GB894107A - Electrical testing of electric switches - Google Patents

Abstract

894,107. Testing switch-gear. SIEMENSSCHUCKERTWERKE A.G. Feb. 3, 1961 [Feb. 3, 1960], No. 4264/61. Class 37. In an arrangement wherein the switch 1 to be tested and an auxiliary switch 2 are connected across a source 3, which provides through transformer U1, high current at a low voltage, the switch 1 is connected also to a high-voltage supply derived from the same source 3 by a transformer 5, the arrangements being such that the two currents pass through zero at the same or nearly the same instant. The currents and voltages are made co-phasal by the inductances 6, 7, the condensers 8, 9 and the transformers 4, 5. In a modification described with reference to Fig. 3 (not shown) condenser 9 is omitted and the secondary connections of transformer 5 are reversed. The arrangement simulates the condition when opening a capacitive load, i.e. unloaded lines or condenser batteries. The current in the switch 2 is arranged to reach its zero value a little earlier than the switch to be tested. The restriking voltage up is made approximately equal to that set up under working conditions by choice of the voltage U2 and of the value of condenser 8. A resistor may be connected in series with condenser 8 in order to ensure that the arc in switch 2 extinguishes before that in switch 1. In an arrangement wherein the test power is developed in a threephase generator 3, Fig. 4, the high current is developed from one phase, and the high voltage from across the other two phases, the currents produced being 90 degrees out of phase. Condensers 8, 8<1> are connected in series with switch 1 and the latter is shunted by a spark-gap device having an auxiliary electrode 16 connected to a resistance 18 through a condenser 17. A further spark-gap 19 connects the resistor 18 in parallel with the switch under test. The arrangement decreases the re-striking voltage in a manner described with reference to Fig. 5 (not shown). The contacts of the switch under test may be in a pre-set position and initially bridged by an ignition wire. The test may be mains energized.