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High earth loop impeance at Transformer

MS01

Hi There, 

We have just installed a new 800kVA transformer on site with a impedance of 4.75%. However when it comes to taking the EL reading at source we are getting 0.12-0.14ohms compared to what we expect of 0.01-0.02 ohms. 

Other than checking the cable connections, changing the meter or having faulting TX can anyone give me some ideas why this may be. Has anyone come across this before?

  • 0 in reply to John Peckham

    "The maximum output current will be 800000/(400 x  3) = 1154.73A rounded up 1155A.

    The prospective fault current will be 1155 x (100/524.75) =  24.316kA.

    The voltage to earth is 433/Route 3= 250V.

    Ze = 250/24316 = 0.0102".

    Spot the error/s. 

    Jaymack

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