SE-330HV Series

Neutral-Grounding-Resistor Monitor

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The SE-330 is an advanced ground-fault and neutral-groundingresistor monitoring relay. It measures neutral current, neutral-toground voltage, and neutral-to-ground resistance. It provides continuous monitoring of the neutral-to-ground path to verify that the neutral-grounding resistor (NGR) is intact. This is of utmost importance—an open NGR renders current-sensing ground-fault protection inoperative and could result in a false belief that the system is functioning properly. The SE-330 can be used with low- and medium-voltage transformers and generators with low- or high-resistance grounding used in processing, manufacturing, chemical, pulp and paper, petroleum, and water-treatment facilities. For high-voltage applications, use the SE-330HV. For applications that require conformance to Australian standard AS/NZS 2081.3:2002, see the SE-330AU.

Resistor Monitoring

The SE-330 combines the measured values of resistance, current, and voltage to continuously determine that the NGR is intact. It is able to detect a resistor failure with or without a ground fault present. Sensing resistors are matched to the system voltage and are used to monitor NGRs on systems up to 72 kV.

Ground-Fault Monitoring

The SE-330 uses an application-appropriate current transformer to reliably detect ground-fault currents as small as 100 mA. DFT filtering ensures that false trips due to harmonic noise from adjustable-speed drives do not occur. Should the resistor open and a ground fault subsequently occur, the SE-330 will detect the fault through voltage measurement, while other current-only sensing relays would be ineffective.

Pulsing Ground-Fault Location

The SE-330 is capable of controlling a pulsing contactor, which is used to switch the NGR resistance in a pulsing-compatible NGR package. The resulting ground-fault current is distinguishable from charging currents and noise and will only appear upstream of the ground fault, making fault location fast and easy, even without isolating feeders or interrupting loads.

Features & Benefits

  • Continuous NGR monitoring

    Detects resistor failure within seconds, reduces transient-overvoltage risk, removes risk of ground-fault-detection failure

  • Ground-fault detection

    Main or backup protection to detect a ground fault anywhere on the monitored system

  • Adjustable pickup (2-100%)

    Select greatest sensitivity without false operation

  • Adjustable time delay (0.1-10 s)

    Adjustable trip delay allows quick protection and system coordination

  • Universal CT compatibility

    Allows the use of a CT that gives required ground-fault settings

  • Output contacts

    Two Form C (Ground Fault and Resistor Fault), Two Form A (Trip/Pulse, Healthy)

  • Analog output (4-20 mA)

    Allows for connecting an optional PGA-0500 meter or control system

  • Pulsing output (SE-330 only)

    Control the operation of a pulsing ground-fault-location circuit

  • Data logging

    On-board 10-event recorder helps with system diagnostics

  • Harmonic filtering (DFT)

    Eliminate false trips due to harmonic noise from ASDs

  • Local communications

    RS-232 port to view measured values, log to a PC and check event records

  • Network communications

    Remotely view measured values and event records, reset trips, and cause a remote trip

  • Software

    PC-interface software (SE-MON330) is included

  • Selectable contact operating mode

    Selectable fail-safe or non-fail-safe operating modes allows connection to shunt or undervoltage breaker coil or alarm circuit

  • Selectable reset mode

    Selectable latching or auto-reset operation

  • Calibrate push button

    Ensures resistor-failure sensitivity is correct
  • Unit-healthy output

    Verifies SE-330 is operating correctly

  • Conformal coating

    Internal circuits are conformally coated to protect against corrosion and moisture

SE-330 PCN Document

SE-330 Datasheet - Previous Revision

SE-330HV Datasheet New Revision

SE-330HV Manual - New Revision

SE-330HV Manual - Previous Revision

SE-330 DeviceNet Manual - Previous Revision

SE-330 EthernetIP Manual - Previous Revision

SE-330 Profibus Manual - Previous Revision

SE-MON330 Software Manual


  • IEEE Device Numbers: Ground Fault (50G/N, 51G/N, 59N), Checking Relay (3), Lockout Relay (86)
  • Input Voltage: See ordering information
  • Dimensions: H 213 mm (8.4"); W 98 mm (3.9"); D 132 mm (5.2")
  • GF Trip-Level Settings: 2-100% of CT-Primary Rating
  • GF Trip-Time Settings: 0.1-10 s
  • Vn Trip-Level Settings: 20-2,000 Vac (≤5 kV systems) 100-10,000 Vac (>5 kV systems)
  • Contact Operating Mode: Selectable fail-safe or non-fail-safe (K1)
  • Harmonic Filtering: Standard feature
  • Reset Button: Standard feature
  • Output Contacts: Two Form A and two Form C
  • Pulsing Circuit: 1.0-3.0 s in 0.2 s increments (SE-330 only)
  • Approvals: CSA certified, UL Listed (E340889), CE (European Union) optional, C-Tick (Australian)
  • Communications: RS-232; (standard) DeviceNet™, Profibus®(1), Ethernet (optional)
  • Analog Output: 4-20 mA, self or loop powered
  • Conformally Coated: Standard feature
  • Warranty: 5 years
  • Mounting Panel: and Surface

Ordering Information


SE-330 for all apps. 35 kV or less

SE-330HV for 72 kV apps.

0=120/240 VAC/VDC

2=48 VDC

0=RS-232 1=RS-232 & DeviceNet™ 2=RS-232 & Profibus® (1) 3=RS-232 & EtherNet/IP™ & Modbus® TCP


1=CSA, UL, CE, C-Tick

0=Normally Open

1=Normally Closed


ER Series Sensing ResistorRequired
Current TransformerRequired



ER Series Sensing Resistor
Required interface between the power system and the /wwHV. Eliminates hazardous voltage levels at the relay.

EFCT Series Ground-Fault Current Transformer
Sensitive ground-fault current detection (5 A primary).

SE-CS30 Series Ground-Fault Current Transformer
Sensitive ground-fault current detection (30 A primary).

Other Current Transformer
For low-resistance NGRs choose a CT primary approximately equal to the NGR rating.