National Grid is warning New Yorkers of increased helicopter activity along their 6,000 miles of high-voltage transmission lines as the company undertakes its annual helicopter inspection.

The rugged and isolated terrain over which much of National Grid’s transmission system passes makes the use of helicopters an efficient way to check the lines.

Transmission lines are generally defined as high voltage lines carrying electricity at or greater than 115 kv. They typically deliver power from generating plants to local electric companies.

“Spotting potential problems before they turn into service interruptions is an essential part of maintaining the safety and reliability of the transmission,” said National Grid’s Director of Electricity Transmission Inspections and Maintenance Gerald Convery. “Particularly during the winter months when ice and high winds can impact our transmission equipment, we owe it to our customers to take pre-emptive measures to head off service interruptions whenever and wherever we can.”

The inspections are conducted by experienced trained personnel using high-powered gyroscopic binoculars. They are particularly interested in signs of wear on power line conductors and lightning protection devices, damaged or leaning transmission structures, loose or broken guy wires, broken, chipped or cracked insulator equipment, and trees leaning toward the lines or into the transmission corridors.

In addition to damaged lines, towers or trees, the flights are conducted to identify signs of waste disposal or unauthorized construction on the rights of way. These could alter the amount of clearance between the ground and the power lines and might lead to human contact with the lines that could result in severe injuries or vegetation interference that could lead to power outages. Of additional concern are signs of erosion, which may cause the transmission structures to become unstable, Convery says.

The inspections are expected to take about five weeks, weather permitting. Flight schedules and routes may be changed on short notice due to regional weather conditions. Public safety officials in the communities over which the flights pass are notified of flight patterns.

Flights will also be conducted during the summer.