Measuring Prospective Fault Current (PFC) at the Origin of a Single Phase Supply (Live Test)
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- Опубліковано 6 сер 2024
- Student training aid for the live test measuring prospective fault current PFC using a MFT Megger tester. Includes a full demonstration of how to measure PFC current. This test is shown being done under controlled condition in a college workshop. I measure both prospective short circuit current PSCC and prospective earth fault current PEFC and record the highest of the 2 readings.
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= 🕐 Time Stamps - Cut to the action 🕕 ==
00:00 - How to carryout a PFC test
02:21 - Isolating the consumer unit
03:37 - Testing between line and neutral of the incoming supply PSCC
04:27 - Testing between line and the earth bar of the incoming supply PEFC
05:35 - Testing between line on top of my circuit breaker MCB and neutral
06:01 - Testing between line on top of my circuit breaker MCB and earth bar
Videos are training aids for City and Guilds (C and G) and EAL courses Level 1, 2, 3 plus AM2, AM2S and AM2E assessments.
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Great vids, they do just what it says on the tin.
Very helpful, thanks guys.
Hi. Much appreciated GSH Electrical
All your videos have been instrumental in getting me through my 2365 level 3 - i've no doubt they will be of great value for my 2391-52 next week, thank you Gaz, your time and effort in making these videos is very much appreciated !!!
Great video. Love the attention giving on when to select the 2 hi, 2lo, 3lo setting on the device. Probably the best video I have seen for this so far.
Comprehensive and clear, thanks for your effort
Thanks 👍
Ta Gaz ... for making it all so clear 👍🙏
The nice thing you said in the end of this video. I hope this video some help to be honest it was hugely helpful not some help .thank you so much you are the best teacher I see him ever.
Massive thanks for the kind words it’s very much appreciated. 👍 I hope this message has been some help 😃
Excellent demo right on the money
Very instructive and well presented good job
+Vernon Jones
Thanks
Great video, really appreciated for my studying, thank you
Hi. So glad I could help. Keep working hard Gaz 👍
Gaz doing these videos through out the night by pendant light!Dedication!
It’s very much appreciated 👍🏻
great explaination and very easily understood....!!! Much Appreciate...!!!!
Thanks 👍🏻
Spot on and well explained as always. Good work Gary. Going to do my 2391-52 from tomorrow. Wish me luck. I am sure I will remember your videos. Thank you.
All the best 🦾
I passed the exam. Thank you for your video tutorials.
Gary again great video and 'HBSH'.
Always clear explanation thanks
Thanks for the support and positive feedback 👍🏻
Awesome Gary
Great video its nice to see someone explain the reason for the test and not just the method.
Should've listened more in physics
Whats that meant to mean?
Looking nice n relaxed as usual Gary
thanx teacher.big respect
Thanks for the positive comment it’s much appreciated. Gaz 👍
Good job
Excellent
Thanks👍
Great videos 👍
Thanks 👍
Thank you so much
No problem 👍
I thought Ze and pfc was done at the supply side of the breaker
Great clear and concise videos. With your PFC test on CU main switch at considerably less than the 33Ka of the incomer, under what conditions would you expect there to be any real chance of PFC across breakers to be greater than there 6Ka max? Thanks
Hi, thanks for the video I’ve got my AM2 soon and it’s going to be 3P+N main switch.
Carrying out this test I would crocodile clip onto the earth bar
One probe in neutral
One probe testing between L1,L2,L3 taking the highest reading and X by 2. Is this correct?
Also what setting would it be on as on a single phase board you switch between the 2?
Hi Gary can you please tell me how this is done using the kewtech kt62 multifunction tester or the ROBIN kts 1620 MFT as the instruction book says nothing about the two lead high loop test, on the control dial there are two settings, loop 20 ohms 200 ohms and 2000 ohms, psc 200A 2000A and 20ka also how to do Ze
Another great video thank you
Just to clarify, we dont measure the fault current, we measure resistance and the tester auto calculates it and shows it as result. You dont send 4-5-600A trough your tester.
The test leads would fry first
brilliant videos as always, my tutor is talking about the 3 lead method being the one we should use when testing, is this correct? and what is it
👍🏻
Gary, could you tell me why on. TNS system sometimes the Pefc and the Pscc readings are different when both the eart and neutral are essentially the same conductor and both test carried out with bonding in place so same parallel paths etc? Thanks.
for the am2s would i need to test PSCC for each breaker or just from the main switch ?
Reg 542-04-02 "The means os earthing must be disconnected from the installation earthed equipotential bonding for the duration of the test to remove parallel paths. This is to prove that the installation has a main earth. IET. Guidance note 3
Hi. Correct and I disconnect from the MET the protective bonding conductor disconnecting it from the main earthing conductor in this video. Thanks for watching GSH Electrical
For Ze testing only, you need to reinstate all bonding connections before carrying out PFC testing.
You only disconnect the main earthing conductor for Ze test, you need to reconnect the main earth for PFC
@@skamuk1 would that be not for the other tests mentioned, not the max PFC demonstrated here? I didn't see mention of the installation earthing being disconnected but he says in this reply that he did that though which is confusing me as it doesn't look disconnected.
Hi. Congratulations for the videos. Please, if you are so kind, two questions:
What is the reason for the difference between the measured PFCs of the two switches, being in the same point of the installation? In the case of Line-PE [424-312A] and in the case of Line-Neutral [311-332A].
Would the measures be different with all the charges connected?
Thanks
Hi. Normal practice is to measure PFC (PSCC and PEFC) only once. If the reading was less that the PFC of the smallest rating device in this case the circuit breakers 6KA then your sorted. I did it twice as a demonstration as this links to my class lessons on PFC. You have to do both PSCC and PEFC as PEFC picks up the parallel earth paths offered by extraneous conductive part (metal water pipe, metal gas pipe, metal frame of the building etc.) thanks for commenting and watching GSH Electrical
Thanks
Can someone advise me about how the instrument gets the current at time 4:33 please ? Are some assumptions made in the calculations ? How can the source impedence be calculated without removing the mains supply voltage ? I read elsewhere that in some instances a standard impedence value is used for the suppliers network and thus the max current is calculated. Is this true ?
I believe that as the circuit is energised it is a marginal resistance measurement. Thus actual voltage = I×R or current = V÷R
Very knowledgeable video, and without any water..
How would you calculate pfc ?Is it I=Uo/Zs ?
Voltage divided by ze
@6:03 you tested line and neutral on a high reading then switched to low reading when testing live and earth, because there's a rccb in the circuit but @6:03 isn't the rccb in the circuit aswel? Can you explain why High reading when live and neutral then low reading for live and earth please thank you
RCDs detect an unbalanced current between the L and N conductors on the outgoing side of the breaker. If the impedance test is done across the L and N terminals there is no imbalance, they are sharing the same amount of current during the test and will not trip. When doing the test between L and E, the RCD detects that the L terminal has current flowing during the test but the N terminal doesn’t, this imbalance will cause it to trip if done on the Hi setting.
What happens if you have BS3036 fuses with 1kA breaking capacity & your PFC reading is 3.17kA?
Is it a requirement of initial verification to test on the load side of the breaker? I thought Ipf was only on the supply side of the main incoming?
I don't think its a requirement, but if you want to do it for peace of mind then by all means do it.
It’s only to test the main fuse if you test on the supply side. If you test on the load side you’ll be testing the mcb/rcbo fault current is under 6ka.
Hi
In psc test why do you put red wire on neutral main isolated why mix the wire. And earth wire which is acting as neutral
Went on line. Main idolater
Thank you
Hi, is this one of the tests that you have to take when doing the level 2 diploma in electrical installations? Or is this for the level 3 diploma? Thanks.
On main breaker are u testing the incoming our outgoing supply?
What code would you put on an eicr if you had a pfc of 8.4ka and the mcbs in the consumer unit where rated at 6ka ?
C1
In case of a fault it's going to be a fire..
Hi Gary, how is it gonna clear any faults or short circuits if the current is way below the 6KA or 33KA? I know these are breaking capacity, hence it gives safety to the installation or equipments but how is it gonna rectify the faults? thanks
Hi. The numbers stated are the maximum break capacity so can clear (handle) faults up to 6KA etc. Thanks for your comment Gaz 👍
The terminology is confusing it won't clear faults. (They'll be rectified physically) It has to be able to withstand them at maximum so by doing pssc and pfc we know the maximum then we simply look at the Icn of the fuse and we know it can close a circuit if a fault occurs. If for example he found 11ka pfc and only 6ka Icn if a fault occurs they may not isolate the supply.
Mark Dove its starting to make sense please can you add more to that?
Could you please explain to me why when we do a zs on a circuit on an mcb we get different readings when doing a 2 high and 2 low test? I don't understand why the readings are so different. And surely if you are getting a high test result on the 2 low setting you can put it on 2 high setting and get a much lower reading.
If you have any info on the megger high/low settings it would be much appreciated 👍
Earth Fault Loop Impedance Test - 3 Lead Low or 2 Lead High - Test Explained
ua-cam.com/video/OaWOCNMQkSI/v-deo.html
So how much current to flow for the RCD to trip? More than 6k amp?
brad Rhed 30mA
In the am2 do you need to do every circuit breakers or just the one
LIVE Testing on a 3 Phase Dis-Board - External Earth Fault Loop Impedance Ze, PEFC, PSCC AM2 & AM2S
ua-cam.com/video/IeWoLUIKuJw/v-deo.html
You left the main switch inside the consumer unit on, is this compulsory when doing the first test
Hi Gary, am struggling to understand this. Your main incoming fuse is rated at 100 amps but you’re mentioning KA. The same with the breaker, this is a 6 amp breaker but you’re now saying it’s 6KA? Can you explain further, please?
Hi. The breaking capacity is the amount of current under fault conditions the over current protective device (fuse) can handle... so commonly a 6 amp MCB can withstand fault currents up to 6000 amps (6KA). At this value and below the device can break the circuit.... over this value it can say cause a massive arc that leads to a fire or melt across the device and then not disconnect the circuit... all the best and thanks for commenting Gaz
So 6 amp is just for the overload protection?
The KA rating is for the short circuit protection?
On the loop switch there is a LL, what would that be used for.
Testing between phases.
I carry out this test with a similar tester . But I never changed the leads over( l-n& l-pe)would this have any effect on the test results ? Also , should the fault current reading between the tails be greater than the rating (eg 100amp)
Also haha ,,,,. Am I correct in saying that the fault conditions are what could occur between the fault happening and the main fuse blowing ?
Thanks.
Hi. No worries on the test leads. The fault current (PFC) at the tails can be up to 30kA the PFC rating of the 100amp cutout fuse is either on it or look in BS7671. It’s the fault current it can clear not the load current which as a rule of thumb is 1.5 Times it’s rated value so 100 amp fuse could carry up to 150 amps for a short period of time. Hope this helps GSH Electrical
Yes
GSH Electrical it’s one thing doing the simple test but another understanding it fully . Thanks
Yes. I hope my videos help in some small way. Thanks Gaz
How come some people use 3 Lead test for this? Does it make a difference? E.G probs on L,N&E doing the PFC test
Hi, just a quick one I’m slightly confused with this test and I’ve my am2 on Monday. What’s confusing me is I’ve seen/heard that you have to times your highest result by x2 and that’s your ipf your record down
Testing for External Earth Fault Loop Impedance (Ze) When You Have a Main Earthing Terminal (MET) ua-cam.com/video/nz3scSSg3ZU/v-deo.html
Live Testing AM2 & AM2S - External Earth Fault Loop Impedance Ze, PEFC, PSCC on a 3 Phase Dis-Board ua-cam.com/video/IeWoLUIKuJw/v-deo.html
Hope these help 👍🏻
Is the measurement of each individual circuit PSC recorded on the test sheet or is it the PSC on the side of the breaker? i.e. 6KA
Hi. The kA rating is either on the side or front of circuit breakers. The measurement is only done once above a (any) breaker as shown in the video as this will be the same reading (PFC) for all of them. Hope this help and all the best GSH Electrical
Sorry, what I meant was that in the box on the test sheet asking for the value of KA, do we wright in the value written on the side of the breaker, or the value we have measured? Cheers Andy
Hi. Yes the value on the device thanks Gaz
im using fluke 1652B will i select Zi loop Hi current or Zi loop no trip
thanks
High current
@@GSHElectrical wow man supper respond thank a lot. you guys are stars
That bending radius on the main swa... 😉
Looks like copex not swa
@@michaelboyes4948 Oh yeah, good point ha ha ha.
Hello Gary
at 1:42 where would i find this table? WR or Onsite?
GN3 Table 2.16 p91
Can anyone explain In a nutshell please what the connection is between Zs, PFC, PEFC & PSCC
Ohm's law
@@tomaustin8943 no as in like in terms of measurement and which ones u need to record on the EICR
@@zamanraja9531 so prospective fault current (ipf) is the highest of PEFC and PSCC. This is recorded in the nature of supply parameters. Zs ie (R1+R2) + Ze is recorded on the schedule of test results.
@@tomaustin8943 omdss u made it so simple thank you so much !!!
@@zamanraja9531 no bother ;)
Hi...wWhat do you have to say regarding these two comments I read on another channel...where the tester / instructor stated the fault currents wer 370 and 350 A for PFC PSCC
1. The breaking capacity of the main fuse will need to be lower than the PFC
The second commentor agreed.....
2.Exactly! How is it that having CBs of 6,000 A breaking capacity will protect a circuit with both earth fault and short circuit PSFC and PSCC of 370 A and 350A, respectively?! The whole purpose of a protective devise is to trip before a circuit or any relevant point of the electrical installation reaches its maxumum PSCC or PFC!!! If that installation has in place those protective devises then surely the PFC and the PSCC are higher than 6,000 A. I seriously suggest this video should be withdrawn. It represents a hazard in itself! It will certainly confuse the inexperienced student.
Your comment would be appreciated...
I think the commentors have mis-understood which part of BS7671 we are compairing...and this may need explaining...by someone somewhere.
.
Hi. Thanks for the detailed message. The information you have provided me is worrying but I haven’t seen the video yet. I am not sure how you can go about having a UA-cam video removed it maybe worth highlighting these points to the channel that produced the video. Many thanks for your time GSH Electrical
The video seems fine as he did the same as yourself tested the board to ensure the fuses/circuit breakers were able to withstand the potential fault currents. It was the commentators who had it wrong....but they did raise an interesting point...in that you would expect the fuse or circuit breaker to trip with the lowest fault current...in order to save the installation.....seems odd to have a large fault current circulating and the prospective faults becomming actual faults and no breaker has tripped....was their slant on things, confusing the actual tripping current eg, 30mA or 150mA, of the device with it's actual handling capacity.
Hi. Thanks for coming back it’s lovely to see your taking things so seriously. Keep watching and asking your questions GSH Electrical
Mate i love your videos but why are your arms sticking out? you been making those gains at the gym? :D
At 4.48 that was dangerous, you almost touch the live main incoming, main cut off switch is also on
Becareful, love your videos keep it up
who wired that DB dear god
Learners have the conductors in and out of this board every day... I didn’t have time at 7am when shooting the video to sort them out. All the best Gaz
Hi Gary
Can I ask a question. Why have not locked off the main switch before taking the cover off and why do you need to do PFC test for each circuit rather than just at the input to the main switch. GN3 and both Napit/niece guides always show locked off powered down CUs whilst doing this test. If I had done this during assessment I would have been failed.
You will never get an answer from him because in this industry no one knows what to do . I had once two different assessment within couple of months and both assessors were saying something else.
Hard to understand
Hi. Sorry. Gaz
Why would you get a significantly higher Pfc L to PE vs L to N. Since you are testing a TNCS supply you would expect the same result since parallel paths are open to both tests through the MET. Or a slightly higher for Pfc might be expected for L to N, since the L tail is 25mm as opposed to 16mm earth tail. Also why test Pfc at top of breaker, as it cannot be higher than Pfc at main switch. This just encourages learners to follow a list of instructions with no awareness of what they are physically testing nor the meaning of what the results actually tell them.
It would have been much better if you shown where on the sheets you put the results.
Surely it's a bit dodgy having a Trade Skills for U advent just before a video by GSH Electrical???????
James Hansing that’s a youtube thing not a GSH thing
@@GSHElectrical Sorry yes, I didn't think it was you guys and I suppose UA-cam possibly can't tell certain advertisers they CAN'T have certain spots but it just seemed a little like letting a rival try to cash in on your hard work and success. Just seemed a bit of a "dick move" by UA-cam and indeed TS4U....