DC 0079 - Frequency Changes during Large Disturbances and their effect on the total system - Phase 2

Status

Proposer

The Distribution Code Review Panel - www.dcode@energynetworks.org
020 7706 5105

Summary

It is recommended that the Distribution Planning Code and EREC G59 should be changed to ensure that all existing embedded generators make changes to comply with the following:

1. That where rate of change of frequency (RoCoF) protection relays are used, as part of Loss of Mains protection, the applied setting should be 1Hzs-1 with a definite time delay of 500ms.
2. That vector shift protection technique should be removed where it is in use as Loss of Mains protection.
3. That existing Loss of Mains protection settings for type-tested generators need not be changed.
4. Any existing over-frequency setting relays still set at 50.5Hz should if possible be reset to 52.0Hz.

Impact

Consultation

The Distribution Code public consultation sought views from industry stakeholders on the modification to both the ‘DCode’ and Engineering Recommendation (EREC) G59 and EREC G83. It was published on the 31 January 2018 with a deadline for responses by 23 February 2018.

DCRP/18/04/PC Consultation Pack

Following the meeting of the Distribution Code Review Panel (the Panel) held on 7th February 2019, it was agreed that the Report to Authority would be amended with minor changes before submission of the Report to Authority for approval. The Panel agreed to this submission and that the modification proposals better facilitate the objectives of the Distribution Code.

Subject to the agreement of the Authority the modification should be implemented from the date the revised Distribution Code is published. This date is proposed as 01 May 2019.

DC0079 Retrospective Action Report to Authority

DC0079 Retrospective Action Report to Authority Annexes

Authority Decision

The purpose of this report is to assist the Authority in its decision to implement the proposed modifications to the Distribution Code Engineering Recommendations G59 and G83. The proposed modifications were subject to industry consultation in August 2017 and February 2018. During the August Consultation no response was received from manufacturers of type tested plant. As a result a second consultation was undertaken in February 2018 and one response was received from a type tested plant manufacturer. The manufacturer did not object to the proposal but proposed a delay in the implementation date.

It is recommended that modifications be made to Distribution Code and Engineering Recommendations G59 and G83 to mandate that all type tested generators commissioned on or after July 2018, demonstrate stability for appropriate RoCoF and vector shift disturbances. The report recommends:

a) That the rate of change of frequency (RoCoF) criterion used for Loss of Mains protection must be 1 Hzs per second with a definite time delay of 500ms

b) That vector shift protection technique should not be used as Loss of Mains protection for type tested generators and that generation must not trip for vector shifts of up to 50º

c) That type tested generation includes stability tests to prove immunity to RoCoF and vector shift less than the above criteria.

Report

Report Annexes

Decision of Authority - 3 May 2018

The Authority has approved this modification. Full details of Ofgem's decision can be found in their decision letter which can be found here. The resultant modifications to the Distribution Code and Engineering Recommendation G59-3/3 will become effective from 1 February 2018.