"High-voltage power lines can be just as safe as the electrical wiring in our homes — or just as dangerous. The key is learning to act safely around them.” — BPA Living and Working Safely Around High-Voltage Power Lines handbook
Maintaining a high voltage site, such as a substation or switchyard, is dangerous work. Whether it’s a 110-volt home wiring or a 500,000-volt power line, electrical installations must be treated with the utmost respect and caution. While anyone working on a high voltage project site has been trained in safety practices, it’s best to brush up on safety protocols for lines between 69,000 and 500,000 volts. That’s why we’re writing this three-part series to help you review high voltage safety practices. This week, we’ll brush up on right-of-way, overhead power lines, nuisance shocks, irrigation systems and underground installations.
1. Keep the right-of-way clear
The best way to ensure safety and prevent accidents is to keep the power line right-of-way clear. Although crops under 10 feet and other specific allowances are permitted, no permanent structures of any kind can block the right-of-way. In fact, it’s best to keep the right-of-way completely clear if possible.
2. Avoid getting too close to an overhead power line
Because power lines conduct such high voltage, currents can jump air gaps and conduct through nearby objects. The amount of voltage and the air gap distance is directly related. Best practices dictate against trying to calculate air gap distances, and sets 14 feet as the maximum above ground safety height in the right-of-way. Vehicles and equipment under 14 feet are operable, but cranes, lifts, and other vehicles that can exceed the 14-foot limit should exercise increased caution.
In addition, the 14-foot limit is calculated based on the ground elevation at the time the power line was erected. Increasing the ground elevation inside the right-of-way is strictly prohibited.
3. Pay attention to and avoid nuisance shocks
Even if you’ve never experienced a nuisance shock, they’re very real. "Nuisance shocks” are what happens when a vehicle, fence, metal building, roof or irrigation system is too close to a power line (within the air gap). When this happens, maintenance personnel working in these vehicles and buildings or touching these objects may feel a nuisance shock similar to static shock.
Whenever you feel a nuisance shock, it’s a good sign that you’re operating too close to the power line or tower. You should immediately distance yourself and reassess your options. If you feel nuisance shock within a building, you should report it for inspection.
4. Properly manage irrigation systems
Modern irrigation systems involve a lot of sprinkler piping that could interact with conductive power lines and towers.
Since they contain running water, this could be extremely dangerous for anyone working on the site. In order to avoid irrigation system conductivity, pipes should be handled with properly insulated equipment, and should always be carried horizontal to the ground (never vertical) during installations and repairs. Spray pivot points need electrical grounds as well. Additionally, sprinkler lines should always run perpendicular rather than parallel to power lines.
5. Properly manage underground pipes and cables
Underground pipes and cables (including telephone and electric cables) are still susceptible to electrical interactivity with power lines due to unpredictable factors like insulation degradation, rain and proximity to towers or power lines.
In order to prevent shorting or overcharging of telephone and cable lines (which could be dangerous for households), pipes and cables should never be installed within 50 feet of a tower. Any underground pipes and cables must be located before installing underground utilities.
Next week, we’ll go over fences, wire fences, electric fences, buildings and vehicles.
Beta Engineering has over 40 years of experience exceeding customer expectations on turnkey high-voltage substation and transmission line projects. With our engineering, procurement and construction experience, we provide an unbeatable EPC approach to projects with an expert team of veteran engineers.