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skyline2500cc
Hello Gents
Once again I’m looking for your expertise to resolve the following application.
A local supply Authority has supplied a single phase 8Kw TN-C-S supply via a cut out, to which we have to terminate a 35mm2 3 core SWA cable to be buried underground. The cable cannot be easily terminated and because we need to provide short circuit protection I was considering installing a 100-200 amp fused disconnector which would enable us to use crimped lugs to make the termination. I would then look to terminate the earth /neutral and phase and use the SWA gland frying pan to earth the SWA.
Question:
Does anyone have any ideas of the best way to do this other that what I am considering.
At the end of the 35mm2 cable we have to feed two sub circuits one is for a consumer unit for lighting and power max load < 3Kw and the other is via a 50mm2 cable to another consumer unit max load <5Kw.
Question
1. The consumer unit will be about 500mm away from the terminated end of the 35mm2 cable, do I need to provide short circuit protection for such a short run.
2. The second sub circuit will be 400 meters long using a 2 core SWA XLPE cable and will use the SWA as the CPC. I have the same problem as before. If we keep the consumer tails short enough do we need to provide short circuit protection and if so what’s the best way of doing this.
3. Finally we are looking to check the earth loop impedance of the sub circuit by way of calculation which is as follows
1. Cable 1 from origin of supply 3 core 35mm2 XLPE buried underground 200 meters long. Short circuit protection by way of BS 88-3 fuse. Measured Ze value 0.35 Ohms max load <3Kw
2. Cable 2 from the end of the 35mm2 cable will have a BS88-3 fuse and will use the SWA as the CPC. The CSA of a 50mm2 2 core cable is 74mm2 as detailed in table 54.7 max load < 5Kw
As Zs =Ze +R1 +R2 how do I go about checking by way of calculation what the Earth loop impedance is from the point of origin to the furthest consumer unit when I have two different size cables with one using a 3[SUP]rd[/SUP] core as the CPC and the other the SWA
It will probably become obvious when someone points it out
Cheers
Skyline 2500cc
Once again I’m looking for your expertise to resolve the following application.
A local supply Authority has supplied a single phase 8Kw TN-C-S supply via a cut out, to which we have to terminate a 35mm2 3 core SWA cable to be buried underground. The cable cannot be easily terminated and because we need to provide short circuit protection I was considering installing a 100-200 amp fused disconnector which would enable us to use crimped lugs to make the termination. I would then look to terminate the earth /neutral and phase and use the SWA gland frying pan to earth the SWA.
Question:
Does anyone have any ideas of the best way to do this other that what I am considering.
At the end of the 35mm2 cable we have to feed two sub circuits one is for a consumer unit for lighting and power max load < 3Kw and the other is via a 50mm2 cable to another consumer unit max load <5Kw.
Question
1. The consumer unit will be about 500mm away from the terminated end of the 35mm2 cable, do I need to provide short circuit protection for such a short run.
2. The second sub circuit will be 400 meters long using a 2 core SWA XLPE cable and will use the SWA as the CPC. I have the same problem as before. If we keep the consumer tails short enough do we need to provide short circuit protection and if so what’s the best way of doing this.
3. Finally we are looking to check the earth loop impedance of the sub circuit by way of calculation which is as follows
1. Cable 1 from origin of supply 3 core 35mm2 XLPE buried underground 200 meters long. Short circuit protection by way of BS 88-3 fuse. Measured Ze value 0.35 Ohms max load <3Kw
2. Cable 2 from the end of the 35mm2 cable will have a BS88-3 fuse and will use the SWA as the CPC. The CSA of a 50mm2 2 core cable is 74mm2 as detailed in table 54.7 max load < 5Kw
As Zs =Ze +R1 +R2 how do I go about checking by way of calculation what the Earth loop impedance is from the point of origin to the furthest consumer unit when I have two different size cables with one using a 3[SUP]rd[/SUP] core as the CPC and the other the SWA
It will probably become obvious when someone points it out
Cheers
Skyline 2500cc
