SF6 Breaker Maintanance 1

[Mbrooke]

What kind, and how often do new (post 2010) dead tank breakers need maintenance? 38kv-362kv class. Looking for any real world insight or documentation on the subject.

 

[stevenal]

If you're a NERC registered entity, check out PRC-005 as it relates to trip circuitry. The instruction manuals should include some checks. SF6 gas density checks are important.

 

[Mbrooke]

Great info, will check RRC-005 out. In regards to the gas density, is visual observation of the pressure gauges sufficient or would that be over simplifying the complex?

 

[FrozenE-]

Hi Mbrooke, we use the gauges primarily for routine patrol checks (weekly/monthly kind of idea). During a major breaker maintenance, usually around 10 years, the density monitors themselves are verified for correct operation and setpoint, and typically the gas inside the breaker is tested using a multi-gas analyzer.

Based on your first question you're asking about general maintenance requirements, not just the SF6 gas itself?

 

[JensenDrive]

Trip and close test every 3 years is our company's protocol.

 

[Mbrooke]

Yup, general maintenance of the whole breaker itself.

 

[FrozenE-]

Based on some surveys of utilities I've seen, there are a lot of differing ideas on what the correct amount of breaker maintenance is. However -

First and foremost, of course start with the manufacturer's recommendations; we vary from them as time goes on and experience with individual types is gained. The specifics obviously change for the different manufacturers & models of breakers. Depending on the type of operator used (spring, air, hydraulic, etc) the maintenance required can change significantly.

But as a rough summary - monthly patrol checks (record counters, , check gauges, stick head in cabinet as a quick observational check); annual heater and operational checks along with a basic operator inspection (it's cold up here, heaters are important); 5 year checks on density monitors and depending on the operator other pressure switches, etc; and usually around 10 years, major maintenance - usually a major mechanism check (including lubrication), breaker timing and motion analysis, insulation checks (esp at those higher voltages as grading caps are more likely), gas checks/density monitor checks, etc.

 

[JensenDrive]

Breaker test is part of 3 year relay trip check routine. I assume they do more than trip and close breakers, but likely something closer to what FrozenE mentions. Relay test routine at 3 years is pretty simple; not a full performance and control system check. Inject currents and voltages and trip output, verify settings against records. Three years is the published goal but gets delayed a lot I hear.

 

[Mbrooke]

What about testing contact parting time? Or something complex like this?

https://www.youtube.com/watch?v=PKXPeTvmVQg

I can understand the delay, its not always easy to schedule an outage.

 

[crshears]

Hey mbrooke, our utility performs "breaker timing tests," which as I understand it includes not just contact parting time [particularly with independently driven phases] but trip and close mechanism actuating time, and the timing of the various pallets in the mechanism and its multipliers, viz., early trip contacts for breaker fail protection, etc., etc., with, just as FrozenE suggests, scheduling initially based on manufacturer's recommendations but subsequently tweaked as operating and service experience dictates.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[FrozenE-]

Mbrooke, the "breaker timing and motion analysis" for us includes coil checks, dashpot operation (if applicable to the breaker), A/B contact timing, mechanism travel measurement, 100A micro ohmmeter contact resistance checks, DRM if a gas breaker where contact wipe can't be measured, and many other checks. For the measurement of most of these parameters we use Programma (owned by Megger these days) equipment. There are other manufacturers that provide equivalents.