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Utility source impedance
https://brainfiller.com/arcflashforum/viewtopic.php?f=23&t=3466
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Author:  jfann [ Sat Oct 04, 2014 10:52 am ]
Post subject:  Utility source impedance

The utility company has provided me with the actual fault current on the secondary side of the Utility transformer but no source impedance information. Would the source impedance be applicable on the secondary side of the utility transformer?

Author:  wbd [ Sat Oct 04, 2014 12:31 pm ]
Post subject:  Re: Utility source impedance

The source impedance on the secondary side of the transformer would include the transformer impedance.

Author:  arcad [ Sat Oct 04, 2014 2:33 pm ]
Post subject:  Re: Utility source impedance

jfann wrote:
The utility company has provided me with the actual fault current on the secondary side of the Utility transformer but no source impedance information. Would the source impedance be applicable on the secondary side of the utility transformer?


What is the transformer nameplate KVA rating, %Z and X/R ratio, and how big is the fault current value provided by the utility company on secondary of the transformer?

Author:  jfann [ Sun Oct 05, 2014 11:26 am ]
Post subject:  Re: Utility source impedance

2500 kVA at 5.7%Z (X/R unknown), 45kA fault current.

Author:  arcad [ Sun Oct 05, 2014 12:44 pm ]
Post subject:  Re: Utility source impedance

jfann wrote:
2500 kVA at 5.7%Z (X/R unknown), 45kA fault current.


What is the transformer secondary voltage?

Author:  jfann [ Sun Oct 05, 2014 5:27 pm ]
Post subject:  Re: Utility source impedance

480V. (Transformer is 24kV to 480V)

Author:  arcad [ Sun Oct 05, 2014 7:31 pm ]
Post subject:  Re: Utility source impedance

jfann wrote:
480V. (Transformer is 24kV to 480V)


The source impedance, avail short circuit current and short circuit MVA on primary side of the 2500KVA, 5.7%Z 24KV/480V rated transformer with 45KA avail short circuit current on its secondary is roughly equal to 2Ohms, 6kA and 250MVA respectively.

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