Neutral Earthing

Earthing resistors installation

NER constructed from 304 stainless steel

Neutral Earthing Resistors

Neutral Earthing Resistors (NERs) are one of the commonest types of earthing systems in medium-voltage AC distribution networks. Also called Neutral Grounding Resistors, they 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
  • High resistance grounding resistors (for use where regulations permit, e.g. some offshore installations)

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.

Neutral grounding resistors are a key element in good electrical substation design. Cressall can be your trusted partner in this task.