POWER LINES
  1. What are transmission lines and why are they necessary?

    Transmission lines are used to conduct electricity between two points. Without high voltage transmission lines, generation would have to be located at or near where the energy is used.

    View Idaho Power’s How We Make Electricity brochure to learn about transmission lines and how power is transmitted to your home.

  2. How does electricity arrive at my home?

    View Idaho Power’s How We Make Electricity brochure to learn about transmission lines and how power is transmitted to your home.

  3. Are transmission lines safe for people to live near?

    Power lines are safe for people to live and work around. However, there are a few safety issues to be aware of:

    • Line breaking – This can happen at any voltage level but is very infrequent and generally occurs when a vehicle collides with a power pole. Safety devices, such as circuit breakers, detect such an event and disconnect power. If protective devices fail, the live power line can pose a serious risk of injury or death if someone contacts it. Always stay away from a downed power line and call the local utility company immediately.
    • Fires caused by malfunctions or animal contact with power lines – Infrequently, a device fails on a power pole and causes it to burn, resulting in a fire. More frequently, a small animal (e.g., bird or squirrel) contacts the power line causing a brush or forest fire.
    • Electromagnetic Fields (EMF) – Wherever electricity is used, EMFs are present.
      • Health - Since the early 1970s, research has been performed to determine if EMF pose health risks. Idaho Power agrees with the overwhelming body of research that shows EMFs are not detrimental to human or animal health.
      • Interference – Modern line design has minimized problems that caused noise or interference in the past. Occasionally, interference is caused by older lines when a piece of equipment is not operating correctly. When a problem does occur, Idaho Power has the equipment and trained personnel to address these issues as required by the Federal Communications Commission.
      • GPS interference – According to a study by the Institute of Electronics and Electrical Engineers (IEEE), power line conductors are unlikely to cause signal degradation to GPS signals. The study noted no loss of satellite signals as the GPS receiver moved across a power line easement. A GPS receiver relies on a dispersed constellation of satellites – at least four and often more.
      • Pivot-irrigation systems - The IEEE conducted a study to determine if EMFs of high voltage transmission lines can interfere with electromagnetically guided cornering systems associated with some center pivot-irrigation units. It was found that 60 hertz magnetic fields of more than approximately 500 mG (Milligauss) are required to cause interference with the operation of one system, which is significantly higher than those found near most high voltage transmission lines.
    • Stray voltage – Stray voltage is different than EMF. Stray voltage develops on the grounded neutral system of a farm wiring or utility distribution system. If an animal touches metal equipment under the right conditions, the voltage on the grounded neutral system will cause a small current to flow through the animal into the ground. Stray voltage may be caused by damaged or improper wiring on the farm or a nearby farm, or on Idaho Power’s electricity lines. Under normal conditions, the voltage is too weak to generate any physical or behavioral changes in the animal.

    For more information about these safety issues visit the Further Reading page and Idaho Power’s Safety page.

  4. Can electromagnetic fields (EMF) from 500 kV lines have harmful health effects?

    EMFs are associated with all electronic devices including computer terminals, television and lights. EMFs dissipate with distance. Idaho Power designs and builds all of its transmission lines so that the EMF exposure at the edge of the right of way is about the same or less than you might encounter under normal home conditions (home electric circuits, lights and appliances). While homes may be adjacent to power line rights of way, few homes actually sit at the edge of a transmission line right of way or easement. Easements for 500 kV transmission lines are 250 feet wide.

    There is an enormous amount of valid, scientific research on this topic and Idaho Power encourages everyone to do their own research keeping in mind that not all studies are considered credible. Some of the more notable organizations where you can find information include the World Health Organization, the National Cancer Institute, the International Agency for Research on Cancer, the National Institute of Environmental Health Sciences, and the Electric Power Research Institute.

  5. Why is a 500 kV line the best system for transmitting power?

    Transmission lines are used to transport electricity long distances. The longer the distance, the higher the voltage needed to move it efficiently. A lower voltage transmission line, such as 230 kV, would not be able to accommodate the planned growth in the region and more lines would soon be needed. A 500 kV transmission line provides as much capacity as multiple 230 kV transmission lines.

  6. Would the substation/transmission line make noise?

    Idaho Power describes transmission line “audible noise” (often referred to as “corona”) as a sputtering sound or a low frequency humming sound. Irregularities on the surface of the conductor such as nicks, scratches, contamination, insects and water droplets can increase audible noise. Consequently, during periods of rain and inclement weather, transmission line noise may be more audible (although this if often masked by the sound of rain). Idaho Power states that under most circumstances, transmission line noise would be inaudible past the edge of the right of way during fair weather.

    To minimize noise levels, Idaho Power selects substation and transmission line materials according to industry standards. Idaho Power also works hard to ensure that hardware is secured tight and that conductor surfaces are not scratched or nicked during construction.

  7. Why is an overloaded line a problem?

    Every transmission line has a thermal rating associated with the physical characteristics of the conductor material being used. Electrical current generates heat in the conductor and should the electrical current become too great, the line could be damaged or even break. The electrical current a given line is carrying can be limited to prevent overloads on parallel lines should the line be taken out of service. New transmission lines would improve electric system reliability by providing an alternate, separate path for power transmission providing additional capacity and relieving congestion on the existing transmission network.

  8. Does Idaho Power have to meet reliability standards?

    Yes, Idaho Power voluntarily complies with reliability standards put forth by the Western Electricity Coordinating Council (WECC) and, by signatory agreement, concedes to the WECC the ability to impose financial penalties for reliability violations.

    Idaho Power must periodically submit reports on varying reliability topics to both the WECC and the North American Electric Reliability Council (NERC). WECC and NERC will also periodically verify that each company is operating by the in-place reliability standards. If either company is found to be out of compliance with reliability standards, WECC can impose monetary penalties. Additionally, Idaho Power is under the oversight authority of state public utility commissions which can force the entity to improve its system if reliability degrades to an unacceptable standard.

  9. What does “reliability” mean as related to extra-high voltage transmission?

    Idaho Power’s transmission system must be able to survive the single worst contingency (abnormal condition) on the system. No one event on a major transmission line can disrupt the system, making it unable to supply all end users. To accomplish this, certain transmission lines are not loaded to their full capability – they hold some of their capacity in reserve. Additional capacity is held in reserve so that energy can be imported from surrounding utilities should Idaho Power lose the ability to make power.

    Idaho Power must also adhere to what’s known as an “n-1” criterion. For multiple major transmission lines delivering power to the same point, if one of the lines goes out of service, the remaining lines must be able to carry both the load they were carrying before the event, plus the load carried by the line that is out of service. This is true even if the line with the highest capacity is the one that goes out of service (note: this requirement only holds true for major transmission lines).

  10. Why not replace high voltage alternating current line with a direct current (DC) line?

    Most of the transmission lines in the United States use alternating current (AC). Converter stations, which convert voltages back and forth from AC to DC, are extremely expensive costing hundreds of millions of dollars. The stations are required each time a DC line connects to the AC grid. While a high-voltage direct current line is efficient, it would not be cost-effective for the B2H Project. Tower heights and ground clearance requirements are the same for both AC and DC transmission lines.

  11. Does every transmission line have a backup transmission line?

    No. Many times, a lower voltage transmission line will be the only transmission serving a sparsely populated area. If the line goes out of service, the customers being served by that line lose power. In urban settings, lower voltage transmission lines typically do have backup.

  12. Has Idaho Power researched distributed generation?

    Idaho Power has been tracking and participating in pilot programs for distributed generation technologies for a number of years. Some of the technologies Idaho Power has been involved with are fuel cells, photovoltaics, micro-turbines and energy storage. At this time, Idaho Power feels that these technologies are still quite expensive in comparison to the B2H Project’s transmission line and some, such as fuel cells and micro-turbines, suffer from the expense of their fuel supply. Idaho Power will continue to track distributed generation technologies with the expectation that costs will come down and they may become useful in Idaho Power's energy supply portfolio.