Pre-approval? Small-scale DNO confusion

Connecting a solar power system to the grid involves an application process with the relevant Distribution Network Operator (DNO). In the past, domestic systems under 4kWp have required no pre-approval from the DNO and permission granted after the installation without incident. This has changed in recent times with DNO’s now requiring certain forms be submitted prior to installation depending on the generator’s size.

There has been some confusion in the industry regarding exactly what size presents an issue with DNO’s and pre-approval. It all comes down to whether a system is deemed a ‘small scale’ or ‘large’ generator.

Registering Solar Generators with the DNO

The general expectation is that the larger a system, the more pre-emptive documentation is required to be submitted to the DNO and approved prior to installation.
The main threshold for a solar power installation is whether it is above or below 16 amps per phase.  The guideline for your system’s rated amp output comes from the inverter’s AC output.

If you’re unsure about the amp rating of your solar power system, ask your installation company. Their electricians will be able to advise you which category the generator falls in to.

Small Scale Generators and the G83

Systems that utilise inverters with an AC output rating below 16 amps per phase are considered ‘small scale’. They can be installed straight away and registered by submitting a G83 form to the DNO after the installation.

EON has a copy of their G83 form here for download as an example.

Some inverters that are rated between 3.6kW and 4kW have AC output ratings over 16 amps per phase. Now seeing as the feed-in tariff changes after 4kWp for PV systems; this presents a different approach needed for  these installations.

Large Generators and the G59

For generators over 16 amps per phase it is a legal requirement for the DNO to be consulted prior to an installation taking place. In addition, a G59 form (download here) is required to be submitted. The process of a DNO reviewing and returning a successful G59 can take up to 8 weeks.

It is therefore vital that anyone installing systems around the 3.6kWp to 4kWp scale establish the correct process for registering their system right away. This is especially the case with the July 1 deadline approaching.

Property owners considering installing solar PV systems before the tariff drops in July are advised to compare their options, carefully select their installer and begin the process well before April 2012 is through.