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The NGRM700 Neutral Grounding Resistor Monitor detects grounding-resistor failures and ground faults and monitors line voltages. It is intended for use in high-resistance grounded 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 and short), including failure of connections between neutral and ground
  • Line-to-line and line-to-ground voltages

The NGRM500 can display the measured values, including current and voltage harmonics on the human machine interface (HMI). Users are able to select filters for ground-fault current and NGR voltage to prevent nuisance operation in noisy applications. 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. NGRM700’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 NGRM700 features a 5,000 m above sea level capability.

It is an ideal solution that is easy to retrofit into existing HRG applications or factory-install in new HRG packages. Capabilities extend to 25 kV and up to 100 A.

The NGRM700 allows the user to meet Canadian requirements. It can be used to perform the functions required by Rule 10-302, Use of Impedance Grounded Systems, of the CE Code, C22.1-18, Section 10, Grounding and Bonding.


  • Determination of RNGR with passive and active measurement methods
  • Continuous monitoring of the RNGR even if the installation is de-energised;
  • Alarm or trip on ground fault
  • Monitoring of the current INGR
  • Monitoring of the voltage UNGR
  • Phase-to-ground fault indication (optional; up to 690 V direct coupling, otherwise via potential transformers)
  • Ethernet communication
  • Web server
  • Language selection (German, English GB and US, Spanish, French)
  • Test button (internal, external) with/without tripping
  • FFT analysis of the measuring signals
  • Pulser for manual ground fault location
  • 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 5000 m AMSL
  • Fault/History memory
  • Analogue 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

LINETRAXX® NGRM700 Variant(s)

TypeSupply voltage U/ Frequency range HzArt. No.
NGRM700AC 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.

Optional Accessories for LINETRAXX® NGRM700

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

Downloads for LINETRAXX® NGRM700

CE Declarations of Conformity NGRM 83.0 KB 2022/08/12 06:17:2512.08.2022 06:17:25
Quickstarts NGRM700/NGRM750 1.4 MB EN2022/12/02 11:08:3102.12.2022 11:08:31D00292
Datasheets NGRM700/NGRM750 1.0 MB EN2022/06/09 10:54:3909.06.2022 10:54:39D00292
Manuals NGRM700/NGRM750 5.3 MB EN2022/12/02 11:07:5502.12.2022 11:07:55D00292
Technical Information NGRM700 Guideform Specification (US) 141.8 KB EN2020/04/30 18:55:5630.04.2020 18:55:56
Manuals NGRM…-Modbus 443.2 KB EN2022/06/09 10:47:4409.06.2022 10:47:44D00292
Technical Information How to Size an NGR (US) 424.0 KB EN2019/05/13 10:31:3513.05.2019 10:31:35
Technical Information NGR Checklist (US) 245.3 KB EN2022/11/07 16:39:0207.11.2022 16:39:02
Technical Information Guideline on NGR/Safety Ground Monitoring 234.7 KB EN2019/09/20 13:52:3320.09.2019 13:52:33
Technical Information Guideline on NGRM Relay Testing 522.3 KB EN2021/10/26 18:41:5226.10.2021 18:41:52
Application Brochures System Grounding in the Americas, Australia, South Africa and Other Regions 576.7 KB EN2019/05/13 10:29:2213.05.2019 10:29:22
Product Brochures HRG & LRG Systems (US) 5.2 MB EN2020/03/05 21:02:3305.03.2020 21:02:33
Flyers Neutral Grounding Resistor Monitors (US) 343.7 KB EN2020/03/23 17:32:0023.03.2020 17:32:00