New to the forum and just recently retired.

AlfInAussieland · Aug 9, 2023

I finished my Electrical Fitter/Mechanic Apprenticeship in late 1998 as a mature age student while working at an Electrical Distributor across our state here in Australia.
Part of the practise was to work in each relevant section so: Streetlights/Underground Subdivisions/Service Truck/ Line work/Sub zone section/Communications etc.
While at the end of my apprenticeship I ended up doing my time in Communications and was asked if I wanted to stay in Communications due to my knowledge and abilities that I gained privately simply due to interest. The provision was that I had to finish my Electrical apprenticeship/qualification first before moving across and then start my Electronics/Communications apprenticeship.
As you can imagine this added another few years on my training before then being qualified in that area. 25+ years later I have retired and am upgrading the house we purchased a decade ago. When first moving in I found lots of dotchy work that I know wasn't done by the previous owners but by so called electricians ...you know the ones that do whole subdivisions of houses.
As we are about to comments on a very large solar/hybrid/battery/generator backup system upgrade, I need to do some preliminary work before the very reputable company and guys (I know some of them and their professional abilities)start their side of the job.
This requires some brushing up on the wiring rules and testing procedures.
Righ now I am checking up on Insulation testing regarding the safe testing at 500V with electronic equipment attached in the circuit.

James · Aug 9, 2023

Welcome to the forum.
what part of Australia are you from?

AlfInAussieland · Aug 9, 2023

East Coast, NSW, Mid North Coast

pc1966 · Aug 9, 2023

AlfInAussieland said:
Righ now I am checking up on Insulation testing regarding the safe testing at 500V with electronic equipment attached in the circuit.

Welcome to the forum!

Typically the risk for IR testing at 500V is when doing it between live wires (L to N, or L1 to L2, etc) as that can charge up small electronic power supplies far above the 330V or so peak of 230V AC causing damage. For this sort of test using 250V should be safe.

Testing 500V from L+N to E should be safe, as that sort of path is expected to not conduct under typical surge conditions, and is often necessary on inspection as often it is not practical to disconnect all loads (they would be L to N so ignored if L and N linked for the test).

However, if any equipment of power distribution blocks have SPD they will normally conduct at around 400V (higher than normal AC peak, lower than hopeful damage point) so show up as a low value (typically < 1M) at 500V but high (typically > 10M) at 250V. SPD are often linked from L-N and N-E (sometimes L-E and N-E) so there is a path to earth under normal conditions at sufficient voltage.

General advice is to test at 250V first and see if anything conducts, if so then going to 500V is pointless as you know it is not going to pass!

AlfInAussieland · Aug 9, 2023

pc1966 said:
Welcome to the forum!

Typically the risk for IR testing at 500V is when doing it between live wires (L to N, or L1 to L2, etc) as that can charge up small electronic power supplies far above the 330V or so peak of 230V AC causing damage. For this sort of test using 250V should be safe.

Testing 500V from L+N to E should be safe, as that sort of path is expected to not conduct under typical surge conditions, and is often necessary on inspection as often it is not practical to disconnect all loads (they would be L to N so ignored if L and N linked for the test).

However, if any equipment of power distribution blocks have SPD they will normally conduct at around 400V (higher than normal AC peak, lower than hopeful damage point) so show up as a low value (typically < 1M) at 500V but high (typically > 10M) at 250V. SPD are often linked from L-N and N-E (sometimes L-E and N-E) so there is a path to earth under normal conditions at sufficient voltage.

General advice is to test at 250V first and see if anything conducts, if so then going to 500V is pointless as you know it is not going to pass!

That is a very extensive reply, thank you.
I even had to look up the acronym "SPD". They are not a device used normally at consumer houses and even rarely used at your average commercial building.
I installed one at my previous house in the Main Switch board before the main switch. Not sure if it ever did anything.
We did use SPD's extensively in the old days on Phone Line MDF's/IDF's (not called that anymore either)
L1 to L2 testing ??..American ?? Our systems use the Star/Delta transformer configuration, so it's either Single or Three Phase. Or am I missing something here?....Been a while.

mainline · Aug 9, 2023

AlfInAussieland said:
That is a very extensive reply, thank you.
I even had to look up the acronym "SPD". They are not a device used normally at consumer houses and even rarely used at your average commercial building.
I installed one at my previous house in the Main Switch board before the main switch. Not sure if it ever did anything.
We did use SPD's extensively in the old days on Phone Line MDF's/IDF's (not called that anymore either)
L1 to L2 testing ??..American ?? Our systems use the Star/Delta transformer configuration, so it's either Single or Three Phase. Or am I missing something here?....Been a while.

L1 = phase 1, L2 = phase 2 etc

AlfInAussieland · Aug 9, 2023

mainline said:
L1 = phase 1, L2 = phase 2 etc

LOL....thanks. Now I get it..a bit slow tonight. Yes, testing between phases.

pc1966 · Aug 9, 2023

SPD have become a normal fitting here in the UK over the last 5 years or so, I guess since the 18th edition of the wiring regulations. Not quite mandatory, but generally expected for most installations and now you get the smaller SPD (single module so size like MCB, type 2 for induced surges rather than buildings with lightning protection systems, etc) at fairly low prices so not really an issue to fit them.

Hard to say how much benefit you get from having them though. In many areas of UK lightning surges are rare so not such a big deal, however, you can get surges from fault-clearing as well and given how much cost is invested in electronics these days it is hard to argue that £50 spent towards protection of £1,000-£10,000 of mains-connected electronics is not a good idea.