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Line impedance query

me1899
Hi 


I am looking at a job where a supply to a replacement CT scanner has to be calculated.


The current scanner is fed by a cable with line impedance 0.06 at source end of the sub panel that feeds it.


The new scanner must have a line impedance no more than 0.06 so basically I can't use the way on the current panel.


The client engineer has said to run from the intake and provide a cable calc to prove the line impedance is OK for the new scanner feed (this is D and B).


I am using AMTECH and was wondering if there was a way to output line impedance or if I need to show a calculation another way?


The client engaged a firm to do line impedance tests, and their report shows values measured between L1-L2, L2-L3 and L1-L3, but looks like they did testing at the sub panel and not at the intake.


This is basically like PSCC right? So I can get PSCC from AMTECH, divide by root 3 and work out impedance from there?


Am I on the right track? Assistance would be much appreciated.


Regards


Anisur
Parents
  • 0
    Hi All


    As an update, looking at the line impedance readings between phases, we instead took measure L - N voltage and divided by corresponding PSCC to get impedance of each phase. That gave us enough play to propose a 95mm 5 core of sub 30m length.


    The manufacturer and main consultant have been advised and give a copy of cable calcs. I note the manufacturer asked for CPC to at least match phase conductor size, so we put in a 5 core and that gets less than 0.06 for Zs.


    From site we also confirmed that the feeding board is genny backed so we have asked the question of the main consultant seeing as the unit is not due to be supplied with a UPS - just waiting an answer from them.


    Sorry for slow update, but been bogged down.


    Hope this will be OK now and all relevant parties will be satisfied.


    I really appreciate and hugely grateful for all the valuable contributions that have been given to this question.
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  • 0
    Hi All


    As an update, looking at the line impedance readings between phases, we instead took measure L - N voltage and divided by corresponding PSCC to get impedance of each phase. That gave us enough play to propose a 95mm 5 core of sub 30m length.


    The manufacturer and main consultant have been advised and give a copy of cable calcs. I note the manufacturer asked for CPC to at least match phase conductor size, so we put in a 5 core and that gets less than 0.06 for Zs.


    From site we also confirmed that the feeding board is genny backed so we have asked the question of the main consultant seeing as the unit is not due to be supplied with a UPS - just waiting an answer from them.


    Sorry for slow update, but been bogged down.


    Hope this will be OK now and all relevant parties will be satisfied.


    I really appreciate and hugely grateful for all the valuable contributions that have been given to this question.
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