Production of transient-current waves with long time constants for test purposes

A development in laboratory bench-testing facilities for protective schemes is described. Test benches used at present contain linear inductors which have high X/R ratios so that offset transients associated with power systems may be simulated. However, owing to losses in the test network, these transients cannot be satisfactorily reproduced at large currents. It is shown here that by replacing the make switch in the conventional test bench with two inverse-parallel-connected thyristors, fired at carefully chosen intervals, it is possible to simulate transients on any system with acceptable accuracy. Details of the proposed test circuits are given, and both computed and experimentally obtained results are included to illustrate the negligible nature of the errors introduced. A method using the equipment for fusegear testing is also described.