It is done through a grounding transformer, which has a primary winding in a star (wye) configuration and a secondary winding in an open (broken) delta configuration. A resistor is connected between the open delta terminals.
In the event of a fault, the voltage rises rather than drops because the voltage is nearly zero under normal conditions.
Grounding transformers are also used in substations for some Delta/Star (Wye) transformers.
On the delta side, we may need to increase the
zero-sequence impedance to reduce the current in case of ground faults.
Therefore, grounding transformers are used in such cases to limit the ground fault current to the rated current value.
Important Note:
- The secondary winding of the grounding transformer can also be used as a regular transformer (for power purposes) in addition to its primary winding’s grounding function.
- The grounding transformer is also referred to as:
- Earthing Ground Transformer (TR)
- Neutral Ground Transformer (TR)
- Large Potential Transformer (TR)
