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Anonymous Poster #1

Transfer Bus Bar for HV Substation

02/21/2017 11:16 AM

Are transfer bus bars/breaker bypass switches recommenced in new build air insulated substations? What is typically done today throughout the world for single breaker elements?

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Guru
Engineering Fields - Electrical Engineering - Been there, done that, still doing it. Engineering Fields - Control Engineering - New Member

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#1

Re: Transfer Bus Bar for HV substation

02/21/2017 2:10 PM

Typically only a licensed electrical engineer with a degree is hired to answer this and many other questions. I also find your proposed scenario dubious at best. A High Voltage (63kV → 22kV) substation would have three phases, multiple power voltages and paths and thus many more than a single breaker.

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Anonymous Poster #1
#2
In reply to #1

Re: Transfer Bus Bar for HV substation

02/21/2017 7:23 PM

From your answer I can only deduce you have zero experience in power engineering or no desire to contribute anything constructive considering the terminology is self explanatory. Notice my use of single breaker per element (ie; single breaker, double bus), not 1 breaker for a multitude of incoming lines and components.

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Anonymous Poster #1
#3

Re: Transfer Bus Bar for HV Substation

02/21/2017 7:42 PM

And just to clarify, by elements I am referring to transmission lines, cables, shunt capacitors, shunt reactors, transformers, phase angle regulators and the like. The breakers in question are modern SF6 spring mechanism dead tank breaker.

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Guru

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#4

Re: Transfer Bus Bar for HV Substation

02/22/2017 2:38 AM

I don't think the inquire was clear and it is still not.

Do you mean your substation is an indoor high voltage [110-220 kV?] in open air double busbar-one main and the second only for transfer [without incoming supply line] the breaker is SF6 insulated hydraulic-spring [for instance] closed and spring disclosed, the busbar disconnector is an open type in air. This is a classic substation before GIS.

See [for instance]: ABB Switchgear Manual 11 Edition.

https://www.scribd.com/doc/118169283/ABB-Switchgear-Manual-11th-Ed-2006

vol.11 High Voltage Switchgear Installation or:

ABB Switchgear Manual 12 Edition.

http://new.abb.com/de/en/ueberuns/geschaeftsfelder/power-grids/switchgear-manual

So, what is your question?

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Anonymous Poster #1
#5

Re: Transfer Bus Bar for HV Substation

02/22/2017 6:30 AM

Outdoor air insulated substations, 66 to 400kv.

My question is, is it still common to include bypass facilities for the circuit breakers to allow for breaker maintenance? Or is this no longer recommended? Apologies if I am not being clear.

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Anonymous Poster #1
#6

Re: Transfer Bus Bar for HV Substation

02/22/2017 6:37 AM

Here are two examples of substations where each circuit breaker can be taken out of service while the transmission elements (transformer or line) remain in service:

Here is a substation without any breaker bypass ability:

I know the prior was used extensively in the 1970s when bulk oil breakers were common, but is the latter now becoming more common in new construction with SF6 breakers?

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Guru

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#7

Re: Transfer Bus Bar for HV Substation

02/22/2017 7:04 AM

You are right. According to:

IEEE HV Substation Design: Applications and Considerations

http://sites.ieee.org/houston/files/2016/04/2012-10-02-HV-Substation-Application-Design-Oct-2-3.pdf

[See page 43] the tie is only optional.

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Anonymous Poster #1
#8

Re: Transfer Bus Bar for HV Substation

02/22/2017 7:17 AM

Thanks for the doc :)

But my question is, is the practice these days to skip it or keep it?

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Power-User

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#9
In reply to #8

Re: Transfer Bus Bar for HV Substation

02/22/2017 8:52 AM

Wouldn't the cost - benefit analysis be very specific to the contemplated installation, including fault tolerance of users, external environmental factors, and the design of the system this equipment is connected to?

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Anonymous Poster #1
#10

Re: Transfer Bus Bar for HV Substation

02/22/2017 9:35 AM

It would, of course, but where the variable remains open in the equation is how reliable, and how much maintenance do modern SF6 circuit breakers need?

Ideally ditching the transfer bus and extra disconnects would be a step forward, but not unless planned and unplanned outages of breakers go down.

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Power-User

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#11
In reply to #10

Re: Transfer Bus Bar for HV Substation

02/22/2017 9:58 AM

I have limited experience with SF6. Equipment I installed in the late 1970s is still there, Westinghouse 35kV class, I think 2 (leaky) bottles exchanged from a population of 7 (3 pole) breakers, maybe 2 operations per year average. My install design allowed isolation (visible gap) on both sides to work on the equipment, and still run the industrial plant at capacity.

In this environment, repair cycle and outage would be intolerable, requiring outside services, maybe days, maybe longer, especially as the equipment obsoletes out. A hard analysis (lost production cost per hour) probably would not justify the expense, but if you are late shipping product and your customer goes somewhere else....

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Anonymous Poster #1
#12

Re: Transfer Bus Bar for HV Substation

02/22/2017 10:06 AM

Generally equipment is redundant and there is enough reserve generation so a signle element outage is often not a problem, but when you have on circuit out for breaker maintenance and then another goes, it makes you think twice.

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Guru

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#13

Re: Transfer Bus Bar for HV Substation

02/23/2017 12:43 AM

In my opinion, if you are positive the Line 1 and Line 2 are synchronized then you may use a couple of bus-isolators in order to transfer from a bus to another when it is required. However, the bus coupler closed is the security of synchronizing. The breaker overcomes a short-circuit, an isolator does not.

If the supplied consumers could be interrupted for a while during the transfer from one bus to another you probably don't need the bus-coupler.

However, the transfer from one busbar to another by isolators only will take seconds-or more- while by opening and closing breakers could take a few cycles.

If the supplied consumers could not be interrupted, then you have to check the synchronizing and to close the bus-coupler at first.

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