Understanding the G59 Micro-generation StandardG59 is an industry standard for generators greater than 16A per phase (typically a 4kW PV system). G59/3 is the latest version of the standard and there have been some welcome changes made. Any request for connection over 16A per phase would require a G59 application to the Distributed Network Operator (DNO). Depending on which DNO’s jurisdiction the proposed installation falls under (Scottish Power, SSE, Northern Power etc) will determine how long it will take and the cost incurred for works.
G59 RelaysG59 relays are safety devices which switch of a generating stations with certain parameters. The often have to be tested by a specialist G59 test engineer and witnessed by a DNO representative. The image above shows an example of a G59 relay. They are essentially steel enclosures with a number of MCB’s and the main really inside. Often included are generation meters, system healthy light and a schematic.
G59 Application CostsG59 application costs can vary depending on the works required for the proposed connection. Usually the DNO will suggest the capacity which can be connected without upgrade works and also any costs to connect the desired capacity. For example, if a 100kW connection was requested it could be that the DNO would offer 75kW connection using the current infrastructure at no additional cost. However to connect the full 100kW may require cable upgrade works at a cost of £2,000 (or £10,000) it just really depends on what is currently in situ.
G59 Relay PanelsThe recent release of G59/3 sees some welcome changes to the requirement and specification of G59 relay panels. Historically G59 relay panels were a requirement for all installations over 50kW. Whilst this may still be the case more DNO’s are allowing inverters with built in G59/3 relays to act as the sole relay. SP Energy networks say this: “Applications greater than 17kW per phase must use G59 approved relays unless G59 type tested inverters are available. G59 applications must be submitted for system studies and associated network reinforcement where necessary prior to connection.” In general, for generators in excess of 16A per phase (3.66kW), the connection must comply with Engineering Recommendation G59/3, published by the Electricity Networks Association. The G59/3 guides can be found by clicking the links below. Don’t worry if this sounds like a foreign language! We will take care of everything G59 related. Our extensive experience has seen us gain approval for systems up to 1MW.
- Guide for G59/3
- Quick reference guide for G59/3
- Guide for G59/3 and is 50kW or less 3-phase or 17 kW or less single phase
- Quick reference guide for G59/3 and is 50kW or less 3-phase or 17 kW or less single phase