GB1072982A - A synthetic testing installation for electric circuit breakers - Google Patents

Abstract

1,072,982. Testing circuit breakers. LICENTIA PATENT-VERWALTUNGS G.m.b.H. Sept.2, 1964 [Sept. 2, 1963], No.35908/64. Heading G1U. In an arrangement for examining the behaviour of high voltage power circuit-breakers when opened to interrupt capacitive currents a high alternating current is supplied to the breaker before it is opened and then a high voltage from a high voltage circuit is applied, representing a recovery voltage. The high voltage circuit comprises two oscillatory circuits, the first operating when the breaker contacts are opened shortly before the high current becomes zero, and supplying a capacitive current of small amplitude but high frequency. Before this oscillatory current becomes zero the second oscillatory circuit, tuned to mains frequency is connected up to the first oscillatory circuit as a result of which the transient voltage waveforms which are characteristic of capacitive disconnections appear at the test breaker gap immediately after the oscillatory current has become zero. To test a circuit breaker P, a generator G supplies current to a transformer T, the secondary of which provides a heavy current i k which is passed through P via an auxiliary breaker H. Shortly before the heavy current i k falls to zero (i.e. at time t 1 , Fig.2) the breakers P and H are opened. The spark gap F 1 and breaker S 1 are fixed and closed by a control device St 1 operating from a current transformer W 1 . This causes a capacitive current i s due to the charge stored on the capacitor C s to flow through the breaker gap and the oscillatory elements R e , L 1 and C e . As this current falls to zero, the spark gap F 2 is fired by the control device St 2 operated from the transformer W 2 , so that at the moment t 2 when i s becomes zero, the circuit C s L s oscillating at the operating frequency is connected, to simulate the expected operating conditions of the breaker.