Circuit Breaker lugs temperature monitoring 1

[newdryno]

Trying to find a suitable way of monitoring the lug temperatures of a ~1000V circuit breaker. I see that infrared pyrometers are quite common but that simply won't work in this case. I'd like direct contact rather than monitoring the air temperature near the lugs however the obvious problem is isolation from high voltage & current. However medium voltage generators and motors monitor winding temperatures with RTDs so I thought this would be a possibility. I see one manufacturer's data sheet for a thin film RTD for slot insertion and it's dielectric strengh is shown as 3200V. Has anyone tried this method of monitoring, say on bus bars? Any suggestions are greatly appreciated.

 

[ScottyUK]

Pleased you got a solution, newdryno. So often we hear nothing about whether an idea worked or not, so thanks for the feedback!


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If we learn from our mistakes I'm getting a great education!

 

[waross]

A comment on temperature ratings of devices;
We had a model specific issue with a temperature controller. We found a possible replacement but the replacement was for indoor use and the application was outdoors in Ontario, Canada. The price was low so we purchased a replacement on speculation and did some testing. We found that as the ambient temperature dropped below the rated minimum temperature, found that the instrument error was equal to the temperature difference between the actual temperature and the minimum rated temperature. We decided that if the unit was overheating when the ambient was that cold that it may be an advantage to get an alarm signal at a little less than the normal set point. We put the replacement in service and never had an issue.
The point is:
When a device is used below the minimum rated temperature what happens? If the only effect is a shift in calibration, is the shift acceptable in the proposed application?


Bill
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"Why not the best?"
Jimmy Carter

 

[newdryno]

In our case we contacted the manufacturer and asked what would be the effect(s) of operating their device in an ambient outside their published temperature range. We had this situation many times with manufacturers of various components. Most of the time the manufacturer could not or more likley didn't want to provide a definitive answer. In the case above we took the temperature relay to a testing lab and did it ourselves. Incidentally, for many components with LCD displays the lower ambient temperature rating is just the lower limit for LCDs; the more important functionality of the component will perform fine below their advertised low limit.