Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Duncan Brown — Tue, 27 Feb 2018 09:43:57 GMT

Happy to have helped.

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Andy Leask — Tue, 27 Feb 2018 06:50:57 GMT

Wow, thank you very much Duncan, i was dubious about using the likes of a forum to answer this simply due to never having used 1 before. I am sold, you have been excellent, thank you.

a colleague did say could the device be limiting the current.

Honestly, thank you. I will relay this back and may be back with more questions once i have spoken to colleagues

Andy

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Duncan Brown — Mon, 26 Feb 2018 15:52:12 GMT

Andy - you have used current limiting devices in the circuit (Schneider Compact NSX MCCB + Micrologic 2) - Under fault conditions, the current is limited. This document contains a little more information.

In the example circuit, for example, the device on MSB/SA way 3 is an NSX400 N 2.3 50kA. If you examine the device data, you can see that the let through energy is going to be between (I haven't interpolated the figure exactly) 6 and 7kA.

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Andy Leask — Mon, 26 Feb 2018 15:33:33 GMT

It is the fault current up to Block 3 End feed unit - BB/01-SA/B3/EF01 is the final value i need, handballing the calc we arrive at around 6kA. if we go from the transformer to MSB/SA we are going from 24kA to 6.4kA through 3 No. 185mm2 armoured cables.

Does that help?

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Duncan Brown — Mon, 26 Feb 2018 15:24:11 GMT

Andy - can you let me know what you are examining upstream? Is it a particular way?

Thanks,

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Andy Leask — Mon, 26 Feb 2018 15:07:43 GMT

Hi Duncan

Thanks very much for the rapid response, i have sent it over and i hope it helps.

RE: Large loss of PSCC across first leg of circuit from Transformer to Main switchboard

Duncan Brown — Mon, 26 Feb 2018 14:59:03 GMT

Hi Andy - I couldn't possibly comment without seeing the project. Please exit the software, go to your project folder, zip up the files and use this link to get the zip file to me.

Thanks,