3 Phase Ze and PFC measurement. Prospective fault current and test sheet input .

A look at three phase prospective fault current measurement and Ze.
Note: check earlier comments, nylon top hat washers/spacers in place on switch fuse. Its not bushed through with continuity on the metal work. Should have made clear (did in 1st take but camera was on a tripod and I got in the way, my bad!)
Will show in next video to prove this isnt BS. Very good spot by a couple of people so far! Thanks for paying attention and watching, I really appreciate it!
Note: Never disconnect any Earths without first isolating the Installation.
Using the TIS mft pro and GS38 leads.
L L measurement and calculated.
Credit Gary Hayers for the inspiration to record this video.

[@electrician247]

See next video for explanation of why I did measure Ze. Sorry for any confusion

[@GSHElectrical]

What a fantastic video Mark - keep up the great work 🦾

[@RedaReda-uk9lm]

Well done Mark, I am learning from your videos.👍

[@alunstone]

Unusual to see such low Ze reading,that transformer must be almost next door. Interesting video,thanks for uploading

[@electrician247]

Literally outside my door!

[@effervescence5664]

I have a site that has a Ze of 0.00, again due to the Trany being right outside the door for the entire industrial site. Tend to find unusually low readings (considered from a domestic pov) any time you get into really large commercial/industrial sites.

[@alunstone]

@@effervescence5664 That is low,never heard of that before,very high fault current on that.

[@ef7480]

Clear and concise. Better than most . (omitting the ones I haven't seen of course)

[@TechOne7671]

Good video mate, and explanation of real life conditions. The building I work in has a 2MVA 11kv-415 dry transformer at one end of the switchboard. Measuring Ze at the switchboard is almost zero as the tx is only 5 metres away connected by massive copper bars. All outgoing circuits are BS88 switchfuses and all control and monitoring circuits are also protected by BS88 fuses. However as you move further down the distribution system in the building, the Zdb readings become more normal.

[@electrician247]

Yeah soon as you get a bit of cable on the install it drops to sensible values. Thanks for watching mate. Appreciate it

[@lammy2304]

Great vids Mark.... Getting geared up for starting my own business next year and just bought a kewtech - wish I’d got the tis now it looks a great meter. 👍👍

[@electrician247]

Thanks for the kind comment. Appreciate it. Always daunting demonstrating stuff. Especially when I am not a teacher! But a few people have asked to see stuff like this. Glad you enjoyed it

[@lammy2304]

@@electrician247 you’re doing a fantastic job, and with the podcasts. Good to see someone doing a bit more commercial stuff with knowledge/ competence - especially for the apprentices out there. 👏👏

[@antonwillis896]

Hi mark, I’ve my am2 on Monday and I’m slightly confused if I need to double my highest result or not. In my pre am2 I’m sure they didn’t mention anything about doubling my highest result

[@electrician247]

Double the single phase measurement for 3 pfc psc is a rule of thumb that airs on the side of caution. Most centres have 3 phase meters I think. Best to check with the centre and your tutor if you can.

[@ef7480]

Also,the square root of 3 is 1.73 so doubling the figure creates a higher kA and allows a little more headroom..

[@sean1325]

Hi is the neutral one you do before the end the PSCC?

[@clark1e1]

If downstream breakers were rated for example 6ka and you got a PFC of 10ka how does a BS88 say at 16ka protect the downstream breakers? Surely if the fault is on one of the downstream circuits and then has a short circuit fault it could be exposed to higher amount of amps than its rated until the main BS88 fuse trips? Just trying to get my head around this bit from Guidance notes 3

[@electrician247]

Hi, the PFC, PSC usually drops away drastically as you move into an installation. But if you had 10kA at a 6kA mcb it would toast it. The upfront BS88 would then operate to protect the installation under short circuit faults. Thats why its vital we ensure PFC PSC does not exceed breaking capacity of protective devices in any part of the installation. We check that value at each sub distribution board to verify what is installed. Hope that helps.

[@clark1e1]

@@electrician247 Thanks very much for the reply! I agree with you and that's what it states on page 72 in GN3 paragraph 6. Its just further down the page it contradicts itself and states If the service cut out is a BS88 then all other overcurrent devices in the consumer unit can be taken to be rated at 16ka.

[@electrician247]

@@clark1e1 yes, this is the approach with CUs in domestic premises. Bit of a fudge really but rarely an issue as PSC PFC generally much lower when measured.

[@clark1e1]

@@electrician247 Thanks very much for your help. I struggle when the guidance tells me it must be one thing then the next paragraph tells its ok if we fudge it 😂

[@adammccabe531]

Loving the vids keep up the good work. just a point tho when you was doing your Ze you removed the out going cpc however the switch fuse and DB are bush and coupled together so wouldn't you pick up a reading from your outgoing cpc conductors through the metel work not nit picking just a observation

[@electrician247]

I knew someone would pick up on this! The switch fuse has paxolin/nylon spacers top and bottom of the Switch fuse entry. Should have made clear in the video which I noticed on editing. Still its all learning curve video content for me. Watch out for the next video and I will show you what I mean! Its covered in that one with some phase loading measurements. Its like it on every unit in the block and to be honest I am not sure why really lol. Must be a reason!? I should definitely have made it clear and I realised just that at the editing stage but this was the 3rd take after the first run of video I stood in the way all the time, 2nd run my audio was off so went with this! Good spot tho and thanks for watching!

[@adammccabe531]

Ok thanks for the reply looking forward to the next one then. Like you say it's all a leaning curve for all of us

[@electrician247]

@@adammccabe531 it sure is. Trying to check my content as best I can but also concious of keeping it real and authentic. Got one coming looking at phase imbalance. That coupled connection caught me out at first as I expected to find continuity between the DB and isolator earth blocks with cabling disconnected. Head scratching until I saw the spacers/washers. I think they are nylon, like top hat washers. Funny what you find on installs isnt it. Glad you are enjoying the videos. Any content you might like to see, let me know!

[@adammccabe531]

Thanks for the update vid. Never seen that before and this is my 26th year on the tools #everydaysaschoolday

[@electrician247]

Never ever seen it myself. All 18 units here have it. 23rd year for me!

[@mathman0101]

Your getting better take some advice from Nick and Jordan about what works best in a small space a wide angle mountable set up initially which you can hook off and on when you want to get in closer. You’ll be a real pro soon.

[@electrician247]

Yes 100%. First shoot I did a great chat through then watched back and realised I was stood in the way of the entire thing! Its hard.

[@pault4793]

That is not quite a correct ZE , What you did is actually a Z db as when you disconnected the earth to the main board you still had the switchfuse coupled with a bush & coupler to the main dist board therefore you still have the cpc's connected giving parallel paths, you should of disconnected the main earth from the 3 phase cutout at the switchfuse , apologies if i have seen something else or not noticed something

[@electrician247]

Hey Paul check an earlier comment. I can see why you think that but the switch fuse has top hat nylon washers/spacers. Good spot though! It had me scratching my head when I didnt get continuity on the earth bars lol. Its the same in every unit in the block. Not sure why really. I did cover it in my first take of the video but was stood in the way so reshoot it all and forgot to mention it! My bad as it could be more clear. This was take 3 so I ran with it afyer realising during editing. It shows what I am talking about in my next video hopefully so you can see I am not talking BS. Good spot though!

[@electrician247]

See latest video, need to get better at explaining things consistently and not ballsing up recordings etc. Its difficult but I am trying kzbin.info/www/bejne/qKrKpIdvoaZ4oMk

[@alexdougherty4905]

@@electrician247 mate you are doing awesome stuff, please keep the videos coming👍

[@electrician247]

@@alexdougherty4905 thanks Alex. Made my day mate. Appreciated