Circuit Breaker Testing

As part of an ongoing UPS upgrade system being carried out by Metropolitan Electrical Services we were called in to ‘listen’ to a molded case circuit breaker feeding UPS equipment on one of the floors of a multi-floor data centre. The engineers carrying out the installation suspected that the circuit breaker was faulty as it was making a very slight audible hum/rattle. The breaker was a critical part of the temporary supply system and would be called on to feed the equipment from the alternative supply in case of a power failure.


With a test load applied to the breaker we listened to and recorded the ultrasonic emissions. We were able to analyze the sound file on our Spectralyser software and determine if there were any signs of internal degradation of the contacts within the device. The test and analysis is totally nonintrusive and nondestructive. The stethoscope module is placed on the external surface of the breaker. We also recorded sound files from similarly loaded devices for comparison and to establish baseline ultra sound levels for the breakers.


We were able to distinguish between the audible sounds heard during the testing and the ultrasonic emissions heard when listening with the Ultraprobe. The Audible noise coming from the breaker was unrelated from the ultrasonic signature although the circuit breaker was deteriorating due to internal arcing of the contacts within. 


The circuit breaker was replaced before the new UPS system went online.


As the defect was found and replaced during testing it did not have any impact on the overall schedule and the temporary supplies were able to be connected before the UPS system went live.

  • Case study overview
  • Client: Telstra
  • Sector: Data Centers
  • Disciplines: Ultrasonic Testing,
  • Duration: 2

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