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Trimble Pro Design - Energy Let Through & Adiabatic Issues

SparkyKris

Hi All

I’ve been in the industry for about 20 years but only just started to do some small designs on Trimble Pro Design Software. So far on the last hand full of projects been relatively problem free but on this particular project I’ve been having issues the prospective fault current. A direct measurement on site has been done as Ze 0.04 (5.8kA). The first issue I had is we are planning to fit Hager combined AFDD/RCBO which are rate at 6kA. As these will be protected by a Hager 200A MCCB its allows me to use back up protection which has now cleared the error. But the issue i have now is the Line & Earth Adiabatic equation is now throwing up errors on all my circuits. I believe the software’s may be think my 16A circuit with 2.5mm T&E is relying on solely the 200A for short circuit protection? On some it’s saying my CPC needs to be at least 13.5mm. I have tried everything I can to think of but with no luck. Can anyone shed some light on this, in particular if you use the software yourself. Thanks in advanced.

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    i don't know the software, so just guessing... one thought -  how long are the circuits? In the lack of anything obvious I wondering if there's something odd like Zs at the far end is too high for "instantaneous" operation of the MCB element of the RCBO and so it's thinking of much extended disconnection times - which might account for wanting a lager c.p.c. (either for adiabatic or lowering Zs). The theory doesn't entirely add up (it's ignoring the RCD element of the RCBO, but many prefer not to rely on RCDs for ADS if they can help it so there may be an option in the software to that effect?) and if the c.p.c. had to be 13.5mm² to meet the adiabatic then the line conductor would need to as well - so perhaps hinting it's an overall Zs rather than c.s.a. issue.  (Assuming a fault current of around 6kA and k=115 then 13.5mm² might suggest a disconnection time somewhere around 0.07s - far too slow for an MCB in instantaneous mode)

       - Andy.

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  • 0

    i don't know the software, so just guessing... one thought -  how long are the circuits? In the lack of anything obvious I wondering if there's something odd like Zs at the far end is too high for "instantaneous" operation of the MCB element of the RCBO and so it's thinking of much extended disconnection times - which might account for wanting a lager c.p.c. (either for adiabatic or lowering Zs). The theory doesn't entirely add up (it's ignoring the RCD element of the RCBO, but many prefer not to rely on RCDs for ADS if they can help it so there may be an option in the software to that effect?) and if the c.p.c. had to be 13.5mm² to meet the adiabatic then the line conductor would need to as well - so perhaps hinting it's an overall Zs rather than c.s.a. issue.  (Assuming a fault current of around 6kA and k=115 then 13.5mm² might suggest a disconnection time somewhere around 0.07s - far too slow for an MCB in instantaneous mode)

       - Andy.

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  • 0 in reply to AJJewsbury

    Hi Andy

    Thank you for taking the time to reply. I should have mentioned originally but I was trying to somewhat keep the original post a bit shorter but well as the CPC being too small it was also saying this about the line conductor as well. As the Ze (or Zs at the incoming supply in this case) is only 0.04 and some of these circuits are only 15 - 30m long I highly doubt it’s an issue with the Zs. Also, the software does have a different type of error that displays for high Zs as I’ve had to deal with that issue in the past. I believe it’s a case of a software issue rather than how the circuits have been set up. I’m trying to use the Hager 200A MCCB to back up the breaking capacity of the Hager 6kA AFDD/RCBO but obviously still want the AFDD/RCBO to still protect the circuit on short circuit & overload. 

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