If there is no power at the socket, why does the multimeter read more than 20 volts?
This is induced electricity.
Impact: It will not affect ordinary equipment and can be left alone. It may cause component damage to particularly sophisticated equipment and needs to be isolated.
Reason: caused by mutual inductance with other electrically charged power cables laid parallel to each other
Power sockets are not powered, measured with a multimeter has more than 20 volts, this situation is generally due to poor contact with the fire wire of the AC power. This happened to the power socket in Mr Tony's house in our village some time ago.
Wiring of the power socket.
Mr Tony is a small farmer, a good farmer, but knows nothing about electricity. I measured the voltage at his home outlet with a multimeter and it was just over 30 volts. As a rule of thumb, a small voltage on an outlet that doesn't reach its rated value is usually a problem with the firewire contact. So I focused on checking the firewire in his house, looking and looking, and found that the screws of the air switch to connect the firewire were a little loose. Tony told me that the fire wire was about to fall out of the screw hole in the air switch last month, and he had stuffed that wire in himself. I tightened that screw with a screwdriver and measured the voltage at the outlet rising to 100V, and the LED on top of the outlet came on.
The LED above the socket lit up.
The screw was tightened and the voltage rose to 100V, but it didn't work yet. I proceeded to look and found electrical tape wrapped around one of the wires on the yard wall. Tony told me that last year a lot of mice climbed up this wire to steal food from the house in the backyard where the grain was stored and ate it, and then he plugged up the hole in that house, and probably the mice couldn't get in and got so annoyed that they chewed the wire off.
I looked at this 2.5 square aluminium wire interface has been seriously oxidised, so there must be a large contact resistance, which leads to the socket voltage does not reach 220 volts. So I cut the aluminium wire and reconnected it, and wrapped it in electrical tape, after which I measured the socket voltage at 220 volts.
