Confused ...IR readings

[davesparks]

So due to the length off cable this can take longer to get the expected result while testing ?

Yes, which is why you continue the test until the reading stabilises or a suitable length of time has elapsed.
I have always used 2minutes for a 500V test.
I think modern higher voltage IR testers perform a timed test (amongst other functions) automatically.

 

[Dannyg8810]

Yes, which is why you continue the test until the reading stabilises or a suitable length of time has elapsed.
I have always used 2minutes for a 500V test.
I think modern higher voltage IR testers perform a timed test (amongst other functions) automatically.

From the socket I tested with the plug from the tester and got 365 and like I've said 135 from the board so wasn't making sense to me

But I now know where I've gone wrong thank you

 

[Toneyz]

It's the same give or take between all conductors ,would the reading of 135 be considered acceptable on a new installation cert? So for so many questions I'm fairly new to testing so these results threw me a bit and just filling cert out now

The good thing is as you say you're fairly new to testing you are questioning the values you get'' is this right, should I be getting this reading ,why have I got this reading.

 

[Dannyg8810]

The good thing is as you say you're fairly new to testing you are questioning the values you get'' is this right, should I be getting this reading ,why have I got this reading.

Yes always learning and being making sure everything I do is correct ,

 

[soms]

So you are testing this with the conductors at both ends free and nothing connected although strictly speaking the cpc should be connected to earth.

This is interesting, I wasn't previously aware of this. There is no explicit mention of it in the OSG, which many trainees/apprentices use as their quick reference/refresher to the testing procedures.
Looking into it, I see it is explained in GN3 as being introduced with the 17th Edition referring reg. 612.3.1.

Don't forget to safely discharge the stored energy in the cable.

Out of curiosity, how would this be done?

 

[Octopus]

^^ you should always do IR tests on a cable with the cpc connected to the cu, along with the other circuits.....

 

[Hellmooth]

If you carry out IR testing like that then you have to expect to get readings like this on long cables.
The cable forms a capacitor and you need to apply the test voltage for long enough to fully charge this capacitor, otherwise you will not be measuring the resistance of the insulation but will just get a slightly random number.

re-test the cable, but this time make sure you allow long enough to overcome the effect of the capacitance of the cable.

Don't forget to safely discharge the stored energy in the cable.

Is this why my Megger will give a low reading when button is first pressed but increases pretty rapidly as button is held down?