The coordination between DOCRs is nonlinear and highly constrained optimization problem in which two settings, namely, TDS and PCS of each relay are considered as decision variables. The main objective is to minimize the sum of OTs of all the primary relays, which are expected to operate in order to clear the faults of their corresponding zones. In this chapter, a hybrid GSA-SQP optimization algorithm has been proposed and successfully applied to solve the DOCRs coordination problem. The SQP routine is incorporated in GSA as a local search mechanism to improve the performance of the conventional GSA algorithm. The proposed approach has been tested and investigated on three different test systems. Simulation results show that the hybrid GSA-SQP algorithm provides effective and robust high-quality solution. Moreover, the results obtained using hybrid GSA-SQP are either better or comparable to those obtained using other techniques reported in the literature. The proposed hybrid GSA-SQP algorithm is suitable to find the global optimal solution for the DOCRs coordination problems, because it benefits from the advantages of both GSA and SQP methods.

Chapter Contents:

• 13.1 Introduction
• 13.2 Problem formulation
• 13.2.1 Objective function
• 13.2.2 Limits of the settings
• 13.2.3 Limits of relay operation time
• 13.2.4 Coordination criteria
• 13.2.5 Modification of objective function for minimization of CTI
• 13.3 Solution method
• 13.3.1 Overview of GSA
• 13.3.2 Overview of SQP
• 13.3.3 Hybrid GSA–SQP algorithm
• 13.3.4 Implementation of hybrid GSA–SQP algorithm
• 13.4 Simulation results
• 13.4.1 Test system 1
• 13.4.2 Test system 2
• 13.4.3 Test system 3
• 13.4.4 Statistical evaluation of the results
• 13.5 Educational program package ocdocr
• 13.6 Conclusion
• References

Inspec keywords: search problems; nonlinear programming; overcurrent protection; quadratic programming; relay protection

Other keywords: constrained optimization problem; optimal coordination; sequential quadratic programing; decision variables; test systems; PCS; pickup current setting; robust high-quality solution; gravitational search algorithm; hybrid GSA-SQP optimization algorithm; time dial setting; DOCR coordination problem; directional overcurrent relays; local search mechanism; nonlinear constrained optimization problem; TDS

Subjects: Combinatorial mathematics; Power system protection; Optimisation techniques