G59/G99 & Relay Testing

In recent years there has been a move to greener carbon neutral generation: Solar PV, Wind, Hydro, Tidal, Geothermal, Bio Diesel and Biomass.

These generation methods tend to be on a smaller scale compared to the older Power Stations (Previously Gas/Diesel/Heavy Oil and others), with locations not necessarily convenient for existing cabling resource. This has led to an update: G59 → G99 (April 2019).

G99 reflects the changes in the regulation, not just the actual testing and commissioning but whole process. Changes were made to reflect the changes within microgeneration including the availability of infrastructure. All in the effort to maintain grid stability.

Depending upon the size of the generation project there is one of two standards to follow:

Smaller projects, less than 16A per phase - G98 (formerly G83)
Larger projects, greater than 16A per phase - G99 (formerly G59)

As part of a piece of European Legislation (the Third Energy Package), a Network Code called Requirements for Generators (RfG) was written. A legally binding containing technical and operational requirements for generation connecting to networks. G98 and G99 were written to incorporate these new requirements into the existing requirements within Great Britain. The standards apply not only to generation but to storage projects also. The electric car market is growing quickly - we will therefore witness a considerable rise in storage projects going forward.

The key aspect to the acceptance test is the G99 relay itself, a G99 compliant Mains Protection Relay is an electronic monitoring device which looks at the quality and stability of the mains electricity. It is programmed to certain fixed parameters dictated by the DNO, these typically include voltage, frequency, ROCOF (rate of change of frequency), phase angle and so on. Should any of these areas go outside the programmed limits, then the relay will cause a protective device such as an MCCB or other type of circuit breaker to open, thereby instantly disconnecting the generator from the grid for protection and peace of mind.

TSL has invested in the Ponovo L336i with differential testing equipment for testing all types of relay. This equipment is superior the DVS3 and often used in place of the Omicron setups.

TSL has worked with all the major DNO's and can offer a G59/G99 relay proving service and/or installation if required on any generation setup. We have replaced numerous relays within the ALoMCP programme in 2021 and 2022.