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Why is the IT network layout not widely used?

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Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
  • #31 19555081
    Krzysztof Reszka
    Moderator of Electrical engineering
    AdamKurek wrote:
    Dividing people and forbidding, limiting them, saying in advance that it is not worth it that they will not understand anything is something like mental terror.

    You're wrong, buddy, no one is forbidding anyone, only bringing nonsense to the topic that may be harmful in initial teaching is forbidden in this forum. The electrode is not a box or a bricklayer where you will find such total nonsense that the fathers of electrics probably fall over in their graves. And the topic of IT electrical installation is a difficult topic because in our country and in the world few electricians meet with it on a daily basis. And unfortunately, literary knowledge is not huge in this area, the lack of standards or translations of the conduct during works unfortunately wreaks havoc on knowledge.
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  • #32 19555341
    AdamKurek
    Level 2  
    retrofood wrote:
    AdamKurek wrote:

    Apart from slander, there is probably nothing worse than denying others the right to share their learning, which is like censorship!


    You are already trying to set up others, although this is your first post on the forum. It's polite like that? Do you have a mirror at home? Take a look. Are you wandering into someone else's yard and doing your cleanup?


    Yes, this is my first post, which I was thinking about and I hesitated if I should interfere, having a fear of how it would be received (and also about being banned). However, despite many doubts (and risks), I decided to take this honestly honest (critical statement) because this topic is VERY important socially.

    It is especially as a new (and green in this) user that I stand here in defense of all those who are repressed and humiliated, "little", "stupid" as if "unworthy" (because more [b] [/ b] uninitiated). After all, it is for him (for us) such seemingly insignificant discussions that are valuable, important (often the only [b]) source of information [/ b].

    After all, a man does not become a birth specialist, he learns from ZERO often starting with this type of accidental interest .. and whether he is humiliated, rotated or at least embarrassed by the boasting "omniscient" "saints" is quite essential for his development and in the future, the development of the industry.

    Because if all old veterans closed up with their knowledge, not passing it on what would have happened in this (or a given country) if they had already died out (they would have fallen to the position of the third world in a given field, what not).

    Knowledge must be shared, because it is a very important social good for the general public.

    So with my criticism, I am not going to offend anyone, but to represent social good.
    For example, since when has this public forum become someone's private backyard? (I don't really understand the idea of narrowing down and appropriating forums through more established users).

    Because it begins to resemble a phenomenon that when someone reaches something (e.g. knowledge, specialization), it is typical, jealous or comparing to everyone, undervalued individuals .. he pushes everyone else down with his shoes so that they do not accidentally get higher . As a result, the whole society loses, because they are terribly negative, even toxic attitudes. Because people become infected with them, copying them subconsciously. That is, when they were humiliated by denying them the right to a given good, then when they achieve something with difficulty, they also repress others on the same basis, how they were suppressed, humiliated. It is a simple mechanism that acts, for example, as a wave in the army (victims of victims become torturers for others in the vicious cycle of violence).

    I am the one who breaks the pattern, saying aloud that something is wrong (that the king is naked). I know and understand this social problem clearly because on a daily basis I am much more passionate about it (than the neglected two decades of electrics / electronics - but designing and constructing various devices and systems are also my great passions, so I think that I am at home, even though it is my first post and I am a self taught (not doing it professionally - yet.. but since I've already talked, I will mention that I'm going to change it .. so I'll be a frequent visitor under this or other nicknames. Because I considered the option that if there is cronyism on this forum, such a typical circle of mutual adoration having nothing to do with honesty and reliability, which could ban me for offending the majesty of "inviolable saints" (in defense of the interests of the majority of ordinary users), then I can always to start over with a blank slate.

    However, if it was not possible, if we were already living in a digital world with one possible public identity, with one story without a chance to change it, I would not risk risking myself, not knowing the local customs, I would prefer not to be critical of the local "elites" (even like now, if I thought the thing was important enough to break convention by saying something unkind in greeting).

    I hope that whoever has the nickname "awareness" knows what improvement is and will take this remark as a practical hint
    (in order not to self-esteem at the expense of someone else's harm, to humiliate others and to deny them the right to know ...
    because maybe here it is common among VIPs that they think (you consider the forum as your property) by ruling over it excessively, so that disrespecting others and closing topics, discouraging discussions with greens is the norm?

    Because you are "at home" and what are the new "in your backyard" what - they are disturbing you ... or are they nervous because they are right away they don't know something ...

    However, it is worth giving people a chance to live in a better world, instead of closing themselves off from them by creating something like a sect.
    If you want, set aside a place only for yourself without disturbing the others I represent here having as much right to know as everyone else. Because it is a social, common good - like this forum (not someone else's property, to limit, narrow, push and suppress others .. suggesting that they are some kind of under people, just because they have NO qualifications and experience.

    It is about irrational pride that takes away reason and sensitivity, empathy. I just try to (as) discreetly remind that this forum is a common good and that the Greens have a right to it (so if someone asks about something and there is a discussion, ordinary personal culture requires respect for others and allow them to express themselves, and not to say that it is not worth it because it is a waste of time for fools or fools who will not understand anything anyway because what? Because knowledge is gained at the moment of birth through enlightenment?

    My point is that denying others knowledge, humiliating others creates the very problem of not knowing, i.e. stupidity.
    Forums are there for people to learn and develop during the discussion - it is like barbarism to confuse them.
    Because what bothers who, on a thread, the greens in a given topic ask seemingly stupid (for insiders) laundry?

    If someone does not like it, do not let them read, go on and let others develop at their own pace, teaching a little.
  • #33 19555479
    Krzysztof Reszka
    Moderator of Electrical engineering
    AdamKurek wrote:
    It is especially as new (and green in it)

    I don't know why but my nose tells me you're not new or green.
    AdamKurek wrote:
    I am the one who breaks the pattern, saying aloud that something is wrong (that the king is naked).

    I think you are wrong and your assessment is highly idealized in terms of the way we are perceived on the forum. You will never be humiliated or considered inferior just because you have a different opinion. It happens that we ask a person on a topic to verify his views because they are in conflict with practical and theoretical knowledge. But it often happens that the opponent does not understand the problem or does not want to understand it, and there is a conflict of interest between the forum and the user who expresses some views. Later we have the kind of resentment you are trying to make us now.
    AdamKurek wrote:
    My point is that denying others knowledge, humiliating others creates the very problem of not knowing, i.e. stupidity.

    Provide evidence of humiliation through the forum. Remember that the user is also a person like you and we have no direct influence on his evaluation of someone's posts.
    You accuse the forum of humiliation, and whether it is done by the forum and its functional members or users like you. And then you give us the label of humiliation.
  • #34 19676828
    kris8888
    Level 40  
    I will connect to the topic because for me the IT network system is still a mystery, at least from the point of view of protection against electric shock. As I understand it, in such a system, touching the L wire or N wire separately is not a threat because the power supply system is isolated from the ground. Only the simultaneous touching of the L and N conductors will close the circuit and cause electric shock.
    Now let's assume that we have two devices in metal housings, in a common room, and in one of them there is a metallic puncture of the L conductor to the housing. It still does not pose a threat to the user (as long as he does not accidentally touch the housing of this device and the N cable at the same time). Why only the puncture of the L wire into the housing of the second device could be a lethal threat? In my opinion, how would it have to be a puncture of the N wire to the housing in the second device so that there would be a risk of electric shock while touching the housings of both devices.
    And most importantly, I assume that both devices are turned off, no current flows through them. I know that turning on any of these devices would close the electric shock circuit by the device that is turned on.
    The IT system reminds me a bit of a power supply through an isolation transformer, and the grounding of the receivers on the receiving side is only intended to detect by the appropriate systems the fact that the working wires are punctured to the device housing.
    Am I okay or is there any mistake?
  • #35 19677300
    Wirnick
    Level 30  
    kris8888 wrote:
    Am I okay or is there any mistake?

    You do well
    However, the issue of basic protection [protection against direct contact] has crept in. Can you explain how to touch the working wires without destroying the protection?
    kris8888 wrote:
    Now let's assume that we have two devices in metal housings, in a common room, and in one of them there is a metallic puncture of the L conductor to the housing.

    Why, when the devices were commissioned, the enclosures were not grounded? Effective grounding gives ground potential to L and it is still safe to touch the enclosures [zero potential difference].
  • #36 19677349
    kris8888
    Level 40  
    Wirnick wrote:
    Can you explain how to touch the working wires without destroying the protection?

    Yes, you are right, under normal circumstances it is impossible, the work hoses are not available. I have given a purely theoretical case in which paralysis would occur.
    Wirnick wrote:

    kris8888 wrote:
    Now let's assume that we have two devices in metal housings, in a common room, and in one of them there is a metallic puncture of the L conductor to the housing.

    Why, when the devices were commissioned, the enclosures were not grounded? Effective grounding gives ground potential to L and it is still safe to touch the enclosures [zero potential difference].

    By default, even these enclosures should be grounded in the IT network system. Therefore, the more I do not understand why a dangerous situation for the user arises only when the L conductor is punctured to the housing in the second device (in the IT network system). Device housings and ground should be at the same potential after all. And we assume that the user cannot touch the working wires by default.
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  • #37 19677467
    CYRUS2
    Level 43  
    kris8888 wrote:
    It still does not pose a threat to the user (as long as he does not accidentally touch the housing of this device and the N cable at the same time).
    It will not touch because the N conductor is not accessible.
    kris8888 wrote:
    Why only the puncture of the L wire into the housing of the second device could be a lethal threat?
    The second short circuit concerns the continuity of the power supply. Read Musiał texts - it shows the 2nd short circuit there.
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  • #38 19677532
    wojtek60
    Level 23  
    Maybe I am going to stir up the topic. Electric cars have an IT system for safety reasons.
    If such a vehicle is considered universality, IT is commonly used.
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  • #39 19677544
    kris8888
    Level 40  
    CYRUS2 wrote:
    The second short circuit concerns the continuity of the power supply. Read Musiał texts - it shows the 2nd short circuit there.

    I understand that you mean this text: http://www.edwardmusial.info/pliki/ochrona_it_tt_tn.pdf

    Except that it says there that the second earth fault (short-circuit of the working conductor to earth) would have to be on a different working conductor than the first. What I also assumed, and it is understandable, is when the short-circuit current reaches high values and the power must be turned off. But if the second ground fault is in the same working conductor as the first, then basically nothing is happening to the IT system except a slight increase in the leakage current.
    So such a general statement that a second ground fault in an IT system forces the power to be turned off is probably not always correct, certain conditions must be met.
    In total, I also wonder why IT systems are not commonly used. Because apart from possible costs and constant care that no working wires and the transformer's neutral point have a short-circuit or large leakage to the ground anywhere, I do not see any other problems. Well, the fact that the working conductors (other than PEN) cannot have a short circuit with the ground also applies to other network systems.
    As for the potential risk for the user in the event of a second ground fault in the IT system, I suggested (maybe incorrectly) with this earlier post, which I will tell you honestly, I also did not fully understand:

    zdzisiek1979 wrote:

    Consider the operating room.
    The surgeon takes the electric saw that is damaged. Saw damaged. The saw is on the table. The earthquake closes the floor table ... now the earthquake is handled is closed by the surgeon but still nothing. But if another fault occurs, the fault path will close between one fault and the other, i.e. the surgeon will be the conductor for the current that flows between one fault and the other.
  • #40 19677596
    Wirnick
    Level 30  
    kris8888 wrote:
    So such a general statement that a second ground fault in an IT system forces the power to be turned off is probably not always correct, certain conditions must be met.

    Until I drank my tea. 20 years of work in IT. I read the theory and eureka - the second earth fault is safe provided that the devices are covered by PE connections (protective conductor network)! Thanks kris !!! It's good that the fuses have tripped the voltage! UKSI and WATCH are just technical additions.

    Added after 22 [minutes]:

    wojtek60 wrote:
    Electric cars require the IT system for safety reasons.

    Indicate where the car installation point is connected to the ground ?. It is a battery system, not even separation (unless it is charging).
  • #41 19677659
    kkas12
    Level 43  
    kris8888 wrote:
    So such a general statement that a second ground fault in an IT system forces the power to be turned off is probably not always correct, certain conditions must be met.
    Where does this earth fault come from?
    Well, from the connection of the phase to the earthed protective conductor.
    But the point is not that two or more earth faults of the same phase are counted consecutively. In this case, it is always one ground fault.
    But when the next phase is grounded then you have a second ground fault.
    And you will continue to argue that in the event of a short circuit between two phases of the SWZ will not occur?

    There is one rule. When the UKSI signals the first earth fault, it should be removed as soon as possible.
    Because when another phase "touches" the protective conductor, there will be a boom and darkness will ensue.
  • #42 19677747
    kris8888
    Level 40  
    kkas12 wrote:
    Where does this earth fault come from?
    Well, from the connection of the phase to the earthed protective conductor.
    But the point is not that two or more earth faults of the same phase are counted consecutively. In this case, it is always one ground fault.
    But when the next phase is grounded then you have a second ground fault.

    Ok, if we approach the matter like this, it is obvious. That is, if the second ground fault only occurs when a different work conductor (different phase or N) is shorted to earth.

    But in the case of the operating room, which let's assume that it is fully powered from one phase and two devices in it have L breakdowns to the ground, can it be treated as one earth fault and in this case not to turn off the power?
    Wirnick wrote:
    kris8888 wrote:
    So such a general statement that a second ground fault in an IT system forces the power to be turned off is probably not always correct, certain conditions must be met.

    Until I drank my tea. 20 years of work in IT. I read the theory and eureka - the second earth fault is safe provided that the devices are covered by PE connections (protective conductor network)! Thanks kris !!! It's good that the fuses have tripped the voltage! UKSI and WATCH are just technical additions.

    But now I do not know if you are making fun of me or did you actually read something innovative in the cited theory?
  • #43 19677787
    Wirnick
    Level 30  
    kris8888 wrote:
    But now I do not know if you are making fun of me or did you actually read something innovative in the cited theory?

    You opened my eyes. IT is safe as a premise. You made me realize the role of the protective conductor not only in IT.
  • #44 19677788
    CYRUS2
    Level 43  
    kkas12 wrote:
    But the point is not that two or more earth faults of the same phase are counted consecutively. In this case, it is always one ground fault.

    kkas12 wrote:
    But when the next phase will be grounded then you have a second ground fault.
    A large phase-to-phase current then flows, which is not limited by the N-PE impedances.
    The phase-to-phase current causes the voltage Upe resulting from the voltage divider on the wire resistance + breakdown resistance.
    The voltage from the divider forces the voltage on PE, i.e. on the housings.
    The diagram is not drawn correctly.
  • #45 19677810
    Wirnick
    Level 30  
    CYRUS2 wrote:
    The phase-to-phase current causes the voltage Upe on PE resulting from the voltage divider on the resistance of the conductors + the resistance to breakdown.

    There will always be 0V on PE at IT - ground potential (common) decides. It is the network layout that will adjust depending on the dividers and resistance.

    Added after 17 [minutes]:

    CYRUS2 wrote:
    Since the current flows to PE, there will be no zero with respect to the ground.

    What is the voltage drop on this cable you anticipate? Will it be 60V?
  • #46 19677862
    Krzysztof Reszka
    Moderator of Electrical engineering
    CYRUS2 wrote:
    It will not touch because the N conductor is not accessible.

    CYRUS2 wrote:
    which is not limited by N-PE impedances.

    This is the N or not.
    CYRUS2 wrote:
    If it were so, there would be no need to detect the 2nd short circuit.
    Fuses on the phases would suffice.

    The earth fault detection must be already at the stage of the first earth fault and turned off by the Uksi system or another device. Deviations only occur in facilities that are vital (operating theaters) or that are dangerous during shutdown.
    Wirnick wrote:
    the potential of the earth (common) is decisive.

    Not always, remember that we also have individual earthing systems, e.g. in hospitals.
  • #47 19710041
    Anonymous
    Level 1  
  • #48 19710146
    Wirnick
    Level 30  
    Krzysztof Reszka wrote:
    Not always, remember that we also have individual earthing systems, e.g. in hospitals.
    markus-19 wrote:
    The voltage value will depend on the earthing resistance which is calculated for the acceptable touch voltage.

    I agree with this local grounding, but when it is possible to do it in a rock or in a hospital building.
    An IT installation uses work conductors and a protective earth conductor (PE), so local grounding is an addition to the installation.
  • #49 19710298
    Anonymous
    Level 1  
  • #50 19710334
    Strumien swiadomosci swia
    Level 43  
    Krzysztof Reszka wrote:
    Deviations only occur in facilities that are vital (operating theaters) or that are dangerous during shutdown.
    Wirnick wrote:

    For example ozonation plants and other equipment in a sewage treatment plant.
    Then even the inverters must be IT network ready.

    On the other hand, PE is used because it is foolproof.
  • #51 19710991
    Krzysztof Reszka
    Moderator of Electrical engineering
    Strumien swiadomosc... wrote:
    For example ozonation plants and other equipment in a sewage treatment plant.

    It is due to the prevailing conditions that are dangerous for the person operating the treatment plants that IT is used there.
    Strumien swiadomosc... wrote:
    Then even the inverters have to be IT network ready.

    Man, I have never met a special inverter adapted to the IT network. Well, maybe?
    Wirnick wrote:
    so local grounding is an addition to the installation.

    An obligation to perform it, not an accessory. This is where part of the earth current, which is capacitive, returns.
    411.6.2 Accessible conductive parts are to be earthed individually, in groups or in groups

Topic summary

The discussion centers around the limited use of IT (Isolated Terra) network layouts despite their perceived safety advantages, particularly in high-security environments like hospitals and mines. Key points include the high construction and operational costs associated with IT networks, the necessity for constant monitoring of insulation resistance, and the potential risks following the first earth fault. Participants debate the reliability of IT networks compared to TN (Terra Neutral) systems, emphasizing that while IT networks can maintain operation after a first fault, they become less safe after subsequent faults. The conversation also touches on the specific applications of IT networks in various industries, including healthcare and mining, and the historical context of their use in Norway. Ultimately, the consensus suggests that the complexity and maintenance requirements of IT networks limit their widespread adoption.
Summary generated by the language model.
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