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Oil-immersed Reactors

Shunt Reactors 

Shunt reactors are used to increase the grid stability and to maintain an economically acceptable level of insulation on networks with long transmission lines between power plants and consumption areas, especially if these lines are low loaded or buried.

Indeed, shunt reactors compensate the capacitive load of energy transmission lines and are adequate solutions for:

maintaining an acceptable voltage whatever the load

limiting transient over voltages induced by switching or sudden load decrease

decreasing line losses by capacitive current reduction

Alstom Grid's know-how and experience in the field of shunt reactors with air-gap cores magnetic circuits, provides our reactors with low vibration and noise levels. Our latest generation tools for the design of shunt reactors allows optimized design for magnetic field distribution that provides safe behaviour.

Shunt reactors can be single- or three-phase according to your requirements. Our references include single-phase units up to 800 kV - 110 MVAr and 400 kV - 125 MVAr. We have also supplied 275 kV - 250 MVAr three-phase units that are currently in operation on all five continents.

Réactance série 400kV 2640 MVA partie active

Smoothing reactors 

Dedicated to HVDC transmission, smoothing reactors are used to reduce the flow of harmonic currents and transient overcurrents in the DC system thanks to their two functions:

  • Compensate voltage ripple at the 12-pulse converter bridge
  • Decrease the short circuit current in the DC link

With insulation principles based on the same special design as a transformer, Alstom Grid oil-filled smoothing reactors offer a low level of electromagnetic radiation outside the tank.

Smoothing reactors benefit from the same measures as the HVDC converter transformers to ensure that they will withstand short-circuit stresses. The clamping structure of the active part is reinforced in order to conform to these requirements.

Shunt Reactor 765kV Hydro Quebec

Series Reactors 

Series reactors are used in line series connections as current limiting devices to reduce fault currents to the required levels. According to your needs, reactors are completely customisable and available as single phase or three-phase and their construction can be unshielded, magnetically shielded or non-magnetically shielded. Alstom Grid is strong-experienced in this domain having supplied series reactors to transmission lines with throughput ratings up to and over 2000 MVAr.

Earthing reactors and transformers 

Earthing reactors provide a solution for limiting both short-circuit currents and the increase of voltage in the healthy phases when a line fault occurs.

When the neutral point is not accessible in the transformer, an artificial neutral can be created by means of an earthing transformer, which consists generally of a zig-zag winding and is connected between the main transformer and the reactor.

Smoothing reactor