Add Ultrasound to Electrical Inspections

Relying solely on infrared thermography for electrical inspections can be risky. While an IR camera can identify faults that produce heat signatures, airborne ultrasound instruments can detect those that don’t generate heat.

With regard to inspection of energized electrical equipment, the first technology that often comes to mind is infrared (IR) thermography.

That’s because IR traditionally has been the tool of choice for identifying potential electrical faults. But, according to Adrian Messer of UE Systems, Elmsford, NY (uesystems.com), relying on a single technology for this task can be risky. The fact is, some electrical faults don’t produce heat signatures that an IR camera will detect. “Here’s where airborne ultrasound comes in,” Messer said. He offered the following overview of why and how.

Airborne ultrasound has seen a large increase in the number of users who combine it and IR to inspect energized electrical equipment. Many operations already leverage the technology for compressed air and gas leak detection. Fortunately, the same instrument used for airborne leak detection can be used for electrical inspections.

There are four main reasons for using ultrasound to inspect energized electrical systems.

Safety

Energized equipment doesn’t need to be opened. Performing an ultrasound scan prior to opening the equipment can help alert the inspector to potential problems such as corona, tracking, and arcing. This reduces the risk or chance of an arc flash occurrence. 

Detecting faults that don’t produce heat

Corona discharge typically doesn’t produce enough change in temperature to be detectible with a standard IR camera. It does, however, produce high-frequency sound that can be heard with an ultrasound instrument. By combining ultrasound and IR, an inspector is able to find any potential electrical fault that may be present.

Recognized standards 

Standards such as NFPA 70B, which deals with the inspection and maintenance of energized electrical equipment, now make mention of using ultrasound and infrared together for a multi-technology approach. 

Advancements in technology 

Because ultrasound has advanced beyond just what the inspector hears in the headset, as well as evolved beyond just a decibel-level readout, users are now able to diagnose the exact nature of a fault. Advanced instruments have capabilities that allow recording of sound from a detected anomaly and analysis of the recorded-sound file in spectrum-analysis software. Corona, tracking, and arcing faults each have signature characteristics that will be present in either the FFT or time wave form when the sound file is analyzed. EP

Adrian Messer is manager of U.S. Operations for UE Systems, Elmsford, NY.  For more information on ultrasound applications and solutions, visit uesystems.com.