By Matt Dell
Selecting the correct equipment for the job and keeping grounding sets maintained and in safe working order is critical to ensuring safe working conditions in the field. Lightning, human error, static electricity, induced voltage and backfeed are all reasons the line you are working on could become energized.
|Exhibit 1. The discoloration of the copper can be an indication of over-heating or change to the material composition.|
Starting Off With the Right Equipment
When purchasing grounds, ensure they are built for the job at hand. A professional testing facility, such as Hi-Line Utility Supply, can build ground sets to your jobsite specifications and certify them for use. According to Occupational Safety and Health Administration (OSHA) standards, grounding equipment must be capable of conducting the maximum fault current that could flow at the point of grounding for the time necessary to clear the fault. Protective grounding should have an electrical impedance low enough to cause the immediate operation of protective devices in case of accidental operation of the lines or equipment (OSHA 29CFR 1910.269(n)(4)).
|Exhibit 2. Damage to cable strands at ferrule, in addition to corrosion from exposure to moisture (green tint on strands).|
Stay Safe with Certification and Repair
While a ground set that appears obviously damaged should be sent in for testing, the same holds true for ground sets that appear to be in pristine condition. You cannot always tell by a visual inspection. Regular testing intervals are highly recommended. To properly inspect and certify a ground set, it must be completely disassembled, and each component (ferrules, clamps, connectors and cables) thoroughly cleaned and then individually tested. Before being reassembled, repairs and part replacements are made. Once reassembled, it will be tested again as a whole unit.
|Exhibit 2.1. Damage to cable strands at ferrule, in addition to corrosion from exposure to moisture (green tint on strands).|
Ground sets that have been tested by a qualified testing facility will always be labeled with the date of test and recommended due dates for recertification. This will keep crews informed about test interval expiration dates.
The complexity of the recertification and repair process requires highly skilled and experienced personnel, and the industry trend is moving towards having an experienced testing laboratory, such as Hi-Line to complete these processes. Hi-Line Utility Supply tests and refurbishes more than 400 grounds and jumpers each week, and also provides all required testing documentation, including the additional certifications needed by most wind farms.
|Ground Set 1|
Properly maintained grounding sets will keep you compliant and ensure you remain safe while working on the line. Remember, a line that is de-energized can easily become energized in the blink of an eye, and keeping electricity grounded when work is being performed is critical to avoid an electrical current seeking your body as the grounding path.
|Ground Set 2|
So which one of the grounding sets pictured here failed? They both did!
Steve Taylor, Hi-Line's repair department manager, noted the ground set that looks like it is in good shape (Ground Set 2), is deceiving.
"The cable strands have been damaged and broken at the ferrule, and moisture created a corrosive condition (the green tint you see), creating a high-resistance failure," Taylor said. See Exhibit 2 and Exhibit 2.1.
|Exhibit 3. Ferrule nut is loose, creating a high resistant point from loose contact with excessive contamination.|
Further examination also yields that it appears this ground set may have been exposed to overheating.
John Malloy, senior product specialist at Hubbell Power Systems, said: "At the back of the ferrule it appears to be discolored, which can be an indication of over-heating or change to the material composition that takes the material from a soft copper to a brittle copper and actually can anneal the ferrule to a new material state. The melting point of copper is 1,083F according to ASTM F855; annealing occurs at lower levels, but we generally only see that in an instance where the set has been subjected to fault current levels way above its normal ratings or has had multiple closing during successive heat levels, and that's when the annealing occurs." See Exhibit 1.
|Exhibit 4. Contamination where ferrule meets shrink tubing. Dirt, moisture and petroleum-based products are all forms of contamination that can conduct electricity.|
If the ground set has been exposed to a high ampacity, or fault current, the ground set should be discarded.
Less surprising is the damage on the rougher looking ground set. See Ground Set 1.
|Exhibit 5. Cable at shrink tubing is kinked, causing weakness to the inner copper cabling.|
"The ferrule nut was loose, creating a high resistance point from loose contact with excessive contamination (see Exhibit 3), and there is additional contamination at the ferrule where shrink tubing protects the cable end (see Exhibit 4)," Taylor said.
|Cuts to cable jackets can compromise the quality of the cable and can also release electrical flow.|
Dirt, moisture and petroleum-based products are all forms of contamination that can conduct electricity, preventing this equipment from properly doing its job. In addition, as seen in Exhibit 5, the cable at clamp was distorted because of folding and bending, creating a high resistance point with damaged strands inside.
|Wire brushing should occur before and after use to remove dirt and corrosion.|
Cable damage from bending and folding at the clamp is common. Always ensure ground sets are stored and handled with care to prevent this type of damage. Taking the time to wire-brush clamps and ferrules to remove dirt and corrosion will keep harmful, electricity-conducting materials off your protective equipment when you need them working at their peak performance. Most importantly, always ensure you are using the correct equipment for the job, and meet all voltage requirements. Always visually inspect your safety equipment, before and after every use. Regular inspections, testing and re-certifications, conducted by a professional testing facility such as Hi-Line Utility Supply, will keep your sets in safe, working order. If you are unsure, consult your company's safe work practices. And remember-you simply cannot tell by looking at it!
|Distorted cable from bending and twisting. This can cause breakage to the cable within.|
About the author: Matt Dell is the owner of Hi-Line Utility Supply, a provider of lineman's transmission and distribution tools, equipment and services since 1960. With more than 10,000 products in stock, Hi-Line guarantees every in-stock order placed by 4:00 p.m. Eastern Time ships the same day, guaranteed. Our skilled team will assemble custom ground sets to your specifications, and also service and repair them. Hi-Line is also your "one-source" stop, offering rubber goods testing, tool repair and fiberglass restoration at both of our locations (Elgin, Ill. and Millbury, Mass.). Dell can be contacted at (800) 323-6606; email firstname.lastname@example.org; www.hilineco.com.