The P79x is an integrated stabilising resistor and varistor unit suitable for use with any high impedance differential scheme. With its compact 20TE case design, it is suitable for rack or panel mounting and allows simple integration with any high impedance differential relay. These units are selectable for single-phase or three-phase differential applications. The P79x is designed with a number of fixed resistors internally. However, with simple parallel or series jumper combinations on the unit terminals, various stabilising resistance values can be obtained to meet the application requirements. The P79x protects the insulation level of the current transformers, interconnecting wiring and relay with the built-in varistors, included to protect the equipment against peak voltages developed during internal fault conditions.