Series compensation is the method of improving the system voltage by connecting a capacitor in series with the transmission line. In other words, in series compensation, reactive power is inserted in series with the transmission line for improving the impedance of the system. It improves the power transfer capability of the line. It is mostly used in extra and ultra high voltage line.

Introduction:
Series capacitors are used on transmission lines for a variety of reasons, including increasing power transfer capability, reducing voltage drop, and improving system stability. However, their use depends on various factors, including the load VAR requirement.

Explanation:
The correct answer is option A, which states that series capacitors on transmission lines are of little use when the load VAR requirement is small. This is because series capacitors are primarily used to improve power transfer capability, which is necessary when the load VAR requirement is large. When the load VAR requirement is small, the power transfer capability of the transmission line is already sufficient, and the addition of series capacitors may not provide significant benefits.

Below are some points to support the answer:

- Series capacitors are used on transmission lines to increase power transfer capability by reducing voltage drop and improving system stability. They do this by compensating for the inductive reactance of the line, which can limit the amount of power that can be transferred.
- The amount of compensation provided by series capacitors depends on the load VAR requirement. When the load VAR requirement is large, the addition of series capacitors can significantly improve power transfer capability. However, when the load VAR requirement is small, the power transfer capability is already sufficient, and the addition of series capacitors may not provide significant benefits.
- The load VAR requirement can vary depending on the type of load connected to the transmission line. For example, a motor load may have a large VAR requirement, while a resistive load may have a small VAR requirement. Therefore, the decision to install series capacitors on a transmission line should be based on an analysis of the load characteristics.
- It is also worth noting that the use of series capacitors can have drawbacks, such as increased risk of overvoltage and resonance. Therefore, their use should be carefully considered to ensure that the benefits outweigh the risks.

Conclusion:
In conclusion, series capacitors on transmission lines are of little use when the load VAR requirement is small. Their use should be based on an analysis of the load characteristics and the potential benefits and drawbacks of their installation.

VAR load is small meant that , reactive power is less or use of inductive loads are small. When reactive power is increases then power factor decreases. To maintain power factor as 1 , We use series capacitors in transmission lines. When the series capacitors are of little used in transmission line, VAR requirement is small.