Recently the large increase in Renewable Connections has reached a stage in certain areas where the Network can no longer take all the potential generation connected to it. In these area the DNO's have responded by allowing connections on the basis that limited export or no export at all is required. Where limited export only is permitted and the User/Generator may have a widely varying local load, the answer is to utilise as export limiting relay. This monitors the export via CT's at the mains incoming supply point. The export limiting relay can be set to maximum levels of export and programmed to switch off an appropriate number of inverters either in one stage or a number of stages.
The DNO's requirments for this vary considerably. A working group has been set up to look at this issue, presumably with the view to standardise their requirements. Some DNO's have issued guidelines for their witnessing engineers to work to in verifying the relay settings and practically testing the systems.
In general terms the guidelines prohibit the use of Bluetooth, as a fail-safe system. Additionally the equipment must operate within a 1 second. At Solatest we are able to supply the hardware and site test by secondary injection this type of equipment to the requirements of the DNO.
This equipment can generally be incorporated alongside the G99 relay panel and tested at the same time. The system will work with a mixture of Renewables, PV and Wind Turbine.