In the kitchen, there are 4 three wall sockets, which are measured normally with an electric pen, af

It should be the zero line that has poor contact until the wire is broken. Because the neutral wire is grounded exactly after it is broken, low-voltage devices such as plug-in lamps can generate an electrical reaction, but after connecting the electrical appliances, the current is too small to be used. You need to open these three sockets to see how they are connected, if it is a socket behind the current, or if there is a problem with the empty neutral node, you can tighten it.

If you can't see it, you need to find an electrician to troubleshoot. In other words, if the neutral wire is connected from socket A to socket B and then to socket C, then the problem must be with socket C or after socket C. Generally, there will be no problems with the line, and you can consider what other construction you have at home at the same time as the problem to determine where the fault point is.

You can only use an electric pen to measure whether the live wire has electricity, but when the zero line is broken you can't measure, it is recommended to use a multimeter to measure whether the socket has 220 volts mains, if there is, when the load is connected, as you said: after the load (electrical appliances) after the three wires are all out of power, then it must be the switch or which terminal has poor contact!

It should be the poor contact of the live wire, because the no-load electric pen measurement is normal, and the live wire will be out of power after receiving the load, indicating that there is a problem with the live wire, and the four phenomena are the same to indicate that the fault point is on the total incoming line of the four sockets, and this kind of fault should be connected to the load on the circuit, and then the electric pen can be measured along the direction of the circuit.

As you wish. It can be preliminarily determined that the wire contact joint is not tightened. Try using a screwdriver and tightening each contact point a little more.

I think it's still a place to connect, the contact is not good, you remove the socket to see it, if not, that is, the wire has a joint, poor contact, you open the socket to see how many wires there are in the socket 3 6 or 9, 3 don't need to look at the main look at the 6 9 is not connected with pliers and then tighten the point, according to the requirements of the connector to tin,

Check the connection of the empty opening! Don't try it out yet! Check whether there is any error in the access position of the plugged internal fire and neutral line! Check if the neutral line is broken!

If the leakage switch does not jump when using electricity, the item wire is not connected incorrectly. Indirect line points in the inspection may be untrue. Now 80% of home improvement electricians are unqualified.

In your case, it's likely that the fireline is in poor contact.