The NGRM500 Neutral Grounding Resistor Monitor detects grounding-resistor failures and ground faults. It is intended for use in high-resistance grounded transformers and generators used in commercial and industrial power systems. In these systems, the NGRM500 monitors:

  • Current through the neutral-grounding resistor (NGR)
  • Voltage between the star point of the transformer and ground (voltage drop across the NGR)
  • NGR failure (open and short), including failure of connections between neutral and ground

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 a compact design with DIN rail mounting making it easy to retrofit into existing HRG applications or factory-install in new HRG packages. If customers prefer, they can easily program the relay via the built-in webserver. NGRM500’s can easily connect to a supervisory system with Modbus TCP/IP or RTU communications. Capabilities extend to 25 kV and 100 A.

The NGRM500 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, C22.1-21, Section 10, Grounding and Bonding.

  • Features
  • Accessories
  • Ordering information
  • Downloads
  • 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
  • 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
  • Range of use up to 2000 m AMSL
  • Fault/history memory
  • Analog output of measured values (0…10 V, 4…20 mA, etc., selectable parameters)
  • Password protection
  • Tripping on RMS, fundamental component signal or harmonics
  • Detection of AC and DC ground faults

Optional accessories for LINETRAXX® NGRM500

CD-series coupling device
Voltage UsysTypeArt. No.
400…690 VCD1000B98039010
400…1000 VCD1000-2B98039053
1000…4200 VCD5000B98039011
4300…14550 VCD14400B98039054
14551…25000 VCD25000B98039055

Measuring current transformer

Voltage/CurrentTypeArt. No.
AC up to 10 AW20 B98080003
AC up to 25 AW35
AC/DC up to 10 ACTUB103-CTBC35B78120030
AC/DC up to 25 ACTUB103-CTBC60

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

Variants of LINETRAXX® NGRM500

TypeSupply voltage US/
Frequency range Hz
Art. No.
NGRM500AC 48…240 V, 40…70 Hz
DC 48…240 V

Downloads for LINETRAXX® NGRM500



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