Maine is at the forefront of green energy production with two wind farms producing energy, a third nearing completion and many others in the permitting stages. Getting the energy to market, however, presents significant challenges because of the state's mountainous terrain and adverse weather conditions.
Most projects require the construction of a 115-kV transmission line to reach the local utility for wheeling to market. Additionally, the local utility typically will need to rerate existing lines to accommodate the increased energy. The new Kibby Mountain wind farm site in the Carrabassett Valley area in Maine is a good example of these requirements.
Kibby Mountain, the Carrabassett Valley and the Sugarloaf Mountain ski area are served by Central Maine Power Co.'s (Augusta, Maine) 115-kV Section 215. The line is a radial feed that was built in the early 1970s.
While the line has kept up with the growth of that area for the past four decades, the additional generation will stress the line by creating resistance on the conductors. As a result, the conductors will heat up and stretch, causing the line to sag.
Power company engineers reviewed the lines section by section and found that there were areas where the additional sag created would not meet the National Electrical Safety Code clearance requirements. Central Maine Power then hired On Target Utility Services (Portland, Maine) to replace 78 selected structures with taller structures to keep the line in compliance. Additionally, tight time frames required that the work be done in the winter and be performed energized.
On Target assigned 10 lineworkers and a line supervisor the task of changing out the structures starting in December 2008, with a completion date of May 2009. The crews missed three weeks while working on storm restoration, wrapping the project up in the third week of May.
The crews only worked a five-day week three times during the winter because of the extreme conditions that cancelled work. Temperatures routinely dipped below zero, and 30° to 35° below zero was not uncommon. Factoring in the wind chill and heavy snows made a bad situation worse. Starting equipment every day was a chore. Linemen would hook up jumper cables, have kerosene heaters blow hot air into the engine compartments and hook up a generator to the block heaters. Usually, the field crews could get everything running within a half hour. On extreme nights, the harder starting equipment would be left running.
Despite the low temperatures, water was a constant problem. Streams would continue to run under the heavy blanket of snow, and the crews had to be religious about cleaning out equipment tracks to prevent damage to the components.
The cold weather also had the crews searching through catalogs for the warmest flame-retardant gear that was available. Double-thick hooded sweatshirts, insulated coveralls and steel-toed insulated pack boots became treasured items. Boot dryers were purchased to dry out boot liners and gloves so the gear would be ready for the next day.
Line belts became an issue as the number of layers increased. One lineworker finally gave up and bought himself a larger belt. Keeping everyone's face covered to prevent frost bite was the most difficult challenge, and there were many different approaches.
In addition to dealing with the adverse weather conditions, the linemen also faced a challenge just getting to the job site. The terrain in the area is mountainous with glacial till and swampy. Approximately 35% of the structures had to be set in ledge. The line is 19 miles long with only four road access points requiring long travel times into some of the structures. The longest haul in was more than 8 miles at roughly 3 mph.
The operation looked like a military campaign with a bulldozer leading the way followed by two flex track cranes, an excavator and an excavator outfitted with a hammer for pounding ledge. The equipment would go structure to structure and would be left at the last structure at the end of the day.
The crews traveled in and out of the job site on a rubber tracked dump truck. Ice and side hills were constant dangers for the tracked equipment. As a result, the bulldozer was used to assist equipment over the steep pitches.
The tracked equipment navigates hills best when traveling straight up and down. Traveling across is not recommended because the machine may slide sideways. The bulldozer operator was tasked with finding or making a safe route for the rest of the equipment.
Several techniques were employed to cross boggy areas depending on how wet it was. Corduroy roads — trees felled perpendicular to the route — were employed on very wet areas. In more stable areas, the small flex-track dump truck would pack the snow down to allow the cold to get to the bog. This would be frozen enough for the heavier equipment to get across. The deep snow facilitated movement through boulder-strewn areas by acting as land fill, allowing the crews to travel over very rugged terrain.
The major part of the production time lost on the project was associated with the crane work. Heavy and gusty winds created safety issues for the crane. The linemen had no way to stabilize the winch line as equipment was raised and lowered. Once the wind reached about 20 mph, work would be suspended. This was tough on the crew, particularly if they had just spent an hour getting into the site.
Compared to the weather, the hot stick work became the least difficult part of the project. Section 215 of the transmission line couldn't be taken out of service because it served as the sole feed into the Sugarloaf ski region. As a result, linemen had to hone their skills in handling energized conductors.
To protect themselves while working hot, the linemen wore flame-retardant clothing and personal protective equipment such as glasses, gloves and hard hats. They also used standard hot stick equipment.
Because they were working hot, the linemen had to be carefully watch the weather conditions. The linemen couldn't hot stick in the rain or snow because the integrity of the stick would be compromised. The crews also couldn't work on the energized line in heavy winds because they couldn't control the moving conductors. To minimize the amount of delays due to severe weather, the line crews often set poles in the rain, prepared to transfer the wire, and then stopped and waited for the weather to clear.
The crews completed the project with no lost time accidents, no medical treatment and no significant equipment damage. To stay on schedule, one crew forged ahead, breaking trail, building pads as necessary for the cranes and setting the poles. If ledge was encountered, the hammer would smash it up, and the excavator cleaned the hole. The crane operator would line down through the phases and hook onto a chain on the pole.
The excavator set up at the butt of the pole and attached a strap to the butt and picked up the butt. As the crane winched up, the excavator moved toward the old pole, keeping the new pole in line with the phases. When the pole was perpendicular, the excavator released and the crane set it in the hole, plumbed it and the excavator backfilled. This crew then moved on, and the transfer crew moved in with its crane.
The transfer crew equipped its crane down line with a 138-kV deadend insulator with a hot line block at the end. The crews used this to transfer the static wire to the new poles. The insulator would then be removed, and the new arm would be swung into position and pinned on the new poles. The crew then used the insulator again to move the energized outside phases from the old structure to the new structure using hot sticks equipped with pin pullers, ball socket adjusters and a lobster claw. The crew then suspended the center phase from the new structure with a link stick and removed the entire top of the old structure in one piece. The center phase was clipped in to the new structure and the old poles felled.
By working together, the On Target crews were able to successfully complete the job and prepare the transmission system for increased surge of power once the wind farm comes on line. The lessons learned about operating in mountainous conditions have been filed away in the memory banks awaiting another opportunity.
Ed Godin ([email protected]) is the superintendent of transmission for On Target Utility Services in Portland, Maine. He has been with the company since 1997.
