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jfann
 Post subject: Utility source impedance
PostPosted: Sat Oct 04, 2014 10:52 am 

Joined: Sat Oct 04, 2014 10:42 am
Posts: 3
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?
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wbd
 Post subject: Re: Utility source impedance
PostPosted: Sat Oct 04, 2014 12:31 pm 
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Joined: Wed May 07, 2008 5:00 pm
Posts: 881
Location: Rutland, VT
The source impedance on the secondary side of the transformer would include the transformer impedance.
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arcad
 Post subject: Re: Utility source impedance
PostPosted: Sat Oct 04, 2014 2:33 pm 
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Location: Toronto
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?
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jfann
 Post subject: Re: Utility source impedance
PostPosted: Sun Oct 05, 2014 11:26 am 

Joined: Sat Oct 04, 2014 10:42 am
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2500 kVA at 5.7%Z (X/R unknown), 45kA fault current.
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arcad
 Post subject: Re: Utility source impedance
PostPosted: Sun Oct 05, 2014 12:44 pm 
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jfann wrote:
2500 kVA at 5.7%Z (X/R unknown), 45kA fault current.


What is the transformer secondary voltage?
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jfann
 Post subject: Re: Utility source impedance
PostPosted: Sun Oct 05, 2014 5:27 pm 

Joined: Sat Oct 04, 2014 10:42 am
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480V. (Transformer is 24kV to 480V)
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arcad
 Post subject: Re: Utility source impedance
PostPosted: Sun Oct 05, 2014 7:31 pm 
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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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