The Association of Manufacturers and suppliers of Power Systems and ancillary equipment


Workgroup 2 Updates

Workgroup 2 – Grid Codes – Leader: John Ruddock

This is still a busy area for the TC. This is due to two drivers, firstly the change to G59 and G83 to standardise on RoCoF (Rate of Change of Frequency) grid failure detection, rather than VS (Vector Shift) protection. Secondly, the introduction of European electrical network grid codes to cover all aspects of grid operation and marketing.

Change to G59 and G83

The change to G59 and G83 is to standardise on RoCoF (Rate of Change of Frequency) grid failure detection, rather than permitting either RoCoF or VS (Vector Shift) protection. The reason for this is that on several occasions, it has been suspected that a transmission system fault that did not result in islanding, resulted in the inadvertent tripping of embedded generation plants by their LoM (Loss of Mains) protection. A definite event was recorded in GB on 22 May 2016 following a single transmission circuit fault. Further investigation of this event showed that a significant number of embedded generation plants had tripped as a result of the operation of VS protection. This event resulted in a loss of infeed power and a frequency excursion that was bigger than that which was anticipated.  This was due in simple terms due to the remaining grid generated power being insufficient for the demand. See Current Thinking of 2018 January 16th here [Distribution Code Public Consultation 6Report To the Authorityv 7ENA EREC G59 Issue 3 8].

As a result of the incident, an investigation took place and committee ‘GC0035 The effects of frequency changes during large disturbances and their impact on the total system for generators greater than 5MW.’ Was formed by National Grid.  The result was a programme of changing to RoCoF protection on all such installations, with a setting of 1 Hz/s with a definite time delay of 500 ms.

Attention then turned to smaller generators and committee ‘GC079 - The effects of frequency changes during large disturbances and their impact on the total system for generators Less than 5MW.’ was formed. This resulted in the recent issue of EREC G59-3-3 with a removal of VS protection (ie LoM by RoCoF only) and a setting of 1 Hz/s with a definite time delay of 500 ms.  This applied to new generators from 1st February 2018, and is not retrospective, but  the issue of retrospective changes to existing sets is being reviewed.

European Electrical Network Codes

The Regulation ‘Requirements for Generation Regulation’ (RfG) establishing a European network code on the requirement for grid connection of generators (RfG) entered into force on 17 May 2016. The provisions of RfG set out detailed rules relating to the connection of, principally, new power generating installations to national electricity networks. This has come from an EU decision to create network codes to govern grid operation and trading rules, which were previously agreed nationally. Quoting from the EU energy website:
“A fully functioning and interconnected internal energy market is crucial for maintaining security of energy supply, increasing competitiveness and ensuring that all consumers can purchase energy at affordable prices. Europe’s cross-border electricity networks are operated according to rules that govern the actions of operators and determine how access is given to users. In the past, these grid operation and trading rules were drawn up nationally. With increased interconnections between countries in the internal energy market, EU-wide rules have become increasingly necessary to effectively manage electricity flows. These rules, known as network codes or guidelines, are legally binding European Commission implementing Regulations. They govern all cross-border electricity market transactions and system operations alongside the EU Regulation 714/2009 on conditions for accessing the network for cross-border electricity exchanges.”

RfG will be effective on 17th May 2018, when the new codes must be in place, which is entailing a rush of work to complete the new codes and standards necessary. New plant has to comply from 17th May 2019.

AMPS have been working with the Energy Network Association, who are responsible for mainlining the distribution code website, and whose members are the owners and operators of the electricity distribution networks in the UK. Together with National Grid, who maintain Grid Codes.

There are three relevant workgroups. AMPS have representatives on each group.

GC0100 - EU Connection Codes GB Implementation - Mod 1

This modification (1/4) will set out within the Distribution Code and Grid Code the following compliance obligations in the EU Connection Codes:

 

  1. Scope and applicability of the RfG, DCC and HVDC requirements for GB users
  2. Set the x4 Type (A-D) MW banding levels for GB, as required in RfG
  3. Set the GB Fast Fault Current Injection parameters, as set out in RfG
  4. Set the GB Fault Ride Through requirements, as set out in RfG and HVD

 

 

GC0101 - EU Connection Codes GB Implementation - Mod 2

This modification (2/4) will set out within the Distribution Code and Grid Code the following compliance obligations in the EU Connection Codes:

  1. Set the Voltage & Reactive requirement in GB, as required in RfG and HVDC
  2. Set the Frequency requirements in GB, as required in RfG and HVDC

GC0102 - EU Connection Codes GB Implementation - Mod 3

This modification (3/4) will set out within the Distribution Code and Grid Code the following compliance obligations in the EU Connection Codes:

  1. Set the System Management parameters, as set out in RfG and HVDC
  2. Set the Compliance requirements, as set out in RfG, DCC and HVDC

The banding levels are proposed as:

RfG Type (A-D) MW banding levels for GB
  Type A Type B  Type C Type D 
Unit Power* 800 W to 1 MW to 10MW 50MW+
1 MW 10 MW 50 MW

 

*Nameplate rating of generator, not site total power.

Northern Ireland is separate, as it is part of the island of Ireland ‘synchronous area’.

The reason for banding is that the technical requirements for sets, particularly electrical protection, get increasingly severe as the set kW increases.

Despite this being issued as a Regulation, which has effect equally across the EU, each Member State can vary the banding points and can set different technical requirements. So much for harmonisation!

A new grid connection engineering recommendation has been issued for consultation which will apply to new sets after May 2019. G59 and G83 will continue to apply to existing sets, as this new directive is not retrospective.

The new documents are:

Distribution Code report (G99 Consultation [9])
G98 in place of G83, for new sets (ENA Engineering Recommendation G98 Draft For Consultation [10])
G99 in place of G59, for new sets (ENA Engineering Recommendation G99 [11])

A ‘final’ version of G99 is being drafted and will be circulated to members  when it is available.

Some amendments may follow. Testing and certification are still being debated, for example.

To complicate matters even further, CENELEC are proposing new European Standards ‘prEN 50549 Requirements for generating plants to be connected in parallel with distribution networks’. These are unlikely to be in place before 2019, and thus will probably replace G98 and G99 at a later date!

GC0095: GB implementation workgroup for Transmission System Operation Guideline (TSOG) European Network Code

The only relevance to AMPS is that control and monitoring of generation is being considered, and it will be retrospective.