What is Shunt Capacitor?

Shunt means parallel. In simple words, the capacitor is connected in parallel with a load or power supply is called shunt capacitor. The series and parallel combination of a no. of shunt capacitors is called shunt capacitor bank. So shunt capacitor is not a special device. It is a normal capacitor only, it is called a shunt capacitor because of its parallel connection with the load. Shunt capacitors are used in transmission lines, power systems, with inductive loads. So AC or non-polarized capacitors are used as shunt capacitors. For DC circuits or DC applications polarized capacitors are used. In this article, It is a brief introduction to shunt capacitor. 

In a single-phase system shunt capacitors are connected in a simple parallel combination. But in a three-phase system, shunt capacitors are connected in either start connection or delta connection. Generally, star connection mostly preferred as voltage stress across the capacitor is decreased.

How Does Capacitor Work?

First, we can note that a metal typically has an equal amount of positively and negatively charged particles, which means it's electrically neutral. If we connect a power source or a battery to the metal plates of the capacitor, a current will try to flow, or the electrons from the plate connected to the positive lead of the battery will start moving to the plate connected to the negative lead of the battery. However, because of the dielectric between the plates, the electrons won’t be able to pass through the capacitor, so they will start accumulating on the plate.

After a certain number of electronics accumulated on the plate, the battery will have insufficient energy to push any new electronics to enter the plate because of the repulsion of those electronics which are already there. At this point, the capacitor is actually fully charged. The first plate has developed a net negative charge, and the second plate has developed an equal net positive charge, creating an electric field with an attractive force between them which holds the charge of the capacitor.

Application of Shunt Capacitor:

• Electrical Power Distribution System. In an electrical power distribution system, shunt capacitors are used. Generally, shunt capacitors or shunt capacitor banks are connected in parallel with each feeder to improve the power factor of that particular feeder.
• Electrical Transmission line. Shun Capacitor bank also used in long-distance transmission lines. In long-distance transmission lines (above 66KV) shunt capacitor banks are used to increase the electrical power transfer capability without extra conductors. The shunt capacitor also used to balance voltage fluctuations.
• Electrical Substation. Shunt capacitor banks used in electrical substations also. When the load is increased above its limit the voltage level will decrease. Due to this all loads connected to that line or feeder will be affected. So Capacitor banks are used in substations to balance the voltage level during an overload or load variation. They also used for power factor correction also. Shunt capacitors also used in electrical substations as reactive power sources to supply the reactive loads.
• Inductive Load. Shunt capacitors are used with inductive loads like Induction Motors, Transformers, etc. The main purpose of using shunt capacitors or shunt capacitor banks to improve the power factor. Generally, the shunt capacitor bank is connected in parallel with the inductive load.
• Filter Circuit. Shunt capacitors are also used for filtering purposes. Shunt capacitor can remove noise, distortion from AC supplies. Generally, shunt capacitors are used somewhere in the electrical power transmission and distribution system to filter the electrical power. Not only AC circuits, in DC circuits such as Rectifier Circuit, power supply circuit, electronic tunning circuit, shunt capacitors are used for filtration purpose.

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