Circuit breakers maintenance tests

[denvar]

Hi we usually carryout breaker timing and contact resistance every year for HV, MV & LV breakers. We usually compare results with commissioning values just to confirm they not too off. Sometimes we don't get the commissioning values hence the queryCan somebody kindly advise on standards for timing values and contact resistance for breaker based on reputable standard IEC/ANSI/FIST etc. Especially advise on maximum pole discrepancy allowed for each kind of breakers

 

[rlundsrud]

Millionth drop testing at 24 volts using the current rating of the breaker is the standard for breakers. You would need a 24 volt power supply that can provide hi current and a load bank that can handle that current. I think you can look at the ansi standards for that testing.

 

[denvar]

Millionth drop testing at 24 volts using the current rating of the breaker is the standard for breakers. You would need a 24 volt power supply that can provide hi current and a load bank that can handle that current. I think you can look at the ansi standards for that testing.

We have breaker analyzer test equipment and DC resistance testing equip. Query is what values are ok ( margins) where commissioning values are not available.

 

[zog]

Millionth drop testing at 24 volts using the current rating of the breaker is the standard for breakers. You would need a 24 volt power supply that can provide hi current and a load bank that can handle that current. .

What standard are you referring to?

 

[GoldDigger]

Millionth drop testing at 24 volts using the current rating of the breaker is the standard for breakers. You would need a 24 volt power supply that can provide hi current and a load bank that can handle that current. I think you can look at the ansi standards for that testing.

I assume that "millionth" is ought-to-correct for "millivolt" or something similar.

 

[templdl]

Have you actually asked a breaker manufacture what they recommend? Each time a breaker is opened and closed the results will change as well as the under actual operating conditions. It is not all that uncommon for those to want to go to a table of numbers that test results are to fall within and then make a judgement to pass or fail.
The tests should not be used objectively but be used subjectively. Any questionable results should be used to justify further evaluation as nd not as a basis for rejection.

 

[templdl]

NEMA AB4

NEMA AB4

Get a copy of NEMA AB4, Guidelines for inspection and preventive maintenance of molded case circuit breakers used in commercial and industrial applications.
For insulated case, power, and medium voltage breakers etc I know that the manufacturer that I had worked for had excellent maintenance instructions for their product.
Should yu ou follow the manufactures recommendation it makes it a whole lot easier when you consult with the manufacturer when addressing issues regarding their product. I saves a bunch of time rather than filling another procedure/method and then have to go back and follow what the manufacturer has recommended.

 

[ATSman]

LV breaker white paper

LV breaker white paper

http://www.eaton.eu/ecm/groups/public/@pub/@eaton/@corp/documents/content/pct_1104261.pdf

 

[templdl]

http://www.eaton.eu/ecm/groups/public/@pub/@eaton/@corp/documents/content/pct_1104261.pdf

Excellent! I'!! Print it out so I can review it farther. EATON does have and always has had some top engineer That series C breaker in the pics was originally designed by Westinghouse engineers back in the '80s and released in the 90s as ,I casn recall.

 

[denvar]

Have you actually asked a breaker manufacture what they recommend? Each time a breaker is opened and closed the results will change as well as the under actual operating conditions. It is not all that uncommon for those to want to go to a table of numbers that test results are to fall within and then make a judgement to pass or fail.
The tests should not be used objectively but be used subjectively. Any questionable results should be used to justify further evaluation as nd not as a basis for rejection.

We have manufacturer information for some breakers but for some we dont hence the query. eg what are the accepted ranges of contact resistance before you conclude internal servicing or repair is required? How much discrepancy between poles should indicate serious problems? For so
me old breakers getting manufacturer assistance in this part of the world is difficult

 

[big john]

Honestly, I think a lot of this is just experience-driven. Some things like travel times will be provided from each manufacturere, but good luck getting that for a lot of older LV breakers, so what do you use if not judgement?

NETA publishes very generic evaluation criteria for some stuff, like investigate any pole with a contact resistance >50% higher than the others, but even that is subjective. I wouldn't lose a wink of sleep passing a breaker where one pole wad 9 microohms and the other was 20.

FIST publishes some actual hard values in their maintenance guidelines if you preger those.

A lot of it is simply comparing values to other phases and othe similar breakers and seeing what jumps out at you. A contact resistance of 300u wouldn't phase me on a small MCCB but that would be condemable on a large frame ACB.

 

[templdl]

We have manufacturer information for some breakers but for some we dont hence the query. eg what are the accepted ranges of contact resistance before you conclude internal servicing or repair is required? How much discrepancy between poles should indicate serious problems? For so
me old breakers getting manufacturer assistance in this part of the world is difficult

Contact resistance shouldn't be used to pass or fail a breaker by. It may be used to justify a further investigation. Every time that you open and close a breaker the contacts actually rub against one another which changes the resistance across the contacts. In addition contact resistance is often measured with a meter that uses a voltage which is much lower than a breakers actual operating voltage.
In addition the actual current path travels not only from the line terminals to the stationary contact through the moving contact but also travels through the trip elements and finally to the load end terminals. There have been in occasions where a braised connection may have been defective resulting in high resistance in the current path.
When checking a breaker for integrity it is best to keep an open mind and varify any test results.
Remember there are those who simply would like to go by numbers which makes it easy for thern to pass judgement, that is using an objective evaluation rather that a subjecting evaluation which is based upon fact reason asn logic by applying actual expertise and actual electrtical/practical knowledge.

 

[topgone]

Contact resistance shouldn't be used to pass or fail a breaker by. It may be used to justify a further investigation. Every time that you open and close a breaker the contacts actually rub against one another which changes the resistance across the contacts. In addition contact resistance is often measured with a meter that uses a voltage which is much lower than a breakers actual operating voltage.
In addition the actual current path travels not only from the line terminals to the stationary contact through the moving contact but also travels through the trip elements and finally to the load end terminals. There have been in occasions where a braised connection may have been defective resulting in high resistance in the current path.
When checking a breaker for integrity it is best to keep an open mind and varify any test results.
Remember there are those who simply would like to go by numbers which makes it easy for thern to pass judgement, that is using an objective evaluation rather that a subjecting evaluation which is based upon fact reason asn logic by applying actual expertise and actual electrtical/practical knowledge.

In my other life, we schedule regular thermograph scans on all the MCC breakers and switchgears to have an advance idea of which circuit breaker are about to fail. Most results we found out were terminal screw looseness. We did find one instance where the braided jumper from the moving contact of a breaker showed abnormal heating. Whenever we see signatures of abnormal heating on breakers, we also include investigations on the existing loads.
Just my two cents.

 

[johnmeto]

Millionth drop testing at 24 volts utilizing the present rating of the breaker is the standard for breakers.

 

[templdl]

In my other life, we schedule regular thermograph scans on all the MCC breakers and switchgears to have an advance idea of which circuit breaker are about to fail. Most results we found out were terminal screw looseness. We did find one instance where the braided jumper from the moving contact of a breaker showed abnormal heating. Whenever we see signatures of abnormal heating on breakers, we also include investigations on the existing loads.
Just my two cents.

A very good practice. What I have recommended is that this be done of a scheduled basis keeping a log of the results. By comparing the history a trend could be established in order to schedule preventative maintenance.

 

[templdl]

Millionth drop testing at 24 volts utilizing the present rating of the breaker is the standard for breakers.

I doubt if your results we could be a satisfactory way to address a warranty issues with as breaker manufacturer. Iwas an sales asnd applications engineer fora majoy breakrer manufacturer and the test which to referring to is not something that is included for the evaluation of their breakers. Every time a breaker is opened and closed that vaslue will change and it if far less that the 120/208/240//277/480v actual operating voltages.
But having a go nogo number to go buy makes it simple for them recognition to pass of fail a breaker. This I have referred to as an objective test. It takes the thinking out of it.
When it comes performing an evaluation that is where an experienced tech/electrician makes a subjective evasluation based upon their knowledge and experience.