Live testing - could this be a Part P assessment failure?

[spark 68]

Hi Trev,

I don't think it makes much difference in reality, as the Zs of the circuit under test should have a negligable effect wrt the RCD tripping current.

IIRC there was an article in one of the wiring matters magazine a while back about this, I think it comes down to which ever way is the safest/most convenient.

 

[trev]

I think I've got all the egg wiped off my face now.
Ah, no there's a bit right there

 

[Engineer54]

Well from the start of this thread until post#12, i was amazed at the lack of understanding on the simple testing of an RCD device. All this nonsense about ''live working'' seems to be clouding the waters somewhat!! Live working and conducting required tests such as RCD and ELI, necessitates the circuit and the CU being live, there is no-way around it.

As for testing RCD's at the furthest point, that's acceptable for checking the RCD is functioning, but to conduct accurate parameter testing you really need to take those readings at the RCD terminals. Some manufactures state that there units need short length of wire to test from rather than directly on the terminals. But you can safely say that RCD test should be conducted at the CU and not in the field.


As for live working, just the use of your commonsense will normally suffice in the real world.... lol!!

 

[Chr!s]

This may help a little.


http://www.hse.gov.uk/pubns/indg354.pdf

Regards Chris

 

[spark 68]

Hi E54,

As for testing RCD's at the furthest point, that's acceptable for checking the RCD is functioning, but to conduct accurate parameter testing you really need to take those readings at the RCD terminals.

Whilst I usually prefer to test at the terminals, as this is more convenient for re-setting the device in question (auto testing aside), some scheme providers prefer you to test at a nearby socket (if and when this is possible re:split load boards) as this is deemed safer using a plug in lead.

The wiring matters article I referred to earlier (I will see if I can find it), seemed to suggest it makes little difference to the trip times recorded (or perhaps the worst case scenario), maybe different organisations have in the past, rightly or wrongly "their own way of testing"

Iam not disagreeing with anyone, as I said I prefer to test at the devices out going terminals.

 

[Farmelectrics]

no you havnt misunderstood nothing wrong with you testing rcbo at board make sure you have warning sign hanging from board and you dont leave area with board cover off do your live rcd tests and replace cover job done

 

[Engineer54]

Hi E54,

Whilst I usually prefer to test at the terminals, as this is more convenient for re-setting the device in question (auto testing aside), some scheme providers prefer you to test at a nearby socket (if and when this is possible re:split load boards) as this is deemed safer using a plug in lead.

The wiring matters article I referred to earlier (I will see if I can find it), seemed to suggest it makes little difference to the trip times recorded (or perhaps the worst case scenario), maybe different organisations have in the past, rightly or wrongly "their own way of testing"

Iam not disagreeing with anyone, as I said I prefer to test at the devices out going terminals.

Think you'll find if you check with the manufacturers themselves, will recommend testing at the outgoing terminals. These Scam providers often seem to try and make-up there own rules, about doing things. Make them sound official too, but they are anything but official, ....Just there own slant on things, that can often be at least confusing and at worst ...Wrong!!

 

[netblindpaul]

One other point.
HSE do not consider live testing as live working.
Live testing is live testing, an essential part of ensuring that electrical equipment is safe for continued use.
Live working is live working, disconnecting and making connections say on an energised circuit carrying current. This is very highly regulated and controlled. Mess this one up & you are in heap big doo doo's!
Hence why live working is not acceptable.

 

[mogga]

if taking a C.U. cover off is a fail then I would fail every day of the week
I work mainly in commercial situation and would never get away with puting in the lim box "Unable to take off DB cover as it would be live " Im an approved electrician and as such have been trained and know the risks and how to use test equipment in live situations FFS
I cant imagine the manager of a resteraunt allowing me to turn off all his/her electricity while I remove covers ect its not practical I have limited dbs that I deem unsafe to work on while they are live MEM Dorman smith LM Crabtree C50 ect this is getting to be a JOKE seems like they want trained monkeys who have no clue how to work on old stuff just want to install nice shiney new equipment What else do they expect from 5 week wonders ?????????????

 

[Tuttle]

Thanks guys. So the answer is that I shouldn't get into any bother if I energise a circuit with the CU lid off to do RCD tests, which is exactly what I do when I don't have an inspector looking over my shoulder

I thought that would be the case but I just wanted to make sure. I think that assessment paranoia is starting to kick in and sometimes H&S rules do seem to go a little bit too far, especially when you're dealing with large organisations!

Actually I used to work in a TV repair shop, over 20 years ago now, and we used to have unattended TV's switched on with screens facing the wall and backs off all over the place, and nobody thought anything of it. We used to have customers coming into the workshops sometimes as well. I wonder what modern H&S would think of that!

 

[Engineer54]

One other point.
HSE do not consider live testing as live working.
Live testing is live testing, an essential part of ensuring that electrical equipment is safe for continued use.
Live working is live working, disconnecting and making connections say on an energised circuit carrying current. This is very highly regulated and controlled. Mess this one up & you are in heap big doo doo's!
Hence why live working is not acceptable.

How about ''Live'' HV/MV overhead line/string and insulator cleaning, with high pressure water equipment from the ground??

 

[netblindpaul]

Different ball game E54, this would only be done by (in the UK) NG, the DNO's, or their approved and trained, competent contractors.
The problem you have in the LV electrical industry is that there are too many who are incompetent out there, so they "police" that by making these rules.
Mind to be honest I've never come across the work you describe being done.

 

[telectrix]

Thanks guys. So the answer is that I shouldn't get into any bother if I energise a circuit with the CU lid off to do RCD tests, which is exactly what I do when I don't have an inspector looking over my shoulder

I thought that would be the case but I just wanted to make sure. I think that assessment paranoia is starting to kick in and sometimes H&S rules do seem to go a little bit too far, especially when you're dealing with large organisations!

Actually I used to work in a TV repair shop, over 20 years ago now, and we used to have unattended TV's switched on with screens facing the wall and backs off all over the place, and nobody thought anything of it. We used to have customers coming into the workshops sometimes as well. I wonder what modern H&S would think of that!

that takes me back a while. mirrors at back of bench, line output valves with around 8kV sitting exposed, metal chassis connected direct to neutral, except when some idiot had wired the plug wrong way round. O/C dropper resistor leaving caps chasrged to 200V d.c. happy days.

 

[Engineer54]

Different ball game E54, this would only be done by (in the UK) NG, the DNO's, or their approved and trained, competent contractors.
The problem you have in the LV electrical industry is that there are too many who are incompetent out there, so they "police" that by making these rules.
Mind to be honest I've never come across the work you describe being done.

Only jiving with you mate...lol!!

Yes they do use this form of cleaning (among others) in the UK. Mainly in and around heavy industrial areas and complexes where prone to industrial build-up of contaminates. Depending on the type and severity of the build-up, anything between every 10 to 15 year periods. Obviously water needs to be high purity deionized water.

If you look at some of Tony's photo's of the heavy industrial plants that he's worked in you will see for yourself the build up that can and does takes place. Now imagine that build-up on 33/66KV and above strings and there insulators. Heavy carbon producing plants tend to need more frequent line cleaning...

 

[netblindpaul]

E54,
I know HV stuff needs cleaning, and I had envisaged a method, as you say, along with the same principles also that are used for water fire extinguishers which are used on LV electrical equipment.
However, I was under the impression that it was normally dry blast cleaning or dry ice cleaning that was used.
Though I can believe it possible to use water, after all water is an insulator...