Difference Between Shunt Capacitors and Shunt Reactors

What is the Difference Between Shunt Reactor and Shunt Capacitor?

There are several devices used in an electrical power system to improve the power factor and its efficiency. A shunt capacitor and a shunt reactor are two different devices used to improve the performance of an electrical grid. There are several other differences between them that we will discuss in this article.

First, we will discuss their basics before going into the list of differences between shunt capacitors and shunt reactors.

Shunt Capacitors

A stunt capacitor is a capacitor or group of capacitors called a capacitor bank connected in parallel to the system. It is used to improve the power factor and efficiency of the power system. The capacitor is used to compensate for the inductive load thus improving the power factor of a system.

As we know, most loads connected in an electrical power system are inductive in nature such as electrical machines, transformers, relays, etc. They all contribute inductive reactance to the power system including the inductance of the power lines. As we know inductance causes lag in the current. Therefore, the current in the power system lags behind the voltage. The increase in the lagging angle decreases the power factor of the system. Due to this lagging power factor, the load draws more current from the source for the same power rating. This increase in the current causes extra line losses in the form of heat.

The capacitance of the capacitor causes to lead the current from the voltage. Therefore it can be used to cancel the inductive reactance in a power system. Multiple units of capacitors known as capacitor bank is connected in parallel to improve power factor known as shunt capacitors.

Shunt Reactor

A shunt reactor is a device used in a power system to improve its efficiency by stabilizing the voltage during the load variation. It is used for compensating the capacitive reactive power in a power transmission line. It is generally used for 400kV or above transmission lines.

It is made of a single winding either directly connected to the power line or the tertiary winding of a three-phase transformer. It absorbs the reactive power from the power lines to increase its efficiency.

Differences between Shunt Capacitor and Shunt Reactor

The following table shows the comparisons between shunt reactors and shunt capacitors.

Comparison Between Shunt Capacitors & Shunt Reactors

Function

• The shunt capacitor is used to provide reactive power to the electrical system which is absorbed by the inductive load in the system such as machines and transformers etc. It leads to power factor improvement and system efficiency.
• The shunt reactor is used to absorb and control the flow of reactive power in the system to improve its efficiency. It helps in controlling the voltage levels and improving system stability. It reduces voltage surges and transients.

Power Factor Correction

• Shunt capacitor directly affects and improves the power factor by providing reactive power.
• The Shunt reactor indirectly improves the power factor by stabilizing the voltage in the power line.

Connection

• The shunt capacitor is directly connected in parallel with the power line.
• The shunt reactor is either connected directly or with the tertiary of a 3-phase transformer.

Voltage

• The shunt capacitor can cause an increase in the voltage during light load conditions in a power system.
• The shunt reactor can cause a slight decrease in voltage due to the nature of inductive reactance.

Harmonics

• Shunt capacitors can cause resonant conditions that can amplify the harmonics in the voltage.
• The shunt reactor can dampen and eliminate the harmonics in an electrical power system.

Applications

• Shunt capacitor finds their applications in the improvement of power factor in different kinds of power systems in industrial and commercial buildings.
• While the shunt reactor is primarily used in high-voltage transmission lines for voltage stabilization.

We can conclude that both the shunt capacitor and shunt reactor are used to improve the efficiency of an electrical power system. Where the shunt capacitor improves the power factor and the shunt reactor stabilizes voltage and reduces harmonics in a power system.

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