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?
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.