Abstract: An integral shunt capacitor bank connected between high voltage AC terminals and comprising a plurality of serially-connected groups of paralleled capacitors is provided with a dual level overvoltage detection circuit between the paralleling buses defining each capacitor group. Each dual level detection circuit includes a voltage measuring impedance providing a low variable voltage proportional to the voltage to be measured and a pair of voltage responsive circuits across the measuring impedance. The voltage responsive circuits comprising each such pair are responsive to different overvoltage levels and include oppositely poled blocking rectifiers.

Abstract: Reactive current compensating apparatus for a multiphase electric power circuit comprises separately variable reactive impedance elements coupled to the power circuit in multiphase relation through phase shifting means such as a tertiary transformer winding. When phase voltage supplied to the compensating impedance leads or lags the line-to-neutral voltage of the power circuit the compensating effect in respect to negative phase sequence line current components is enhanced as compared to direct conductive connection of compensating impedance to the power circuit.

Abstract: A DC measuring circuit for power rectifiers is described wherein primary line current is utilized to measure direct current output. In the measuring circuit line current transformers are connected to a multiphase instrument rectifier through a phase shifting current transformer which is adjustable to compensate for difference between the primary to secondary line current phase shift characteristic of the power transformer and any phase shift in the line current transformers. By such compensation the average value of rectified primary line current in the measuring circuit is maintained independent of the commutating angle of the rectified power current.