An earth fault distance location algorithm in compensated networks with additional estimation of the fault impedance and fault current

Abstract

Earth fault distance protection with distance protection relays is common practice in solidly grounded networks. However, in compensated networks earth faults can cause big problems, because they do not extinguish themselves. To find the fault point is from high interest also in combination with network expansion [9]. In previous investigations the authors found that the classic algorithm of these distance protection relays principally can be used also for compensated networks, - however the accuracy of the distance calculation strongly depends on the network conditions [1],[2]. In this paper a new improved algorithm is developed. For this purpose an exact 3-phase mathematical simulation model of the investigated network is used to check the results of the improved algorithm. The simulations show, that this improved distance calculation provides very good accuracy up to earth fault transitions impedances of 1 kohm. Furtheron it is shown in the paper that the same algorithm can be used in 2-phase networks as well. With the implemented improvements the algorithm again allows earth fault transitions impedances of up to 1 kOhm. Finally, the simulation results are validated by real test data to verify the usability of this improved algorithm.