TC 99 - Insulation co-ordination and system engineering of high voltage electrical power installations above 1,0 kV AC and 1,5 kV DC

IEC 61936-2:2023 provides, in a convenient form, requirements for the design and the erection of DC installations in systems with nominal voltages above 1,5 kV DC, so as to provide safety and proper functioning for the use intended.
For the purpose of interpreting this document, a DC installation is considered to be one of the following:
a) A converter station or DC switching station;
b) one (or more) DC generating or storage unit(s), such as solar farms or battery storage units, located on a single site, the DC installation includes DC equipment and cables with all associated power electronics, controlgear, switchgear and all electrical auxiliary systems. Connections between DC generating or storage units located on different sites are excluded;
c) DC installation erected on offshore facilities for the purpose of generation, transmission, distribution and/or storage of electricity; or
d) DC transition station (between overhead lines and underground cable or between different sections of underground cables).
This International Standard does not apply to the design and erection of any of the following:
- overhead and underground lines between separate installations;
- electric railways;
- mining equipment and installations;
i- installations on ships according to IEC 60092 series and offshore units according to IEC 61892 series, which are used in the offshore petroleum industry for drilling, processing and storage purposes;
- electrostatic equipment (e.g. electrostatic precipitators, spray-painting units);
- test sites;
- medical equipment, e.g. medical X-ray equipment;
- valve hall or converter hall.
This document does not apply to the requirements for carrying out live working on electrical installations.
This document does not apply to the design of factory-built, type-tested thyristor valves, VSC valves and switchgear for which separate IEC standards exist.
This first edition cancels and replaces the IEC TS 61936-2 published in 2015. This edition constitutes a technical revision.
See the foreword of this edition for the list of significant technical changes with respect to the previous edition.

IEC 60071-2:2023 constitutes application guidelines and deals with the selection of insulation levels of equipment or installations for three-phase AC systems. Its aim is to give guidance for the determination of the rated withstand voltages for ranges I and II of IEC 60071‑1 and to justify the association of these rated values with the standardized highest voltages for equipment. This association is for insulation co-ordination purposes only. The requirements for human safety are not covered by this document. This document covers three-phase AC systems with nominal voltages above 1 kV, phase-to-earth, phase-to-phase and longitudinal insulation. It has the status of a horizontal standard in accordance with IEC Guide 108. This edition includes the following significant technical changes with respect to the previous edition:
a) Clause 4 Concepts governing the insulation co-ordination has been added.
b) Subclause 5.3 has been revised, and Subclause 5.4 Detailed simulation has been added because it is widely applied in the recent practices of insulation coordination.
c) Special considerations for cable line and GIL/GIB have been added in Clause 9.
d) Annex K (informative) Application of line shunt reactor to limitation of TOV and SFO in high voltage overhead transmission lines has been added.
e) Annex L (informative) Calculation of lightning stroke rate and lightning outage rate has been added.

IEC TS 61936-0:2023 provides principles to ensure the coherence amongst HV publications to be observed necessary for the coordination of the design, selection of equipment, operation, and maintenance activities for erection of electrical HV installations to ensure the safety of such systems.
In the context of this document, "safety" relates to the safety of persons, domestic animals, livestock and property.
This Technical Specification is intended for use by technical committees in the preparation of standards with safety aspects which can be a part of an electrical high voltage installation

IEC 60071-11:2022 applies to high-voltage direct current (HVDC) systems. It specifies the principles on the procedures for the determination of the specified withstand voltages, creepage distance and air clearances for the equipment and the installations of these systems.
This document gives the insulation co-ordination principles related to line commutated converter (LCC) and voltage sourced converters (VSC) HVDC systems. The main principles of this document also apply to other special converter configurations of LCC, such as the capacitor commutated converter (CCC) as well as the controlled series compensated converter (CSCC), etc.
This document applies to insulation co-ordination of equipment connected between the converter AC bus (including the AC harmonic filters, the converter transformer, the circuit breakers) and the DC line side. The line and cable terminations in so far as they influence the insulation co-ordination of converter station equipment are also covered.
This document applies only for HVDC applications in power systems and not for industrial conversion equipment. Principles and guidance given are for insulation co-ordination purposes only. The requirements for human safety are not covered by this document.
This international standard replaces, in conjunction with IEC 60071-12, IEC 60071-5 published in 2014.
This edition includes the following significant technical changes with respect to IEC 60071‑5:2014:
This standard applies to both LCC and VSC HVDC systems whereas IEC 60071-5 only dealt with LCC HVDC system;
Annex C (normative) gives the recommended specified withstand voltage (LI and SI);
Annex C (normative) gives the minimum air clearances;
Annex E shows the correlation of clauses between this standard and IEC 60071-5:2014.
The contents of the corrigendum of November 2023 have been included in this copy.

IEC 60071-12:2022 applies guidelines on the procedures for insulation co-ordination of line commutated converter (LCC) stations for high-voltage direct current (HVDC) project, whose aim is evaluating the overvoltage stresses on the converter station equipment subjected to combined DC, AC power frequency, harmonic and impulse voltages, and determining the specified withstand voltages for equipment.
This document deals only with metal-oxide surge arresters, without gaps, which are used in modern HVDC converter stations. The criteria for determining the protective levels of series and/or parallel combinations of surge arresters used to ensure optimal protection are also presented. Typical arrester protection schemes and stresses of arresters are presented.
Annex A contains examples of insulation co-ordination for LCC HVDC converters which support the concepts described in the main text, and the basic analytical techniques used.

IEC 61936-1:2021 provides requirements for the design and the erection of electrical power installations in systems with nominal voltages exceeding 1 kV AC and nominal frequency up to and including 60 Hz, so as to provide safety and proper functioning for the use intended.
This document does not apply to the design and erection of any of the following:
– overhead and underground lines between separate electrical power installations;
– electrified railway tracks and rolling stock;
– mining equipment and installations;
– fluorescent lamp installations;
– installations on ships according to IEC 60092 (all parts) and offshore units according to IEC 61892 (all parts), which are used in the offshore petroleum industry for drilling, processing and storage purposes;
– electrostatic equipment (e.g. electrostatic precipitators, spray-painting units);
– test sites;
– medical equipment, e.g. medical X-ray equipment.
This document does not apply to the design of prefabricated, type-tested switchgear and high voltage/low voltage prefabricated substation, for which separate IEC standards exist.
This edition includes the following significant technical changes with respect to the previous edition:  
introduction has been rewritten to reflect the status when this document is produced;
the scope has been improved to clarify the application of this document;
missing and obsolete terms and definitions have been updated including improvement of existing terms;
Table 1 has been updated where agreements between supplier and user are needed;
requirements of electromagnetic compatibility have been clarified;
insulation coordination clause (Clause 5) has improved wording for better clarity and the technical content has an updated coordination to the latest versions of the insulation coordination standards;
wording regarding electrical equipment has been improved and made clearer;
subclause for fuses has been improved and reworded;
requirements have been added for labelling when multiple sources are required to be disconnected;
missing requirements for GIS have been reintroduced;
subclause regarding ventilation (HVAC) has been improved;
figures in Clause 7 have been updated and moved to the corresponding subclause;
requirements for transformer installations have been improved including adjustment of editorial typing-errors;
clause on protection, automation and auxiliary systems has been restructured and improved;
protection against lightning strokes has been extended;
clarification of content due to the distinction between erection (and providing electrical safety for the intended use of the electrical power installation) and subsequent activities such as maintenance and repair with safe working procedures;
where no provincial, national or regional regulations are available for safe working procedures, an informative guideline is provided in Annex F. This replaces the former parts of Figure 3 in Clause 7.

IEC 61936-1:2010 provides common rules for the design and the erection of electrical power installations in systems with nominal voltages above 1 kV a.c. and nominal frequency up to and including 60 Hz, so as to provide safety and proper functioning for the use intended. For the purpose of interpreting this standard, an electrical power installation is considered to be one of the following:
a) Substation, including substation for railway power supply;
b) Electrical installations on mast, pole and tower; Switchgear and/or transformers located outside a closed electrical operating area;
c) One (or more) power station(s) located on a single site. The installation includes generators and transformers with all associated switchgear and all electrical auxiliary systems. Connections between generating stations located on different sites are excluded;
d) The electrical system of a factory, industrial plant or other industrial, agricultural, commercial or public premises. The electrical power installation includes, among others, the following equipment: rotating electrical machines; switchgear; transformers and reactors; converters; cables; wiring systems; batteries; capacitors; earthing systems; buildings and fences which are part of a closed electrical operating area; associated protection, control and auxiliary systems; large air core reactor. NOTE: In general, a standard for an item of equipment takes precedence over this standard. This standard does not apply to the design and erection of any of the following:
- overhead and underground lines between separate installations;
- electric railways;
- mining equipment and installations;
- fluorescent lamp installations;
- installations on ships and off-shore installations;
- electrostatic equipment (e.g. electrostatic precipitators, spray-painting units);
- test sites;
- medical equipment, e.g. medical X-ray equipment.
This standard does not apply to the design of factory-built, type-tested switchgear for which separate IEC standards exist. This standard does not apply to the requirements for carrying out live working on electrical installations. This second edition cancels and replaces the first edition, published in 2002. It constitutes a technical revision. The main changes with respect to the previous edition are listed below:
- new table of references for additional agreements between manufacturer/contractor/planer and user/orderer/owner (4.1.2);
- addition of minimum clearances in air not standardized by IEC but based on current practice in some countries (Annex A);
- deletion of nominal voltages (Table 1, Table 2, Clause 5);
- addition of regulations for fuses (6.2.15);
- simplification of regulations for escape routes (7.5.4);
- deletion of special regulations for operating aisles (7.5.4);
- modification of clearances for fire protection (Table 3);
- modification of safety criteria for earthing systems (10.2.1);
- modified curves of permissibly touch voltages (Figure 12, Annex B);
- deletion of numbering of subclauses without headlines;
- change of "should" to "shall" in many cases or change of subclauses with "should" to a note. The contents of the corrigendum of March 2011 have been included in this copy.

Provides, in a convenient form, common rules for the design and the erection of electrical power installations in systems with nominal voltages above 1 kV a.c. and nominal frequency up to and including 60 Hz, so as to provide safety and proper functioning for the use intended. This standard applies to all high voltage installations except as stated otherwise in some cases specified in other parts of IEC 61936. This standard does not apply to the design and erection of any of the following: - overhead and underground lines between separate installations; - electric railways (but not the substation feeding a railway system); - mining equipment and installations ; - fluorescent lamp installations; - installations on ships and off-shore installations; - electrostatic equipment; - test sites; - medical equipment, e.g. medical X-ray equipment. This standard does not apply to the design of factory-built, type-tested switchgear for which separate IEC standards exist. This standard does not apply to the requirements for carrying out live working on electrical installations. For the purpose of interpreting this standard, an electrical power installation is considered to be one of the following. a) Substation A closed electrical operating area in a transmission or distribution network. When switchgear and/or transformers are located outside a closed electrical operating area, this is also taken to be an installation. b) One (or more) power station(s) located on a single site The installation includes generators and transformers with all associated switchgear and all electrical auxiliary systems. Connections between generating stations located on different sites are excluded. c) The electrical system of a factory, industrial plant or other industrial, agricultural, commercial or public premises Connections between closed electrical areas (including substations), located on the same site, are taken to be part of the installation, except where such connections form part of a transmission or distribution network. The electrical power installation includes, among others, the following equipment: - rotating electrical machines; - switchgear; - transformers and reactors; - converters; - cables; - lines; - wiring systems; - batteries; - capacitors; - earthing systems; - buildings and fences which are part of a closed electrical operating area; - associated protection, control and auxiliary systems ; - large air type core reactor. NOTE In general, a standard for an item of equipment takes precedence over this standard.

IEC TS 61936-2:2015(E) provides, in a convenient form, common rules for the design and the erection of electrical power installations in systems with nominal voltages above 1,5 kV d.c., so as to provide safety and proper functioning for the use intended.

IEC 60071-5:2014 provides guidance on the procedures for insulation co-ordination of high-voltage direct current (HVDC) converter stations, without prescribing standardized insulation levels. This standard applies only for HVDC applications in high-voltage a.c. power systems and not for industrial conversion equipment. Principles and guidance given are for insulation co-ordination purposes only. The requirements for human safety are not covered by this standard. This International Standard cancels and replaces IEC TS 60071-5 published in 2002. On the basis of technical experience gained since the Technical Specification was published, sufficient consensus has emerged for transformation of the Technical Specification into an International Standard. The technical content is essentially the same as that contained in the Technical Specification with amendments mainly for user convenience. The structure of the document has been changed to allow division and subdivision into complete integral parts to facilitate comprehension and ease of referencing. In addition to the high level revisions above, the following main technical changes have been made with respect to the previous edition:
- arresters have been added to several locations to reflect some recent 800 kV HVDC scheme practice, along with their justifications, expected voltages, overvoltages and arrester stresses in service;
- significant changes have been made in Clause 8 - all subclauses on the characteristics, schemes, stresses and specification of arresters have been consolidated into a single entity, Clause 8;
- the implications of a smoothing reactor and of a neutral blocking filter located on the neutral bus (as on some recent 800 kV schemes), on coordination of arresters connected to the neutral end have been added;
- possible use of sacrificial arresters on the neutral bus is introduced to cater for excessive arrester energy in the rather unlikely event of a particular rare fault;
- all subclauses dealing with study tools and modelling details have been consolidated into Clause 10;
- creepage distances and clearances have been consolidated into Clauses 11 and 12, respectively, with more details added.

Provides guidance on the procedures for insulation co-ordination of high-voltage direct current (HVDC) converter stations, without prescribing standardized insulation levels. Applies only for HVDC applications in high-voltage a.c. power systems and not for industrial conversion equipment. Principles and guidance given are for insulation co-ordination purposes only. The requirements for human safety are not covered.