4 pole Isolator on a 3 phase system

[Engineer54]

And our incomers were 3 pole with links. The reasoning being, switch the neutral and you remove one of the neutral earth paths. To break one of those links had to be a deliberate act.
There is the danger of closing the switch without the link fitted. But for the link to have been removed in the first place a responsible person would have authorised it and be accountable if not replaced.

The only time I’ve fitted 4 pole ACB’s was for stand by generators.

Sorry kid, we’re poles apart :yes:

Thanks for the kid quote, ....if only....lol!! :yes:


Now think about having Multiple 3 pole incomers from TX's and 3 pole bus couplers, all the TX neutrals commoned!!! How about having a faulty TX tripping out, but still having it's neutral being backfed even when it's out of service, well until someone actually goes and physically removes the neutral connection(s) anyway. ....So Yep, we sure are poles apart, all our switchboards are fully automatic both operationally and protection wise. When a supply needs to be fully isolated from the switchboard, we don't want to be messing around with a socket wrench or spanner to disconnect a neutral conductor, which in many cases could be several neutral conductors where parallel feeder supply's are involved!! No, i'll be definitely be sticking to the industry standard of 4 pole ACB's on main multi section switchboards. It's an absolute no brainer as far as i'm concerned...

 

[Knobhead]

Using REF both the supply and load VCB and ACB open under fault conditions. OK there could be a path through a faulted secondary winding but with the neutral being solidly bonded the current would be minimal.

From my days working under M&Q the neutral was never switched (if it was used at all). It was the same in the steel industry.
Most of the LV switchgear I installed were 3 pole + neutral links, it’s what I’m used to.

At the end of the day, we’ve both worked in different fields. I was brought up with 550V and 660V systems.
Neutral? What’s that?

DNO distribution LV boards don’t switch the neutral as this picture shows

BTW I do like these ABB SAIF pillars. They are designed for load break / fault make. Better than pulling fuses by hand.

 

[Engineer54]

Yes, but we're talking here about multiple TX neutrals that are on 3 pole ACB's for incomers and couplers. isolation of any of those commoned TX neutral becomes a real pain in the neck.... On our 4 pole system, the TX and switchboard bus bar neutrals never get to be commoned up, it is only present at the section(s) of the switchboard it's corresponding phase conductors are also present!! It's an all win, win arrangement over an identical but 3 pole arrangement!!

 

[Knobhead]

I’m used to multiple transformers having commoned neutrals. The biggest board having seven transformers.

It would be once in a blue moon the bus sections would be closed but the neutrals were never broken.

We’ll have to agree to disagree on this one.

 

[Tiny Spark]

I may be talking crap here and mixing up regs but a thought popped into my head this morning.

Is there not a reg somewhere that says something along the lines of if you have a 3 phase machine being worked on by unskilled staff the local isolation must switch all live conductors?

Sure i remember seeing something about it in the past but cant remember and my regs book is at work lol

 

[Smudge]

right or wrong on the breaking of the neutral, if the guys being an ar*e, knock him out.


All views and opinions are my own and do not reflect those of the entire smudge family.

 

[Engineer54]

We’ll have to agree to disagree on this one.

We certainly will have too on this one..... And i'm not understanding your reasoning for preferring 3 pole breakers on a multi TX supplied switchboard! at all.

 

[Knobhead]

Give me time to do the drawings and we'll meet on another playing field.

 

[Sparks1962]

This is a must... especially with this guy. I can guarentee that he will not want to do it though...

I'd get rid of him if I were you and get someone in who knows what they are talking about and can prove it!

 

[wade88]

Well he had a senior member with him, supervising i imagine, who did not bother to engage in conversation with me at all, nor did i want to stand there and attempt to belittle his colleague by suggesting he was a total fu*ktard so let them both get on with it. The elder chap appeared to be taking charge. It's the 5 year EICR being done, i shall await the results sheets, have a look and see what has been said.

Well for once i am glad its not me on the receiving end, feels quite nice being on the majority side for a change haha.

Thanks again chaps.

 

[Guest111]

part of the problem with some people seems to be understanding the term "live" conductor which they take as meaning a phase conductor whereas in the regs a live conductor actually means any conductor which is not an earth.

 

[Paultrim123321]

Think its shocking that someone has this attitude to a paying client. I am guessing this guy does not get much repeat work. For me, inspection and consulting services is not just about leaving a defect sheet but about liaising with the client and helping them to improve their system through communication.

 

[Knobhead]

Sorry Wade

E54 and I will cary on elsewhere

 

[wade88]

It's all good for me Tony, my post was answered in 15 minutes, every other discussion just makes for good reading and something else to learn. Do please carry on!