Protection Automation Control PCS-974 Transformer Auxiliary Relay PCS-974 is an auxiliary relay, which can provide mechanical and backup protections for a transformer, a shunt reactor or generator in any voltage level. It provides up to 20 highpower- pickup binary inputs for mechanical element monitoring, alarming and tripping. The high-power-pickup design reduces the risk of Electro-Magnetic Interference (EMI) in order to improve reliability. Generally, mechanical relays include winding temperature relays, oil temperature relays and buchholz relays. The PCS-974 is compatible with IEC 61850 station bus and process bus applications. It supports IEC 61850-8-1 MMS, GOOSE and IEC 61850-9-2 Sampling Value. The RJ-45 faceplate port is provided for testing and setting in effort to make commissioning and maintenance easier. Functions Protection and Control • Overexcitation protection (24) Overexcitation protection is based on the ratio of voltage to into any side of the transformer using PCS- Explorer software. Underfrequency and overfrequency protection (81U/81O) Four-stage underfrequency protection and four-stage overfrequency protection are provided in each relay. The change-of-rate (df/dt) element is integrated for underfrequency protection. Zero-sequence voltage and outof-limit frequency are detected in order to block under-/overfrequency protection. Figure 1 PCS-974 Functional Block Diagram 3

• Two-stage phase-to-phase impedance protection (21) They are selectable to forward direction or reverse direction by logic setting. The power swing blocking logic is integrated to improve reliability. • Two-stage phase-to-ground impedance protection (21) They are selectable to forward direction or reverse direction by logic setting. The power swing blocking logic is integrated to improve reliability. • Power swing blocking releasing (PSBR) The unique power swing blocking releasing logic is integrated to prevent the mal-operation of impendence protection due to power swings. • Four-stage phase...

Protection Automation Control • Two RS-485 serial ports using IEC 60870-5-103 • One RS-485 serial port for clock synchronization User Interface • HMI interface with large-size LCD and 9-button keypad on the front panel • One front RJ-45 port for testing and setting • One RS-232 or RS-485 rear port for printer • Language selection - English + selected language • Assistant software - PCS-Explorer Features • To eliminate the interference from switchyard field, high-power-pickup binary inputs are designed for dedicated mechanical inputs, in order to improve the protection reliability. • A unique...