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Topic Title: Festival Power
Topic Summary: Testing ??
Created On: 16 August 2012 10:44 PM
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 16 August 2012 10:44 PM
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slittle

Posts: 3459
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I've had the pleasure of helping a good friend install a microwave and copper network for one of the emergency services at the "V" festival this week.

A total change of role for me, but using some of my hard earned skills from a previous employment and I have to say really enjoyed.

However having watched the sparks on site install the power supplies for us it's left me wondering what happens with regard to design, testing etc on such events as it seems to be very much drop off a genny, plug in a 63a lead, split it down on some distribution and connect in the mobile units as necessary. I've had three sites made live and nothing appears to have been checked.

To be fair it's not my problem as I've got no electrical installations on site as such as all of our kit is 13a plugs and cat 5 but given the expected 20-30,000 people on site there doesn't seem to be much paperwork ???


Stu
 16 August 2012 11:01 PM
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peteTLM

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Actually stu,
ive recently tested some temp installs for the olympics which are basically the same kit etc.

Theres no paperwork........its all done on a tablet computer!

There is no insulation resistance testing as there are programmable earth leakage relays on the main backbone (which are single core anyway, 150mm or 240mm tri rated carrying 400A) and the plug and play leads are done at the depot before dispatch. Bigger supplies just have multiples run.
RCD response, rcd delays, earth loop tests are all done to every avaliable socket.

As you can imagine, 240mm tri-rated leads with 400A plugs 50m in length are an eye watering amount of money.

The systems are set up as TNS.
The generators are hooked up in parallel where needed.

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----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 17 August 2012 05:49 PM
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davezawadi

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The safety is not in the paperwork Stu, as you can't test safety into an installation, just verify that its there! As you have local generation TN-S is the order of the day, and stage structures an the like have main bonding. All of the larger stuff (dimmers, amplifier racks etc) is class 1 with regular PAT inspection, and difficulties are rare. Because structures are metal, there are multiple earth connections and paths everywhere, so touching something with a faulty earth cable and an insulation failure is very difficult. Interestingly there were a few cases in the 60s and 70s where musicians turned up to gigs with live guitars, and we had an edict at the BBC which used separate isolation transformers for each piece of non BBC kit! (It seems that we were not trusted to test the earth continuity of externally supplied gear) . Risk assessments tend to concentrate on water getting into things, and keeping the punters away from anything they could get at whilst under the influence! RCDs etc are everywhere on subcircuits, but its rare to get one trip even in the wet. The 63A lead (this is standard for low consumption items) normally comes to a DB with 3 single phase 30mA RCDs and distribution breakers to smaller connectors which may then go to 13A sockets. Gear of dodgy origin gets a quick PAT test and inspection before powering up, so it is probably as safe as anything can be. I haven't seen a live mic or guitar for a long time, but some Artistes claim they can feel tingles, probably from LSD or straight fear! BTW the cables are HO7RN-F rubber not tri-rated PVC (that's for panel wiring, I don't think I have seen tri-rated real cables), and are significantly heavy and expensive. Most of you wouldn't like the connectors for larger cable sizes (Camlock and similar) as they are individual for each core (and colour coded) but then you wouldn't want to unplug one under load anyway.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 17 August 2012 06:02 PM
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sparkingchip

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The BBC lost a engineer locally when he pulled up in a people carrier with a large extending aerial mounted in the roof, he extended the aerial under HV cables without checking it was clear first.

Andy
 17 August 2012 06:29 PM
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slittle

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Dave & Pete,

Looking at the way the guys were installing the bits we saw they were clearly very competent and yes loads of RCD's which were quite happily holding.

We all know the paperwork is only as good as the guy that writes it and the real safety is in the design and execution of the install.

Dave, yes every bit of cable I saw was H07RN, unfortunately I didn't get to see the "big stuff" as the stage areas were not part of our remit so it was 63A max for our cabins and mobile units.

Certainly an impressive set up by all concerned and so much of it will never been seen by the thousands of festival goers as it's all in "off limits" areas.

Stu
 17 August 2012 07:56 PM
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davezawadi

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So it is Stu, but the odd MW or two is quite dangerous in the wrong hands. OMS was mentioning me as a (possible) sparks on another thread, but then I hate the chasing of walls! Good luck with your next experience with the entertainments industry. BTW I was really impressed with the spectacle of the Olympics opening... pity the sound feed on the BBC I-player (and probably the broadcast) had so many technical snags, you can't get the staff any more! oops my age is showing.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 17 August 2012 08:16 PM
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slittle

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Dave,

We only get the good gigs that have a large presence from the boys in blue

Probably be V next year before we play again but time will tell. It makes a nice change from the pigs, chickens and combines for a few days

Stu
 17 August 2012 08:53 PM
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davezawadi

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OK Stu, if you need help, just ask!

-------------------------
David
CEng etc, don't ask, its a result not a question!
 18 August 2012 12:43 AM
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peteTLM

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Indeed, the sheath is Ho7RN rubber, the strands are definatley tri, there is just too many of them.
Unintentionly, we had a tug of war with a cable with 10 people and ripped the plug off the end. Fine, fine strands.

I have to say the difference between countrys and manufacturers were really noticeable. One country in particular, the cable birdcaged like an swa despite having no armour and was a nightmare like no other. The cable from a country that nicks all our fish was a dream!

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----------------------------------------
Lack of planning on your part doesn't make it an emergency on mine....

Every man has to know his limitations- Dirty Harry
 18 August 2012 07:40 AM
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jleltd

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Tri Rated cable is called so because it is certified for use by 3 national testing organisations UL CA and BS. Other than that its appliance wiring cable PVC single insulated 105 deg C.

H07RNF has a rubber type insulation under that sheath and being rubber the copper strands are either tinned or covered in a clear wrap to stop the bare copper coming into contact with the rubber.

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James
 19 August 2012 07:40 AM
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deleted_1_Grizzly01

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BS 7909, anyone?
 19 August 2012 09:50 AM
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OldSparky

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i used to work for a company called stage electrics,, this was my job role connecting gennys running in temp supplies, testing and then on site in case it went off..

all the leads were pat tested and inspected when returned to the warehouse ready for the next event so you could count on them being ok when next used.

all the supplies are on rcds, testing used to be generally loop tests and rcds tests..

the company had niceic tests forms adapted for event power.

gennys were earth staked as well as the main distros.. bonding where we could to the stage, tho to be honest you couldnt be sure the way the stage was constructed it would be continuous.

great job but long hours, like my home life now.
 19 August 2012 10:09 AM
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davezawadi

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As most posters here seem a little vague about the readily obtained BS7671, quoting standards is little help to anyone. As I said before safety is not tested into installations. You can fully comply with BS7671 and still have a fixed installation which is not very safe, it all depends on the things which cannot be specified by a simple set of rules.

Consider this:
We start with a slogan, which may have some degree of truth "Speed Kills"
Our fatal accident rate is the lowest in Europe
Accidents on country roads are higher than other roads
We must see a year on year improvement for political reasons
If the speed limit were reduced there would be less serious accidents, lets make it very low!

What is wrong with this reasoning? (Which I could apply to BS7671 but its more obvious this way)

Most country roads are relatively narrow, have many bends and hills, high hedges etc.so visibility is not as good as other roads
They have difficult to see road junctions with smaller visibility as above
They tend to have slow traffic like tractors using them
Many drivers drive quite slowly, they are enjoying the view, or realising that conditions are less good, or are old or tired.
Others have distance to travel and all this slow traffic annoys them
People overtake in unsatisfactory places without adequate view of the road, and often exceed the speed limit in doing so. They tend to feel that they have no alternative to a bit of risk taking.
Serious accidents are often due to junctions or overtaking.

Does reducing the speed limit to 40mph even address the underlying reason for the accidents?
Can it be enforced, say a speed camera every 250m?
Is there an alternative way to improve the accident rate, with a less serious impact on journey times?
If the policy doesn't work, particularly if accident rates increase, can it be reversed or is this politically unacceptable?

Speed cameras may have had a little impact on accident rates in a few places. In general the policy failed as it did not address the correct problem, which is probably to improve driver concentration and skill at assessing risks, rather than making him watch the speedometer not the road! This policy is very slowly being reversed in a few places.

You see you cannot get safety by inspecting and testing speed, (or EFLI) when the public are unaware of the environment (taking mains powered radios into the bath). The alternative of testing and improving the quality of country roads is unacceptable due to cost (in fact many are already in very poor condition, causing more accidents). Government wants to be seen to be doing something....even if it is not the right thing.

-------------------------
David
CEng etc, don't ask, its a result not a question!
 19 August 2012 02:18 PM
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John Peckham

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David Z


I think the designer of the installation can design in safety and the installer install to the design. The inspector than can verify compliance with the design and BS7671. Of course you can try and predict how the installation may be used and make an allowance for misuse but the magic phrase "so far as reasonably practicable" will need to be applied. Often greed and a general lack of integrity coupled with incompetence will displace safety for money.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 19 August 2012 03:38 PM
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davezawadi

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Yes John, That is what I think too.
The point I was making is that testing is only part of the story, it is only verifying that the design is installed correctly. A poor design can inspect and test fine, but still not be satisfactory. Of course that is why the inspector needs to understand what is going on fully and completely, which is why I also remark on some of the other posts! These festival installs have a very standard design methodology, are pretty robust and plug together so mistakes are very unlikely. Therefore the level of testing which does happen is easily missed because it is largely simple verification of connections.

I was going on about the speed limit idea because I think this misses the design point, it attempts to test safety into a system and is not going to work. We have lots of rural roads here and a significant number of serious accidents. Two near me in the last couple of years can be directly understood to be impatience with slow traffic, and I do not see how making the volume of slow traffic greater will reduce accidents. True that if everything were stationary collisions would be rare, but most people living outside towns need to travel significant distances for everything, and they have a limited number of hours in the day. My point is probably supported by the statistic that it is young drivers who generally have these accidents, and I think this is lack of experience and skill rather than lack of patience as many older drivers also drive fairly fast, but perhaps in safer places!

-------------------------
David
CEng etc, don't ask, its a result not a question!
 19 August 2012 04:16 PM
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kj scott

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As Grizzly has stated, BS 7909 is relevant, not BS 7671, having spent some time playing with the V installations over a number of years section 10 of BS 7909 is particularly pertinent. Any bonding to the stage also has to consider interference to the sound systems.

The set up is pretty much generators and trailing leads, these are normally tested prior to delivery to site ; Camlock has been replaced by Powerlock as a connection system in recent years. They also use a lot of stand alone generator/lighting sets.

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http://www.niceic.biz
 19 August 2012 06:45 PM
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John Peckham

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BS7909 even has it's own special test sheets for the I&T. BS7909 does however refer to BS7671.

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John Peckham

http://www.astutetechnicalservices.co.uk/
 19 August 2012 11:43 PM
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kj scott

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Originally posted by: John Peckham

BS7909 even has it's own special test sheets for the I&T. BS7909 does however refer to BS7671.


BS 7909 does refer to BS 7671 regularly, and why not, the principles of safety are the same; but the starting point of reference must still be BS 7909 for entertainment sites such as the V.

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http://www.niceic.biz
 20 August 2012 11:12 AM
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AJJewsbury

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We start with a slogan, which may have some degree of truth "Speed Kills"
Our fatal accident rate is the lowest in Europe
Accidents on country roads are higher than other roads

If the collision rate higher on rural roads, or just the death rate?

According to one of my 1st aid trainers, the recent reduction in road deaths is more due to better medical procedures rather than safer driving. If my experiences in west Wales is anything to go by, you're likely to have to wait longer for things to arrive (due to the distances), wait longer until they actually find you (roads can be miles long between landmarks and signs are pretty scarce), wait longer to get to the hospital and then probably find that the local casualty is less well equipped than its city-centre counterpart.

Just a thought.

- Andy.
 20 August 2012 03:54 PM
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davezawadi

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Hi Andy
Whichever it is of those, and I don't think it is clear, is lowering the speed limit the correct fix?
Or is it your own list which should be improved, as all of these are important wherever you live?

I expect you are well aware of the various quality improvement systems which are touted; six sigma, 5S etc. and one that is not quite so commonly known the theory of constraints which is also known as the logical thinking process. One of the most important parts of quality improvement is trying to fix the right problem, as it is all to easy to fix other minor snags and get little effect on the overall system. I have quite a bit of experience with TOC techniques and it is extremely effective. I would like to find a way to improve the quality of electrical inspection, especially EICRs, but there are a great many competing requirements on the inspector particularly wielding his power to get work through dubious reporting. I think that it is extremely important that reports are truthful and accurately assess the risk, but I find that this is often not the case, major dangers such as live conductors are not found but very low risks are reported as immediately dangerous. I am always upset when compliant installation features are reported as dangerous, and particularly when the inspector clearly is not familiar with the current edition of the regulations! For example a bathroom without any equipotential bonding but protected by RCD is given a C1. Similarly an installation with main bonding, but not connected adjacent to the stop tap, is given a C1.

This kind of thing gives electricians a bad name, and makes the public much less likely to have inspections or even repairs, because they know that once the man (woman) is through the door they will have to spend a great deal of money. If they have to spend money on things that are not even wrong, it is worse still. Interestingly the scheme providers seem to have very little interest in quality or complaints.

-------------------------
David
CEng etc, don't ask, its a result not a question!
IET » Wiring and the regulations » Festival Power

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