An advanced method for testing of distance relay operating characteristic Academic Article uri icon

abstract

  • This paper introduces a new phasor-based method for testing relay characteristic. Regardless what is the principle the relay design is based on; cross polarizing, memory polarizing or no-polarizing at all; electromagnetic, static or micro-processor based; the relays are treated as black boxes and provided with test signals which are quite close to the real situation a relay would encounter under service. The system parameters, prefault and fault signals, and the transition period from prefault to fault should be correctly presented. Although the phasor based test method uses just the fundamental frequency test signals, it simulates a fault by instantaneously switching all signals between prefault, fault and postfault states while monitoring relay outputs. The results are much closer to the relay performance under service than what has been demonstrated by the existing steady-state and dynamic phasor test method. The results can also be used as a good reference point for interpreting test results of transient testing in which the dc and high frequency components are naturally presented. The operating characteristic of a relay resulting from a test without correct test signals and corresponding procedure is unrealistic. Certain conditions are required to obtain a characteristic that determines relay performance under service situations: Correct prefault voltages and currents; Correct fault voltages and currents; Correct transition from prefault to fault; Load current effect on the fault signals; Presence of the dc decaying offset; Presence of the high frequency transients; The far-end infeed/outfeed conditions. In this paper, prefault and fault signals for single-line-to-ground (A-G), double-line-to-ground (BC-G), line-to-line (BC) and three-phase faults (ABC) are derived based on the symmetrical component fault analysis method. Five different distance relays have been tested using the new method witti the DYNA-TEST simulator developed at Texas A&M University. A section of the Houston Lighting & Power Company power system is used as a practical model. To demonstrate the effect of prefault voltage and current oh the characteristic, three cases for each fault type have been implemented: Case I: prefault voltage = 0; prefault current = 0; Case II: prefault voltage = rated value (E=67 0 V); prefault current = O; Case III: prefault voltage = rated value (E=67 0 V); prefault current = selected value (5-30 A). Case I is equivalent to the situation of reclosing in to fault. Case II is the no-load or light prefault condition. A computer program is used to control the testing. Extensive test results are presented in the paper. Performance of the different relays is compared. It is clear from the test results that the new testing method can be used to idendify application and design problems. An example of the test results is shown in Figure 1 where the measured characteristic of a relay obtained through testing is compared with the theoretical characteristic.

published proceedings

  • IEEE Power Engineering Review

author list (cited authors)

  • Kezunovic, M.

complete list of authors

  • Kezunovic, M

publication date

  • December 1996