The relay type NC20 provides protection of shunt capacitor banks and harmonic filter circuits. The capacitor banks may have the following configurations: Single Wye grounded. Single Wye ungrounded (with a resistor on the output of the neutral unbalance voltage transformer in order to develop the appropriate input current for the unbalance protection). Double Wye ungrounded. The capacitor banks may be: internally/externally fused or fuseless capacitor units. A suitable compensation method is provided to compensate the inherent unbalance neutral current Protections 37, 49 and 50/51 (RMS) are based on RMS value measurement of the three phase currents (fundamental and harmonics up to the 11th)
In recent years the harmonic producing part of total load has increased continuously because of the ...