Welcome to Talk Electrician Forum
|Welcome to Talk Electrician Forum, the UK's Friendliest Electrical forum on the internet, whilst you can view all our posts and topics like most online communities you must register to post (reply, or ask a question) in our community, but don't worry this is a simple free process that requires minimal information for you to signup. We do have different membership levels (called silver and gold) as a subscription service, BUT, this is an extra, and not needed, So please feel free to join for FREE, and then decide if you like our community, and would perhaps like to subscribe to any of our our extra services. Our members offer the best advice in the electrical industry including DIY,Domestic,Commercial,Industrial,Renewables,Health and Safety issues and Control and Automation.
Be a part of Talk Electrician Forum by signing in or creating an account.
Calculating Prospective Fault Current
Posted 19 April 2012 - 09:44 PM
Posted 19 April 2012 - 09:50 PM
Your PFC is the higher of PSSC and PEFC (both taken with earth and bonds connected)
Posted 19 April 2012 - 09:51 PM
Posted 19 April 2012 - 10:35 PM
Posted 19 April 2012 - 10:38 PM
Edited by johninlondon1, 19 April 2012 - 10:39 PM.
Posted 19 April 2012 - 10:40 PM
Think ill stick to Grape Testing as thats easier......
Posted 19 April 2012 - 10:54 PM
You`d make a good living from it if you could do more in a day, but alas! Its so tiring. Makes you want to just curl up in a baZzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
Posted 19 April 2012 - 11:00 PM
I regretted selling my other Megger separates good quality and reliable is how I'd describe them.
Posted 19 April 2012 - 11:20 PM
Would still be using it but not practical with having no dik.
I regretted selling my other dik.
Can you say things like that on here???
Posted 20 April 2012 - 07:27 AM
You test Ze right at the incomer, BEFORE any RCD's, so your tester will work just exactly the way it was designed to work. If you are having trouble tripping RCD's you are testing in the wrong place.
Granted your tester won't be able to measure Zs on a final circuit with an RCD, so you will have to bypass the RCD or calculate that, but you were talking about measuring Ze
Anyway back to the original question, that tester only gives the impedance, so PSSC and PEFC HAVE to be calculated using law.
Posted 21 April 2012 - 10:27 AM
Posted 21 April 2012 - 10:59 AM
Posted 21 April 2012 - 04:39 PM
How to test Zs on a RCD protected radial circuit.
Turn OFF RCD, short L to E at the end of line of the circuit (Furthest point from supply)
Connect one lead of your tester and connect to OUT GOING line terminal of the RCD ( RCD SWITCHED OFF)
CAREFULLY Connect the other lead to the INCOMING Line terminal and take reading.
Your Meter bypasses the RCD so it will not trip and you get a reading using the full 25 Amp test current.
Remove leads, remove short at end of line and you have it, accurate direct reading
I had to draw it out to prove to myself it would be a true reading when shown this Method.
Try it and see for yourself
Edited by sparkytim, 21 April 2012 - 04:43 PM.
Posted 21 April 2012 - 05:25 PM
And can I just add that the only way for ANYONE to measure Ze is the way you describe - if earthing conductor is connected to MET , you`ve effectively measured Zs(DB) - which isn`t a recognised measurement in 7671; but is widely used.
Ze is measured with the isolator off and the earth disconnected BUT the PEFC is measured with the earth connected and all bonding in place.