The electricity system is changing as older thermal plants based on large synchronous machines are displaced by renewables making increasing use of power electronics for connection and interconnectors using high-voltage direct current (HVDC) technologies. The result of this is the fault behaviour of the system is evolving as power electronic sources do not contribute the same high fault current as synchronous machines. These tests will validate the outcomes of the G74 review by recording system behaviour in response to the application of fault disturbances at two locations. By collating data on the network configuration as well as generation and demand during tests, the system can be accurately modelled in accordance with the new G74-2 guidance and the accuracy of the short circuit calculation technique assessed.

Benefits

• Ensure that a high degree of confidence is maintained in the calculation of system fault levels across a range of system conditions incorporating new generation technologies and other sources of fault current. The outputs from these system tests will be a valuable contribution towards validating the outcome of the G74-2 review.

• Provide a library of system responses under controlled disturbance conditions to investigate new measures of system strength and validate RMS and EMT modelling.

Permission to conduct these tests is highly likely to be contingent on an extensive review of protection settings applied to schemes in the area surrounding the test. Such reviews are always helpful in identifying any hidden protection issues thus aiding future system reliability. This will bring benefits to the grid-connected assets in terms of safety and reliability, by optimising their protections systems.