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.

What is G99?
G99-1 was announced in July 2018 and comes into effect from 27th April 2019:

And it allows equipment that is compliant with G99 to be connected in advance of 27th April, as it will also comply with the pre-existing G59/3-4 requirements.

After the 27th April 2019, you will be unable to connect using equipment that is compliant with G59/3-4 only.

G99 mains protection – are you ready?
The world of mains protection is changing. G99-1 mains protection will replace the current G59/3-4 in April 2019.

Type tested vs non-type tested equipment

There is a difference between type tested and non-type tested equipment. According to the ENA’s G99 document, type tested equipment is defined as:

A product which has been tested to ensure that the design meets the relevant requirements of G99 and that all similar products supplied will be constructed to the same standard and will have the same performance.

Type tested equipment includes inverters (the device that converts Direct Current to nominal frequency Alternating Current).

So, if you are not using type tested equipment the DNO can still ask you to carry out an on-site witness test, basically using the same test procedures and testing equipment as we have always used when carrying out G59/3-4 witness tests.

Be mindful that your DNO Engineer can still ask for a full witness test, therefore we have merged the two engineering recommendations G59/3-4 and G99-1 into one course, because next Year you will need to be aware of all the challenges from each set of recommendations.