Which connection is better for Capacitor Bank Star or Delta?

Most of the time capacitor bank is connected in Delta, but it is also connected in Star for some applications. Now the question arises when the Capacitor bank is connected in Star and when connected in Delta? Which connection is better for Capacitor Bank Star or Delta? In this article, you will find the advantages and disadvantages of both star-connected capacitor banks and delta-connected capacitor banks.

The capacitor bank is used for power factor correction. For the correction of the power factor in the three-phase system, a three-phase capacitor bank is needed which may be star-connected or delta-connected.

Delta connected Capacitor Bank

Delta-connected capacitor banks are generally used for low to medium voltage. The delta-connected capacitor bank can be used for high voltage but sometimes it is not possible because in the delta connection, the full phase voltage is applied across each capacitor whereas in the star connection root 3 times less than phase voltage is applied across the capacitor.

So you may understand if we use delta delta-connected capacitor bank at high voltage, the voltage rating of the capacitor should be high. So high voltage capacitor manufacturing is costly and sometimes impossible.

Advantages of Delta Connection in a Capacitor Bank

1. The KVAR generated by the capacitor is proportional to the square of the applied voltage which means if the voltage is higher the KVAR also be higher. So the delta-connected capacitor bank provides more KVAR compared to the star-connected capacitor bank because, in a star connection, less voltage is applied across the capacitor than the delta connection.

2. Delta connected Capacitor bank can circulate the harmonic current, so it can reduce the harmonic effect in an electrical system.

3. Delta-connected capacitor bank provides a balanced capacitance to each phase of the electrical system and also maintains a balanced voltage.

4. If a capacitor cell in one phase fails inside the capacitor bank, the voltage across each phase remains the same, only KVAR is dropped.

Disadvantage of Delta Connection in a Capacitor Bank

1. The only disadvantage of the delta-connected capacitor bank is, that the voltage stress across each capacitor is high which reduces the life of the capacitor and it may not be used for high-voltage applications.

Star connected Capacitor Bank

The star-connected capacitor bank is used for medium to high-voltage applications. In star connection, the voltage across each capacitor is root 3 times lesser than the phase voltage, so the voltage stress across the capacitors is low even in high voltage applications. There are two types of star connections in the capacitor bank.

1. Grounded Star Connection
2. Ungrounded star Connection

In a grounded star connection, the neutral point is connected to the earth or it is grounded but in an ungrounded star connection, the neutral point is isolated from the earth or ground.

Advantages of Star Connected Capacitor Bank

1. The star-connected capacitor bank is simple in connection.

2. The voltage stress across each capacitor is less, so the life of the capacitors is high.

Disadvantages of Star Connected Capacitor Bank

1. Star-connected capacitor bank provides less KVAR than a delta-connected capacitor bank because the voltage across the capacitor is less.

2. Star connected capacitor bank cannot circulate the harmonic current in an electrical system.

3. The ungrounded star-connected capacitor bank cannot maintain the balance voltage and cannot provide the balance capacitance.

4. If a capacitor cell in one phase is failed, an unbalanced voltage occurs in the electrical system.

Conclusion

You may understand the delta-connected capacitor bank provides more advantages and benefits than the star-connected capacitor bank. So delta connection is better for the capacitor bank. For these reasons, capacitor banks are mostly delta-connected.


Read Also:

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• Can use of Capacitor or Power Saver device reduce our Electricity Bill?
• [Exact] Difference between Coupling Capacitor and Bypass Capacitor

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