Thursday, October 3, 2013

Why Three phase Capacitor banks connected in Delta?

Capacitor banks are used for improving PF of the system. It was very interesting to find out that all capacitor banks  are connected in Delta instead of star.

There are many advantages of connecting capacitor bank in Delta instead of Star connections , Same will be discussed as below:-

1. Lower Maintenance cost
In a delta connected capacitor if any cell out of three get faulty then KVAR of capacitor bank get dropped by 27% means capacitor will work in open delta connections. Now that faulty cell will be replaced very easily by just opening the leads. This way maintenance cost will be reduced considerably as cost of replacement of one cell is needed to be bear instead of whole capacitor.

For MCCB standards:-

2. Higher Efficiency
In Delta circuit Current is high in comparison to Star connections.  Which will leads to higher  high efficiency in case of Delta connections.

3. Higher capacitance

If you solve for delta and star connections and find out equivalent circuit then you will find out that capacitance of a delta bank is more than the equivalent capacitance of a series capacitor bank. So more capacitance means it will supply more reactive power will it supply & since capacitor bank's sole purpose is to supply reactive power, delta connection will serve better.

Capacitor banks rating is in KVAR as it is not Active power and it is known as reactive power.Shunt capacitor banks are mainly installed to provide capacitive reactive compensation/power factor correction.

Capacitor bank delta connections

The use of SCBs has increased because they are relatively inexpensive,easy and quick to install and can be deployed virtually anywhere in the network.

4. Voltage balancing in Capacitor bank: - By connecting capacitor banks in Delta, voltage unbalance can be avoided as in the case of star connected capacitor banks.

Capacitor bank connections in delta are shown as above.

IS 13925 (Part 4) : 2013
IEC 60871-4 : 1996
IEC 60871 are standards used for Capacitor banks

This Indian customary (Part 4) that is identical with IEC 60871-4 : 1996