Date Code 20080110 Introduction and Specifications 1-3
SEL-387E Instruction Manual
Restricted Earth Fault Protection
The SEL-387E Relay provides sensitive detection of internal ground faults via the Restricted
Earth Fault (REF) protection element. The Winding 3 inputs are used for introduction of neutral
CT polarizing current. Operating current is derived from the residual current calculated for the
protected winding. A directional element determines whether the fault is internal or external.
Tripping is supervised by zero-sequence current thresholds and a positive-sequence current
restraint setting. The REF function is applicable to a single grounded wye winding or an
autotransformer with one breaker and set of CTs at one terminal and one breaker and set of CTs
at the other terminal. Since the Winding 3 inputs are used for the neutral CT, only two of the
winding inputs may be used for normal differential or overcurrent protection purposes.
Overcurrent Protection
The SEL-387E Relay provides nondirectional overcurrent elements for each winding/terminal:
• Phase Overcurrent: Three-level instantaneous; definite time; inverse time
• Residual Overcurrent: Instantaneous; definite time; inverse time
• Negative-Sequence Overcurrent: Instantaneous; definite time; inverse time
In addition, the SEL-387E Relay has two special overcurrent functions:
• Combined overcurrent (inverse time, phase, and ground) for summed currents from
Windings 1 and 2
• Restricted Earth Fault (REF) protection for sensitive ground fault detection in grounded
wye-connected windings
Overcurrent element pickup settings and operating characteristics are independent of the
differential element settings. Most elements can be torque controlled.
Volts-per-Hertz Protection
The SEL-387E Relay provides sensitive dual-level elements to detect voltage overexcitation.
Level 1 volts-per-hertz elements provide instantaneous and definite-time operation for alarm or
trip. Level 2 elements provide one of three selectable inverse-time/definite-time composite
characteristics, or one user-definable inverse-time characteristic, for alarm or trip. Both volts-
per-hertz protection levels may be torque controlled.
Overvoltage and Undervoltage Protection
The SEL-387E Relay provides eight overvoltage and undervoltage elements. Elements include
phase undervoltage and overvoltage elements, phase-to-phase undervoltage and overvoltage
elements, as well as positive sequence, negative sequence, and residual overvoltage elements.
Phase and phase-to-phase elements operate when any individual phase exceeds the respective
setting. Combine these elements with SEL
OGIC
control equations to provide time delays for up
to 999999 cycles. The elements have many applications in protection, control, and indication.
To Next Page
Loading...
