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General Powerline Inspections

The first thing that utilities need to agree on is why they should patrol their transmission lines. Is it because it’s mandated by the state’s public utilities commission? Is it because the board of directors thinks we should be doing it to “keep up with the Jones’”? Is it something company executives want done to do to absolve themselves of liability or to shift responsibility?

It should be to gather information about the condition of the transmission lines. (In this context, “lines” includes the right-of-way.) If that’s not the reason, then the inspection can simply be done by the cheapest means. If the reason is to gather information, that is probably where the process should begin. What information is needed? Who will be using it and for what? In larger utilities, there may be several departments that need this information. For instance, the forestry department will want to know the condition of vegetation along the right-of-way for planning and reclearing purposes as well as to mitigate immediate issues. The people responsible for right-of-way maintenance will want to know what is located on their right-of-ways, including encroachments and indications of approaching encroachments. The group responsible for O&M will be interested in current damages that need to be repaired based on the extent and nature of damages. It’s also necessary that planner/schedulers that work with inhouse maintenance as well as contractors have this info. It may be determined that a line needs to upgraded or replaced, in which case the capital construction people must get involved. So the condition of transmission lines affects everything in the transmission department, and in order for it to operate efficiently it needs accurate, detailed, and timely information. Otherwise you know what they say: garbage in…garbage out.

Another thing they say is: “you can pay me now, or pay me later.” Or how about “an ounce of prevention is worth a pound of cure.” Banding a cracked crossarm is quick, easy, cheap and may extend the operational life of the crossarm by decades. If not repaired, that crossarm will further degrade may eventually result in an a locked-out line, angry rate payers, loss of revenue, and a much more expensive emergency repair. Most reasonable people would agree that not knowing the conditions of the lines is not a good strategy. The adage: “what you don’t know won’t hurt you” is probably not the one that you should go with.

Management should not only mandate that inspections be carried out, but should state the purpose along with expected product of the inspections. The last thing that those responsible for doing it should feel is that all they are doing checking a box to cover the boss’s butt.

Personnel tasked with actual line inspection should be knowledgeable in all aspects of transmission line conditions including:

  • An understanding of the company’s attitude and policies toward various conditions and situations. An example would be an old barn built on the edge of the right-of-way which is probably grandfathered in. If that same barn was in the early construction phase, it should probably be removed. Or a deer stand located on the right-of-way might be permitted as long as it wasn’t attached to utility property, and it didn’t compromise minimum conductor clearance requirements, and didn’t interfere with line and right-of-way maintenance. Another example might be something that could result in a liability issue. In that instance, contemporaneous photographic evidence would be helpful. Or maybe in some instances—such as a logging operation working along the right-of-way—counseling caution to the workers might be appropriate.

  • Being fluent in the company’s terminology and having a basic knowledge of construction standards and minimum acceptable conditions.

  • Being able to identify discrepancies and determine whether they meet the threshold of something that should be mitigated. They should be knowledgeable enough with repair methods to suggest what would appropriate.

  • Being able to accurately prioritize any damage that they find. This prioritization should be clearly defined in the company’s deliverables requirements. The inspector should clearly understand the company’s policy regarding aggravating and mitigating factors, and apply it to arrive at the final damage priority assignment. He should understand when and why photographic documentation is required, and what photographs are needed and how to create the most effective shots.

  • For vegetation issues, the inspector should have basic forestry knowledge such as common species of vines and floor brush along with growth rates and maximum heights. With respect to danger trees along the edge of the right-of-way, they should be able to recognize individual tree health and integrity as well as problems the species’ typically causes. It is important to understand general growing conditions for terrain type and time of year, and be able to assign a mitigation response time. The inspector should be familiar with FERC standards and terminology when describing right-of-way conditions.

It goes without saying that anyone tasked with working around transmission lines and stations have a basic understanding of high voltage characteristics including conduction, induction, insulation, and arcing distances.

The deliverables defined by management should be specific, measurable, and have practical mitigation limits.

Inspectors assigned to outage/operation investigations should have a deeper depth of knowledge with respect to understanding the behavior of high voltage electrical transmission in order to narrow the

potential outage causes. These should include, but are not limited to:

  • Basic insulation level of various transmission structure components

  • Vegetation conductivity

  • Lightning behavior and consequences

  • Insulator types and construction

  • Arcing factors and distances

  • Ionization levels and causes

  • Atmospheric conditions conducive to arcing

  • Bird and other animal behavior

  • Insulator contamination types and conductivity

  • Disguise methods and techniques

Inspectors should have an inquisitive nature that is challenged by mystery solving, which may require thinking outside the box. Prior to beginning the investigation, the investigator should endeavor to ascertain as many of the following clues as possible and formulate his investigation plan of action.

  • Transmission Line – Voltage, line age, construction materials, construction type, foundation type, terrain type(s)

  • Fault type – Phase(s)-to-ground, phase-to-phase(s), phase imbalance, open circuit

  • Fault phase – Phase identification, location considering transpositions

  • Time-of-day – Bird activity, human activity, temperatures, humidity, electrical loads

  • Time of year – Agricultural activity, bird migrations, vegetation growth rates, electrical loads,

  • Atmospheric conditions – Temperature, humidity, wind, ice/snow loads, thunderstorm and/or lightning activity, tornadic/microburst activity

  • Agricultural activity – Planting equipment, harvesting equipment, aerial spraying, stubble burning

  • Line loading – Arc distance, conductor sag,

  • Terrain – Agricultural, ranching, marsh/wetlands, steep grades, bird types and habits, span length and conductor sag, span length and static wire loading, erosion, logging, construction

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