Date Code 20081022 Instruction Manual SEL-787 Relay
Section 1
Introduction and Specifications
Instructi on Manual
Overview
The SEL-787 Transformer Protection Relay is designed to provide current
differential and overcurrent protection to two-winding transformers, buses,
generators, etc. The basic relay provides current differential and instantaneous
and inverse time-overcurrent protection. Voltage-based and RTD-based
protection are available as options. All relay models provide monitoring
functions.
This manual contains the information needed to install, set, test, operate, and
maintain any SEL-787. You need not review the entire manual to perform
specific tasks.
Features
Standard
Protection Features
➤ Phase Instantaneous Overcurrent (50P)
➤ Ground (Residual) Instantaneous Overcurrent (50G)
➤ Negative-Sequence Overcurrent (50Q)
➤ Phase Time Overcurrent (51P)
➤ Ground (Residual) Time Overcurrent (51G)
➤ Negative-Sequence Time Overcurrent (51Q)
➤ Current Differential (87)
➤ Breaker Failure Protection
Optional
Protection Features
➤ Voltage-Based Protection
➢ Undervoltage (27)
➢ Overvoltage (59)
➢ Negative-Sequence Overvoltage (59Q)
➢ Directional Power (32)
➢ Loss of Potential (60LOP)
➢ Frequency (81)
➢ Volts/Hertz (24)
➤ Neutral Current-Based Protection
➢ Neutral Instantaneous Overcurrent (50N)
➢ Neutral Time Overcurrent (51N)
➢ Restricted Earth Fault (REF)
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