Modeling and Simulation of Differential Protection for a 2X15MVA, 33/11KV Injection Substation using Numerical Differential Relay

Abstract

The increase in size and capacity of power transformer units has brought about a considerable reduction in operation and maintenance costs; however, the risk of interruption of power supplies is always there if there is a breakdown in the transformer due to an internal fault. Therefore, differential protection has been in place for its protection against internal faults, but the differential protection scheme has been in use with matching current transformers (MCT). In this research, modeling, and simulation of a differential protection scheme for a 2X15MVA injection substation using a numerical differential relay were successfully carried out using MATLAB/Simulink. The methodology adopted was to model and simulate a differential protection scheme with a conventional relay and matching current transformer and to model and simulate a numerical differential relay under the following fault conditions: terminal fault, short circuit fault, and inter-turn fault. The validation of the scheme with numerical differential relay (NDR) was done by comparing the simulation graph obtained with that of the protection scheme with a matching current transformer (MCT), and the results obtained in graphical form show that the differential protection scheme with numerical differential relay (NDR) is 80% better, faster, cheaper, more effective, and easier to connect than the method with MCT.