What could be causing electric current on my laptop case?

[berkeman]

'L' stands for 'Live'

Well, "Live" and "Line" basically mean the same thing.

 

[Wrichik Basu]

With the charger unplugged from the wall, what do you get for the resistance from each of the 3 pins of the plug to the outer and inner barrels of that charger?

My multimeter shows 0.L when the two leads are separated, so that means open circuit, or infinite resistance. Keeping that in mind,

​

Terminal 1 (in plug)​	Terminal 2 (barrel in DC jack)​	Value (in Ω)​
Live​	Outer​	∞​
Neutral​	Outer​	∞​
Earth​	Outer​	1.011k​
Live​	Inner​	∞​
Neutral​	Inner​	∞​
Earth​	Inner​	2.093k​

the tester has several lights on it that can pinpoint exactly which wires aren't wired correctly.

Okay then, I will buy one.

No, ~45V between Earth and neutral means a faulty or overloaded neutral path anywhere in the system.

Okay, that explains it.

The cause could be a connection that has become unreliable, a new load that has been attached or a fault in your ACU. If your neutral bonding is shared with another home or homes (illegal in many areas) the fault may be nothing to do with you

In that case, our "regular" electrician won't be able to find the fault perhaps, and I have to call the power supply company. This just got a lot complicated.

 

[Wrichik Basu]

Ideally, in order to protect against this you should install a Residual Current Device(s): in fact Wikipedia suggests that in India you should already have this.

Nope, we don't have a RCCB. Our main circuit breaker is a simple 20A fuse. It was supposed to be replaced by a 64A C-curve DP MCB last year, but then lockdown started and the work hasn't been done.

 

[pbuk]

In that case, our "regular" electrician won't be able to find the fault perhaps, and I have to call the power supply company. This just got a lot complicated.

Perhaps, although the fact that your ACU which I'd guess draws about 10A accounts for about half the neutral return voltage indicates that the problem is fairly local.