Panel problem

[rizla1990]

Hi guys, after your thoughts on a problem i have on a panel at a sand quarry feeding the main sand pumps and de-watering screens.
The panels main isolator is tripping at random times, it can run for an hour with no problems then it will blow. There are 2 rcd's feeding the pumps and neither of them blow however the main switch does. I can start any part of the plant in any order and no problems , it will sometimes blow as soon as you turn it on and other times it will all run for 10 mins or maybe 2hours. Im thinking it could be a faulty isolator? Anyone with any ideas? Thanks in advance
Rhys

 

[westward10]

Is the isolator a mccb.

 

[rizla1990]

This is the isolator. There is no info visable on it. Allthough it says 'trip' on it.

View attachment 35449

View attachment 35450

View attachment 35451

View attachment 35452

 

[westward10]

What is the writing by the switch activator.

 

[rizla1990]

Its the make of the switch, there is no info on that sticker other than 'trip' on the top right hand side. I will be going there tomorrow so i will be able to look closer. Im just a bit miffed as to why that is tripping and the 2 rcd's arent

 

[westward10]

An rcd, assuming it is only an rcd will not trip with overcurrent.

 

[LeeH]

Looks the the isolator is a shunt trip, as I can see a CT at the bottom of panel under the isolator.

The earth leakage controller is probably that unit that has 2 red wires to it from the isolator.

Are you sure the 2 motors have RCDs as I cannot see any.

But I'm looking on my phone.

I presume you have done your basic tests on the field wiring and motors...

What was the IR results?

 

[LeeH]

I'll play devils advocate here and say no IR has been done, the motors are starting to deteriorate and the leakage is being detected and the isolator is being forced closed and you have little experience in this field.

Tin hat on and I'm fully prepared for a flaming.

 

[Bobster]

I can't see any individual RCD protection on the MCCBs I presume are installed to protect the pumps. Although under M&Q regs they do have to be protected by a 30ma rated RCD, or another form of leakage detection.

The main isolator does look to include a shunt trip, the coil at the bottom of the panel would detect an imbalance between all phases and earth.

Likely to be just the motor insulation degrading. Two large motors will have fairly substantial earth leakage when combined, especially if they are old or in not a good condition (full of dust etc..)

Get some tests done, and let us know the results. I know what my initial first though it having plenty of first hand experience dealing with pumps in quarries, an it will probably come down to poor design.

 

[Des 56]

The comments on the lack of Rcds.
Have I got the wrong images or perhaps I'm getting senile its not been used the panel looks like its only just left the factory

 

[rizla1990]

I haven't had time to be there to do any tests yet. It was a call yesterday, went there this morning, turned it all on and guess what, no problems. Stayed there an hour and all was fine. So i left and lo and behold a couple of hours later , phonecall to say the problem had returned. I was unable to return today so told them I would be back tomorrow. The plant is only 10 months old so id hope the motor insulation would not have degraded that bad that quick?

 

[rizla1990]

The comments on the lack of Rcds.
Have I got the wrong images or perhaps I'm getting senile its not been used the panel looks like its only just left the factory

This is an old photo of the panel before installation, it was the only photo i had. Sorry.

Also my bad for the rcd comment, i meant the mccbs!

 

[Bobster]

What size are the motors? You realise they have a natural amount of leakage?

 

[rizla1990]

What size are the motors? You realise they have a natural amount of leakage?

Yes i am aware of natural leakage. As for the size I can't remember but i have a feeling they were a 30kw and 22 kw

 

[Bobster]

Well, I'd take your clamp meter with you to measure imbalance.

You could possibly measure what the ct is producing and measure that with a multimeter .

 

[rizla1990]

Well, I'd take your clamp meter with you to measure imbalance.

You could possibly measure what the ct is producing and measure that with a multimeter .

Thanks for the help, i am rather new to the commerical side of things so am still learning a lot as i go along. Will let you know what i find

 

[Bobster]

Quarry work is hardly commercial. There is a lot more than bs7671 you need to be aware of here. A lot is also statute law whereas bs7671 is not. So make sure you are absolutely sure you're meeting all requirements. As if it goes wrong you will soon be in a world of excrement.

Also worth a note no insurance will cover you if you've departed from some of these standards.

 

[Darkwood]

Are those the schematics at the bottom, you need to use them to trace the shunt trip circuit and what it is operated by, usually but not exclusively they look for a N/C loop and will trip the main switch if opened, it can be many things causing the intermitant tripping from corroded control connections, guard limits, O/L auxillaries etc etc.
You need to review and understand the wiring schematics, if unavailable it comes down to tracing and interpreting how the control system operates, failure to approach this the correct way will just cause wasted time and further confusion.
Judging by the colour code of the cable, the control will be AC possible 110v or 230v although the TX is too small to confirm.

 

[Darkwood]

Ill second Rob on this, in asking the question you really should be supervised when doing this work, this is not something you can take on when your short of other work, you need alot of experience in this sector or like Rob says, you may end up in deep doodi's, I did 15yrs in control and machinery before I classed myself as competent enough to hit it on my own, although i do cover a large variation of machinery, I'm still on a big learning curve even now after 28yrs.

 

[LeeH]

Like I said the shunt is clearly visible, upper right of the isolator near the 3 phase bus.

It may just need commissioning correctly.

 

[Darkwood]

Like I said the shunt is clearly visible, upper right of the isolator near the 3 phase bus.

It may just need commissioning correctly.

It is likely to be a shunt but to be open minded here, it may be one of many trips that can be fitted hence I motioned to look at the schematics which seem to be sat in the bottom.

 

[LeeH]

It is likely to be a shunt but to be open minded here, it may be one of many trips that can be fitted hence I motioned to look at the schematics which seem to be sat in the bottom.

With the CT connected (you can see the grey flex both ends) to the unit it has to be an RCD?

 

[Darkwood]

Bloody hell..had to expand that to super size to see it, yes it does look like the unit to the left of the 4 motor overloads is an eartheakage monitor, that been the case the red wire on the main switch will be as I suggested before just looking for a closed loop or it won't hold.
Are you veiwing this on a 42inch screen or what ?

 

[LeeH]

iPhone...

 

[Antony1]

The earth leakage relay is probably adjustable and probably didn't get set up right from the start, it may need adjusting now the motors are aging

 

[Bobster]

bare in mind that may be feasible in an ordinary installation.

This is supplying quarry pumping equipment

 

[rizla1990]

The earth leakage relay is probably adjustable and probably didn't get set up right from the start, it may need adjusting now the motors are aging

Sorry guys, forgot to let you know, turns out antony you are spot on, it was set quite low 0.5ma and 0.5 time delay. It has worked like this for around 10 months no problems. Have turned up to 1.5ma and 1.5 time delay and all is good. Thanks again everyone for the help

 

[Bobster]

1.5ma? You sure?

 

[LeeH]

Normally there is a multiplier. x1 x10 etc so maybe he's confused.

 

[Bobster]

Normally there is a multiplier. x1 x10 etc so maybe he's confused.

Exactly my thinking, guessing it's 150ma, if so, just broken M&Q regs.

 

[rizla1990]

1.5ma? You sure?

Maybe there was a x on it, the scale was 0.5-2.5 on both

 

[LeeH]

Could have been just a kiss.

 

[davesparks]

Sorry guys, forgot to let you know, turns out antony you are spot on, it was set quite low 0.5ma and 0.5 time delay. It has worked like this for around 10 months no problems. Have turned up to 1.5ma and 1.5 time delay and all is good. Thanks again everyone for the help

Was this a random hit and hope job or did you work out the correct settings for this particular system?

 

[rizla1990]

Was this a random hit and hope job or did you work out the correct settings for this particular system?

I had a second opinion of a panel builder friend of mine, he could not see the point of this particular circuit in the wiring diagram, he has made panels and installed them in almost identical situations so he agreed that i should try turning it up first otherwise to bypass it but as it worked by turning it up its all good

 

[LeeH]

Then he's a tard.

 

[rizla1990]

Then he's a tard.

That may be your opinion. This forum seems to be full of people that just want to criticise everything everyone says . Suppose all of you guys have been perfect since day1 on the job! Never had to ask for help!?
Well i will not be wasting any more time on here.

 

[Bobster]

I guess the panel builder doesn't know much about M&Q regs, why would he.

Best hope nothing goes wrong, as on your head be it.

Just to add, M&Q is statute law an has teeth unlike bs7671

 

[davesparks]

I had a second opinion of a panel builder friend of mine, he could not see the point of this particular circuit in the wiring diagram, he has made panels and installed them in almost identical situations so he agreed that i should try turning it up first otherwise to bypass it but as it worked by turning it up its all good

There must be a point to it, otherwise it would not be there. Nobody will have put expensive components in to a panel for no good reason.

I can appreciate adjusting it as part of a fault finding process, but adjusting it permanently when you don't even know why it is there just makes no sense.

 

[Andy-1960]

The CT at the bottom of the panel looks like a core balanced transformer to me, therefore the entire system is being monitored for earth leakage, this is why the isolator is tripping. Glad I'm not looking for the fault!!