All About G99
Purpose of G99-1
The purpose of this Engineering Recommendation (EREC) is to provide requirements for the connection of Power Generating Facilities to the Distribution Networks of licensed Distribution Network Operators (DNOs).
It is intended to address all aspects of the connection process from standards of functionality to site commissioning, such that Customers, Manufacturers and Generators are aware of the requirements that will be made by the local DNO before the Power Generating Facility will be accepted for connection to the Distribution Network.
The guidance given is designed to facilitate the connection of Power Generating Module(s) whilst maintaining the integrity of the Distribution Network, both in terms of safety and supply quality. It applies to all Power Generating Module(s) within the scope of Section 2, irrespective of the type of electrical machine and equipment used to convert any primary energy source into electrical energy.
If a piece of equipment has not been listed on the ENA’s ‘type-tested’ preferred supplier list, it has not been recognised as ‘type-tested’ by the ENA and cannot be used as such.
Why is G99 mains protection important?
The power generation landscape has seen a dramatic change over recent year. Instead of relying on a relatively small number of high-capacity power stations, we are turning towards a much larger number of low-capacity generators.
Wind Farms, photo-voltaic (PV) solar sites and hydroelectric plants are replacing coal and oil power stations. In 2017, renewable sources generated 20% of the UKs energy, and now its moved up to almost 36%.
When talking about generators on power generating sites, we are referring to synchronous generators.
A synchronous generator is known as such because the frequency of the voltage is directly proportional to the RPM.
In the case of asynchronous generating units, the output frequency is regulated by the power system to which the generator is attached.
The output frequency of a synchronous generator can be more easily regulated to remain at a constant value. They are also often more efficient. This is because they can easily be accommodated to load power factor variables.
The rapid expansion of lower-capacity generators can cause the grid to become less stable and this, risks damaging both the generator and the grid. Systems that run ‘parallel-to-mains’ must include a relay to decouple the generator from the grid if a problem arises with either.
So, this is where the new G99/2 testing comes in, because the tests are basically the same to prove compliance with G59, as we have always done with DNO witness tests.
So, anyone who has not been to one of our courses in the past Year, will need to upgrade their knowledge to include the new (loss of mains) ROCOF settings.
To obtain the list of spaces on the upcoming courses, please get in touch using the link shown below or just email david.pallas@save-electricity.co.uk
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