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Ultrasonic War Story No. 80
Partial Discharge & Ultrasound
Video of Corona Transformer Using Ultrasound
Video of CrossWalk Light AM Radio Signal
Partial discharge of switchgear
equipment and in substations can result in "catastrophic damage". Detect, locate and remedy the problem.Ultrasonic inspection for electrical anomalies such
as "partial discharge" has been around for awhile now. However, when I talk to many of you and I feel
you are still not using the ultrasonic receiver to listen for partial discharge such as arcing, tracking or corona. Instead
you are relying on infrared to find a problem. Remember, IR is surface temperature, cabinets need to be opened to be effective.If
you have been around the ultrasonic inspection world for very long and read articles in UPTIME Reliability Magazine,
or you have attended my ultrasound workshops or level I course, then you have heard me constantly remind you that IR
does not detect corona under 240kV either. You have also heard me or read that I suggest the use of an ultrasonic receiver
to scan any and all panels or doors prior to opening and in some cases before entering a vault, man-hole, or entering a substation.The
term partial discharge is widely used when scanning switchgear, transformers, high-voltage cabinets, substations or power
lines for arcing, tracking and corona discharge as well as Transient to Earth Voltage (TEV). Some electricians and
electrical workers describe the use of a different instrument when scanning for partial discharge or Transient to Earth
Voltage (TEV). This other device is sensitive to radio waves operating utilizing a bandwidth of 15-60mhz for detecting partial
discharge.During one of my latest level I classes, while walking the outer perimeter of a substation (outside
the fence of course) and using a parabolic reflector and a long range horn, my students were able to detect partial
discharge in the form of corona above a 13kV Transformer some 30 feet away.
- Video
Link (http://www.ultra-soundtech.com/ust/id7.html) of a sound emitting from Cross Walk Transformer/Control Box and a 13kv Transforner Bushing.
- Have you heard
sounds in your swithgear that were not the usual corona, arcing or tracking sounds?
- Maybe you have heard sounds that were similar to CB Radio squelch (Breaker 19).
- Or with the use of an AM Radio in a substation or along the power lines, you may have heard sounds that were
not the usual arcing, tracking or corona sound.
Using an ultrasound receiver, I have detected tracking in switchgear
using a contact probe. You could hear the tracking start-up, then build in intensity, discharge and start over again. While
the sound was low-level in amplitude, it still could be detected.Transient
to Earth Voltages (TEV) is detectable using ultrasound and the electromagnetic wave receiver operating within a
bandwidth of 15-60Mhz. Both the electromagnetic energy and the ultrasound
inspection can be done with the electrical apparatus or switchgear energized.
NOTE:
The TEV instrumets that I have seen do not detect corona or arcing or tracking unless very close
to the source. Depending upon the voltage being inspected, an ultrasond receiver such as the SDT, CTRL, AccuTrak, or
UE Systems instruments have very little problem detecting corona, tracking and arcing from a distance with or without a parabolic
reflector or long range horn.
Come to my Ultrasound Level I Class to learn more.
