G99 – NEW REGULATIONS IN THE UK

G99 NEW REGULATIONS COVERING THE FOLLOWING DIFFERENT POWER GENERATOR TYPES IN THE UK

Type A Generators (Generators up to 1MW)

Type A generation systems will be very similar in design and application to the general requirements defined in G59, although some of these requirements have now been formalised in slightly more detail. The following list details some of the main requirements

  • Performance & Control – Generators will now need an input signal from the DNO to stop generation, which must occur within 5s of signal receipt.
  • Frequency Response – Generators must continue to operate for specified times, following a network frequency deviation
  • Network Falling Frequency – Generator must retain constant power output down to 49.5Hz, after this point a linear drop off can occur of 5% to 47Hz
  • Frequency Response (LFSM-O) – Generators should have the ability to reduce their power output in response to a rising frequency
  • Voltage Limits and Control – should be able to provide constant power for a DNO network voltage deviation of ±10%
  • Reactive Power Control – Generators should be able to operate between 0.95 lag and 0.95 lead PF
  • Fast Fault Current Injection

 

Type B Generators (Generators from 1MW to  <10MW

Type B generation systems will be broadly similar in design and application to the general requirements defined in G59. The big changes are that the manufacturers design and specification will need to improve, additional power system studies will be required to demonstrate compliance and there will SCADA interfaces to the DNO.

  • Performance & Control – Generators will now need an input signal from the DNO that that can reduce their power from 100% to 0%
  • Frequency Response – Generators must continue to operate for specified times, following a network frequency deviation
  • Network Falling Frequency – Generator must retain constant power output down to 49.5Hz, after this point a linear drop off can occur of 5% to 47Hz
  • Frequency Response (LFSM-O) – Generators should have the ability to reduce their power output in response to a rising frequency
  • Fault Ride Through – Generators must remain connected and stable for twospecific fault scenarios on the DNO network
  • Voltage Limits and Control – should be able to provide constant power for a DNO network voltage deviation of ±10% and synchronous generators must have a flexible excitation system
  • Reactive Power Control – Generators should be able to operate between 0.95 lag and 0.95 lead PF at registered capacity and operate for a wider range below full capacity
  • Fast Fault Current Injection – Generators must be able to inject current into the system during fault conditions to help stabilise grid
  • Operational Monitoring – DNO will be require installation of local SCADA / Telecontrol equipment to monitor performance

 

Type C and D Generators (Generators >10MW or Connected at >110kV)

Type C & D generation systems will see a large change and face several more significant design challenges. This will result in more power system studies being required to demonstrate compliance, complex controllers and interfaces to the DNO and an increased need for reactive power compensation equipment.

  • Performance & Control – Generators will need full active control by the DNO
  • Frequency Response – Generators must continue to operate for specified times, following a network frequency deviation
  • Network Falling Frequency – Generator must retain constant power output down to 49.5Hz, after this point a linear drop off can occur of 5% to 47Hz
  • Frequency Response (LFSM-O) – Generators should have the ability to reduce their power output in response to a rising frequency
  • Frequency Response (LFSM-U) – Generators should have the ability to increase their power output in response to a falling frequency
  • Frequency Sensitive Mode – Generators will require a full frequency-based control system
  • Fault Ride Through – Generators must remain connected and stable for fourspecific fault scenarios on the DNO network
  • Voltage Limits and Control – should be able to provide constant power for a DNO network voltage deviation of ±10% and synchronous generators must have a flexible excitation system
  • Reactive Power Control – Generators should be able to operate between 0.95 lag and 0.95 lead PF at registered capacity for all voltage between 95% and 105% and operate for a much wider range below full capacity
  • Fast Fault Current Injection – Generators must be able to inject current into the system during fault conditions to help stabilise grid
  • Black Start Capability – no specific requirements, but sites that have this capability should notify National Grid
  • Operational Monitoring – Full real-time / time stamped data exchange with the DNO.

 

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