How to modify an RCD to a voltage monitoring relay using a couple of parts

Hello dear guests and subscribers of my channel. Today I want to talk with you about the possibility of modifying a standard RCD with just a couple of additional (and very cheap) parts, and output to obtain a combined device that will not only control the leakage current, but also protect your network from surges voltage.

Interesting? Then let's get started.

What do we need to upgrade

So, in order to modernize a standard RCD, we only need a couple of details:

1. Varistor rated for 275 volts. The voltage value of 275 Volts indicates that as soon as the voltage reaches this value, the varistor will lose its internal resistance and current will flow through it.
2. Resistance 10 kOhm, rated for 10 watts of power dissipation.

Yes, this is all that is required to finalize our RCD.

We turn the RCD into a voltage surge protection relay

So, now you can proceed to the direct alteration. To do this, simply connect our resistance and varistor into a series circuit using soldering.

Now we just add the created chain in this way: we connect one end to the "L" output of the RCD, and the other to the "N" input of the RCD.

That's it, the modernization is complete.

Note. I want to immediately clarify that this modification does not in any way affect the normal operation of the RCD, since we do not touch on the internal circuit and logic of work.

How it all works

So, the revision has been made, it's time to understand how it all works. In fact, everything is extremely simple and let's start with an RCD:

The principle of operation of the RCD is concluded in the constant monitoring of the leakage current. And this means, as soon as the insulation is damaged on the protected line and a leakage current occurs, exceeding the pickup setting on the relay, almost instantaneous disconnection of the protected section of the chain.

So, our revision creates an artificial leakage current, but only if the voltage in the network exceeds the threshold of 275 Volts. It is at this moment that the varistor will lose its resistance and a current will flow through the 10 kΩ resistance, which will be approximately equal to 30 mA in magnitude.

The RCD will take the flowing current for the leakage current and a trip will occur. Thus, the RCD will perform the function of a voltage relay.

Conclusion

I understand that dear sirs experts will be categorically against such "arbitrariness" and it is better not to engage in inventions, and purchase a full-fledged voltage relay (by the way, a review of a fairly high-quality Chinese voltage relay I did in this material).

But as one of the options for getting out of the situation when there is no way to supply (purchase) the launch vehicle, such a revision has the right to life.