In all honesty I'd like developed countries to move away from TT supplies. TT, TN-C-S and PME are simply a choice between cons in a world where DNOs do not want to provide more conductors than it takes to get the lights on. TN-S provides all the advantages of superior fault clearing given by TN-C-S, but without parallel earth currents or the risk of exposed parts becoming live should the neutral be lost. 

The U.K. will not and can not change back to TN-S systems. It will be too complicated and costly. TN-C-S has its own issues.


I was recently at an outlying cottage in the countryside  and was confirming the type of earthing provided. An occupier, an ex electrician, said that the supply was TT as the incoming supply cables had too high an earth fault  loop impedance for a P.M.E. earthing system.  We normally require a figure of about 0.35 Ohms for P.M.E. earthing. So, in this case the earhing was TT.


Also attached to the cottage was a stable block for horses, and TT earthing is very desirable where valuable four footed animals are concerned.


Z.

 

In all honesty I'd like developed countries to move away from TT supplies. TT, TN-C-S and PME are simply a choice between cons in a world where DNOs do not want to provide more conductors than it takes to get the lights on. TN-S provides all the advantages of superior fault clearing given by TN-C-S, but without parallel earth currents or the risk of exposed parts becoming live should the neutral be lost. 

The U.K. will not and can not change back to TN-S systems. It will be too complicated and costly. TN-C-S has its own issues.


I was recently at an outlying cottage in the countryside  and was confirming the type of earthing provided. An occupier, an ex electrician, said that the supply was TT as the incoming supply cables had too high an earth fault  loop impedance for a P.M.E. earthing system.  We normally require a figure of about 0.35 Ohms for P.M.E. earthing. So, in this case the earhing was TT.


Also attached to the cottage was a stable block for horses, and TT earthing is very desirable where valuable four footed animals are concerned.


Z.