Integrating Renewables and CHP into the UK Electricity System: Investigation of the impact of network faults on the stability of large offshore wind farms

Simulations have been performed to investigate the impact of network faults on the stability of large offshore wind farms. Results are presented for balanced 3-phase faults applied on the GB 400 kV transmission system.

The studies indicate that faults on the GB transmission system (close to the wind farm) may cause instability of the large offshore wind farms. The voltage drop investigations show that for a 100% voltage drop at a 400 kV connection point (such as Norwich Main), a very fast clearance time (less than 90 ms) is required to maintain stable operation of a 120MW offshore wind farm. However, when the voltage drops are less than or equal to 60%, the critical clearance times are longer than 140ms.

The contours of voltage drop for the GB transmission system illustrate that for a 60% voltage drop the 3-phase fault would have to occur close to the connection point. Therefore the stability of the offshore wind farms may only be effected by relatively local faults. Possible remedial measures include the use of fast acting reactive power support, e.g. a Static Reactive Power Compensator (STATCOM).