GB1377474A - Systems for testing insulating or dielectric material - Google Patents

Abstract

1377474 Testing insulators or dielectrics F C ROBINSON & PARTNERS Ltd 22 Nov 1971 [21 Aug 1970] 40475/70 Heading G1U In a method of testing a specimen 20 of insulating material, the load presented to the transformer 19 is determined and pulses are applied of a power exceeding the continuous power rating of the transformer. Operation of the generator 17 causes sequence timer 14 to operate, causing contactor 13 and switch 15 to close in turn, the switch 15 preferably being closed for five half cycles. Fault signals are fed through amplifier 23 to a recorder 28, while a voltage from unit 27 is supplied to a memory voltmeter 38. In order to determine the inception voltage, fault signals are fed through shaper 30 of coincidence circuit 29 to bi-stable 31 and hence to counter 32. The output from curcuit 16 is fed to monostables 34, 35 to counter 36. Monostable 35 produces a resetpulse to bi-stable 31 so that the first pulse occurring after 31 has been reset is fed forward to counter 32. The counters 32, 36 supply output pulses to comparator 37 which when both are present, generates a signal to hold the voltmeter at the reading appearing at the occurrence of the fault. The counters 32, 36 are reset from the comparator 37 after the generation of the hold signal or upon receipt of a pulse from counter 32 without a pulse from counter 36.