LOOP IMPEDANCE & PFC - ASSESSMENT TIPS - PROSPECTIVE FAULT CURRENT ZE PSCC ZS - UNDERSTAND THE TESTS
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- เผยแพร่เมื่อ 18 พ.ค. 2024
- Recently, we made a video on validating ring circuit test results with tips on what you should know for electrical assessments. This video follows on from that and looks at Earth Fault Loop Impedance testing, Ze, PFC and more.
Again, we keep to very simple drawings and explanations and concentrate on what you should know before any assessment.
And we will give you some tips on what the assessor might ask, the sort of things that I used to ask.
All electrical training courses will include end of course exams and/or assessments that are designed to test your abilities and understanding of the course that you are completing.
In this video we look at loop impedance or Ze. What is it and why it is important.
But, we can’t do this without understanding the three common types of earthing systems, why they are different and how to test them.
And then we will move on and ask - What is prospective fault current and prospective short circuit current, what does each one mean and where are they measured in the circuit.
We will begin with TN-S earthing systems and move on to TN-C-S and TT installations where things are very different.
This is video number 220 and to view all our videos type in LearnElectrics all one word into the TH-cam search bar.
Visit our TH-cam channel where we have many more videos on a wide range of electrical topics.
I needed this video. Excellent teaching method. Cheers.
Good to know the video has done its job. Thanks. Dave.
Thankyou for this training video…… another addition to my mental toolbox …..your videos are really appreciated
Great, thank you. Appreciated. Dave.
You and your videos, man! Wicked!
Thanks for that, appreciated.
Another great video. Really appreciate your hard work in making these videos. It has helped me alot.
Glad to hear it and thanks for watching, appreciated.
Wow a great video.
Exception, simple and accurate.
Thank you.
It's really fun and learns to see your videos.
Glad you like them and thank you for watching. Appreciated, Dave.
Thank you for this video. Dankeschön!
You are very welcome.
Well come mate.
Glad it was useful, thanks.
Thanks again for a clear explnation. For Ze you show (for all types of earthing arrangements) the three wire method for test leads, with one to L, N and E. When measuring PSSC you say that it's "exacly the same test leads and meter set up" but show the blue and black wires from the meter joined together on the N conductor. That is the correct configuration for measuring PSSC?
Correct. The measurement is between Line and Neutral, so the black earth lead is is on the neutral. but the meter needs the neutral connection, so we put the blue neutral lead there too. Have another look at the video, it is explained. Thanks. Dave.
I believe, that Zs not only the Eart Fault Impedance. I think, that the Line-Neutral loop impedance is also called Zs. The Prospective Fault Current (PFC), and the Prospective Short Current (PSC) is also depends on system loop impedance (Zs). Do I see well? Thank you for your very useful work! 👍
No, Zs is a line to earth fault. Between line and neutral it is a short circuit. Have another look at the video. Thanks for watching. Dave.
Thank you for this video it’s a great explanation ! I just wanted to know, why the overhead power supply can’t provide TN-C earthing arrangement ?
Its whatever method that the supplier uses when installing a supply. We just work with what they give us.
Do we also test pscc between phases on a 3 phase system? This current can be way more than pscc between L and N. Will the CB be able to handle this short circuit current?
We can m measure PSCC between L & N but most test meters will not measure between phases as they are not designed for 400V. We choose the worst case PSCC from the single phase testing and multiply by 2. We use this as the prospective 3 phase short circuit current. have a look at Appendix 14 page 554. Dave.
I cannot thank you enough for these wonderful videos.
I was wondering. Why Ze must be a live test? Why difference it will make if we test it without electricity?
Is it because we have transformer which has windings coil that is inductive resistance?
You cannot test Ze as a dead test without turning off everybody else electricity in the town. Its a live test back to the suppliers transformer, This video will help.
th-cam.com/video/xtDId-g7GjU/w-d-xo.html
Hello! Where is the additional source electrode (PME) on the TN-C-S drawing...? Thank's for the video!
PME uses the electrode back at the supply transformer.
Take a look at this video on earthing systems. Thanks for watching. Dave.
th-cam.com/video/qAah0Uqx9oI/w-d-xo.html
If we have a Line and neutral conductor back to the transformer then why not convert TT systems to TNC-S arrangements throughout.
We need a line and neutral from Source to dwellings anyways so we already have a complete circuit from supply!!
I'm guessing it's not that easy as it would have been done already..It makes me wonder sometimes tho considering how unstable TT systems can be under some circumstances..
Id assume it’s because tns and tncs are bonded to star point through MET. It doubt it would be feasible to have a single earthing terminal for a property going back to the transformer thus the need to earth it seperately.
The TNS and TNCS cables are of different construction. If they are retro-fitted as overhead cables, the weight can be quite substantial. Good question.
Thanks for taking part Daniel, appreciate the input. Dave.
I’m slightly confused.
Why do we need to do PFC?
That is the purpose.
Thanks for the fantastic video!
Its one of the essential tests and helps us ensure that the devices can handle the fault current.
@@learnelectrics4402 thank you
But I don’t understand which part of the breaker will this help with?
I know we need the short circuit part.
But I’m now aware of any scenario where we can practically use PFC to choose breakers or anything else
I doubt it could be made much clearer.
Very nice reply, thank you. Dave.