Fault current Analysis
Fault current Analysis
(OP)
Dear All
i am designing a Distribution system having one 2MVA 22kV/415V Transformer and one MAIN DISTRIBUTION BOARD (MDB) and 5 Distribution Board (DB). i obtain 40kA Fault in Transformer secondary and in every DB the Fault level is more than 30kA.
I want to reduce the Fault current level less than 15kA in every DB.
Please help me is any solutions are there to reduce the fault level at DB.
Regards,
LSK
i am designing a Distribution system having one 2MVA 22kV/415V Transformer and one MAIN DISTRIBUTION BOARD (MDB) and 5 Distribution Board (DB). i obtain 40kA Fault in Transformer secondary and in every DB the Fault level is more than 30kA.
I want to reduce the Fault current level less than 15kA in every DB.
Please help me is any solutions are there to reduce the fault level at DB.
Regards,
LSK






RE: Fault current Analysis
RE: Fault current Analysis
RE: Fault current Analysis
The system is already designed. so it is impossible to increase the length between MDB and DB aswellas the size of the transformer.
So please let me know is the any other solution is available.
Regards,
LSK
RE: Fault current Analysis
Probably a lot cheaper than reactors and no worries about the magnetic field from a large air core reactor heating up nearby structural metal.
Bill
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"Why not the best?"
Jimmy Carter
RE: Fault current Analysis
RE: Fault current Analysis
No offense, but the nature of your question indicates you need to find someone with more experience to assist you.
Also, the fact that a system is designed does not preclude changes. The fact that a system is built and operating does not preclude changes.
RE: Fault current Analysis
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Fault current Analysis
I suggest that you at least calculate the length of feeder cable required to reduce the fault current to an acceptable level.
Bill
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"Why not the best?"
Jimmy Carter
RE: Fault current Analysis
You might want to consider current limiting fuses. In the USA, this would only be helpful if the equipment were tested with the selected protective equipment and given a "series rating". I don't know if there is a similar procedure for IEC equipment.
The best solution would be to purchase higher rated equipment. It doesn't seem reasonable to have an MDB rated for 3 kA load with only a 15 kA fault rating.
RE: Fault current Analysis
That said, to rate the DBs at 15kA would still require further work depending on what is installed in them. Assuming that we're discussing the style of DB I'm thinking of, say, light & power distribution within buildings, most of the miniature circuit breakers are only rated to 6kA, sometimes lower. This would mean either putting more expensive circuit breakers in for every circuit, or revisiting the whole design.
If it were DBs for some sort of industrial application, I'd be rating all the sub boards higher.
RE: Fault current Analysis
For instance if-let's say the DB is supplied by 3*1/c 1000 MCM copper triplexed cables- approx.20 m [65ft]-and the reactance will be 0.002 ohm if the cables will run at 2 ft distance apart then the reactance will be 0.0049 and the short circuit current will be 22 KA. Of course you have to check the voltage drops [mainly in the case of induction motor starting] as jghrist indicated.