Submitted by Karoliina Maikola and James Hobbs of Safegrid
Middle Tennessee Electric, one of the largest electrical cooperatives in the United States, installed Safegrid sensors for a pilot in the Murfreesboro, TN area on a circuit. After installation, a strong, continuous partial discharge signal was noted in an area of the circuit as seen below. Using the analytics tool, we can also see the levels and times of the PD signals inside the red box.
the challenge
The noise indicated a potential fault, but the exact cause and location were unknown. GridGuardian, a cloud-based real-time grid monitoring system, showed a potential issue developing, but some additional investigation was needed.
Using some of the other tools available, Middle Tennessee Electric engineer Caleb Bates and James Hobbs, the US technical specialist from Safegrid, began to look at the issue and how best to determine its cause.
James recommended using either a thermal or Partial Discharge detection camera on devices in the area. Caleb first went to the satellite view on GridGuardian to see if poles in the area could have devices causing the signal as shown below.
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solution
Once the poles in the area (shown in the green and red boxes above) were identified, Caleb went to the site and used a customer-owned infrared camera, which allowed Middle Tennessee Electric to identify a hot lug at a disconnect switch, indicating a hotspot.
To confirm the issue was indeed causing this case of Partial Discharge noise, the circuit was switched out, and the offending disconnect was opened. This resulted in the noise from this particular area stopping, as shown below.
results
By detecting the hotspot early, Middle Tennessee Electric was able to identify and correct the loose connection promptly, preventing a larger failure. The ability to predict and locate this unseen fault saved the utility both time and money, as potential service interruptions were avoided, and repair efforts were minimized. A potential outage would have taken around 1600 households offline.
“The Safegrid solution proved invaluable to us, allowing timely, proactive maintenance and safeguarding against future issues”, said Bates.
