Capacitor bank protection

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)


Standard Protective & control elements
  • Under Voltage - 27
  • Under Current - 37
  • Negative sequence overcurrent transformer - 46LT
  • Phase overcurrent side H and side L - 50/51
  • Maximum Residual Overcurrent - 50N/51N
  • Overvoltage - 59
  • Breaker Failure - BF
  • CT Supervision - 74CT
  • Trip Circuit Supervision - 74TCS
SW Pack optional configuration
  • Thermal with Pt100 Probes - 26


  • One USB Type B local port for communication with ThyVisor setup software




In recent years the harmonic producing part of total load has increased continuously because of the ...