Latest updates to G59 regulation (effective 1st Feb 2018)

January 29th, 2018

The Association of Manufacturers and suppliers of Power Systems and ancillary equipment (AMPS) has released information on the latest updates to the UK Grid Connection Requirements.

This affects all Non-Type Tested Generating Plants from 50Kw and above commissioned after 31st January 2018.

The Distribution Code Review Panel has advised of the publication of a revised Distribution Code (V29) and a revised Engineering Recommendation G59/3-3. These take effect for all new Non-Type Tested Generating Plants commissioned from 1st February 2018.

Please note that it is assumed that ‘commissioning’ is the date of completion testing of the generators loss of mains protection and first synchronisation to the network. This may not be the same date as the complete plant is ‘commissioned’. There is no definition given in the documentation.

It has previously been suspected that a transmission system fault that did not result in islanding resulted in the inadvertent tripping of embedded generation plants by their Loss of Mains (LoM) protection. A definite event was recorded on 22nd 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 Vector Shift protection. This event resulted in a loss of infeed and a frequency excursion that was bigger than anticipated.

Therefore, the purpose of the modification proposal is to ensure that all embedded Non-Type Tested Generating Plants greater than 50Kw or 16amps per phase (with a commissioning date on or after the date of implementation of these proposals) comply with the following:

  1. Rate of Change of Frequency (RoCoF) settings changed to 1 Hz/s with a definite time delay of 500 ms for all new non-type tested generators. Generators commissioned on or after 1st February 2018 would be required to commission with the new setting;
  2. All Non-Type Tested Generating Plants commissioned on or after 1st February 2018 will not be allowed to use Vector Shift (VS) as a means of Loss of Mains (LoM).

Our ComAp MainsPro and InteliPro Mains Protection Relays are fully compliant to the latest G59/3-3 updates. They are fully field tested with a number of test instruments used in the marketplace.

For more information on these changes or on our mains protection relays, please get in contact with Ian Wassman on or 07767 112262.