DEVELOPMENT OF AN OPTIMIZED DUAL RELAY SETTING COORDINATION SCHEME FOR DISTRIBUTION NETWORK WITH DISTRIBUTED GENERATION

In Distributed Generation systems (DG), the fault current through a relay in forward direction is mostly higher than in the reverse direction. Thus, it is desirable to have dual setting directional over current relay (DOCR) which can operate for both forward and reverse direction of fault current with two independent relay settings. The presence of DGs gives additional fault current contribution to the fault location. In this work, the coordination problem was formulated as a nonlinear optimization problem with the aim of minimizing the operation times of the relays using bat algorithm. The protection setting consists of two time-dial settings and one pickup current setting for each relay. The algorithm was used to obtain the time dial setting (TDS) with the objective of minimizing the TDS and constraint of satisfying CTI for network topologies and DGs operation. The performance of the presented coordination strategy was tested on distribution part of IEEE 30 bus system with synchronous DGs. In the case of TDS for without DG penetration for the relay at maximum/minimum category, the two cases I, II appreciated significantly with 99.96%, and 99.98% respectively. At the maximum/minimum operation for cases I, II with DG penetration result 99.98% and 99.99% respectively when compared with the base case. This show that the relay response fast to clear out the fault current in the network. Also, a reduction in cases I and II of fault current at maximum/minimum level without DG represent 25.12% and 14.47% respectively. At maximum/minimum fault current for cases I, II scenario with DG result to 29.33% and 14.94% respectively. The result illustrates that the algorithm used within dual setting protection scheme is significantly reaching the optimized coordination and the relay coordination is certain for all simulation scenarios with remarkable performance.