I'm having a weird issue at my workplace where some industrial equipment is present.

Almost every time I leave my laptop (with grounded aluminum body) for a while and come back I will get a quite nasty static discharge from it.

Even if have touched metallic door handle seconds before, which I think would eliminate charge on my body.

So the question is: Can a ground leakage in other areas of the building generate a static charge on grounded metallic surfaces like my laptop?

Provided of course that they are powered by the same line.

  • 1
    \$\begingroup\$ A metallic door may not be grounded. \$\endgroup\$ – Andy aka Jan 24 '19 at 13:02
  • \$\begingroup\$ In my case, I know it is since it is physically connected to the building metal frame, whic is driven into ground. \$\endgroup\$ – Kristian Jan 24 '19 at 13:27
  • \$\begingroup\$ Are you sure that the laptop is grounded? Did you measure it? \$\endgroup\$ – CL. Jan 24 '19 at 13:29
  • \$\begingroup\$ Now I did :) Both laptops (which both have the issue) are dead short to ground via charger after getting through the anodization layer with multimeter. One via regulate DC jack charger and one via USB-C dock. \$\endgroup\$ – Kristian Jan 24 '19 at 13:47
  • \$\begingroup\$ Also, when measuring AC between neutral and ground of the outlet it shows around 700mV. I tested it with a cheap multimeter though, not sure about the impedance of the measuring circuit. \$\endgroup\$ – Kristian Jan 24 '19 at 13:55

It won't be a static charge. But if what you think is "ground" isn't really grounded at all, then stray voltages can build up. This might be up to half the supply voltage. The only way to tell is to measure the voltage to a known good ground, that you can confirm is really connected to the Earth. This might be a metal rod pushed into the soil outside the building.

Also bear in mind that if you are walking from the door to the laptop, you could be building up static then.

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