Abstract
Abstract:
This paper includes a study and analysis of an earthed out of service for one of double circuit transmission lines impact on a Distance Measuring Relay (DMR) setting due to zero sequence system mutual coupling. The protection in a remaining line measures the fault impedance correctly, except when the line that is not in service is earthed at both ends. In this case a DMR performance which installed in this configuration at the ground faults occur is much less reliable and accuracy to get an ideal tripping protected zone for its. This study has been Modeling and simulting by using (MatlabSimulink) program to analyze a steady state of ground fault on single circuit to calculate the DMR voltage,current and apparent impedance of sequences and system at various fault locations under operational status for the Iraqi North Regional Grids (INRG) 132Kv system. The paper results shows that mutual coupling by zero sequence current of earthed line may cause the DMR to seriously over-reach under different operational situations. The DMR first zone reach may extend to its second zone, So a DMR will give a trip signal for an external faults.
