4 Pole Breaker

As always, it will depend on a variety of factors not in evidence. The primary factor is if anything can be wye wired (4 pole) instead of delta wired (3 pole). Hire an engineer or liscensed electrician for a proper authorized answer. Do not just go by my or anyone else's answer here. We have no authority.

i have only come across 4-pole breakers when the system has two alternative sources and, in the event of power failure from the mains, change-over to the standby generator is done. In such a case, it is a good practice to isolate the neutral also.

However, as Redfred says, you should check out many things, including the local legislation which may have something to say on this,

British Standard 7671 covers it.

Hi

3 pole and 4 pole circuit breakers are also of different type

like neutral with over loading protection or wihtout over loading protection

like neutral has same short circuit breaking capacity or different one but try to have a circuit breaker that has all 4 poles identical, it is advantages in the case when one of the pole of the device will get damage, and it also provide isolation from neutral voltage,

regards

Divyesh patel

A. GROUND FAULT PROTECTION OF A DOUBLE-ENDED SYSTEM

1) Careful evaluation has to be done as to whether circuit breakers having three-pole plus neutral link can be used or four-pole breakers are required.

2) If unrestricted ground fault protection is fitted to the transformer neutral, then the bus section circuit breaker should have 4-poles and preferably incomer circuit breakers should also have 4-poles. It is because;

i. Uncleared ground fault located at the load side of a feeder have two return paths. As an example, a ground fault on a feeder at the bus section "A" will have a current return path in both the incomers, thus tripping both.

ii. The sensitivity of the unrestricted ground fault relay is reduced due to the split current paths.

The use of four pole or three pole CB will depend on your system protection and system configuration.

Normally in 3phase with neutral we just use 3pole CB but if application of 3pole will affect the operation of your protective relay then we can use 4pole CB. Proper evaluation and engineering judgement shall need to apply.

kindly illustrate the difference between 3 pole circuit breaker with 4 pole