GB1354851A - Method and device for remotely providing a measurement of an electric current in a high voltage line - Google Patents

Abstract

1354851 Measuring current in high voltage lines BALTEAU S A 19 April 1972 [20 April 1971] 18169/72 Heading G1U In a system for measuring the current in a high voltage line 6a, Fig. 1 the output of a generator 1 is divided into two signals by a hybrid-T junction 5, 5a, 5b, one of the signals is phase-modulated with the line current by a ferrite modulator 6 and applied, via a further modulator 12, to one of the symmetrical inputs of a second hybrid-T junction 7 functioning as a comparator, the other signal is applied via a fixed phase shifter 9a and a third phase modulator 8 to the second symmetrical input of the comparator hybrid-T 7, and the E and H outputs of the comparator 7 are applied to a differential amplifier 9 and an amplifier 10 to produce an output current which controls the phase modulator 8 in such a way that the two inputs to the comparator 7 are substantially equal, whereupon the output current from the amplifier 10 is proportional to the unknown line current and can be displayed on a conventional meter (not shown). The differential amplifier 9 also provides a signal for the modulator 12 which is said to compensate for frequency and/or power variations in the output of generator 1. Signals from the generator 1 are transmitted to and from the vicinity of the high voltage line 6a by wave guides 2, 3, 4, which preferably include temperature stabilizing means such as a circulating fluid. In a first modification Fig. 2, (not shown) instead of comparing the two outputs of the hybrid-T comparator 7 in the differential amplifier 9, only one output is used and this is compared with a fixed reference signal. Further, instead of compensating for frequency and/or power variations by modulator 12, the output of amplifier 14 may act directly on the generator 1. In a second modification Fig. 3, (not shown) the waveguide 2 can be dispensed with by using an arrangement of circulators. In a third modification Fig. 4 (not shown) the modulator 9a and the hybrid-T 7 can be omitted and the signals can be detected (20, 23) before being applied to the differential amplifier 9, and the modulator 12 can be omitted by effecting direct control of the generator 1 by means of a further detector (21).