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Case Study

Kallang Basin

SVCs for dynamic voltage control of 230 kV cable network

Since 1988, the Public Utilities Board (PUB) of Singapore has operated two static var compensators (SVC) of the thyristor-controlled reactor type (TCR) in its 230 kV cable transmission network. The TCRs, one rated at 100 Mvar located to Kallang Basin s/s and one rated at 50 Mvar and located to Labrador s/s, were supplied by Hitachi Energy on a turnkey basis.

The Singapore 230 kV transmission network is 100% cablebased, with heavy reactive power generation within the system as a consequence. The subsequent need for reactive power absorption is considerable, as well as complex, due to the varations in the reactive power balance during varying load conditions ranging in between peak load and light load.

Before the advent of TCR, the need for reactive power absorp­tion was solved by extensive incorporating of shunt reactors at vital points in the network, fixed as well as mechanically switched. This had not been fully satisfactory in certain respects, however, and mainly the following:

− A need for frequent switching of reactors, with the associated switching transients, circuit breaker wear, and requirements for maintenance of the breakers.
− Limited dynamic capability in situations where fast operation of reactors would be advantageous from a system point of view.
− Only stepwise switching of reactive power was possible, which did not admit optimum utilization of the power system with respect to losses as well as active power carrying capability. 

Main data  
System    SVC
Commissioning year    1985
Technical data  Labrador Kallang Basin 
Controlled voltage  230 kV 230 kV
SVC rating 50 Mvar (inductive) 100 Mvar (inductive)
Control system  Three-phase voltage control by means of a voltage regulator
Thyristor valves  Water-cooled thyristor valves with outdoor dry-type air/water exchanger