How to connect modern household appliances to wiring without grounding: electrical safety lesson

"How to live without" land "?" - this is perhaps the main question for electricians over the past 20 years. People living in the old housing stock buy modern household appliances that are designed for wiring equipped with grounding, but they do not have one. What to do in this case? How to protect yourself from electric shock? Let's figure this out!

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In old houses and apartments, two wires are connected to the sockets: phase and zero. There is no cherished PE conductor (grounding). And if in a private house it is possible to make a ground loop, then in a separate apartment of a high-rise building it is absolutely impossible to construct a potential equalization system or throw "ground" onto a battery.

In this case, there is only one option in which you can protect yourself from electric shock from a device that is not connected to a PE conductor (ground). This connection is through an RCD (Residual Current Device). Connecting the device through an RCD is quite simple: phase and zero are connected to the upper terminals RCD, and two wires (phase, zero) also come out of the RCD to the outlet to which it will be connected electrical appliance.

Such a scheme will protect residents from electric shock. Example: if an insulation breakdown occurs in the washing machine, then when touched, there will be a slight electric shock - the RCD will instantly sense this leak and turn off the power to the electrical appliance. This is an effective measure of protection - there is no other way!

But what about paragraph 1.7.80 of the PUE?

The above paragraph says:

"If it is necessary to use an RCD to protect individual electrical receivers powered by the TN-C system, the protective The PE-conductor of the electrical receiver must be connected to the PEN-conductor of the circuit supplying the electrical receiver to the protective-switching apparatus ".

It is assumed here that you can take an additional wire, connect it to grounding electrical appliance and bring the RCD to the upper terminal N (zero). Such a system is perfect for a private house with old wiring, but it is unacceptable for an apartment in a high-rise building. Let's explain why.

If in an apartment building somewhere along the riser a zero conductor burns out, then on the RCD on top of the conductor N (terminal N), which is connected by an additional wire to the ground of the electrical appliance, will immediately appear voltage. Imagine that you are not at home and you have no idea about anything, and on the case of your washing machine, 80, 100 or 200 volts suddenly appear from nowhere. This is fraught with unpleasant consequences.

Or imagine another option: the electrician confused and reversed the phase and zero at the input to the apartment. Then, automatically, a voltage from pure 220 volts will appear on all cases of electrical appliances!

Conclusion

Clause 1.7.80 of the PUE (grounding connection through the upper terminal N of the RCD) is applicable exclusively for private housing, but is not suitable for apartments in high-rise buildings. To protect against electric shock in apartments, a simple electrical connection is used through a residual current device (RCD).

How did you solve this problem? Write your way in the comments!

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