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Forum Index : Off topic archive. : Single HT elec. line in SA-works?
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| domwild Guru  Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Hi, Driving across the Nullabor I noticed single wire high-tension farm supplies instead of the two-wire single-phase ones I am used to from the bush and I have also seen single telephone wires running north from Gascoyne Junction in WA to the sheep stations. This telephone system seems to work unless there is a thunderstorm nearby, which also cuts the wire occasionally. IMHO there must be a lot of resistance if the earth is the second conductor or isn't there? What happens at the farm for the electricity supply? Does each farm have a gigantic ball of copper as the earth and missing neutral but such a mass of copper may as well be strung up as a second wire anyway? Confusion always reigns supreme in my mind! Help! Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Barry T Coles Senior Member  Joined: 30/07/2009 Location: AustraliaPosts: 109 |
Hi Dom I'm not the full bottle on this but I know that it's what electricians refer to as Neutral to earth return. My understanding is that power is sent along the single wire to a residence & then any appliance that is being used & then is returned to the grid through an earth spike driven deep into the ground and then by way of an earth connection back at a pole where the single wire started thereby completing the circuit. It was done I believe back in the days when copper wire was the go and as a cost saver. Cheers Barry I need to learn from the mistakes of others. I dont have the time to make them all myself. |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Dom The system is called a SWER system it works on high voltage very low amps to reduce resistive losses in the neutral line something like 33,ooo volt with a transformer at each house to bring it to 240 volts. All the best Bob Foolin Around |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Thats interesting. I would imagine the earth stake would have to be good and deep. Being AC, I dont think there would be any corrosion problems. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi glenn They normally bury about 50 meters of cable as deep as they can in the ground at the transformer for the neutral earth and have a conductive liquid the pour in the trenches, maybe salt but not sure on that, they have a conductance meter, something like a megger that they test the earth return with from a stake driven in the ground well away from the array. If the reading is to high they put in more cable. We where on this system for a while, and during the wet weather the power was noticeably better. The cable is aluminium stranded cable with a high tensile galvanized steel core very strong as some spans are over a Kilometer. It is single phase naturally and from memory limited to 10 KW on the transformer. We had a 5 hp single phase 440 volt motor in the dairy and it grunted a bit starting in dry weather. All the best Bob Foolin Around |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Thanks. I am no longer confused! What sort of a max. distance for the single wire from the powerstation or substation are we talking about? Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Dom The one we where on was around 15 Klm and I have seen some longer than that so I do not know what the max distance would be. I asked a friend of mine who was a lines man and he said the longest one he put in was 90 Klm but he wasn't sure if it had a booster or not as they just put up the line. All the best Bob Foolin Around |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
I suppose it would be a good idea to bury the earth return line under the septic waste water pit. Keep it moist. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Yes, The conductive stuff they pour into the trench is called "Bentonite" mixed with water . It keeps the soil sort of moist and lowers the resistance of the earth around the conductor . They use it in s.w.e.r lines and around the earthing straps for microwave and tv towers , Radio station transmitter earthing Mats . these earthing mats are copper wires radiating from the base of the radio tower Bruce Bushboy |
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