SEL-387A

Current Differential and Overcurrent Relay

The SEL-387A is an economical and efficient solution designed for the protection, monitoring, and control of two-winding power transformers. It inherits the high-performance protection features of the SEL-387 but is optimized for two-winding applications to provide superior cost-effectiveness. Combining differential and overcurrent protection, it can be flexibly applied to various power apparatus, including transformers, buses, generators, and reactors.

Key Features

Two-Winding Differential Protection (87)

Provides single- or dual-slope percentage restrained differential characteristics to maintain stability and prevent misoperation during through-fault conditions.
Harmonic Control and Security

Includes 2nd, 4th, and 5th harmonic blocking to prevent false trips during transformer energization (inrush) or overexcitation, supplemented by DC element detection.
Automatic Compensation

Performs internal phase angle and CT ratio compensation, allowing for easy installation without the need for external correction CTs.
Comprehensive Overcurrent Protection

Provides multi-layered backup protection using phase, negative-sequence, and residual overcurrent elements.
Optional Restricted Earth Fault (REF)

Supports the addition of two REF elements for sensitive detection of ground faults in wye-connected transformers.
SELogic Control Equations

Allows users to configure custom protection and control logic using variables, timers, latch bits, and more.

Advanced Asset Monitoring

Through-Fault Monitor: Records the accumulated stress from through-faults to help manage equipment lifespan and optimize maintenance schedules.
Temperature Monitoring: Integrates with the SEL-2600 RTD Module for real-time monitoring of critical operating temperatures.
Condition Monitoring: Includes standard breaker contact wear monitoring (Breaker Monitor) and station battery voltage monitoring.
Event Analysis and Recording

Features high-resolution oscillographic event reports and Sequential Events Recorder (SER) for rapid and accurate root-cause analysis of disturbances.
Flexible Communication Interface

Equipped with four independent serial ports (one front/two rear EIA-232, one rear EIA-485) for simultaneous connection to multiple supervisory systems.
Optimized Field Operations

Provides an advanced local operator interface with programmable text display points and local control elements for intuitive monitoring and operation.

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