PPL Electric Utilities must meet federal and state standards for service reliability
PPL Electric Utilities is member of the PJM Interconnection LLC., which oversees and operates the transmission system and the movement of wholesale power in all or part of 13 states and the District of Columbia.
In 2010, PPL Electric Utilities spent nearly $100 million to maintain and improve electric service reliability. Our reliability programs include inspection and maintenance schedules for transmission and distribution systems, vegetation management programs, and investments in additional distribution automation.
Trees are one of the more common causes of power outages, especially during storms. To safeguard the reliability of its electric distribution system, PPL Electric has developed a comprehensive program to clear trees and other vegetation around power lines. In 2010, PPL Electric Utilities spent more than $30 million for vegetation management along transmission and distribution power lines.
Click here to visit our Vegetation Management website.
If trees touch the power lines, there can be short-circuits and widespread service outages. Taller species of trees that are permitted to grow under power lines could eventually contact the wires, causing service interruptions and unsafe conditions. It is necessary for PPL Electric to trim these trees to maintain safe, reliable electric service
All distribution lines are surveyed and trimmed on either a four- or five-year cycle, depending on location. Tree trimming is intended to manage vegetation growth and growth rates vary geographically, not by urban/rural designations. Vegetation growth rates are higher south of the Blue Mountains than north of them. In 2010, tree trimmers qualified in working around energized electric conductors pruned trees along 7,444 miles of distribution lines.
PPL Electric uses a widely accepted tree maintenance practice known as directional pruning, which removes only the branches growing toward power lines. Remaining branches are left to grow naturally. Trees retain more of their natural shape and spacing, and because less of the live crown is removed, trees are not placed under as much stress. The National Arbor Day Foundation and other tree care groups endorse directional pruning as better for tree health.
We spend $500,000 a year to install animal guards at substations to prevent birds, squirrels and other animals from entering the electrical facilities and causing outages. In areas where animals have caused power outages, we install animal guards along aerial facilities to prevent future occurrences.
Inspection and maintenance
Routine helicopter patrols of all transmission lines are conducted every year, as well as more comprehensive aerial inspections on a four-year cycle. We also perform ground patrols of approximately 1,500 miles of transmission lines annually.
There are more than 34,000 wooden poles on the transmission system. Some are replaced each year based on age and condition.
From helicopter patrols, we use laser beams to measure the distances between transmission power lines and any obstructions, like trees. It's called LIDAR technology, now widely used by utilities across the U.S. We look to ensure no obstructions can interfere with the operation of the high-voltage transmission lines.
PPL maintains 35,000 miles of overhead distribution lines across its system, delivering power to customers. The electric delivery system includes roughly 900,000 utility poles that carry conductors, crossarms, insulators, transformers, circuit breakers, lightning arrestors, and other equipment. The condition of each piece of equipment contributes to power reliability. We are adding more lightning arrestors to the delivery system to reduce the impact of adverse weather on electric reliability.
Additionally, PPL delivers power along 6,500 miles of underground lines, mainly in cities. These lines run through hundreds of manholes and underground vaults, which are inspected periodically each year. We test and cure about 75 miles of underground primary cable each year, and we installed 136 miles of new underground cable last year.
Inspections of distribution lines and poles are done periodically based on a schedule and circuit performance to identify equipment problems that may affect system performance or service to customers. Overhead line inspections identify the weak links in the system so that damaged or deteriorated equipment can be repaired or replaced. Some of these inspections are done with infrared cameras to identify problems before an outage occurs. This program is referred to as our thermography inspections, which are performed on about 6,000 miles of distribution circuit each year.
PPL Electric Utilities operates nearly 400 substations. At regional substations, a battery of maintenance tests is performed each year on bulk power transformers and other equipment to ensure ongoing reliable operations. These tests are the only way to evaluate equipment condition. There are about 750 super-sized circuit breakers at our substations, too. These are essential to keeping the power flowing. Substation mechanics inspected and maintain them regularly.
Substation maintenance programs include inspections, condition testing and overhauls of equipment, such as power transformers, circuit breakers, disconnects, power cables, and security equipment. Some equipment is maintained on a schedule basis; other equipment is condition monitored. These two methods help ensure that maintenance work is performed in a timely manner. In addition to time and condition-based maintenance, thermo-graphic inspections help to ensure that substation equipment does not operate at elevated temperature levels for an extended period of time, which could lead to premature failures.
Upgrades and replacements for optimum reliability
Each year, several million dollars are set aside for specific reliability improvements on local distribution circuits that experience a higher than average number of power outages or outages with generally longer duration. Engineers regularly review performance of all distribution circuits and identify solutions like additional fuses, more lightning arrestors or installation of automated devices to provide better performance. In some cases, circuits are re-designed to improve reliability for customers.
In addition, in 2011 and 2012, PPL Electric Utilities plans to install or replace fault indicators at 3,100 locations on the distribution system. The strategically placed fault indicators will alert emergency responders to cases of trouble so we can quickly identify the location of faulted equipment, reducing outage time, and improving customer service.