Which device is used to regulate reactive power and can resemble a transformer in appearance, but is connected primarily to the source circuit?

• A. Shunt Reactor
• B. Voltage Regulator
• C. Isolator
• D. Capacitor Bank

Answer: (A)

Regulating reactive power on a power system is done with devices that either absorb VARs in shunt or supply VARs with capacitors. A shunt reactor fits the description because it is connected in parallel to the line, usually on the source side, and behaves like an inductive element that absorbs reactive power from the system. Its large core and windings give it a transformer-like appearance, but the role is to draw reactive power from the source to control voltage levels and stabilize the system, especially on long or lightly loaded lines. Capacitor banks supply reactive power to raise voltage, voltage regulators adjust voltage by changing transformer taps to keep voltage within limits, and isolators are switches that disconnect parts of the circuit; none are primarily used to regulate reactive power in the way a shunt reactor does.