Variable shunt reactor

air-insulated

Overview
Shunt reactors and series reactors are core components for stable AC grid operation. Shunt reactors provide reactive power compensation and overvoltage control under light-load conditions, while series reactors introduce controlled impedance in transmission paths to limit current and influence power flow.

Portfolio range

• Power ratings: from 10 MVAr up to 300 MVAr
• Voltage levels covered: from 25 kV to 800 kV
• Product types: fixed shunt reactors, variable shunt reactors (VSR), series reactors

Fixed vs. variable shunt reactors

• Fixed shunt reactor: constant reactive power compensation suited to predictable grid conditions
• Variable shunt reactor (VSR): flexible reactive compensation using on-load tap changer (OLTC), adapts to fluctuating loads and dynamic grid requirements

Fixed vs. variable shunt reactors — comparison (table)
Criteria | Fixed Shunt Reactors (FSR) | Variable Shunt Reactors (VSR)
Reactive power compensation | Constant compensation | Dynamic, adjustable compensation
Best suited for | Stable, predefined grid conditions | Fluctuating and dynamic grid conditions
Typical applications | Long overhead lines, stable transmission systems | Renewable integration, cable-dominated grids
Grid behavior | Predictable, steady load profiles | Variable generation and load patterns
Voltage control | Switching on/off | Stepwise, finely adjustable
Efficiency | High efficiency | Optimum efficiency across varying conditions
Losses | Fixed | Reduced losses at below-rated reactive power levels
Flexibility | Limited | High
Technology | Fixed rating, simple design | Tap changer technology enables adjustment
Investment | Lower initial cost | Moderate higher initial investment, higher operational value
Operational value | Proven, robust solution | Reliable technology, future-ready for modern grids

Shunt reactors in modern power systems
Shunt reactors mitigate overvoltage in long transmission corridors and cable-based infrastructure. They are typically installed at grid connection points, substations (busbars or line ends), or cable terminations to provide centralized reactive power compensation, especially under light-load or no-load conditions.

Shunt reactor configurations

• Single-phase and three-phase configurations: single-phase used for specific very-high-voltage cases, three-phase standard for utility-scale grids ≤550 kV
• Oil-immersed designs: strong insulation, efficient thermal management and long service life

Series reactors portfolio
Series reactors are installed in series with transmission lines or feeders to introduce controlled impedance. Typical functions include limiting short-circuit currents, protecting equipment, shaping power flow and balancing loads between parallel circuits.

Applications and use cases

• Substations: stabilize voltage and manage reactive power at busbars and line ends
• Utility deployments: grid expansion, reinforcement and modernization to reduce losses and improve efficiency
• Renewable integration: manage voltage fluctuations from wind and solar, particularly for long HVAC cable links and cable-dominated connections

Comparison shunt vs. series reactor — key points (table)
Feature | Shunt reactors | Series reactors
Primary function | Reactive power compensation and overvoltage control | Short-circuit current limitation and power flow control
Connection type | Connected in parallel (lines, cables, busbars) | Connected in series with transmission lines or feeders
Main applications | Long transmission lines, cables, substations, renewable integration | Short-circuit current limitation, load-flow control
Typical customers | Transmission and distribution utilities, renewable developers | Transmission utilities, industrial users
Key variants | Fixed and variable shunt reactors, single-phase and three-phase, oil-immersed designs | Line reactors, current-limiting reactors, smoothing reactors
Typical benefits | Voltage stability, reduced transmission losses, improved power quality | Improved system protection, controlled current levels, enhanced grid stability
Typical installation locations | Transmission substations, cable terminations, offshore wind grid connections | Substations, feeders, network interconnections

Key technical features and performance

• Voltage and power ratings: typically 25 kV to 800 kV and 10 MVAr to 300 MVAr
• Compact designs for space-constrained installations
• Options for low-loss and low-noise operation
• VSR regulation ranges up to ~80% using tap changer technology
• Digital monitoring and predictive maintenance options to enhance availability and lifecycle efficiency

Benefits for customers

• Stable grid operation and improved power quality via effective reactive power compensation
• Flexibility to adapt to evolving grid conditions and renewable generation variability
• Engineering and lifecycle services: consulting, system design, manufacturing, testing and long-term maintenance

Technical specifications

• Voltage levels: typical coverage 25 kV to 800 kV
• Power ratings: typical range 10 MVAr to 300 MVAr
• Product variants: Fixed Shunt Reactors (FSR), Variable Shunt Reactors (VSR), Series Reactors
• VSR regulation: on-load tap changer (OLTC) enabling dynamic adjustment; extended regulation ranges up to ~80%
• Configurations: single-phase (for specific very-high-voltage cases) and three-phase (standard ≤550 kV)
• Design options: oil-immersed for strong insulation and thermal management; compact designs for reduced footprint
• Functions: reactive power compensation, overvoltage mitigation, short-circuit current limitation, power flow control
• Typical applications: transmission substations, cable terminations, offshore wind connections, long HVAC cable systems, utility grid reinforcement
• Monitoring/maintenance: digital condition monitoring and predictive maintenance options to reduce lifecycle costs