Shunt reactors and series reactors are both types of reactors used in electrical power systems to control voltage and current under various operating conditions. However, they serve different purposes and have different effects on the electrical system. Here are the main differences between shunt reactors and series reactors:

Shunt Reactors:

1. Connection: Shunt reactors are connected in parallel with the transmission line or electrical system they are serving. They are typically connected between the line conductors and ground (neutral) or between phases in three-phase systems.

2. Purpose: Shunt reactors are primarily used to compensate for capacitive (inductive) reactive power in long high-voltage transmission lines, especially when the line is lightly loaded. Capacitive reactive power arises due to the distributed capacitance of the line, which can cause voltage instability and resonance issues.

3. Operation: Shunt reactors provide inductive reactive power to the system, which helps to counteract the capacitive reactive power and stabilize the voltage along the transmission line. By absorbing excess reactive power, shunt reactors improve the power factor and voltage profile of the system.

4. Effect: Shunt reactors increase the impedance of the transmission line at higher frequencies, effectively reducing the capacitance of the line and improving its electrical characteristics. They also help dampen transient voltage fluctuations and mitigate voltage surges caused by switching operations and lightning strikes.

Series Reactors:

1. Connection: Series reactors are connected in series with the transmission line or electrical system they are serving. They are typically inserted into the line conductors to limit the flow of current and control the system impedance.

2. Purpose: Series reactors are primarily used to limit the flow of short-circuit currents, improve system stability, and protect equipment from overcurrent conditions. They are often installed in distribution networks, industrial plants, and sensitive equipment installations.

3. Operation: Series reactors increase the impedance of the transmission line, which reduces the short-circuit current levels during fault conditions. By limiting the fault current, series reactors help protect equipment and prevent damage to the electrical system.

4. Effect: Series reactors increase the total impedance of the line, which affects the voltage drop and power transfer capability of the system. They also help improve the stability of the system by reducing the impact of short-circuit faults and transient disturbances.

In summary, while both shunt reactors and series reactors are used to control voltage and current in electrical power systems, they serve different purposes and are connected in different configurations. Shunt reactors compensate for capacitive reactive power and stabilize voltage, while series reactors limit short-circuit currents and improve system stability.