What Is the Difference Between a Shunt and a Series Reactor?

Published 27 Aug 2026Updated 27 Aug 20265 min readAdvancedGrid
Quick answer — A shunt reactor is connected phase-to-earth (shunt) to absorb reactive power and control the voltage; a series reactor is connected in series with the line to limit the current and the fault level. The shunt reactor is rated in MVAr and reduces the voltage, while the series reactor is rated in ohms/current and limits the short-circuit and inrush current. They serve different purposes but are both single-winding inductive devices.
Contents
What is the difference between a shunt and a series reactor?

Shunt reactor

Connected across the line, it absorbs reactive power, reducing the voltage (used on lightly loaded lines and cables).

Series reactor

Connected in series, it limits the current, the fault level and the inrush; it has a small reactance and a large current rating.

Choosing

A shunt reactor for voltage control; a series reactor for current/fault limiting. They are sometimes both needed in a substation.

References & standards

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

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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.
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