Generator earthing

All the Genuine TNS farm systems I have seen had a transformer next to the load, usually large for grain drying (150-300 kVA), and an 11kV supply. You cannot assume anything else is TN-S particularly nowadays when random changes seem to be made! And whilst I agree with Graham for any cabled installation, it is not a problem with the local TX and an incorporated Earth mat, which meets the within your control specification. I think you may be right John about the generator Earth bars going into the rock, It is very difficult to get a 1 micro-Ohm Earth resistance although the water source might be good too, as a HV fault in the power station could be very dangerous! If you only have a small generator and no livestock an Earth rod and RCD is probably adequate, but I have had a lot of experience with bigger ones and I much prefer an Electronic MCCB as protection. Certainly bonding every bit of ground connected metalwork would be a good idea, to get a low Ze value.

551.4.3.2 says a system for distribution of Electricity which does not apply to a private transformer.

IF this is not a private transformer job, and the supply is from somewhere else then, of course, you will need some form of Earthing for the generator supply but this probably will be low enough resistance from the bonding Mike and  I mentioned above, add another rod if you like it does no harm, but the supply is not safely TN-S.

There is another point and that is the position of the generator N-E bond. The generator will be insulated from the Earth if on the linkage (normal), and failure of the Earth cable core quite possible, and will not be noticed. The safest place for the bond is therefore somewhere fixed in the switchgear to ensure ADS will still operate correctly. Again this is not a problem if the generator is fixed down to a base and a long  PTO shaft connected to the tractor.

All the Genuine TNS farm systems I have seen had a transformer next to the load, usually large for grain drying (150-300 kVA), and an 11kV supply. You cannot assume anything else is TN-S particularly nowadays when random changes seem to be made! And whilst I agree with Graham for any cabled installation, it is not a problem with the local TX and an incorporated Earth mat, which meets the within your control specification. I think you may be right John about the generator Earth bars going into the rock, It is very difficult to get a 1 micro-Ohm Earth resistance although the water source might be good too, as a HV fault in the power station could be very dangerous! If you only have a small generator and no livestock an Earth rod and RCD is probably adequate, but I have had a lot of experience with bigger ones and I much prefer an Electronic MCCB as protection. Certainly bonding every bit of ground connected metalwork would be a good idea, to get a low Ze value.

551.4.3.2 says a system for distribution of Electricity which does not apply to a private transformer.

IF this is not a private transformer job, and the supply is from somewhere else then, of course, you will need some form of Earthing for the generator supply but this probably will be low enough resistance from the bonding Mike and  I mentioned above, add another rod if you like it does no harm, but the supply is not safely TN-S.

There is another point and that is the position of the generator N-E bond. The generator will be insulated from the Earth if on the linkage (normal), and failure of the Earth cable core quite possible, and will not be noticed. The safest place for the bond is therefore somewhere fixed in the switchgear to ensure ADS will still operate correctly. Again this is not a problem if the generator is fixed down to a base and a long  PTO shaft connected to the tractor.