HV Breaker Hydraulic vs Pneumatics

[cuky2000]

We came across an application with HV breakers with some of them specified with hydraulic mechanism and others specified with pneumatic operating mechanism.

Although both units have some pricing and physical differentials, the electrical performance is pretty much similar.

Doe any one know why to specify two breakers design in the same facility?

 

[potteryshard]

In my experience, stay away from both. The pneumatic breakers over time suffer endless compressor problems, leaks, condensation and corrosion issues. The hydraulic units begin to leak internally at the check valves until the pumps run continuously and need replacement. Both designs require relatively exotic high-speed pilot valves which are troublesome and difficult to source.

I've experienced much less trouble with mechanical spring (typically torsion bar springs in the higher voltages) driven breakers.

 

[oldfieldguy]

I'm with potteryshard on his assessment, although if I had to choose one of your two choices, I'd go with pneumatics, because there is less oil to spill/squirt around the compartment. I've worked with several spring mechanisms and they seem to eliminate a lot of problems. The only thing that can leak on the mechanism is the gearbox of the charging motor and that's like a teacup (obligatory SI reference) of oil.

With the disappearance of oil circuit breakers, per unit maintenance costs have gone down on HV breakers and most calls concerning them are related to the pneumatic or hydraulic mechanisms.

As for the question "Doe any one know why to specify two breakers design in the same facility?", I'm thinking that vendor ! has offered a really nice round of golf, and Vendor 2 has indicated multiple free meals.

But then I'm considered cynical...

old field guy

 

[ScottyUK]

I can recall only one hydralic problem among 60-odd 3x 1-pole breakers - an installed base of nearly 200 individual actuators - in 10 years. No one had experienced a hydraulic fault before I joined the company either, so that's another 8 years trouble-free. 3600 actuator-years between failures isn't too bad a record - I wish a few other things in that plant had been as reliable.

The breakers in question were ABB's ELK series from the Swiss part of the empire and were generally a delight to work on, other than the KKS numbering system used to defeat me because I didn't use it frequently enough to stay conversant!


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If we learn from our mistakes I'm getting a great education!

 

[cuky2000]

Hi all,

The interesting part is both units (hydraulic and pneumatic) were supplied by the same vendor.

The substation is in breaker 11/2 configuration designed for 50 kA using breakers rated for 63 kA independent pole operation (IPO). There are two single shunt capacitor banks and two shunt reactors mechanically switched by dedicated circuit breakers.

I tried to find the rational with some of the utility engineers involved on this design and also with the vendor of the circuit breaker. However, I was not lucky finding a good answer to justify using one vs. the other type of breaker. Appear that the engineers that developed the guideline are not longer with the utility and not ones know the background or rational of this application.

I am posting a list of rated parameters for both breakers with the hope that some one brings some light or suggestion to demystify why both units are used in the same substation.

 

[davidbeach]

Where they all installed at the same time? Or was it that one type was installed for the initial construction and the other type used for an expansion?

 

[cuky2000]

The breakers are new purchased at the same time. According with the manufacturer they can provide same type of breaker design.

The torsional bars operating mechanism do not meet the CO duty cycle required by the utility project and the utility standard practice. The selection of this vendor was based in several factors including the high TRV rating (above the Std values by IEEE/IEC) driven by a few HV series cap banks connected in the power systems.

 

[bacon4life]

Perhaps an attempt to avoid some common mode failures? Looks like the whole interrupter is a different design. Is there a pattern to how they are spread out?