grounding transformer
{{Short description|Power engineering device}}
A grounding transformer or earthing transformer is a type of auxiliary transformer used in three-phase electric power systems to provide a ground path to either an ungrounded wye or a delta-connected system.{{cite web |url=http://www.swedishneutral.se/download/Swedish%20Neutral%20Grounding%20Transformer%20Technical%20Specification%20English.pdf |title=Grounding Transformer |website=Swedish Neutral}}{{cite web |url=http://www.ecmweb.com/bonding-amp-grounding/grounding-transformers |title=Grounding Transformers |last=Dickinson |first=Mike |date=August 19, 2011 |website=Pacific Crest Transformers |access-date=September 4, 2017}} Grounding transformers are part of an earthing system of the network. They let three-phase (delta connected) systems accommodate phase-to-neutral loads by providing a return path for current to a neutral.
Grounding transformers are typically used to:
- Provide a relatively low-impedance path to ground, thereby maintaining the system neutral at or near ground potential.{{cite web |url=https://pact.in/blog/2021/08/what-is-a-floating-neutral |title=Floating Neutral Transformer |website=Neutral Transformers|date=14 August 2021 }}
- Limit the magnitude of transient over voltages when restriking ground faults occur.
- Provide a source of ground fault current during line-to-ground faults.
- Permit the connection of phase-to-neutral loads when desired.
Grounding transformers most commonly incorporate a single winding transformer with a zigzag winding configuration, but may also be created with a (rare case) delta-wye transformer.{{cite web |url=https://www.pacificcresttrans.com/grounding-transformer-faqs/ |title=Grounding Transformer FAQs |date=November 8, 2013 |website=Pacific Crest Transformers |access-date=September 4, 2017 |archive-date=August 13, 2018 |archive-url=https://web.archive.org/web/20180813182725/http://www.pacificcresttrans.com/grounding-transformer-faqs/ |url-status=dead }} Neutral grounding transformers are very common on generators in power plants and wind farms. Neutral grounding transformers are sometimes applied on high-voltage (sub-transmission) systems, such as at 33 kV, where the circuit would otherwise not have a ground; for example, if a system is fed by a delta-connected transformer. The grounding point of the transformer may be connected through a resistor or arc suppression coil to limit the fault current on the system in the event of a line-to-ground fault. Martin Heathcote (ed.), J & P Transformer Book, Newnes, 2011 {{ISBN|0080551785}}pp. 421-422