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)
Applications • Bank capacitor / harmonic filter Protection functions • Pt100 thermometric probes (26) • Undervoltage (27) • Phase undercurrent (37) • Negative sequence overcurrent (46) • Neutral unbalance overcurrent with inherent unbalance compensation (46N) • Thermal image (49) • Phase overcurrent (50/51) • RMS phase overcurrent (50/51(RMS)) • Residual overcurrent (50N/51N) • Overvoltage (59) • Breaker failure (BF) • Discharge Timer (TD) Monitoring and control functions • CB diagnostic • Cold Load Pickup (CLP) • CTs monitoring (74CT) • Digital Fault recording (DFR) • Fault and event logging (SER & SFR) • Logic selectivity • Multiple setting profiles • Programmable Logic Controller • Self-test • Trip circuit supervision (74TCS) Hardware • 2 binary inputs + 6 output relays + 8 LEDs • Auxiliary power supply 110-230 Vac/dc • Auxiliary power supply 24-48 Vac/dc • Flush, projecting, projecting, rack, with separate MMI • Network module with Ethernet FX port (optical fiber) • Network module with Ethernet TX port (copper RJ45) + RS485 port • Nominal current 1/5 A selectable by DIP-switch • RS485 port (unavailable with Ethernet FX port) • Standard CT amperometric inputs 1/5 A Communication • IEC 61850 Protocol • Modbus RTU RS232 protocol • Modbus RTU RS485 / IEC 870-5-103 / DNP3 protocol • Modbus TCP/IP protocol (network board must be provided)
