The grounding Zig Zag transformers or reactors can be manufactured with an altitude up to 5,000 m.a.s.l. and up to 34 kV voltages.
Its core is made of siliceous steel grain-oriented to low losses and can also be manufactured with copper or aluminium coil, for indoor or outdoor use, dry or in oil, with a suitable design to resist to short circuit forces.
Grounding transformers or reactors allow to create a neutral connection in three-phase systems, composed by three-wires. This neutral is equipped with a current transformer to detect ground faults load side of the transformers and is normally connected solidly ground or through a resistor to limit the current.
Three-phase systems composed by three-wires are used between a phase and neutral, aiming for the permanent current from ground transformers to be small and, that way, the normal current would be the same as the no load current of the equivalent transformer.
Still, ground faults can occur in the system and when this happens, the short circuit current is limited only by the transformer impedance and ground resistance, for that reason it takes very high values. Therefore, the grounding transformer is designed to withstand these high currents that cause mechanical and thermal stresses.
In order to limit these high currents is recommended to install a resistance grounding. With that union, the result is a system connected to ground and limited by less harmful currents in case of failure.
This type of transformers are usually equipped with just one deviant ZIG-ZAG connection, it consists in three insulators equivalents to the phases and a neuter insulator. In addition, they can be equipped with the same accessories than a conventional transformer, they commonly are: protection elements as valve to relief pressure or a level of refrigerated liquid. It can also use Biodegradable vegetal oil or mineral oil.