Substation main earth bar pictures

You will find below a few pictures of HV electrical substation’s main earth bar. I took these pictures inside a Consumer HV room at one of my recent building projects.

Picture 1 – Location of the main earthing bar inside a HV Switchgear Room




Observe the location and position of the main earth bar in the HV room. At every electrical room of significant size, at least one main earth bar like this should be provided.

Picture 2 below shows a closer view of this earth bar.

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Picture 2 – HV Room’s main earth bar



The purpose of having the main bar is simple.

All earthing conductors inside the HV room would be connected to this bar. That is the reason you can see in Picture 2 a number of ready-made termination holes complete with bolts, nuts and spring washers.

Notice the main copper earthing tape mounted along the substation wall in Picture 1. This is the main equipotential earthing conductor for this electrical room.

It should run through all perimeter walls of the room at a height of approximately 12 inch from the substation’s finish floor level. That is why you can see that in Picture 2 the left-most and right-most terminals have been connected with a horizontal copper tape conductor.

An ideal installation would have the main equipotential conductor run in a ring around the perimeter walls and both conductor ends connects to the main earth bar at the left-most and right-most terminals.

However, in this case it was not in a ring at the time this picture was taken because there was an entrance door at the wall in front of the 11 KV switchgear. Picture 1 was taken at the rear.

Later the horizontal copper tapes were connected into a ring by running additional conductor above the entrance door.

What are the conductors connected to the main earth bar in Picture 2?

The horizontal tapes at the left and right are what I have explained above.

The other three conductors have been installed vertically down into the cable trench.

(NOTE: Notice that the cable trench has been filled with river sand. Many installations prefer to have cable trenches filled with sand to avoid problems with rates and snakes playing hide and seek inside the cable trench.

Once a while these live beings find their way into the electrical switchgears and cause many problems including short circuits and intermittent trippings.

I have come across many operational problems because of these reasons.

To overcome these problems, many operation engineers prefer to just have all substation cable trenches filled with river sand. Then the trench is finished with approximately one inch of lean concrete on top of the sand and level with the substation floor.

When they need to do some work in the trench, they just knock down and break the thin concrete and dig out the sand.

No doubt this is a messy way of doing things, but it seemed to have been a very practical solution to these sorts of problems.)

Back to the earth tapes run vertical down into the cable trench. Where are these tape conductors for?

From the right, the first vertical conductor is connected to the HV switchgear equipotential conductors.

The center vertical conductor is connected to the earth busbar inside the switchgear compartments.

The last vertical conductor, at the far left, is the connection to the earthing electrodes outside the HV room.

Picture 3 – Disconnecting earth terminals



Some of the readers may not notice that the earth bar in Picture 2 is actually a two-piece bar. The two separate pieces are much more visible in Picture 3 above.

Notice that there is just one terminal (other than the terminal for connecting the two bars) on the short piece, while there are six terminals on the longer bar.

This has been designed to be so. The terminal on the short bar is called “disconnecting terminal”. The whole assembly is purchased readily assembled by manufacturer.

Usually earth bar with one or two disconnecting terminals are readily available. If an electrical contractor needs more disconnecting terminals, then it need to be ordered and it would be fabricated as required by the project at hand.

The terminals on the shorter piece are intended for testing and trouble-shooting purposes. That is why the conductor to the grounding electrodes is often connected to the short piece.

However, so clients forbid the use of the disconnecting terminals altogether. These sorts of clients usually manage many separate electrical installations with separate local operation teams.

It is usually not always easy to ensure an adequate level of competency of each member of the local operation and maintenance teams.

An earth lead conductor connected to the disconnecting terminal may easily lead to a total absence of connection to the earth electrode.

This presents a very serious safety risk.

This lead to a policy of forbidding the use of the disconnecting terminals. Therefore, all their substations would have single-piece earth bars.

Picture 4 – HV switchgear body earth conductor



This photo gives a clearer view of the switchgear equipotential bonding conductor.

As you may be aware, the switchgear came in separate smaller panels and the individual panels are then connected and bolted together at site.

The switchgear body earth (another name for the enclosure equipotential bonding) conductors, as indicated in Picture 4, have also been installed and bolted to each individual panel.

Therefore, these individual lengths of body earth conductors are connected and bolted to each other at the construction site.

The short inter-connecting copper pieces and all accessories including bolt-and-nuts for making the complete connection are provided by the switchgear manufacturer and shipped together with the rest of the panels.

Picture 5 – Bolt, nut and spring washer



This may be obvious for most readers, but some beginners may be silently screaming for help. So I labeled these components for them since they are such critical components in the electrical grounding system.

Picture 6 – Earth bar insulator post





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Pictures of electrical wiring

I have uploaded many pictures of electrical wiring to this blog. Now it has started to become difficult to find the pictures related to specific titles such as the wiring, etc. It will become worse as I send more post and pictures.

Picture 1 – Electrical DB wiring



Because of that, I will periodically send a post that will become an “anchor” for a specific title.

This title on wiring is one such example. Instead of being a normal post, it will generally function as the index page for posts and pictures of electrical wiring that I have sent to this blog.

So when you are looking for pictures of electrical wiring works, you can either look at the post list (i.e. BLOG ARCHIVE) at the right column of this blog page, or you can come to this post directly and scroll down to see if there is anything that interest you.

Of course, there is another way, which is by clicking the relevant “label” titles at the bottom of each page.

However, using the “label” will open all posts that have been tagged with that label in a single page. Readers with slow connections may not like the waiting when the pages are heavily loaded with graphics such is this blog.

Moreover, if multiple “labels” are opened simultaneously, readers with small RAMs may cause their computers to crawl, or even hang.

The best way is to come to an anchor post like this, which provides a short summary to posts related to a specific broad title. The graphic loading is also much less heavy because only one or two pics are added for each related post.

I have already send anchor post for other titles:

Temporary electrical installation pictures
Temporary electrical earthing pictures
Temporary lighting installation pictures
Electrical installation pictures


I will add more if there are more that three or four posts related to a specific title.

Now let’s get back to the DB wiring pictures.

Picture 1 show a house electrical DB with the cover removed.

Taken from this slightly lower angle, you can see the LIVE busbar of the DB.

Picture 2 below shows the wiring from the higher position. Here the outgoing wiring of the MCB’s (miniature circuit breakers) can be seen more clearly.

Picture 2 – Distribution Board Picture



I will not talk in detail about this wiring here. You can read a more detail description of the wiring at another post, 1-Phase ELCB Connection Pictures.

There are more pictures of this electrical DB there also.

Diagram 3 – Lighting layout and wiring details



Prior to installation of the electrical wiring conduit and trunking, the position of all fittings including the light switches, the socket outlets and lighting points must be determined.

Diagram 3 above shows examples where the light switches should be located.

I have sent a post with some pictures on the installation of lighting switches for office buildings here, Light switch installation pictures.

If you are looking for house electrical pictures, I have a post here, Home wiring pictures.

This article is not very good. It was actually a draft that I did at the time I started this blog. Suddenly something else demanded my urgent attention. That was why I did not have now post sent to this blog for a few months.

I posted the draft article anyway. I will come back to it some time soon with the final version and some pictures that may be useful for the readers.

Picture 4 – Internal wiring of an office DB showing the installation and wiring work in progress



Picture 4 shows the internal wiring of a DB for lighting and small power.

This DB was installed at a multi-storey office building. The internal wiring that has been done as shown was actually done at the factory.

That is why you cannot see any outgoing wiring from the MCB’s at the upper part of the panel.

You can see more pictures of this DB and other switchboards at this post, Switchboard earthing pictures.

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Electric shock injury pictures

I found these pictures of electrical injuries from one of the NIOSH websites. They were classified as in public domain and free for re-publishing.

So I put them here for those whose need them but have no time or the Internet skills to go around digging inside those massive websites themselves.

Picture 1 - Entrance Wound






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When an electric shock happens, the current enter the body at one point of contact and then leave the body at another point.
Therefore, two points of contact on the body are required for the electric shock to occur.
The two contacts will complete the electrical circuit, which will allow the shock current to flow through. (Read the post, Most basic principles of house electricity, to know the basics of how this works.)

At each of the points of contact, there is a resistance to the flow of current. The human body itself also presents resistance but this is normally low compared to the resistances at the two points of contact.
Just like the resistance in the filament of an electric bulb causes the filament to heat up, the resistances at these two locations caused the flow of the shock current to be converted into heat, which resulted in the severe burns that you see in Picture 1.

What the image in Picture 1 shows is the burn injury on the body at the location where the shock current flows in. The dark spot in the center of the wound is the entrance point.
This man was lucky. The shock current narrowly missed his spinal cord.

Picture 2 shows the injuries where the current leaves the body. Usually this is under the feet where they touch the ground.
The magnitude of the current when it enters the body is the same as when it leaves the body. If both feet touch the ground at the moment of the shock, then it is the total of the exiting currents at both feet.

In the case of Picture 2, it did not say whether both feet were injured. The foot shown here suffered massive internal injuries, that is not visible in the picture here. However, it was so bad that the foot had to be amputated a few days later.

Picture 2 – Exit wound


Picture 3 – Arc or flash burn



Don’t be there if you are not supposed to be there.
That is what I usually say to bystanders who hang around to witness the energization of a newly completed electrical system. It is always dangerous to be anywhere near the place because one of the most common types of accident there is electrical explosions.

The image in Picture 3 is one example of injuries from electrical explosions.
The NIOSH site said that man was near an electrical panel when the accident happened. He did not touch the electrical panel.

However, the electricity arched through the air. An example of electric arcs through the air is what we call lightning strikes.
Surprised? So you can consider this an injury from an extremely small lightning strike.

The man happened to be in the path of the arcing electrical current, so the current punched into his body. You may wonder why the injury is located at the armpit. That is because there were perspiration on his body at the time and perspirations are very conductive. So his armpit presented a very conductive (and therefore “very attractive”) path for the electric arc current.

Picture 4 - Thermal Contact Burns



Electric current not only heats up electrical wires that burn houses. If and when it travels through a human body, the points of contact where it enters and leaves the body can generate enough heat (due to skin contact resistances) to cause fire and burns the victim’s clothes.

That was what happened to the victim in this picture. The current exited the victim’s body at the knee. It caused fire at the skin there, which then catches his clothing and burned his upper leg.

Picture 5 – Internal injuries



This is an example of an electric tool accident. The worker was shocked by the electric tool he was holding. You can see from the picture the thermal burn injury at the entry point of the shock current.

However, the wound was even more severe that what can be seen here. Massive internal tissue damages have occurred that subsequently caused severe swelling to the hand.

The swelling usually peaks 24 – 72 hours after the electric shock. In this case, the hospital needed to cut open the skin on the arm in order to relieve the pressure that resulted from the swelling, which could have damaged nerves and blood vessels. This image in Picture 6 below was after the skin was cut open a few days later.

Picture 6 – A few days later



Picture 7 - Involuntary Muscle Contraction



This worker was working above overhead electrical cables. For some reasons he fell and grabbed the bare cables in order to save himself. The resulting electric shock mummified his first two fingers, which later had to be removed.

The acute angle of the wrist was caused by the burning of the tendons, which had contracted, drawing the hand with them.

Browse around other posts that I sent to this blog. You will find pictures of “bad electrical installations” that can lead to accidents and electrical injuries shown by the above pictures.

How much shock current does it take to cause the above injuries?

Keep on reading.

I have collected some data from the websites of relevant authorities, which you can see below.

Effects of the electric shocks

Listed below are the effects of electric shocks starting from the lowest amount of current flow to the highest for a duration of one second at typical household voltages.

1 mA - A normal person will feel a slight tingling sensation.

5 mA - A light shock will be felt, but most persons will be able to “let go”. Not a painful feeling, but definitely disturbing. However, a strong reflexive movement by the victim can cause further accidents and other type of injuries.

6 to 30 mA - The victim can be paralyzed, or the muscles will freeze (will not be able to release a tool, wire, or other object

Painful, and my not be possible to let go.

At high voltage (above 600 Volt, this current can already cause severe burns)

Women start to suffer the effect at lover current levels (6-26mA), while men can sustain until a bit higher (10 to 30 mA)

30 mA - Will cause respiratory paralysis
(The victim stops breathing for a period of time)

30 mA - This is the most sensitive rating of Earth Leakage Circuit Breakers (ELCB) normally installed in residential home in this country.

50 to 150 mA - The victim get an extremely painful shock.
The breathing stops (respiratory arrest).
Severe muscle contraction: flexor muscles may cause holding on, extensor muscles may cause intense pushing away.
Death is possible.

(At 75 mili-Ampere and above – The victim undergo ventricular fibrillation (very rapid, ineffective heartbeat). This condition can cause death within a few minutes. The only way to save the victim is by a special device called defibrillator.)

1 A and above - Uneven heartbeats occurs (Ventricular fibrillation).
The muscles will contract.
Damage to the nerves.
Death is likely.

4 A - The victim gets heart paralysis, which means the heart stops pumping.

(Highlight: How much is 4 amperes? If you connect a 1KW portable space heater to a wall socket outlet, and your house supply from the electricity company is 240 Volt, then that’s about 4.1 amperes running inside the wires from the socket to the space heater.)

5 A and above - Human tissues get burned.

10 A and above - Cardiac arrest and severe burns.
Death is probable.

Note: The above medical data has been obtained from the National
Institute for Occupational Safety and Health (NIOSH)

13 A - The lowest current a typical plug fuse will blow in a socket – plug supply connection.

15 A - Lowest level of current a normal circuit breaker or fuse will trip at a home distribution board, or a house electrical panel.
Further explanations on the electric shock injuries
The higher the current, the longer the time of the shock current, the more severe the injuries

(a) As you can see above, the higher the current that flow through a human body, and the longer it flows, the more serious the injuries.

If the shock is short in duration, it may only be painful. A longer shock (lasting a few seconds) could be fatal if the level of current is high enough to cause the heart to go into ventricular fibrillation.

100 mili-ampere current flow (that is one tenth of an ampere, or 0.1 Ampere) through the body will kill a person in just 2 seconds. Maybe he does not die immediately, but death is almost certain after sustaining 100 mA for 2 seconds.

(b) A person can only withstand less that 10 mili-amperes and still have control of his arm muscles. Beyond that, he no longer has control over his arms. That is the reason he cannot let go of the faulty tool he is holding (the hand may even tighten the grip on the electric tool), resulting in longer flow of shock current through the body thereby making the injuries more serious.

This situation when prolonged will lead to respiratory paralysis (the muscles that control breathing cannot move.)

That is part of the reason for the requirements to have install Earth Leakage Circuit Breakers (ELCB) for circuit supplying electrical tools. The ELCB can detect very small amount of leaked electrical current and trip that circuit within a fraction of a second thereby saving lives.

A severe shock can cause much more damage to the body than is visible. A person may suffer internal bleeding and destruction of tissues, nerves, and muscles.
Sometimes the hidden injuries caused by electrical shock result in a delayed death.
If a shock current is maintained long enough at a relatively high current, death is probably not avoidable.
But if somehow the contact area to the electrified object is broken fast enough and the victim’s heart has not yet been damaged, his normal heartbeat may return, even though this type of recovery is rare.

The severity of injuries depends on which part of the body does the shock current flow through

The most serious effect is when the current flow through the heart.
If a live wire accidentally touches the body by contact at the head, the nervous system will be severely damaged.
If during the accident the victim’s right hand touches the LIVE wire, while the left hand is holding the metal casing of the washing machine, the electrical current will flow through the chest. Then the lungs and heart will probably be injured.

Of course how severe will also depend of how many mili-amperes and how long the shock current flows.

If the current only flow through the arm portion, then the injuries can be as bad as the arm coming off while the victim still survive (not dead). There have been actual cases like these in high voltage accidents.

If the current does go through the chest, the person will almost surely be electrocuted.
A large number of serious electrical injuries involve current passing from the hands to the feet. Such a path involves both the heart and lungs.

This type of shock is often fatal.

A higher skin resistance will lower the shock current.

(a) Again the current is inversely proportional to the resistance. If the victim’s body is dry, then the shock current through his body will be lower. Then the injury will be less severe.

The resistance of a dry skin is can be 100,000 ohm or more. While that of a wet skin is only approximately 1,000 ohm.

At 600 volts, the dry skin resistance will only allow 6 mA at the most, while the wet skin can allow 600 mA to flow through the body.

Compare this to the list of injuries above and you can appreciate the extreme importance of dryness in the effort to avoid electrical shock.

Even at 240 volt, the wet skin will allow 240 mA to flow through the body, making very severe injuries and even death possible.

(b) Other than wet skin, wet working conditions will also have the same effect because they can make the skin wet and reduce resistance. Likewise, a damaged or broken skin.

(c) The resistance will also be reduced in direct proportion of the cross-sectional area of the path current. This means that when the contact made to an electrified object with an applied force as opposed to touching it with the tip of the fingers, the contact area will be larger. Therefore, the resistance to the current flow will be lower and the shock current will be higher.

Very Low Voltage also can kill
(a) The severity of the injury can increase the longer the victim is exposed to the shock current. Because of that, even low voltages can be extremely dangerous because the degree of injury depends not only on the amount of current but also on the length of time the body is in contact with the circuit.

Some victims have stopped breathing when shocked with currents from voltages as low as 49 volts.

For example, a shock current of 100 mA applied for 3 seconds can cause injuries as severe as a current of 900 mA applied for a fraction of a second.
(b) The victim’s muscle structure also plays a factor. People with less muscle tissue are typically affected at lower current levels.

The higher the voltage, the more serious the injuries.

(a) A current flow is directly proportional to the voltage supplying the current. That is why the higher the voltage, the higher the shock current flowing through the victim’s body. Therefore, the injuries will be more severe.

(b) At high voltage (i.e. 600 volts), the shock current can be as high as 4 amps. That amount of shock current will damage the hearts and other internal organs. In addition, internal blood vessels may clot, and the nerves in the area where the skin touches the electrified object may be damaged.

(c) High voltages can also cause severe tissue burns. A strong shock at the limb can cause the limb to come off.

Higher voltage can cause further accidents, therefore additional non-electrical injuries.

(a) Sometimes high voltages can lead to additional injuries. High voltages cause violent muscular contractions. The victim may lose his balance and fall, which can cause further injury or even death if he falls into machinery that can crush him.

(b) Bones can be fractured as a result from extreme muscle contractions during the shock, or cause by falling from working height.

You can see installation conditions that can lead to these injuries. Visit Temporary electrical installation pictures; Electric panel installation pictures; Multi storey building electric closets; Electrical installation pictures.

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How To Test An Emergency Light

An emergency light (EL) is an emergency equipment.

Like all emergency equipment, we do not need it unless we are in a state of emergency.

Picture 1 – An emergency light fixture

It is also a safety equipment, which means that we need it to prevent danger, to reduce the risk of personal injuries, to prevent loss of lives or properties.

There is a problem common to most emergency or safety equipment. It is not used or not in operation most the time. In other words, it is always on standby.

This is how the problems develop.

When an equipment is seldom used or operated, it may not work at the moment it is supposed to work.

Poor workmanship during installation, low quality components, etc may cause failures in parts of the equipment.

These failures are not noticed until an emergency situation arises. Then it would already be too late.

Another example is the standby electric generator. Many buildings rely on the standby generator as part of the fire protection system for the building.

However, because it is seldom used, many times the generator cannot start when there is a fire and the main supply fails.

Of course, we have the emergency lighting to aid us in evacuating the building.

But then again, what if the emergency light also fails at some place in the building?

The occupants in the room can be left in total darkness. Accidents can happen which will make the situation much worse.

This is why the emergency light should be checked regularly and it is easy to do it.

How to test an emergency light

Picture 2 – A close up view of a surface-mounted emergency light



Picture 2 above shows the close up view of the emergency light in Picture 1.

MAINS HEALTHY light

The MAINS HEALTY light is an LED light. Under normal condition, this LED would give out red light. I took this picture while the building is under construction. The mains electricity from the public supply is still not connected. That is why this LED did not light up yet.

If the red LED lights up, that means the building supply is connected to the EL light unit. Therefore, the rechargeable battery inside the unit is charging.

The battery is always charging to keep it at full charge all the time. There is an electronic circuitry inside the fixture that automatically charges the battery to keep it full all the time.

However, even when the battery is fully charged, the LED stays ON. Do not expect the LED to light off when the battery charge is full. This light only says that the electricity supply is available.

In some design, the LED may also be used to say that the internal electronic charging circuit is also working properly. In other words, it summarized the status of the health of the charging part of the EL light fixture.

The TEST pushbutton

This pushbutton switch allows you to check if the lamp would light up when the building electricity supply really fails.

To test it, just press the red pushbutton switch.

The EL lamp will light up.

With the charging circuit healthy and the operation test of the lamp also okay, you now have no worry about your emergency lighting.

With recessed mounted EL lights, the test is also similar. Picture 3 below shows a ceiling-recessed EL light.

Picture 3 – Ceiling-recessed emergency light




You can see more pictures of the emergency lights at this post, Emergency lighting installation pictures.

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Temporary lighting installation pictures

A construction site’s temporary electrical installation must provide adequate lighting for the activities that are carried out at a particular workspace whether indoor or outdoor.

Picture a1 - A site temporary lighting with mobile generator

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Arguably more important than the light levels, the temporary lighting installation should be sufficiently safe for use and provided with adequate protection to prevent electrical shocks.

A. SITE TEMPORARY LIGHTING

Picture 1 – Indoor temporary lighting and wiring

Picture 1a – Temporary lighting – Bad cabling installation


Picture 2 – Another temporary lighting and wiring indoor



Picture 3 – External site floodlight



1) Mechanical protection

In general, equipment for use at construction sites should be tough enough to withstand the abuses of work area where they are installed. Damaged light

fittings not only result in the repair cost, but they also present risks of electrical shocks to workers using them or those who are nearby.

For temporary lighting, they can be installed out of reach of human hands or any construction materials that are handled in the area. Also from equipment and

machines being operated there.

Another easy measure is to use wire cages type of lighting fixtures.

Precautions should also be taken against the danger of electrical fires that may result because of damaged lighting fixtures or the temporary supply wiring.

2) Supply from a separate section of the distribution panel

The temporary wiring supplying the lighting circuits should be connected to the special lighting section on the temporary switchboard. These circuits should

be protected by 100 mA RCD (residual current circuit breakers).

3) Mechanical support of the wiring

The installation of wiring for the temporary lighting should be carried out with proper supports and fittings to allow for wiring cables to be routed in ways

that minimize obstructions, which can results in damage to the luminaries and wiring.

These damages can present shock risks to the works and possibilities of electrical fires.

4) Normal duty lighting

Normal duty lighting circuits are installed to provide general illumination for work and allow safe movement inside and around the construction site.

5) Lighting levels

An illumination level of 10 lux is adequate for general movement within a building under construction.

As a simple example, one length of 100 meter festoon light string fitted with 20 nos 100 watt lamps at 5 meter intervals will give a 10 lux over a

rectangular area of 25 meter x 30 meter.

6) Use of festoon lighting

Festoon lighting should only be used strictly in underground shafts, wells and tunnels.

When this type of lighting is used, the lamp holders should only be the moulded, non-removable type (the lamp holders are bonded or moulded to the wiring

cables) and the lighting supply voltage is 32 Volts or below.

7) Supply to lift shaft temporary lighting

Either a temporary wiring or the newly installed permanent electrical wiring may be used to supply a lift shaft temporary lighting.

However, the light fittings used should be properly guarded against accidental mechanical damage and they should only be connected to the wiring using a

lighting plug and socket.

These lights should be installed at intervals of less than nine meters along the vertical length of the lift shaft.

The control of the lift shaft lighting should be by means of two-way switches located near the shaft access points.

8) Use of SELV voltage

The use of lighting circuits supplied at safe extra low voltage levels (SELV - voltages less than 50 volts ac or 120 volts dc) is highly recommended for

working in confined spaces where workers faces high possibilities of frequent contacts with temporary electrical equipment and wiring.

B. TEMPORARY SITE FLOOD LIGHTING

Large construction sites usually need temporary floodlight towers (in addition to the temporary lighting inside the new buildings) to provide lighting

efficiently for the general movement, safety and security on the external areas of buildings under construction.

The lighting towers will usually takes the form of fixed tower or mobile tower units. Which one to use usually depends on the siting positions available for

the lighting tower units and the duration of the contract.

For contracts with construction periods of relatively short durations, it may be much more economical to use mobile tower units.

However, if contract period is long, then it may be worth some considerations to use fixed height tower units. In any case, the fixed height towers can still

be reused on future projects. Careful dismantle the fixed height static towers at the end of the contract. Then the only extra material that is required in

at the next construction site is the foundation.

Static floodlighting tower units are normally available up to 18 meter high. They can be powered from the mains supply and they can be provided with their

own electric generator.

The external areas of a construction site usually need a lighting level of around 20 lux average. This is the level sufficient of for the handling of

construction materials and site clearing works.

A rectangular area of 60 meter by 60 meter can be lighted up to this light level by a typical 18 m tower carrying four units of 400 watt high pressure sodium

fittings.

A main contractor with larger contracts and relatively longer contract period may want to consider a more elaborate study on their site lighting

requirements. If there is enough space to mount these floodlighting tower units, a proper lighting engineering study can be carried out together with the

overall temporary electrical installation.

The exercise would employ the floodlight lamp data, the aiming angles of the light fittings, and the mounting heights of the individual fittings to arrive at

the required overall illuminance.

These static towers would normally employ high intensity luminaries and with the type of equipment available today, the contractor can now light areas to

sufficient level so the works can continue in evenings of the darker months. This is significant because it can considerably reduce the contract time.

Light fittings used in this application would necessarily be high intensity discharge type and the high pressure sodium lantern have become the more dominant

type due to its high lighting output per kW of power usage (approximately 125 lumens per watt).

A tungsten filament lamp would give only 22 lumens per watt.

The capital cost of choosing the high-pressure sodium equipment is considerably higher than the tungsten halogen, but the main contractor may do well to

consider other factors also such as the running cost, installation cost and the lamp life.

At the end of the construction work, all these equipment except the tower foundation can be dismantled and transported to other project sites for reuse.

You can see below a few pictures of a small mobile floodlight unit and other types of temporary site floodlights:

Picture 4 - Mobile site floodlight unit


Picture 5 – Luminaries of mobile flood lights


Picture 6 – This is a permanent floodlight, not a temporary one



Picture 7 – A closer view of the 400 watt temporary floodlight in Picture 3



C. SITE TEMPORARY ELECTRIC SUPPLY

A site temporary lighting is actually part of its temporary electric supply installation.

The term ‘temporary’ brings up a vision of a length of twin and earth cable, or a four-core twisted cable and an undersized green earth wire, that is connected into a 30A single or 4-phase and neutral switch-fuse, trailing across the rough ground of the construction site to terminate into a seasoned self-fabricated distributed (with or without metal-clad enclosure).

On the so-called ‘distribution board’, a length of three flexible extension cord is connected to a clumsily assembled socket outlet with or without the use of a three-pin plug.

How would you connect a three-core extension cord to a three-pin 13 A socket outlet?

Somewhere on this blog, you can see clearly how it is done. It even has had various ways of doing it.

The extension cord run at high level near the soffit of floor slab, or some just run on the scattered floor to a temporary metal-clad 13A switched socket outlet some 30 meters away.

The construction contract cost hundreds of millions, but the temporary electric supply system has been ‘engineered’ to fulfill all the site electrical requirements for the minimum price possible.

The main contractor has the responsibility to ensure the temporary electricity supply system installed is not only functional and meets all his electrical needs, but also safe for all involved in the construction work.

The supply system need to be good enough to provide reliable power distribution, whether that period of the construction contract is three months or three years.

Or whether the site supply requirement is 4 kVA or 3-megawatt supply.

What specifications to use for the temporary electric supply equipment?

Generally, what applied to low voltage installation is in the IEE Wiring regulations also apply to the temporary supply system.

However, two more British standards should be used to cover the gaps not covered there: BS 4363 (Specification for distribution units and electric supplies for construction sites and building sites) and BS 7375 (Code of practice for distribution of electricity in construction and building sites).

Source of the temporary supply

The temporary electric supply can be obtained from either the distribution network of the local electric supply authority or an independent electric generator installed at the site. Which one to use is usually just a matter of judgment on the cost involved.

However a few other factors may also need to be carefully considered which include practical problems that are usually associated with the distribution of the electric power safely and effectively throughout the site.

If the supply is taken from the local electric supply authority, a lead-time is usually required, as the authority would need time to arrange for the connection.

The main contractor also need to submit sufficient details on the peak demand that will be required during the course of the contract, the positions of the point of supply intake and also the estimated contract period.

The authority usually requires enough details on the types and size of electrical load, e.g. lighting, heating, motors, etc. Motor loads usually need more details such as types of motors and the method of starting (direct-online, auto-transformer starting, etc).

Update (March 15, 2014): I have a collection of pictures on temporary lighting that I have not yet uploaded anywhere. I plan to just progressively attach the pictures below in this post with a brief comment for each picture.

This way I do not need to write a post just for the purpose of sharing the pictures.

xxx MORE TEMPORARY LIGHTING INSTALLATION PICTURES xxx

Picture 08 - Temporary flood light installed at high level of a rail workshop under construction

This picture show flood lights installed at the high level of a rail workshop under construction.

Actually this temporary lighting has only recently been installed. Electrical supply wires were still dangling around and not properly fixed.

However, the main contractor were pressing for progress and I did not wish to look like a bad guy there. So I just let them use them first to help them gain some additional progress before I apply more pressure for the temporary cable to be properly fixed.

In any case, the dangling cabling were mostly at the higher level of the work area.

This is not to say that the risk of accident was minimal. As you can see in the background of the picture, there was a mobile sky-lift being used to install the fighting pipes just below the roofing of the workshop.

In some days, there were quite a number of the sky-lifts throughout the workshop floors.

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