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How the DayCor camera saved BPA’s
Bacon
1 out of 3 case studies that demonstrate
the usefulness of the DayCor camera in solving tricky transmission
problems
Don Ruff, BPA Insulator Specialist UGM
2005
The SnoKing-Tap line story:
This 13-mile long transmission
line was built at 500-kV in the 1970’s, in anticipation of population
and load growth in the Puget Sound area but operated at 230-kV until
Sept. 29, 2003.
Landowner noise & customers complaints
Starting on Sept. 29, BPA received many phone calls and emails from
area residents about the line.
Landowners expressed concern over:
- Noise
- Property values and buyout policies
- EMF
- Nuisance shocks
- Health and safety
Investigation:
BPA was pressured by residents and political officials to immediately
take action.
BPA engineers began an investigation that included:
Dozens of noise measurements along the transmission line in various
weather conditions
Close-range tower and equipment inspections
Helicopter corona inspections
Meeting with landowners one-on-one
EMF testing
After analyzing the research and landowner comments, the scope of
the investigation was expanded from the line to include the SnoKing
substation.
Research showed a high level of corona activity on the transmission
line due to it operating at 230-kV for a number of years.
| Helicopter investigation: |
| Two 500 kV lines were built at the same
time. One, Monroe-Custer, was operated at 500 kV. The other, SnoKing
Tap was operated at 230 kV. We used the DayCor via Helicopter
to see corona activity on both lines. |
| Conclusion: |
| The SnoKing Tap line had serious corona
issues and it was a conductor issue not a hardware issue. |
What was found on the conductor:
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Close range photos showed a film
of algae on the conductor.
Over the past 30 years this algae was able to survive at the
lower voltage.
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Dirt “spikes” on the bottom
of the conductor were identified as sources of corona noise,
especially during mildly damp conditions.
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| After cleaning.. |
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What was found on the conductor:
Close range photos showed
a film of algae on the conductor.
Over the past 30 years this algae was able to survive at the lower
voltage.
Dirt “spikes” on the bottom of the conductor were identified
as sources of corona noise, especially during mildly damp conditions.
Results:
Steel brushes cleaned
the line better than expected.
Noise measurements taken comparing the clean span with an unclean
span showed about a 6 dbA reduction.
It was concluded that a general cleaning of the line would reduce
noise enough to have the line perform like similar 500-kV lines.
Conclusion:
BPA engineers were under
the gun to find the problem and fix it. Without the DayCor camera,
they would have guessed that it was a hardware problem.
The DayCor camera pinpointed the problem with the conductor which
reduced the amount of outage time needed to fix the problem.
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