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The NGRM750 Neutral Grounding Resistor Monitor detects grounding-resistor failures and ground faults and monitors line voltages. It is intended for use in low-resistance grounded (LRG) commercial and industrial power systems. It is an advanced device that allows monitoring of :

  • Current through the neutral-grounding resistor (NGR)
  • Voltage between the transformer or generator neutral point and ground (voltage drop across the NGR)
  • NGR failure (open), including failure of connections between neutral and ground
  • Line-to-line and line-to-ground voltages

A benefit to many users is the multilingual user interface that allows the comfort of reading values and programming in your native language. 

It is designed for easy retrofit with a panel mountable human-machine interface (HMI).  If preferred, the relay can easily be programmed via the built-in webserver.  NGRM750’s can easily connect to a supervisory system with Modbus TCP/IP or RTU communications.

For generator or transformer grounding applications at extreme altitudes, the NGRM750 features a 5,000 m above sea level capability.

It is an ideal solution that is easy to retrofit into existing LRG applications or factory-install in new LRG packages. Capabilities extend to 25 kV and 2,000 A.


  • Determination of RNGR with passive and active measurement methods
  • Continuous monitoring of the RNGR even if the installation is de-energized
  • Alarm or trip on ground fault
  • Monitoring of the current INGR
  • Monitoring of the voltage UNGR
  • Faulted-phase indication (optional; up to 690 V direct coupling, otherwise via potential transformers)
  • Ethernet communication
  • Webserver
  • Language selection (English, German, Spanish, French)
  • Test button (internal, external) with/without tripping
  • FFT analysis of the measuring signals
  • Relay for detection of ground faults and resistor faults
  • Relay for shutdown of the installation after a configurable time
  • Can be combined with RCMS… for automatic shutdown of feeders
  • Graphical user interface
  • Wide supply voltage range (24 to 240 VAC/VDC)
  • Range of use up to 5,000 m AMSL
  • Fault/history memory
  • Analog output of measured values (0…10 V, 4…20 mA, etc., selectable parameters)
  • Detachable HMI for door mounting
  • Password protection
  • Tripping on RMS, fundamental component signal or harmonics
  • Detection of AC and DC ground faults

Downloads for LINETRAXX® NGRM750

Quickstarts NGRM700/NGRM750 1.5 MB EN2022/06/09 10:52:1409.06.2022 10:52:14D00292
Datasheets NGRM700/NGRM750 1.0 MB EN2022/06/09 10:54:3909.06.2022 10:54:39D00292
Manuals NGRM700/NGRM750 5.4 MB EN2022/06/09 10:48:1109.06.2022 10:48:11D00292
Flyers NGRM550 & NGRM750 630.6 KB EN2022/05/25 06:07:5225.05.2022 06:07:52
Manuals NGRM…-Modbus 443.2 KB EN2022/06/09 10:47:4409.06.2022 10:47:44D00292
Technical Information NGR Checklist (US) 245.3 KB EN2022/11/07 16:39:0207.11.2022 16:39:02

Optional Accessories for LINETRAXX® NGRM750

CD-series coupling device

TypeVoltage UsysArt. No.
CD1000400…690 VB98039010
CD1000-2400…1000 VB98039053
CD50001000…4200 VB98039011
CD144004300…14550 VB98039054
CD2500014551…25000 VB98039055

Measuring current transformer

TypeVoltage/CurrentArt. No.
W20AC up to 10 AB98080003
AC up to 25 AB98080010
CTUB103-CTBC35AC/DC up to 10 AB78120030
AC/DC up to 25 AB78120031

Voltage supply for measuring current transformers CTUB103…

Typemax. connected measuring current transformersArt. No.
STEP-PS/1 AC/24 DC/0.52B94053110
STEP-PS/1 AC/24 DC/1.757B94053111
STEP-PS/1 AC/24 DC/4.217B94053112


TypeSupply voltage U/ Frequency range HzArt. No.
NGRM750AC 24…240 V, 40…70 Hz
DC 24…240 V
Accessory for FP200-NGRM: Transparent front cover 144x72 (for IP65)*B98060005

*When using the "transparent front cover 144x72 (IP 65)" the cutout in the switchboard cabinet must be extended in height from 66 mm to 68 mm (+0.7/-0 mm).

The degree of protection IP65 applies only to the user interface FP200-NGRM when using the front cover. The degree of protection for the complete device is still IP30.