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.

Retrospective upgrades

Well it has taken 4 Years for a decision to be made, but at last the powers that be are going to request, that all (SSEG) generation sites, that have an output of less than 5 Meg, are going to be subjected to the same changes as those over 5 Meg sites.

IE any sites with Vector Shift as the setting for loss of mains, will need resetting to (ROCOF) and if the system does not have a relay that can be reset, that relay will need replacing with one that does.

The panel in charge of the development of G99 recommendations and how it relates to the industry have sent out this information, we have shown this statement below, this information has relevance to both G99 and G100, the information below relates to the Loss of Mains settings for Grid Protection, and how the relays protecting those settings are required to operate.

The actual changes to G59/3-4 do not come into force until the end of April 2019, but all DNOs will be using the new G99 or G100 settings if a test is carried out before that Date.

Below is the statement from the panel.
(The electricity network licensees, i.e. National Grid and the Distribution Network Operators, have been working on a programme of desensitizing loss of mains protection on generation installations in the 5 to 50MW size range over the past four years. This work has now been completed.

It is expected that starting around the second quarter of 2019 the requirements will change such that all other generation connected to distribution networks will also need to have its loss of mains protection desensitized. The exact arrangements for undertaking this work, which will affect potentially thousands of smaller generation installations, have yet to be finalized. The maximum population size that might be involved in this programme is of the order of 50 000 sites.
Recognizing that there will be a significant workload in changing protection settings, and even in some cases changing relays, the network licensees are looking to establish a database of contractors who have the experience and competence to undertake the work.

A key requirement is full familiarity with the range of loss of mains equipment in use in Great Britain, and appropriate experience and expertise in the software and other techniques used to set up and control loss of mains protection).
End of statement from the panel.

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 30% of the UKs energy.

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.

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 G59/3-4 testing comes in, because the tests are basically the same to prove compliance with G99 as we have always done with G59/3-4 witness tests, have no doubt you will still need these skills.We believe the coming changes will completely change the relay testing environment so much so, that a lot of People will make a lot of money carrying out these tests, just think of the work involved, you may well be called to a site, where the whole system will need not only testing and recalibrating, but will need rewiring and a new relay fitting.

And as it says in the statement, there could be as many as 50,000 sites where these changes will need carrying out.

We are here to help you get ready for this massive market and aid you in getting on the database of contractors , so we will be helping passed clients who only want upgrades to understand G99 and G100 and how the ROCOF settings work within those new recommendations, or if you are a new client who has not yet obtained one of our test engineer certificates, we can help you with the full weeks test engineer course.

This will be a massive task and there are basically not enough testing engineers who understand these new settings to take on the task, so why not get trained to carry out these changes, and at the same time get to know the relays you will be working with, the training on the relevant relays is a requirement of the ENA Board.

The changes that will be coming in about the (Lose of Mains) settings, will now take place using G99 and G100 recommendations, so our courses will be concentrating on these guide lines.
So, anyone who has not been to one of our courses in the past Year, will need to upgrade their knowledge on the new ROCOF settings.

To obtain the list of spaces on the upcoming courses, please get in touch using the link shown below or just email