ELECTRICAL OVERCURRENT PROTECTION GRADING IN V4D

Selective Coordination contributes to the localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings and settings. Selective Coordination is critical for the reliability of electrical distribution system and must be analyzed and test regularly. A properly engineered and installed system will allow only the nearest upstream overcurrent protective device to open for both overload and all types of short-circuits, leaving the remainder of the systems undisturbed and preserving continuity of service. The aim of this study is to perform a Coordination and Overload study for the electrical installation in Village-4D T1, in order to know the root causes of the continuous tripping of its main Circuit Breaker which results in frequent power outage in the area. The revision of past researches was the first step taken toward understanding the concept involving protections; followed by a series of site inspections which helped gather the relevant data needed for the study such as the types of protective devices and their arrangement as well as the ratings. The methodology required a sensitivity analysis of the CBs in the area of study and Overload study in which fault levels were simulated using Simulink/MATLAB. The preliminary results of the study based on CBs level of sensitivity showed that V4D protective devices level of sensitivity is medium, therefore less prone to nuisance tripping outside the nominal tripping current. Thus sensitivity is not the factor causing the breaker to trip. However the results from the overload study show that the increasing number of overheating appliances used by students causes the circuit to overload, thus tripping the main breaker.