Wire testing, OK or not - Page 1
Forum section: electronics / beginners

author: IvoS
author_rank: Frequent Contributor
timestamp: September 24, 2019, 10:42:13 pm
content: A friend of mine who is an electrician told me that he tests all circuits with high voltage of 10kV.He does that to check if the wire was nicked or somehow damaged during construction before they start closing the walls.A typical Romex 12-14AWG wire used for wiring the house has insulation voltage rating of 600V. Is it OK to stress the insulation on the wire with 10kV?

author: ataradov
author_rank: Super Contributor
timestamp: September 24, 2019, 11:06:39 pm
content: It is fine, but probably pointless. What exactly are they looking for in that test? And what is the source of that 10 kV voltage?

author: IvoS
author_rank: Frequent Contributor
timestamp: September 24, 2019, 11:16:43 pm
content: primarily looking for insulation integrity, if the wire was cut or the insulation is somehow compromised

author: ataradov
author_rank: Super Contributor
timestamp: September 24, 2019, 11:18:47 pm
content: Yes, but what is observed/expected when the voltage is applied? Do they apply high voltage and run around looking for discharge/sparks?

author: ataradov
author_rank: Super Contributor
timestamp: September 24, 2019, 11:24:38 pm
content: This also assumes that there is only wiring and no other devices including RCDs and may be even light switches. Otherwise you are just asking for trouble.

author: Monkeh
author_rank: Super Contributor
timestamp: September 24, 2019, 11:43:06 pm
content: 10kV is nonsense.1kV and below, yes, insulation resistance testing is normal. Well, in some places..

author: vk6zgo
author_rank: Super Contributor
timestamp: September 25, 2019, 12:32:17 am
content: Maybe some "Meggers" can produce 10kV, although the highest I've seen is 1kV.Years ago,we had a thing called a "Trimax Ionisation Tester" at several of my employers.From memory, it could test at up to about 25kV, but like a Megger, it couldn't produce dangerous or damaging current levels.Perhaps something similar?

author: tkamiya
author_rank: Super Contributor
timestamp: September 25, 2019, 01:00:10 am
content: I was professionally trained as electrician in Japan.Back then, Megger was a hand crank type. They easily put out few KV but very little current. Even if there is a huge nick and short, current was so low, it did not cause any (additional) damage. Cable damage can happen by accident (putting nail through, scrapes, or rats chewing on insulation). Megger will let you know the cable has leak. Again, current was low enough that it didn't cause any damage.Of course, if you have any electronics plugged in, it would be advisable to unplug them.

author: MosherIV
author_rank: Super Contributor
timestamp: September 25, 2019, 06:44:09 am
content: HiWe have an insulation tester called a Voltage Withstand Tester at work. It tests up to 6KV.Technically, you only need to run a voltage withstand test once on a product to proove/validate a new product's specifications.Does it damage the insulation?Depends on the nature of the insulation breakdown.If the breakdown results in an arc that leaves behind conductive resdue then, yes the insulation has been compromised and damaged.It is possible to have a breakdown where the hv finds a leakage path and does little/no damage.Each time you run a voltage withstand test, it does stress the insulation.