PUB IB04300001E
D64RPB125 DIGITAL GROUND FAULT RELAY
Revision 1
September, 2004
Page 3
1. GENERAL
DESCRIPTION
The D64RPB125 is a microprocessor based ground fault relay for use on solidly grounded or resistance grounded systems. This
innovative digital electronic relay measures ground fault current using 3 built-in current transformers and an electronic zero
sequence circuit.
The D64RPB125 reacts to alternating current only and will reject direct current signals. It will maintain accuracy over a frequency
range of 45 to 65Hz, filtering out harmonics which could cause nuisance tripping, making it ideal for use on systems employing
static switching.
660 Volts is the maximum system operating voltage for the D64RPB125 when passing the system power conductors through the
built-in CTs. The CTs are positioned within the relays so that they line up with the terminals on the associated Eaton’s Cutler-
Hammer E125 (15 – 125 A) Frame circuit breaker.
The ground fault current trip level is set on a front accessible binary DIPswitch array. Trip currents can be selected in 8 discrete
steps from 0.1 Amp – 2.0 Amps. The trip level can be set just above the charging current
1
. Any deterioration in the circuit will trip
the relay. This also permits scheduled field testing of the relay (by lowering the trip level).
1
The capacitance-to-ground charging current on a system will vary depending on: the overall length of the cables; the
types of loads; the quality of insulation on the phase conductors; the surrounding equipment grounding, cable trays,
junction boxes, etc.; and, the type of transformer.
A "Rule-of-Thumb" for systems 600 Volts and lower: The charging current is 0.5 Amps per 1000 kVA of transformer
capacity.
The response time on ground fault trip is set on a front accessible binary DIPswitch array. Trip times from 20 milliseconds to 5.0
seconds can be selected in 8 discrete steps.
The output relay has Form “Z” (4 terminal) N.O. and N.C. contacts which may be used to operate the upstream protective device
and to indicate a failure of the system. The relay can be set to operate in any one of the following modes: Failsafe; Non-failsafe;
Auto Reset, or Pulsed operation by means of 2 front accessible DIPswitches.
By double clicking the cover mounted Reset button, the Reset button on the D64DMCC connected to the RJ –12 port, or a
remote Test/Reset button connected to terminals R1 and R2, a functional test of the D64RPB125 is invoked. A single press of
any of the above Reset buttons resets the relay after a trip. (It is not necessary to press the Reset buttons when the Auto Reset
or Pulsed operating modes are selected). A green RUN LED flashes to indicate when control power is applied to terminals N-
and L+. A red TRIP LED flashes to indicate the relay has sensed a ground fault current higher than the trip level for a period
longer than the trip time and that the output contacts have operated.
The 8 point terminal block is pull-apart simplifying connection of field wiring.
The D64RPB125 operates on any control voltage from 24 to 125 Volts ac or dc.
2. OPERATION
2.1
GLOSSARY OF TERMS
Manual Reset:
The cover mounted Reset pushbutton, the Reset button on the D64DMCC connected to the RJ –12 port, or a
N.O. contact remote Test/Reset pushbutton connected to terminals R1 and R2 of the D64RPB125 must be
pressed once to reset the output relay after a trip, providing the ground fault has been cleared or the measured
values are within the preset limits.
Auto Reset:
The output relay N.O. contact is closed when tripped and the N.C. contact is open when tripped.
The output relay does not change state when control power is applied to terminals N- & L+.
With control voltage on terminals N- & L+ (green RUN LED flashing), when the measured values reach or
exceed the DIPswitch settings for current and time, the output relay changes state (trips) and the red TRIP LED
flashes. The output relay will remain tripped until one of the following conditions is met:
