On Friday, November 11, 2011 05:18:26 PM Peter Blodow did opine: > Hello Karl, > > the general installation for small houses, like one family buildings or > small shops, if made new or repaired, is a 3 phase four lead underground > cable, fused with 50 A where it enters the building, coming up from the > ground at the edge of the houses wall. In our case, rather typical I > think, it's a four times 70 sq. mm alu cable with double PVC insulation. > From the main fuses, a four times 25 sq. mm copper cable continues to > the current counter. After that, current is fused with three 35 A fuses. > Then things split up into three copper strips for the single phase > circuits. Each circuit, going to the rooms, is equipped with a 16 A > breaker. The tripping characteristics are from very fast (magnetic > breaker) for the living rooms, medium for the kitchen and lag for my > machinery (mainly thermal breaker). For the welding shop and the outdoor > circuits I use 25 A slow blow wire fuses. In our house, being rather > large, I have installed 6 sub-distribution cabinets in order to keep the > single phase wires and cables at reasonable length. > > The neutral lead of the incoming ground cable is grounded at the village > transformer station together with the center of the secondary windings > of the trafo. It's primary is connected in delta so there is no > grounding on the high voltage side. Inside the house, lead #4 is > connected by a 16 sq. mm copper to the main water pipe, but since the > incoming public water supply is now a plastic pipe I doubt that there is > much use... > You need to fix that Peter. I'd take it back to the entrance, drive 2 ground rods adjacent to the foundation that are 2 meters apart, and tie the neutral to both with the same size wire they used for the water pipe connection that is no longer there. Run separate wires to each rod so that it is y'd to each rod at the neutral wire. That will stop 90% of a local lightning strike.
> After the current measuring device, the neutral is split up into the > neutral lead system going to the single phase circuits and the > protective ground system, both going throughout the house. This > separation must happen as soon the leads become smaller than 10 sq. mm > copper, i.e., right before the separation of the single phase circuits. > With heavier wires, they may serve both purposes in one. > > The transformers at the station are three phase transformers, three > coils on a three leg iron core. There is only one trafo necessary for > one supply line, e.g., one street. This is all a very simple and > straightforward system. At the trafo station there is also a circuit > breaker to interrupt all phases in case one of them fails, in order to > avoid unsymmetrical supply with a danger of burning up three phase > motors. A three leg trafo costs about 30% or so more than a single phase > trafo, but can carry 70% more energy, which is the reason for this > system. > > Even In little houses and small apartments, all apartments will have a > three phase supply because the electric kitchen stoves, usually being > the largest consumer, are connected three phase in order to distribute > power to the lines, hereby avoiding unsymmetries. These tend to be > cancelled out by statistic distribution, looking over a large number of > houses. > > This system is, of course, not so true for old buildings, but after WW > II there weren't so many buildings left around in Germany, so we had the > "chance" of new technologies with new installations. When we had bought > our house in the seventies, I found remainders of the old installation > in the attic: 6 A at 220V AC, single phase. That made it 1300 Watts at > maximum, and now I have almost 100 kW available... Compared to my 50.8kw with that 200 amp 254 volt balanced single phase feed, that rather nice. > Peter Blodow > > Karl Schmidt schrieb: > > On 11/11/2011 03:25 AM, Peter Blodow wrote: > >> Brian, > >> Here in Germany, all electrical supply, home and industry, is done > >> with three phase current plus neutral. For single phase use, like > >> for apartments, the three phases are split up and each apartment or > >> room gets one hot leg plus neutral (plus protective earth). > > > > Interesting - you are saying that "all" homes in Germany have 3phase > > power? That would mean 3 transformers instead of one - an expensive > > way to go for the utility company. There is some savings in > > distribution losses with 3 phase - and in the USA some homes are now > > getting 3 phase for air-conditioning and a lower rate. > > > > The thing that changes this is now inverters have dropped greatly in > > cost. There is little reason to pay for a 3-phase service install for > > a one man shop. (Newer Air-conditioners may have an inverter to > > increase efficiency ) > > > > The error of using safety-ground as a neutral is a common error (the > > most common?) - once current is flowing over the conductor, there is > > always a voltage drop and then a ground potential is no longer a > > ground potential. The rule is: Never use safety-ground as a neutral > > and never use a neutral as a safety-ground. Safety grounds should > > never have current flowing unless there is something faulty. > > > > The number of power connectors around the world is staggering. > > historically, most countries set up their own standard so some local > > company would have a cartel to produce the plugs and sockets. Some > > of the connectors are close enough in size that they will plug into > > other standards creating dangerous situations. > > > > It is also important to note that color codes for power circuits > > varies by county; sometimes in dangerous ways! I have a bit of this > > written up at: > > > > http://wiki.xtronics.com/index.php/Wire-Gauge_Ampacity#Why_was_.27hot. > > 27_Black_in_House_Wiring.3F > > > > There is a second article related to grounding here: > > > > http://wiki.xtronics.com/index.php/Lightning_Failures_in_Transducers > > > > > > ---------------------------------------------------------------------- > > ---------- Karl Schmidt EMail > > k...@xtronics.com Transtronics, Inc. WEB > > http://xtronics.com 3209 West 9th Street > > Ph (785) 841-3089 Lawrence, KS 66049 FAX > > (785) 841-0434 > > > > When angry, count to four; when very angry, swear. -- Mark Twain > > > > ---------------------------------------------------------------------- > > ---------- > > > > ---------------------------------------------------------------------- > > -------- RSA(R) Conference 2012 > > Save $700 by Nov 18 > > Register now > > http://p.sf.net/sfu/rsa-sfdev2dev1 > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------ > ------ RSA(R) Conference 2012 > Save $700 by Nov 18 > Register now > http://p.sf.net/sfu/rsa-sfdev2dev1 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> If you learn one useless thing every day, in a single year you'll learn 365 useless things. ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
