Relay Testing Background Nearly all complex relays installed today are microprocessor-based. Relays no longer use a disk and magnetic fields to determine the overload condition, instead they rely on complex circuitry, programming, and user input settings to protect the facility. Each relay manufacturer utilizes different programming interfaces and languages and offers varying levels of customization. The various functions utilize an input (current, power, voltage, frequency) with or without a directional element to trigger a user-defined pick-up….









