IEC TS 62786-1:2023

Distributed energy resources connection with the grid - Part 1: General requirements

IEC TS 62786-1:2023, which is a Technical Specification, provides principles and general technical requirements for distributed energy resources (DER) connected to an electric power network (in the following: the "network"). It applies to the planning, design, operation and connection of DER to networks. It includes general requirements, connection scheme, choice of switchgear, normal operating range, immunity to disturbances, active power response to frequency deviations, reactive power response to voltage changes, EMC and power quality, interface protection, connection and start to generate electrical power, active power management, monitoring, control and communication, and conformance tests.
It is supplemented by additional parts of IEC 62786 series, covering specific aspects.
This document specifies interface and interoperability requirements for connection of DER to a network operating at a nominal frequency of 50 Hz or 60 Hz. These requirements are intended for application at the point of connection (POC) of the DER to the grid. In some situations, the requirements can be the applied at the AC terminals of the generator. Additional parts of IEC 62786 provide more specific requirements.
DER include distributed generation and electrical energy storage in the form of synchronous generators, asynchronous generators, power converters, etc., connected to the medium voltage (MV) or low voltage (LV) network.

Raccordement au réseau des ressources énergétiques décentralisées – Exigences générales

General Information

• Status: Published
• Publication Date: 27-Nov-2023
• ICS: 29.240.01 - Power transmission and distribution networks in general
• Technical Committee: TC 8 - System aspects of electrical energy supply
• Drafting Committee: JWG 10 - TC 8/JWG 10
• Current Stage: PPUB - Publication issued
• Start Date: 20-Oct-2023
• Completion Date: 28-Nov-2023

Relations

• Replaces: IEC TS 62786:2017 - Distributed energy resources connection with the grid
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TS 62786-1 ®
Edition 1.0 2023-11
TECHNICAL
SPECIFICATION
colour
inside
Distributed energy resources connection with the grid –
Part 1: General requirements
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IEC TS 62786-1 ®
Edition 1.0 2023-11
TECHNICAL
SPECIFICATION
colour
inside
Distributed energy resources connection with the grid –

Part 1: General requirements
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.240.01  ISBN 978-2-8322-7927-4

– 2 – IEC TS 62786-1:2023 © IEC 2023
CONTENTS
FOREWORD . 5
1 Scope and object . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
4 Requirements for generating plants . 14
4.1 General . 14
4.2 Connection scheme . 14
4.3 Choice of switchgear . 14
4.3.1 General . 14
4.3.2 Interface switch . 15
4.4 Normal operating range . 15
4.4.1 General . 15
4.4.2 Operating frequency range . 15
4.4.3 Operating voltage range . 15
4.5 Immunity to disturbances . 16
4.5.1 General . 16
4.5.2 Rate of change of frequency (ROCOF) immunity . 16
4.5.3 Undervoltage ride through (UVRT) requirements . 18
4.5.4 Overvoltage ride through (OVRT) requirements . 19
4.5.5 Rapid phase angle change immunity . 20
4.6 Active power response to frequency deviation . 21
4.7 Power response to voltage changes . 21
4.7.1 General . 21
4.7.2 Voltage support by reactive power . 21
4.7.3 Reactive power control modes . 22
4.7.4 Voltage related active power control . 22
4.7.5 Voltage related reactive power response . 23
4.7.6 Additional reactive current requirements on generating plants . 24
4.8 EMC and power quality . 29
4.8.1 General . 29
4.8.2 Direct current (DC) injection . 29
4.9 Interface protection . 29
4.9.1 General . 29
4.9.2 Requirements on voltage and frequency protection . 31
4.9.3 Means to detect islanding situation . 32
4.9.4 Digital input to the interface protection . 33
4.10 Connection and starting to generate electrical power . 33
4.10.1 General . 33
4.10.2 Connection of synchronous-type generators . 33
4.10.3 Autoreclose of distribution lines . 33
4.11 Ceasing and reduction of active power on set point. 33
4.12 Remote information exchange . 34
4.12.1 General . 34
4.12.2 Monitoring and control . 34
4.12.3 Communication . 34

4.13 Requirements regarding single fault tolerance of interface protection system
and interface switch . 35
5 Conformance tests . 35
Annex A (normative) Operating frequency range . 36
Annex B (normative) Operating voltage range . 37
Annex C (normative) Undervoltage ride through capability of DER . 38
Annex D (normative) Overvoltage ride through parameters . 39
Annex E (informative) Reactive power control behaviour of DC to AC power
conversion equipment used in DER in conjunction with synchronous generators . 40
E.1 Background. 40
E.2 Power system with DER configuration . 40
E.3 Reactive power directions with leading/lagging of current phase angle to
voltage phase . 40
E.4 Reactive power control of synchronous generators . 41
E.5 Reactive power control of power conversion equipment . 42
E.6 Reactive power effect as reactive and capacitive load . 42
E.7 Conclusion . 43
Annex F (normative) Summary of power thresholds to be defined by individual
countries . 44
Bibliography . 45

Figure 1 – Example of electricity generating plant connected to a network (schematic
view of switches) . 12
Figure 2 – Under frequency ride through capability requirements of DER . 17
Figure 3 – Over frequency ride through capability requirements of DER . 17
Figure 4 – Instantaneous frequency change ride through requirement of DER . 18
Figure 5 – Under voltage ride through capability requirements of DER . 18
Figure 6 – Power recovering requirements for UVRT operation of DER (example) . 19
Figure 7 – Over voltage ride through capability . 20
Figure 8 – Example of instantaneous voltage phase angle change during UVRT . 20
Figure 9 – Typical power-frequency response curve. 21
Figure 10 – Typical volt-watt response curve . 23
Figure 11 – Typical volt-var response curve . 24
Figure 12 – Principle of voltage support during faults and voltage steps (DBL: lower
deadband limit; DBH: higher deadband limit) . 27
Figure 13 – Accuracy requirement for additional reactive current in positive and
negative sequence (LTR: limit of tolerance range) . 28
Figure 14 – Operation of protection functions . 32
Figure E.1 – Configuration schematic of a power system . 40
Figure E.2 – Reactive and active power control image of syncronous generators and DER . 42

Table 1 – Operating frequency requirements of DER . 15
Table 2 – Operating voltage requirements of DER . 16
Table 3 – Volt watt mode parameters (example) . 22
Table 4 – volt-var response set-point values for reference voltages (example) . 23
Table 5 – Interface protection functions . 30

– 4 – IEC TS 62786-1:2023 © IEC 2023
Table A.1 – Continuous operating frequency range . 36
Table A.2 – Limited operating frequency range . 36
Table B.1 – Continuous operating POC voltage range . 37
Table B.2 – Limited operating voltage range . 37
Table C.1 – UVRT capability of DER with an interface to the grid based on a
synchronous generator . 38
Table C.2 – UVRT capability of DER with an interface to the grid based on non-

synchronous generators (eg. converters, DFIG, etc.) . 38
Table D.1 – OVRT capability of DER . 39
Table E.1 – Operation and behaviours of synchronous generators, dispersed loads and
DER 43
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