Synchronous condenser

Synchronous condenser installation at Templestowe substation, Melbourne, Victoria, Australia. Built by ASEA in 1966, the unit is hydrogen cooled and capable of three phase power at 125 MVA.

In electrical engineering, a synchronous condenser (sometimes called a syncon, synchronous capacitor or synchronous compensator) is a DC-excited synchronous motor, whose shaft is not connected to anything but spins freely.[1] Its purpose is not to convert electric power to mechanical power or vice versa, but to adjust conditions on the electric power transmission grid. Its field is controlled by a voltage regulator to either generate or absorb reactive power as needed to adjust the grid's voltage, or to improve power factor. The condenser’s installation and operation are identical to large electric motors and generators (some generators are actually designed to be able to operate as synchronous condensers with the prime mover disconnected[2]).

Increasing the device's field excitation results in its furnishing reactive power (measured in units of var) to the system. Its principal advantage is the ease with which the amount of correction can be adjusted.

Synchronous condensers are an alternative to capacitor banks and static VAR compensators for power-factor correction in power grids.[3] One advantage is that the amount of reactive power from a synchronous condenser can be continuously adjusted. Reactive power from a capacitor bank decreases when grid voltage decreases while the reactive power from a synchronous condenser inherently increases as voltage decreases.[1] Additionally, synchronous condensers are more tolerant of power fluctuations and severe drops in voltage.[3] However, synchronous machines have higher energy losses than static capacitor banks.[1]

Most synchronous condensers connected to electrical grids are rated between 20 MVAR (megavar) and 200 MVAR and many are hydrogen cooled. There is no explosion hazard as long as the hydrogen concentration is maintained above 70%, typically above 91%.[4] A syncon can be 8 metres long and 5 meters tall, weighing 170 tonnes.[5]

Synchronous condensers also help stabilize grids. The inertial response of the machine and its inductance can help stabilize a power system during rapid fluctuations of loads such as those created by short circuits or electric arc furnaces. For this reason, large installations of synchronous condensers are sometimes used in association with high-voltage direct current converter stations to supply reactive power to the alternating current grid. Synchronous condensers are also finding use in facilitating the switchover between power grids[6] and providing power grid stabilization as turbine-based power generators are replaced with solar and wind energy.[7][3]

  1. ^ a b c B. M. Weedy, Electric Power Systems Second Edition, John Wiley and Sons, London, 1972, ISBN 0-471-92445-8 page 149
  2. ^ Kundur 1994, p. 638.
  3. ^ a b c Fairley, Peter (2015-07-24). "Zombie Coal Plants Reanimated to Stabilize the Grid". IEEE Spectrum. IEEE. Retrieved 2023-11-13.
  4. ^ "Synchronous Condenser | AC Motors | Electronics Textbook".
  5. ^ Parkinson, Giles (25 October 2021). "Wind and solar limits relaxed after four big spinning machines installed". RenewEconomy. Archived from the original on 26 October 2021.
  6. ^ Fairley, Peter (2023-11-13). "To Free The Baltic Grid, Old Technology Is New Again". IEEE Spectrum. IEEE. Retrieved 2023-11-13.
  7. ^ "GE synchronous condensers – 100 years on". Modern Power Systems. 2020-02-12. Retrieved 2023-11-13.