Finally, I was able to check what currents the power cable with a cross section of "one and a half square" can withstand.
This is very important knowledge for understanding where it is permissible to use such a cable and what machines it needs to be protected.
In my apartment, 1.5 mm² cables are laid to all the sockets, protected by a 16A machine, and I always wanted to understand how permissible this is.
Almost all electricians adhere to the rule "a 1.5 mm² cable is only suitable for light, and 2.5 mm² must be laid for sockets".
Advanced electricians say that a 1.5 mm² cable must be protected with 10A machines, and a 2.5 mm² cable with 16A machines, arguing this by the fact that any circuit breaker with characteristic "C" can withstand a current 1.45 times higher than the nominal up to an hour.
There is still a bike saying that they started laying 2.5 mm² on the sockets when the entire cable was "fake", made according to TU, and its real cross-section was significantly less than the nominal.
I am sure that none of these electricians have ever checked the real characteristics of the cable and cannot clearly say what will happen to a 1.5 mm² cable if a current of 24A flows through it for an hour. And I checked it.
Electricians proceed from the figures given in GOST in the PUE.
GOST 31996-2012 "Power cables with plastic insulation ..." contains table 19 "Permissible current loads of cables with copper conductors insulated from PVC compounds and polymer compositions that do not contain halogens ".
According to this table, the permissible current for the VVG 3x1.5 cable when laid in air is 21A.
In PUE 7 (Electrical Installation Rules. Edition 7) yes table 1.3.4 "Permissible continuous current for wires and cords with rubber and polyvinyl chloride insulation with copper conductors."
The VVG 3x1.5 cable is correctly considered a two-core cable, since only two of its cores carry current in operating mode. According to the table, such a cable can withstand 23A when laid open and 18A when laid in a pipe.
For the experiment, I connected a VVG 3x1.5 GOST Alfakabel (https://ammo1.livejournal.com/1148518.html) six fan heaters, each of which provided a load of 4 or 8 amperes.
We warm the street. :)
A power meter was used to control and measure the current. Atorch AT3010.
The cable loop was passed through a piece of corrugated pipe.
Three thermocouples were fixed on the cable (one on the cable sheath, the second directly on the core, the third in the pipe between the two cables), connected to the thermometers GM1312 and TM-902C.
First, I loaded the cable with 16A.
After 30 minutes, the temperature stabilized: on the surface of the cable sheath 34 °, on the core 33 °, in a corrugated pipe with two cable sections under a load of 42 °.
The second experiment is 24A. This is the current that can pass through the cable until the 16A machine turns off (remember, it may not turn off for an hour if it exceeds 1.45x, that is, up to 23.2A).
After 5 minutes, the temperature in the corrugation reached 60 °, after 20 minutes it stabilized at 67 ° and remained the same after 30 minutes. The temperatures on the cable lying in air were 49 ° and 46 °.
The third experiment is 31.3A. This is a current that should definitely not be run through a 1.5 mm² cable. :)
After three minutes, the corrugation was 64 °, after 5 minutes 80 °, after 10 minutes 97 °, after 15 minutes 104 °, after 20 minutes 105 ° and the temperature stabilized - after 30 minutes there were still the same 105 ° in the corrugation, 82 ° on the surface of the cable lying in the air, 68 ° on the core.
Table 18 of the same GOST 31996-2012 the permissible heating temperatures of the conductors of the cables are indicated.
The temperature of 70 ° is considered to be permissible for a long time, the maximum temperature is 160 °.
For myself, I can conclude that 16A is an easy mode for a 1.5 mm² cable, in which it almost does not heat up. 24A heavy, but quite working mode. 31A is an extreme mode in which nothing bad happens to the cable (it does not melt, does not burn, but of course it should not work in this mode). It turns out that a 1.5 mm² cable can be protected with a 16A circuit breaker with a "C" characteristic (but "B" is better, of course, so that it turns off faster under increased load).
As far as possible, I filmed the experiment.
https://www.youtube.com/watch? v = v_JfqFwNBCU
I just conducted an experiment and am not going to argue with electricians, PUE and GOST. I drew important conclusions from this experiment, and you draw conclusions yourself.
© 2020, Alexey Nadezhin
The main topic of my blog is technology in human life. I write reviews, share experiences, talk about all sorts of interesting things. My second project - lamptest.ru. I test LED bulbs and help figure out which ones are good and which are not so good.