Neutral Earthing Resistors (NERs) – sometimes 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. NERs 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 (certifcates available)
- 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. NERs are a key component of the earth fault protection scheme in the majority of medium voltage electricity generation and distribution systems.