SIST ES 203 726 V1.1.1:2022

ETSI STANDARD
Environmental Engineering (EE);
Progressive migration of Information and
Communication Technology (ICT) site to
400 VDC sources and distribution

2 ETSI ES 203 726 V1.1.1 (2022-08)

Reference
DES/EE-0260
Keywords
energy efficiency, power supply, site engineering

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ETSI
3 ETSI ES 203 726 V1.1.1 (2022-08)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Executive summary . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 9
3 Definition of terms, symbols and abbreviations . 11
3.1 Terms . 11
3.2 Symbols . 12
3.3 Abbreviations . 12
4 Present situation of a telecommunication or data centre powering solution and motivation for
migration to up to 400 VDC . 13
5 General evolution cases during migration . 17
5.1 Present situation . 17
5.2 DC/DC converter related considerations . 20
5.3 400/AC migration inverter consideration . 21
5.4 Long distance transport in -48 V/up to 400 VDC/-48 V in centre and multistep migration . 23
5.5 Combined migration cases . 24
5.6 Grid/back-up generator 400 DC switch replacing AC mechanical switch . 25
6 Up to 400 VDC batteries . 26
7 Migration of up to 400 VDC remote power to local up to 400 VDC power system . 26
8 Coupling renewable energy to existing buildings distribution with migration to up to 400 VDC . 27
9 Up to 400 VDC cabling, earthing and bonding in the migration period . 27
10 Electrical safety requirements . 28
11 Electromagnetic compatibility requirements at the input of telecommunication and datacom (ICT)
equipment . 28
12 Impacts on energy efficiency and other key performance indicators (environmental impact, life
cycle assessment) . 29
Annex A (normative): Power supply and interface considerations . 30
Annex B (informative): Information on some papers on up to 400 VDC migration solutions,
advantages and implementation decision and process . 31
Annex C (informative): Details on some saving assessment of migration to up to 400 VDC . 32
C.0 Overview . 32
C.1 Energy efficiency . 32
C.2 Energy cost reduction . 32
C.3 Saving on material, area in ICT room and labour . 33
C.4 Less copper and installation cost, progressive installation by modularity . 33
C.4.0 Overview . 33
ETSI
4 ETSI ES 203 726 V1.1.1 (2022-08)
C.4.1 Reliability and dependability improvement (comparative evaluation using Recommendation
ITU-T L.1202) . 34
C.4.2 Lower life cycle environmental impacts . 34
C.4.3 Solar power input to power distribution . 34
C.4.4 Open innovation . 34
History . 35

ETSI
5 ETSI ES 203 726 V1.1.1 (2022-08)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
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Foreword
This ETSI Standard (ES) has been produced by ETSI Technical Committee Environmental Engineering (EE).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Executive summary
The present document gives explanation, requirements and guidance for increasing the use of up to 400 V Direct
Current (400 VDC) power systems and the distribution to Information and Communication Technology (ICT)
equipment. It includes 400 VDC remote powering up to 400 VDC of distributed ICT equipment, the option of
interconnection of local renewable energy sources and their connection to DC power nanogrids and other users,
extending the resilience capability of the telecommunication network and ICT sites to grid failures and climate change.
ETSI
6 ETSI ES 203 726 V1.1.1 (2022-08)
Introduction
Telecommunication network energy consumption and cost are increasing at a rate of several percentage points per year
as reported in Trends in worldwide ICT electricity consumption from 2007 to 2012 [i.11]. The use of up to 400 V Direct
Current (400 VDC) architecture (as presented in Table 1, Annex B and Annex C) can result in significant savings.
The use of up to 400 VDC solutions result in energy savings with higher efficiency and reduced distribution losses,
reduction in maintenance cost due to higher reliability and lower unavailability, savings in space for power equipment
in Information and Communication Technology (ICT) rooms (each square metre being of high cost) and, finally, more
simplicity in site installation and development.
Different levels of saving and improvement result from a comparison of up to 400 VDC solutions to -48 V solutions
(copper savings) or to Uninterrupted Power Supply (UPS) solutions (reliability, efficiency, easier installation).
400 VDC remote power can be beneficial.
As for the power system, energy savings in addition to those resulting from efficiency improvements depend on the load
in the telecommunication or data centre. Energy efficiency should be evaluated at the system level, including the
general distribution cabling and voltage conversion stages, as well as the internal power circuits inside the load
downstream of the power interface, i.e. conversion architecture in the system (e.g. dual inputs, local back-up, AC/DC
rectifier losses).
Indirect savings of up to 400 VDC solutions relate to lifecycle in the production and recycling phase as there should be
less passage through copper and electronics as well as less battery usage for given output power and system
dependability. Battery capacity and dependability savings are achieved by removing inverter losses if replacing AC
UPS or by reducing -48 V distribution losses.
The present document specifies requirements for a safe migration of an existing site to a unified up to 400 VDC
powering feeding system, power distribution and the power interface of telecommunication/ICT equipment. It includes
requirements relating to the stability, cabling, earthing, as well as bonding and measurement, for the existing site.
The main significant components of up to 400 VDC equipment and additional progressive migration equipment are
presented in Figures 2 and 3. These are schematic diagrams that do not show all the electrical arrangement details. The
architecture under consideration complies with Recommendation ITU-T L.1204 [14] on electrical architecture,
including energy storage defined in ETSI TS 103 553-1 [i.1] or Recommendation ITU-T L.1220 [i.2], technically
equivalent, and with ETSI ES 203 474 [9] or Recommendation ITU-T L.1205 [15], technically equivalent, for DC
coupling of a local RENewable Energy (REN) system on site or with DC nano/micro grid interconnecting sites with
REN sources and storage or ICT equipment requiring remote powering. Smart DC nanogrids are under study as
reported in Intelligent DC Microgrid Living Lab [i.12].
The migration simplifies the use of up to 400 VDC combined with REN and DC nanogrids and should extend resilience
capability of telecommunication networks sites to grid failures and climate change.
The present document was developed jointly by ETSI TC EE and ITU-T Study Group 5. It is published respectively by
ITU and ETSI as Recommendation ITU-T L.1207 [i.3] and ETSI ES 203 726 (the present document), which are
technically-equivalent.
ETSI
7 ETSI ES 203 726 V1.1.1 (2022-08)
1 Scope
The present document defines solutions for progressive migration of Information and Communication Technology
(ICT) sites (telecommunication and data centres) to up to 400 V Direct Current (400 VDC) distribution and direct use of
up to 400 VDC powering ICT equipment from 400 VDC sources. The present document also defines different major
use case options and migration scenarios, such as:
• migration to an up to 400 VDC of telecommunication site power solution;
• migration to an up to 400 VDC of data centre power solution;
• migration with up to 400 VDC power transfer between existing -48 V centralized sources to high power
density -48 V equipment, such as routers;
• integration of up to 400 VDC remote powering;
• combined architecture with up to 400 VDC and AC sources and distributions possibly using hybrid power
interfaces on ICT equipment.
For each of these, the present document describes many possible options and characteristics, such as:
• migration architecture with up to 400 VDC/-48 V conversion to power existing -48 V equipment using
existing -48 V room distribution;
• conditions for tripping overcurrent protection devices without -48 V batteries;
• migration architecture with up to 400 VDC/AC inverter as an alternative to the AC UPS to power existing AC
equipment;
• use of local up to 400 VDC for remote powering of ICT equipment;
• coupling up to 400 VDC systems to a local REN source or to a DC microgrid;
• possibility of conversion between battery and up to 400 VDC distribution, e.g. for long power distribution or
short-circuit current or battery technology (e.g. lithium-ion).
The present document also gives a saving assessment frame reference to define the best migration scenario and its steps
by considering energy, resource, environmental impact and cost savings based on functional aspects such as modularity,
flexibility, reliability, efficiency and distribution losses, as well as maintenance evolution when migrating from -48 V or
Alternating Current (AC) to up to 400 VDC solutions. This also includes consideration of load architecture evolution
dependent on use cases (e.g. telecommunication site, data centres).
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 300 132-1 (V2.1.1) (2019): "Environmental Engineering (EE); Power supply interface at
the input to Information and Communication Technology (ICT) equipment; Part 1: Alternating
Current (AC)".
ETSI
8 ETSI ES 203 726 V1.1.1 (2022-08)
[2] ETSI EN 300 132-2 (V2.6.1) (2019): "Environmental Engineering (EE); Power supply interface at
the input of Information and Communication Technology (ICT) equipment; Part 2: -48 V Direct
Current (DC)".
[3] ETSI EN 300 132-3 (V1.2.1) (2003): "Environmental Engineering (EE); Power supply interface at
the input to telecommunications equipment; Part 3: Operated by rectified current source,
alternating current source or direct current source up to 400 V".
[4] ETSI EN 300 253 (V2.2.1) (2015): "Environmental Engineering (EE); Earthing and bonding of
ICT equipment powered by -48 VDC in telecom and data centres".
[5] ETSI EN 301 605 (V1.1.1) (2013): "Environmental Engineering (EE); Earthing and bonding of
400 VDC data and telecom (ICT) equipment".
[6] ETSI ES 202 336-2 (V1.1.1) (2009): "Environmental Engineering (EE); Monitoring and control
interface for infrastructure equipment (Power, Cooling and environment systems used in
telecommunication networks); Part 2: DC power system control and monitoring information
model".
[7] ETSI ES 203 199 (V1.3.1) (2015): "Environmental Engineering (EE); Methodology for
environmental Life Cycle Assessment (LCA) of Information and Communication Technology
(ICT) goods, networks and services".
[8] ETSI ES 203 408 (V1.1.1): "Environmental Engineering (EE); Colour and marking of DC cable
and connecting devices".
[9] ETSI ES 203 474 (V1.1.1): "Environmental Engineering (EE); Interfacing of renewable energy or
distributed power sources to 400 VDC distribution systems powering Information and
Communication Technology (ICT) equipment".
[10] ETSI TS 103 531 (V1.1.1): "Environmental Engineering (EE); Impact on ICT equipment
architecture of multiple AC, -48 VDC or up to 400 VDC power inputs".
[11] Recommendation ITU-T L.1200 (2012): "Direct current power feeding interface up to 400 V at the
input to telecommunication and ICT equipment".
[12] Recommendation ITU-T L.1202 (2015): "Methodologies for evaluating the performance of an up
to 400 VDC power feeding system and its environmental impact".
[13] Recommendation ITU-T L.1203 (2016): "Colour and marking identification of up to 400 VDC
power distribution for information and communication technology systems".
[14] Recommendation ITU-T L.1204 (2016): "Extended architecture of power feeding systems of up to
400 VDC".
[15] Recommendation ITU-T L.1205 (2016): "Interfacing of renewable energy or distributed power
sources to up to 400 VDC power feeding systems".
[16] Recommendation ITU-T L.1206 (2017): "Impact on ICT equipment architecture of multiple
AC, -48 VDC or up to 400 VDC power inputs".
[17] Recommendation ITU-T L.1320 (2014): "Energy efficiency metrics and measurement for power
and cooling equipment for telecommunications and data centres".
[18] Recommendation ITU-T L.1410 (2014): "Methodology for environmental life cycle assessments
of information and communication technology goods, networks and services".
[19] IEC 60364 (all parts): "Low-voltage electrical installations".
ETSI
9 ETSI ES 203 726 V1.1.1 (2022-08)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TS 103 553-1 (V1.1.1): "Environmental Engineering (EE); Innovative energy storage
technology for stationary use; Part 1: Overview".
[i.2] Recommendation ITU-T L.1220 (2017): "Innovative energy storage technology for stationary use
- Part 1: Overview of energy storage".
[i.3] Recommendation ITU-T L.1207 (2018-05): "Progressive migration of a
telecommunication/information and communication technology site to 400 VDC sources and
distribution".
[i.4] ETSI EN 302 099 (V2.1.1) (2014): "Environmental Engineering (EE); Powering of equipment in
access network".
[i.5] Recommendation ITU-T K.48 (2017): "EMC requirements for telecommunication equipment -
Product family Recommendation".
[i.6] IEC 60950-1: "Information technology equipment - Safety - Part 1: General requirements".
[i.7] IEC 62368-1: "Audio/video, information and communication technology equipment - Part 1:
Safety requirements".
[i.8] ETSI EN 300 132-3-1 (V2.1.1) (2012): "Environmental Engineering (EE); Power supply interface
at the input to telecommunications and datacom (ICT) equipment; Part 3: Operated by rectified
current source, alternating current source or direct current source up to 400 V; Sub-part 1: Direct
current source up to 400 V".
[i.9] ETSI EN 300 386 (V2.1.1) (2016): "Telecommunication network equipment; ElectroMagnetic
Compatibility (EMC) requirements; Harmonised Standard covering the essential requirements of
the Directive 2014/30/EU".
[i.10] ETSI TR 100 283 (V2.2.1) (2007): "Environmental Engineering (EE); Transient voltages at
Interface "A" on telecommunications direct current (dc) power distributions".
[i.11] Van Heddeghem W., Lambert S., Lannoo B., Colle D., Pickavet M., Demeester P. (2014): "Trends
in worldwide ICT electricity consumption from 2007 to 2012". Computer Communications, 50,
64-76.
NOTE: Available at https://doi.org/10.1016/j.comcom.2014.02.008.
[i.12] Aalborg University: "Intelligent DC Microgrid Living Lab".
[i.13] Tsumura T, Takeda T, Hirose K (2008): "A tool for calculating reliability of power supply for
th
information and communication technology systems". In Intelec 2008 - IEEE 30 International
Telecommunications Energy Conference, 21.3, 6 pp., San Diego.
[i.14] Marquet D, Tanaka T, Murai K, Tanaka T, Babasaki T (2013): "DC power wide spread in
Telecom/Datacenter and in home/office with renewable energy and energy autonomy". In Intelec
th
2013 - IEEE 35 International Telecommunications Energy Conference, Smart Power and
Efficiency, pp. 499-504, Hamburg.
[i.15] Caltech Berkeley 2017 Vossos V, Johnson K, Kloss M, Khattar M, Gerber D, Brown R: "Review
of DC power distribution in buildings: A technology and market assessment" pp.71.
ETSI
10 ETSI ES 203 726 V1.1.1 (2022-08)
[i.16] Schneider WP 118 Rasmussen N (undated): "High-efficiency AC power distribution for data
centers". White Paper 128. Rueil-Malmaison: Schneider Electric. 19 pp.
[i.17] CE+T Intelec 2016 Frebel F. (eFFiciency research), Bleus P. Bomboir O. (CE+T Power, sa):
"Transformer-less 2 kW non isolated 400 VDC/230 VAC single stage micro inverter". In Intelec
2016 - IEEE International Telecommunications Energy Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/7749105.
[i.18] CATR Intelec 2012 Qi S, Hou F, Jing H: "Study and application on high voltage DC power
th
feeding system for telecommunications in China". In Intelec 2012 - IEEE 34 International
Telecommunications Energy Conference, pp. 9.1. 5, Scottsdale.
NOTE: Available at https://ieeexplore.ieee.org/xpl/conhome/6362321/proceeding.
[i.19] CAICT Intelec 2017 Qi S, Sun W, Wu Y: "Comparative analysis on different architectures of
power supply system for data center and telecom center". In Intelec 2017 - IEEE International
Telecommunications Energy Conference, pp. 26-29, Queensland.
[i.20] DCC+G Fraunhofer 2014 Wunde B: "380 VDC in commercial buildings and offices". Presentation
at Vicor Seminar 2014. 71 slides.
NOTE: Available at http://dcgrid.tue.nl/files/2014-02-11%20-%20Webinar%20Vicor.pdf.
[i.21] Fraunhofer Safety Intelec 2017 Kaiser J et al.: "Safety consideration for the operation of bipolar
DC grids". In Intelec 2017 - IEEE International Telecommunications Energy Conference,
pp. 327-334, Queensland.
[i.22] Fraunhofer Droop Intelec 2017 Wunder B et al.: "Droop controlled cognitive power electronics for
DC microgrids". In Intelec 2017 - IEEE International Telecommunications Energy Conference,
pp. 335-342, Queensland.
[i.23] Void.
[i.24] Fujitsu-NTT-Appliance coupler-Intelec 2017 Kiryu K, Tanaka T, Sato K, Seki K, Hirose K:
"Development of appliance coupler for LVDC in Information Communication Technology (ICT)
equipment with having a protection of inrush current and arc". In Intelec 2017 - IEEE International
Telecommunications Energy Conference, pp. 343-346, Queensland.
[i.25] level3-Eltek Intelec 2016 Ambriz A. (Level 3 Communications), Kania M. (Eltek): "A service
provider's decision to move from 48V to 380V powering: The problem statement, technical
assessment, financial analysis and practical implementation plan". In Intelec 2016 - IEEE
International Telecommunications Energy Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/7749117.
[i.26] NTT Intelec 1999 Yamashita T, Muroyama S, Furubo S, Ohtsu S: "270 VDC System - A highly
efficient and reliable power supply system for both telecom and datacom systems". In Intelec 1999
st
- IEEE 21 International Telecommunication Energy Conference, PI 1-3. 5 pp., Copenhagen.
[i.27] NTT-f Intelec 2016 Hiroya Yajima, Kenichi Usui, Toshiyuki Hayashi (R&D and datacenter,
NTT Facilities Japan): "Energy-saving effects of super computers by using on-site solar power and
direct HVDC feeding systems". In Intelec 2016 - IEEE International Telecommunications Energy
Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/8214133.
[i.28] NTT-f Intelec 2011 Hirose K, Tanaka T, Babasaki T, Person S, Foucault O, Sonnenberg BJ,
Szpek M: "Grounding concept considerations and recommendations for 400 VDC distribution
rd
system". In Intelec 2011 - IEEE 33 International Telecommunications Energy Conference, 8 pp.,
Amsterdam.
[i.29] NTT Intelec 2012 Tanaka T, Hirose K, Marquet D, Sonnenberg BJ, Szpek M: "Analysis of wiring
design for 380-VDC power distribution system at telecommunication sites". In Intelec 2012 -
th
IEEE 34 International Telecommunications Energy Conference, 15.2. 5 pp., Scottsdale.
ETSI
11 ETSI ES 203 726 V1.1.1 (2022-08)
[i.30] OCP Orange: "400 VDC power feeding architecture", OCP 2017.
NOTE: Available at http://www.opencompute.org/wiki/Telcos.
[i.31] OCP Murata (2017): "Open compute power solutions". 4 pp.
NOTE: Available at https://www.avnet.com/wps/wcm/connect/onesite/584cd2d9-7c90-4465-83bc-
15501e9bc430/Murata-ocp-EN-Brochure.pdf?MOD=AJPERES&CVID=lMbA3cq&CVID=lMbA3cq.
[i.32] Orange Intelec 2011 Marquet D, Foucault O, Acheen J, Turc JF, Szpek M, Brunarie J:
"Pre roll-out field test of 400 VDC power supply: The new alliance of Edison and Tesla towards
rd
energy efficiency". In Intelec 2011 - IEEE 33 International Telecommunications Energy
Conference, 8 pp., Amsterdam.
[i.33] Orange Intelec 2016 Foucault O, Marquet D, le Masson S: "400 VDC Remote Powering as an
alternative for power needs in new fixed and radio access networks". In Intelec 2016 - IEEE
International Telecommunications Energy Conference, TS19.3, 9 pp, Austin.
[i.34] Orange Intelec 2017 Marquet D, Foucault O, Pichon JM,, Hirose K, Bianco C, Hockley R:
"Telecom operators to accelerate the migration towards 400 volt direct current - Efficient
powering for telecom/ICT equipment and coupling sites to smart energy microgrids". In Intelec
2017 - IEEE International Telecommunications Energy Conference, pp. 196-203, Queensland.
[i.35] Orange Intelec 1999 Marquet D, San Miguel F, Gabillet JP: "New power supply optimised for new
st
telecom networks and services". In Intelec 1999 - IEEE 21 International Telecommunication
Energy Conference, 25-1. 8 pp., Copenhagen.
[i.36] Orange Intelec 2005 Marquet D, Kervarrec G, Foucault O: "New flexible powering architecture
th
for integrated service operators". In Intelec 2005 - IEEE 27 International Telecommunications
Conference, pp. 575-580, Berlin.
[i.37] Schneider WP 151 Rasmussen N (undated): "Review of four studies comparing efficiency of AC
and DC distribution for data centers". White Paper 151, Rueil-Malmaison: Schneider Electric,
12 pp.
[i.38] Schneider WP 127 Rasmussen N, Spitaels J (undated): "A quantitative comparison of high
efficiency AC vs. DC power distribution for data centers". White Paper 127, Rev 2.
Rueil-Malmaison: Schneider Electric, 23 pp.
[i.39] Telstra Intelec 2017 Yong M, Bettle D: "Deploying HVDC in existing network exchanges:
Practical and financial benefits for telecommunications carriers". In Intelec 2017 - IEEE
International Telecommunications Energy Conference, pp. 204-207, Queensland.
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady-state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
NOTE: Available in ETSI EN 300 132-2 [2].
advanced battery: battery of more performant technology, e.g. lithium battery compared to mainly used legacy battery
technology used in telecommunication and data centres, i.e. Valve-Regulated Lead-Acid (VRLA)
DC/DC converter: power electronic system that transfers energy from one DC voltage (level) to another DC voltage
(level)
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
ETSI
12 ETSI ES 203 726 V1.1.1 (2022-08)
interface "A": terminals, at which the power supply is connected to the system block
NOTE: Available in ETSI EN 300 132-2 [2].
interface A1: interface, physical point, at which AC power supply is connected in order to operate the
telecommunications and datacom (ICT) equipment
interface A3: interface, physical point, at which power supply is connected in order to operate the telecommunications
and datacom (ICT) equipment
NOTE: Available in ETSI EN 300 132-1 [1].
load, load equipment: power consuming equipment that is part of a system block
normal operation: operation in typical environmental and powering conditions for telecommunications and datacom
(ICT) equipment, power supply, power distribution and battery at normal service
normal service: service mode where telecommunications and datacom (ICT) equipment operates within its
specification which includes a defined restart time after malfunction or full interruption
NOTE: Available in ETSI EN 300 132-2 [2].
normal service voltage range: range of the steady-state voltages over which the equipment will maintain normal
service
NOTE: Available in ETSI EN 300 132-2 [2].
power supply: power source to which telecommunication and datacom (ICT) equipment is intended to be connected
NOTE: A power source can be at building level, room level, rack level or a unit inside ICT equipment that feeds
power at a defined interface where it is required.
system block: functional group of telecommunications and datacom (ICT) equipment depending on its connection to
the same power supply for its operation and performance
telecommunication centre: any location where telecommunications and datacom (ICT) equipment is installed and is the
sole responsibility of the operator
NOTE: Available in ETSI EN 300 132-3-1 [i.8].
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
4G fourth Generation
5G fifth Generation
AC Alternating Current
AC ICT AC Information & Communication Technology
AC UPS AC Uninterruptable Power Supply
ATS Automatic Transfer Switch
CAPEX Capital Expenditure
DC Direct Current
DCC DC Components
DCC+G DC Components and Grids
DoD Depth of Discharge
EMC ElectroMagnetic Compatibility
FTTx Fibre To The x
HRMG High Resistance Middle point Grounding
HVDC High-Voltage Direct Current
ETSI
13 ETSI ES 203 726 V1.1.1 (2022-08)
ICT Information and Communication Technology
IEC International Electrotechnical Commission
IT Information Technology
ITU-T International Telecommunications Union - Telecommunication
KPI Key Performance Indicator
LCA Life Cycle Assessment
MTBF Mean Time Between Failures
MW MegaWatt
NTT Nippon Telegraph and Telecom
O&M Operation and Maintenance
OCP Open Closed Principle
OPEX OPeration EXpenditure
PDU Power Distribution Unit
PFC Power Factor Correction
POL Point Of Load
PSU Power Supply Unit
PV Photovoltaic
REN RENewable Energy
TC Technical Committee
TCO Total Cost Ownership
UPS Uninterruptible Power Supply
USA United States of America
VAC Volts Alternating Current
VDC Volts Direct Current
VRLA Valve-Regulated Lead-Acid
WP White Paper
4 Present situation of a telecommunication or data
centre powering solution and motivation for migration
to up to 400 VDC
Figure 1 presents a mixed power system architecture with the various interfaces A, A3 and A3ac, and interconnection to
an AC board and back-up engine generator, as it will appear during the migration period in most of legacy
telecommunication operators' buildings.
Figure 1 shows the drawbacks of existing powering -48 V and AC Uninterruptible Power Supply (UPS) solutions, and
where improvements should progressively be made when building new generation rooms or upgrading existing rooms
with up to 400 VDC in telecommunication/ICT buildings.
The ICT power supply interfaces considered in the present document shall be ETSI EN 300 132-2 [2] for -48 V, ETSI
EN 300 132-1 [1] for AC and Recommendation ITU-T L.1200 [11] or ETSI EN 300 132-3 [3] for up to 400 VDC.
The motivations for migration to up to 400 VDC solutions are to reduce the drawbacks of -48 V and AC solutions
shown in Figure 1 by aiming for the ultimate target defined in the architecture shown in Figure 2, which offers the
following advantages:
• Power architecture unification by progressively using a single up to 400 VDC power interface on loads.
Different migration steps are possible, from less to more benefit, as described in clause 7.
• Simplification of architecture and maintenance (e.g. with more modular solutions) by using the up to 400 VDC
architecture defined in Recommendation ITU-T L.1204 [14].
• Energy efficiency and energy cost reduction with dynamic saving modes as in 48 V that can be assessed by
using a comparative evaluation specified in Recommendation ITU-T L.1202 [12]. More than 3 % can be saved
on energy consumption and more than 80 % on material and labour cost, as assessed in Annex C.
• Lower copper and installation costs, progressive installation by modularity. Copper use could be decreased by
a factor of 10, resulting in a simpler and faster installation, easier upgrades and the flexibility to adapt to new
product developments. Integration of REN could be also simplified. Assessment is described in Annex C.
ETSI
14 ETSI ES 203 726 V1.1.1 (2022-08)
• Reliability and dependability improvement. The comparative evaluation of up to 400 VDC versus -48 V and
AC interfaces shall be established by the methods specified in Recommendation ITU-T L.1202 [12].
NOTE 1: Compared to UPS installation at comparable prices, unavailability can be improved by a factor of 10, as
reported in "A tool for calculating reliability of power supply for information and communication
technology systems" [i.13] and "DC power wide spread in Telecom/Datacenter and in home/office with
renewable energy and energy autonomy" [i.14].
• Lower life cycle environmental impacts (less copper, less complex equipment, longer lifetime, less number
and capacity of battery use and more modularity, etc.). This shall be evaluated by the Life Cycle Assessment
(LCA) environmental impact in compliance with ETSI ES 203 199 [7] or Recommendation ITU-T
L.1410 [18], technical equivalent, assessment methods.
The up to 400 VDC loads architecture can have an impact on specific aspects not fully covered in the present document
such as:
• more on site power generation in terms of solar and wind with local power storage to try to minimize power
drawn from the grid when grid supply is used only as a backup source;
• excess renewable power generation sold back to the grid and utility supply selection in attempts to minimize
utility cost;
• a possible future requirement for centre power autonomy that might make the most of the supply distribution
system that is dormant most of the time.

Figure 1: Legacy power architecture in common telecommunication or data centres at the start of
migration to up to 400 VDC at level of power station, distribution and load equipment
NOTE 2: Text blocks highlighted in green indicate improvements and those in red drawbacks of existing solutions.
ETSI
15 ETSI ES 203 726 V1.1.1 (2022-08)

Figure 2: Expanded ultimate target migration to up to 400 VDC principle with all options
NOTE 3: The indicated power interface refers to standard up to 400 VDC Recommendation ITU-T L.1200 [11] or
ETSI EN 300 132-3 [3], 48 V ETSI EN 300 132-2 [2], AC ETSI EN 300 132-1 [1], Remote Powering
ETSI EN 302 099 [i.4].
As far as possible, a common approach is applied for telecommunication and data centres for local power distribution,
but very high power in a data centre (multi-megawatt) might introduce some differences as presented in Annex B and
clause 5.5.
The potential savings are at the levels of:
• power plant;
• distribution;
• loads.
The connection of a solar power system to up to 400 VDC local distribution presented in Figure 1 is not described in
detail in the present document; it shall comply with ETSI ES 203 474 [9] or the technically equivalent Recommendation
ITU-T L.1205 [15].
If data centres are looking to become more autonomous from the utility, this can also mean more emphasis on local site
power solutions and the impact on electricity supply network has to be considered.
Depending on the battery usage approach, there can be an impact on the architecture depending on the strictness of the
regulation for charge control, as discussed in clause 6.
There can be single or bidirectional flow on the DC nanogrid as presented in Intelligent DC Microgrid Living Lab
[i.12].
ETSI
16 ETSI ES 203 726 V1.1.1 (2022-08)
In general, the migration steps towards up to 400 VDC solutions would be as shown in Figure 3, and described as
follows:
• install a centralized up to 400 VDC power station, and up to 400 VDC distribution to ICT rooms on given sites
or other user equipment (e.g. cooling);
• add up to 400 VDC/-48 or 400 VDC/AC front converter in a transition period;
• change existing -48 V or AC equipment Power Supply Unit (PSU) to up to 400 VDC PSU using dual input
PSU ETSI TS 103 531 [10] or the technical equivalent Recommendation ITU-T L.1206 [16], one for -48 V or
AC, one for up to 400 VDC or universal AC and up to 400 VDC input PSU.

Figure 3: Possible transition paths to target inside a telecommunication or data centre
NOTE 4: The indicated power interface refers to standard up to 400 VDC Recommendation ITU-T L.1200 [11] or
ETSI EN 300 132-3 [3], -48 V ETSI EN 300 132-2 [2], AC ETSI EN 300 132-1 [1], Remote Powering
ETSI EN 302 099 [i.4].
Table 1 gives an overview of the potential improvements of migration case towards the up to 400 VDC target and
additional options, such as RENewable Energy (REN). Some detailed assessment hypotheses are given in Annex C. The
potential savings listed in Table 1 assume a sufficient market of up to 400 VDC systems for a realistic comparison (less
than a factor of 10 in volume of installed equipment).
NOTE 5: The comparison is between legacy -48 V or AC UPS to pure up to 400 VDC target. The transition period
with DC/DC converters (400/-48) or a DC/AC inverter (400/AC) is not assessed, as there are many
different configurations and transition equipment that can be reused o
...

SLOVENSKI STANDARD
01-oktober-2022
Okoljski inženiring (EE) - Naraščajoče prehajanje informacijske in komunikacijske
tehnologije (IKT) na vire 400 VDC in distribucijo
Environmental Engineering (EE) - Progressive migration of Information and
Communication Technology (ICT) site to 400 VDC sources and distribution
Ta slovenski standard je istoveten z: ETSI ES 203 726 V1.1.1 (2022-08)
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
35.020 Informacijska tehnika in Information technology (IT) in
tehnologija na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

ETSI STANDARD
Environmental Engineering (EE);
Progressive migration of Information and
Communication Technology (ICT) site to
400 VDC sources and distribution

2 ETSI ES 203 726 V1.1.1 (2022-08)

Reference
DES/EE-0260
Keywords
energy efficiency, power supply, site engineering

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ETSI
3 ETSI ES 203 726 V1.1.1 (2022-08)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Executive summary . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 9
3 Definition of terms, symbols and abbreviations . 11
3.1 Terms . 11
3.2 Symbols . 12
3.3 Abbreviations . 12
4 Present situation of a telecommunication or data centre powering solution and motivation for
migration to up to 400 VDC . 13
5 General evolution cases during migration . 17
5.1 Present situation . 17
5.2 DC/DC converter related considerations . 20
5.3 400/AC migration inverter consideration . 21
5.4 Long distance transport in -48 V/up to 400 VDC/-48 V in centre and multistep migration . 23
5.5 Combined migration cases . 24
5.6 Grid/back-up generator 400 DC switch replacing AC mechanical switch . 25
6 Up to 400 VDC batteries . 26
7 Migration of up to 400 VDC remote power to local up to 400 VDC power system . 26
8 Coupling renewable energy to existing buildings distribution with migration to up to 400 VDC . 27
9 Up to 400 VDC cabling, earthing and bonding in the migration period . 27
10 Electrical safety requirements . 28
11 Electromagnetic compatibility requirements at the input of telecommunication and datacom (ICT)
equipment . 28
12 Impacts on energy efficiency and other key performance indicators (environmental impact, life
cycle assessment) . 29
Annex A (normative): Power supply and interface considerations . 30
Annex B (informative): Information on some papers on up to 400 VDC migration solutions,
advantages and implementation decision and process . 31
Annex C (informative): Details on some saving assessment of migration to up to 400 VDC . 32
C.0 Overview . 32
C.1 Energy efficiency . 32
C.2 Energy cost reduction . 32
C.3 Saving on material, area in ICT room and labour . 33
C.4 Less copper and installation cost, progressive installation by modularity . 33
C.4.0 Overview . 33
ETSI
4 ETSI ES 203 726 V1.1.1 (2022-08)
C.4.1 Reliability and dependability improvement (comparative evaluation using Recommendation
ITU-T L.1202) . 34
C.4.2 Lower life cycle environmental impacts . 34
C.4.3 Solar power input to power distribution . 34
C.4.4 Open innovation . 34
History . 35

ETSI
5 ETSI ES 203 726 V1.1.1 (2022-08)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
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ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
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DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
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oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This ETSI Standard (ES) has been produced by ETSI Technical Committee Environmental Engineering (EE).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Executive summary
The present document gives explanation, requirements and guidance for increasing the use of up to 400 V Direct
Current (400 VDC) power systems and the distribution to Information and Communication Technology (ICT)
equipment. It includes 400 VDC remote powering up to 400 VDC of distributed ICT equipment, the option of
interconnection of local renewable energy sources and their connection to DC power nanogrids and other users,
extending the resilience capability of the telecommunication network and ICT sites to grid failures and climate change.
ETSI
6 ETSI ES 203 726 V1.1.1 (2022-08)
Introduction
Telecommunication network energy consumption and cost are increasing at a rate of several percentage points per year
as reported in Trends in worldwide ICT electricity consumption from 2007 to 2012 [i.11]. The use of up to 400 V Direct
Current (400 VDC) architecture (as presented in Table 1, Annex B and Annex C) can result in significant savings.
The use of up to 400 VDC solutions result in energy savings with higher efficiency and reduced distribution losses,
reduction in maintenance cost due to higher reliability and lower unavailability, savings in space for power equipment
in Information and Communication Technology (ICT) rooms (each square metre being of high cost) and, finally, more
simplicity in site installation and development.
Different levels of saving and improvement result from a comparison of up to 400 VDC solutions to -48 V solutions
(copper savings) or to Uninterrupted Power Supply (UPS) solutions (reliability, efficiency, easier installation).
400 VDC remote power can be beneficial.
As for the power system, energy savings in addition to those resulting from efficiency improvements depend on the load
in the telecommunication or data centre. Energy efficiency should be evaluated at the system level, including the
general distribution cabling and voltage conversion stages, as well as the internal power circuits inside the load
downstream of the power interface, i.e. conversion architecture in the system (e.g. dual inputs, local back-up, AC/DC
rectifier losses).
Indirect savings of up to 400 VDC solutions relate to lifecycle in the production and recycling phase as there should be
less passage through copper and electronics as well as less battery usage for given output power and system
dependability. Battery capacity and dependability savings are achieved by removing inverter losses if replacing AC
UPS or by reducing -48 V distribution losses.
The present document specifies requirements for a safe migration of an existing site to a unified up to 400 VDC
powering feeding system, power distribution and the power interface of telecommunication/ICT equipment. It includes
requirements relating to the stability, cabling, earthing, as well as bonding and measurement, for the existing site.
The main significant components of up to 400 VDC equipment and additional progressive migration equipment are
presented in Figures 2 and 3. These are schematic diagrams that do not show all the electrical arrangement details. The
architecture under consideration complies with Recommendation ITU-T L.1204 [14] on electrical architecture,
including energy storage defined in ETSI TS 103 553-1 [i.1] or Recommendation ITU-T L.1220 [i.2], technically
equivalent, and with ETSI ES 203 474 [9] or Recommendation ITU-T L.1205 [15], technically equivalent, for DC
coupling of a local RENewable Energy (REN) system on site or with DC nano/micro grid interconnecting sites with
REN sources and storage or ICT equipment requiring remote powering. Smart DC nanogrids are under study as
reported in Intelligent DC Microgrid Living Lab [i.12].
The migration simplifies the use of up to 400 VDC combined with REN and DC nanogrids and should extend resilience
capability of telecommunication networks sites to grid failures and climate change.
The present document was developed jointly by ETSI TC EE and ITU-T Study Group 5. It is published respectively by
ITU and ETSI as Recommendation ITU-T L.1207 [i.3] and ETSI ES 203 726 (the present document), which are
technically-equivalent.
ETSI
7 ETSI ES 203 726 V1.1.1 (2022-08)
1 Scope
The present document defines solutions for progressive migration of Information and Communication Technology
(ICT) sites (telecommunication and data centres) to up to 400 V Direct Current (400 VDC) distribution and direct use of
up to 400 VDC powering ICT equipment from 400 VDC sources. The present document also defines different major
use case options and migration scenarios, such as:
• migration to an up to 400 VDC of telecommunication site power solution;
• migration to an up to 400 VDC of data centre power solution;
• migration with up to 400 VDC power transfer between existing -48 V centralized sources to high power
density -48 V equipment, such as routers;
• integration of up to 400 VDC remote powering;
• combined architecture with up to 400 VDC and AC sources and distributions possibly using hybrid power
interfaces on ICT equipment.
For each of these, the present document describes many possible options and characteristics, such as:
• migration architecture with up to 400 VDC/-48 V conversion to power existing -48 V equipment using
existing -48 V room distribution;
• conditions for tripping overcurrent protection devices without -48 V batteries;
• migration architecture with up to 400 VDC/AC inverter as an alternative to the AC UPS to power existing AC
equipment;
• use of local up to 400 VDC for remote powering of ICT equipment;
• coupling up to 400 VDC systems to a local REN source or to a DC microgrid;
• possibility of conversion between battery and up to 400 VDC distribution, e.g. for long power distribution or
short-circuit current or battery technology (e.g. lithium-ion).
The present document also gives a saving assessment frame reference to define the best migration scenario and its steps
by considering energy, resource, environmental impact and cost savings based on functional aspects such as modularity,
flexibility, reliability, efficiency and distribution losses, as well as maintenance evolution when migrating from -48 V or
Alternating Current (AC) to up to 400 VDC solutions. This also includes consideration of load architecture evolution
dependent on use cases (e.g. telecommunication site, data centres).
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 300 132-1 (V2.1.1) (2019): "Environmental Engineering (EE); Power supply interface at
the input to Information and Communication Technology (ICT) equipment; Part 1: Alternating
Current (AC)".
ETSI
8 ETSI ES 203 726 V1.1.1 (2022-08)
[2] ETSI EN 300 132-2 (V2.6.1) (2019): "Environmental Engineering (EE); Power supply interface at
the input of Information and Communication Technology (ICT) equipment; Part 2: -48 V Direct
Current (DC)".
[3] ETSI EN 300 132-3 (V1.2.1) (2003): "Environmental Engineering (EE); Power supply interface at
the input to telecommunications equipment; Part 3: Operated by rectified current source,
alternating current source or direct current source up to 400 V".
[4] ETSI EN 300 253 (V2.2.1) (2015): "Environmental Engineering (EE); Earthing and bonding of
ICT equipment powered by -48 VDC in telecom and data centres".
[5] ETSI EN 301 605 (V1.1.1) (2013): "Environmental Engineering (EE); Earthing and bonding of
400 VDC data and telecom (ICT) equipment".
[6] ETSI ES 202 336-2 (V1.1.1) (2009): "Environmental Engineering (EE); Monitoring and control
interface for infrastructure equipment (Power, Cooling and environment systems used in
telecommunication networks); Part 2: DC power system control and monitoring information
model".
[7] ETSI ES 203 199 (V1.3.1) (2015): "Environmental Engineering (EE); Methodology for
environmental Life Cycle Assessment (LCA) of Information and Communication Technology
(ICT) goods, networks and services".
[8] ETSI ES 203 408 (V1.1.1): "Environmental Engineering (EE); Colour and marking of DC cable
and connecting devices".
[9] ETSI ES 203 474 (V1.1.1): "Environmental Engineering (EE); Interfacing of renewable energy or
distributed power sources to 400 VDC distribution systems powering Information and
Communication Technology (ICT) equipment".
[10] ETSI TS 103 531 (V1.1.1): "Environmental Engineering (EE); Impact on ICT equipment
architecture of multiple AC, -48 VDC or up to 400 VDC power inputs".
[11] Recommendation ITU-T L.1200 (2012): "Direct current power feeding interface up to 400 V at the
input to telecommunication and ICT equipment".
[12] Recommendation ITU-T L.1202 (2015): "Methodologies for evaluating the performance of an up
to 400 VDC power feeding system and its environmental impact".
[13] Recommendation ITU-T L.1203 (2016): "Colour and marking identification of up to 400 VDC
power distribution for information and communication technology systems".
[14] Recommendation ITU-T L.1204 (2016): "Extended architecture of power feeding systems of up to
400 VDC".
[15] Recommendation ITU-T L.1205 (2016): "Interfacing of renewable energy or distributed power
sources to up to 400 VDC power feeding systems".
[16] Recommendation ITU-T L.1206 (2017): "Impact on ICT equipment architecture of multiple
AC, -48 VDC or up to 400 VDC power inputs".
[17] Recommendation ITU-T L.1320 (2014): "Energy efficiency metrics and measurement for power
and cooling equipment for telecommunications and data centres".
[18] Recommendation ITU-T L.1410 (2014): "Methodology for environmental life cycle assessments
of information and communication technology goods, networks and services".
[19] IEC 60364 (all parts): "Low-voltage electrical installations".
ETSI
9 ETSI ES 203 726 V1.1.1 (2022-08)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TS 103 553-1 (V1.1.1): "Environmental Engineering (EE); Innovative energy storage
technology for stationary use; Part 1: Overview".
[i.2] Recommendation ITU-T L.1220 (2017): "Innovative energy storage technology for stationary use
- Part 1: Overview of energy storage".
[i.3] Recommendation ITU-T L.1207 (2018-05): "Progressive migration of a
telecommunication/information and communication technology site to 400 VDC sources and
distribution".
[i.4] ETSI EN 302 099 (V2.1.1) (2014): "Environmental Engineering (EE); Powering of equipment in
access network".
[i.5] Recommendation ITU-T K.48 (2017): "EMC requirements for telecommunication equipment -
Product family Recommendation".
[i.6] IEC 60950-1: "Information technology equipment - Safety - Part 1: General requirements".
[i.7] IEC 62368-1: "Audio/video, information and communication technology equipment - Part 1:
Safety requirements".
[i.8] ETSI EN 300 132-3-1 (V2.1.1) (2012): "Environmental Engineering (EE); Power supply interface
at the input to telecommunications and datacom (ICT) equipment; Part 3: Operated by rectified
current source, alternating current source or direct current source up to 400 V; Sub-part 1: Direct
current source up to 400 V".
[i.9] ETSI EN 300 386 (V2.1.1) (2016): "Telecommunication network equipment; ElectroMagnetic
Compatibility (EMC) requirements; Harmonised Standard covering the essential requirements of
the Directive 2014/30/EU".
[i.10] ETSI TR 100 283 (V2.2.1) (2007): "Environmental Engineering (EE); Transient voltages at
Interface "A" on telecommunications direct current (dc) power distributions".
[i.11] Van Heddeghem W., Lambert S., Lannoo B., Colle D., Pickavet M., Demeester P. (2014): "Trends
in worldwide ICT electricity consumption from 2007 to 2012". Computer Communications, 50,
64-76.
NOTE: Available at https://doi.org/10.1016/j.comcom.2014.02.008.
[i.12] Aalborg University: "Intelligent DC Microgrid Living Lab".
[i.13] Tsumura T, Takeda T, Hirose K (2008): "A tool for calculating reliability of power supply for
th
information and communication technology systems". In Intelec 2008 - IEEE 30 International
Telecommunications Energy Conference, 21.3, 6 pp., San Diego.
[i.14] Marquet D, Tanaka T, Murai K, Tanaka T, Babasaki T (2013): "DC power wide spread in
Telecom/Datacenter and in home/office with renewable energy and energy autonomy". In Intelec
th
2013 - IEEE 35 International Telecommunications Energy Conference, Smart Power and
Efficiency, pp. 499-504, Hamburg.
[i.15] Caltech Berkeley 2017 Vossos V, Johnson K, Kloss M, Khattar M, Gerber D, Brown R: "Review
of DC power distribution in buildings: A technology and market assessment" pp.71.
ETSI
10 ETSI ES 203 726 V1.1.1 (2022-08)
[i.16] Schneider WP 118 Rasmussen N (undated): "High-efficiency AC power distribution for data
centers". White Paper 128. Rueil-Malmaison: Schneider Electric. 19 pp.
[i.17] CE+T Intelec 2016 Frebel F. (eFFiciency research), Bleus P. Bomboir O. (CE+T Power, sa):
"Transformer-less 2 kW non isolated 400 VDC/230 VAC single stage micro inverter". In Intelec
2016 - IEEE International Telecommunications Energy Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/7749105.
[i.18] CATR Intelec 2012 Qi S, Hou F, Jing H: "Study and application on high voltage DC power
th
feeding system for telecommunications in China". In Intelec 2012 - IEEE 34 International
Telecommunications Energy Conference, pp. 9.1. 5, Scottsdale.
NOTE: Available at https://ieeexplore.ieee.org/xpl/conhome/6362321/proceeding.
[i.19] CAICT Intelec 2017 Qi S, Sun W, Wu Y: "Comparative analysis on different architectures of
power supply system for data center and telecom center". In Intelec 2017 - IEEE International
Telecommunications Energy Conference, pp. 26-29, Queensland.
[i.20] DCC+G Fraunhofer 2014 Wunde B: "380 VDC in commercial buildings and offices". Presentation
at Vicor Seminar 2014. 71 slides.
NOTE: Available at http://dcgrid.tue.nl/files/2014-02-11%20-%20Webinar%20Vicor.pdf.
[i.21] Fraunhofer Safety Intelec 2017 Kaiser J et al.: "Safety consideration for the operation of bipolar
DC grids". In Intelec 2017 - IEEE International Telecommunications Energy Conference,
pp. 327-334, Queensland.
[i.22] Fraunhofer Droop Intelec 2017 Wunder B et al.: "Droop controlled cognitive power electronics for
DC microgrids". In Intelec 2017 - IEEE International Telecommunications Energy Conference,
pp. 335-342, Queensland.
[i.23] Void.
[i.24] Fujitsu-NTT-Appliance coupler-Intelec 2017 Kiryu K, Tanaka T, Sato K, Seki K, Hirose K:
"Development of appliance coupler for LVDC in Information Communication Technology (ICT)
equipment with having a protection of inrush current and arc". In Intelec 2017 - IEEE International
Telecommunications Energy Conference, pp. 343-346, Queensland.
[i.25] level3-Eltek Intelec 2016 Ambriz A. (Level 3 Communications), Kania M. (Eltek): "A service
provider's decision to move from 48V to 380V powering: The problem statement, technical
assessment, financial analysis and practical implementation plan". In Intelec 2016 - IEEE
International Telecommunications Energy Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/7749117.
[i.26] NTT Intelec 1999 Yamashita T, Muroyama S, Furubo S, Ohtsu S: "270 VDC System - A highly
efficient and reliable power supply system for both telecom and datacom systems". In Intelec 1999
st
- IEEE 21 International Telecommunication Energy Conference, PI 1-3. 5 pp., Copenhagen.
[i.27] NTT-f Intelec 2016 Hiroya Yajima, Kenichi Usui, Toshiyuki Hayashi (R&D and datacenter,
NTT Facilities Japan): "Energy-saving effects of super computers by using on-site solar power and
direct HVDC feeding systems". In Intelec 2016 - IEEE International Telecommunications Energy
Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/8214133.
[i.28] NTT-f Intelec 2011 Hirose K, Tanaka T, Babasaki T, Person S, Foucault O, Sonnenberg BJ,
Szpek M: "Grounding concept considerations and recommendations for 400 VDC distribution
rd
system". In Intelec 2011 - IEEE 33 International Telecommunications Energy Conference, 8 pp.,
Amsterdam.
[i.29] NTT Intelec 2012 Tanaka T, Hirose K, Marquet D, Sonnenberg BJ, Szpek M: "Analysis of wiring
design for 380-VDC power distribution system at telecommunication sites". In Intelec 2012 -
th
IEEE 34 International Telecommunications Energy Conference, 15.2. 5 pp., Scottsdale.
ETSI
11 ETSI ES 203 726 V1.1.1 (2022-08)
[i.30] OCP Orange: "400 VDC power feeding architecture", OCP 2017.
NOTE: Available at http://www.opencompute.org/wiki/Telcos.
[i.31] OCP Murata (2017): "Open compute power solutions". 4 pp.
NOTE: Available at https://www.avnet.com/wps/wcm/connect/onesite/584cd2d9-7c90-4465-83bc-
15501e9bc430/Murata-ocp-EN-Brochure.pdf?MOD=AJPERES&CVID=lMbA3cq&CVID=lMbA3cq.
[i.32] Orange Intelec 2011 Marquet D, Foucault O, Acheen J, Turc JF, Szpek M, Brunarie J:
"Pre roll-out field test of 400 VDC power supply: The new alliance of Edison and Tesla towards
rd
energy efficiency". In Intelec 2011 - IEEE 33 International Telecommunications Energy
Conference, 8 pp., Amsterdam.
[i.33] Orange Intelec 2016 Foucault O, Marquet D, le Masson S: "400 VDC Remote Powering as an
alternative for power needs in new fixed and radio access networks". In Intelec 2016 - IEEE
International Telecommunications Energy Conference, TS19.3, 9 pp, Austin.
[i.34] Orange Intelec 2017 Marquet D, Foucault O, Pichon JM,, Hirose K, Bianco C, Hockley R:
"Telecom operators to accelerate the migration towards 400 volt direct current - Efficient
powering for telecom/ICT equipment and coupling sites to smart energy microgrids". In Intelec
2017 - IEEE International Telecommunications Energy Conference, pp. 196-203, Queensland.
[i.35] Orange Intelec 1999 Marquet D, San Miguel F, Gabillet JP: "New power supply optimised for new
st
telecom networks and services". In Intelec 1999 - IEEE 21 International Telecommunication
Energy Conference, 25-1. 8 pp., Copenhagen.
[i.36] Orange Intelec 2005 Marquet D, Kervarrec G, Foucault O: "New flexible powering architecture
th
for integrated service operators". In Intelec 2005 - IEEE 27 International Telecommunications
Conference, pp. 575-580, Berlin.
[i.37] Schneider WP 151 Rasmussen N (undated): "Review of four studies comparing efficiency of AC
and DC distribution for data centers". White Paper 151, Rueil-Malmaison: Schneider Electric,
12 pp.
[i.38] Schneider WP 127 Rasmussen N, Spitaels J (undated): "A quantitative comparison of high
efficiency AC vs. DC power distribution for data centers". White Paper 127, Rev 2.
Rueil-Malmaison: Schneider Electric, 23 pp.
[i.39] Telstra Intelec 2017 Yong M, Bettle D: "Deploying HVDC in existing network exchanges:
Practical and financial benefits for telecommunications carriers". In Intelec 2017 - IEEE
International Telecommunications Energy Conference, pp. 204-207, Queensland.
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady-state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
NOTE: Available in ETSI EN 300 132-2 [2].
advanced battery: battery of more performant technology, e.g. lithium battery compared to mainly used legacy battery
technology used in telecommunication and data centres, i.e. Valve-Regulated Lead-Acid (VRLA)
DC/DC converter: power electronic system that transfers energy from one DC voltage (level) to another DC voltage
(level)
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
ETSI
12 ETSI ES 203 726 V1.1.1 (2022-08)
interface "A": terminals, at which the power supply is connected to the system block
NOTE: Available in ETSI EN 300 132-2 [2].
interface A1: interface, physical point, at which AC power supply is connected in order to operate the
telecommunications and datacom (ICT) equipment
interface A3: interface, physical point, at which power supply is connected in order to operate the telecommunications
and datacom (ICT) equipment
NOTE: Available in ETSI EN 300 132-1 [1].
load, load equipment: power consuming equipment that is part of a system block
normal operation: operation in typical environmental and powering conditions for telecommunications and datacom
(ICT) equipment, power supply, power distribution and battery at normal service
normal service: service mode where telecommunications and datacom (ICT) equipment operates within its
specification which includes a defined restart time after malfunction or full interruption
NOTE: Available in ETSI EN 300 132-2 [2].
normal service voltage range: range of the steady-state voltages over which the equipment will maintain normal
service
NOTE: Available in ETSI EN 300 132-2 [2].
power supply: power source to which telecommunication and datacom (ICT) equipment is intended to be connected
NOTE: A power source can be at building level, room level, rack level or a unit inside ICT equipment that feeds
power at a defined interface where it is required.
system block: functional group of telecommunications and datacom (ICT) equipment depending on its connection to
the same power supply for its operation and performance
telecommunication centre: any location where telecommunications and datacom (ICT) equipment is installed and is the
sole responsibility of the operator
NOTE: Available in ETSI EN 300 132-3-1 [i.8].
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
4G fourth Generation
5G fifth Generation
AC Alternating Current
AC ICT AC Information & Communication Technology
AC UPS AC Uninterruptable Power Supply
ATS Automatic Transfer Switch
CAPEX Capital Expenditure
DC Direct Current
DCC DC Components
DCC+G DC Components and Grids
DoD Depth of Discharge
EMC ElectroMagnetic Compatibility
FTTx Fibre To The x
HRMG High Resistance Middle point Grounding
HVDC High-Voltage Direct Current
ETSI
13 ETSI ES 203 726 V1.1.1 (2022-08)
ICT Information and Communication Technology
IEC International Electrotechnical Commission
IT Information Technology
ITU-T International Telecommunications Union - Telecommunication
KPI Key Performance Indicator
LCA Life Cycle Assessment
MTBF Mean Time Between Failures
MW MegaWatt
NTT Nippon Telegraph and Telecom
O&M Operation and Maintenance
OCP Open Closed Principle
OPEX OPeration EXpenditure
PDU Power Distribution Unit
PFC Power Factor Correction
POL Point Of Load
PSU Power Supply Unit
PV Photovoltaic
REN RENewable Energy
TC Technical Committee
TCO Total Cost Ownership
UPS Uninterruptible Power Supply
USA United States of America
VAC Volts Alternating Current
VDC Volts Direct Current
VRLA Valve-Regulated Lead-Acid
WP White Paper
4 Present situation of a telecommunication or data
centre powering solution and motivation for migration
to up to 400 VDC
Figure 1 presents a mixed power system architecture with the various interfaces A, A3 and A3ac, and interconnection to
an AC board and back-up engine generator, as it will appear during the migration period in most of legacy
telecommunication operators' buildings.
Figure 1 shows the drawbacks of existing powering -48 V and AC Uninterruptible Power Supply (UPS) solutions, and
where improvements should progressively be made when building new generation rooms or upgrading existing rooms
with up to 400 VDC in telecommunication/ICT buildings.
The ICT power supply interfaces considered in the present document shall be ETSI EN 300 132-2 [2] for -48 V, ETSI
EN 300 132-1 [1] for AC and Recommendation ITU-T L.1200 [11] or ETSI EN 300 132-3 [3] for up to 400 VDC.
The motivations for migration to up to 400 VDC solutions are to reduce the drawbacks of -48 V and AC solutions
shown in Figure 1 by aiming for the ultimate target defined in the architecture shown in Figure 2, which offers the
following advantages:
• Power architecture unification by progressively using a single up to 400 VDC power interface on loads.
Different migration steps are possible, from less to more benefit, as described in clause 7.
• Simplification of architecture and maintenance (e.g. with more modular solutions) by using the up to 400 VDC
architecture defined in Recommendation ITU-T L.1204 [14].
• Energy efficiency and energy cost reduction with dynamic saving modes as in 48 V that can be assessed by
using a comparative evaluation specified in Recommendation ITU-T L.1202 [12]. More than 3 % can be saved
on energy consumption and more than 80 % on material and labour cost, as assessed in Annex C.
• Lower copper and installation costs, progressive installation by modularity. Copper use could be decreased by
a factor of 10, resulting in a simpler and faster installation, easier upgrades and the flexibility to adapt to new
product developments. Integration of REN could be also simplified. Assessment is described in Annex C.
ETSI
14 ETSI ES 203 726 V1.1.1 (2022-08)
• Reliability and dependability improvement. The comparative evaluation of up to 400 VDC versus -48 V and
AC interfaces shall be established by the methods specified in Recommendation ITU-T L.1202 [12].
NOTE 1: Compared to UPS installation at comparable prices, unavailability can be improved by a factor of 10, as
reported in "A tool for calculating reliability of power supply for information and communication
technology systems" [i.13] and "DC power wide spread in Telecom/Datacenter and in home/office with
renewable energy and energy autonomy" [i.14].
• Lower life cycle environmental impacts (less copper, less complex equipment, longer lifetime, less number
and capacity of battery use and more modularity, etc.). This shall be evaluated by the Life Cycle Assessment
(LCA) environmental impact in compliance with ETSI ES 203 199 [7] or Recommendation ITU-T
L.1410 [18], technical equivalent, assessment methods.
The up to 400 VDC loads architecture can have an impact on specific aspects not fully covered in the present document
such as:
• more on site power generation in terms of solar and wind with local power storage to try to minimize power
drawn from the grid when grid supply is used only as a backup source;
• excess renewable power generation sold back to the grid and utility supply selection in attempts to minimize
utility cost;
• a possible future requirement for centre power autonomy that might make the most of the supply distribution
system that is dormant most of the time.

Figure 1: Legacy power architecture in common telecommunication or data centres at the start of
migration to up to 400 VDC at level of power station, distribution and load equipment
NOTE 2: Text blocks highlighted in green indicate improvements and those in red drawbacks of existing solutions.
ETSI
15 ETSI ES 203 726 V1.1.1 (2022-08)

Figure 2: Expanded ultimate target migration to up to 400 VDC principle with all options
NOTE 3: The indicated power interface refers to standard up to 400 VDC Recommendation ITU-T L.1200 [11] or
ETSI EN 300 132-3 [3], 48 V ETSI EN 300 132-2 [2], AC ETSI EN 300 132-1 [1], Remote Powering
ETSI EN 302 099 [i.4].
As far as possible, a common approach is applied for telecommunication and data centres for local power distribution,
but very high power in a data centre (multi-megawatt) might introduce some differences as presented in Annex B and
clause 5.5.
The potential savings are at the levels of:
• power plant;
• distribution;
• loads.
The connection of a solar power system to up to 400 VDC local distribution presented in Figure 1 is not described in
detail in the present document; it shall comply with ETSI ES 203 474 [9] or the technically equivalent Recommendation
ITU-T L.1205 [15].
If data centres are looking to become more autonomous from the utility, this can also mean more emphasis on local site
power solutions and the impact on electricity supply network has to be considered.
Depending on the battery usage approach, there can be an impact on the architecture depending on the strictness of the
regulation for charge control, as discussed in clause 6.
There can be single or bidirectional flow on the DC nanogrid as presented in Intelligent DC Microgrid Living Lab
[i.12].
ETSI
16 ETSI ES 203 726 V1.1.1 (2022-08)
In general, the migration steps towards up to 400 VDC solutions would be as shown in Figure 3, and described as
follows:
• install a centralized up to 400 VDC power station, and up to 400 VDC distribution to ICT rooms on given sites
or other user equipment (e.g. cooling);
• add u
...

SLOVENSKI STANDARD
01-oktober-2022
Okoljski inženiring (EE) - Postopna migracija informacijske in komunikacijske
tehnologije (IKT) na virih in distribuciji 400 VDC
Environmental Engineering (EE) - Progressive migration of Information and
Communication Technology (ICT) site to 400 VDC sources and distribution
Ta slovenski standard je istoveten z: ETSI ES 203 726 V1.1.1 (2022-08)
ICS:
19.040 Preskušanje v zvezi z Environmental testing
okoljem
35.020 Informacijska tehnika in Information technology (IT) in
tehnologija na splošno general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

ETSI STANDARD
Environmental Engineering (EE);
Progressive migration of Information and
Communication Technology (ICT) site to
400 VDC sources and distribution

2 ETSI ES 203 726 V1.1.1 (2022-08)

Reference
DES/EE-0260
Keywords
energy efficiency, power supply, site engineering

ETSI
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ETSI
3 ETSI ES 203 726 V1.1.1 (2022-08)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Executive summary . 5
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 9
3 Definition of terms, symbols and abbreviations . 11
3.1 Terms . 11
3.2 Symbols . 12
3.3 Abbreviations . 12
4 Present situation of a telecommunication or data centre powering solution and motivation for
migration to up to 400 VDC . 13
5 General evolution cases during migration . 17
5.1 Present situation . 17
5.2 DC/DC converter related considerations . 20
5.3 400/AC migration inverter consideration . 21
5.4 Long distance transport in -48 V/up to 400 VDC/-48 V in centre and multistep migration . 23
5.5 Combined migration cases . 24
5.6 Grid/back-up generator 400 DC switch replacing AC mechanical switch . 25
6 Up to 400 VDC batteries . 26
7 Migration of up to 400 VDC remote power to local up to 400 VDC power system . 26
8 Coupling renewable energy to existing buildings distribution with migration to up to 400 VDC . 27
9 Up to 400 VDC cabling, earthing and bonding in the migration period . 27
10 Electrical safety requirements . 28
11 Electromagnetic compatibility requirements at the input of telecommunication and datacom (ICT)
equipment . 28
12 Impacts on energy efficiency and other key performance indicators (environmental impact, life
cycle assessment) . 29
Annex A (normative): Power supply and interface considerations . 30
Annex B (informative): Information on some papers on up to 400 VDC migration solutions,
advantages and implementation decision and process . 31
Annex C (informative): Details on some saving assessment of migration to up to 400 VDC . 32
C.0 Overview . 32
C.1 Energy efficiency . 32
C.2 Energy cost reduction . 32
C.3 Saving on material, area in ICT room and labour . 33
C.4 Less copper and installation cost, progressive installation by modularity . 33
C.4.0 Overview . 33
ETSI
4 ETSI ES 203 726 V1.1.1 (2022-08)
C.4.1 Reliability and dependability improvement (comparative evaluation using Recommendation
ITU-T L.1202) . 34
C.4.2 Lower life cycle environmental impacts . 34
C.4.3 Solar power input to power distribution . 34
C.4.4 Open innovation . 34
History . 35

ETSI
5 ETSI ES 203 726 V1.1.1 (2022-08)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to normative deliverables may have been declared to ETSI. The declarations
pertaining to these essential IPRs, if any, are publicly available for ETSI members and non-members, and can be
found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to
ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the
ETSI Web server (https://ipr.etsi.org/).
Pursuant to the ETSI Directives including the ETSI IPR Policy, no investigation regarding the essentiality of IPRs,
including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not
referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become,
essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its

Members. 3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and of the 3GPP
Organizational Partners. oneM2M™ logo is a trademark of ETSI registered for the benefit of its Members and of the ®
oneM2M Partners. GSM and the GSM logo are trademarks registered and owned by the GSM Association.
Foreword
This ETSI Standard (ES) has been produced by ETSI Technical Committee Environmental Engineering (EE).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Executive summary
The present document gives explanation, requirements and guidance for increasing the use of up to 400 V Direct
Current (400 VDC) power systems and the distribution to Information and Communication Technology (ICT)
equipment. It includes 400 VDC remote powering up to 400 VDC of distributed ICT equipment, the option of
interconnection of local renewable energy sources and their connection to DC power nanogrids and other users,
extending the resilience capability of the telecommunication network and ICT sites to grid failures and climate change.
ETSI
6 ETSI ES 203 726 V1.1.1 (2022-08)
Introduction
Telecommunication network energy consumption and cost are increasing at a rate of several percentage points per year
as reported in Trends in worldwide ICT electricity consumption from 2007 to 2012 [i.11]. The use of up to 400 V Direct
Current (400 VDC) architecture (as presented in Table 1, Annex B and Annex C) can result in significant savings.
The use of up to 400 VDC solutions result in energy savings with higher efficiency and reduced distribution losses,
reduction in maintenance cost due to higher reliability and lower unavailability, savings in space for power equipment
in Information and Communication Technology (ICT) rooms (each square metre being of high cost) and, finally, more
simplicity in site installation and development.
Different levels of saving and improvement result from a comparison of up to 400 VDC solutions to -48 V solutions
(copper savings) or to Uninterrupted Power Supply (UPS) solutions (reliability, efficiency, easier installation).
400 VDC remote power can be beneficial.
As for the power system, energy savings in addition to those resulting from efficiency improvements depend on the load
in the telecommunication or data centre. Energy efficiency should be evaluated at the system level, including the
general distribution cabling and voltage conversion stages, as well as the internal power circuits inside the load
downstream of the power interface, i.e. conversion architecture in the system (e.g. dual inputs, local back-up, AC/DC
rectifier losses).
Indirect savings of up to 400 VDC solutions relate to lifecycle in the production and recycling phase as there should be
less passage through copper and electronics as well as less battery usage for given output power and system
dependability. Battery capacity and dependability savings are achieved by removing inverter losses if replacing AC
UPS or by reducing -48 V distribution losses.
The present document specifies requirements for a safe migration of an existing site to a unified up to 400 VDC
powering feeding system, power distribution and the power interface of telecommunication/ICT equipment. It includes
requirements relating to the stability, cabling, earthing, as well as bonding and measurement, for the existing site.
The main significant components of up to 400 VDC equipment and additional progressive migration equipment are
presented in Figures 2 and 3. These are schematic diagrams that do not show all the electrical arrangement details. The
architecture under consideration complies with Recommendation ITU-T L.1204 [14] on electrical architecture,
including energy storage defined in ETSI TS 103 553-1 [i.1] or Recommendation ITU-T L.1220 [i.2], technically
equivalent, and with ETSI ES 203 474 [9] or Recommendation ITU-T L.1205 [15], technically equivalent, for DC
coupling of a local RENewable Energy (REN) system on site or with DC nano/micro grid interconnecting sites with
REN sources and storage or ICT equipment requiring remote powering. Smart DC nanogrids are under study as
reported in Intelligent DC Microgrid Living Lab [i.12].
The migration simplifies the use of up to 400 VDC combined with REN and DC nanogrids and should extend resilience
capability of telecommunication networks sites to grid failures and climate change.
The present document was developed jointly by ETSI TC EE and ITU-T Study Group 5. It is published respectively by
ITU and ETSI as Recommendation ITU-T L.1207 [i.3] and ETSI ES 203 726 (the present document), which are
technically-equivalent.
ETSI
7 ETSI ES 203 726 V1.1.1 (2022-08)
1 Scope
The present document defines solutions for progressive migration of Information and Communication Technology
(ICT) sites (telecommunication and data centres) to up to 400 V Direct Current (400 VDC) distribution and direct use of
up to 400 VDC powering ICT equipment from 400 VDC sources. The present document also defines different major
use case options and migration scenarios, such as:
• migration to an up to 400 VDC of telecommunication site power solution;
• migration to an up to 400 VDC of data centre power solution;
• migration with up to 400 VDC power transfer between existing -48 V centralized sources to high power
density -48 V equipment, such as routers;
• integration of up to 400 VDC remote powering;
• combined architecture with up to 400 VDC and AC sources and distributions possibly using hybrid power
interfaces on ICT equipment.
For each of these, the present document describes many possible options and characteristics, such as:
• migration architecture with up to 400 VDC/-48 V conversion to power existing -48 V equipment using
existing -48 V room distribution;
• conditions for tripping overcurrent protection devices without -48 V batteries;
• migration architecture with up to 400 VDC/AC inverter as an alternative to the AC UPS to power existing AC
equipment;
• use of local up to 400 VDC for remote powering of ICT equipment;
• coupling up to 400 VDC systems to a local REN source or to a DC microgrid;
• possibility of conversion between battery and up to 400 VDC distribution, e.g. for long power distribution or
short-circuit current or battery technology (e.g. lithium-ion).
The present document also gives a saving assessment frame reference to define the best migration scenario and its steps
by considering energy, resource, environmental impact and cost savings based on functional aspects such as modularity,
flexibility, reliability, efficiency and distribution losses, as well as maintenance evolution when migrating from -48 V or
Alternating Current (AC) to up to 400 VDC solutions. This also includes consideration of load architecture evolution
dependent on use cases (e.g. telecommunication site, data centres).
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI EN 300 132-1 (V2.1.1) (2019): "Environmental Engineering (EE); Power supply interface at
the input to Information and Communication Technology (ICT) equipment; Part 1: Alternating
Current (AC)".
ETSI
8 ETSI ES 203 726 V1.1.1 (2022-08)
[2] ETSI EN 300 132-2 (V2.6.1) (2019): "Environmental Engineering (EE); Power supply interface at
the input of Information and Communication Technology (ICT) equipment; Part 2: -48 V Direct
Current (DC)".
[3] ETSI EN 300 132-3 (V1.2.1) (2003): "Environmental Engineering (EE); Power supply interface at
the input to telecommunications equipment; Part 3: Operated by rectified current source,
alternating current source or direct current source up to 400 V".
[4] ETSI EN 300 253 (V2.2.1) (2015): "Environmental Engineering (EE); Earthing and bonding of
ICT equipment powered by -48 VDC in telecom and data centres".
[5] ETSI EN 301 605 (V1.1.1) (2013): "Environmental Engineering (EE); Earthing and bonding of
400 VDC data and telecom (ICT) equipment".
[6] ETSI ES 202 336-2 (V1.1.1) (2009): "Environmental Engineering (EE); Monitoring and control
interface for infrastructure equipment (Power, Cooling and environment systems used in
telecommunication networks); Part 2: DC power system control and monitoring information
model".
[7] ETSI ES 203 199 (V1.3.1) (2015): "Environmental Engineering (EE); Methodology for
environmental Life Cycle Assessment (LCA) of Information and Communication Technology
(ICT) goods, networks and services".
[8] ETSI ES 203 408 (V1.1.1): "Environmental Engineering (EE); Colour and marking of DC cable
and connecting devices".
[9] ETSI ES 203 474 (V1.1.1): "Environmental Engineering (EE); Interfacing of renewable energy or
distributed power sources to 400 VDC distribution systems powering Information and
Communication Technology (ICT) equipment".
[10] ETSI TS 103 531 (V1.1.1): "Environmental Engineering (EE); Impact on ICT equipment
architecture of multiple AC, -48 VDC or up to 400 VDC power inputs".
[11] Recommendation ITU-T L.1200 (2012): "Direct current power feeding interface up to 400 V at the
input to telecommunication and ICT equipment".
[12] Recommendation ITU-T L.1202 (2015): "Methodologies for evaluating the performance of an up
to 400 VDC power feeding system and its environmental impact".
[13] Recommendation ITU-T L.1203 (2016): "Colour and marking identification of up to 400 VDC
power distribution for information and communication technology systems".
[14] Recommendation ITU-T L.1204 (2016): "Extended architecture of power feeding systems of up to
400 VDC".
[15] Recommendation ITU-T L.1205 (2016): "Interfacing of renewable energy or distributed power
sources to up to 400 VDC power feeding systems".
[16] Recommendation ITU-T L.1206 (2017): "Impact on ICT equipment architecture of multiple
AC, -48 VDC or up to 400 VDC power inputs".
[17] Recommendation ITU-T L.1320 (2014): "Energy efficiency metrics and measurement for power
and cooling equipment for telecommunications and data centres".
[18] Recommendation ITU-T L.1410 (2014): "Methodology for environmental life cycle assessments
of information and communication technology goods, networks and services".
[19] IEC 60364 (all parts): "Low-voltage electrical installations".
ETSI
9 ETSI ES 203 726 V1.1.1 (2022-08)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TS 103 553-1 (V1.1.1): "Environmental Engineering (EE); Innovative energy storage
technology for stationary use; Part 1: Overview".
[i.2] Recommendation ITU-T L.1220 (2017): "Innovative energy storage technology for stationary use
- Part 1: Overview of energy storage".
[i.3] Recommendation ITU-T L.1207 (2018-05): "Progressive migration of a
telecommunication/information and communication technology site to 400 VDC sources and
distribution".
[i.4] ETSI EN 302 099 (V2.1.1) (2014): "Environmental Engineering (EE); Powering of equipment in
access network".
[i.5] Recommendation ITU-T K.48 (2017): "EMC requirements for telecommunication equipment -
Product family Recommendation".
[i.6] IEC 60950-1: "Information technology equipment - Safety - Part 1: General requirements".
[i.7] IEC 62368-1: "Audio/video, information and communication technology equipment - Part 1:
Safety requirements".
[i.8] ETSI EN 300 132-3-1 (V2.1.1) (2012): "Environmental Engineering (EE); Power supply interface
at the input to telecommunications and datacom (ICT) equipment; Part 3: Operated by rectified
current source, alternating current source or direct current source up to 400 V; Sub-part 1: Direct
current source up to 400 V".
[i.9] ETSI EN 300 386 (V2.1.1) (2016): "Telecommunication network equipment; ElectroMagnetic
Compatibility (EMC) requirements; Harmonised Standard covering the essential requirements of
the Directive 2014/30/EU".
[i.10] ETSI TR 100 283 (V2.2.1) (2007): "Environmental Engineering (EE); Transient voltages at
Interface "A" on telecommunications direct current (dc) power distributions".
[i.11] Van Heddeghem W., Lambert S., Lannoo B., Colle D., Pickavet M., Demeester P. (2014): "Trends
in worldwide ICT electricity consumption from 2007 to 2012". Computer Communications, 50,
64-76.
NOTE: Available at https://doi.org/10.1016/j.comcom.2014.02.008.
[i.12] Aalborg University: "Intelligent DC Microgrid Living Lab".
[i.13] Tsumura T, Takeda T, Hirose K (2008): "A tool for calculating reliability of power supply for
th
information and communication technology systems". In Intelec 2008 - IEEE 30 International
Telecommunications Energy Conference, 21.3, 6 pp., San Diego.
[i.14] Marquet D, Tanaka T, Murai K, Tanaka T, Babasaki T (2013): "DC power wide spread in
Telecom/Datacenter and in home/office with renewable energy and energy autonomy". In Intelec
th
2013 - IEEE 35 International Telecommunications Energy Conference, Smart Power and
Efficiency, pp. 499-504, Hamburg.
[i.15] Caltech Berkeley 2017 Vossos V, Johnson K, Kloss M, Khattar M, Gerber D, Brown R: "Review
of DC power distribution in buildings: A technology and market assessment" pp.71.
ETSI
10 ETSI ES 203 726 V1.1.1 (2022-08)
[i.16] Schneider WP 118 Rasmussen N (undated): "High-efficiency AC power distribution for data
centers". White Paper 128. Rueil-Malmaison: Schneider Electric. 19 pp.
[i.17] CE+T Intelec 2016 Frebel F. (eFFiciency research), Bleus P. Bomboir O. (CE+T Power, sa):
"Transformer-less 2 kW non isolated 400 VDC/230 VAC single stage micro inverter". In Intelec
2016 - IEEE International Telecommunications Energy Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/7749105.
[i.18] CATR Intelec 2012 Qi S, Hou F, Jing H: "Study and application on high voltage DC power
th
feeding system for telecommunications in China". In Intelec 2012 - IEEE 34 International
Telecommunications Energy Conference, pp. 9.1. 5, Scottsdale.
NOTE: Available at https://ieeexplore.ieee.org/xpl/conhome/6362321/proceeding.
[i.19] CAICT Intelec 2017 Qi S, Sun W, Wu Y: "Comparative analysis on different architectures of
power supply system for data center and telecom center". In Intelec 2017 - IEEE International
Telecommunications Energy Conference, pp. 26-29, Queensland.
[i.20] DCC+G Fraunhofer 2014 Wunde B: "380 VDC in commercial buildings and offices". Presentation
at Vicor Seminar 2014. 71 slides.
NOTE: Available at http://dcgrid.tue.nl/files/2014-02-11%20-%20Webinar%20Vicor.pdf.
[i.21] Fraunhofer Safety Intelec 2017 Kaiser J et al.: "Safety consideration for the operation of bipolar
DC grids". In Intelec 2017 - IEEE International Telecommunications Energy Conference,
pp. 327-334, Queensland.
[i.22] Fraunhofer Droop Intelec 2017 Wunder B et al.: "Droop controlled cognitive power electronics for
DC microgrids". In Intelec 2017 - IEEE International Telecommunications Energy Conference,
pp. 335-342, Queensland.
[i.23] Void.
[i.24] Fujitsu-NTT-Appliance coupler-Intelec 2017 Kiryu K, Tanaka T, Sato K, Seki K, Hirose K:
"Development of appliance coupler for LVDC in Information Communication Technology (ICT)
equipment with having a protection of inrush current and arc". In Intelec 2017 - IEEE International
Telecommunications Energy Conference, pp. 343-346, Queensland.
[i.25] level3-Eltek Intelec 2016 Ambriz A. (Level 3 Communications), Kania M. (Eltek): "A service
provider's decision to move from 48V to 380V powering: The problem statement, technical
assessment, financial analysis and practical implementation plan". In Intelec 2016 - IEEE
International Telecommunications Energy Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/7749117.
[i.26] NTT Intelec 1999 Yamashita T, Muroyama S, Furubo S, Ohtsu S: "270 VDC System - A highly
efficient and reliable power supply system for both telecom and datacom systems". In Intelec 1999
st
- IEEE 21 International Telecommunication Energy Conference, PI 1-3. 5 pp., Copenhagen.
[i.27] NTT-f Intelec 2016 Hiroya Yajima, Kenichi Usui, Toshiyuki Hayashi (R&D and datacenter,
NTT Facilities Japan): "Energy-saving effects of super computers by using on-site solar power and
direct HVDC feeding systems". In Intelec 2016 - IEEE International Telecommunications Energy
Conference, Austin.
NOTE: Available at https://ieeexplore.ieee.org/document/8214133.
[i.28] NTT-f Intelec 2011 Hirose K, Tanaka T, Babasaki T, Person S, Foucault O, Sonnenberg BJ,
Szpek M: "Grounding concept considerations and recommendations for 400 VDC distribution
rd
system". In Intelec 2011 - IEEE 33 International Telecommunications Energy Conference, 8 pp.,
Amsterdam.
[i.29] NTT Intelec 2012 Tanaka T, Hirose K, Marquet D, Sonnenberg BJ, Szpek M: "Analysis of wiring
design for 380-VDC power distribution system at telecommunication sites". In Intelec 2012 -
th
IEEE 34 International Telecommunications Energy Conference, 15.2. 5 pp., Scottsdale.
ETSI
11 ETSI ES 203 726 V1.1.1 (2022-08)
[i.30] OCP Orange: "400 VDC power feeding architecture", OCP 2017.
NOTE: Available at http://www.opencompute.org/wiki/Telcos.
[i.31] OCP Murata (2017): "Open compute power solutions". 4 pp.
NOTE: Available at https://www.avnet.com/wps/wcm/connect/onesite/584cd2d9-7c90-4465-83bc-
15501e9bc430/Murata-ocp-EN-Brochure.pdf?MOD=AJPERES&CVID=lMbA3cq&CVID=lMbA3cq.
[i.32] Orange Intelec 2011 Marquet D, Foucault O, Acheen J, Turc JF, Szpek M, Brunarie J:
"Pre roll-out field test of 400 VDC power supply: The new alliance of Edison and Tesla towards
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energy efficiency". In Intelec 2011 - IEEE 33 International Telecommunications Energy
Conference, 8 pp., Amsterdam.
[i.33] Orange Intelec 2016 Foucault O, Marquet D, le Masson S: "400 VDC Remote Powering as an
alternative for power needs in new fixed and radio access networks". In Intelec 2016 - IEEE
International Telecommunications Energy Conference, TS19.3, 9 pp, Austin.
[i.34] Orange Intelec 2017 Marquet D, Foucault O, Pichon JM,, Hirose K, Bianco C, Hockley R:
"Telecom operators to accelerate the migration towards 400 volt direct current - Efficient
powering for telecom/ICT equipment and coupling sites to smart energy microgrids". In Intelec
2017 - IEEE International Telecommunications Energy Conference, pp. 196-203, Queensland.
[i.35] Orange Intelec 1999 Marquet D, San Miguel F, Gabillet JP: "New power supply optimised for new
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telecom networks and services". In Intelec 1999 - IEEE 21 International Telecommunication
Energy Conference, 25-1. 8 pp., Copenhagen.
[i.36] Orange Intelec 2005 Marquet D, Kervarrec G, Foucault O: "New flexible powering architecture
th
for integrated service operators". In Intelec 2005 - IEEE 27 International Telecommunications
Conference, pp. 575-580, Berlin.
[i.37] Schneider WP 151 Rasmussen N (undated): "Review of four studies comparing efficiency of AC
and DC distribution for data centers". White Paper 151, Rueil-Malmaison: Schneider Electric,
12 pp.
[i.38] Schneider WP 127 Rasmussen N, Spitaels J (undated): "A quantitative comparison of high
efficiency AC vs. DC power distribution for data centers". White Paper 127, Rev 2.
Rueil-Malmaison: Schneider Electric, 23 pp.
[i.39] Telstra Intelec 2017 Yong M, Bettle D: "Deploying HVDC in existing network exchanges:
Practical and financial benefits for telecommunications carriers". In Intelec 2017 - IEEE
International Telecommunications Energy Conference, pp. 204-207, Queensland.
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
abnormal service voltage range: range of steady-state voltage over which the equipment will not be expected to
maintain normal service but will survive undamaged
NOTE: Available in ETSI EN 300 132-2 [2].
advanced battery: battery of more performant technology, e.g. lithium battery compared to mainly used legacy battery
technology used in telecommunication and data centres, i.e. Valve-Regulated Lead-Acid (VRLA)
DC/DC converter: power electronic system that transfers energy from one DC voltage (level) to another DC voltage
(level)
ICT equipment: device, in the telecommunication network infrastructure, that provides an ICT service
ETSI
12 ETSI ES 203 726 V1.1.1 (2022-08)
interface "A": terminals, at which the power supply is connected to the system block
NOTE: Available in ETSI EN 300 132-2 [2].
interface A1: interface, physical point, at which AC power supply is connected in order to operate the
telecommunications and datacom (ICT) equipment
interface A3: interface, physical point, at which power supply is connected in order to operate the telecommunications
and datacom (ICT) equipment
NOTE: Available in ETSI EN 300 132-1 [1].
load, load equipment: power consuming equipment that is part of a system block
normal operation: operation in typical environmental and powering conditions for telecommunications and datacom
(ICT) equipment, power supply, power distribution and battery at normal service
normal service: service mode where telecommunications and datacom (ICT) equipment operates within its
specification which includes a defined restart time after malfunction or full interruption
NOTE: Available in ETSI EN 300 132-2 [2].
normal service voltage range: range of the steady-state voltages over which the equipment will maintain normal
service
NOTE: Available in ETSI EN 300 132-2 [2].
power supply: power source to which telecommunication and datacom (ICT) equipment is intended to be connected
NOTE: A power source can be at building level, room level, rack level or a unit inside ICT equipment that feeds
power at a defined interface where it is required.
system block: functional group of telecommunications and datacom (ICT) equipment depending on its connection to
the same power supply for its operation and performance
telecommunication centre: any location where telecommunications and datacom (ICT) equipment is installed and is the
sole responsibility of the operator
NOTE: Available in ETSI EN 300 132-3-1 [i.8].
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
4G fourth Generation
5G fifth Generation
AC Alternating Current
AC ICT AC Information & Communication Technology
AC UPS AC Uninterruptable Power Supply
ATS Automatic Transfer Switch
CAPEX Capital Expenditure
DC Direct Current
DCC DC Components
DCC+G DC Components and Grids
DoD Depth of Discharge
EMC ElectroMagnetic Compatibility
FTTx Fibre To The x
HRMG High Resistance Middle point Grounding
HVDC High-Voltage Direct Current
ETSI
13 ETSI ES 203 726 V1.1.1 (2022-08)
ICT Information and Communication Technology
IEC International Electrotechnical Commission
IT Information Technology
ITU-T International Telecommunications Union - Telecommunication
KPI Key Performance Indicator
LCA Life Cycle Assessment
MTBF Mean Time Between Failures
MW MegaWatt
NTT Nippon Telegraph and Telecom
O&M Operation and Maintenance
OCP Open Closed Principle
OPEX OPeration EXpenditure
PDU Power Distribution Unit
PFC Power Factor Correction
POL Point Of Load
PSU Power Supply Unit
PV Photovoltaic
REN RENewable Energy
TC Technical Committee
TCO Total Cost Ownership
UPS Uninterruptible Power Supply
USA United States of America
VAC Volts Alternating Current
VDC Volts Direct Current
VRLA Valve-Regulated Lead-Acid
WP White Paper
4 Present situation of a telecommunication or data
centre powering solution and motivation for migration
to up to 400 VDC
Figure 1 presents a mixed power system architecture with the various interfaces A, A3 and A3ac, and interconnection to
an AC board and back-up engine generator, as it will appear during the migration period in most of legacy
telecommunication operators' buildings.
Figure 1 shows the drawbacks of existing powering -48 V and AC Uninterruptible Power Supply (UPS) solutions, and
where improvements should progressively be made when building new generation rooms or upgrading existing rooms
with up to 400 VDC in telecommunication/ICT buildings.
The ICT power supply interfaces considered in the present document shall be ETSI EN 300 132-2 [2] for -48 V, ETSI
EN 300 132-1 [1] for AC and Recommendation ITU-T L.1200 [11] or ETSI EN 300 132-3 [3] for up to 400 VDC.
The motivations for migration to up to 400 VDC solutions are to reduce the drawbacks of -48 V and AC solutions
shown in Figure 1 by aiming for the ultimate target defined in the architecture shown in Figure 2, which offers the
following advantages:
• Power architecture unification by progressively using a single up to 400 VDC power interface on loads.
Different migration steps are possible, from less to more benefit, as described in clause 7.
• Simplification of architecture and maintenance (e.g. with more modular solutions) by using the up to 400 VDC
architecture defined in Recommendation ITU-T L.1204 [14].
• Energy efficiency and energy cost reduction with dynamic saving modes as in 48 V that can be assessed by
using a comparative evaluation specified in Recommendation ITU-T L.1202 [12]. More than 3 % can be saved
on energy consumption and more than 80 % on material and labour cost, as assessed in Annex C.
• Lower copper and installation costs, progressive installation by modularity. Copper use could be decreased by
a factor of 10, resulting in a simpler and faster installation, easier upgrades and the flexibility to adapt to new
product developments. Integration of REN could be also simplified. Assessment is described in Annex C.
ETSI
14 ETSI ES 203 726 V1.1.1 (2022-08)
• Reliability and dependability improvement. The comparative evaluation of up to 400 VDC versus -48 V and
AC interfaces shall be established by the methods specified in Recommendation ITU-T L.1202 [12].
NOTE 1: Compared to UPS installation at comparable prices, unavailability can be improved by a factor of 10, as
reported in "A tool for calculating reliability of power supply for information and communication
technology systems" [i.13] and "DC power wide spread in Telecom/Datacenter and in home/office with
renewable energy and energy autonomy" [i.14].
• Lower life cycle environmental impacts (less copper, less complex equipment, longer lifetime, less number
and capacity of battery use and more modularity, etc.). This shall be evaluated by the Life Cycle Assessment
(LCA) environmental impact in compliance with ETSI ES 203 199 [7] or Recommendation ITU-T
L.1410 [18], technical equivalent, assessment methods.
The up to 400 VDC loads architecture can have an impact on specific aspects not fully covered in the present document
such as:
• more on site power generation in terms of solar and wind with local power storage to try to minimize power
drawn from the grid when grid supply is used only as a backup source;
• excess renewable power generation sold back to the grid and utility supply selection in attempts to minimize
utility cost;
• a possible future requirement for centre power autonomy that might make the most of the supply distribution
system that is dormant most of the time.

Figure 1: Legacy power architecture in common telecommunication or data centres at the start of
migration to up to 400 VDC at level of power station, distribution and load equipment
NOTE 2: Text blocks highlighted in green indicate improvements and those in red drawbacks of existing solutions.
ETSI
15 ETSI ES 203 726 V1.1.1 (2022-08)

Figure 2: Expanded ultimate target migration to up to 400 VDC principle with all options
NOTE 3: The indicated power interface refers to standard up to 400 VDC Recommendation ITU-T L.1200 [11] or
ETSI EN 300 132-3 [3], 48 V ETSI EN 300 132-2 [2], AC ETSI EN 300 132-1 [1], Remote Powering
ETSI EN 302 099 [i.4].
As far as possible, a common approach is applied for telecommunication and data centres for local power distribution,
but very high power in a data centre (multi-megawatt) might introduce some differences as presented in Annex B and
clause 5.5.
The potential savings are at the levels of:
• power plant;
• distribution;
• loads.
The connection of a solar power system to up to 400 VDC local distribution presented in Figure 1 is not described in
detail in the present document; it shall comply with ETSI ES 203 474 [9] or the technically equivalent Recommendation
ITU-T L.1205 [15].
If data centres are looking to become more autonomous from the utility, this can also mean more emphasis on local site
power solutions and the impact on electricity supply network has to be considered.
Depending on the battery usage approach, there can be an impact on the architecture depending on the strictness of the
regulation for charge control, as discussed in clause 6.
There can be single or bidirectional flow on the DC nanogrid as presented in Intelligent DC Microgrid Living Lab
[i.12].
ETSI
16 ETSI ES 203 726 V1.1.1 (2022-08)
In general, the migration steps towards up to 400 VDC solutions would be as shown in Figure 3, and described as
follows:
• install a centralized up to 400 VDC power station, and up to 400 VDC distribution to ICT rooms on given sites
or other user equipment (e.g. cooling);
• add up t
...