currently carrying out pir on small commercial building on an industrial estate. main board is fed by 25mm 4core from a 100a bs 88 switch fuse in an outbuilding. this switch fuse is fed via a 50mm 4 core which goes off to a substation on site which we have not got acsess to and dont know how is protected or connected. problem starts here - zs at db is 0.98 ohms. zs at switch fuse is 0.97 ohms. the 50mm 4 core run is approx 25meters to substation. am i right in thinking there is something seriously wrong here? i no i havnt seen whats at the substation end yet but im thinking we have a big problem if the zs at db is so high and the switch fuse contains fuses with a max zs of 0.42. please someone tell me im not going mad and missing something.
very high ze/zs
- Thread starter sparkyt
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TT Installation?
AndyGuinness
AndyGuinness
like i say cant acsess supply origin at the moment but there are no rods and rcds present at any point we have inspected so far. estate owner wants to get his own spark in as i have flagged up a problem but just want to make sure im not barking up the wrong tree first. being so close to the sub station should we really have readings so high?
Nope, would suggest full access to substations then get on the phone to the DNO if something is amiss.
AndyGuinness
AndyGuinness
If they are SWA cables you need to check the tightness of the glands specially in the sub station . Some sparks of late , don't seem to be able to get their glands tight.
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Not likely to be TT that low especially on industrial estate could be corrosion problem somewhere.
