Life of an Electromechinical relay

[cranky108]

Does anyone know a good reference for determining the usable life of an electromechinical relay?

I know we have had to replace some capacitors, but other than ocasusinal failures they seem to be holding up well.

 

[racobb]

They were so well designed, I don't think we know what their useful life is yet. Most of the problems I see are the bearings wearing and causing timing and/or reset issues with the disc.

I am speaking of the IAC and CO units.

Probably see more problems with the older ACR and RC reclosing relays.

Alan

 

[Laplacian]

MIL-HDBK-217F

Is this a protective or control relay? 217F covers control relays. The IEEE Gold Book may also be useful.

http://www.sre.org/pubs/Mil-Hdbk-217F(2).pdf

 

[marks1080]

I've seen some that have been in service since the 50's... They will likely be replaced before they ever fail. Refular maintenance on these relays is necessary though.

 

[dpc]

It's going to depend on what type of relay is under consideration and the service.

David Castor

http://www.cvoes.com

 

[oldfieldguy]

I used to regularly test some GE and Westinghouse protective relays that were in service continuously since the 1940's. After sixty years of service they were still hitting the original curves and functioned perfectly with only an occasional cleaning and I never had to worry about software and firmware upgrades.

Of course when one caught a fault and operated, all it did was drop a little orange flag.

old field guy

 

[marks1080]

The orange flag hadn't faded yet? That is a high quality relay!

 

[lz5pl]

oldfieldguy Did you still keep also the original laptop which have been used for their initial programming ;-)

By the way, I often say that the biggest mistake of relay engineers was when we left design of relay protections to computer guys. The result is 500+ pages User Manual for overcurrent relay !


------------------------
It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[cranky108]

We have someone trying to justify replacing the IAC relays because they are old. So the question needed to be asked.

My coworkers said, 75 years or the span of two protection engineers.

I do believe that in this case the panels included ACR's, which seem morl likely to become jammed due to lack of grease, or hardining of the orignal grease (we'll blame it on poor maintenance).

 

[davidbeach]

You can always replace the ACR with something like the BE1-79A that is a work alike replacement solid state relay without having to replace the IACs. What every you eventually replace the IACs with won't last as long and won't do time overcurrent any better. What the replacement will do much better is a bunch of stuff the IAC can't do - reclose in the same relay - and even better the replacement will provide a whole lot more information about what did, and more importantly didn't, happen for any given event.

 

[racobb]

YEP....Have used the Basler as an ACR replacement on many occasions.

Alan

 

[cranky108]

Once upon a time I used a Basler ACR retrofit, and I had problems with it.
First problem was the ACR case wasen't wired as expected. That corrected, the next time it was called on to reclose, it was burned up.

The replacment we purchased was better to work with.

However they haven't reported any problems yet.
I just don't want to go replacing relays because they are old. I want to see a real reason.

Thanks for your input. This is good information

 

[racobb]

The "old" electromechanical relays did and still do a great job for what they were designed to do....and like was said, I have not upgraded the firmware in one yet either!

Granted there have been many instances where I have needed different curves or functions and could have used a micro based relay, but most of the time they are perfect for the job.

The manufacturers are always pressing to get the latest and greatest set of bugs (firmware upgrades) in all of the existing relays in the field, but I do not do the upgrades unless absolutely necessary. I have upgraded the firmware in relays and had them not operate as advertised. Then I end up flashing it back to the old version. That means that every time I do the upgrade, I am also doing another full commission test....and who needs to be doing that!

The capability of a few cycle delay in the inst is what I miss most of the time.

Alan