GENERAL APPLICATIONS

The Series Reactors generally find application in medium and high voltage capacitor installation under the following circumstances :

The short circuit level of the network is high and as a result switching in surges of capacitor banks are high. Example: Capacitors near a large generating or receiving station.

A number of capacitor banks operate in parallel across a common bus. A newly switched in capacitor bank draws a heavy current from an already charged bank and the mains.

The network contains high arcing frequencies and/or is subjected to sudden voltage surges (Switching or lightning)

In modern circuits with large thyristor controls, there is a great deal of generation of harmonics for which a capacitor bank forms a low or very low impedance path. To prevent the flow of the harmonics into the bank a filter circuit containing a series reactor is quite often necessary.

A properly designed series reactor- capacitor installation can act as a tuned filter circuit. By selecting the tuning, one can pass to ground the entire contents of that particular harmonic and prevent its spread further into computer systems or telecommunication systems. This has to be done carefully. In advanced countries, laws are being enacted to make this feature compulsory.

Normally a 6% series reactance (6% of the capacitor bank in KVAr) is used. Where warranted, a 3% or a 1% Series Reactor is also specified. There are number of instances where a series reactor can entirely be dispensed with.

The advantages of a series reactor are that it limits the surge currents and also high frequency currents as under(3) and (5) above, into a capacitor bank. This protects the capacitor bank and reduces the burden on the switchgear controlling the capacitor bank.