Littelfuse SE-325 User Manual
Protection Relays & Controls
Neutral-Grounding-Resistor Monitoring
SE-325 SERIES (PGM-8325)
Neutral-Grounding-Resistor Monitor
Simplified Circuit Diagram
Description
The SE-325 Neutral-Grounding-Resistor Monitor is used on
resistance-grounded systems up to 25 kV to monitor the
integrity of the neutral-to-ground path and to detect ground
faults. It measures current and voltage in a transformer or
generator neutral-to-ground connection and continuity of the
neutral-grounding resistor (NGR). The SE-325 coordinates these
three measurements to detect a loose connection, corrosion,
ground fault, or NGR failure, and provides one alarm or trip
output contact.
Features & Benefits
FEATURES BENEFITS
Continuous NGR
monitoring
Ground-fault
Detection
Adjustable pickup
(0.5 - 4 A)
Adjustable time delay
(0.1 - 2 s)
Output contacts Form A output contact
Selectable contact
operating mode
Detects resistor failure within seconds, reduces
transient-overvoltage risk, removes risk of groundfault-detection failure
Main or backup protection to detect a ground
fault any where on the monitored system
Select greatest sensitivity without
false operation
Adjustable trip delay allows system coordination
Selectable fail-safe or non-fail-safe operating
modes allows connection to shunt or undervoltage
breaker coil or alarm system
CT
B
ER SERIES
(Sensing Resistor)
NGR
A
L1
L2
Ordering Information
ORDERING NUMBER CONTROL POWER
SE-325 120 Vac
SE-325D 120 Vac/Vdc
SE-325E 240 Vac
Consult manual online for additional ordering options.
ACCESSORIES REQUIREMENT
CT200 Series Required
ER Series Required
SE-MRE-600 Optional
RK-325, RK-325I, RK-302 Optional
RK-13 Optional
NGRM-ENC Optional
SE-325 SERIES
(NGR Monitor)
Accessories
A
B
ER Series Sensing Resistor
Required interface between the power
system and the SE-325. Eliminates
hazardous voltage levels at the monitor.
CT200 Series Current Transformer
Required CT detects ground-fault current.
RK Series Remote Indication and Reset
Optional panel-mounted remote indication
and reset assemblies. Available in NEMA 1 or
NEMA 4 configurations.
Specifications
IEEE Device Numbers Ground Fault (50G/N, 51G/N),
Overvoltage (59N), Lockout Relay (86),
Checking Relay (3)
Input Voltage See ordering information
Dimensions H 150 mm (5.9"); W 109 mm (4.3");
GF Trip Level Set tings 0.5-4.0 A
GF Trip Time Settings 0.1-2.0 s
RF Trip-Level Settings 20-400 Vac (≤5 kV systems)
100-2,000 Vac (>5 kV systems)
Contact Operating Mode Selectable fail-safe or non-fail-safe
Reset Button Standard feature
Output Contacts Form A
Approvals CSA certified,
C-Tick (Australian)
Conformally coated Standard feature
Warranty 5 years
Mounting Surface
D 100 mm (4.0")
UL Listed (E340889),
© 2013 Littelfuse Protection Relays & Controls
Littelfuse.com/se-325
Rev: 4-A-050213
Based on Manual Rev 12
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