Dangerous Electricity Supply

[chris_b]

I've played outdoor gigs for the last 2 weekends and both times the electricity supply, from a generator, had no earth!! We refused to play unless a proper supply was provided.

Always carry an earth loop indicator to check the electricity supply; it's basically a 13 amp plug with lights on the top to tell you if the supply is good or bad.

Without an earth your anti surge plug won't work and you can die from electrical shock, as Keith Relf (Yardbirds) and Les Harvey (Stone The Crows) did.

[ironside1966]

Glad you had the good sense not to play, many would and it is not worth risking your lives.

[lowhand_mike]

ooh, where can i get one of those then? and what do they normally go for?

[6stringbassist]

I always use an extension lead with a built in RCD, it won't actually work unless there is an earth, and will 'trip out' if there's a fault.

Something like this is ideal, and cheap.

[url="http://www.maplin.co.uk/Module.aspx?ModuleNo=29769&doy=16m7&criteria=rcd"]http://www.maplin.co.uk/Module.aspx?Module...mp;criteria=rcd[/url]

Edited July 16, 2008 by 6stringbassist

[chris_b]

The RCD is good but only if you have an earth. If you don't it doesn't trip. You should be able to find these in any electrical shop. These are a couple of examples I found online:

MARTINDALE CP501 CHECK PLUG £11.95
[url="http://www.pat-training.co.uk/socket_testers.htm"]http://www.pat-training.co.uk/socket_testers.htm[/url]

13A Tester Plug £8.40
[url="http://essentialsupplies.co.uk/acatalog/Online_Catalogue_13A_Test_Plugs_147.html"]http://essentialsupplies.co.uk/acatalog/On..._Plugs_147.html[/url]

Edited July 16, 2008 by chris_b

[6stringbassist]

[quote name='chris_b' post='240839' date='Jul 16 2008, 01:23 PM']The RCD is good but only if you have an earth. If you don't it doesn't trip. You should be able to find these in any electrical shop. These are a couple of examples I found online:

MARTINDALE CP501 CHECK PLUG £11.95
[url="http://www.pat-training.co.uk/socket_testers.htm"]http://www.pat-training.co.uk/socket_testers.htm[/url]

13A Tester Plug £8.40
[url="http://essentialsupplies.co.uk/acatalog/Online_Catalogue_13A_Test_Plugs_147.html"]http://essentialsupplies.co.uk/acatalog/On..._Plugs_147.html[/url][/quote]

If it hasn't got an earth it won't actually work at all.

Edited July 16, 2008 by 6stringbassist

[martthebass]

I always go wireless - does that protect me?
I assumed it did if the amp had double insulation like most domestic electrical goods.

Edited July 16, 2008 by martthebass

[warwickhunt]

[quote name='martthebass' post='241193' date='Jul 16 2008, 07:48 PM']I always go wireless - does that protect me?
I assumed it did if the amp had double insulation like most domestic electrical goods.[/quote]

Wireless is obviously keeping you isolated so long as you don't intend touching another single piece of kit; yours or PA. However, it doesn't stop your kit getting damaged!

[bremen]

[quote name='martthebass' post='241193' date='Jul 16 2008, 07:48 PM']I always go wireless - does that protect me?
I assumed it did if the amp had double insulation like most domestic electrical goods.[/quote]

No amp that I know of is double-insulated.

Surely a generator is safer than mains? The only reason you get a shock from the mains to ground is that the ground is used as the conductor for the return current. The output from a generator is 'floating', ie not connected to earth at either side, so there's no reason for current to flow to earth.

[chris_b]

On both gigs we had an additional problem. Although we ran a daisy chain of extension leads to a proper power supply, the house (marquee) lights were still running from the unearthed generator. Potentially this was a very dangerous situation so we had to make sure we went nowhere near their lights while we were playing.

[6stringbassist]

[quote name='bremen' post='241550' date='Jul 17 2008, 10:11 AM']No amp that I know of is double-insulated.

Surely a generator is safer than mains? The only reason you get a shock from the mains to ground is that the ground is used as the conductor for the return current. The output from a generator is 'floating', ie not connected to earth at either side, so there's no reason for current to flow to earth.[/quote]

It will always go to earth if there's a difference in potential, that's why lightning goes down, you can't get more floating than that.

The problem with the Martindale type testers is they only tell you if there is an earth, not how good it is.

If you have a very poor earth, then whatever means of disconnection you have won't disconnect fast enough, ie in 40ms or faster.

I'd recommend that everyone uses some sort of RCD protection.

Anywhere that has 'live' entertainment where the public has access are meant to be tested to BS7671 standard every year, to obtain their entertainments license. They are also meant to have RCD protection on all sockets likely to be used.

[bremen]

[quote name='6stringbassist' post='241557' date='Jul 17 2008, 10:20 AM']It will always go to earth if there's a difference in potential, that's why lightning goes down, you can't get more floating than that.[/quote]

No, the reason lightning goes down is because there's a potential difference between the cloud and the ground. You also see lightning from cloud-to-cloud; that's where there's a PD between clouds.

[b]If neither output terminal of the generator is connected to ground [/b], there is only PD from terminal-to-terminal. So you don't want to be bridging them ;-)

However, there is no PD between either terminal and the ground, so you could quite safely grab either terminal with one hand and the ground with the other.

Does anyone know whether generators do connect a terminal to ground, and if so why?

[quote]I'd recommend that everyone uses some sort of RCD protection.[/quote]

Certainly if the supply is referenced to earth (or even if it's not, doesn't do any harm!)

[6stringbassist]

[quote name='bremen' post='241563' date='Jul 17 2008, 10:35 AM']No, the reason lightning goes down is because there's a potential difference between the cloud and the ground. You also see lightning from cloud-to-cloud; that's where there's a PD between clouds.

Erm, that's what I said.

[b]If neither output terminal of the generator is connected to ground [/b], there is only PD from terminal-to-terminal. So you don't want to be bridging them ;-)

However, there is no PD between either terminal and the ground, so you could quite safely grab either terminal with one hand and the ground with the other.

Ground or earth has zero potential, if the generater has an output of 230 volts then there's a potential difference of 230 volts.

Does anyone know whether generators do connect a terminal to ground, and if so why?





Certainly if the supply is referenced to earth (or even if it's not, doesn't do any harm!)[/quote]

[bremen]

[quote]No, the reason lightning goes down is because there's a potential difference between the cloud and the ground. You also see lightning from cloud-to-cloud; that's where there's a PD between clouds.

Erm, that's what I said.[/quote]

My point is that there is PD between cloud and ground, hence lightning.

If neither output terminal of the generator is connected to ground there is no PD between generator and ground, hence the irrelevance of an RCD.

Just like using an isolating transformer, where the output is floating so there's no possibility of current flow to earth via an unfortunate bass player.

My question is, does anyone know whether generators do reference to ground? (I can't think why they would, but if they did they'd be just as dangerous as mains electricity and an RCD is a must).

Unless you know for sure that the generator output is floating, though, do use an RCD. Or an isolating transformer ;-)

[thepurpleblob]

You don't need an earth (as in connected to a spike in the ground)) for a generator supply. In most cases the earth is not connected and is not required. This is normal. If you *need* to use an RCD then generators can be modified by linking the earth to the neutral. It isn't really neccessary though, as the setup is completely different to the mains supply. It's actually inherently safer.

If the generator has been modified you must *always* (legally I think) use an RCD *and* connect the earth/neutral to a ground spike. I suspect all that hassle is more likely to go wrong and be dangerous than just to leave it alone.

RCDs, surge protectors etc. are mains protection devices. They're not intended for generator use.

Edited July 22, 2008 by thepurpleblob

[Mottlefeeder]

Small generators are designed to be used with equipment that is local to them. The output is not earthed so that even if you have a fault, and the casing of your equipment becomes connected to either of the mains conductors, you will not get a shock because the current has nowhere to flow. If you have a second fault on the system, then you create the conditions where one piece of gear may be 230 volts different to the next, and a shock current could flow from one to the other through you. The protection philosophy is based on you being able to see the first fault, and chosing to do something about it, hence the need for the generator to be supplying gear that is local to it.

If the generator is feeding strings of lights etc, you will probably not be able to see the first fault - the cable pinched by the scaffolding clamp for example, and you will not know that you only need one more fault to make it dangerous. In those circumstances, it is better to earth the generator output, so that the first fault will show itself by causing a trip.

A couple of other points -

As has already been pointed out, plugtop RCDs expect to see a connection between earth and neutral on a domestic supply, and on a generator with an un-earth-referenced output, they will not allow the breaker to be set. The RCDs in distribution boards work differently, and would be a better option (they do not trip on loss of power).

One poster commented about daisy-chaining distribution boards together. This is not a good idea. Every distribution board that you connect through will add the cable to plug connection, the cable to socket connection, and the spring connection of the socket to plug-pin, into the earth circuit, increasing the risk of a faulty earth. Plugging faulty equipment into an unearthed distribution board could make everything on that distribution board dangerous, since there is no earth connection to blow the fuse for you. The best way to work is to use longer mains cable to your equipment, and fewer cable extenders.

[BOD2]

I did a little research when this topic first appeared but the only information I could find made me feel that it was incomplete or not applicable to this example of generator use.

If you look on generator websites you will see the advice that an earth is not needed, due to the inherently safer nature of the generator. So far so good.

BUT...these websites are talking about general use of a generator - on a building site or to power a few small applicances outdoors. This is completely different to powering a band with lights, amps, PA, longer cable runs etc. etc. which is quite different to powering up a couple of small appliances.

For that reason, although I accept that generators do not NEED to be earthed, I would feel more comfortable using a generator that has been suitably modified and earthed with an earth spike by a qualified electrician, and then using the normal RCD protection that I would use at any other gig.

The problem is....are you going to find such a setup at the average small outdoor gig ? It might be wirth inquiring beforehand.

[Mottlefeeder]

This is the HSE guidance on using generators -
[url="http://www.hse.gov.uk/foi/internalops/fod/oc/400-499/482_2.pdf"]http://www.hse.gov.uk/foi/internalops/fod/...0-499/482_2.pdf[/url]

[thepurpleblob]

[quote name='Mottlefeeder' post='246453' date='Jul 23 2008, 10:21 PM']This is the HSE guidance on using generators -
[url="http://www.hse.gov.uk/foi/internalops/fod/oc/400-499/482_2.pdf"]http://www.hse.gov.uk/foi/internalops/fod/...0-499/482_2.pdf[/url][/quote]

Mmmm... it pretty much tells you to earth it and use an RCD from my understanding (unless it's a single load item a very short distance away and you have somebody sitting watching it). Very much at odds with what genny manufacturers say - not surprisingly probably.

[BassMunkee]

Belkin do some really good surge protectors which also won't work without a decent electricity supply.
£9.99 for a single plug, and £19.99 for a 4 gang extension, worth the money, IMHO, AND you insurance against breakage of plugged in stuff, which can't be bad.

[yorks5stringer]

We had a picnic to play on Saturday and specified a gazebo and surge protected power supply. Needless to say it started to rain, the gazebo let a fine drizzle of rain through that you could not see but feel...cue disconnection of all equipment and swift move inside!

[chris_b]

I'm confused!! After watching 2 different bands on 2 different gigs rushing around trying to sort out the same problem I thought I knew what to do when playing with an electricity supply from a generator!!

I spoke to a BBC electrician at the weekend and he said you don't need an earth on a generator supply because it is a closed system and all the equipment is local to the generator..... BUT, the electricity regs say you should have an earth every time! What do you do?

I guess the safest option is to go for the earth and use RCD plugs.

[Mottlefeeder]

[quote name='chris_b' post='246680' date='Jul 24 2008, 10:30 AM']I'm confused!! After watching 2 different bands on 2 different gigs rushing around trying to sort out the same problem I thought I knew what to do when playing with an electricity supply from a generator!!

I spoke to a BBC electrician at the weekend and he said you don't need an earth on a generator supply because it is a closed system and all the equipment is local to the generator..... BUT, the electricity regs say you should have an earth every time! What do you do?

I guess the safest option is to go for the earth and use RCD plugs.[/quote]

There may be some confusion here about what we mean by the electricity regs.
The IEE wiring regs were originally rules for IEE members, and had no legal standing. They are now a British standard.
The Electricity at Work Regulations 1989 - [url="http://www.opsi.gov.uk/si/si1989/Uksi_19890635_en_3.htm#mdiv8"]http://www.opsi.gov.uk/si/si1989/Uksi_1989..._en_3.htm#mdiv8[/url] is the law (for all people covered by the Health and Safety at Work Act), and says

"Earthing or other suitable precautions
8. Precautions shall be taken, either by earthing or by other suitable means, to prevent danger arising when any conductor (other than a circuit conductor) which may reasonably foreseeably become charged as a result of either the use of a system, or a fault in a system, becomes so charged; and, for the purposes of ensuring compliance with this regulation, a conductor shall be regarded as earthed when it is connected to the general mass of earth by conductors of sufficient strength and current-carrying capability to discharge electrical energy to earth."

That does not say you need an earth every time, and allows the use of an isolated system as a means of preventing danger through 'conductors becoming charged'. However, when the system stops being isolated (the first fault) your precautions should pick that up.