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Apparent voltage on plastic service head

Tolly

What are your thoughts on this please?

Using the TIS810 contact volt stick, you can see (no audio) that no voltage is indicated on the isolator, tails or meter, but there is (by flashing red and vibrating) on the plastic service head/fuse - the tester is supposed to activate at 50-600v. The relevant DNO came and tested it, and stated there's no more than 0.4v on the head (though I don't know about the tester they used). 

  • 0 in reply to Tolly

    interesting, it does seem rather  less sensitive with the cling film but not a conclusive go no-go  as the pen clearly sometimes will trigger with the known good insulator in the way.
    It really is not a lab instrument, and I'd not have much confidence in the 60volts figure - I suspect that there is considerable variation between units and that is a limit of the kind 'definitely always triggers at 60V or a bit below' rather than 'must exceed 60V for light to come  on'.
    mind you the DNO chap is not looking exactly scientific either. 
    Can I ask why this is being looked at ? - have problems been reported that indicate a leakage such as tingles and shocks or electrolysis ?

    this is all a bit odd and not conclusive.

    Mike.

  • 0

    A video showing how DNO operatives should use single pole contact voltage indicators as an aid for identifying issues, when carrying out safe isolation, PSCC, and Ze testing.

    youtu.be/z7han_twcnw

  • 0 in reply to Sparkingchip

    I see that at ~3:24 he proves live incomer with a test lamp first ;-)

    The problem that Father in Law had was that there was coupling between a true live and his isolated circuit (not sure what voltage he was working on) and that it was still capable of lighting a neon tester that was in use at the time. He needed the test lamp to show that there was no live power (this will have been before RCD leakage/shock protection being common).

    It's still a useful video though.

  • 0 in reply to Philip Oakley
    Philip Oakley said:
    I see that at ~3:24 he proves live incomer with a test lamp first ;-)

    A two pole tester shows there is a voltage difference between the probes, but not which probe actually has the highest voltage on it, it could be either of them.

  • 0 in reply to Philip Oakley
    Philip Oakley said:
    The problem that Father in Law had was that there was coupling between a true live and his isolated circuit (not sure what voltage he was working on) and that it was still capable of lighting a neon tester that was in use at the time.

    Which is why many voltage testers have a switchable load, to reduce the impedance of the tester,

    The high impedance load stops the RCD tripping, but creates ghost voltages.

    For example Fluke T-series testers provides single and double pole voltage indications and a switchable load, requiring two buttons to be pressed simultaneously.

    • Single-pole phase test offers fast identification of live conductors
    • With 4 ways to indicate the presence of voltage – LED indicator, LCD display, audible tone or tactile feedback, always know if hazardous voltage is present
    • Switchable load: avoid display of ghost voltages allowing you to draw more current from the circuit under test and avoid trip residual-current devices (RCDs)

    www.fluke.com/.../fluke-t150

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