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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
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  • Former Community Member
    0 Former Community Member
    If you look at HTM 06-01, the generator should be on line within 15 seconds of a LoOP event (Loss of Offsite Power) ie both primary and secondary HV have failed (or you want the set idling if primary has failed just in case secondary follows it


    It is entirely feasible to delay the circuit breaker feeding the CT for longer  - eg, you open the CB on loss of supply with a spring recharge on the breaker, and then when it detects generator volts, it counts for a pre set time before closing - you may need this anyway to manage the load step


    Sounds like said consultant doesn't really know what he wants and is making this up on the hoof


    Regards


    OMS
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  • Former Community Member
    0 Former Community Member
    If you look at HTM 06-01, the generator should be on line within 15 seconds of a LoOP event (Loss of Offsite Power) ie both primary and secondary HV have failed (or you want the set idling if primary has failed just in case secondary follows it


    It is entirely feasible to delay the circuit breaker feeding the CT for longer  - eg, you open the CB on loss of supply with a spring recharge on the breaker, and then when it detects generator volts, it counts for a pre set time before closing - you may need this anyway to manage the load step


    Sounds like said consultant doesn't really know what he wants and is making this up on the hoof


    Regards


    OMS
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