When Wearing Cover-Ups, One Size Does Not Fit All
Dec 1, 2007 12:00 PMBy Joesph Torres, San Diego Gas & Electric Co.
Rubber gloving and energized work has become the standard rather than the exception in recent years among overhead distribution linemen. At San Diego Gas & Electric Co. (SDG&E; San Diego, California), distribution linemen began rubber gloving all energized lines when the utility raised the parameters for energized work from 4000 V to 12,000 V. As a result, the linemen install and wear properly rated gloves, sleeves and covers when working within the approach distance of energized conductors.
The utility industry has seen many changes in gloving and cover-up procedures. At SDG&E, the biggest change has come not from the personal protective equipment (PPE) used, but rather from the pole-top hardware, especially insulators.
PPE, designed to guard linemen against accidental line contact, goes by many names: tupperware, hose, pigs, line “guts” and hoods. The primary function of cover-ups, or guards as some linemen call them, is to prevent the accidental contact between an operator and an energized line, or between a jumper and a grounded member on a pole or crossarm.
Adapting to Different Configurations
As gloving became a more common procedure at SDG&E, so did cover-ups. The utility purchased a variety of cover designs to adapt to different system configurations. These tools, tested for use on circuits rated through 69 kV, are widely available from several manufacturers. Various sizes and lengths are available to fit the size of conductor, insulators and other energized equipment in the work area.
Some of these products can be joined together with complementing end connections to insulate a longer span of bare conductor and supporting insulator. This makes it easier for linemen to transport the covers to the pole-top work site. They have recently become lighter in weight, while still retaining their dielectric strength.
Linemen also can use these products to cover strain insulator deadends, with or without side jumpers. Used individually, the insulator cover isolates arresters, cutouts or leads. Most cover-ups and standoff insulator covers, crossarm guards and pole covers are available with or without attachment eyes or sockets for lifting and placement with clampstick or fiberglass handles.
Maintaining Cover-Ups
Linemen store most of their cover-ups in waterproof canvas bags, which accompany them in the bucket or may be sent up the pole top and down by a hand line. Scheduled maintenance, which includes the visual inspection, cleaning and testing of each tool, is an important part of the gloving work practices. Cover-ups should be kept clean at all times and wiped off with a clean rag to remove dirt and oil residue. Mild soap and water also can be used for tougher cleaning needs. Utilities must exercise caution before using solvents or abrasives that may attack or damage the part's mechanical or dielectric properties.
A simple but practical rule linemen learn about approaching energized lines is to install the PPE (cover-ups, hoses, blankets) and remove it in the order that provides the maximum protection while moving into, around and out of the energized area. This applies anytime and anywhere linemen are working around energized lines — in a bucket, from a pole or in a manhole.
Working in a Bucket
The most significant change in rubber gloving in the past seven years has been the increased use of aerial bucket trucks. Prior to 2000, when energized gloving was first introduced, most gloving activity was performed from poles, with a small percentage performed from aerial bucket trucks. While working from a pole, linemen were trained to wear approved sleeves and gloves, and routinely test and visually inspect the gloves for deterioration that would affect the protective insulator quality of the gloves. Linemen also participated in work procedures training for covering energized conductors with rubber hoses and blankets.
Because linemen climbed and worked from the pole, the cover-up area was limited. As aerial work platforms have become more prevalent, the exposure to energized lines and the flexibility in approach distance to energized lines has expanded during pole-top work.
Utilities are also locating an increasing number of poles in vehicle-accessible areas. This allows crews to work from insulated buckets and platforms. Linemen continue to cover and perform work on energized conductors in the same manner as they had in the past from poles, but the lengths of covers and use of blankets have increased, along with the increased use of aerial devices.
Polymer Versus Porcelain
Another major change has come not in the cover-ups but in the size of the insulator cover used to insulate the work area. Traditionally, porcelain has been the material of choice for distribution and transmission voltage insulation. However, porcelain has several disadvantages including a low strength-to-weight ratio, a more brittle nature, and susceptibility to salt and dirt contamination.
Coastline utilities face a major problem with salt contamination on insulators closer to the ocean, which results in flashovers. Bonding used to be a major concern on lines within 3 miles of the ocean. To address the insulator contamination issue, utilities built their coastline systems with much larger insulators.
When linemen began working on or near energized lines along the coastline, they had to carry larger J-neck-type conductor covers, which were awkward and cumbersome. This was especially true when working with spiral conductor covers that were required to slide over the bigger porcelain insulators.
Non-Ceramic Insulator Cover-Ups
When nonceramic insulators made from polymeric materials were introduced 30 years ago, they improved the insulator contamination problems. These polymer insulators are designed with less conductive metal area exposed, and performance under contaminated conditions was found to be significantly better than with ceramic insulators. They are also much smaller in size. These findings led SDG&E to begin converting all porcelain insulators to polymer insulators. Along the coastline, this meant smaller insulators, which allows linemen to use smaller cover-ups when working on or near energized conductors.
The use of polymer insulators has been growing steadily. In some applications, such as distribution-class surge arresters, polymer products have virtually replaced porcelain.
SDG&E still has a large number of poles that are all porcelain, so linemen keep an assortment of old cover-ups to accommodate these poles as the need to work on them arises. As these poles are refurbished, the insulators are being converted to new polymer pin insulators and post insulators. As a rule, linemen working within 3 miles of the coastline still carry a larger J-neck cover. Once the linemen get inland, they typically carry a much-smaller F-neck cover.
Linemen prefer using the older rubber line hose and insulator cover-ups. These rubber goods tend to cover just about any size of conductor or insulator compared to the new plastic conductor covers. They also carry rubber-slotted blankets with eyelets and rubber blanket buttons, which give the linemen a better cover-up in certain instances, like cutouts and potheads.
Staying Safe
In recent years, energized work has become an everyday assignment for SDG&E field operations. To mitigate the risk associated with this increased exposure to field personnel, SDG&E is doing everything it can to ensure that no employee approaches or takes any conductive tool or equipment closer to any energized power lines or equipment without being properly insulated or guarded. Safe distances and all safety procedures are adhered to at all times. There is only way: The right way.
Joseph Torres is construction supervisor for Electric Regional Operations Northeast Construction & Operations at San Diego Gas & Electric Co. He has 39 years of experience as a journeyman lineman, troubleshooter, electric foreman and supervisor. JTorres@semprautilities.com