IEC TS 62786-41:2023

Distributed energy resources connection with the grid - Part 41: Requirements for frequency measurement used to control distributed energy resources (DER) and loads

IEC TS 62786-41:2023 (E), which is a Technical Specification, defines minimum requirements for frequency and rate of change of frequency measurements used to control distributed energy resources (DER) and loads connected to electrical power networks.
This document specifies the characteristics of frequency and rate of change of frequency measurements to evaluate their performances. It describes the main use cases of frequency and rate of change of frequency measurements, with associated level of performances. It describes the principle of functional tests to evaluate the specified characteristics and defines the influencing factors that affect these performances, under steady state or dynamic conditions.
This document defines the functional requirements applicable to frequency and rate of change of frequency measurements which can be inside or outside the DER or loads. In the case of DER, this document provides requirements additional to those which are defined in the other parts of IEC 62786 or standards produced by the relevant IEC technical committees (e.g. TC 82 for photovoltaic systems, TC 88 for wind systems, TC 120 for electrical energy storage systems (EES)).
This document is applicable to DER and loads regardless of the voltage level of the point of connection to the grid.
This document does not specify hardware, software or a method for frequency or rate of change of frequency measurement. It does not specify tests linked to environmental conditions associated with hardware devices (climatic, electromagnetic disturbances above 3 kHz, mechanical stress, etc.).
Frequency and rate of change of frequency measurements associated with time stamping are not in the scope of this document. These measurements are already covered by IEC 60255 118 1.
Frequency and rate of change of frequency measurements associated with protection functions or protection relays are not in the scope of this document. These requirements are already covered by IEC 60255-181.

General Information

• Status: Published
• Publication Date: 16-Jul-2023
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 8 - System aspects of electrical energy supply
• Drafting Committee: JWG 12 - TC 8/JWG 12
• Current Stage: PPUB - Publication issued
• Start Date: 17-Jul-2023
• Completion Date: 17-Jul-2023

Standards Content (Sample)

IEC TS 62786-41 ®
Edition 1.0 2023-07
TECHNICAL
SPECIFICATION
colour
inside
Distributed energy resources connection with the grid –
Part 41: Requirements for frequency measurement used to control distributed
energy resources (DER) and loads

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IEC TS 62786-41 ®
Edition 1.0 2023-07
TECHNICAL
SPECIFICATION
colour
inside
Distributed energy resources connection with the grid –

Part 41: Requirements for frequency measurement used to control distributed

energy resources (DER) and loads

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 91.140.50  ISBN 978-2-8322-7225-1

– 2 – IEC TS 62786-41:2023 © IEC 2023
CONTENTS
FOREWORD . 7
1 Scope . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Performance description . 14
4.1 General . 14
4.2 Input energizing quantities . 14
4.3 Delay time . 15
4.3.1 Description . 15
4.3.2 Reporting of delay time declaration . 15
4.4 Effective resolution and accuracy . 15
4.4.1 Description . 15
4.4.2 Effective measurement resolution . 16
4.4.3 Reporting of the frequency and ROCOF accuracy . 16
4.5 Measuring range, operating range, and rejection of interfering signals . 16
4.6 Timing characteristics . 19
4.6.1 Reporting rate. 19
4.6.2 Settling time . 19
5 Summary of typical performances associated with different use cases . 20
6 Description of functional test principles . 22
6.1 General . 22
6.2 Test reference conditions . 24
6.3 Verification of delay time for frequency and ROCOF measurement . 24
6.3.1 Test description . 24
6.3.2 Example determination of delay time . 25
6.4 Verification of effective resolution for frequency and ROCOF measurement . 27
6.4.1 Test description . 27
6.4.2 Example determination of effective resolution . 29
6.5 Verification of measurement and operating ranges . 29
6.5.1 Verification of measurement and operating ranges under steady state
conditions . 29
6.5.2 Measuring and operating ranges under dynamic conditions . 31
6.5.3 Verification of rejection of interfering interharmonics. 33
6.5.4 Verification of rejection of harmonics . 35
6.6 Verification of settling time . 38
6.6.1 Test description . 38
6.6.2 Verification of settling time for frequency measurement . 39
6.6.3 Example of verification of frequency settling time . 39
6.6.4 Verification of settling time for ROCOF measurement . 40
6.6.5 Example of verification of ROCOF settling time . 40
6.7 Type test report . 41
Annex A (informative) Measurement classes . 43
Annex B (informative) Description of frequency or ROCOF measurement use cases . 44
B.1 Use case "PLL in photovoltaic power generating systems" . 44
B.1.1 Technical background of the use case . 44
B.1.2 Resulting requirements for measurement . 45

B.2 Use case "Primary reserve" . 46
B.2.1 Technical background of the use case . 46
B.2.2 Resulting requirements for measurement . 46
B.2.3 Example of "frequency-watt" function in photovoltaic power generating
systems . 47
B.3 Use case "Secondary reserve – frequency measurement used for centralized
control" . 48
B.3.1 Technical background of the use case . 48
B.3.2 Resulting requirements for measurement . 48
B.4 Use case "Fast frequency-active power proportional controller with dead
band" . 49
B.4.1 Technical background of the use case . 49
B.4.2 Resulting requirements for measurement . 50
B.5 Use case "Fast frequency response" . 51
B.5.1 Technical background of the use case . 51
B.5.2 Resulting requirements for measurement . 51
B.6 Use case "Synthetic inertia" . 51
B.6.1 Technical background of the use case . 51
B.6.2 Resulting requirements for measurement . 52
B.7 Use case "Passive anti-islanding detection" . 52
B.7.1 Technical background of the use case . 52
B.7.2 Resulting requirements for measurement . 53
B.8 Use case "Active anti-islanding detection" . 54
B.8.1 Technical background of the use case . 54
B.8.2 Resulting requirements for measurement . 54
B.9 Use case "ROCOF measurement used for centralized control" . 55
B.9.1 Technical background of the use case . 55
B.9.2 Resulting requirements for measurement . 55
B.10 Use case "Load control with active power management" . 55
B.10.1 Technical background of the use case . 55
B.10.2 Resulting requirements for measurement . 55
B.11 Use case "Self-dispatchable loads" (microgrid applications) . 56
B.11.1 Technical background of the use case . 56
B.11.2 Resulting requirements for measurement . 56
B.12 Use case "Under-frequency load shedding" (UFLS) . 57
B.12.1 Technical background of the use case . 57
B.12.2 Resulting requirements for measurement . 57
Annex C (informative) Summary of requirements expressed in standards and grid
codes related to frequency and ROCOF measurements . 58
Annex D (informative) Maximum ROCOF to be considered on power systems in case
of incidents . 65
D.1 General . 65
D.2 UK . 65
D.3 European continent . 65
D.4 Islands . 65
Annex E (informative) Frequency and rotating vectors . 66
Annex F (informative) Synthetizing input signals with sudden frequency change

without discontinuity in voltage waveform. 68
Annex G (informative) Step test equivalent time sampling technique . 71
G.1 Overview. 71

– 4 – IEC TS 62786-41:2023 © IEC 2023
G.2 Equivalent time sampling . 72
G.3 Determination of settling time using instrument errors . 73
Annex H (informative) Voltage and phase angle changes during transmission line
faults related to the type of transformer connection . 75
H.1 Overview. 75
H.2 Power line short circuit fault and protection .
...