I continue the series of articles on the correct electrician, increasing our professionalism and improving our knowledge together. And today I will tell you how to do it right use a differential current device (UDT) (which, by the way, is not correctly called an RCD - I will write a separate article about this) in electrical installations of individual residential buildings and apartments.
As I wrote in my last thorough article about how to color-code conductors correctly - we, as professional electricians and even just home craftsmen who are going to get into an electrician, are obliged to read the modern regulatory documentation and interpret it correctly.
Unfortunately, PUE 7, to which many refer and I, until recently, too, in many ways DO NOT suitable, since it contains quite a few gross errors that were thoughtlessly rewritten from obsolete GOSTs. We are not to blame that the people of the sovereign and those who are responsible for this have not yet put things in order in the technical normative documentation?
Therefore, you need to keep up with the times and not wait until PUE 8 appears in 10 years. You need to speak the same terminological language now, as I will try to do it in the future. Well, let's get back to the stated topic of the article and get started.
Requirements for using UDT
Specifically, the requirements for the use of UDT in electrical installations of buildings are described in GOST R 50571.3-2009 (IEC 60364-4-41: 2005), which appeared instead of GOST P 50571.3-94 and GOST P 50571.8-94 (requirements for the use of UDTs of which, by the way, were rewritten with errors in PUE).
I will continue with general, but important information. As a rule, in electrical installations of buildings that correspond to the most common and modern types of earthing systems TN-S and TN-C-S, circuit breakers are used as a protection measure (AB).
IMPORTANT: And UDT are used when in electrical circuits, certain earth fault currents, and at the same time, AB cannot turn them off for a certain time, standardized by GOST R 50571.3 (in particular, table 41.1 of this standard).
This time is called "maximum off time".
What does this information give us? To make it easier to understand the table - for example - let's take an apartment or an individual house. System earthing type - TN-C-S. Rated AC voltage of line conductor U0 - 230 V.
Then we get that in electrical installations of individual residential buildings or apartments, in electrical circuits AFTER THE CIRCUIT BREAKER follows it is imperative to install an UDT if the circuit breaker used cannot cut off the earth fault current within 0.4 seconds.
It should be noted here that the maximum tripping time from table 41.1 should be applied in accordance with cl. 411.3.2.2 of IEC 60364-4-41: 2017 in the following cases:
What else useful does the standard tell us? GOST R 50571.3-2009?
Paragraph 411.3.3 (in relation to electrical installations inside a building) directly tells us:
After reading it, you can get the first important practical conclusion for us:
Now we open the original IEC 60364-4-41 on the basis of which R 50571.3-2009 was created. But we are opening not the 2005 edition, but 2017, when a number of important changes and additions were made.
For example, a new one was added paragraph 411.3.4which reads:
We get the second practical conclusion:
You ask a question - so in GOST 50571.3-2009, PUE 7 and so on - there is no such requirement. "Why else put UDT on lighting?" Right! This is not yet in this GOST. But it will definitely be, because the standards are constantly being revised and created on the basis of IEC standards. It just takes time.
In addition, putting UDT on the lighting circuit is justified, since quite often in living quarters, lamps are placed in the reach of their hands by ordinary people.
Therefore, start doing the right thing now according to the most progressive and modern requirements.
Conclusion: why is this article good? It puts an end to endless disputes - whether or not to install UDT for the final circuits of plug sockets and lighting in electrical installations of buildings of individual residential buildings and apartments. The answer is to put. And what kind of UDT to choose and how to do it - this will be the topic of a separate article.
P.S. If you like this format of articles (with evidence and rationale and my conclusions) - write in the comments so that I can see feedback from you.