Chris Pearson:lyledunn:
You are correct Alan, the last house is next door at the end of line about 150m away from the house in question. On the line running left on my sketch the first section is overhead to a pole where it feeds another TT property. At the same pole the cable goes below ground and feeds 3 more domestic properties on a run of about 500m to the last.How many of the three further properties are TN-C-S? Is it likely that after at least 650 m, Ze could be < 0.35Ω?
Very good point Chris, but I cannot answer that. The lengths I gave were all estimates based on how far I can hit a golf ball!. I had to get into my van and drive to the farm from the house. The overhead from the transformer near the farm went as the crow flies to the first property then went underground and along the road before being teed off to the house in question. I know where the tee is on the side of the road because the first DNO crew dug it up a week earlier as they suspected a neutral failure at that point. The front lawn is at least a 60m pitch shot with a good whack with my hybrid and perhaps another pitch to get back to the transformer, so maybe 300m . What I can tell you is that when the fault was fixed Ze at the house was 0.28 ohms with P to N displaying the same. Relatively small transformer so I guess the conductors must have been at least 50mm2. The last house looked further away than it actually is on Google maps so maybe they are just on the threshold. By the way, the incoming water service is MDPE with copper thereafter. And dont go doing resistivity and impedance sums as my golf shots often fly well over the green!
Chris Pearson:lyledunn:
You are correct Alan, the last house is next door at the end of line about 150m away from the house in question. On the line running left on my sketch the first section is overhead to a pole where it feeds another TT property. At the same pole the cable goes below ground and feeds 3 more domestic properties on a run of about 500m to the last.How many of the three further properties are TN-C-S? Is it likely that after at least 650 m, Ze could be < 0.35Ω?
Very good point Chris, but I cannot answer that. The lengths I gave were all estimates based on how far I can hit a golf ball!. I had to get into my van and drive to the farm from the house. The overhead from the transformer near the farm went as the crow flies to the first property then went underground and along the road before being teed off to the house in question. I know where the tee is on the side of the road because the first DNO crew dug it up a week earlier as they suspected a neutral failure at that point. The front lawn is at least a 60m pitch shot with a good whack with my hybrid and perhaps another pitch to get back to the transformer, so maybe 300m . What I can tell you is that when the fault was fixed Ze at the house was 0.28 ohms with P to N displaying the same. Relatively small transformer so I guess the conductors must have been at least 50mm2. The last house looked further away than it actually is on Google maps so maybe they are just on the threshold. By the way, the incoming water service is MDPE with copper thereafter. And dont go doing resistivity and impedance sums as my golf shots often fly well over the green!
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