Hitachi and I think Siemens has 72.5 class dead tank breakers available in vacuum. Not sure if anyone else does (yet). We've been keeping a bit of an eye on the 3M Novec stuff, which is what GE is marketing as their g3 technology, but aren't anywhere near purchasing any.
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...
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...
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...
buzzp brings up a good caution - but I would go one further and say do not try this with current going through the ct. CT circuits should not be disturbed while in service. Especially if you are not familiar with how to use simple test tools to perform this check. Open CT circuits are very...
Thanks Lionel.
djs - I'm under the impression that only very small transformers use this technique. I've measured the ratio of transformers from 500 KVA to 200 MVA with accurate instruments (eg TR-800) and they're often within 0.1% of calculated using nameplate data. Can anyone confirm this?
From my understanding, the inrush issue on a back-fed transformer is primarily due to the winding configuration/positioning. The winding expected to be energized first (wouldn't necessarily be the pri but we'll assume that it is), is physically on the outside of the secondary winding. I'm sure...
HamburgerHelper - No, I'm up in Canada - toured the great lakes this fall and heard some discussions at a few wineries along the way, interesting stuff.
We run primarily mixed gas breakers here (almost all SF6/CF4, with a few /N2's kicking around still).
Manitoba's take on it while I'm posting...
Happened across this document which seems relevant - some discussion about breaker electrical characteristics as well as different control/mitigation philosophies at reduced SF6 pressures.
Link
marks1080, I'm looking at a schem for an older 145PM40-20 here, but I have the 63-1, -2, -3 pressure switches along with a 33 (spring charge limit switch)all paralleled. These pick up a 63AX which opens a normally closed contact in the CC, TC-1, and TC-2 circuits (lockout on low gas or low...
marks1080:
Absolutely, the old air blast experts are in short supply, but there's still some around; we're also on the track to remove all ours, one would HOPE within the same timeframe, but you know how that goes....
Mbrooke:
Tripping via healthy breakers is absolutely necessary in the case...
Absolutely, and exactly why I've been lurking around this site for years.
My 63-2's show the trip cct being blocked open (both cct's of course). Interesting indeed - I agree, our companies could have spec'd as such, I'm in support, not supply - but I will be enquiring when I get a chance.
I...
Ok, my miss-reading of your comment on breaker fail "initiation". Fair enough.
As for the tripping at low-low - I would not consider low-low to be near a point where there is "low or no SF6". Especially the NO SF6 part. I agree, at low-low they will still trip adequately; if they didn't then...
Can you provide some further information on this one? It's something I've never come across before and I'd be surprised if any breaker manufacturer would stand behind that statement.
The only time I've seen coils burn up is because the breaker failed to operate at all (mech problem, coil fell...
