what factors would determine type of cable

[paulthemagpie]

what factors would dtermine the type of cables suitable for the installation in a service trench?

thank you for your help

 

[Guitarist]

I know you need help with your homework, but with the greatest respect to yourself I think you need to read through the course material, the BGB plus any other books you have and find the answers all on your own. By all means run them by us for clarification afterwards, but I think we would be doing you a disservice just telling you what you need to write down. :smilewinkgrin:

 

[paulthemagpie]

okay thats fair enough!

some factors i can think off are:

mechanical stress and viberation damage.
ambient temperature
possibly the effect of moisture on the installation if its talking about the installation to the trench.

am i on the right path with these as they talking about TYPE of cables and not size

 

[Richard Burns]

OK you are now getting there, these can be classed as external influences (external to the cable not the trench). So then you need to determine the resistance of various cables to these external influences and so whether they are suitable for use.

 

[paulthemagpie]

great! thanks for your help.

so the fact the question just ask what factors can determin the type means the answer i give are correct and also the resistance of the various cables is another factor!

thanks

 

[Richard Burns]

Is the cable suitable for being installed in a trench?
Well it is a bit wet in there and it will get cold and when we pull the cable in it will get abraded.
Hmm.. what sort of cable can take getting abraded wet and cold?

So you have just classified the possible external influences and the assessed the cable type for those influences.

 

[SirKit Breaker]

With regard to cable current carrying capacities etc, you need to consider the C factor, and de rate accordingly.
No I am not trying to be clever, but look the tables up in the BGB, it will be a good exercise for you.
You need to find out which C factor you need, i think it is in symbols, then look up the right table for cables buried underground, then from that table choose the correct derating factor for your choice of cable, then you need to select the cable size to suit. I have given you a keyword in the paragraph, SELECT BGB part 5.

 

[Jack1995]

Hi there,

to calculate the fusing factor do i use the fuse rating or the prospective current?

Thank You

Jack

 

[Knobhead]

Where do you come in to the equation?