In this toolbox we will discuss grounding.
If a crane, concrete pump or piling rig could hit the overhead line if it topples, a grounding system needs to be put in place. This grounding system protects employees if the crane collapses and lands on the overhead line. Compared to a fuse being blown at home, it is different when it comes to an overhead line. The power (1800 V or 25 kV) might stay on it.
An expert (installation and work supervisor based on ProRail guideline RLN00128-2) must establish if a grounding system is required. Only this person can grant a potential exemption.
This needs to be established well before the work is started. This way, measures can be taken in a timely manner and work can be done/carried out safely.
If a crane is equipped with a grounding cable and the crane has to be driven/moved, help guide the cable so it does not get detached or broken.
If the crane is detached from the rail, inform the site manager and use another grounding point.
Lightning
In case of lightning, the rule applies that when there is less than 10 seconds between the sound of thunder and the light flash, you must take shelter, for instance in the management cabin. The risk of lightning striking is too big. This risk even increases when there is an overhead line present!
A grounding electrode needs to be installed. This grounding electrode (a pin in the ground or in a sheet pile wall) protects the signalling and other installations. With a grounding electrode in place, the installations are protected in case of lightning striking the machine.
Example
The machine is within falling range of the high-voltage installation (overhead line).
- A connection needs to be made with the retour (negative leg rail). Additionally, the machine must be protected against lightning at all times.
- The safeguards against hitting the overhead line and the safeguards against lightning strikes are combined. Always check the following:
- Is there a connection between the track and the over voltage protection circuit (Soule CLS)?
- Is there a connection between the over voltage protection circuit and the grounding electrode (grounding pin next to the soule or sheet pile wall)?
- Is there a cable available from the grounding pin or sheet pile wall to the machine?
Is the answer: NO. Immediately contact the site manager.
The length of the cable may not exceed 65 metres. This cable must be short-circuit proof and reliable. The connection, that is made in an instant, guarantees that a short-circuit is created in case the machine collapses and hits the overhead line. Furthermore, it is protected against lightning.
In case of an emergency:
Should something fall onto the rail or get stuck on a level crossing! Alert the train driver by waving a red flag or something else. Wild arm gestures and waving your tabard also helps.
Make these gestures standing next to the rail at no less than 1000 metres distance from the incident. Send a colleague in the opposite direction to do the same.
Always see to your own safety and follow the steps on the alarm card!
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