Im really curios about this, on another forum the main voltages, grounding and bonding were brought up on how they differe across countries. I found out that the IT system with a Delta secondary was the norm in Norway for residential and commercial as apposed to TT and the widly adopted TN-C-S earthing found through out North America and Europe.
Any body know how this system was applied there?
Does anybody have any pictures of residential breaker panels/consumer units in Norway useing IT grounding?
Pretty like 2 phase from your delta 208V except for grounding at transformer.
Fuse or (later 2 pole breaker) on both live live lines to a single phase outlet.
Local grounding similar to NEC. No bonding to N, (no N existing)
It has been used some different arguments to use this system. Most common: A) 3 phase available with 3 wires only. B) safer, because its harmless until fail on the 2'nd phase.
It is pretty common to have 3-phase here, I even have at my cabin. Good for the water pump :-)
Another difference from North American systems: Copper only up to 16 mm^2. Pretty common wit wires on the wall here: (pictures after e lightning accident)
dsk
PS Ground connections connected at copper clamps under plastic cower in top of cabinet. (pic) DS
So essentially the local transformer secondaries are delta-wired without any earth (ground) reference?
Isn't the probability of an earth fault somewhere in the distribution awfully high? Unless I'm seriously mistaken an earth fault in any house or apartment would cause that phase to assume earth potential throughout the wiring on this transformer. In this case, the first fault in any other house would cause a dangerous potential difference.
In order to avoid such unpredictable situations most other countries opted for TN or TT
It will not be used in a new area, but are maintained where it is established. The supply to the house whre the pictures are from are changed to TT when the transformer was changed to supply 20 new buildings, they have 400V TN-C-S, so my guess are just tapping off at 230V for the older buildings.
The IT system made it self to TT at first fault :-) At second fault, it might start a fire in the first fault location. When no fault the voltage was floating relative to ground, usually stabilized at approx 130V due to capacity to ground.
In Norway even TN-C-S systems have all pole circuit breakers, so even an overload in N will release the circuit. P (ground) and N are not connected in more than one location in each house.
Thanks for the insights! No one has been able to provide me with reliable information about Norwegian distribution systems before, so I appreciate your info very much!
BTW, welcome to the message board!
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The IT system made it self to TT at first fault :-)
TT using a corner-grounded delta transformer setup... does feel a bit odd!
Thanks for the insights! No one has been able to provide me with reliable information about Norwegian distribution systems before, so I appreciate your info very much!
BTW, welcome to the message board!
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The IT system made it self to TT at first fault :-)
TT using a corner-grounded delta transformer setup... does feel a bit odd!
Thank you, I just saw your question when googeling for something about payphones. The self grounding TT description are right. It would probably been better with permanent corner grounding.
I will probably not be regular reader, but just pm me if you have questions about Norwegian oddities
I have just made a controller for my American payphone (AE 120B) for use at home, collecting or returning money depending on answer or not.
It sounds like the 'missing' pay [hones here went to Norway.
The proliferation of cell phones has made the 'pay phone' an item that is really hard to find here. And, when you do find one, the odds are it does not work!
A small modification; Taped a piece of thick paper to allow slightly ticker coins. Now it accepts NOK 10 and NOK 1. Ease to adjust back, just remove tape and paper. Building the coin controller was the most difficult part, Norwegian payphones did work different.
In Austria the major (former monopoly) phone company is still legally required to provide a dense network of payphones for emergency use. Occasionally I still see them being used for regular calls but not all that often. Some have even been upgraded to web access stations. Card phones have become rather uncommon I think, I haven't owned a card myself for more than 10 years.
The cards are still available as far as I know and there's a very odd anomaly. Originally the cards cost 50, 100 and 200 Schillings and contained a corresponding number of credit units. When the Euro was introduced in 2002, the system was never changed, only one unit is now 7.2 cents instead of 1 S. I never knew that until I found a card with a few units left in 2004 and the phone still showed what I considered Schilling credit.
We dont have many payphones left, But I did get my fingers int this, typical of the 90ies here. Pretty ugly, and this one are the most dirty I ever have seen. dsk
Is that really from the 90s? Dial pay phones were pretty much extinct by the early 90s in Austria. The only ones I've ever seen were semi-private ones at a public indoor pool. I think they survived until the introduction of the Euro. I really liked them because they had a cool vintage look about them. They even had red 7-digit displays for credit.
They were phased out when we got new coins in 1994. Then push button came. We were pretty late with non rotary. The last monopoly telephone was released in 1982, and was our first non rotary.
They were phased out when we got new coins in 1994. Then push button came. We were pretty late with non rotary. The last monopoly telephone was released in 1982, and was our first non rotary.
dsk
We weren't thst far ahead (first push-button phone introduced in 1980 but still pulse dial) but pay phones were upgraded fairly quickly.
In American telephony the term "rotary" refers exclusively to multi-line phones now only seen in period film and TV.
They are marked by having multiple push buttons towards the front which must be selected (pushed down) to complete a connection.
The term "rotary" is linked to the fact that the INTERIOR switching for these phones used "ROTARY WIPERS" as the switching mechanism. (Later some used linear wipers which are vaguely related to the cheapo keyboards used by PCs even now. The critical circuits are printed on thin plastics/ dielectrics and the contact wipes across these thin films to make the connections.)
{ For cyber-security buffs, the Japanese PURPLE code machines were built up around rotary wipers. When the Americans attempted to replicate their scheme they ended up with a PURPLE machine that worked even faster than the Japanese original. }
What you're describing would be termed as "dial telephone" -- leading to terms such as "dial tone."
(This followed an older scheme wherein you didn't dial at all -- you rang the operator (PBX -- public exchange) and told her who you wanted to reach. She then worked her plug board to make the connection. (Yes, she had a dial, herself)
This scheme was made funny and famous by Lilly Tomlin on Laugh-In. With it, Lilly could listen in on every conversation at will -- the ultimate gossip.
The rotary switch constituted a mini version of a PBX -- with some able to handle 64 lines. (IIRC) This type can be seen in "The Apartment" (1961) on the desk of the big bosses's secretary. Like Tomlin, she ends up knowing everything that's going on in the big corporation -- for the exact same reason.
True rotary phones were rented at a premium, (Impossible to buy.) typically at commercial rates for two+ lines. (You'd get a Yellow pages minimal citation to go with your commercial lines, too. Space ads cost a bundle extra.)
If you were a private party and wanted two lines the phone company would merely provide an extra vanilla handset. You would not get the push-buttons, etc.
Rotarys took off because they permitted "call stacking" -- if line one was busy, the system would automatically shift a new caller to line two, and so on.
Not surprisingly, most businesses felt compelled to get at least two lines and a rotary set of phones to match.
By todays standards, those old phone rates were sky high.
Thank you for this explanation. You are right in hence of my reference was to a rotary dial telephone. The rest was all new for me, and yes it differs great from what I believed was right. My mothers thounge are Norwegian so please forgive language problems.
Basically its just a surge arrester with a fuse. If a surge occurs such as a primary going into the secondary, the arrestor shorts the transformer neutral to ground by blowing the internal fuse. Under normal conditions it remains isolated from ground. 230 volts is present between phases and no neutral exists for loads like in a 230/400Y network.
The main difference are the tradition of systems with NO NEUTRAL This has implemented fuses in all wires, and when breaker became the rule, they are now sensing, and breaking all wires simultaneously, even neutral where those are. It is more and more focus on covers, and it shall not be possible to touch any wires or terminals without removing a cover (This makes even measuring a little more heavy, and you may often find missing covers to be replaced later by "lazy" workers".
You are not allowed to rewire your own home here, its extremely limited what you may do legally in your own house. It is common to have a main switch or breaker in all cabinets, something I have been missing in US homes.
Another difference may be the extremely long distances from the transformer to the consumer. On the countryside it may be several 1000 meters (~yds). This may cause considerable voltage drops, and instant water heaters are "unofficially banned".
The main difference are the tradition of systems with NO NEUTRAL This has implemented fuses in all wires, and when breaker became the rule, they are now sensing, and breaking all wires simultaneously, even neutral where those are. It is more and more focus on covers, and it shall not be possible to touch any wires or terminals without removing a cover (This makes even measuring a little more heavy, and you may often find missing covers to be replaced later by "lazy" workers".
You are not allowed to rewire your own home here, its extremely limited what you may do legally in your own house. It is common to have a main switch or breaker in all cabinets, something I have been missing in US homes.
Another difference may be the extremely long distances from the transformer to the consumer. On the countryside it may be several 1000 meters (~yds). This may cause considerable voltage drops, and instant water heaters are "unofficially banned".
dsk
Do they have a home supply center in Norway? What happens if someone re-wires their home without permission? I guess Im just really curios.
In America people can go to a 'Home Depot' or 'Lowes' and buy everything they need to rewire a home: electrical panel, wire, boxes, outlets, meter sockets, ect no questions asked. Sometimes in some areas a person should pull a permit and let the town know that is happening, but, being honest that usually doesn't happen. In America the average home owner can re-wire his entire home and not be punished.
In US home you are required to have a main disconnect either outside or the panel right after the meter. But sub panels are not required to have this disconnect. However, a detached structure from the home like a shed or garage must have a main disconnect or less than 6 breakers to turn off all the power to the structure.
How much is the average voltage drop? Does 230 volts drop to 210 volts? Also why the ban on instant water heaters?
One more question: In Norway, do all IT systems not interconnect the grounding systems of different structures? In that only 2 or 3 hots, no ground to a home?
In systems where ground/ earth wires (jord cable) do not interconnect all structures that can be a major fire risk?
(In one home phase "A" may ground to the case of a fridge. Ok, just a TT system now. But if phase "B" grounds in a home two from the same transformer in the electric heater and the grounding system of the 2 homes is not interconnected home one and home two will have ground grids of opposite potential. The 230 volt potential will make power flow across the earth creating voltage gradients and heating up the grounding system drying out the soil)
Some of the pictures look fairly familiar to the continental European eye, except for the IT-specific bits.
Do you have any idea why in one picture some of the fuses are yellow instead of white? I've never seen that before!
The large number of RCBOs (GFI breakers) is also unusual, in most parts of Europe they're still ridiculously expensive!
For the fuse color I have no idea. It is strange. Perhaps a main or higher amperage fuse?
My understanding is that in Norway GFCI/RCD breakers are mandatory. From all the Norwegian panels I have seen on the net most if not all the circuit breakers are RCD/GFCI type. Its interesting, because through out the rest of Europe its normal to have a 'main type RCD breaker' where one 63 or 100 ampere RCD breaker feeds about 10 regular breakers thus protecting many circuits. Its cheaper, but one ground fault shuts down more than one circuit.
It is no demand, but convinient to have many gfci's. The color codes were: RED: hig voltage as neon signs etc. Yellow: central heating, oil burning boilers etc. Green: computers or other equipment needing controlled shut down. Not sure if this really was in a code, or just commonly used. dsk
It is no demand, but convinient to have many gfci's. The color codes were: RED: hig voltage as neon signs etc. Yellow: central heating, oil burning boilers etc. Green: computers or other equipment needing controlled shut down. Not sure if this really was in a code, or just commonly used. dsk
But the circuits must at least be GFCI protected?
Having many is a good idea. Ground fault only turn off one circuit.
Many countries require the use of at least two RCDs these days. In Germany that seems to have caught on but in Austria not quite, the only home box with more than one RCD I've ever seen was mine. And I only did that because it was a really fancy place. The new kitchen alone got seven circuits for a 3-phase induction hob, electric oven, dishwasher, microwave, combi boiler, lights and sockets. Originally (1960) there were only two, lights and sockets. And that was fancy, usually lights and sockets weren't on separate circuits back then.
In a larger place I'd absolutely do one RCD per floor so no one has to stumble down stairs in the dark. Even that's a bit unusual though.
RCBOs are still painfully expensive. I think a 2-pole RCD is around 30 Euros, an MCB around 10 and an RCBO is 70 Euros. I only bought some recently because they were 60% off. Hardly comparable to the UK where you can get an RCBO for 10 to 20 quid off eBay! Sometimes actually the same brand that costs more than twice as much here...
Many countries require the use of at least two RCDs these days. In Germany that seems to have caught on but in Austria not quite, the only home box with more than one RCD I've ever seen was mine. And I only did that because it was a really fancy place. The new kitchen alone got seven circuits for a 3-phase induction hob, electric oven, dishwasher, microwave, combi boiler, lights and sockets. Originally (1960) there were only two, lights and sockets. And that was fancy, usually lights and sockets weren't on separate circuits back then.
In a larger place I'd absolutely do one RCD per floor so no one has to stumble down stairs in the dark. Even that's a bit unusual though.
RCBOs are still painfully expensive. I think a 2-pole RCD is around 30 Euros, an MCB around 10 and an RCBO is 70 Euros. I only bought some recently because they were 60% off. Hardly comparable to the UK where you can get an RCBO for 10 to 20 quid off eBay! Sometimes actually the same brand that costs more than twice as much here...
What does RCBO and MCB stand for? Im none to familiar.
RCD _ residual current device, essentially a GFI but usually entirely electro-mechanical rather than electronic. Trip currents range from 10 mA to 3 A for ancient models, currently up to 500 mA I think. For all outlet circuits 30 mA are required in most countries these days, requirements for lighting circuits and fixed appliances vary. Earthing arrangements play a role as well, in a TN-C-S system similar to US practices it is sometimes allowed to have circuits without RCDs, in a TT system (only a local earth rod, no connection to the neutral) RCDs are usually necessary for all circuits as the fault current will not be high enough for a fuse or MCB.
MCB = miniature circuit breaker, plain old breaker in US terms.
Edit: RCBO = combined RCD and MCB, i.e. GFI breaker.
I have a rotary dial phone in my pool bar and a rotary dial wall phone in the garage There is not really much special in the pay phone itself. They get installed on a special "ground start" line from the CO. If you install one on a regular line, they work normally. The "ground start" requires that you momentarily ground one line to get dial tone. When I was a lifeguard they made the mistake of putting the terminal block for the pay phone in the guard room. We had a regular phone hooked up and we shorted it out with our whistle. This is done by the coin acceptor in the pay phone, usually grounding through the coin itself on the old ones like this one. The other trick on a pay phone was to "pin" a call. You stuck a pin or needle through the cord or into the mike hole and shorted it to the phone base. That is why the newer cords are armored and they put in a pin proof mouth piece mike. They glued the cap on.
Hi again, I feel guilt for messing up this post about Norwegian power. Yes I love much of this, and the 3 slot payphone looks great. Is it another place on ECN forums we could continue that part of this, and come back to the thread starters issue?
What may be important in this setup is. (PE protective earth) The cable from the transformer has a common N and PE (TNC) From the main panel, the N and the PE are splitted, so the rest of the building are TNS. The PE are bonded to pipes, and other metallic parts of the building where so are. N are never grounded after the main panel. N are deemed to be treated as a live wire, and all circuit breakers are multipole, and senses current in, and breakes N to. In this building all branches are protected with combined GFCI and breakers. All light switches breaks both live and renewal to bathrooms etc. We still use Schuko and they are unpolarized. The North American AFCI are not used at all here.
What may be important in this setup is. (PE protective earth) The cable from the transformer has a common N and PE (TNC) From the main panel, the N and the PE are splitted, so the rest of the building are TNS. The PE are bonded to pipes, and other metallic parts of the building where so are. N are never grounded after the main panel. N are deemed to be treated as a live wire, and all circuit breakers are multipole, and senses current in, and breakes N to. In this building all branches are protected with combined GFCI and breakers. All light switches breaks both live and renewal to bathrooms etc. We still use Schuko and they are unpolarized. The North American AFCI are not used at all here.
Great info.
TN-C should be avoided anywhere in the system for a variety of reasons. Yes it is commonly used in Europe and USA, but has downfalls. Some of the current flows through the earth producing elevated magnetic fields and step touch potentials (stray voltage)
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.
Historical it has been used many different systems. Halden had 40 Hz, Svalbard 25Hz, Rjukan had the 127/220V as you mention.
At home I have 230V 3 phase IT. When no errors in the network I measure 127V to ground. The 3 phase meter meters current in 2 legs.
At our cabin we have 3 phase 230V TT, I Guess this are tapped on the legs of a 400V transformer since the transformer was changed when some in the neighborhood built houses with 400V TN-C-S
The cabin are built on on solid rock, (in/on?? a little island of soil) In a dry summer its not good enough grounding to release the 30 milliamp GFCI when grounding a leg. I feel that's pretty safe. :-)
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
Perhaps not an apparent problem, but IMO a step back. 230 volt IT does not produce stray currents since all load current is carried on insulated conductors, but the system that replaces it with TN-C-S does. Backwards IMO for one of the most advanced countries on Earth.
Personally I would use TN 3x230+PE for home and light commercial networks while using TN-S 400Y/230+N+PE for large commercial/industrial.
Our 208 volt system are not delta rather 120/208Y. Our deltas are 240 volts but rare in new construction. Both our 277/480 and 120/208 is TN-C-S. TN-C is used everywhere by utility companies even in the high voltage side. Never liked it but that is how it is.
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.
If I am correct, doesn't Finland or Sweden use TN-S?
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.
I do not know much about Sweden and Finland, but they have "always" had 230/400V with N
Once in Sweden I had an expensive experience: We installed same single phase equipment, some PC's etc and suddenly we got a "smoke leakage" The 3 phase supply had a small fuse on the N conductor, so we got nearly 380V at the 230V single phase outlets! Usually they only have fuses/breakers in the live wires in Sweden.
I have no clue about the Swedish or Finnish codes.
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.
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.
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.
......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.
If we really should go historical, Oslo's first hydroelectric power plant opened 1900. 1.8 MW 46.6Hz 4 wire 2 phase (90deg). High voltage 5kV to a secondary plant for making 2*110V dc pictures: http://tinyurl.com/ohobbzt
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.
[quote]
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.
That is interesting, I never thought about it that way.
......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.
Yup, even until the early 60s some buildings did not have grounding outlets. Our ranges and ovens had none grounding outlets until 1996, but simply used the neutral to ground. A bad idea, but that is how it worked.
1)A 230/400 V system equal to UK systems. 2)A 230/230 V system where single phase loads are between 2 legs of the 230V 3 phase system. This may or may not have a grounded center of the Y (IT or TT) no Neutral wire at all.
As far as I know this was banned in the UK from 1948.
By experience I may tell touching a single live wire standing on a surface of a PVC floor are at least unpleasant :-)
If the PVC floor is fairly thin, and the sub floor even slightly conductive then capacitive coupling will ensure enough current to feel it. Also any surface film of condensation will make the floor a less than perfect insulator.
I can confirm that! Even wearing shoes with rubber soles and standing on a wooden floor a 230 V sgock is rather unpleasant! I got bit by a portable record player on a flea market, that's how I know. Of course the floor may have been a bit damp as this happened in a cellar but still, I had an inch of rubber or so between my feet and the floor!
Speaking of ungrounded outlets, a few months ago I got to tour an untouched 1910s apartment (now a museum) and in the bathroom there was an outlet right next to the sink!
Hi dsk with the 230 volt system presumably you get 230 phase to phase and 127 volts to earth/neutral is this right? On another topic I remember that when I'm upstairs standing on carpet which is on wooden boards I can touch live 240 volt terminal and feel nothing but if I accidently touch a wall I get a slight tingle.
You are right usually close to 127V to ground, but i may drop to 0 if its a fault somewhere, or raise to 230. Sometimes it is much higher voltages to, or peeks, but it is a sort of fusing in the transformer center who shorts to ground if to high voltage. (at least more than 230)
I know a student who did the trick mentioned over, because it was a fault somewhere outside his apartment, so he had 230 to ground. He just removed one fuse (the metered leg), and linked the ground to the disconnected wire. That way he could get 10 amps "free".
Regarding feeling the voltage. The caretaker at the old STK (=STC) in Oslo didn't like to climb the ladder so he always tried with his fingers if it was OK before he put in an an lamp. :-) (about 1970)
Hi dsk with the 230 volt system presumably you get 230 phase to phase and 127 volts to earth/neutral is this right?
More or less. Since you don't have a fixed reference to earth (or only a high-impedance connection) in an IT network the actual voltage will vary a bit.
BTW, it's 133 V these days, not 127 (127 is 220 V*sqrt(3) and 133=230*sqrt(3))
Thanks yes I knew 127 was for 220 phase to phase but I always struggle with the maths thanks for the info its been most helpful
No problem! I read about it so often that I've really learned those voltages by heart, that's why I notice such inconsistencies.
I think the big issue with maths is who becomes a teacher. Naturally people who hated maths because they had a hard time understanding it are quite unlikely to study it and become teachers. Unfortunately that means most teachers don't realise what it feels like to be "mathematically challenged" and what those who are need.
I tried studying electrical engineering for two painful semesters... worst time of my life! Few people have ever been as successful making me feel dumb as those maths geniuses! Later I switched to a more basic course (non-academic) and passed with flying colours. I can do maths when I need it and someone explains it to me in a way I understand but otherwise I'm lost.
I did not think about that difference, we still say 380 for 400, 220 for 230 etc here. In this discussion are this just of academic interest. If you tell people it is the phase voltage divided with the square root of 3, most people just say yes OK. (but get no interest)
If you draw a triangle of with sides of 230, put in a Y and measure to the center they may even understand it.
1)A 230/400 V system equal to UK systems. 2)A 230/230 V system where single phase loads are between 2 legs of the 230V 3 phase system. This may or may not have a grounded center of the Y (IT or TT) no Neutral wire at all.
As far as I know this was banned in the UK from 1948.
IMO 230 volts TN should be used in all domestic and light commercial, its much safer and no broken neutral to worry.
Ive always wondered, why was IT chosen over TN? Surely grounding the neutral would have been better?
Why IT? When I asked som 30 years ago, they claimed it to be safer. We should modernize a system from 1940 (IT) and the supplier would change the transformer at the same time, we offered to pay the extra cost to change to 400V TN-S or TN-C-S but they refused "of safety reasons".
Blessed are the meek, For they shall inherit the earth. !
Why IT? When I asked som 30 years ago, they claimed it to be safer. We should modernize a system from 1940 (IT) and the supplier would change the transformer at the same time, we offered to pay the extra cost to change to 400V TN-S or TN-C-S but they refused "of safety reasons".
Blessed are the meek, For they shall inherit the earth. !
What connection are the transformers? Are those boxes on the LV fuses?
Generally, the primary side (HV) will be Delta connected, the Secondary side (LV) will be Star connected. By the looks of things, the two black boxes on the left pole are triple pole LV fuse-switches, when you open them up, it cuts power to the load side of the fuses. The HV side is fused by DDO type expulsion fuses seen on that intermediate cross-arm as part of the vertical air-break switch.
Thanks! Id be very interested in the windings and data plate.
If you zoom on this picture: http://commons.wikimedia.org/wiki/File:Three-phase_distribution_transformator_IMG_8086_Hurum_Norway_23kV_240V.JPG
The data plate says Yyn0.
Which would come out as ungrounded wye primary with a wye secondary neutral brought out.
Now that I think about it, if the primary is wound wye, wouldn't it be so it can be solidly grounded? What would the IEC designation be for that?
I see what looks like a forth ground/neutral wire on the MV, so it would make sense then.
A primary grounded wye has the advantage of being resistant to ferroresonance, which Id imagine is more of a concern at 22kv and a long run.
Unless the primary is ungrounded wye? If ungrounded, than why wye and not delta? An ungrounded wye with a shorted secondary nullpunkt and one 230 volt phase faulted would make for some very interesting conditions.
Pretty quick answer, I will post the answer in Norwegian, and try try to translate in next reply. The information is limited by national safety reasons.
Trafoen fra bilde i masten er nok flyttet inn i den nye stasjonen. Koblingsanleggene i stasjonen er nye.
Trafoen er en 100kVA trafo fra Møre Transformatorfabrikk. Koblingsgruppe YYNN0 22kV/0.240V med manuell trinnreggulering med 2.5%. To trinn opp og to trinn ned. Tomgangstap 325W Belastningstap 1296W,ek=4.09% og er=1.3%. Det er IT nett på området. For helt nye lavspentnett bygger eidsiva TN-C nett fram til kunde. Denne trafoen har kun IT nett. Det brukes av og til treviklingstrafoer men for det meste setter vi to trafoer der det er behov for IT og TN-C. Det er da lettere å tilpasse merkeytelsen til behovet. Nettstasjonen tar da litt mere plass. På forumet ser jeg at noen har kommentert at det er expulsion fuse som er brukt på høyspentsiden. NB: Det er lite brukt og i vi bruker ikke den typen. Fra expulsion fuse kommer det ut varm gass og kan være en potensiell brannfare ved tørt terreng. (En slik sikring var årsaken til en stor skogbrann i Australia (jeg tror det var på begynnelsen av 80-tallet) hvor flere mennesker omkom. Det vanlige er å bruke enten backup fuse som fungerer sammen med en bryter via en slagstift som kommer ut av sikringen eller bruk av en fullrange fuse som ikke blåser ut varm gass.
Translation: The transformer in the mast are moved inside the new station. (main reason safety for the workers)
Rating 100 kVA double Y primary 22kV secondary 230V adjustable +/- 2 steps of 2.5 %. No load loss: 325W. Made by Møre Transformatorfabrikk. http://moretrafo.no/
The transformer supplies an existing IT network, New networks would have been TN-C to customer, (TN-CS from there) If dual voltages are needed they may use an extra set of windings, but prefer 2 transformers to keep the load more controlled. In that case the station will be slightly bigger.
They do not use high voltage expulsion fuse due to risk of fire in dry summers. They usually use a spring loaded fuse and switch, or a full-range fuse of a type not blowing out hot gases.
Pretty quick answer, I will post the answer in Norwegian, and try try to translate in next reply. The information is limited by national safety reasons.
Trafoen fra bilde i masten er nok flyttet inn i den nye stasjonen. Koblingsanleggene i stasjonen er nye.
Trafoen er en 100kVA trafo fra Møre Transformatorfabrikk. Koblingsgruppe YYNN0 22kV/0.240V med manuell trinnreggulering med 2.5%. To trinn opp og to trinn ned. Tomgangstap 325W Belastningstap 1296W,ek=4.09% og er=1.3%. Det er IT nett på området. For helt nye lavspentnett bygger eidsiva TN-C nett fram til kunde. Denne trafoen har kun IT nett. Det brukes av og til treviklingstrafoer men for det meste setter vi to trafoer der det er behov for IT og TN-C. Det er da lettere å tilpasse merkeytelsen til behovet. Nettstasjonen tar da litt mere plass. På forumet ser jeg at noen har kommentert at det er expulsion fuse som er brukt på høyspentsiden. NB: Det er lite brukt og i vi bruker ikke den typen. Fra expulsion fuse kommer det ut varm gass og kan være en potensiell brannfare ved tørt terreng. (En slik sikring var årsaken til en stor skogbrann i Australia (jeg tror det var på begynnelsen av 80-tallet) hvor flere mennesker omkom. Det vanlige er å bruke enten backup fuse som fungerer sammen med en bryter via en slagstift som kommer ut av sikringen eller bruk av en fullrange fuse som ikke blåser ut varm gass.
Looks like it has become a standard, but I have actually no clue. I prefer to work with old phones; max 48V DC + 90V 25HZ
dsk
Its ok. I want to say thank you over and over, at this point you have given me mountains of information!
I am still learning all of it!
So, considering the transformers, am I correct 3 types of IT supplies existed in Norway?
230 IT
400 IT
690 IT
And 400 and 690 in buildings was stepped down to 230 with building owned transformers?
Here is the USA larger buildings are fed with 277/480Y TN-C-S supply from power provider. 277 for lighting and 480 for motor. 480 is then stepped down to 120/208Y TN-S in the building for electrical sockets.
Just to add, I think a wye primary is a poor choice. If the impact protection shorted to ground, and a phase was also faulted to ground on the LV, this would create a neutral shift in the vector. The other phases would go over 230 volts damaging what ever is connected to them.
Just some friendly advice for Norwegian utilities... I mean no harm
690 are not a used standard here, but more a special ting. 230V IT ,TT , TNC-S are used. 400V are usually TNC-S not IT. Private transformers are usually small for single units using e.g. 400V when 230 are supplied or vica verca. Atotransformers are banned.
Trams/subways runs on 750V DC Train on approx 16-20kV 16-2/3Hz
Don't sweat it You may not have all the knowledge in the world in this area, but so far this thread has become a gold mine of information I never imagined.
DSK, let me say thank you over a hundred plus times! You have contributed so much to this thread and answered all my questions hundreds of times over with detail. I have learned a lot. Great stuff.
I think you are proof that Scandinavian nations are the nicest and happiest place on earth. Now I know why Norway has so little crime, as its impossible to feel left out of anything. Everyone is so helpful.
Thank you for your time! Many thanks from the USA!
Apparently Denmark is an island between Germany and Sweden using 25 kV/50 Hz, the modern European railway standard.
The early adopters of electrical railways chose either DC or low-frequency AC because such motors can be controlled simply with series resistors. Before the days of solid state inverters controlling the speed of a 50 Hz AC motor was incredibly complex and required chunky machinery on each loco/EMU. The Hungarians went through all that trouble when they electrified their railways in the 1930s because it was still cheaper than dedicated railway power plants or huge rotary converter stations as we still have in Austria (Germany and Switzerland are moving over to solid state inverters). Seems like Denmark chose the Hungarian way.
Edit: low-frequency AC had one huge advantage, it could be transformed on board of the train. Motors at that time couldn't run on more than about 1000-1500 V so DC systems could only go up to 3 kV with series-wired motors but AC systems could easily have 15 kV overhead wire voltage and transform it down to something manageable. The high voltage greatly reduces current and voltage drop, that's why some countries have a mix of power systems, DC on older lines and AC on newer high-speed lines. Apparently the Dutch can't run electric freight trains because of the limits of their 1.5 kV DC overhead supply!
The Czech Republic is split, the North is DC and the South is 50 Hz AC.
It's interesting, and I'm learning a lot too. I have designed,(and partly built) units for export to USA, Australia, and other countries. Only the US marked has been a challenge because of their own standards so different from Europe.... or actually not when you learn it to know. Most US 480V machinery will run at 400V 50 hz and visa versa. 20% more power out in the 480V system, but it works, and no smell of burned equipment :-)
By the way, last time I visited USA, I registered high voltage with 3+N and only 3 wires (connected to the transformers to the consumers network), eg in different parts of CA. What will be the difference, and normal voltages? (Reference to other threads or pages? since this not fits this thread?)
By the way, last time I visited USA, I registered high voltage with 3+N and only 3 wires (connected to the transformers to the consumers network), eg in different parts of CA. What will be the difference, and normal voltages? (Reference to other threads or pages? since this not fits this thread?)
dsk
What are you referring to as "high voltage"?
For voltages in CA, the largest utility is PG&E, & here is a link to the "Greenboook" which lists the voltages they supply.
Huge document, I will need some time to read all that. :-)
This picture http://tinyurl.com/hs7q4wy shows a pole, sometimes the supply has 3 wires, and service neutral, sometimes only the 3 wires. The transformer primary is connected between N and one supply wire, or 2 of the supply wires. What use to be the primary voltage for these transformers?
In California 16kv is very common followed by 12kv, the lines are usually 3 wire on the HV and have no neutral. Transformers are connected L-L or delta. There are some 4 wire lines where the HV neutral is insulated, and those are typically 2.4/4.16kvY.
Outside of California 4 wire is common for the HV with the neutral multi grounded (multi grounded mostly forbidden in California). Typical voltages are 7.2/12.47Y, 7.6/13.2Y, 7.9/13.8kvY, 13.2/23kvY, 14.4/25kvY and 19.9/34.5kvY. 2.4/4.16Y and 4.8/8.36kvY often found on older systems which are now obsolete.
I did hope this would be something different, and make them look at it. Obviously not. How dangerous might this be? Probably worst for the transformer close to. I do not use to stand and lean to those poles in bad weather. :-)
I could not resist to share this picture. It is not by code! When you biuld a house and a neighbor has their drop running over your property, you temporarily fix the wire in a tree, cuts down the pole, and builds the house with the wire going trough! Then you may get it solved when you get the powercompany to connect your house, and hopefully just pay for one visit. Ill guess the risk never has been evaluated, but this is a cable with 2 wires, 230V between, and approx 127 V to ground.
They could convert the existing buildings too, it'd take new cables and some inside work too. I guess a dual-voltage transformer wouldn't be enough for running both systems in parallel since the old setup requires a floating star point (IT) while the new one needs an earthed one (TN).
I suppose they could convert the older parts to 133/230 V TT if they're currently 133/230 IT with earthed local PE. That'd be the Belgian system, once common in quite a few European countries. They'd still need a transformer with separate secondaries I guess. If all existing supplies are single phase (i.e. only two out of the three phases are supplied, giving 230 V) they could replace the distribution and reconnect the existing buildings to 230 V line to neutral instead.
Here is an interesting PDF (yes I know its in Norwegian but can be translated). Stresses importance of RCDs in IT systems due to the lack of interconnected ground systems between buildings:
![[Linked Image from electrical-photos.com]](https://www.electrical-photos.com/data/501/medium/2014-08-05_12_18_40.jpg)
![[Linked Image from electrical-photos.com]](https://www.electrical-photos.com/data/501/medium/2014-08-05_12_18_51.jpg)
![[Linked Image from electrical-photos.com]](https://www.electrical-photos.com/data/501/medium/2014-08-05_12_19_17.jpg)
![[Linked Image from gfretwell.com]](http://gfretwell.com/ftp/bar.jpg)
![[Linked Image from upload.wikimedia.org]](http://upload.wikimedia.org/wikipedia/en/thumb/f/f3/Y_in_delta_network.svg/1142px-Y_in_delta_network.svg.png)
![[Linked Image from img.photobucket.com]](https://img.photobucket.com/albums/v480/dsk/EL/Trafo%20Lillehammer/2015-01-18115110_zps3a6cd880.jpg)
![[Linked Image from img.photobucket.com]](https://img.photobucket.com/albums/v480/dsk/EL/Trafo%20Lillehammer/2015-01-18122142_zpsf8ff2ce8.jpg)
![[Linked Image from img.photobucket.com]](https://img.photobucket.com/albums/v480/dsk/EL/Trafo%20Lillehammer/2015-01-18122119_zps9d674328.jpg)
