chapter  4
36 Pages

Current Interruption in AC Networks

WithJ.C. Das

This chapter explores the various fault types, their relative severity, effects on the electrical system, and the circuit breaker itself. It shows that short-circuit calculations according to empirical methods in International Electrotechnical Commissionor American National Standard Institute/Institute of Electrical and Electronics Engineers standards do not and cannot address all the possible applications of circuit breakers. Current interruption in high-voltage ac networks has been intensively researched since the introduction of high-voltage transmission lines. The interrupting current at final arc extinction is asymmetrical in nature, consisting of an ac component and a dc component. A breaker may be used for line dropping and interrupt charging currents of cables open at the far end or shunt capacitor currents. The current and voltage waveforms of capacitance current interruption in a single pole of a circuit breaker under the following three conditions are shown: without restrike; with restrike; and with restrike and current chopping.