Abstract
The proliferation of Distributed Generations (DGs) in distribution networks has provided power system operation improvement while raising some protection challenges. Turning to bi-directional, the protection schemes of the deregulated distribution networks should be able to deal with an out-of-zone fault. More specifically, DGs impose bi-directional fault current and directional relay should be employed to identify correct fault direction so that the protective relays are prevented from mal-operation of out-of-zone fault. This paper introduces a current-based directional algorithm that utilizes a pre-fault current signal as the reference. This algorithm is designed based on the pre-fault current and rate of change of the fault current. As it can be inferred from the mathematical basis of the proposed method, it has low sensitivity to decaying DC and noise components. Also, the proposed index has a certain and straightforward range of variation between (-1, 1) for backward and forward fault direction, respectively. The performance of the proposed algorithm is evaluated for different scenarios such as variation of fault resistance, sampling frequency, and types of faults in three simulated systems and a laboratory test bench. The simulation and experimental evaluation results show the accuracy and speed of the proposed algorithm in comparison with similar algorithms.
Highlights
Expansion of the utilization of Distributed Generations (DGs) in distribution networks has led to its many benefits including loss reduction, improvement of voltage profile, increase in reliability, and reduction of environmental pollutants [1, 2]
DGs impose bi-directional fault current and directional relay should be employed to identify correct fault direction so that the protective relays are prevented from mal-operation of out-of-zone fault
Due to the presence of DGs in the distribution network, the protec tion schemes have been confronted with serious protection challenges
Summary
Expansion of the utilization of Distributed Generations (DGs) in distribution networks has led to its many benefits including loss reduction, improvement of voltage profile, increase in reliability, and reduction of environmental pollutants [1, 2]. While time-domain analysis has a high-speed response, these algorithms suffer from low accuracy, sensitivity to noise, and the decaying DC component Note that these algorithms can be implemented with a relatively low sampling rate. The proposed directional index is designed based on the pre-fault cur rent and rate of change of fault current and this algorithm belongs to the time-domain analysis group. - As discussed, the time-domain type of the direction fault detection algorithms suffers from signal transients, especially decaying DC components in the current-based algorithms. It has been Mathe matically proven that, due to the use of the rate of change of fault current signal, the proposed index has very little sensitivity to the decaying DC component.
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