Compared to shunt reactors with a fixed rating, Variable Shunt Reactors provide several benefits to the operators. Customer values and applications of VSRs are as follows.
To reduce voltage spikes in the network resulting from switching in and out the Fixed Shunt Reactors; especially in networks with low short circuit power. Generally, switching Fixed Shunt Reactors in and out is a non-optimal compensation which leads to voltage steps and also wearing out the breakers. It is possible to avoid switching actions by using a VSR and regulate it to its minimum power tap position. VSRs reduce voltage jumps during switching operation.
In substations with SVC equipment and rotating phase compensators, the VSR has the capability to be coordinated with the SVC/phase compensators in order to maximize the dynamic capacity of the network during failure.
For wind park generation applications, a VSR may be used by the operator of the wind park to control reactive power fluctuations. An important difference between wind parks and conventional large generation is the fluctuating and unpredictable active power exchanges of the wind park to the main grid; these active power fluctuations cause in turn reactive power losses which are a serious concern regarding network operational security. Using Fixed Shunt Reactors require too many switching actions and the need for advanced control possibilities of SVC may not be needed. It is possible to reduce number of circuit breakers by having one VSR instead of two or more parallel fixed reactors. This will consequently cause reduction on maintenance work on breakers and space requirements.
VSRs are suitable to be used for seasonal load variations. At low loading condition the full MVAr rating is needed to maintain a stable voltage. As the load increases in the intermediate season the VSR acts to fine tune the voltage to the required level.
Daily load variation is another possible application of VSRs. The loading varies as a consequence of Economic Load Dispatch (ELD) and Optimal Power Flow (OPF) in the power system. For this reason there is a need for a more flexible compensation of the reactive power.
VSRs can also be used for voltage regulation at high voltage AC cables. AC cables generate much more reactive power per unit of length than overhead lines (almost 20 times more) and because of thermal constraints in the cables it is normally not possible to load them at SIL. Therefore there is a need for reactive power compensation to stabilize the voltage. At variable stationary loads, better fine-tuning of the voltage and consequently a better control of the network can be achieved using a VSR. VSRs are flexible to adapt with revisions in the network. The future load and generation pattern is not specified and the demand for reactive power compensation may change. To meet the new demand there is a possibility to regulate the VSR.
It is possible to adjust the reactive power consumption of a VSR during maintenance or a failure situation on another reactor.
In substations with SVC equipment and rotating phase compensators, the VSR has the capability to be coordinated with the SVC/phase compensators in order to maximize the dynamic capacity of the network during failure.
For wind park generation applications, a VSR may be used by the operator of the wind park to control reactive power fluctuations. An important difference between wind parks and conventional large generation is the fluctuating and unpredictable active power exchanges of the wind park to the main grid; these active power fluctuations cause in turn reactive power losses which are a serious concern regarding network operational security. Using Fixed Shunt Reactors require too many switching actions and the need for advanced control possibilities of SVC may not be needed. It is possible to reduce number of circuit breakers by having one VSR instead of two or more parallel fixed reactors. This will consequently cause reduction on maintenance work on breakers and space requirements.
VSRs are suitable to be used for seasonal load variations. At low loading condition the full MVAr rating is needed to maintain a stable voltage. As the load increases in the intermediate season the VSR acts to fine tune the voltage to the required level.
Daily load variation is another possible application of VSRs. The loading varies as a consequence of Economic Load Dispatch (ELD) and Optimal Power Flow (OPF) in the power system. For this reason there is a need for a more flexible compensation of the reactive power.
VSRs can also be used for voltage regulation at high voltage AC cables. AC cables generate much more reactive power per unit of length than overhead lines (almost 20 times more) and because of thermal constraints in the cables it is normally not possible to load them at SIL. Therefore there is a need for reactive power compensation to stabilize the voltage. At variable stationary loads, better fine-tuning of the voltage and consequently a better control of the network can be achieved using a VSR. VSRs are flexible to adapt with revisions in the network. The future load and generation pattern is not specified and the demand for reactive power compensation may change. To meet the new demand there is a possibility to regulate the VSR.
It is possible to adjust the reactive power consumption of a VSR during maintenance or a failure situation on another reactor.