Powering Life for Modern Humanity

LZR-Series Neutral Grounding Resistor (NGR)
Low Resistance Grounding System

Low Impedance Grounding Equipment for Detecting Ground Fault Current of a Medium Voltage Generator or Transformer Neutral


APT’s low impedance grounding Neutral Grounding Resistor and Reactor will reduce the stress and amount of damage to your power system equipment. They do this by controlling the magnitude of the ground fault currents. 

  • When used in generator neutral, these devices will also limit the amount of the generator available Line to Neutral fault current below the design limits set by the NEMA MG1 generators design standard.
  • Additionally, APT Neutral Grounding Resistors and Reactors will reduce the magnitude of the harmonic currents. This circulates in the neutrals of paralleled generators due to the differences in the generator winding pitches, armature reaction, and other system conditions.

APT Neutral Grounding Resistors help switchgear sense that there is current in neutral/ground. The NGR’s help dissipate that current.

Voltage Ratings


Current Ratings

100A – 400A

Temperature Rise

1400°F (Maximum)

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Neutral Grounding Resistor Core Features

  • Used in the neutrals of generators, transformers, and other rotating machines
  • Performs best when operated in a 120°F maximum ambient temperature, 0°F minimum ambient temperature, and an altitude 6000 feet or lower
  • Standard Enclosure includes:
    • Filtered ventilation louvers
    • NEMA 1/3R for indoor/outdoor applications
    • Hot Dip Galvanized
    • Cables: Bottom Entry/Exit
  • Enclosure Options:
    • Aluminum, Stainless Steel (304 or 316)
    • Powder coated ANSI 61 Gray or custom colors
    • One or two connection bushings that can either be top or side mounted
  • LZR-P Option to accommodate tight lead time requirements and other site-specific specifications
  • Window Type or Bar Type Current Transformer, with secondary terminals available for field interconnection to the ground fault relay
  • Unfused or Fused Voltage Transformer
  • Maximum Dimensions: 40″W x 38″D x 28″H
  • Approximate Weight: 500 lbs.

Neutral Grounding Resistor Product Applications

  • Electric Utility & Manufacturing
  • Water Treatment Plants
  • Low Service Pump Stations
  • Healthcare
  • Data Centers
  • Hotel Resorts
  • Many more!

Applicable Standards

Related Products

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Our Service & Expertise

Advanced Power Technologies (APT) offers a full range of:

  • Intelligent power distribution systems
  • Low and medium voltage switchgear
  • Walk-in equipment buildings
  • And more!

We design and build our products in-house, based on how you would like it to be. APT has many different options to create the best and reliable switchgear for your power system.

APT will provide a comprehensive system commissioning and integration once we install our equipment. We will continue our ongoing support during the lifetime of the installation, including:

  • Field service upgrades
  • Retrofits