Cast Resin Transformers for System Earthing

TMC manufactures a large range of cast resin earthing transformers. Cast resin transformers contain no oils and are environmentally inert. The transformers are suitable for use by power distribution companies, private facilities such as city buildings, factories and mines and where environmental and fire restrictions limit the use of oil filled transformers.


Earthing Transformers

Cast resin earthing transformers are available in single phase and three phase. Single phase earthing transformers are used between the system neutral and earth. Three phase earthing transformers are used where there is no neutral available and can be supplied with an auxiliary winding for supply of power to other circuits. Zigzag neutral earthing transformers are particularly common – please see the downloadable brochure below for full details.


The transformers can be supplied in enclosures to various degrees of protection, or open (un-enclosed) if preferred. Enclosure ratings of IP21 to IP33 are common and protection up to IP66 is also available for extreme conditions and flameproof applications. Enclosures are fitted with sealed marshalling boxes fitted with temperature and performance monitoring equipment. Enclosures can be fitted with interlocked doors to provide additional safety.

Fan Cooling

TMC cast resin transformers can be supplied with fans and controls to increase the rated capacity (kVA). Forced directed air circulation permits a continuous power increase of up to 35% above the rated capacity. Fans can be used to economically provide extra capacity for overload conditions such as cyclic load peaks and traction loads.

Information Required with Enquiry :

  • Rated power (continuous load)
  • Short time load (in Amps for period of time in seconds)
  • Voltages
  • Impedance
  • Number of phases
  • Operating frequency
  • Connection symbol (Vector group)
  • Ambient conditions
  • Design standard
  • Enclosure protection rating
  • Temperature sensing equipment
  • Current sensing equipment (CT’s).