What is a Shunt Capacitor?

What is a Shunt Capacitor?

Shunt Capacitor Definition

A shunt capacitor is defined as a device used to improve power factor by providing capacitive reactance to counteract inductive reactance in electrical power systems.

Power Factor Compensation

Shunt capacitors help improve the power factor, which reduces line losses and improves voltage regulation in power systems.

Capacitor Bank

The capacitor reactance is generally applied to the system by using static capacitor in shut or series with system. Instead of using a single unit of capacitor per phase of the system, it is quite effective to use a bank of capacitor units, in the view of maintenance and erection. This group or bank of capacitor units is known as capacitor bank.

There are mainly two categories of capacitor bank according to their connection arrangements.

• Shunt capacitor.

• Series capacitor.

The Shunt capacitor is very commonly used.

Connection of Shunt Capacitor Bank

The capacitor bank can be connected to the system either in delta or in star. In star connection, the neutral point may be grounded or not depending upon protection scheme for capacitor bank adopted. In some cases the capacitor bank is formed by double star formation.Generally large capacitor bank in electrical substation is connected in star.

The grounded star connected bank has some specific advantages, such as,

• Reduced recovery voltage on circuit breaker for normal repetitive capacitor switching delay.

• Better surge protection.

• Comparatively reduced over voltage phenomenon.

• Lesser cost of installation.

In a solidly grounded system, the voltage of all three phases of a capacitor bank remains fixed, even during two-phase operation.

Location Considerations

Ideally, a capacitor bank should be placed near reactive loads to minimize reactive power transmission across the network. When a capacitor and load are connected together, they disconnect simultaneously, preventing overcompensation. However, it’s not practical or economical to connect a capacitor to each individual load due to varying load sizes and availability of capacitors. Additionally, not all loads are connected continuously, so the capacitors may not be fully utilized.

Hence, capacitor, is not installed at small load but for medium and large loads, capacitor bank can be installed at consumer own premises. Although the inductive loads of medium and large bulk consumers are compensated, but still there would be considerable amount of VAR demand originated from different uncompensated small loads connected to the system. In addition to that, inductance of line and transformer also contribute VAR to the system. On viewing of these difficulties, instead of connecting capacitor to each load, large capacitor bank is installed at main distribution sub-station or secondary grid sub-station.