PRO range of relays provide reliable and high performance protection. The |RU_PRO is a relay tor AC voltage supervision with universal application; it protects the three-phase network against over-, under- voltage, unbalance or earth faults in isolated networks. Beside the pure RMS value measurement of the line voltage the lRU_PRO evaluates the symmetrical components (Ul , U2 & UO sequence system). By evaluating these components relay |RU_PRO can detect the phase sequence, voltage unbalance and earth faults.The relay is equipped with an independent, 2-step over- (U>, U>>) and under voltage supervision simultaneously with separately adiustable tripping values and delay times. Voltage measuring is 3-phase. In this process there is a continuous comparison of the line conductor voltages in case of a delta connection and of the phase voltages in case of a star connection with the preset limit values. The highest voltage is always evaluated for over voltage supervision and the lowest voltage for under voltage supervision.
