a static VAR compensator is a set of electrical devices for providing fast-acting reactive power on high voltage electricity transmission networks svcs are part of the flexible AC transmission system device family regulating voltage power factor harmonics and stabilizing the system unlike a synchronous condenser which is a rotating electrical machine a static VAR compensator has no significant moving Parts other than internal switch gear prior to the invention of the SVC power factor compensation was The Preserve of large rotating machines such as synchronous condensers or switched capacitor Banks the SVC is an automated impedance matching device designed to bring the system closer to Unity power factor svcs are used in two main situations connected to the power system to regulate the transmission voltage transmission SVC connected near large industrial loads to improve power quality in industrial SVC in transmission applications the SVC is used to regulate the grid voltage if the power system's reactive load is capacitive leading the SVC will use thyristor-controlled reactors to consume bars from the system lowering the system voltage under inductive lagging conditions the capacitor banks are automatically switched in thus providing a higher system voltage by connecting the thyristor-controlled reactor which is continuously variable along with a capacitor Bank step the net result is continuously variable leading or lagging power in industrial applications svcs are typically placed near high and rapidly varying loads such as Arc furnaces where they can smooth flicker voltage typically an SVC comprises one or more Banks of fixed or switched shunt capacitors or reactors of which at least one bank is Switched by thyristors elements which may be used to make an SV AC typically include thyristor-controlled reactor TCR where the reactor may be air or iron cord thyristor switched capacitor TSC harmonic filter s mechanically switched capacitors or reactors switched by a circuit breaker by means of phase angle modulation switched by the thyristors the reactor may be variably switched into the circuit and so provide a continuously variable mvar injection or absorption to the electrical Network in this configuration coarse voltage control is provided by the capacitors the thyristor-controlled reactor is to provide smooth control smoother control and more flexibility can be provided with thyristor-controlled capacitor switching the thyristors are electronically controlled thyristors like all semiconductors generate heat and deionized water is commonly used to cool them chopping reactive load into the circuit in this manner injects under desirable odd order harmonics and so Banks of high power filters are usually provided to smooth the waveform since the filters themselves are capacitive they also export mvars to the power system more complex arrangements are practical where precise voltage regulation is required voltage regulation is provided by means of a closed-loop controller remote supervisory control and manual adjustment of the voltage set point are also common the main advantage of svcs over simple mechanically switched compensation schemes is their near-instantaneous response to changes in the system voltage for this reason they are often operated at close to their zero point in order to maximize the reactive power correction they can rapidly provide when required they are in general cheaper higher capacity faster and more reliable than Dynamic compensation schemes such as synchronous condensers however static VAR compensators are more expensive than mechanically switched capacitors so many system operators use a combination of the two technologies sometimes in the same installation use using the static VAR compensator to provide support for fast changes and the mechanically switched capacitors to provide steady state bars