Do YOU Know What Happens to a Circuits Insulation Resistance When the Circuit Length is Increased?
ฝัง
- เผยแพร่เมื่อ 9 มิ.ย. 2024
- In this video I explain what happens to the overall insulation resistance of a circuit when the circuit length is increased. Often on site we test 3 time a single phase circuits for insulation resistance between line and CPC, neutral and CPC and between live conductors (line and neutral). However currently BS 7671 model forms only have 2 boxes for insulation resistance LIVE - LIVE and LIVE - EARTH and in this video I explain why testing LIVE conductor to EARTH is a more onerous test on the circuit and how the length of the conductors will have an impact on the circuits insulation resistance.
🔵 Do you Know Which Conductors Need to be Connected During the Insulation Resistance Test? • Do you Know Which Cond...
🔵 Insulation Resistance Test (Includes Line and Neutral Together to Earth and Between Live Conductors) • Insulation Resistance ...
🔵 Combined Insulation Resistance Test Line and Neutral Together to Earth & Between Live Conductors • Combined Insulation Re...
🕐 Time Stamps - Cut to the action 🕕
00:00 - Insulation resistance and circuit length
00:40 - Circuit conductors
01:48 - Very high value of insulation resistance
02:28 - Adding length
03:00 - Resisters in parallel
04:18 - What are we looking for
05:53 - Linking live conductors
07:45 - Earth metal work
10:40 - Bonding in place
10:42 Connection to the source earth
Videos are training aids for City and Guilds (C and G) and EAL courses Level 1, 2, 3 plus AM2, AM2S and AM2E.
You can follow me day by day on Facebook, Instagram, Twitter and TikTok lookout for "GSH Electrical.
▶️ FACEBOOK / gshelectrical
▶️ INSTAGRAM / brihzmraygdtmjmdb9lunq...
▶️ TWITTER / gsh_electrical
▶️ TikTok vm.tiktok.com/ZMRBLFdhe/
#GSHElectrical #Electricaltrainingvideos #electricaltesting
Still a bit confused, but I know more than I did 12 minutes ago. Thanks.
Useful as always. Been watching for a few years now and the knowledge is spot on. Thank you Gaz and team!
Thanks MMG 👍🏻
Absolutely brilliant gaz 🙌🏻🙌🏻 as an adult learner your videos are helping me out so much, thanks gaz 👍👍
Thanks for watching and the great comment 😊👍🏻
Great video mate have a wonderful Sunday
Very good video I appreciate the education you give.
Thanks. Great video with an easy to understand tutorial.
Thanks Bryan
Another great video
Thanks 👍🏻
Thank you very much.. Clear and logical presentation.. excellent channel.. !
Thanks for the kind words 👍🏻
Good video combining theory and practical 👍.
Amazing videos really appreciate it.
Thanks for watching and the feedback 👍🏻
Yet another in a brilliant range of videos; always interesting, always enlightening.
Could I just ask: would it not be better in the real world and in an older property to test the insulation with the cpc disconnected at the consumer unit, so that only the cable is tested (hopefully); and then test with the cpc reconnected to the busbar? Or vice versa of course.
When the insulation resistance is way below infinity (999m ohm) surely this would give a better indication of the system condition when insulation resistance is for example in the range of say 60m ohm!
Important to also test between live conductors of course.
Just to note, at a 1GΩ (Billion Ohms), you get a leakage of 240 nano amps
Just wondering how voltage drop would affect this over the longer distance increasing the voltage drop..
But then does the temp of the insulation also change the characteristics of the insulation.. Then there is the electrical conductivity of the copper when it is at the higher temp.. Causing more voltage drop? or less?
Hi, thanks for your helpful videos. On this one I’m struggling to see why the resistance when adding cable length is treated as parallel rather than series?
Line and CPC run parallel to each other.
@@paulmatthews5470 In this instance use of the word parallel has a specific meaning in electrical circuitry with no relationship to their proximity in a space running next to each other.
@@etdj909 never meant to be
Will a 500v insulation resistance test damage RCBOs?
Hi Gaz great video however im a bit confused i thought the longer the cable the greater the resistance and now your saying the less resistance or is it to do with the cables in parallel. Am i right in thinking the whole point of insulation resistance is to make sure the line neutral and earth are totally insulated from each other and that no current is leaking out of the insulation to cause a short or earth fault. Thank you for putting this video together much appreciated.
The details are in the video Angela maybe worth a second watch 👍🏻 thanks for commenting Gaz
Yes the longer the cable the higher the resistance of the CONDUCTORS But with insulation resistance we are measuring the resistance BETWEEN conductors not the resistance OF the conductors.
So the longer the conductors of which the resistance between them we are measuring, the lower that resistance will be as there is more area available for the electrons to jump from one conductor to the other.
Think about if you have a 1m hose with one puncture. That means when you turn on the tap you will have leakage (water drip from the puncture) of say 1lt per minute.
If you add to the end of that hose another 1m hose with the same size puncture then your total length of hose would be 2m with 1 puncture per 1m.
So that means that your leakage will double (water drips from now 2 identical holes) to 2lt per minute.
Meaning the insulation (which is the hose) between the water and the ground has halved as now twice the amount of water is dripping!
Is it the same logic for singles and SWA?
Yes
Fantastic explanation, but I am a bit confused , testing line and neutral combined to earth so long as the value is >1 meg ohm then what’s the problem after all we only test line and neutral combined to earth so as not to damage any sensitive electronic equipment that can’t be removed from circuit. Also we should be careful with this test as anyone who maybe touching any earthed metal work will be tested as well and they won’t be happy.
Brilliant video Gaz as always
👍👍👍👍❤️I do love waking up on a Sunday morning to a great electrical installation lesson from GHS , keeps my brain refreshed,
Well as long as they aren’t holding a live cable and a CPC then they aren’t completing a circuit.
@@paulmatthews5470 get your tester out and set for 500v IR and hold the test lead that that is plugged into the line jack and with out touching the other test lead press the test button, I bet you get a shock, remember the test voltage goes down the line and returns on the earth back to the tester , so it simple logic that on its return all earthed metal work including the kitchen sink will be tested and if someone just happens to be leaning on that sink they will be tested as well , and you can expect to be called a view choice names.
@@seandempsey7351 just tried it, never got a shock, BECAUSE I’M NOT COMPLETING THE CIRCUIT
Now, if I had been leaning on something earthed as well, I’d then get a shock. But standing here I’m fine.
@@paulmatthews5470 that’s what I said if someone is touching any earthed metal work such as a water or gas pipe even the kitchen sink when you press the test button they will get a shock. It won’t do them any harm but they will call you a view choice names. And as for the tester you will will get a shock from just the line probe but again at worst it’s a sharp tingling up your arm . I’ve done it not on purpose but a lack of concentration on my part . Also some people can hold both probes and fill nothing .
It does not stop there. Any place where the insulation is squashed the insulation will be thinner and reduced, at a socket , twisted cable or tight joist feed through, we are aware of this but how much can this reduce resistance value . I am sure there are other factors at work as well.
Clever instructor electrical installations
In practice, would the voltage drop be the main limiting factor in length as opposed to resistance, or are the the same thing in that resistance causes voltage drop?
Nail between phase and neutral and minimal leakage to earth
Got to love this shit, learn how to use a Megger ohm resistance meter
V equals I r squared
Fuse blows.... don't know why,,,,,, over current or earth fault....
Yeah but once again you are targeting house bashers - your logic/reasoning does not hold true for singles say!