Which device is used to compensate reactive power in a substation and can resemble a transformer in appearance?

• A. Capacitor Bank
• B. Reactor Core
• C. Isolator
• D. Shunt Reactor

Answer: (D)

Reactive power compensation in a substation is achieved by devices that either supply or absorb VARs to keep voltage and currents in balance. A shunt reactor is connected in parallel with the line or bus and absorbs inductive reactive power, helping to control voltage levels on long or lightly loaded lines. Its construction—large magnetic core and windings—gives it an appearance similar to a transformer, which is why it can resemble a transformer in appearance. Capacitor banks, by contrast, supply reactive power (they provide leading VARs) and look like banks of capacitors rather than a transformer-like piece of equipment. An isolator is just a switch and doesn’t affect reactive power. So, the device that both compensates reactive power and can look transformer-like is the shunt reactor.