Insulator Washing
Another common practice is to utilize helicopters for
insulator washing. Again, this is a method that allows for the line to remain
energized during the process.
The helicopter carries a water tank that is refilled at a
staging area near the work location. A hose and nozzle are attached to a
structure on the helicopter and are operated by a qualified line worker who
directs the water spray and adequately cleans the insulator string.
Again, with the ease of access afforded by the helicopter,
the speed of this operation can result in a typical three-phase tower being
cleaned in a few minutes.
Inspections
Helicopters are invaluable for tower line and structure
inspections. Due to the ease of the practice and the large number of
inspections that can be accomplished, utilities have increased the amount of
maintenance inspections being done, thus promoting system reliability.
Helicopters typically carry qualified line workers who
utilize stabilizing binoculars to visually inspect the transmission tower for
signs of rusting or weakness and the transmission hardware and conductor for
damage and potential failure.
Infrared inspections and photographic imaging can also be
accomplished from the helicopter, either by mounting the cameras on the
helicopter or through direct use by the crew. During these inspections, the
helicopter provides a comfortable situation for accomplishing the necessary
recording of specific information, tower locations, etc.
In addition, inspections from helicopters are required
following a catastrophic event or system failure. It is the only logical method
of quickly inspecting a transmission system for the exact location and extent
of damage.
Helicopter Method Considerations
The ability to safely position a helicopter and worker at
the actual work site is the most critical consideration when deciding if a
helicopter method can be utilized for construction or maintenance. The terrain
and weather conditions are obvious factors, as well as the physical spacing
needed to position the helicopter and worker in the proximity required for the
work method.
If live-line work methods are to be utilized, the minimum
approach distance required for energized line work must be calculated very
carefully for every situation. The geometry of each work structure, the
geometry of the individual helicopter, and the positioning of the helicopter
and worker for the specific work method must be analyzed. There are
calculations that are available to analyze the approach distances (IEEE Task
Force 15.07.05.05, 1999).
When choosing between construction and maintenance work
methods, the safety of the line workers is the first consideration. Depending
on circumstances, a helicopter method may be the safest work method. Terrain
has always been a primary reason for choosing helicopters to assist with
projects since the ability to drive to each work site may not be possible.
However, helicopters may still be the easiest and most
economic alternative when the terrain is open and flat, especially when there
are many individual tower locations that will be contacted. Although helicopters
may seem to be expensive on a per person basis, the ability to quickly position
workers and easily move material can drastically reduce costs.
When live-line methods can be utilized, the positioning of
workers, material, and equipment becomes comparatively easier.
Finally, if the safe use of the helicopter allows the
transmission systems to remain energized throughout the project, the helicopter
may be the only possible alternative. Since the transmission system is a major
link in the competitive energy markets, transmission operation will have
reliability performance measures which must be achieved.
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