Series compensated line protection: system modelling and relay testing

Considerable progress has been made in modelling series compensated power systems. With the introduction of computer based test benches, a method has emerged that dynamically tests line protection against a full power system model. Currents and voltages, incorporating all the electrical phenomena of series compensated lines, can be injected into relays and their responses measured within the laboratory. Using two test benches, an overall protection scheme, comprising two relays and a communication link, can be fully exercised. Beginning with a synopsis of the protection problems expected, the authors give details of a special version of distance protection for series compensated lines. The relay modifications are described, and a summary of test results given. They conclude that the advanced test procedure has given the means of testing relays for a range of difficult applications, and in particular, has proven that distance protection can be practically applied to series compensated lines