OVERCURRENT PROTECTIVE RELAYS FOR ELECTRIC DISTRIBUTION SYSTEMS
DOI:
https://doi.org/10.4314/njt.v43i4.17Keywords:
Numerical, Electromechanical, micro-controller, over-current, relay, electric feederAbstract
This paper presents over-current protective relays for electric distribution systems. The objective is to determine the reliability of the system by comparing the performance of numerical and electromechanical relays. Electromechanical over-current protective relay on 33kV Itire-Ijesha distribution feeder was analyzed and modeled using MATLAB/Simulink. A numerical relay was proposed and also modeled using the real data of the existing Itire-Ijesha 33kV distribution feeder. While electromechanical relay was simulated as an instantaneous relay, the numerical relay was programmed and simulated as an IEEE moderately inverse definite minimum time (IDMT) relay. The simulation was for single line-to-ground fault with the red phase, double line-to-ground fault using red and blue phase as well as line-to-line fault using red and blue phase. Comparing the performances of the two different models, numerical relay tripped in mini-seconds while the electromechanical relay model tripped in seconds. In conclusion, therefore, the numerical relay proved to be superior, smarter, and more reliable than electromechanical relays.
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