Application scenarios of reactors
Function, Principle, and Applications of High Voltage Shunt Reactors
Function, Principle, and Applications of High Voltage Shunt Reactors
High voltage shunt reactors are essential devices in modern power systems, mainly used to control voltage rise caused by excessive capacitive reactive power in high-voltage transmission networks. They are widely applied in long-distance overhead lines, high-voltage cable systems, and substations with light-load operating conditions.
Function of High Voltage Shunt Reactors
In high and extra-high voltage transmission systems, overhead lines and cables generate significant capacitive reactive power due to their inherent line capacitance. Under light-load or no-load conditions, this capacitive effect leads to voltage rise at the receiving end and substations.
High voltage shunt reactors are connected in parallel to the power system to absorb reactive power and provide inductive compensation. Their main functions include:
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Absorbing excess capacitive reactive power generated by transmission lines
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Limiting overvoltage during light-load or no-load operation
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Stabilizing busbar and line voltage levels
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Reducing insulation stress on transformers and switchgear
By providing continuous inductive reactive power absorption, shunt reactors help maintain voltage within permissible limits and improve overall system reliability.
Operating Principle
A high voltage shunt reactor operates based on the inductive reactance of its core and windings. When connected in parallel to the power system, the reactor behaves as an inductive load.
Under AC voltage, the reactor draws inductive current and absorbs reactive power, which counteracts the capacitive reactive power generated by transmission lines. The absorbed reactive power is approximately proportional to the square of the system voltage. As a result, when system voltage increases, the reactive power absorbed by the shunt reactor increases automatically, making it particularly effective for overvoltage suppression.
From a system perspective, a shunt reactor functions as a continuously connected reactive power compensation device with stable and predictable performance.
Typical Application Scenarios
Long-Distance Overhead Transmission Lines
In long EHV and UHV overhead lines, especially at voltage levels of 220 kV, 500 kV, and above, shunt reactors are commonly installed at the receiving end or in substations to compensate for line charging reactive power and prevent voltage rise.
High Voltage Cable Systems
High voltage and extra-high voltage cables generate much higher capacitive reactive power than overhead lines. Shunt reactors are therefore essential in urban power grids, underground cable networks, and submarine cable projects to control voltage and reduce charging current.
Substation Bus Voltage Control
In large substations, high voltage shunt reactors are used in combination with capacitor banks, SVC, or STATCOM systems. They provide base-level reactive power absorption, while fast-acting devices handle dynamic voltage regulation.
Renewable Energy Integration
In power systems with large-scale wind or solar generation, operating conditions change frequently. Shunt reactors help absorb surplus reactive power during low active power output periods, supporting voltage stability and reducing the burden on dynamic compensation equipment.
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