NGR-US Series – Neutral-Grounding-Resistor System Series - Littelfuse NGR Resistance-Grounding Systems Provide Superior Protection

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Littelfuse products are not designed for, and shall not be used for, any purpose (including, without limitation, automotive, military, aerospace, medical, life-saving, life-sustaining or nuclear facility applications, devices intended for surgical implant into the body, or any other application in which the failure or lack of desired operation of the product may result in personal injury, death, or property damage) other than those expressly set forth in applicable Littelfuse product documentation. Warranties granted by Littelfuse shall be deemed void for products used for any purpose not expressly set forth in applicable Littelfuse documentation. Littelfuse shall not be liable for any claims or damages arising out of products used in applications not expressly intended by Littelfuse as set forth in applicable Littelfuse documentation. The sale and use of Littelfuse products is subject to Littelfuse Terms and Conditions of Sale, unless otherwise agreed by Littelfuse. "Littelfuse" includes Littelfuse, Inc., and all of its affiliate entities.

High-resistance grounding prevents many of the problems that are associated with ungrounded and solidly grounded electrical distribution and utilization systems. High-resistance grounding can limit point-of-fault damage, eliminate transient overvoltages, reduce the arc-flash hazards, limit voltage exposure to personnel, and provide adequate tripping levels for selective current-based, ground-fault detection and coordination. The Littelfuse Neutral-Grounding Resistor System includes a neutral-grounding resistor (NGR), current transformer, and sensing resistor installed in a NEMA 3R enclosure for use with high-resistance ground transformers and generators. The NGR system is designed for use with Littelfuse NGR resistor monitors for complete system grounding and grounding protection. This series comes pre-installed in a ventilated NEMA 3R galvanized, steel enclosure, and the components are pre-wired to terminals for ease of installation.

Note: The NGR series – US is specifically designed for use in US applications and all other parts of the world except Canada. For applications in Canada, please use the NGR series – Canada.


  • Ungrounded and solidly grounded electrical distribution and utilization systems
  • High-resistance grounding is applied on transformers and generators where safety and continuity of service are important
  • A faulted feeder may remain in operation until it is safe to repair the fault, where allowed by the local electrical code

Access specifications, certifications, check availability and order parts below

Catalog #CT secondary current AmpsInput
Voltage (V)
Mounting MethodWeight (lbs/g)built in CTsFrequencyInput Current Range (A)Input Impedance (Ohms)NEMA RatingResponse Time (ms)Sense Resistance (Ohms)StockCompare
NGRUS3140.05480Floor MountNo6021383RContinuousER-600VCCheck
NGRUS3150.05480Floor MountNo6021383R; Weather Protected Sensing ResistorContinuousER-600VCCheck
NGRUS3160.05480Floor Mount0 KgNo60555.43RContinuousER-600VCCheck
NGRUS3170.05480Floor MountNo60555.43R; Weather Protected Sensing ResistorContinuousER-600VCCheck
NGRUS3180.05600Floor MountNo602173.53RContinuousER-600VCCheck
NGRUS3190.05600Floor MountNo602173.53R; Weather Protected Sensing ResistorContinuousER-600VCCheck
NGRUS3200.05600Floor Mount0 KgNo60569.43RContinuousER-600VCCheck
NGRUS3210.05600Floor MountNo60569.43R; Weather Protected Sensing ResistorContinuousER-600VCCheck
NGRUS3220.054160Floor MountNo605480.93R10 sER-5KVCheck
NGRUS3230.054160Floor MountNo605480.93R; Weather Protected Sensing Resistor10 sER-5WPCheck
NGRUS3240.054160Floor MountNo605480.93RContinuousER-5KVCheck
NGRUS3250.054160Floor Mount0 KgNo605480.93R; Weather Protected Sensing ResistorContinuousER-5WPCheck
NGRUS3260.054160Floor MountNo6010240.53R10 sER-5KVCheck
NGRUS3270.054160Floor MountNo6010240.53R; Weather Protected Sensing Resistor10 sER-5WPCheck
NGRUS3280.054160Floor MountNo6010240.53RContinuousER-5KVCheck
NGRUS3290.054160Floor MountNo6010240.53R; Weather Protected Sensing ResistorContinuousER-5WPCheck
NGRUS3300.054160Floor MountNo6015160.33R10 sER-5KVCheck
NGRUS3310.054160Floor MountNo6015160.33R; Weather Protected Sensing Resistor10 sER-5WPCheck
NGRUS3320.054160Floor MountNo6015160.33RContinuousER-5KVCheck
NGRUS3330.054160Floor MountNo6015160.33R; Weather Protected Sensing ResistorContinuousER-5WPCheck
NGRUS33414160Floor MountNo602596.23R10 sER-5KVCheck
NGRUS33514160Floor MountNo602596.23R; Weather Protected Sensing Resistor10 sER-5WPCheck
NGRUS33614160Floor MountNo602596.23RContinuousER-5KVCheck
NGRUS33714160Floor MountNo602596.23R; Weather Protected Sensing ResistorContinuousER-5WPCheck

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