A Self-Balancing High-Voltage Capacitance Bridge

A self-balancing high-voltage capacitance ratio bridge, especially designed for continuous measurement of corona losses on experimental transmission lines, is described. The instrument is derived by combining a negative-feedback amplifier with a high-voltage capacitance bridge based on the current comparator principle. Manual control is provided for the four most significant decades of the bridge, thus permitting the function of the feedback amplifier to be limited to the balancing of small deviations. In this manner the errors originating in the amplifier and the associated indicating or recording instruments are made insignificant in the overall measurement. The accuracy of the built-in current comparator is 0.001 per cent, of the circuitry associated with the amplifier, 1 per cent. The output of the automatic balancing circuit is instrumented to produce a readout which is proportional to the power loss and reactive volt-amperes. Both components are in the form of small dc voltages and thus are suitable for recording.