Considering Pilot Protection in the Optimal Coordination of Distance and Directional Overcurrent Relays

Abstract

The aim of the relay coordination is that protection systems detect and isolate the <br><br>faulted part as fast and selective as possible. <br><br>On the other hand, in order to reduce the fault <br><br>clearing time, distance protection relays are usually equipped with pilot protection schemes. <br><br>Such schemes can be considered in the Di<br><br>stance and Directional Over-Current Relays <br><br>(D&DOCRs) coordination to achieve faster protection systems, while the selectivity is <br><br>maintained. Therefore, in this paper, a new formulation is presented for the relay <br><br>coordination problem considering pilot protection. In the proposed formulation, the <br><br>selectivity constraints for the primary distan<br><br>ce and backup overcurrent relays are defined <br><br>based on the fault at the end of the transmissi<br><br>on lines, rather than those at the end of the <br><br>first zone of the primary distance relay. To solve this nonlinear optimization problem, a <br><br>combination of Genetic Algorithm (GA) and Linear Programming (LP) is used as a Hybrid <br><br>Genetic Algorithm (HGA). The proposed approach<br><br> is tested on an 8-bus, the IEEE 14-bus <br><br>and the IEEE 39-bus test systems. Simulation <br><br>results indicate that considering the pilot <br><br>protection in the D&DOCRS coordination, not only obtains feasible and effective solutions <br><br>for the relay settings, but also reduces the overall operating time of the protection system.