Capacitance test

[lyledunn]

A senior engineer mentioned a capacitance test as a means of locating a fault on a 33Kv underground cable. Can someone enlighten me as to what is involved in such a procedure? Regards,

Lyledunn

 

[nbucska]

Why not use TDR (time-domain reflectometry ) ? <nbucska@pcperipherals.com>

 

[Lewish]

Cable has a certain capacitance rating per mile. For example, telephone cable is 83nF/mile. With a capacitance meter, measure the capacitance, divide by the rated capacitance per mile and that is the distance to the fault.
Only problem is, that is only accurate to about 10 per cent, which can be quite a distance.
To get really close, use a TDR.

 

[nbucska]

And you can't measure SHORTED cable, only open ones. <nbucska@pcperipherals.com>

 

[lyledunn]

nbucska,
Thanks, that was the point. The cable was shorted to earth. The fault was found in no time by pulse echo but I was interested to know about the capacitance test and if it is still used. Thanks all for info. Regards,

Lyledunn