Startco Engineering Ltd.
Page 2
SE-325 Neutral-Grounding-Resistor Monitor
Rev. 8
Pub. SE-325-M, May 6, 2008.
2.1.3 M
ODE
In the shunt-trip mode (SH), the output relay energizes
and its contact closes if a resistor-fault or ground-fault trip
occurs. The shunt-trip mode is not fail-safe because shunt-
trip devices do not operate if supply voltage fails.
In the undervoltage mode (UV), the output relay
energizes and its contact closes if the resistor-fault and
ground-fault circuits are not tripped. The undervoltage
mode is referred to as fail-safe because undervoltage devices
release if supply voltage fails.
2.1.4 RES
This switch setting must correspond to the resistance of
the external sensing resistor. For the ER-600VC and
ER-5KV, select 20K. For the ER-15KV and ER-25KV,
select 100K.
2.1.5 RES T
RIP
L
EVEL
Neutral-to-ground trip voltage is adjustable from 20 to
400 Vac with a 20-k
Ω
sensing resistor, and 100 to
2,000 Vac with a 100-k
Ω
sensing resistor. To prevent false
resistor-fault trips, the RES TRIP LEVEL should be set
higher than the voltage across the neutral-grounding resistor
when neutral-to-ground current is equal to the operating
value of the ground-fault circuit. Typical values for 5-, 15-,
and 25-A tripping systems are shown in Table 1. For others
systems, refer to the NGR Monitor Set-Point Assistant at
www.startco.ca.
2.2 I
NDICATION
AND
R
ESET
The green POWER LED indicates that the internal power
supply is on. Red LED's indicate ground-fault and resistor-
fault trips. When a trip occurs, the SE-325 remains latched
until the reset switch is pressed or supply voltage is cycled.
Terminals are provided for remote indication and reset as
shown in Fig. 1.
For the non-latching option, the SE-325 resets when the
fault clears.
2.3 F
USING
The output contact is protected by fuse F1 (4.0 A, time
delay).
TABLE 1. S
ETTINGS
FOR
T
YPICAL
S
YSTEMS
System
Voltage
Neutral-Grounding
Resistor
Sensing
Resistor
Ground-Fault
Trip Level
ResTrip Level
(Volts)
Let Through
(Amperes)
Resistance
(Ohms)
Model Resistance
(Ohms)
(Amperes)
(Volts)
480
600
2,400
4,160
480
600
2,400
4,160
7,200
14,400
7,200
14,400
25,000
5
5
5
5
15
15
15
15
15
15
25
25
25
55
69
277
480
18
23
92
160
277
554
166
332
577
ER-600VC
ER-600VC
ER-5KV
ER-5KV
ER-600VC
ER-600VC
ER-5KV
ER-5KV
ER-15KV
ER-15KV
ER-15KV
ER-15KV
ER-25KV
20,000
20,000
20,000
20,000
20,000
20,000
20,000
20,000
100,000
100,000
100,000
100,000
100,000
0.5
0.5
0.5
0.5
2.0
2.0
2.0
2.0
2.0
2.0
4.0
4.0
4.0
30
40
140
240
40
50
190
320
600
1,100
700
1,400
2,000