Temporary electrical installation pictures

I have uploaded so many pictures of temporary electrical installations to this blog that I think it is time to give the subject a separate post title of its own. This post will be an anchor post for all pictures that I uploaded on temporary electrical installations.

Picture 1 – Temporary electrical submain cables




===== RELATED ARTICLES:   Temporary Electrical Earthing Pictures  |  Electrical grounding electrode pictures |  Electrical installation pictures

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I wish to make one thing very clear on temporary electrical installations.

The installations for purposes of temporary electricity supply are not "nice" installations in majority of construction scenarios.

If I am to show only the nice and proper temporary supply installations on this blog, then I only serve the readers with only less than half of my experience on this matter.

With that also it means that only less than half of the lessons can be learned by beginners of electrical installations.

With all these good and bad examples of electrical installations, beginners can learn more of the real life scenarios that they will face when they start work at real construction sites.

Now back to the pictures.

Picture 1 above shows how the low voltage (LV) submain cables are installed in this project.

These cables are 4-core, steel-wire-armored copper cables. They connect the temporary main switchboard to individual sub-switchboard inside the building under construction.

Personally I do not really have any objection to the way the contractor installed these cables because they are steel wire armored cables even though they look a little unsightly.

They however should be protected from accidental damage. Some sort of barricade should be installed because one of the main construction roads is just a few feet away from the steel fence.

An alternative might be to raise the temporary cables higher so that any possible accidents by construction vehicles would not hit the electric cables.

Notice the picture label that I put on the right of the picture: temporary earthing electrode. The indication pointed to a white signboard.

Actually this was one of a few improvements made by the main contractor to the temporary electrical installation at this project site. I have sent a post earlier on this issue, which you can read here, Temporary electrical panel and cord pictures.

The warning sign indicating the location of temporary electrical grounding is a very important safety matter. If the earthing is damaged and not functioning well enough, hundreds of workers at the job site faced risks of electrocution or serious injuries from electric shocks every day.

If you have not seen these sorts of injuries before, you can see them see them at this post, Electric shock injury pictures. If you have seen then, then don’t. Once should be enough. I lose my appetite for food almost a whole day every time I look at those pictures.

The temporary grounding electrode should have also been barricaded for protection from damage, which was also carried out one or two weeks after this photograph was taken.

Later the temporary submain cables on the fence were also provided with some DANGER warning signs.

Picture 2 – Temporary site flood lighting



This flood light was installed on the fence not far from the sub-main cables in Picture 1.

If I remember it correctly, this flood light fixture was 400 watt, IP 65 metal halide.

You can see more photographs of temporary lighting at another post, Temporary lighting installation pictures.

Picture 3 – Temporary electrical panel without earthing connection



This electrical panel was installed to operate a machinery at a very wet condition and outdoor.

The electric panel was very neat and of a high quality.

A brief look inside might not alarm you at all. It did look good.

However, a closer observation revealed something sinister. The panel did not have the electric shock protection at all.

In case some readers may wonder, the machinery supplied by this panel was not an automated machine. It was a manned at the machine itself with the motor near the operator and in a very wet area.

You can read the post here, Electrical panel pictures. There are more pictures of this electric panel there also.

Picture 4 – Burned 13A socket outlet



This is a temporary switched 13A socket out installed on a temporary electrical panel at a construction site.

Notice burn mark around one of the socket pin holes. This is the “LIVE” terminal of the socket.

You would get this mark if you use the socket the way photographed in Picture 2 (check the photo at the post link below). It could have been caused by fire sparks when the live wire was pulled out of the socket without turning off the socket switch.

It could also be caused by fire or heat because the contact between the live conductor and the socket terminal inside was not good enough to handle the current taken by the electric tools being operated.

In any case, this would be a very good source of electrical fires.

This temporary DB was actually installed outside of the new building and there was not really anything that could catch fire. However, if it were inside the building, it would be also a real fire hazard.

Visit this post, Temporary socket outlet pictures, to see more photos of temporary electrical panels and temporary socket outlets.

Picture 5 – A method(?) for a temporary electrical distribution



Would you believe it if I say that the above picture was a distribution system for a temporary electrical supply at a building under construction?

I took the above picture quite a while back. I thought it was interesting.

You can see the rest of the pictures here, Temporary electrical distribution.

Picture 6 - Another temporary electrical panel



I saw the above temporary installation at a new project I just get involved in. So I took some pictures and sent out the following Site Memo:

SITE MEMO:

Dear Sir,

Re: Temporary electricity supply: Electric shock hazards

As I have explained on Saturday last week, please find attached photographs of the temporary electrical cabling.
I believe the photos are self-explanatory. However, I wish to highlight the following points:

1. Many extension cords do not have the grounding cable.
2. The extension cords are laid on the floor along main work traffic. Cables can be damaged leading to exposures of LIVE cables. A few have already been damaged and improperly patched up.
3. Observe that the area is a very wet area. The risks of electrocution here is very high.

I suggest the following action be taken IMMEDIATELY:

1. If possible, the temporary DB is relocated to a more suitable and DRY area.
2. Enforce the rules that all subcontractors run their extension cords at high level along walls or columns.
3. Enforce the rules that all extension cords have a working grounding conductor.

It is my opinion that the present situation is VERY DANGEROUS and a fatal electric shock accident can happen any time.

Regards,

Lee Wan Seng
Resident Electrical Engineer

Visit this post, Temporary electrical cabling, to see the rest of the pictures.

That’s all I have time for today. I will update this post with more pictures soon.

Chiao.

Copyright http://electricalinstallationwiringpicture.blogspot.com Temporary electrical installation pictures

Temporary Electrical Earthing Pictures

This post shows a few pictures on the earthing of temporary electric supply installations. However, before you see the pictures, remember that I am sharing here pictures of real life electrical installations. By showing them on this blog, I am sharing my experience with the readers.

It does not mean that I am recommending what is shown on a picture as a good or correct way to do something, unless I specifically say so, of course.

Beginners, please take note. The pictures that I show on this blog are materials for you to see and think. These are real life pictures from real construction sites, and construction industry is a really complex world by itself.

Picture 1 – The earthing of temporary supply DB using the cable’s wire armor



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Picture 2 – A closer view on the termination of the cable armor



The safe utilization of a temporary electric supply often depends on the existence of an effective electrical earth.

It is the responsibility of the person in charge of a construction site to ensure that the earthing of the electric supply system is working effectively. The site’s electricity supplier (the electric supply authority) has nothing to do with this part of the electric supply.

Many electricity supply authorities use protective multiple earthing (PME) system. With this method, the electrical system’s neutral and earth are combined.

When this method is used, all metalworks including structural metalwork must be bonded together in such a way to make all metal parts electrically continuous.

However, in most real life construction sites, this bonding is hard to do and almost impossible to maintain properly throughout the duration of the construction period.

So usually, the public utility supplier will not connect the supply until an alternative electrical earth is provided and fully tested.

They also insist that evidence of the earthing test results endorsed by a competent electrician is submitted together with the completed application forms for the temporary electricity supply to the site.

Independent earth electrodes

Several methods are used to provide the alternative electrical earth. The most commonly used method is to use independent earth electrodes installed at the location near the main intake temporary switchboard (this is usually the location where the temporary meter is installed).

This will ensure that the protection fuses will operate and disconnect the site electrical installation from the incoming public supply in the event of a fault.

This disconnection is an absolute must in order to minimize the damages to the site’s electrical system due to the fault.

It is also to prevent the fault from spreading upstream to the electric supplier’s distribution network. The latter is the main reason the electricity supplier is worried about this aspect of the temporary installations.

Picture 3 – Temporary electric supply: A poor man's complete system


I will devote a whole post in the future for this subject of earthing.

For now, I have a few picture of temporary electrical grounding for your viewing pleasures. I seek an apology from those readers who already have some electrical knowledge. These pictures are not for you guys. They are just too simple.

However for those managers and construction people who have always been intimidated by those colleagues on these sorts of issues, let me assure you that if you understand what these three lousy pictures say, then you already understand what an electrical grounding is.

Picture 4 – Temporary incoming cables, kWh meter, DB, earth wire and protective PVC conduit


Picture 5 – Temporary earth grounding



Now lets start with picture 10. You may need to click on the picture to see it in full size.

The black case on the wooden panel there is the temporary electric meter supplied by the electric authority. Below it in white PVC casing is the temporary distribution board.

You can also see a piece of wire in green insulation coming out downward from the distribution board.

This wire goes straight into a two-meter length white PVC conduit, and (if you watch it closely) it comes out of the vertical PVC conduit at the bottom and goes straight into the concrete floor just beside the plywood partition wall.

All these you can see much more clearly in Pictures 11 and 12.

Now let’s get back to the black energy meter.

Above it you can see two lengths of black insulated cables coming down from high level (below the roof level of the temporary wooden structure).

One cable terminates at a black piece of component just above the meter, while the other one terminates at a cheap white plastic terminal block.

The two components each have a cable of the same size coming out at the bottom connection and terminate at the temporary kilo-watt-hour meter.

Now lets get a little bit more technical.

Single-phase electrical installation

This is what we call a single-phase electrical installation (a three-phase supply would have four black cables coming down from the roof level – three phase cables and one neutral cable).

Therefore, the incoming supply from the authority is also a single-phase supply (we apply single-phase supply, so they give us a single phase supply).

An electric supply from the authority can be one of a few types.

Single-phase two-wire system

The type as recorded in the pictures is the single-phase two-wire type (three-phase 4-wire if we apply three-phase supply). This type will have two incoming cables from the authority’s distribution network – one live or phase cable and one neutral cable.

Other types may have three incoming cables from the distribution network for the same one-phase supply – the same live and neutral cables, plus a third cable, which is the earthing cable.

A construction site needs an independent, reliable electrical earthing

Now as I said earlier in this post, a construction site really needs an independent and reliable earthing, an electrical grounding that is not dependent on any third party’s grounding or even the electricity supplier’s grounding.

Failure to provide this can result in fatal injuries from electric shocks, even multiple casualties in a single accident.

Never mind my emotions on this (if you can sense them), but an electrical accident is that dangerous and electrical shocks can strike silently without warning.

Because of the need for that independent and reliable earth for the temporary site supply, the green electric cable is installed below the white PVC distribution board (Picture 11 shows this more clearly).

What if this earthing is not working?

The electrical earthing is important so that the electric shock protection device (ELCB or RCD) can operate and isolate the incoming supply from the temporary installation. (I have uploaded a few ELCB pictures at this post, 1-Phase ELCB Connection Pictures, for the readers who wish to see them).

Without this cable, the electrical system can still work. The workers can still use their tools and do a good job for their employers so the construction venture can end up being very profitable for the shareholders of the company.

However, one fine day, the extension cord that carries current to the electric drill one of the workers has been using gets damaged, exposing the live wire to an unintentional contact with any of the workers around the area.

Being hard at work, the workers bodies and clothes are usually very damp or very wet with sweat, and human sweat is a good conductor of electricity just like the electrolyte in your car battery.

In this situation, all that is needed is one accidental contact at any part of a worker’s body with the exposed live conductor of the damaged extension cord. Then he would receive a severe electric shock injury. Even death is highly likely depending on where on the worker’s body the contact to the live wire happens.

Severity of electric shock injuries depend on the location of the contact

If the contact is at the hands, then the electric shock current will travel through the chest and the workers heart before going down to the legs and the ground. Then you may have a case of fatal injuries there.

Sorry for the diversion. This electrical earthing matter is so simple that I have to drag the stories into the injury aspects to make it a bit longer ;-)).

Not only it is simple, it is also plain cheap and low cost.

Look at the picture again. You have a short length of the green wire and two meters of the white PVC pipe.

Wait… I know what a few of you are thinking…

Yes, there is copper earth electrode in the concrete, which goes straight down below the concrete about 1.5 to three meters into the ground.

Cheap in price, costly in lives

The above example is a very small installation, so it looks simple. This wooden structure only draws a few amperes. However, even for a large installation, the grounding is relatively just as simple.

The point that I am trying to make in here is that providing an independent and effective earth is not a challenge at all in most construction site situations.

So, do not risk human lives just to save some construction cost there.

Update February 11, 2010:

The challenge of a site electric supply

It is always a challenge to provide the electricity supply to the site people safely. Construction sites are among the most challenging environments to the safe use of electricity.

A lot of works are done outdoors, in all sorts of weather conditions. Wet and damp conditions present very high risks of severe electric shocks.

The workflow of site works is constantly changing as the construction work progresses. Therefore, the temptations to improvise the electrical distribution system are often too great to resist.

Routine construction activities, the demolition and excavation works may all result in damages to both the temporary supply and the newly fixed permanent supply systems.

When the activities at a site are at its peak with hundreds or thousands of workers ,not to mention construction vehicles and machineries, the site usually become congested.

This sort of situations makes the control of risks very difficult. Temporary cables and electric construction tools and equipment are very likely to be damaged by the movement of heavy machines and materials.

The people who use electricity at site have various needs, and sometimes conflicting interests and expectations. The workers and team leaders themselves work for different subcontractors and suppliers.

In order to maintain any reasonable degree of safety and control of risks, a effective site management is an absolute must-have for the site main contractor or the client’s people who are in charge at the construction site.

Due to the nature of construction works, a risk-free environment is impossible to attain most of the time. However, some risks can be avoided by careful planning before the work commences at the site.

Protect the earthing system

The protection of workers against electric shocks and injuries depends so much on the integrity of the earthing part of the electrical grounding system.

The earthing part, as shown in the above pictures, includes the grounding electrodes and all the underground conductors or cables that form part of the earth grounding network.

However, that is easier said than done.

These networks of electrodes and the connecting conductors are almost always installed at the ground level. They can easily be damaged by uncontrolled excavation works construction vehicles.

The personnel in charge of safety aspects of the construction site should include it their daily routing to patrol this part of the site temporary supply installation.

Other than that, it always a good idea to install some highly visible warning signs to warn workers and drivers of construction vehicles of these critical electrical supply safety parts.

The following are two pictures show the temporary warning signs put up by the contractor indicating the location of the temporary earthing electrodes.

They rushed up to install this after I found out in my second day of assignment at the construction site that the temporary supply at the building under construction has been operating for many months without earthing connection at all.

I have sent a post earlier about this temporary installation. Read it here, Temporary Electrical Panel Pictures.

Picture 6 – Temporary electrical earthing warning sign


Picture 7 – Notice the temporary supply cables at the fence, but that is a topic for another post.



There were 250 to 400 construction workers at site daily. Luckily there was no electrical accident yet. Really, really lucky.

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