Breaker Temperature-rise tolerance on bolts

[sheryl86_ann]

Greetings!

I would like to ask if anyone can direct me to a website leading to the common standard temperature for circuit breakers use in industries.

For short background why I need. We did a shutdown activities on substations including breakers re-tigthening on bolts using standard torque requirements. As part of the activity, we did temperature reading data on "before and after temperature" on its bolts. Now, aour ambient temperature is around 31 degree celcius. Common data recorded is around 30 to 33 degree celcius.

This time, we are using same "parameter" / standard our client has which is " Before and after temperature reading must be LESS THAN the [ambient temperature + 30 degree]. Now, I need to know where this statement is from and what reference is this.

We did not took the running current of this breakers for our target is with bolts rise temp/ shutdown though.

Thank you very much.

Sincerely,

Sheryl Ca?o
Philippines

 

[Smart $]

Can't answer your question as posed... but >this here document< has a little information on testing standards for listing purposes here in the US.

 

[G._S._Ohm]

1 common standard temperature for circuit breakers use in industries.

2 As part of the activity, we did temperature reading data on "before and after temperature" on its bolts. Now, aour ambient temperature is around 31 degree celcius. Common data recorded is around 30 to 33 degree celcius.

3 This time, we are using same "parameter" / standard our client has which is " Before and after temperature reading must be LESS THAN the [ambient temperature + 30 degree]. Now, I need to know where this statement is from and what reference is this.

Hello, Ms. Ca?o:

I hope this helps. . .

1 Is this the high limit for the ambient temperature?

2 Loose bolted connections passing current will cause local heating due to increased contact resistance.
Apparently the maximum temperature rise you measured was 2 C above ambient. Since ambient was 31 C, the 30 C reading must have been a measurement error of - 3%.

3. I can't imagine bolts that are tight would cause a 30 C rise above ambient.
Maybe this is due to the breakers internal resistance while passing current. A 20 A breaker that I measured had a 2 W internal resistance wire to actuate the thermal trip.
This +30 C pass/fail specification was probably calculated to include 95% or 99% of the breakers that get shipped.