Neutral Earthing

Earthing resistors installation

NER constructed from 304 stainless steel

Neutral Earthing Resistors

Neutral Earthing Resistors (NERs) – also called Neutral Grounding Resistors – are employed in medium-voltage AC distribution networks to limit the current that would flow through the neutral point of a transformer or generator in the event of an earth fault. Earthing resistors limit fault currents to a value that does not cause any further damage to switchgear, generators or transformers beyond what has already been caused by the fault itself.

Features of all Cressall grounding resistors include:
  • Current ratings up to 8,000 Amps
  • Full compliance with ANSI-IEEE 32, Terminology and Test Procedure for Neutral Grounding Devices
  • Stainless steel resistors and enclosures as standard, IP23 to IP56. (Cable boxes up to IP65)
  • Type-tested standard designs (certificates available)
Options include:
  • Supply of resistor banks only for incorporation into customers’ own enclosures
  • Shock-tested marine designs
  • Provision for CTs, heaters, special cabling, etc.
  • Interlocked off-load by-pass isolators
  • Single or multiple vacuum contactors

Cressall manufactures neutral earthing resistors for voltages up to 132kV and for any current and time rating. Earthing resistors are a key component of the earth fault protection scheme in the majority of medium voltage electricity generation and distribution systems.