SPAD 346 C Stabilized Differential Relay

or transformer inrush situations. Due to these circumstances the operation of the differential relay has been stabilized in respect of the load current. In a stabilized differential relay the differential current required for relay operation is higher, the higher the load current is. The stabilized operation characteristic of the differential relay module and the setting range of the characteristic is presented in the description of the differential relay module SPCD 3D53. The operation of the differential relay module SPCD 3D53 is based on the fundamental frequency components. Operation based on fundamental frequency components is accurate and stable: the DC component and harmonics of the current do not cause unwanted operation of the protection stage.

Uaux Auxiliary voltage TS1...TS4 Output relay (heavy-duty types) SS1...SS4 Output relay IRF Self-supervision output relay BS1...BS5 External control inputs U1 Three-phase stabilized differential relay module SPCD 3D53 U2 Earth-fault relay module SPCD 2D55 U3 Combined overcurrent and earth-fault relay module SPCJ 4D28 U4 I/O relay module SPTR 9B31 U5 Power supply module SPGU 240A1 or SPGU 48B2 U6 Energizing input module SPTE 8B18 TS1...TS4 Output signals (for heavy-duty output relays) SS1...SS4 Output signals SERIAL PORT Serial communication port SPA-ZC_ Bus connection module Rx/Tx Receiver (Rx) and transmitter (Tx) for the connection of optical fibres