IT Network
IT Network
(OP)
Hi forum members,
I need a clarification about the IT network.The neutral is not grounded and this network is only allowed for three phases load.For single phase load, a delta/star transformer is used to provide the neutral.At a place of work, I noted that this neutral is not grounded.I belive this is a violation of the code as the neutral is no longer at earth potential.
Guardiano
I need a clarification about the IT network.The neutral is not grounded and this network is only allowed for three phases load.For single phase load, a delta/star transformer is used to provide the neutral.At a place of work, I noted that this neutral is not grounded.I belive this is a violation of the code as the neutral is no longer at earth potential.
Guardiano






RE: IT Network
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If we learn from our mistakes I'm getting a great education!
RE: IT Network
RE: IT Network
The data people came up with grounding schemes to address unreliable grounding systems. At the same time, codes were changing and modern ground methods became as dependable and reliable as the "Special grounds".
What is the voltage. If a neutral point is available that will limit the maximum nominal voltage to ground to less than 150V then the system must be grounded. If the system is not grounded, all equipment must be capable of withstanding phase to phase voltage applied phase to ground. Not all equipment is suitable for use on floating systems. Blown front ends on rectifiers and other equipment may result from a remote ground fault.
Another North American code violation. If a neutral is used for line to neutral loads the neutral must be grounded.
In North America it is common for IT to install a dedicated ground bus for all it grounding. Then, the electrical contractor connects this bus to the main building/system ground bus with a 4/0 copper cable to satisfy code requirements.
I always laugh when I see a magic triangle being installed. This is three 3M ground rods in a 3M equilateral triangle. The grounding system in an industrial may entail 1000 times the weight of the "magic triangle" of copper cables. There is actually a danger that a massive ground fault, on its way to the main ground grid may, cause an elevated ground potential on the IT network. However, if the installation is up to code there will be a large ground cable connecting the magic triangle to the main ground grid and thus saving the it people and equipment from harm. We have learned to not waste time arguing with IT guys. They seem to have a contempt for anyone working with power frequencies, currents and voltages and can not possibly learn anything new. They know Ohm's law, what more is there to power systems?
We quietly install the jumpers to bring the system up to code and make it safe and avoid confrontation. If you make a big deal out of connecting the IT ground to the system ground, the ITs may disconnect it after you have left.
Install the proper grounding quietly and what they don't know may save their lives and/or equipment.
Bill
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"Why not the best?"
Jimmy Carter
RE: IT Network
David Castor
www.cvoes.com
RE: IT Network
While I was on the Information Technology soapbox, the OP may have intended the European IT or floating neutral systems.
And I was on a roll!
LPS for the link and my further education.
Bill
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"Why not the best?"
Jimmy Carter
RE: IT Network
David Castor
www.cvoes.com
RE: IT Network
Guardiano
RE: IT Network
I can see a possible 'safety problem' caused by the relatively high source impedance and the low fault level which will potentially cause difficulties with fault clearance times. That shouldn't be anything which can't be dealt with using normal methods, e.g. RCD or RCBO. Another safety problem may occur if you have supplies from both systems in the same area, especially if some helpful soul decided to bond the neutrals or use a convenient neutral from one service and a convenient phase from the other service to power a load. Bad workmanship for sure, but that doesn't mean it can't happen.
Is the isolating transformer a Y-Y type or a DY?
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If we learn from our mistakes I'm getting a great education!
RE: IT Network
Guardiano