Ground Fault Trip Unit pick-up setting through one
phase of the circuit breaker as shown in Figure 5-1.
This should cause the breaker to trip and the ground
fault alarm light should light in less than 1 second. Reset
the breaker. Repeat the test on the other two phases.
If the system is a 4-wire system with a neutral current
sensor, apply the same current as described above
through one phase of the breaker returning through the
neutral sensor as shown in Figure 5-2. The breaker
should not trip and the ground fault alarm light should
not light. Repeat the test on the other two phases.
If the system is a 3-wire system with no neutral current
sensor, apply the same current as described above
through any two phases of the breaker with the connec-
tions exactly as shown in Figure 5-3. The breaker
should not trip and the ground fault alarm light should
not light. Repeat the test using the other two combina-
tions of breaker phases.
FIELD TESTING SHOULD BE USED FOR FUNCTION-
AL TESTING AND NOT FIELD CALIBRATION OF
THE DIGITRIP OPTIM 550 GROUND FAULT TRIP
UNIT.
ANY TEMPORARY CONNECTION MADE FOR THE
PURPOSE OF CONDUCTING TESTS SHOULD BE
RESTORED TO PROPER OPERATING CONDITIONS
BEFORE RETURNING THE BREAKER TO SERVICE.
The results of the test are to be recorded on the test
form provided with the equipment.
6.0 RATING PLUG
The rating plug, as illustrated in Figure 3-5, is used to
establish the continuous ampere rating of the related cir-
cuit breaker.
The Long Delay protection function of the trip unit is set
at the rating plug value (I
n
). The Short Delay and
Instantaneous protection functions are set as a multiple
of I
n
. The Ground Fault protection function is indepen-
dent of I
n
.
Different rating plugs are available to match the desired
current rating and type of circuit breaker into which the
trip unit is to be installed (Table 3.1).
I.L. 29C508B
Page 7
Effective 9/00
!
CAUTION
Figure 5-1 Connections for Ground Fault Trip Test
Source
Low
Voltage
Source
L C R
N
Load
Current Limiting
Resistor
(if required)
Source
Low
Voltage
Source
L C R
N
Load
Current Limiting
Resistor
(if required)
Figure 5-2 Connections for Ground Fault No-Trip Test,
with a Four-Wire System
