Measuring residual current. How do I know what RCD to fit?

[Inteificio]

"You can measure the earth leakage by using an earth leakage clamp meter and clamping all the phases (and neutral if there is one) simultaneously."

That is the kind of thing I was looking for, I just can't find one!


All the kit I can find clamps only the earth (which I would assume is only useful for single phase with no potential parallel paths).



"or proper training coupled with an effective preventive maintainence program....

what do you think?" That would of course be prefered, but sometimes we have to be realistic


As ever I am explaining things poorly and only giving half this info to try and keep the conversation on track. e.g. discussing whether RCDs are the best solution is irrelevant, the boss wants them in, they are going. discussing whether feeding one machine of the next is a good idea, we all know it's- the boss wants it that way so its being done like that.

I really do just need help on the bit i asked for.

I'm wanting something like Marvo described. Does anyone know where to get one, or who makes them?

Thanks,

 

[GMES]

Where is the factory in question, I only ask because there are a lot of very knowledgeable guys on here and maybe would be willing to design the system for you, don't know how much that would cost your boss but it will be cheaper than lost production due to you designing it wrong.

 

[GLENNSPARK]

........

 

[Inteificio]

Why are they on plugs and sockets? Factory machinery is much safer if it's fixed and hard wired.

Most of the equipment will be hard wired. Some parts of the production line get changed, they will be on plugs/sockets


The boss only wants them until the day the first one trips.

I know, hence wanting that not to happen unless it is stopping someone getting a shock


It isn't the job of an electrical designer to prevent or protect against reckless or negligent behavior or willful damage by the machine operator.

Designs have to take into account usage. The usage here dictates much higher standards of safety. Let me cite an example of retard. They want to use a labeller on a production line. So some idiot runs an extension lead across the floor. Some other idiot runs a POWERED pallet truck over it. It sticks on the wire, so they rev the motor and grind down to live. The metal pallet truck then went live. Due to my insistence that socket was protected by an RCD and no injury was caused. So hiring intelligent people would be preferred, but if you are dealing with retards, you have to take extra care. It's like designing electrics in a farm, this place is populated by large dumb animals who do not understand electricity.

 

[GLENNSPARK]

Why are they on plugs and sockets? Factory machinery is much safer if it's fixed and hard wired.


The boss only wants them until the day the first one trips.


It isn't the job of an electrical designer to prevent or protect against reckless or negligent behavior or willful damage by the machine operator.

some plugs are interlocked...by means of the isolator switch...

 

[Geoffsd]

All the kit I can find clamps only the earth (which I would assume is only useful for single phase with no potential parallel paths).


I'm wanting something like Marvo described. Does anyone know where to get one, or who makes them?

https://www.google.co.uk/search?q=e...0j7&sourceid=chrome&espv=2&es_sm=122&ie=UTF-8

I think you need to read how to operate them.

They are Earth Leakage clamp meters.
They measure residual current.

 

[GLENNSPARK]

Hi,

I have been tasked with rewiring most of the machines in a factory.
Due to the age of the equipment and usage I believe residual current protection is a good idea.

This presents an issue with how they want them wired.

Currently we have cables hanging from the ceiling at multiple points of the production line.
The want rid of this and want each machine in the production line to power the next.

My idea is to fit a dist board at one end and feed them off each other.

The only issue I have is what do I rate the RCD as?

The easy approach is to fit a 30mA RCD as the incomer and feed everything off individual mccbs.

However I do not know if these machines will cause nuisance tripping.


So the short version of this question is how can I measure the residual current on a 3 phase machine?

I've seen a PAT tester that could do single phase, but nothing for 3.

At the moment, the best idea I have (which sucks) is to get a settable RCD and keep reducing the current until it trips. This obviously does not take in to account any fluctuations in the device!

So do any of the sparks know how to do this properly or have any advice to offer?

Thanks,

incidentally for testing 3 phase equipment you need plugs that are wired internally...both in star...and delta....depending on whether or not a neutral pin has been provided.....dont forget that a pat tester measures all live conductors to earth on IR....

 

[trev]

Sorry but that's just too good to resist.
Those familiar with my sense of humour will know what I'm getting at

 

[Inteificio]

very witty Trev.

Those who know my sense of humour will know what I'm getting at. :bucktooth:

 

[GMES]

I take it #22 is not an option

 

[trev]

very witty Trev.

Those who know my sense of humour will know what I'm getting at. :bucktooth:

Biff! Can I borrow one of your epic fail pics please.

 

[Marvo]

"You can measure the earth leakage by using an earth leakage clamp meter and clamping all the phases (and neutral if there is one) simultaneously."

That is the kind of thing I was looking for, I just can't find one!

You can do this with any earth leakage clamp meter.

http://www.test-meter.co.uk/earth-leakage-clamp-meter/

 

[Des 56]

Breaking news
Fork truck runs over extension lead


"Unfortunately, just one of those things we can't protect against"

I just wish there was some way we could

 

[Inteificio]

You can do this with any earth leakage clamp meter.

That is the obvious thing I was clearly overlooking.
Was just looking at the instructions and clicked.

I will now slowly walk away feeling daft.

 

[mechelec]

If you are being told to fit RCD protection use something like this

Earth Leakage Relays

fit one for each machine on it own dedicated feed (if required) and set to maximum setting (30A) and maximum time delay. You will have fulfilled the instruction you have been given and shouldn't get nuisance tripping.

 

[Inteificio]

I take it #22 is not an option

Thanks for the offer, but I won't design it wrong...probably.

 

[Jaxo]

So if I fit an RCD its ok to wire my factory in extension leads ?

 

[Plonker 3]

Wow lots of questions at once.

Reason for RCDs, many.
For a quick answer.
These will be fed off plugs and sockets, regs indicates RCD requirement.
Boss wants RCDs.
Operators are a f£$^%ing liability and are so reckless with equipment everything in this factory needs RCD protection.
No reason not to add additional safety, if something is designed correctly, it won't cause an issue, but stop an accident.

"and i smell a cascading feeds epic here as well..." - Each piece of equipment will have it's own dedicated feed. Not sure what you meant though, so care to expand?

"What happens when one machine packs up, it takes out another 3 or 4 or whatever? " That's a good thing. If one item on the production line has an electrical fault the production line stops.


Des, I know little about mining, so your references are lost on me.
Basically a packing machine. Main boxer -> conveyor -> metal detector -> conveyor -> weigher -> LS.


RCDs are going in, no choice on that.
I need to know how to design to avoid nuisance trips.

So what does he suggest you do?

 

[Inteificio]

"So if I fit an RCD its ok to wire my factory in extension leads ?"

Clearly not, however if you have to deal with stupid people it means they are less likely to be able to hurt themselves.


"So what does he suggest you do?" - He is a mechanical engineer.

 

[Plonker 3]

"So what does he suggest you do?" - He is a mechanical engineer.

So why is he not listening to your professional opinion?