ETSI TS 102 121 V1.4.1 (2025-02)

TECHNICAL SPECIFICATION
Environmental Engineering (EE);
Power distribution to telecommunications
and datacom (ICT) equipment
2 ETSI TS 102 121 V1.4.1 (2025-02)

Reference
RTS/EE-027015
Keywords
distribution, earthing, power, power supply, system
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ETSI
3 ETSI TS 102 121 V1.4.1 (2025-02)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 8
3.1 Terms . 8
3.2 Symbols . 8
3.3 Abbreviations . 8
4 Types of power supply systems . 9
4.0 Introduction . 9
4.1 DC supply . 9
4.1.1 Mains operation . 9
4.1.2 Battery operation . 9
4.1.3 Floating/Parallel operation . 10
4.1.3.0 General principles . 10
4.1.3.1 DC switch operation . 10
4.1.3.1.0 Operation between rectifier and battery . 10
4.1.3.1.1 Switch operation with interruption . 11
4.1.3.1.2 Switch operation without interruption . 11
4.1.3.2 DC converter operation . 11
4.1.3.3 Redundant DC distribution . 11
4.2 AC supply . 12
4.2.1 Mains operation . 12
4.2.2 Inverter operation . 12
4.2.3 AC switch operation . 12
4.2.3.1 AC switch operation with interruption . 12
4.2.3.2 AC switch operation without interruption (STS) . 13
4.2.3.3 AC uninterruptible power supply systems (UPS) . 13
4.2.4 Reliability and redundancy . 18
5 Power supply interfaces in telecommunication installations . 18
5.0 Basic forms of Power Suppyl Interfaces . 18
5.1 PSI 1 interface between primary power and telecommunication installations and equipment . 19
5.1.0 Definition . 19
5.1.1 Connection conditions . 19
5.1.2 Harmonics and superimposition . 20
5.1.3 Radio interference . 20
5.1.4 Disturbances on the customer installation . 20
5.1.5 Further sources of supply voltage . 20
5.2 PSI 2 interface . 20
5.2.0 Definition . 20
5.2.1 Connection conditions . 20
5.2.2 Radio interference . 21
5.2.3 Interference voltage . 21
5.3 PSI 3 interface between telecommunication installations or equipment and the telecommunication
networks . 21
5.3.0 Definition . 21
5.3.1 Connection conditions . 21
5.3.2 Operation with remote power feeding of current . 21
5.3.3 Operation with ringing AC voltage . 21
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4 ETSI TS 102 121 V1.4.1 (2025-02)
5.3.4 Radio interference . 22
5.3.5 Interference voltage . 22
5.4 Cabling and routing . 22
6 Earthing and equipotential bonding. 22
7 Electrical Safety requirements . 22
Annex A (normative): Principle of artificial DC mains network for measurement of
disturbance . 23
Annex B (informative): Power supply considerations . 24
History . 25

ETSI
5 ETSI TS 102 121 V1.4.1 (2025-02)
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 IPR online database.
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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Foreword
This Technical Specification (TS) 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.
Introduction
The present document gives guidance on installation, connection and operation of power supply systems for
telecommunication / datacom (ICT) systems and equipment. Also are considered items of equipment with their own
power supply, which are connected to form a complete system.
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6 ETSI TS 102 121 V1.4.1 (2025-02)
1 Scope
The present document gives guidance on installation, connection and operation of power supply systems for
telecommunication / datacom installations and equipments. Also are considered items of equipment with their own
power supply, which are connected to form a complete system installation.
The present document contains definitions for power supply and distribution systems in complement to power interfaces
standards ETSI EN 300 132 series [5], [6], [26].
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 in the
ETSI docbox.
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] IEC EN 60038: "IEC standard voltages".
[2] ETSI EN 300 386: "Telecommunication network equipment; ElectroMagnetic Compatibility
(EMC) requirements; Harmonised Standard covering the essential requirements of the Directive
2014/30/EU".
[3] EN 60950-1: "Information technology equipment - Safety - Part 1: General requirements",
(produced by CENELEC).
[4] EN 60896-21: "Stationary lead-acid batteries - Part 21: Valve regulated types - Methods of test",
(produced by CENELEC).
[5] ETSI EN 300 132-1: "Environmental Engineering (EE); Power supply interface at the input to
Information and Communication Technology (ICT) equipment; Part 1: Alternating Current (AC)".
[6] ETSI EN 300 132-2: "Environmental Engineering (EE); Power supply interface at the input to
telecommunications and datacom (ICT) equipment; Part 2: Operated by -48 V direct current
(DC)".
[7] ETSI EN 302 099: "Environmental Engineering (EE); Powering of equipment in access network".
[8] ETSI EN 300 253: "Environmental Engineering (EE); Earthing and bonding of ICT equipment
powered by -48 VDC in telecom and data centres".
[9] Recommendation ITU-T K.20: "Resistibility of telecommunication equipment installed in a
telecommunications centre to overvoltages and overcurrents".
[10] Recommendation ITU-T K.21: "Resistibility of telecommunication equipment installed in
customer premises to overvoltages and overcurrents".
[11] Recommendation ITU-T K.45: "Resistibility of telecommunication equipment installed in the
access and trunk networks to overvoltages and overcurrents".
[12] HD 384 (all parts)/HD 60364: "Electrical installations of buildings", (produced by CENELEC).
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7 ETSI TS 102 121 V1.4.1 (2025-02)
[13] ETSI EN 301 489-1: "ElectroMagnetic Compatibility (EMC) standard for radio equipment and
services; Part 1: Common technical requirements; Harmonised Standard for ElectroMagnetic
Compatibility".
[14] EN 61000-3-2: "Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic
current emissions (equipment input current ≤ 16 A per phase)", (produced by CENELEC).
[15] EN 61000-3-3: "Electromagnetic compatibility (EMC) - Part 3-3: Limits - Limitation of voltage
changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment with
rated current ≤ 16 A per phase and not subject to conditional connection", (produced by
CENELEC).
[16] Recommendation ITU-T P.53: "Psophometer for use on telephone-type circuits".
[17] EN 50310: "Application of equipotential bonding and earthing in buildings with information
technology equipment", (produced by CENELEC).
[18] EN 61000-4-11: "Electromagnetic compatibility (EMC) - Part 4-11: Testing and measurement
techniques - Voltage dips, short interruptions and voltage variations immunity tests", (produced by
CENELEC).
[19] EN 50174-2: "Information technology - Cabling installation - Part 2: Installation planning and
practices inside buildings", (produced by CENELEC).
[20] EN 62040-1-1: "Uninterruptible power systems (UPS) - Part 1-1: General and safety requirements
for UPS used in operator access areas", (produced by CENELEC).
[21] EN 62040-1-2: "Uninterruptible power systems (UPS) - Part 1-2: General and safety requirements
for UPS used in restricted access locations", (produced by CENELEC).
[22] EN 60896-11: "Stationary lead-acid batteries - Part 11: Vented types - General requirements and
methods of tests", (produced by CENELEC).
[23] EN 62310-1: "Static transfer systems (STS) - Part 1: General and safety requirements", (produced
by CENELEC).
[24] EN 60896-22: "Stationary lead-acid batteries - Part 22: Valve regulated types - Requirements",
(produced by CENELEC).
[25] ETSI EN 301 605: "Environmental Engineering (EE); Earthing and bonding of 400 V DC data and
telecom (ICT) equipment".
[26] ETSI EN 300 132-3 (V2.3.1) (2023-01): "Environmental Engineering (EE); Power supply
interface at the input of Information and Communication Technology (ICT) equipment; Part 3: Up
to 400 V Direct Current (DC)".
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] IEC 60050-601: "International Electrotechnical Vocabulary. Chapter 601: Generation,
transmission and distribution of electricity - General".
[i.2] EN 62368-1 Ed. 1.0: "Audio/Video, Information and Communication Technology Equipment -
Part 1: Safety requirements", (produced by CENELEC).
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8 ETSI TS 102 121 V1.4.1 (2025-02)
[i.3] IEC EN 60445: "Basic and safety principle for man-machine interface, marking and identification-
Identification of equipment terminals, conductor terminations, and conductors".
[i.4] ETSI TR 100 283: "Environmental Engineering (EE); Transient voltages at Interface "A" on
telecommunications direct current (DC) power distributions".
[i.5] 19 Pfl1: "Voltage limits for 60 V consumers in telecommunication installations of the Deutsche
Telekom".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
current-using equipment: either a further power supply system or a telecommunication equipment
NOTE: The telecommunication equipment with associated power supply may be considered as
telecommunication installation or telecommunication equipment.
disturbance: electromagnetic disturbance having components in the radio frequency range
immunity: ability of a device, equipment or system to perform without degradation in the presence of an
electromagnetic disturbance
power supply system: electrical equipment, which makes available energy obtained from a primary power source
(e.g. AC distribution) in a form suitable for the current-using equipment
radio interference: degradation of the reception of a wanted signal caused by radio frequency disturbance
supply voltage: voltage preferably obtained from the public distribution system or other primary electric power sources
Transfer Switch (TS): integrated automatic bypass switch used in the UPS, which can be fully static, fully
electromechanical or hybrid
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
DC Direct Current
EMC Electro Magnetic Compatibility
ERM Electromagnetic Radio spectrum Matters
HD Harmonization Document
ICT Information and Communication Technology
MOS Metal Oxide Semiconductor
PSI Power Supply Interface
SBS Systems Bypass Switch
SD Safe Disconnection
STS Static Transfer Switches (for the stand-alone static switches)
TS Transfer Switch
UPS Uninterruptible Power Supply
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9 ETSI TS 102 121 V1.4.1 (2025-02)
4 Types of power supply systems
4.0 Introduction
In telecommunication and datacom installations and equipment the designation of a power supply system refers to its
output.
In this sense there are DC and AC supplies. The operating modes described below are basic forms, which may be
developed into more complex arrangements.
4.1 DC supply
4.1.1 Mains operation
The current-using equipment is supplied with DC voltage obtained by a rectifier from the AC system (see figure 1).
The nominal voltage is a normative definition used to enable differentiating power interfaces as defined in
IEC 60050-601 [i.1].
Current using
equipment
Figure 1: Principle of mains operation
4.1.2 Battery operation
The current-using equipment is supplied from a battery. Both primary and secondary cells (Accumulators) can be used
as batteries. The Accumulator is disconnected from the current-using equipment for charging (see figure 2).
current
using
equipment
Figure 2: Principle of battery operation
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10 ETSI TS 102 121 V1.4.1 (2025-02)
4.1.3 Floating/Parallel operation
4.1.3.0 General principles
The current-using equipment is connected continuously to a rectifier and battery (see figure 3).
Current using
equipment
Figure 3: Principle of parallel operation
The current-using equipment is supplied in parallel operation; the rectifier being dimensioned in such a way that it can
cover the total power consumption of the current-using equipment and in addition supply an appropriate charging
current for the battery (see figure 3).
With this configuration the battery is continuously ready for operation in a fully charged condition. If the mains AC
voltage is outside of the specification (e.g. fails, reduction of voltage, high harmonics), the current-using equipment
continues to be supplied without interruption.
Parallel operation includes a very common charging mode known as floating mode and other charging modes such as
intermittent charge.
Floating charge is a charging mode where the self-discharge of the battery is compensated by maintaining a sufficient
voltage to the battery. The charging voltage can be varied due to temperature compensation.
Intermittent charge is a charging mode where the self-discharge of the battery is compensated by periodically raising the
voltage of rectifiers for short periods. Between these periods the rectifier voltage is left lower than it should be in
floating mode. The aim is to reduce plate corrosion and loss of water, as well as to reduce the risk of thermal runaway.
This may help to prolong the life span of batteries used in outdoor equipments or areas with high ambient temperature.
4.1.3.1 DC switch operation
4.1.3.1.0 Operation between rectifier and battery
The power requirement of th
...