6–64
345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
S3 Protection
The 345 protection elements are organized in two identical setpoint groups: Setpoint
Group 1 and Setpoint Group 2.
Each Setpoint Group has the same protection functions, depending on the relay order
code. These protection functions include:
•
87T Percent Differential (XFMR PCNT DIFF)
•
87T/50 Instantaneous Differential (XFMR INST DIFF)
•
87G Restricted Ground Fault (RESTD GND FAULT1(2))
•
49 Thermal Model (THERMAL MODEL)
•
51P Phase Timed Overcurrent (PHASE TOC1(2))
•
50P Phase Instantaneous Overcurrent (PHASE IOC1(2)
•
51G Ground/Sensitive Ground Timed Overcurrent (GROUND/SENS. GND TOC1(2))
•
50G Ground/Sensitive Ground Instantaneous Overcurrent (GROUND/SENS. GND
IOC1(2))
•
51N Neutral Timed Overcurrent (NEUTRAL TOC1(2))
•
50N Neutral Instantaneous Overcurrent (NEUTRAL IOC1(2))
•
51_2 Negative Sequence Timed Overcurrent (NEG SEQ TOC1(2))
•
50BF Breaker Failure (W1(2) BREAKER FAIL)