Why Does DC High Voltage Test Generate Negative Voltage?

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Discussion Overview

The discussion revolves around the behavior of DC high voltage test devices, specifically why they tend to generate negative voltage rather than positive voltage during insulation testing. The scope includes technical explanations and user experiences related to high voltage testing equipment.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions why DC high voltage test devices generate negative voltage instead of positive voltage.
  • Another participant explains that high voltage test supplies can generate voltage between two terminals, with one possibly grounded, leaving the other as active.
  • A participant describes their device as supplying negative voltage to the tested item while keeping the other terminal at zero volts, which is earthed.
  • Further inquiries are made about the function and specifications of the testing instrument.
  • One participant notes that for insulation testing, the polarity used does not significantly impact the results, suggesting that the choice of negative voltage may be arbitrary.

Areas of Agreement / Disagreement

Participants express differing views on the reasons behind the use of negative voltage in testing devices, with some suggesting arbitrary choices and others seeking a more definitive explanation. The discussion remains unresolved regarding the rationale for the negative voltage generation.

Contextual Notes

There are limitations in the discussion regarding the specific definitions of voltage polarity in testing contexts and the absence of detailed technical specifications for the devices mentioned.

moosya
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Hi every body
I've some question that need to be answered
WHy DC high voltage test devices always generate negative voltage rather than positive voltage
I hope that i can get an answer

Thanks
 
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High voltage test supplies generate a voltage between two output terminals and one of these might be grounded, or it might not. If it is, it leaves the other terminal as the active one.

I don't think there is any reason you would especially choose to ground the positive side of the supply. Power supplies for high voltage usually give you the option.

High voltage insulation testers are usually battery powered and have both outputs floating, so you can connect them whichever way you like.

Can you give an example of this type of test device?
 
my device supplies negative (-V) to the tested item and a zero volt to the Earth and this zero volt terminal is the earthing terminal of the test device
it does not provide +v and -v
I hope you understood what i mean
 
What is the function of your instrument?

What is it used for?

What voltage does it give?
 
my device is used to test the insulation of the electrical equipments by applying high voltage DC to the device and merasuring the leakage current to the earth
I observed that my device always injects negative votage instead of positive voltage with a zero volt on the other side of tested item (earthed)
I did not find any acceptable reson for this ?
 
For insulation testing it doesn't make any difference which polarity is used, so I guess someone just made an arbitrary decision.

Don't worry about it.
 
Ok thanks for clarification
 

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