I know a company that uses this..
Aerosol - ESC Electrical Contact Cleaner Spray - 500ml - [AT-1487] - http://www.thesafetysupplycompany.co.uk/p/8954323/aerosol---esc-electrical-contact-cleaner-spray----500ml---at-1487.html?gclid=CjwKEAjw4vzKBRCt9Zmg8f2blgESJADN5fDgvfGfr2lGv4q91BRXOKGuZVQs0qVr5sEUVOuKGhBU6RoCMKXw_wcB
on their supply leads in a factory.
I don't think you really need to worry too much about it though.
Fundamentally, it appears as if the protective devices are introducing significant impedances to question the effectiveness of your protective measure. If I was in that position (assuming I can personally verify the accuracy of my instrument) I would accept and record the readings
measured. If these are too high I would try a replacement and would contact the manufacturer for their spiel, and maybe record it on the documentation.
Using calculation to compare your measured value, is for purposes exactly as you are demonstrating here.
For the argument of referring to calculation instead...
Opting to refer to calculation over measurement would be naive. In a real world scenario, a fault current is going to flow down your measured impedance, not your calculated impedance. Calculations, while useful, never compensate for connection resistances, contact resistance or arc gaps.
Yes, the H&S world, Training courses, Guidance Note 3 and the incoming 18th edition all suggest EFLI can be verified by calculation with the measured protective conductor continuity and supply impedance loop. But these fault currents don't flow down imaginary numbers.
Also, the disconnection of a protective conductor when verifying continuity will remove the parallels. When we measure Zs we want the parallels.We need to start paying more attention to the pefc and pscc (and therein the pfc) within our circuits and not just at the origin or submains. The 18th edition is planning on introducing terms like:
- rated short-time withstand current, Icw (already there)
- rated peak withstand current, Ipk
- rated conditional short-circuit current, Icc
These have been around for powertrack busbar systems but are now going to be more commonly used for any assembly. So we will need to set our testers to pfc (which means it will do an EFLI test and play with ohms law) and make sure all the parallels are there to ensure we measure the highest pfc value.
