[chbot] Insulation Tester

Volker Kuhlmann list57 at top.geek.nz
Sat Jan 30 22:40:37 GMT 2021

On Tue 26 Jan 2021 23:29:05 NZDT +1300, Mark Beckett wrote:

> 1. Capacitance will tend to show as a lower insulation resistance while it
> charges, hence why longer cables get a time.

Yes, it shows as increasing resistance over time, until it has charged

> My comment about comms cables was more that "just because you can, doesn't mean
> it's a good idea" as we are now finding out.

Yes, very annoying. What it the cables' rating and test specification
exactly? 1kV testing doesn't strike me as unreasonable for something
where spikes are probably regularly that high. Is it a quality issue
with longevity over the lifetime of the product?

I've seen a fig.8/IEC power cable easily break through the whole outer
insulation from bending it, from sitting on a shelf for a few years. It
had all the approvals marked and passed all tests when sold... If
offered for sale now, immediate fail and product recall.

I'm pretty sure e.g. landline telephone cables must meet mains
isolation, unless that has changed with all the free Chinese trade.

> 2. I've had something checked for Electrical safety and they certainly didn't
> do those tests, and I can't see why they would deliberately destroy and exceed
> every component rating to prove ???

Well, I've sent a device for testing to what is/was UL Labs
Christchurch, and that's exactly the test they said they did. It was a
few years back but I don't see why it would change. SMPS isolation is
(or should be) 1kV by design, mains to user touchable parts of
appliances likewise. It's for type approval, not individual testing.

In my opinion goods should meet safety standards and specifications not
just when sold, but until they stop being used; that includes testing to
specification at any time. I'm sure industry and manufacturers

> I'm not sure where the conductive path is when you ".. wrap the whole thing in
> tinfoil and earth that and put 1kv into all the connections".

Mains / telephone line voltage to user fingers. There shouldn't be a
conductive path! It's a system test, not a component test. Most
appliances are designed and approved for many markets, so NZ standards
are a good start but not enough on their own. I don't have a copy of
EN/ISO60950 either.


Volker Kuhlmann
http://volker.top.geek.nz/	Please do not CC list postings to me.

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