Neutral Earthing Reactors

A Neutral Earthing reactor is a single phase unit connected between the neutral of a system and earth, for the purpose of limiting the line to earth current under system fault conditions. Neutral earthing reactors generally carry no continuous current, or only a small continuous current.

With regard to installation, these devices may be identified as:

  • Cast resin dry type, conventional dry type or oil immersed
  • With air core or gapped iron core
  • With or without magnetic shield
  • With or without enclosure
  • For indoor or outdoor installation
Consideration must be given to the possible effects of magnetic stray fields which may emanate from a current limiting reactor. An iron cored or shielded reactor will have minimal stray fields when operating at rated current. Under short-time current conditions, however, a high magnetic stray field will be generated even from a shielded reactor, because the magnetic shield is generally designed to be saturated when the reactor carries a high short-time current.

Therefore, the location of the phase windings and their position relative to operating personnel, other apparatus and metallic structures must be well planned so as to minimise exposure, undue heating and dangerous forces during the period of short time current.