How Is a Transformer Neutral Earthed?

Published 27 Aug 2026Updated 27 Aug 20265 min readIntermediateGrid

Quick answer — The neutral is earthed to hold the system at earth potential and to provide a return path for earth faults, and the method (solid, resistance, reactance or insulated) depends on the system voltage and the allowed earth-fault current. Solidly-earthed systems give a low fault level; resistance or reactance earthed systems limit the current and reduce plant stress and electromechanical torque.

Contents

Earthing methods
Why it matters
Design and protection

How is a transformer neutral earthed and why?

Earthing methods

Solid earthing clips the neutral to earth; resistance earthing limits the current; reactance (e.g. Petersen coil) earthing compensates the capacitive current; and a high-impedance or isolated earth is used in some small systems.

Why it matters

The method sets the earth-fault current, the overvoltage on the healthy phases, and the damage to the windings, so it affects the protection and the transformer design.

Design and protection

The neutral earthing affects the required insulation and the protection coordination (earth-fault, differential, restricted earth-fault), so it must be chosen and set to match the system.

References & standards

IEC 60076-1
IEEE C57.12.00

Book series Academy

Related manufacturers

Prolec GE (GE Vernova) · Prolec GE Waukesha · Hitachi Energy USA · Siemens Energy · Eaton · Virginia Transformer Corp

Related components

Tank & mechanical Protection, monitoring & diagnostics

Technical content is prepared from engineering references, standards frameworks, manufacturer documentation and industry sources. Contractual or compliance decisions should refer to current official standards. TransformerPath Technical Editorial.

Source transformers for this application

Submit an RFQ or browse manufacturers and components.

Submit an RFQ Get Verified