- #1
Why Not Stack Busbars?
- Thread starter Ivan001
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Discussion Overview
The discussion revolves around the feasibility and practicality of using a busbar arrangement where one busbar is positioned above another, as depicted in an attached image. Participants explore the implications of such a configuration in terms of mechanical strength, cooling efficiency, and adherence to established standards in electrical engineering.
Discussion Character
- Debate/contested
- Technical explanation
- Exploratory
Main Points Raised
- Some participants question the lack of information regarding the practice of stacking busbars, suggesting that it may not be as uncommon as implied.
- Concerns are raised about potential fire hazards from animal nests between busbars when power is off.
- One participant mentions that similar configurations have been used in lower power applications, indicating that mechanical strength is a critical factor influenced by fault current stress.
- There is a discussion about the mechanical strength of insulators and whether they can support the weight of busbars when arranged vertically.
- Participants express the need for sources or evidence to support claims about the practice of busbar arrangements, highlighting the absence of such configurations in available examples.
- Technical reasons are provided for why busbars are typically mounted on their sides, including improved convection cooling and reduced sag.
- One participant emphasizes the importance of understanding historical design choices before proposing new configurations, citing practical challenges encountered in dismantling substations.
Areas of Agreement / Disagreement
Participants do not reach a consensus on the validity or practicality of stacking busbars. Multiple competing views remain regarding the mechanical and electrical considerations of such an arrangement.
Contextual Notes
Participants note limitations in available evidence and the reliance on historical standards that may not encompass newer configurations. The discussion reflects uncertainty about the mechanical properties of insulators and the implications of design choices.
- #2
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Your question is SERIOUSLY lacking in information, but who says it isn't?
- #3
Baluncore
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How would you put out the fires that start in the animal nests built between the bars when the power is off?
- #4
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Why not assume that every feasible method is in use somewhere? and that many infeasible methods have been tried and discarded.
It would be very hard to say that some method has never been used anywhere.
It would be very hard to say that some method has never been used anywhere.
- #5
Windadct
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This is used - it has been a while but I am thinking often in MCC or other lower power - or more importantly lower fault current applications. The mechanical strength of the bus is almost entirely determined by the fault current stress.
- #6
Ivan001
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Did you seen it somewhere?phinds said:
You can everywhere buy horizontal, vertical or stair type of busbar insulators, but nowhere something like that. I guess that those red insulators have low mechanical strenght in regards to short circuit power between two bars. I asked it because I always see three phases placed horizontaly with some spacing between phases, but never seen one above other..
- #7
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The fact that you haven't seen it sold that way is irrelevant. I asked you where you heard that it can't be done and you are ignoring the question. On this forum that is not acceptable. When you are asked to provide a source for a categorical statement the rules say you have to provide it. You said it isn't practiced. Give me a source that says it isn't practiced.Ivan001 said:
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- #8
Ivan001
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OK, I understand.phinds said:
If you google some of the key words: busbar system, busbar spacing insulators, etc...you will get a lot of examples with vertical, horizontal or stairway busbar systems, but there will be no picture which represents the situation from my question.
Now, please give me a source where we can see the arrengment from my picture?
- #9
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Absence of evidence is not evidence of absence. You continue to evade the question.
- #10
Ivan001
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Yeah of course. In that case, can you give explanation why we can use one busbar above other or why we can't. Is insulator's strenght too week for this type of arangement or not?phinds said:
- #11
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See post #2Ivan001 said:
- #12
Baluncore
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Convection cooling is improved by mounting the bars on their sides. Better cooling reduces the need for copper and support for that mass.Ivan001 said:
A bar must support it's weight between insulators, there is less sag when mounted on edge than when flat.
The insulators are subjected to less voltage where the bars are supported from a grounded chassis. Leakage or voltage breakdown should be to ground, not to another phase.
Bus bars come in limited lengths, they must be joined. Also, how do you make a tap to the bus if you cannot inter-finger one bar between two at the same potential?
Threading a bar into the support structure, or installing an insulator, should not require disturbance of other bars.
Sometimes the coded standards are based on what worked 50 years ago. If that standard does not include a particular configuration, then it cannot be used.
There are many practical and electrical reasons why the use of some particular configuration is unusual. How many other reasons do you need?
- #13
berkeman
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Well said, thanks.Baluncore said:
- #14
Baluncore
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@Ivan001
The insulators you show in post #1 have an internal thread at each end. You must tighten the screw with a spanner, without rotating or damaging the insulator. Where two insulators meet at a bar you will need a short threaded stud. But that cannot be tightened without gripping and risking damage to the insulator surfaces while overcoming the friction between the bus bar and the radius of the insulator end. Staggering the insulators so the screw heads can be accessed, will introduce a whole new set of distorting forces to the bars and insulators. It will also lead to a difficult hole pattern in the bars that will make design difficult. Why invent a whole new set of problems.
I have dismantled two electricity substations for scrap, so I really appreciate the convenience of access to the nuts and bolts that held them together. The sub-stations were designed by engineers who had worked through WW2, so were well aware of the ways to reduce indirect bomb damage and speed repair. Taking things apart can be highly educational. You should not design a new solution until you thoroughly understand the multi-dimensional reasoning behind the old design.
The insulators you show in post #1 have an internal thread at each end. You must tighten the screw with a spanner, without rotating or damaging the insulator. Where two insulators meet at a bar you will need a short threaded stud. But that cannot be tightened without gripping and risking damage to the insulator surfaces while overcoming the friction between the bus bar and the radius of the insulator end. Staggering the insulators so the screw heads can be accessed, will introduce a whole new set of distorting forces to the bars and insulators. It will also lead to a difficult hole pattern in the bars that will make design difficult. Why invent a whole new set of problems.
I have dismantled two electricity substations for scrap, so I really appreciate the convenience of access to the nuts and bolts that held them together. The sub-stations were designed by engineers who had worked through WW2, so were well aware of the ways to reduce indirect bomb damage and speed repair. Taking things apart can be highly educational. You should not design a new solution until you thoroughly understand the multi-dimensional reasoning behind the old design.