Working with E-equipment is becoming increasingly common as a result of the energy transition. Even before the arrival of E-equipment, dangerous situations involving electricity were a regular occurrence - sometimes with severe consequences. An electric current is not visible, but improper handling can have major consequences.
Consider the following example: Imagine you have been working in the garden. You want to disconnect the garden hose. Whilst disconnecting the garden hose, you discover that you had not yet turned the tap off. When you disconnect the garden hose, the water from the tap sprays out and you get wet. Fortunately, in this example, the worst that can happen is that you get wet as a result of water spraying from the tap. The situation is very different when we consider wires with a current running through them. When you disconnect a wire that still had current flowing through it at the time of disconnection, then you cannot see the current being ‘released’. At this point, you are at risk of suffering an electric shock, or an electric arc may occur. This can result in life-threatening situations.
For this reason, it is important that all employees who prepare and perform activities near and using E-equipment are aware of the risks that can occur when working with live current.
The target audience for this toolbox is:
- Colleagues who perform activities with and around E-equipment at the construction site
- (Head) Foremen
- Work planners
- Project coordinators
- Project managers
- Construction site managers
N.B.: If you do not feel comfortable giving this toolbox to someone, then ask a work supervisor (WS) or installation supervisor (IS) for assistance!
For additional background information, please refer to the toolbox on electrocution and electric arc. This toolbox also contains a video in which an electric arc is simulated.
Electric arc
An electric arc is the sudden release of energy by an electric current, usually as a result of short circuit. An electric arc results in the release of a large quantity of heat, light, sound, pressure waves and toxins. As a result, an electric arc can best be compared to a small explosion, with a risk of very severe or even fatal burn wounds or poisoning. The heat that is released can reach extremely high temperatures (up to 20,000 degrees Celsius!).
The images shown below and the video examples referred to above provide examples from installation technology settings. However, an electric arc can just as easily occur when you remove a plug or charging cable from a piece of E-equipment. The risks and consequences are just the same!
Electrocution is a harmful flow of electrical current through the human body or an animal, resulting in death. The same incident is referred to as electric shock if it does not result in death. Consequences for the victim – depending on duration and amperage – can vary from difficulty breathing to burn wounds or severe heart rhythm abnormalities.
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| Diagram of electrocution/electric shock affecting a person | ||
Refer to the toolbox What to do after an accident involving electricity for additional information.
Burnout of plugs | batteries
A malfunction or large resistance (overload) can result in cables or batteries becoming too warm, of even igniting. The financial consequences of a burnt out battery or plug can vary from tens to millions of euros, depending on the equipment.
The image below depicts a burnt out E-cabinet at a Heijmans project. Someone attempted to move this cabinet whilst it was still connected to mains power.
Explanation
The fact that a plug fits does not automatically mean that a plug
can be connected. If an incorrect plug is connected, this can result in a short circuit. A short circuit can cause a plug to overheat and burn out. One example are the cheap charger plugs that the Dutch frequently import from other countries. The plugs fit on our phones and will even charge our phones. However, these cheap plugs cause hundreds of house fires every year.
Do
Ask the foreman or work supervisor (WS according to NEN3140) who is authorised (VOP or VP) to connect plugs for a project.
Explanation
If the plug is still live, this can cause an electric arc. As explained previously, an electric arc can result in a large amount of heat, light, sound, pressure waves and toxins being released. In other words, pulling a plug from a cabinet when it is still live can result in you sustaining burns and/or being poisoned.
Do
Check who is authorised to connect and/or disconnect plugs. If you are authorised to work with plugs, you should perform an LMRA to check whether the electrical device that you want to disconnect from the cabinet is switched off.
Explanation
If too many plugs are connected to a cabinet simultaneously (for example a mushroom), then this can cause too much current to flow through the grid. This causes the source to become overloaded. A fire can then occur as a result of the electrical wires becoming too warm. The risk of a fire occurring as a result of overloading when using E-equipment increases as the power of the equipment used increases.
This happened at a Heijmans project in March 2023. A cabinet had been installed at the project as a temporary power supply. Agreements were made in advance about the capacity of the cabinet. A colleague who was not properly informed about these agreements connected too many devices simultaneously. This caused the cabinet to become overloaded. The plug and the cabinet connector burnt out (luckily without personal injury).
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| A burnt out plug at a Heijmans project. | Burnt out 125A wall socket on a generator to which the plug was connected |
Do
Check who is authorised to connect and/or disconnect electricity-consuming equipment to/from a cabinet. If you are authorised to connect and/or disconnect electricity-consuming equipment to/from a cabinet, then – before you connect it – you should check the capacity of the cabinet and how much of that capacity is already being used before you connect a new piece of equipment.
Explanation
The use of (il)legal extension leads increases the risk of overloading the cabinet. As described above, overloading a system can cause the electrical wiring to overheat, resulting in a fire.
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| The use of an illegal extension lead can overload the system. This can cause the plug to catch fire. | Looping connections and the use of an illegal extension lead can result in overloading the system. |
Do
Check who is authorised to connect and/or disconnect plugs. If you are authorised to work with plugs, ensure that you provide a suitable connection so that extension leads are not required.
Explanation
If a cable or cabinet is potentially live, then it is not a good idea to move this cable or cabinet. The movement can cause something in the wire or the cabinet to dislodge. In the worst case scenario, this can result in an electric arc, or you can be electrified by the current that is ‘released’.
Do
Check who is authorised to move cables. If you need to move a cable, always check with the foreman or the work supervisor. A cable or mushroom that needs to be moved should never exceed 32/63 ampere! Perform an LMRA. Check whether the cable has been disconnected. Switch off all electricity-consuming equipment (construction saws, pumps, etc.). Remove the switched off equipment from the mushroom.
If you have any doubts or are unsure about anything: do not proceed!
Explanation
Having been advised against it by the installation supervisor (IS), employees tried to extend a cable during contract work. This resulted in overloading due to the extra resistance on the cable and a burnt out plug.
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| The burnt part of the plug is circled, with one pin having sunk completely into it. |
Do
Follow the instructions of the installation supervisor (IS) and/or the work supervisor (WS according to the NEN-3140). Installation technology is a completely different field to the conventional technology that has been used to date. For this reason, it is not (yet) possible to gauge certain hazards.
Explanation
Even though it is not permitted, we still occasionally encounter safety features that have been bridged during work using conventional equipment (e.g. keeping an automatic setting engaged with a stick). DON’T DO IT!
If a safety feature is bridged, this can result in a short circuit. This increases the risk of an electric arc, electrocution or material damage. The fact that a safety feature has activated means that something is wrong!
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| This photo shows the bridging of a safety feature by placement of screw drivers. This is extremely dangerous! |
Do
Down tools and contact the foreman or work supervisor (WS according to NEN-3140). They will send a qualified employee to the construction site to investigate why a safety feature has activated.
Explanation
If a malfunction occurs, then the equipment may stop working (temporarily). You may be tempted to resolve the issue yourself, due to high work pressure and tight deadlines (and costs). This was often done in the past with diesel powered equipment. However, in the case of E-equipment, current may still be ‘leaking’, which means that the entire device is electrically charged. This results in an increased risk of an electric arc, electrocution or material damage.
Do
Down tools and contact the foreman or work supervisor (WS according to NEN-3140). They will send a qualified employee to the construction site to rectify the malfunction.
Explanation
An electro-technical issue may indicate that current is ‘leaking’. The earth pin ensures that any current that escapes is conducted to the earth. If there is no earth pin or it has been removed, then the leaked current cannot flow to the earth. In that case, if something becomes charged (for example, due to a small crack somewhere in the system) and you touch something, then you become the earth pin. Which means you will become electrified.
Do
Earth pins should never be moved without reason. They must always be subjected to diagnostic testing to ensure that they are working properly. If an earth pin needs to be moved or temporarily removed, then a plan must be created with the work supervisor (WS according to the NEN-3140). The current is completely switched off temporarily. Once a new location has been found for the earth pin, it needs to be fitted by a qualified individual. Work can only be safely resumed after the earth pin has undergone diagnostic testing to confirm that it is working correctly.
Explanation
When moving loose batteries, we are legally required to transport them under ADR9 (transport of hazardous substances). This is due to the fact that the substances in the batteries can be harmful to the environment.
Batteries contained in electrical equipment are exempt from the ADR9 requirements.
Do
Check whether the loose battery packs are being transported according to ADR9.
Unfortunately, minor and major incidents can occur, despite the measures that we all take to prevent them. You can read below what you should do in the event of minor and major incidents. The following always applies: TAKE CARE of your own safety!
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| The photo above shows a buried cabinet. |
- A pinched cable;
- A box placed on top of a cable;
- A cabinet that has accidentally been buried;
- Damaged cables or plugs;
- Etc.
As you will have read in this toolbox, even these smaller incidents can have major (sometimes even life-threatening) consequences. Therefore, it is important that you report such smaller incidents to the foreman or work supervisor (WS according to the NEN-3140) as soon as possible. This allows for the incident to be resolved as quickly as possible, so that the work can be resumed safely.
STEP 2: Contact the emergency services, if necessary. Contact the fire department in the case of a fire in a battery pack, there is no point trying to extinguish this yourself.
STEP 3: If a colleague or a person has suffered an electric shock, they should always go to the hospital!
Discuss the following topics with each other:
- Do you, or your foreman, know who the installation supervisor (IS) is for the construction site installation?
- Are you always aware of who your work supervisor is ?
- Do you know who on the project is authorised to work with cables and electrics?
- Do you know when current is flowing through a cable?
- Do you know what minor incidents are?
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