Location of shunt faults in radial power distribution systems considering capacitive effect and non-homogeneous lines

Abstract

This article proposes an alternative for low impedance shunt fault location in radial power distribution systems using the fundamentals of voltage and current measured at the power substation. This proposal includes typical characteristics of power distribution systems, such as unbalances, non-homogeneous line sections and untransposed lines; also we consider the capacitive effect that can significantly affect the behavior of a fault location method. The proposed method, presents errors in location of about 1% respect to the radial length where fault is located. The continuity of electricity service is an essential part of the of power quality in distribution systems, and is highly related to the detection and location of permanent faults in the network. Fault location is a topic that has become increasingly important in recent years, due the actions performed by the companies responsible for this service with the goal of reduce discontinuity rates in power distribution systems. Hence, distribution systems that have a good quality will be able to restore the service to customers quickly after a fault. In Colombia, the Regulatory Commission of Energy and Gas (CREG) in its resolution 097 of 2008 (1), establishes the parameters to measure electricity service quality for Local Distribution Systems, specifically with the use of two indicators, called IRAD and ITAD. Therefore, with an adequate location of permanent faults in distribution networks we can reduce the time of interruption and the frequency of fault events through a suitable preventive maintenance schedule at critical points of the system. Nowadays, fault location methods based on circuital model, show several developments that can improve the performance of the methods for localization, this developments allow to observe the apparent reactance of the system from information available at the substation (2), also it is possible to include capacitive effects of the networks (3), determine the load current downstream of the fault (4), and even consider variations in loads (5), but doing this require the use of approximations which reduce the efficiency of the techniques or performance of the methods that use radial power flow, like iterative sweep methods. The method presented in this paper permits to estimate the location of the faulted point, taking into account the measurements of voltage and current per phase from the substation, in addition to the knowledge of the values of impedance or admittance of the elements present in the system until faulted point.