Under Voltage Relays

The single-phase overvoltage relay basically comprises a tapped input transformer fitted with a plug-bridge, a potentiometer, a level-detector and a dry-reed repeat element. When the relay setting is exceeded, the level detector triggers and so energizes the repeat element. The single-phase undervoltage relay is similar to the above but is maintained operated and .drops off. when the monitored voltage falls below the relay setting.The three-phase relays comprise of three of the above elements.