Tower Crane Problem-Electric shock felt at hook?

Question

Please help
an electric shock is felt at the hook:
1. cant get a voltage reading at the hook
2. everywhere on the crane is bonded
3. RCD does not trip
4. the Tower Crane is earthed at the base; all parts are bonded
5. shock is felt even when Tower Crane main supply power is cutted off
6. suspecting that the wire drum is storing the static, but how?

anyone has experience this before and can offer some advice?

Answer 1

The cable is building up a static charge. That's why you're unable to get a voltage reading.

Check all the ground and bonding connections. Pay special attention to anything that contacts the steel cable -- from the wire drum all the way to the last pully.


Are there any electric transmission or distribution lines around? You could be building a charge off the electric fields of the power lines. Depending on the voltage, you can even get a charge if you're more than 20 feet away.

Answer 2

I have three children with disabilities. There is no way I would allow an institution to torture my babies. There are other methods. The school and the parents are the truly handicapped in this case. Between the teachers and the parents, children with disabilities can be helped and taught to act appropriately.

Answer 3

Electrostatic my guess is, it's not grounded as good as you think it is :) Better grounding, Use ground straps on anything that moves/slides.