The North American Electric Reliability Corp. (NERC) is taking an aggressive approach to ensure the reliability of transmission lines throughout the United States. While investigating a recent outage on the East Coast, industry officials discovered violations of industry standards for allowable operating temperature and line clearances through the utility’s transmission line route. NERC officials immediately sent a message to utilities across the U.S.: Determine existing violations and fix them. Fast.
Utilities were required to have an action plan in place by Jan. 18, immediately followed by a systemwide assessment of potential violations. Any remediation work will be prioritized and is expected to be completed within one year of the assessment results over a three-year compliance period.
“NERC realized that in some instances, utilities don’t have current information on the field conditions of their transmission facilities as it relates to line capacity,” says Chris Norquist, Burns & McDonnell project manager.
The Right Approach
Utilities have some freedom in developing a strategy that makes sense for their system. Options for completing the assessments can include a combination of patrolling their lines, field spot-checking various portions of the route or using light detection and ranging (LiDAR) technology. Field verification of the lines through patrolling or ground surveys can take extensive time and manpower to complete, and not many utilities have the maintenance staff to take on the extra work. In many instances, continuous access is not available along the transmission routes, adding difficulty to verification from the ground.
LiDAR technology may be the most comprehensive option. LiDAR is deployed using a helicopter or fixed-wing aircraft equipped with a special unit of lasers. The aircraft flies over a transmission route as the lasers connect with the route and objects below, assigning tens of thousands of geo-positioned points on the transmission line, poles, vegetation, buildings and the ground.
The points are typically processed by the LiDAR firm performing the flyover, classified and sent to the engineer who will pull the information into an overheard power line design program, such as PLS-CADD, to create a 3-D model of the line and its surroundings.
“With the model created, the program uses specified weather cases to determine how a transmission line will perform during specific weather events, such as high wind or ice storms,” Norquist says.
With that information, a utility can gain an accurate capacity rating for its transmission assets by knowing if nearby trees and buildings will adversely affect the lines during significant weather events or if there are other existing violations that need to be addressed.
Timing Is Everything
A limited number of LiDAR firms are available to perform the flyovers, which means there could be a long waiting period between hiring a firm and getting the results. With remediation required as quickly as possible but no later than one year from the time of discovery, the ideal solution is to partner with an engineering firm to keep the project moving.
“With NERC’s remediation timeline, there’s really not a lot of time to waste,” Norquist says. “If we’re on a team, even while the assessment is in progress, we can start developing a plan for remediation. As soon as the assessments are complete, we can start developing the most cost-effective engineering solutions.”
Using a well-developed plan and diligent effort, utilities will have a solid understanding of the current state of their transmission systems and can comply with the NERC alert while averting potential costly outages.
For more information, contact Chris Norquist, 816-822-3266.