BC Hydro was an early adopter of live-line tool and bare-hand technique for live-line work on its 45,000 miles of transmission and distribution lines. But in 1970, after a bare-hand work accident and nagging inconsistencies in work practices, all company bare-hand work was discontinued. Known for its aggressive hydro generation and a vision to deliver power without interruption, the company appointed the Bare-hand Working Committee in 1990, which has developed far-reaching procedures for certification of the utility's power line technicians and bare-hand equipment.
The Transmission Network
BC Hydro (Vancouver, British Columbia, Canada) owns and operates more than 11,000 miles of transmission line and 34,000 miles of distribution lines, delivering power to 1.6 million customers across a 366-sq-mile service territory serving 94% of British Columbia's population and transmission customers throughout North America. Some of the 60- to 500-kV grid is inaccessible even to four-wheel service vehicles, crossing mountainous terrain and spanning dense forests and wide river crossings.
The Bare-hand Working Committee, made up of managers, engineers and field workers, did its homework and realized that bare-hand work require a highly trained and motivated team of technical professionals. After almost a year of researching the industry and working with outside consultants, the team developed a comprehensive training program to certify power line technicians (PLTs) to perform bare-hand work.
To qualify for the 90-hour bare-hand training, a PLT must have a minimum of one year of experience working on BC Hydro transmission lines using live-line tool methods. Trainees start out attending 30 hours of classroom and hands-on training to become familiar with the various access techniques and equipment, such as ladders, carts, rope and aerial lifts. When the trainee has become accomplished at performing the access procedures and has completed the 30 hours of training to the satisfaction of the work methods instructor, he is assigned to a working crew for 60 hours under close supervision from the instructor. At the end of the 90 hours, he is certified to perform bare-hand work for BC Hydro.
Bare-hand Field Operations
BC Hydro presently has 38 bare-hand-certified PLTs performing energized conductor work, such as changing insulators, repairing conductors, installing aerial markers or changing bundled conductor spacers. The company has four certified bare-hand aerial lift trucks dedicated to bare-hand work. One or more aerial lift units and several bare-hand crews are based in each of the utility's three service regions, depending on where the work is required. All 138-, 230- and 500-kV transmission line work is planned as energized work unless an outage occurs for some other reason. Recently, BC Hydro started to use bare-hand procedures for 138-kV and 60-kV conductor repair and maintenance. During the committee's research, it noted that most bare-hand accidents in the industry were occurring on lower voltage. Therefore, the committee established that the minimum approach limit for 230 kV would be maintained when working on voltages lower than 230 kV. Workers are receptive to the clearance standards. They feel more comfortable working in a less congested area and enjoy doing the work.
Bare-hand work is sometimes strenuous. Fatigue is common and could become a safety concern. To address this challenge, BC Hydro established that duties be rotated among the crew members. Everyone works a different position for a period of time, from rigging on the tower to working on the wire. Each crew is made up of a safety watcher, a work methods instructor (who may have oversight for more than one crew) and a core team of PLTs who are all capable of performing any task. The work methods instructors (who are journey-person PLTs with senior experience levels) conduct the 90-hour PLT training, as well as work alongside trainees and crew members on a daily basis. This “player-coach” participation helps the company maintain consistent procedures among all bare-hand workers and aids in identifying and implementing best practices among the different crews. Workers report they enjoy their job and are less apt to burn out because of the varying work assignment. They are more attentive and maintain a higher appreciation of the activity of those working around them.
May through October is the prime time for bare-hand projects because of Canada's cold and wet winters, although some winter work can be performed in the interior of the province, which tends to be dryer. In January of this year, bare-hand crews completed a hardware replacement project on wood H-frame poles. The suspension shoes installed in the 1950s were difficult to hotstick. The job could have been done using conventional live-line tool methods; however, replacing the old hardware using bare-hand methods was easier and faster. A job like this performed bare-hand typically increases production by 30%.
Unpredictable weather is a constant concern in maintaining the insulated and nonconductive properties of equipment — especially the rope used in bare-hand technique. On a typical day, crews working in the mountains or along the Pacific Ocean may be working in a remote area on a long transmission crossing. Suddenly, a storm blows in. It may only last a short time, but the crew and the equipment are caught in the rain. For bare-hand crews using rope, this is a serious concern. Wet rope can become a path to ground, creating the potential for a flashover.
BC Hydro's standard procedure in the case of rain is to bring all rope back to the ground for moisture testing. As the rope is lowered to the ground, it is moisture-tested using a handheld, Hi-Test Rope Detector (Waukegan, Illinois; www.hdelec.com) testing device. The entire rope passes through the moisture detector at a rate of one foot per second. As the rope is pulled to the ground, the tester generates an approximately 13-kV current flow across the rope. A meter gage registers the moisture value.
An audible alarm and warning light also alert the inspector if high moisture content is encountered. Rope that does not meet the requirements is hung to dry or set aside for further inspection and drying.
Because of the rugged terrain and difficulty in accessing remote transmission lines and structures, 80% of BC Hydro's bare-hand work is performed by rope access ladders and insulated platforms and booms. Dry tests using the handheld moisture detectors are performed in the field as work commences each morning. While crews are lifting rope to the platform or structure, the dry test is performed on all rope. As with crews caught in the rain, rope that does not pass the moisture test is left in the air to dry and a new rope is brought to the bonded-on workers. If a crew works at different towers or other locations during the day, additional dry tests are not required unless the weather changes and/or the rope becomes subject to moisture.
Annual wet tests also are performed on all bare-hand rope. A typical test includes selecting the dirtiest section of the rope — one near each end and a third from somewhere in the middle of the rope. Approximately one foot in each section is sprayed with distilled water until the rope is sufficiently wet. A moisture testing device with electrode probes is placed on the rope and voltage of 100 kV dc is applied until the leakage current stabilizes, which usually takes about one minute. The maximum permissible leakage current is 75 microamperes. Rope that passes the wet test is thoroughly dried prior to returning to service.
Types of Rope
Rope used during energized work methods is classified according to field application into three categories and is easily identified by color-coding.
All three types of rope are inspected in the field prior to use by the crew. The green and orange categories of rope require an annual dielectric shop test, which includes a wet test. These two categories of rope also must be tested for moisture before work begins each day and again during the day if exposed to inclement weather.
When the Bare-hand Working Committee was developing aerial life equipment certification standards, it was observed that the hydraulic oil running through the aerial boom had the potential over a period of time of becoming contaminated, which may affect the dielectric integrity of the oil and create the potential for a problem. The committee worked with Powertec Lab in Vancouver and recommended that quarterly hydraulic oil tests be performed to ensure that the nonconductive and dielectric certification of the aerial lifts was being maintained. Because there was no oil test standard in the industry for bare-hand procedures, ASTM D1816, which is the standard used for testing transformer oil, was adopted. A pass/fail criterion of 25 kV over electrode spacing of 2 mm was determined to be the most appropriate solution.
Oil Test Revisited
Since the oil test procedure was adopted in the early 1990s, an average of two oil changes each year have been required at a cost of more than $7000 per unit each. In 1999, the Bare-hand Working Committee decided to look at the appropriateness of the oil test and the possibility of adopting different test standards or changing the pass/fail criteria. Alternative certification procedures or adjustment in the pass/fail threshold were discussed. The investigation turned up no alternative standards that the committee could live with, but a new oil-drying process being developed by Powertec Labs for transformer oil was discussed that showed promise both in reconditioning the hydraulic oil and restoring the oil's dielectric properties.
|Category||Rope Type||Rope Color||Test Procedure|
|Up to 60-kV live-line tool applications||Double-braid polyester-polyester||White||Not dielectric tested|
|Up to 500-kV live-line tool applications||Meets ASTM.F.1701||Green||BC Hydro standard based on ASTM F 1701|
|Bare-hand||Meets ASTM.F.1701||Orange||BC Hydro standard based on ASTM F 1701|
The portable prototype oil dryer was shipped to the region where one of the aerial lifts was scheduled for maintenance and quarterly certification. The drying process, which takes about one day, was completed, and samples were sent to the laboratory for analysts to determine the effect of the drying process on oil additives and viscosity. The lab results showed that the filtration process removed the contaminants and restored the oil to meet the bare-hand ASTM D1816 dielectric oil criteria, without affecting the oil's viscosity and additive properties in any significant way. Since the oil drying remedy for high moisture levels was adopted two years ago, no oil changes have been required. Accounting for the cost of operating and maintaining the dryer, BC Hydro is realizing an annual savings of about $15,000.
Because of BC Hydro's success in establishing bare-hand procedures and best practices, the demand for PLT crews has increased significantly. A few years ago, it was not uncommon to request an outage to perform maintenance on a circuit. Today, work-outage requests are almost unheard of. The number of BC Hydro bare-hand-certified PLTs has grown in the past three years from 25 to 38. In 2003, BC Hydro completed its first project using helicopter access to energized transmission lines. The pilot project was successful and showed great promise for future work. BC Hydro continues to strive for improvements, but the test of time has confirmed that the Bare-hand Working Committee did its homework.
Pat Sawatsky is manager of the Field Services Work Methods Team at BC Hydro. He has 30 years of experience with BC Hydro as a power line technician, instructor and field manager. The Work Methods Team is responsible for developing and/or approving energized work procedures at BC Hydro. The team of 10 people has engineering, trade and instructional expertise.
Tim Remfert is a work methods trades training instructor at BC Hydro. He has been an integral part of the BC Hydro bare-hand program from its inception. He instructs crews in the work procedure and works with the crew as part of a bare-hand team. Remfert is also the chairman of BC Hydro's Bare-hand Working Committee.