SEL SEL-387E Current Differential and Voltage Relay

SEL-387E Current Differential and Voltage Relay

Apply the SEL-387E Current Differential and Voltage Relay to provide comprehensive

protection, metering, and automation of transformers, reactors, and other power apparatus

Protection

Expand transformer protection capabilities with restricted earth

fault (REF), negative-sequence overcurrent, overexcitation, and

frequency elements. Innovative restraint and blocking prevent false

trips and enhance security while maintaining sensitivity to internal

faults.

Control

Simplify engineering designs with SELogic® control equations for

customizing advanced protection and control schemes. Apply

frequency elements for load shedding and/or load restoration

schemes

Monitoring/Metering

Oscillographic event reports, Sequential Events Recorder (SER)

reporting, and accurate three-phase power metering reduce or

eliminate external recorder and metering requirements. Station

battery voltage monitor, through-fault monitor, and circuit breaker

contact wear monitor assist maintenance programs.

Flexible Communications

Serial and Ethernet communications provide complete integra

tion. IEC 61850 communications offer high-speed, relay-to-relay

information exchange. Supported protocols include ASCII, binary,

and SEL distributed port switch communications. Built-in web server

provides read-only point of access to view metering, settings,

targets, and SER.

The SEL-387E Relay provides security against system and transformer

conditions that may result in relay misoperation. The fifth-harmonic

element prevents relay misoperation during allowable overexcitation

conditions. Second- and fourth-harmonic elements along with the

dc offset element provide security against inrush currents during

transformer energization. The even harmonic elements offer the

choice between harmonic blocking and harmonic restraint. In the

blocking mode, select either blocking on an independent phase basis

or on a common basis. The second-, fourth-, and fifth-harmonic

thresholds are set independently, and the dc blocking and harmonic

restraint features are independently enabled.

Overcurrent Protection

Each three-phase current input terminal has a total of 11 overcurrent

elements, 9 of which are torque-controllable, providing comprehensive

overcurrent protection on each winding input. For backup overcurrent

protection in ring-bus or breaker-and-a-half configurations, two

combined overcurrent elements operate on the sum of the currents

from windings 1 and 2. The combined currents from two separate

breaker CTs emulate the current as if from a single bushing CT applied

on the transformer.

Volts-Per-Hertz Protection

Overexcitation occurs when the magnetic core of a transformer

becomes saturated. When this happens, higher harmonic frequencies

become more prominent, resulting in overheating and damage.

Overexcitation conditions are detected by a volts-per-hertz element.

Use the relay outputs for alarm or trip functions.

The SEL-387E Relay provides sensitive, instantaneous, definite-time

elements plus a settable composite inverse-time/definite-time

characteristic. The relay also includes one user-defined inverse-time

characteristic programmed with SEL-5806 Curve Designer Software.

The inverse-time element has a percent-travel operating characteristic

similar to that employed by an induction-disk time-overcurrent

element. This characteristic coincides well with the heating effect that

overexcitation has on transformer components

The SEL-387E Relay has three differential elements that use operate

and restraint quantities calculated from the two– or three–winding

input currents. Set the differential elements with either a single- or

dual-slope percentage-restraint differential characteristic, as shown

below.

Restricted Earth Fault (REF) Protection

Enhanced Automation Elements

The REF function compares the directions of neutral current and

winding residual current for sensitive ground fault detection in

grounded–wye or autotransformer–connected windings.

Metering Functions

Voltage inputs combined with measured currents yield key metering

information in the SEL-387E Relay. Measured quantities include:

• Three-phase voltage and current from all inputs

• Three-phase and per-phase MW and MWh

• Three-phase and per-phase MVA

• Three-phase and per-phase MVAR and MVARh

• Frequency, volts-per-hertz, harmonics

• Differential currents

• Station battery—four settable alarm levels

Sequential Events Recorder (SER)

Retrieve time-tagged sequential event messages recorded by the

SEL-387E Relay to analyze the time relationships between assertion

and deassertion of logical elements. Apply the relay with an SEL-2032

Communications Processor to quickly and automatically receive SER

messages from the relay in an efficient binary format.

Advanced SELogic® Control Equations

Logically combine selected relay elements for various control

functions, and assign outputs to logic functions. In addition to

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