electricalforum.nz

We have a installation in a rural area. A new shed has been built around 400m from the point of supply.
The mains are 240AL tailed down to 16CU at each end.
During installation BEFORE any connection to the network the guys doing the jointing between the CU and AL were getting shocks from the cable, we found that the electric fence for the property was inducting enough power to cause this (we turned off the electric fence and it stopped).

Anyway the electric fence is a real powerful unit, it on a Bull Farm - like cows, but way more aggressive, the display indicates it is delivering 17kv pulses. The mains when run passes under the electric fence several times over the 400m run.

Anyway the problem has became a bit more obvious when the building end neutral was connected to the N-Bar. The network connection had since been done (it was on a builders temp), a noticeable tingle was received between the unconnected Neutral and the N-stud in the switchboard.

the question is, how can we reduce or eliminate the induced voltage from the electric fence?

I would have thought that if the star point at the transformer is earthed and you have a MEN and earth electrode at the builders temp every should be ok.

On the dairy farm I have worked on we had 5KV at best and the run off for it was 9KV.
9KV was enough for the bulls (and myself) that we had.

17KV sounds a bit high, you could try seeing if the unit has a lower voltage option.

Have you IR tested the cable to earth? Just in case its not inductance.
Another thing is check that the unit is earthed properly(according to MIs which will be more than 1 earth stake).


Slightly OT What sort of unit do they have?

Remember this is not a dairy farm, it's a bull farm and they are very stroppy that's why they have a electric fence that packs a wallop

IR tests are great, it's definitely induced, it's been that way since the day it was laid in the ground and before it ever was connected.

As far as earths for the e-fence, they put down 12 earth pins as per the recommended MI's - I quizzed them on that today while on site.

I don't know the brand of e-fence

Suggest trying an SPD to divert those spikes to earth.