Central Relaying Unit for Wind Farm Based on Directional Angle and Differential Current

Abstract

Wind farm protection system is usually divided into different protection zones including the wind farm area, wind farm collection system, wind farm interconnection system and the utility area. The medium voltage collector feeder in a wind farm is usually protected by conventional protection strategy. The main drawback of this protection that it can't discriminate between faults occurred in the wind turbine generator (WTG) and cable feeder faults. Moreover, the protection relay did not isolate the faulted cable feeder from the WTG side. Therefore, the fault is still fed from the WTG. A new digital protection algorithm is proposed in this paper based on the fault current direction and differential current magnitude. The proposed protection algorithm identifies the internal fault location in the wind farm from external fault on the power grid based on the direction of the phase angle between voltage and current signals at the collection bus. The algorithm discriminates between internal faults in the protected collection cable feeder sections zones based on the differential current magnitude at each cable feeder section. A new set of zones are proposed to improve the proposed protection algorithm. The new suggested zones enabled the proposed protection algorithm to be a central protection scheme for the whole wind farm. The proposed algorithm is applied on a part of Zafarana wind farm which connected to 220 kV network of the unified Egyptian network.