Busbar Sectionalizing Isolators

Did you try this?

" Sectionalizers. The sectionalizer is a self-contained, circuit-opening device used in conjunction with source-side protective devices, such as reclosers or circuit breakers, to automatically isolate faulted sections of electrical distribution systems. "

That takes me to medium voltage pole mounted sectionlizers, not HV isolators used in subdividing busbars. Big difference between the two.

Your second image gives you a better idea of what the purpose is. The bus configuration (they call it "double busbar") is what I would call "straight bus with transfer bus." You will note that there is a transformer connected on each side of the sectionalizer. It doesn't tell if the lines are the energy source or the transformers, but it doesn't matter. The two buses allow very flexible selection of which transformer is connected to which lines. They even add the "bus coupler" cross-tie, which can give even more options for switching which loads are on which bus. In the event there is a bus fault, that particular bus can be easily disconnected from the lines and transformers that were on it, and the load shifted over onto the other bus, but in normal operation the selection of which loads are on which bus can be useful for utility power flows.

This bus approach tends to be costly. Everything is duplicated: bus, switches, etc., plus there are also the cross-tie devices and connections. However, the advantage is flexibility and high availability if the system MUST be kept in service. Other schemes include double breaker/double bus and breaker-and-a-half. You can look these up on your own to see the relative costs, complexity, and flexibility.

Straight bus with transfer bus (aka main and transfer bus) would be this:

Typically 6-12 elements are connected to one side of the sectionlizing disconnects and 6-12 elements on the other side.

My question is why do you need them when you already have one or even two extra busbars that can take the place of any other main busbar?

Typically all breakers in scheme are normally closed- source supply does not matter and at times it changes hourly.

Here is teaching model that has isolators on the busbar itself:

https://www.leybold-shop.com/ausstattungen/elwe-training-systems/power-engineering/switching-of-high-voltage-systems/double-busbar-system/experimental-stand-double-busbar-system-8-1517040-000-10-1.html

I mean, why go through that trouble?

why go through that trouble?

As said already by several posts - security of supply. If your supply depended on just one breaker, would you be happy if you were cut off while the breaker was serviced.

Many expect power 24/7 and would complain much if cut off for 30 minutes every 10 years - this bus/breaker scheme is just one of the items that gives continuity of supply.

I understand, and thats where the second or even third busbar comes in. So why sub divide when a backup is already in place?

Usually the sectionalizer is required in order to separate redundant supplying feeders as two feeders supplying a same substation. In this substation you may have -for instance- a H scheme supplying two step-down transformers, two pump-one reserve-, or else. In a double busbar system one of them serve as transfer busbar. Usually only one busbar is provided with sectionalizer. All of this redundant equipment is necessary if you cannot give yourself much time to renew your power supply after a break. For example, in a very large industrial complex, where one hour of disruption costs $ 1 million, another $ 100,000 equipment that could avoid this disruption will be welcome.

If that is the case then what is the bus coupler breaker for, seems like a very expensive switch.

Disclaimer: I know absolutely nothing about this subject, but, it seems to me that:

Everyone seems to be concentrating on the bus duplication/redundancy.

The sectionalizing switches are to enable isolation of equipment which is faulty or for routine maintenance.

But here what I'm trying to get across: You don't need the sectionlizing switches in order to take a busbar out of service without interrupting any elements.

But what if a switch fails closed?

If 232-1 Fails to open or needs to be taken out of service you make sure coupler 212 is closed along with disc 212-1 and disc 212-2. You then close 273-2 then opening 273-1. Close 274-2 then open 274-1, close 275-2 open 275-1 ect- do this until all bays have been transfered to C22.

Now you open breaker 232, followed by opening 212 and 212-1. Lastly you open disc 232-3. Apply grounds as required. The failed disconnect 232-1 can now be serviced.

No bay is interpreted except one and no busbar subsectionlizing was required.

Noting Electron Spinner's post #13......A suggestion, going back to original post & diagram with red arrows.

The normal situation is to share the load between the two in-feed transfo, one on the upper bus, second on lower bus. For this they must be in parallel, but also there is the coupling breaker in the middle which can separate them in the event of a fault - only half the load is lost.

Suppose there is a fault on the upper right-hand bus. One transfo breaker & bus coupler will open.

To get back all load, without maybe overloading one transfo, the transfos need to be paralleled again. Unless there are syncronism & phase check relays on both transfo breakers as well as the bus coupler, the bus coupler is needed to do this - but it should not close if it is still connected to faulty upper R.H. bus.

The disconnector at right of coupler breaker allows the faulty section to be isolated, so bus coupler can be used - it also allows the faulty bus to be earthed & repaired while there is still 3/4 of the system. It also gets 3/4 of system while busses are extended to new breakers.

But why 3/4s. You still have one working bus.

With half a bus isolated, there are 3 working half busses out of 4 half busses in a fault-free system.

That is 3/4.

Sorry for being such a hard head, but I still don't get it. All bays can be transferred to the other bus. You don't need midpoint sectionalizers to do that.

Study the informative feed back you have been given.

Go to sleep with it on your mind.

In the morning,it will dawn on you.

Still hasn't dawned. All elements are normally equally divided among the busbar with the coupler closed. All elements can be placed on any single busbar with the other shut down for maintenance. The midpoints do absolutely nothing.

To continue the saga.

The RH top busbar has failed. You have 3/4 of system.

LH bottom busbar gets fault. You can still, with the disconnectors/ bus-coupler CB, link Top LH busbar to bottom RH busbar to parallel transfos or operate with them separated.

Not with one bus coupler. RH top faults, a disconnect can not break fault current, so the bus coupler must open- also dropping LH top. RB and LB remain, so half the system.

The substations I'm thinking of do not require separate operation. All circuits are electrically linked together.

They would not install them without an economical and valid reason.

Study it diligently without a preconceived idea that they were not required.

A teacher can teach,but they cannot learn it for you.

Wait till in the morning,it will dawn on you,I promise.

Correct, but I can't figure out that reason nor does literature explain why. I've thought about it for some time. In so far the replies here make assumptions that there is more then one bus coupler or that busbars will operate independently of one another. Maybe independent operation is the intent- but I can't see it being of use at 400, 220 and 132kv.

Here is a link for you to study.

It was easy to find on Google.

I simply entered your question and got lots of results.

https://testguy.net/content/256-electrical-substation-bus-schemes-explained

Read and understand it,and the associated links.

This will improve your knowledge of the concept.

You will have to learn it yourself,I cannot learn it for you.

That link answers nothing and just confirms what I already knew:

This configuration utilizes two buses and two breakers per circuit. Both buses are normally energized and any circuit can be removed for maintenance without an outage on the corresponding circuit. Failure of one of the two buses will not interrupt a circuit because all of the circuits can be fed from the remaining bus and isolating the failed bus.

Substations with the double bus double breaker arrangement require twice the equipment as the single bus scheme but are highly reliable. Load balancing between buses can be achieved by shifting circuits from one bus to the other. This scheme is typically found in EHV transmission substations or generating stations.

Again, you can already shutdown any busbar without removing bays. So why add isolators in the center?

Honestly all the replies thus far tell me folks here have a limited understanding of HV and EHV substations and they themselves are unsure only making guesses.

Returning to the second diagram in the original post, I now notice the picture filename contains GIS. That probably means Gas Insulated Substation - not Gas Insulated Switchgear. Note that this GIS has only one breaker per circuit, connection to either bus is by disconnectors.

So all the busbars are SF6 insulated. SF6 is thousands of times worse as a greenhouse gas than CO2. If there is a busbar fault, or a new breaker is added at end, it makes sense to not have to pump out the whole busbar by having the disconnectors in the middle. Finding & dismantling/ re-building the faulty section also takes a lot more time than open air insulation.

Without the 4 disconnectors at the middle, the bus coupler is out of action.

As I pointed out, with the disconnectors, despite the failed half-bus under maintenance the coupler can cross-over and make a busbar with a transfo on each side & still have on operational coupler.

The disconnectors also allow maintenance on the busbars associated with the bus-coupler.

Again, I think people are commenting on something they do not understand assuming I'm the novice. A GIS substation is divided into partitions, so repair of a busbar does not require 150+ feet of busbar being pumped out. Only a small section.

Page 11 onward:

https://new.abb.com/docs/librariesprovider78/chile-documentos/jornadas-tecnicas-2013---presentaciones/6-jessica-ponce-de-leon---gas-insulated-switchgear-concept-design-for-service-continuity-in-gis.pdf?sfvrsn=2

Another example:

https://cigreindia.org/CIGRE%20Lib/CIGRE-Paris-Session-2014-papers-Report/B3/B3_118_2014.pdf

I will say that you are correct in one thing, that yes you can take a busbar out of service and still have the coupler in operation which can be of advantage should you get a fault during maintenance.

However, why add them to a triple busbar station?

I'm not a GIS man.

As for "commenting on something they do not understand", you have not helped understanding.

1. The original post #1 gives two diagrams with sectionalisers. The first gives no indication of the purpose of the circuits. The second appears an actual system - looking like a distribution point with two transformers.
2. Your post #4 has no sectionalisers to comment about.
3. Your post #5 "Teaching model" has sectionalisers, but also incorporates the bus coupler with them in a way which permits the busses to be connected by switches even while the bus coupler is out for maintenance.
4. Your post #13 has double busses at LV & HV, but no sectionalisers to comment about.
5. Your post #13 questions sectionalisers in a triple busbar - is that the real question.

You appear to not have considered enough the practicality and speed of getting power back to circuits after a faulty section is isolated, which is worth some extra switches.

As a point for discussion, take the following sketch, a skeleton of your #4 diagram; which is a simple system which allows a circuit to be fed [and protected], without break, through the bus coupler via the transfer bus & a switch, while its breaker is serviced; but adding a sectionaliser SEC.

The circuit on the right is sole incomer.

Without sectionaliser SEC, fault on main bus M disables all loads.

With SEC it is possible to disconnect the source, open SEC, close the right hand-most switch and the coupler and feed the left hand circuits. If the fault is left of SEC, opening SEC & closing the source breaker gets right hand circuits back. So half the circuits can be restored quickly,

You're getting stuck on semantics because frankly you don't have an answer and are just guessing yourself. A senior EU relay technician or substation engineer would be able to give succinct answers.

I normally don't do this, but here goes:

1) As a generic example of what I'm referring when I say "busbar sectionalizers"

2) Yes, because I'm replying to post #3 which incorrectly calls SBDB (single breaker double busbar) main and transfer. So I included a diagram of what main and transfer actually looks like to clear up any confusion.

3) As another example of sectionalizers reiterating that they are common enough/ of enough importance to be added to teaching models.

4) An actual example comparing to none sectionalizer stations. Over 2/3 of the SBDB substations on earth are like that- without sectionalizers. Hence my mysticism.

5) Members here are telling me the sectionlizers allow load to be transferred such that with 1/4 of the busbars out of service load can still be placed on either side of a coupler meaning that a busbar fall or breaker failure while in maintained will only clear half the circuits instead of all of them. This I understand, and why single breaker triple busbar came about. So, if single breaker triple busbar addresses this concern, why are single breaker triple busbar stations still cropping up sectionlizers- only appearing redundant to the scheme?

A fault on any busbar causes the coupler to open with associated bays with OR without sectionlizers.

The faulty busbar is isolated by opening the disconnects to all bays attached to the failed bus then closing all the disconnects attached to the healthy bus followed by the bay breakers.

The 4th image does not have a transfer bus. It has two main busbars, called single breaker double busbar. I think we are inadvertently discussing a different system altogether.

In reply to post #30 by Electron Spinner ES.

This thread began with ES questioning the usefulness of busbar sectionalisers, tabling several double busbar diagrams to the thread in discussion.

The contributions have brought ES round to the view that sectionalisers have their purpose (see 5. of post #30 by ES) - so now ES's question is "why have sectionalisers in triple busbar systems".

Point 4) of subject post #30 by ES states "Over 2/3 of the SBDB substations on earth are like that- without sectionalizers. Hence my mysticism.".

If one looks at the second document referenced in post #27 by ES.....

https://cigreindia.org/CIGRE%20Lib/CIGRE-Paris-Session-2014-papers-Report/B3/B3_118_2014.pdf

at page 6, there is the following, relevant text I marked bold....

<<It can be seen so far that the main problem during dielectric test is a lack of required gaps and grounding. Therefore, this calls for additional gaps to be put into GIS at the right location that helps reduce the service interruption. After meticulously reviewed, the suitable location for the additional gap is at the middle of the busbars as depicted in Fig. 9. For this purpose, the disconnecting switch is used to provide the required gap and sectionalize the substation into two sections. It is evident from Fig. 9 that during the dielectric test, all feeders in the section of the affected bay have to be shutdown while those in the other section remain in service. For EGAT, the transmission system is designed with N-1 criterion. The shutdown of one section of a substation does not affect the system operation because the other section has an adequate capacity to handle the same amount of power. This GIS design option is applied to an important substation.>>

Finally, since ES has been rude to HiTekRedNeck in post #32, I feel justified in recalling my wise first boss warning me of the dangers of being "Hoist with your own petard".

Thank you- good eye. :) I have no doubt that is the reason behind installations involving GIS. I will double check my notes. But my mysticism is still propelled by such mid bus disconnects being found in AIS substations where such limitations are not encountered. That is baffling.

Being rude- a remark which translates to being shamed for not consenting to persecution. I will not allow my character, knowledge, skill, contributions, imagination or beliefs to remain a sitting duck. I am far from any novice only choosing to stand humble. Life experience and history has routinely taught me that the greatest suffering and some of the greatest intellectual oppression come from those who esteem themselves as vastly superior whilst condemning others with the same hand. 1940s Berliner Philharmoniker routinely sympathized playing Symphony no 9 Beethoven, Richard Wagner, Richard Strauss and other famous composers to their highly respected elite guests.

You may have become desensitized from time or his approval; but HiTek's avatar, choice of words, and signature emphasizing fools from the start told me he is here to play a character at the expense of others.

With that said the west is encountering an ever increasing shortage of engineers and trades men that is only now starting to play out. It would be in the best interest of society to give current and future engineers a reason to feel respected as that can be found elsewhere in great abundance.

If you treat me as human "Hoist with your own petard" will never be a qualm so don't worry about it.

Instead of answering my questions about your qualifications,you responded with an ad hominem attack,in an attempt to deflect attention from your lack of qualifications and knowledge.

Your attempt to offend me has no value.I must respect the person before I value their opinion.

Since you did not answer the question about your skill level,I will presume that you are a philosophunculist,and not a qualified engineer or technician,and you wish to be presumed by all to be a silent,humble supremely qualified individual,but by asking such a simple question,you have exposed your lack of expertise.

You do not want the correct answer,you simply want to find someone that agrees with your opinion about isolators.If they do not agree,it is not the right answer.

You will never find the "right" answer if you cannot comprehend the information already given to you by the many replies and admit that your opinion about the isolators is wrong.

"Consult you local home center on guidance for further instruction. They have books with step by step instructions for further detail" (A quote from one of your previous posts.)You seem to like denigrating others to imply your superior intellect.

Good luck in your quest.

I unsubscribed from this conversation,but I ran across it while following 67Model's posts,so if I happen to see your reply,it will be by chance,not by intent.

"deflect attention from your lack of qualifications and knowledge." "you have exposed your lack of expertise."

Again, you fetishize this.

If it was so easy for you in the time spent writing the above diatribe let alone sifting my posts you could have made me look like a fool by explaining (in detail) the complete list of advantages gained by having busbar isolators the same way the purpose of a bus coupler is explained here:

https://www.eng-tips.com/viewthread.cfm?qid=423232

Asking about bus disconnects is not a simple question because 1) It is not encountered in many utilities 2) Single breaker double bus schemes are rare if not unheard of in the IEEE world. This same question would manifest in any US or Canadian engineer hence why I am specifically asking on an international forum.

From this link:

https://electrical-engineering-portal.com/circuit-configurations-hv-mv-switchgear-installations

"Experience shows that more complex coupling arrangements are usually needed in order to meet practical requirements concerning security of supply and the necessary flexibility when switching over or disconnecting."

I get what they are saying, but I still believe that having them is more cost and failure then what is given in return.

What is your job description in your trade or craft?

How much training do you have in your field of endeavor?

Any college level or technical training?

Do you work for a utility or construction company?

How much experience do you have in this field?

The level of your questions and your replies indicates that you are a beginner,and not a seasoned and knowledgeable employee.

Your failure to understand is not a fault of those that have tried to help you.

You have been provided with all of the information required,but YOU must put in a diligent effort to understand it.

(UNSUBSCRIBE)

Everyone else aside, reading your posts here and elsewhere you come across as an profoundly arrogant individual offering nothing but elitist disparagement given an opportunity.

Stop pretending to be Nikola Tesla as you are in no way associated with his welcome gift of imagination vs your uninvited gift of condescension.

With that said I shake your hand in sincerity for unsubscribing as the rubbish took itself out to the curb.

For future readers- in so far I plan on adding isolators only when exceeding 12 bays. Be it double or triple busbar. I still want to leave them out, but mostly adding them on the basis regarding a fire or catastrophic event. That way at least half the station can be brought back into service reducing impact.

I will however spec design such that any busbar, bay, or gas section can be taken out for replacement without shutting down the the other busbars.

Similar philosophy for AIS substation.