Function:

35

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Current Differential Relays are used for the protec-

tion of transformers, motors and generators, by

comparing the magnitude of the current entering

and leaving the protected circuit. On a given phase

winding, any difference between the two currents

will indicate an internal fault; the relay will sense the

vectorial difference between the two currents of the

protected section and will initiate a quick disconnec-

tion of the unit, to prevent disastrous consequences.

The relay may also be used to protect internal faults

on transformers, such as: ground faults, shorted

winding, leakage between primary and secondary,

etc. It will sense and compare primary vs. secondary

currents, once the turns ratio has been taken into

consideration.

Operation:

With control voltage applied, the output contacts

(shown in the de-energized position) will remain de-

energized as long as the difference between the two

input currents remains below the preset trip value.

The contact will transfer to the engerized position

when the current difference exceeds the trip value.

Current Differential Relay

PRODUCT SPECIFICATIONS

Sample Part No.

WCD-230AC-1-A

Type:

WCD - Close Differential

Control Voltage VAC

& VDC

120AC

208AC

230AC

380AC

416AC

460AC

525AC

575AC

Trip Adjustment Range

.5 = 0.1 amp to 0.5 amp

1 = 0.2 amp to 1.0 amp

2 = 0.4 amp to 2.0 amp

Options

A = Two normally open contacts

B = Two normally closed contacts

H = Contacts rated 3 amp at 125 VDC

P = Transient protection is provided in compliance

with ANSI/IEEE C37.90-1978

Consult factory for additional models.

PART NUMBER SELECTION

Notes:

1.

Remove black screws for access to the trip adjustments.

2.

Clockwise rotation of the adjustment potentiometer will raise the current differential trip point.

3.

The output contacts are shown de-energized.

PART NUMBER SELECTION

Part Number

Line Current .....................................

Control Voltage ................................

Differential Trip Point .......................

Operating Temperature ....................

Burden ..............................................

Output Contacts ...............................

Contact Ratings ................................

WCD Series

Single Phase, AC current, 50-400 Hz Direct or from CT

5 amp continuously

20 amp 30 seconds

200 amp, 0.10 seconds

See Part Number Selection

Screwdriver adjustable.

See Part Number Selection

Current input: 2.5 VA max.

Control voltage DC: 2 W max.

AC: 2 VA max.

One set, N.O., One set N..C.

5 amp resistive at 120 VAC or 28 VDC

25DC

48DC

125DC

87

.172 DIA.

4 MTG. HOLES

3

3

7

4

5

TERMINAL STRIPS

#6 - 32 SCREWS

WILMAR™ Protective Relays – WCD Series