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.
|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|