Transformer Fault Current Calculation Spreadsheet

Transformer Fault Current Calculation Spreadsheet

Transformer Impedance

Transformer Impedance is measured in Percent Impedance, this is the percentage of rated primary voltage applied to the Transformer’s primary winding in order for the rated secondary Full Load Current to flow in the secondary winding (this test is preformed with the primary winding connected to a Variac or variable supply and the secondary winding shorted-out).

Transformer Impedance values may vary but typically Blakley Electrics transformers will be between 4 to 5% of primary Voltage.

For further details please contact Blakley Electrics‘ Technical department.

Impedance Voltage Vz = ( Primary Volts V x Percent Impedance Z% ) / 100

Transformer Maximum Fault Current Allowing for Loog Impedance

To calculate the Maximum Fault Current that can be achieved in a circuit fed by a transformer we refer to the below formula.

Maximum Fault Current

This formula calculates the loop impedance at the end ofa circuit fed from the secondary winding of a transformer. When calculating Fault Loop Impedance Select the Correct Transformer Type Above. Three Phase Transformers Divide the Values for Vs secondary Voltage by √3 and the VA by 3.

For Centre Tapped to Earth (C TE) transformers halve the values for Vs and VA . For RLV / 110V C TE Disconnection Times & Zs figures refer to BS 7671:2008, 411.8 Table 41.6.

Software:Transformer Fault Current Calculation – Blakley Electrics
Developer:BLAKLEY Electrics
Downloads:Right here

Transformer Fault Current Calculation

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Page edited by E.C. (Google).


  1. success
    Oct 20, 2014

    Keep up the good work

  2. Bassam alhaboob
    Aug 18, 2013

    thank you

  3. nedal nemer
    Jun 09, 2013

    very cool

    Mar 21, 2013

    this site
    helps lot.

  5. carsona
    Sep 23, 2012

    I like this site a lot its really good.

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