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Increase of power transmission capacity in South Africa-Zimbabwe interconnection by means of SVC

Since 1995, a Static Var Compensator (SVC) rated at 100 Mvar inductive to 200 Mvar capacitive at 330 kV supplied by Hitachi Energy has been operating in the Matimba-Insukamini 600 MW power interconnecting corridor between South Africa and Zimbabwe. It is located at the ZESA Insukamini 330 kV substation in Zimbabwe, close to the coupling point for the 400 kV interconnection to South Africa.This 405 km long line forms part of an AC connection running in parallel with the Cahora Bassa HVDC link. In 2014 an upgrade of the SVC was performed.

The purpose of the compensator is to provide high speed dynamic voltage control during certain system loading and outage conditions. The single 400 kV interconnection between Matimba and Insukamini is relatively weak, and unless proper measures are taken, poorly damped, low frequency (<0,5 Hz) active power oscillations tend to appear between South Africa and Zimbabwe. The SVC is equipped with a Power Oscillation Damper (POD) in order to mitigate these power oscillations.

With the SVC in operation, stability and power transfer margins have been increased by approximately 150 MW in the existing power corridor

Main data
System SVC/Upgrade
Commissioning year 1994/2012
 Controlled voltage  330 kV
 SVC rating   100 Mvar inductive to 200 Mvar capacitive. 
 Control system   Three-phase voltage control by means of a closed-looped voltage regulator. Strategy selection includes Power Oscillation Damping. 
 Thyristor valves   Water-cooled three-phase valves with indirect light triggering.

Insukamini: SVC to increase power transmission capacity