APTP Articles

Neutral Earthing Resistor

With increasing generation and network capacity added to an electrical network, fault level reduction is an ongoing task for electrical power distribution companies and the main business drivers are:

  • Maintain the existing equipment within design ratings to avoid expensive upgrades
  • Safety and reliability
  • Bushfire risk mitigation
  • Storms
  • Improvement of supply quality.

Short circuits between phase and ground can result in irreversible damage to networks and equipment, therefore a Neutral Earthing Resistor is a good preventative option to control and reduce their effects.

The reason for limiting the current by Neutral Earthing Resistor may be one or more of the following:

  • Reduce burning effects in faulted electrical equipment
  • Reduce mechanical stresses in circuits and apparatus carrying fault currents
  • Safety, reduce electrical shocks caused by stray ground fault currents in the ground return path
  • Easier detection of fault location
  • Transient over voltages.

There are different resistance materials used to build a Neutral Earthing Resistor:

  • Cast iron resistance elements, fragile, resistance not consistent and non-corrosion resistance
  • Liquid resistor, old technology, maintenance cost is high
  • Alloy Steel Grid type, best technical and economical solution.

The essential parameters needed for Ohmic Resistors Pty Ltd to design a Neutral Earthing Resistor are:

  • Rated voltage (Line to Line kV)
  • Fault current
  • Fault duration (10 seconds is customary)
  • Protection degree (IP) (IP23 is standard solution)
  • Enclosure finish (Galvanising/painted colour/Stainless steel)
  • Continuous current rating
  • Auxiliary items like current transformers, protection relays, vacuum contactors, On or Off load Disconnectors.


Ohmic Resistors has recently moved their manufacturing premises from Sydney to Brisbane and can now share resources with Cynebar in Brisbane with the STANDARD RESISTOR™ Brand resistors.

Standard Resistors brand is used throughout Australia and Overseas for Dynamic Braking applications, Motor Resistor starters and Neutral Earthing resistors. As specialised designers and manufacturers of high power and accuracy resistors, we are there to safeguard a very wide range of power, motor and distribution systems in railways telecommunications, laboratories, and major lift / elevator companies. STANDARD RESISTOR™ Brand consists of a wide range of wire wound resistors, D coat, Vitreous coating, and Bobbin style to suit your needs as a fixed resistor or adjustable resistor.

For more information contact Ohmic Resistors
02 9820 5055 or visit www.ohmic.com.au

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OHMIC Resistors