Neutral Earthing Transformers
For delta-connected 3-wire electrical systems with no star point, one solution to the absence of a neutral for connection to the earth or ground connection is to create an artificial neutral by using a zigzag or delta-star earthing transformer with a low voltage secondary winding. This can be connected to a suitably rated resistor of which the other terminal is earthed.
The neutral earthing transformer will be a short-rated dry type, rated for the ‘on’ time of the earthing package, which may be a short term rating of 10 or 30 seconds, or in some cases continuous – for example for offshore installations where safety considerations may require that faults are not cleared immediately.
Cressall Resistors manufactures complete earthing transformer designs of this type, with the transformer and loading resistor mounted in a single enclosure.