l Percentage current differential protection. (87PT)
l Unrestraint current differential protection. (87UT)
l DPFC current differential protection. (87DT)
l Restricted Earth Fault Protection/Zero sequence current differential protection. (REF, 87GT)
l Common-and-serial-windings differential protection only for autotransformer (87ST)
l Three-level directional overcurrent protection for HV side and MV side. (67P, 50P, 51P)
l Five-level directional overcurrent protection for LV side. (67P, 50P, 51P)
l Three-level directional zero sequence overcurrent protection for HV side and MV side. (67G, 50P, 51P)
l Two-zone phase-to-phase impedance protection for HV side and MV side. (21P)
l Two-zone phase-to-ground impedance protection for HV side and MV side. (21G)
l Two-level over excitation protection for HV side and MV side. (24)
l Zero sequence overcurrent protection for HV side and MV side (50N, 51N)
l Zero sequence overvoltage protection for HV side and MV side (59N)
l Breaker failure protection for HV side and MV side. (50BF)
l Zero sequence overvoltage protection for LV side. (59G)
l Combined-overcurrent protection for LV side (50P, 51P)
l Overcurrent protection for common winding of auto-transformer. (50P, 51P)
l Zero sequence overcurrent protection for common winding of auto-transformer. (50P, 51P)
l Voltage supervision element for overcurrent protection.
l Activating cooling equipment (49)
l Power swing blocking (68)
l Blocking on-load tap change (OLTC) during overload.
l Circuit breaker monitoring.
l CT failure detection logic.
l VT failure detection logic.
l Tripping circuit supervision.
l Voltage and current drift auto adjustment.
l 32 event reports, 32 alarm reports and 32 binary input reports.
l High resolution oscillography of last 8 oscillograms (compatible with international COMTRADE format)
l GPS clock synchronization.
l Communication ports: Ethernet with IEC 61850 (One additional communication unit is required) or 2 RS-485 with IEC 60870-5-103, 1 RS-485 for clock synchronization, 1 RS-232 or RS-485 for communication to printer, 1 RS-232 for testing and setting at the front.
l Main and backup protection can be integrated in one set of protection equipment. Protection information such as sampled data and binary inputs is shared by all elements.
l Delta→Y transfer method is used to adjust phase angle of secondary current on each side of the transformer, thus the faulty and healthy phase can possess its characteristic and the restraint of inrush current can be phase-segregated.
l Two discrimination principles for inrush current are provided: harmonics restraint and waveform distortion restraint.
l DPFC percentage differential protection is regardless of the load current and is sensitive to small internal fault current within the transformer. Its performance against current transformer saturation is also good.
l Zero sequence current at each side of transformer is generated by calculation of the equipment itself. The secondary zero sequence current of CT is balanced by software adjustment. Polarity of CT can be examined easily. Positive sequence current restraint is adopted to eliminate influence caused by unbalance current between three phases and CT saturation on zero sequence percentage differential protection.
l Distinguish of open and short circuit of current transformer is more reliable due to combination of voltage and current value method adopted.
l Most requirements to backup protection of all sides of the transformer are provided. The tripping output circuit can be configured by tripping matrix and suitable to any mode of tripping.
l The built-in reliable power swing blocking logic can properly supervise the impedance protection during a power swing. The power swing blocking logic can make the relay stand aside for an external fault during a power swing and pickup for an internal fault.
l The RCS-978 relay is based on NR’s well established and proven hardware platform of multi-processor. Two CPU modules are adopted in the relay. Each CPU module has one microprocessor and two digital signal processors (DSP). All CPUs can operate in parallel.
l The connector type can be selected as connectorized wiring connector and crimp terminal connector. The unique connectorized wiring connectors from the relay rear panel to the terminal blocks on the rack or cabinet makes the on-site commissioning and replacement much easier than when you do the commissioning using the traditional screw terminals on the rear panel.
l Innovative technology to prevent any undesired trip caused by any component failure is adopted. The relay has two independent data acquisition paths, one for a fault detector and the other for protection and its logic. Tripping outputs are supervised by the fault detector to prevent a mal-operation.
l Various GPS clock synchronizations are provided: second/minute pulse via binary input or RS-485, message via communication ports and IRIG-B synchronization.
l The format of event report is compatible with international COMTRADE file.
l The relay is equipped with Ethernet ports with IEC 61850 (one additional communication unit is required) and RS-485 ports with IEC 60870-5-103.