Behavior study of polarized distance relay in presence of the simultaneous faults

The first part of the paper is concerned with an algorithm of fault calculations for several cases of simultaneous faults to obtain complete information about the current and voltage which are needed in power network protection systems, especially distance relays. The second part presents the behavior of plain and polarized distance relays for each fault case and deals with the operation caused by simultaneous faults. It is shown that any distance relay protection scheme used can lead to incorrect operation in the presence of simultaneous faults. Finally, some modifications in distance relays must be provided to satisfy the requirements of the corresponding simultaneous faults.

1. INTRODUCTION

The major use of fault quantities is in the settings of protective system. The knowledge of the currents and voltages at several locations of a power system due to various faults are essential to select an adequate protection system and to determine the interrupting requirements for circuit breaker. Therefore, the various types of faults occurring at many locations throughout the power system must be calculated to provide sufficient data to develop the best co-ordination between different relays in the system and to study their behavior. It is known, that, there are four types for parallel fault. and two types for series fault may occur in a power system.