Switchyard reactor

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In an electric power transmission grid system, switchyard reactors are large inductors installed at substations to help stabilize the power system.

For transmission lines, the space between the overhead line and the ground forms a capacitor parallel to transmission line, which causes an increase in voltage as the distance increases. To offset the capacitive effect of the transmission line and to regulate the voltage and reactive power of the power system, reactors are connected either at line terminals or at the middle, thereby improving the voltage profile of transmission line.

In large systems with many generators connected in parallel, it may be necessary to use a series reactor to prevent excessively large current flow during a short circuit; this protects transmission line conductors and switching apparatus from damage due to high currents and forces produced during a short circuit.

A shunt reactor is connected in parallel with a transmission line or other load. A series reactor is connected between a load and source.