OCB Vs VCB

I don't have much information outside of North America, but I recently purchased medium voltage (13.8 KV) switchgear for 3 new substations. Out of 11 submitted proposals, all were for vacuum breakers.

Since I had a bad experience with a VCB a few years back, I did some more investigation. I could not find a single vendor to offer anything other than VCB in that voltage class. Not only were there no oil breakers offered, I could not even find any air breakers. The only other option available was SF6, which cost about 50% more than the VCB's.

As to your specific question, here is a white paper from a Ukrainian manufacturer stating that, in the medium voltage class, VCB's are 70% of the in-service fleet for USA and Europe, 100% in Japan, and over 50% in Russia.

Our company is using VCBs in incoming, outgoing and bus coupling panels of 11KV rating manufactured locally in Pakistan by Siemens, Areva and PEL as well as Syed Bhais which are giving satisfactory results.

All what I can say is, I was previously recommended by expert people the following:

VCB is always preferable for medium voltage applications, while OCB and SF6 is preferable for high and extra high voltage applications. Please, don't ask me the reasons .

I am working in power plants in India and we are using BHEL make VCB's for 6.6kv medium voltage system.WE are using 66 vcb's for different motors,there is not much problem.

with regards

C.B.Deshmukh

Electrical engineer

I'm working in an industrial plant in Egypt and we are using AEG VCBs for 6.6kv, and we are using OCBs and SF6 for 66kv main feeders. Also, there is not much problems.

It may be an economical reason, or may be concluded earlier from particular applications out of our scope. Also, type of system earthing may give preference to one over another.

Our power system is fully isolated from the earth.

Regards

Samak

We are using VCBs of GE Shanghai and well satisfied with the performance.

Mostly in the world, for medium voltage one prefer VCBs because it is modified and latest. Advantages, as you said, you know well. In VCBs there are categories according to the application.

Until recently Oil Circuit Breakers were used in large number . There are number of disadvantage of using Oil as quenching media in circuit breakers. Flammability and high maintenance cost are two such disadvantage.

Manufacturer and users were forced to search for different medial of quenching.

Air blast and magnetic air circuit breakers were developed but could not sustain in the market due to other disadvantage . These new type of CB were bulky and cumbersome.

Further research were done and simultaneously two type of breakers were developed wit SF₆ as quenching media in one type and Vacuum as quenching media in other.

There are a few disadvantage in this type of breaker also. One major problem is that the user of the breaker are biased in favour of old fashioned OCB and many of user always have step motherly attitude to the new generation of the breakers

No. of SC operation :- SF6 - 10 - 50

VCB - 30 -100

No. of full load operation :- SF6 - 5000 - 10000

VCB - 10000 - 20000

No. of mechanical operation SF 6 - 5000 - 20000

VCB - 10000 - 30000

MTF are identical for SF6 and VCB

Thanks for all, however you missed my points which is I'm looking for comparison statistics or trends between usages of OCB compare to usage of VCB. If any wants the advantage of using VCB instead of OCB I used the following in my report.

Advantages:

The advantages of replacing OCB with VCB are as follows:-

1. Technical Improvement.

• Can be configured for automation
• High speed auto-reclose
• Fault level withstands increase.

1. Performance Improvement.

• More reliable
• Oil fire hazard risk eliminated.
• Life time extension
• Availability of spare parts.
• Improved Safety.

1. Operation Costs Reduction.

• Oil-less (Oil not required)
• Reduced maintenance
• Revalue of company asset.
• Lower cost (custom made OCB spares will be high)
• Can be condition based maintenance (No preventive maintenance)

WHAT I need is document (Appendix B) to support the following paragraph which I used in my report:

"Study shows that world wide OCB usage is decreasing in the market due to environmental and maintenance costs (Appendix B) which means in nearest future it will be difficult to find oil circuit breakers in market".

Can't help you with the stats or studies - there may be some IEE studies, but I'm not a member. I know that the advantages are so obvious that I didn't even consider asking for OCBs - only VCBs were considered. But I also understand that one sometimes has to convince non-electrical people. Good luck!

Thanks for your interest in my case