Phase Balance Protection Relays

Phase balance protection relays continuously monitor a three phase AC power supply, tripping upon fault condition. These relays protect against asymmetrical under or over voltage. The internal relay remains energised and the LED illuminates only when the voltage balance between all three phases is within the user adjustable limit and hence satisfactory for connection to the three phase equipment. The unbalanced trip point is adjustable from 5% to 15% of the nominal voltage through the front control knob. The relay is self powered, requiring no auxiliary power supply, and is available with either a single or double pole changeover relay output and built-in 5 second time delay.

Key Terms: B921 - Phase Balance - Protection Relay