It is not always possible to rely on the color of the insulation of conductors, for example, in old electrical wiring of houses of the last century, where special attention was not paid to the statutes of the PUE. And if the phase wire is determined quickly enough (with the help of an indicator screwdriver), then some difficulties may arise with zero and grounding.
Method one: just look at the markings
No matter how trite it is, but not all users may know the true meaning of various wire markings, hence all the problems arise.
The phase conductor is always marked with an aggressive color. It can be black, red, brown. Working "zero" - a wire without potential hazardous to life and health, must have a neutral color, and usually it is blue or blue. But the most noticeable color for the ground loop is yellow-green, the lines can be located both along and across the entire conductor.
If the installation was carried out by competent electricians, then there will be no problems to distinguish "zero" from "earth". Unfortunately, intelligent masters are not often found, so other indication methods have to be used.
Method two: a multimeter to help
You can determine the neutral and ground conductors using a multimeter and an indicator screwdriver. How to do it? Simple enough, namely:
1. Initial situation: there are 3 wires with incomprehensible insulation in a junction box, socket or switchboard. First of all, using an indicator screwdriver, we determine the "phase". We transfer the multimeter to the AC voltage measurement mode.
2. We touch the phase wire with one probe of the multimeter, and with the other - any second conductor.
3. Without removing the probe from the "phase", we touch the third wire with the second probe.
4. The potential difference between the "phase" and the grounding conductor will always be less than between the phase and working zero.
Of course, this method is not very accurate, but nevertheless, with some dexterity, you can quickly determine where "zero" passes, and where is "earth". It is only necessary to accurately and scrupulously check the readings on the multimeter.
Method three: sequential disconnection of wires
This is probably the most "wooden", but still effective way.
Important! If you are going to perform the operations described below, you must turn off all electrical appliances. Do not just click the power button, but be sure to pull out the power cord from the outlet. Otherwise, the consequences for technology can be very sad.
First, we turn off all electrical appliances. Required. Then we go to the switchboard and carefully disconnect the neutral conductor from the zero bus. After that, you can safely go to the problem area, armed with a multimeter. There will be no potential difference between "zero" and "phase" - the multimeter will show the value "0". But between the phase conductor and "ground" voltage will remain, but very insignificant.
It should be remembered that when applying this method in practice, in no case should you forget about your own safety and disconnect the "zero" from the common bus only with protective gloves, and best of all by moving the input switch to the position "Off"