Stepping on electrical cables

[ProfT]

I recently had an incident where one of our mine operatives stepped on a submersible cable and it exploded (We later discovered that the cable was scavenged from the scrap yard). This cable was only carrying 20 A.

My initial thought was to bar everyone from stepping on cables even armoured XLPE cables. And then I also thought, I should put a policy in place that would prohibit stepping on cables. Now I want to run these suggestions by my boss, are these viable solutions?

 

[ScottyUK]

It's a mine. Do you really think a policy will prevent miners from stepping on cables? Your time would be better spent trying to prevent scrap cable from being re-used. Mining cable shouldn't explode when someone steps on it, or even when a loader runs over it. Who authorised use of scrap cable in the mine?

Forget about the cable 'only carrying 20A' becasue that is totally irrelevant. The condition you need to consider is the available fault current at that point, not the load current. It cound be many thousands of amps, perhaps tens of thousands.


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If we learn from our mistakes I'm getting a great education!

 

[ProfT]

Thank you scotty! Nobody authorised the use of scrap cables but the responsible electrician has since been brought to order. How can I determine the available fault current?

 

[ScottyUK]

You need to look at the source of the power and the impedance between the source and the point of the fault. Google 'fault level calculation' or have a look at one of the many texts on the subject. faq238-1287 is a good starting point.


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If we learn from our mistakes I'm getting a great education!

 

[megavolt120]

This goes towards the basic principle that in electrical work, it is either 100% right, or it's wrong. There is no gray area. I have people tell me all the time "WOW! what you do must be so hard!"...no it's not. Show me documentation from the cable manufacturer that it is ok to step on the cables...can't? then it is a no-step situation...