ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Norwegian power?

This are definitely interesting, and it was detected currents in the ground in Oslo when the subway in Stockholm in 1950 was started. (417 kilometers away and supplied with 750V DC)

Still this are considered as a non existing problem.

I'm a educated as a mechanical engineer, but have dealt pretty much with electro...

When we consider our traditions with IT systems, these problems are not of importance .... ????

I see lots of equal sides to your 277/480V systems, and your 208 delta's

I don't think TN-S is systematically used in any country of the world these days since it simply isn't cost-effective. It's either TT (at the cost of high loop impedance) or TN-C (at the cost of stray current issues).

Berlin sort of had TN-S for a while because some areas were supplied with 127/220 V and the PEN was only used as an earth conductor since there were no 127 V loads.

Most places had single-phase meters only and 220 V loads were connected across the two lives. However, only one of the lives was measured, so thrifty people connected one wire of a socket to the central heating pipes or cold water plumbing, thus creating their own neutral, and plugged in stuff set to 127 V. Voila, free power if connected to the right leg of the supply! Illegal and unsafe of course, but there are always some morons, no matter where you go.

In the states everything under the NEC is TN-S (its mandatory) but when you get to utilities TN-C is used because of capitol economy.

......favoured isolated rooms in homes (in a room without earth potential even touching a live wire can't create a dangerous current flow). Isolated room systems typically use 2-pin outlets and class 0 or class 2 equipment. Class 1 is safe as well as class 1 without earth connection is just class 0.

These days it's nearly impossible to create a room without earth potential with metal air ducts, central heating pipes in case of hot water heat, antenna wire shields, network cable shields etc. etc.

Well not quite, up to the main panel it's technically TN-C so the whole system is TN-C-S. And until recently range and dryer circuits were entirely TN-C if I'm not mistaken.

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Correct, but only because that section is fed by pocos which is governed by the NESC. But if the transformer was customer owned the service would fall under separately derived requiring TN-S. Up until 1996 ranges and dryers could ground through the neutral but its no longer done. Other than that (and technically overhead line work/systems over 600volts) TN-C is forbidden.





[quote]I think Sweden historically had a mix of TT and TN-C but generally favoured isolated rooms in homes (in a room without earth potential even touching a live wire can't create a dangerous current flow). Isolated room systems typically use 2-pin outlets and class 0 or class 2 equipment. Class 1 is safe as well as class 1 without earth connection is just class 0.

These days it's nearly impossible to create a room without earth potential with metal air ducts, central heating pipes in case of hot water heat, antenna wire shields, network cable shields etc. etc.

This way of thinking was the rule her in Norway too, even with pretty good grounding trough steel tubes for central heating, grounded coax on the antenna systems etc. The rule was no grounding needed if it was at least 2 m (=yd) from a grounded surface to the outlet.

By experience I may tell touching a single live wire standing on a surface of a PVC floor are at least unpleasant :-)

But even older American buildings has 2 pin outlets.