GE MagneBlast Breakers

[goofydog]

would appreciate some help (verbiage) with an argument to replace my old 5kV MagneBlast breaker line-up with a new arc flash rated vacuum bottle line-up. breakers have been "sort of maintained" over their 35+ years - but the bus has really never been down for inspection/cleaning due to the process and system configuration. can anyone give me some ammo for my business case?

thanks!

 

[BJC]

I can't help you, new for the sake of new is throwing money away. Find a good service company that can come in check it out and replace/ rebuild it.
20 years ago it would have been GE IS&E. Cutler Hammer will probably do it. There are others out there but you should check the jobs they have done and their references.
Depending on the size of your gear you might save enough money to pay your salary for 4 or 5 years.

 

[dpc]

It's difficult to make a purely business case for this. If switchgear problems are causing downtime, that cost can be calculated. But if it is a concern over a possible future catastrophic failure, that is tough to quantify. It is possible to buy vacuum breakers that will directly replace the air breakers you now have.

Arc-resistant switchgear has some limitations. It is only arc-resistant when the door are closed and latched. Also, it will be necessary to vent a large exhaust duct to keep the blast pressure down. Sometimes this is a problem in existing facilities.



David Castor

http://www.cvoes.com

 

[oldfieldguy]

Magne-blast gear is good stuff. Properly maintained, I think "forever" might fit the blank for "life expectancy". A good service company versed in maintaining this gear can do wonders for further reliability.

As to arc-flash issues, there are remote racking devices available for this equipment, and remote control operation is pretty easy. This will give a bit better margin of safety for the old line-up.

Replacing the entire line-up of working equipment with something for the sake of "arc-flash", well, that depends on how excited your management gets about the safety aspects of arc-flash issues. They will have to put their own number to that, because if your Magne-blast gear is still working, there's an order of magnitude difference in refurbishing the old gear and replacing it with the new stuff.

old field guy

 

[Zogzog]

GE really messed up when they built the magneblast line, they built them so well they will last forever if maintained, thier accountants hate those breakers.

I get calls on these all the time, wanting to replace these because they are 50 years old, why replace something that has lasted that long without issues with something that wpn't last 20 years?

I specilize in these, we remanufacture them and provide roll in vaccum replacements.

 

[manning225]

I agree with those suggesting re-furb rather than replace. Whoever does your maintance make sure thay give a once over on a regular basis for excessive partial discharge. Trip timing test are also good for the mechanics if they can be done on this type of switch (anyone got experience?) That will make you sleep easier at night.

 

[oldfieldguy]

Manning225 brings up a good point. Somewhere in twenty or thirty years after manufacture, the grease in several important roller bearings hardens and tripping can become erratic. The bearings need to be disassembled, cleaned and lubed. This is to be expected for a mechanical assembly that has been in service for decades.

Trip timing tests as well as trip current profile tests show these problems.

Much of the partial discharge issue comes about from aging insulation cracking and tracking. The tracking can be mitigated by inspection and good, thorough cleaning.

old field guy

 

[Zogzog]

EPRI requires nuclear plants to rebuild the mechanisims every 10 years, full disassembly is the only way to propery re-lubricate the mech.

 

[rcw retired EE]

What about the asbestos arc chutes on the older breakers? Is there a benefit in eliminating asbestos components by swapping out breakers?

Investigate upgrading the relaying to modern digital relays. You might be able to reduce arc flash for parts of the gear by implementing zone interlocking schemes that are not possible with old relays.

 

[mns15451]

There are basically two type of problems with these breakers. The operating mechanism of the Magne-blast C.B and the arch-chutes. The operating mechanism is so much complicated and conjusted that you hardly have space to perform maintenance of parts like cams, bearings, rollers etc. These parts play the main role in the opening, closing and timings of the breakers. Indeed its possible to replace or maintain these parts (I have done several times on 13.8 Kv breakers) but its quite time consuming and require expertise/accuracy. I doubt that there are experts avail even with GE to overhaul these breakers in the real sense.
The second aspect i.e. the arc-chutes are made of asbestos. Asbestose causes skin cancer and has been band internationally. We should therefore take extra care while cleaning the arc-chutes. Special oxygen masks, I would suggest to be used by the maintenance staff.
I would therefore recommend and it will be far more economical to replace all these magne-blast breakers with Vacuum power or Power/vac replacement or retrofit breakers brought forth by GE or other vendors. These are direct replacement breakers and requires very little commissioning times.Hope this will assist to make up your mind.

 

[Zogzog]

Our shop is certifed via 10 CFR appendix B to refirbish these in a nuclear safety related program, they are actually some of the easier mechanisims you will find. So there are experts in overhauling these, and many other breakers.

These mechs have less issues than most VCB's, they were made back in the day we overdutied stuff.

Perhaps the biggest issue people have with these in the bottles in the gear, the potting that was used is a very common failure point and using a VCB as a replacement does nothing to address this issue.

THe biggest advantage to a VCB replacement is the reduced weight of the VCB, minimizes stress on the elevating mechanism, another common failure point.

 

[abeltio]

Did you talk to your insurance company? what is their take on this?

Many sites base their inspection/maintenance requirements based on the agreements they reach with their insurers to maintain a low premium.



saludos.
a.

 

[norcalnewb]

One of the biggest problems I have seen with these breakers is they get hung up in the cell. I used to work at a facility that had several line-ups of the gear. They performed routine maintenance on the gear and still had repeat issues of the breakers getting hung up. Someone then had to physically force the breaker to drop, not exactly what I consider a safe operation. Later, I worked for a company that made replacement breakers for the Magne-Blast, and that seemed to be common theme there as well.

I will admit that I haven't seen too many cases where a breaker failed except in cases of extremely poor maintenance, but I still prefer horizontal racking breaker.

 

[dpmac]

We seem to have a large percentage of customers with MagnaBlast breakers. Most are 15kV, 1000MVA (ML13 mech). There were a few variations, but for the most part they are the same. I agree with those who say to do it right they must be disassembled every 10 years or so. I have seen firms attempt this in the field and its not pretty. I know many firms who can do it in the field, but they know better. (I am talking about guys on their knees looking for lost parts in a dim lit substation, not qualified mechanics in a well lit fully equipped mobile shop).

Interesting about the timing comments. I believe there is documented information (Zog?) detailing Magnablast breakers not latching closed because the new style greases now used allow the breaker to operate TOO fast.

I have seen early vacuum retrofits get stuck in the cells because they were TOO light and held in place due to primary contact tulip spring pressure. The early (80's) vacuum retrofit breakers were scary. Those companies that did them well still do. Those that did not got out of it (thankfully).

Zog made a good point about the primary bottles. If any of your breakers have dark colored tar substance dripping on the primary poles your simple breaker rebuild or retrofit project just got harder, longer and more expensive.