Fault on underground Sub Mains cable

[kibble19]

Hi,

I am currently in the middle of completing a new installation in time for a Halloween event at a local activity centre. Over the weekend, while I was not there, it seems that they have lost power to the sub mains distribution panel.
Unfortunately I didn't have my Megger to hand yesterday as it is being calibrated, I will get it back later today, so I couldn't test the cable.
I have 400V across all three phases and neutral at the Sub station end, protected by 3 x 300A BS88 fuses. The 120mm 4Core SWA is buried direct in to the ground and runs 530m. At the other end it is connected in to a PowerPact panel. I have no voltage at the panel end. The fuse chamber was still in the on position at the sub station, but upon testing to see if I have voltage at the distribution panel end I only have continuity beep between all three phases and neutral.
I did notice that L1 fuse has blown, which I replaced yesterday but still no voltage.

I feel that the cable must be damaged underground, but I don't see how it can stay on at the fuse chamber? Any ideas?
I will be able to test the cable later today.

Also if it is damaged underground, does any one know of any tester out there to find the section of damaged cable, as its a 530m run and digging that back up will be costly!!

 

[Rocboni]

Yes I'm thinking the same, and in my opinion you are correct.
But in the interests of 'being nice' I'm staying quiet so far.

In the interests of 'being nice' also i'll say no more....

 

[Pete999]

Stick a few hundred DC Volts up one end and watch the ground shake where the fault is.

 

[telectrix]

few hundred. 5kV should shift some dirt.

 

[StephenRowley]

Stick a few hundred DC Volts up one end and watch the ground shake where the fault is.

function gen a oscilloscope, look for the reflection, do the maths and bingo you'll know where the cable break is(good Luck)

 

[telectrix]

function gen a oscilloscope, look for the reflection, do the maths and bingo you'll know where the cable break is(good Luck)

long sds bit. drill down along the run. when the sds bit stops going bang, you've found the break.