Opening a Can of Worms
When you say you are opening a can of worms, you are warning people that you are about to discuss something that could be very controversial or lead to more problems. And that’s exactly what I’m about to do.
During the review of an article written by Pam Tompkins and Matt Edmonds for the December 2022-January 2023 issue of Incident Prevention (see https://incident-prevention.com/blog/electrical-protective-equipment-and-live-line-tools/), the magazine’s exceptionally qualified editorial advisory board members brought up a passage that they wanted to discuss very carefully. The article itself – which deals with electrical protective equipment and hot sticks – is accurate and useful. At its very end is a statement, almost mentioned in passing, that employers can test hot sticks with battery-powered hand-held testers. And that statement is correct, they can. But some of our editorial advisory board members are very familiar with portable testers and have been directly involved with comparison testing of portable hot-stick testers and high-voltage lab testing of hot sticks. That is where the can of worms is found. The power-line industry uses portable hot-stick testers widely and confidently. The issue is that we may not be using them correctly. But is that a problem?
The OSHA Standard
Let’s start from the beginning with the OSHA standard for testing hot sticks. It is worth mentioning here that tools for any work method that are the primary or first line of electrical protection for the worker have an electrical testing and inspection protocol to ensure that they are dependable. If it can’t be tested, or if its performance can’t be assured in some effective way, it can’t be considered an employee’s primary means of protection.
For instance, insulating or dielectric overshoes were considered mandatory for electrical workers a decade ago, but OSHA rescinded that rule because testing and inspection were determined to be inadequate to ensure those devices as primary means of protection from electrical hazards. Those devices are now, as OSHA puts it, “part of a system of protection” for employees exposed to electrical hazards. Category A barehand aerial platforms are another example. The boom is tested before each use to assure minimal current leakage because the boom is the primary protection for the worker, isolating the energized platform from ground with the insulating boom. In Category B aerial devices designed for rubber glove or hot-stick work, the boom is not tested before each use. Category B booms are tested once per year for insulation integrity, but it is the rubber gloves – inspected before each use and periodically electrically tested – that are the primary means of protection. In Category B aerial devices, hot sticks are also the primary means of protection. Like rubber gloves, they receive a periodic inspection, plus a visual inspection and wipe before each use. That protocol – a periodic inspection, and a wipe and inspection before each use – has been an effective OSHA policy since 1974. By the way, as noted in the preamble, that process was used by the industry for two decades before OSHA, and there is no instance in the record of a properly used and maintained hot stick failing and causing employee injury. I expect a reader or two to respond with stories about failed stick injuries, as I’ve heard often, but when I’ve tried to find a record of those instances, I’ve been unsuccessful. If you can verify one of those stories, our editorial advisory board wants to know about it. There are instances of smoking sticks in rain or snow, and I am one of those who experienced that on a 230-kV circuit 30 years ago. There was also a ladder flashover in 2022 that I heard about, but I don’t have any of the details.
Here is what OSHA says about testing hot sticks, which can be found at 29 CFR 1910.269(j)(2)(iii)(E) through (E)(3): “The voltage applied during the tests shall be as follows:
246,100 volts per meter (75,000 volts per foot) of length for 1 minute if the tool is made of fiberglass; or 164,000 volts per meter (50,000 volts per foot) of length for 1 minute if the tool is made of wood; or other tests that the employer can demonstrate are equivalent.”
That last statement – “other tests that the employer can demonstrate are equivalent” – generally applies to portable hot-stick testers, or at least that has been the customary interpretation across the industry. The preamble to 1910.269 mentions the (E)(3) “other equivalent tests” as part of other hot-stick-related discussions but never describes or explains what is meant by “other equivalent tests.” As a practice in OSHA rulemaking, OSHA often mentions the employer’s options to perform “equal,” “demonstrated” or “other” in response to OSHA’s specified actions. In a note to paragraph 1910.269(j)(2), OSHA refers to IEEE 516, which addresses other tests that might be employed.
IEEE 516-2021 describes two types of testing that can be performed. The first type, noted in paragraph 5.8.5, “Use of moisture or dielectric property determination meters,” is actually two types of high radiofrequency (RF) cross-sectional watt-loss testing. The other type, found in paragraph 5.8.4, describes the use of portable live tool testers this way: “Portable live tool testers provide a means for conveniently field-testing insulating tools without auxiliary equipment except for a power supply. It is very important to note that some portable units are designed to test the entire insulating tool’s cross-sectional areas for conductivity. To be certain of the tester’s capability, the user should check the applicable literature or contact the equipment manufacturer. Reliance on electrical testing is the prerogative of the user who is responsible for maintaining equipment calibration, application, and interpretation and responsible for the safety of the user.”
“Cross-sectional areas” in the previous paragraph refers to horizontal sections across the stick’s surface. The RF testers mentioned earlier can and will test deep into the foam filler through a cross-section of the hot stick. But I’m getting ahead of myself here; later in this article we will look at some 2002 Electric Power Research Institute tests that determined an electrode on a portable tester that completely encircled the hot stick improved reliability. EPRI Solutions, a division of EPRI at the time, intended to build such a model, but I don’t believe they ever accomplished that.
So, that’s what the rules say. Now let’s focus on the phrase “that the employer can demonstrate” and how that fits into the topic of portable stick testers. The two most familiar portable hot-stick testers are those from A.B. Chance and Hastings. Both testers operate on the Ohm’s law principle that voltage, resistance and current calculations are linear. Both testers also operate at an electrode voltage between 1,800 and 2,500 volts AC. Each extrapolates from the leakage current at the testing voltage what the leakage would be at 75,000 volts. Neither of the tester manufacturers explains this in their operating manual. You can find the Hastings operator instructions describing the multipliers applied to the actual current for the leakage reading. They also include, as do A.B. Chance’s, key operator hints to improve reliability. The Hastings document can be found at www.hfgp.com/storage/app/media/docs/instruction-booklets/hotsticktester_6799-6781.pdf.
Both manufacturers provide important practical instructions to ensure the reliability of the testers as part of a system of hot-stick maintenance and inspection. These are very particular rules for operation and testing, plus contact information for the user to call the manufacturer for more details. This is the “demonstration” that employers have relied on to use portable stick testers and comply with OSHA’s (E)(3) rule. The questions now become, are crews properly using the testers at their disposal, and can the employer demonstrate that the protocols with the portable testers meet the other requirements? Are portable stick testers reliable, and can the employer demonstrate that using the most basic electrical principle, Ohm’s law?
Many labs also use extrapolation of testing data at voltages lower than 75 kV to reduce corona damage to hot-stick surfaces. About two decades ago I got curious about this extrapolated test results idea and set up some comparison tests using our lab hot-stick testing bench and portable testers from A.B. Chance and Hastings. I compared testing on two 8-foot shotguns, two 8-foot switch sticks and two 12-foot 1.5-inch lift sticks. I divided each stick into 12-inch segments and compared the test results for every stick to every segment. I did all the tests using the wet-test method, spraying the sticks with tap water using a window-cleaner-type spray bottle. Now, readers, don’t get excited over the tap water in my tests. I wasn’t testing hot sticks, I was comparing results between testers, so the water’s conductivity did not matter.
The very first thing I noticed was that test results varied greatly at the working end of every stick. I guessed it had something to do with stray capacitance between the tester and the conductive end fitting, but I wasn’t curious enough to find out the technical why. I just started the tests 6 inches to 8 inches from the end. Keep in mind, I wasn’t testing to prove the stick was good; I was comparing instrument results. I did find inconsistencies, but they were on a very low order to the tune of about 7% to 8%. What I did do was roll the sticks 90 degrees, perform two tests per segment with the portable testers and average the readings. The lab tests were performed at the lab’s top test voltage of 40,000 volts AC. The lab tests used coil springs around the stick so that rotating was not necessary.
Where the stick segments failed under the portable testers, I could see a reason why. It was luster, a dent or puncture, or a linear scratch. But what I also determined was that a stick with a failed segment was not necessarily a failed stick. If a segment failed, I could move the test unit 6 to 8 inches either way and get a passing result. It occurred to me that a hot stick’s performance was not accurately judged by a segment test. The actual resistance to leakage increases by the resistance of each segment. We segment test because we have limited test voltage. This is not a recommendation, but if we really want to test a hot stick’s performance, we should apply an end-to-end voltage equal to 75,000 volts times the length of the stick in feet – and that’s not practical. The voltage would be hazardous, and the stick would be damaged. Such a test would not even be representative of the lineworker on a stick. In application, the stick is only hot at the working end (or the hanger), and the resistance of the whole length of the stick from energized point to the first point of different potential is what is actually limiting current flow. I respect colleagues in the industry who may disagree with me on this and would reject a hot stick that had a segment that failed. But for 20 years I hot-sticked primary and transmission from wood poles without issue, so I am comfortable with the segment test versus whole-stick performance idea. The segment testing of sticks is an accurate means of determining the overall reliability of a hot stick.
When I finished my exploration of testers, even though the lab test 7% to 8% of the time showed poor performance on a segment that the portable tester passed, I was confident that the visual inspection and wipe before use combined with an annual high-voltage test was dependable. Using a portable tester in the field is just an added and reliable method of ensuring the sticks are dependable.
Then along came Incident Prevention magazine’s editorial advisory board and references to some real testing done by real scientists led by George Gela, Ph.D., at the Electric Power Research Institute in 2002. EPRI is a professional organization well-respected in the electrical industry. The technical report is titled “Criteria for Development of an Improved Insulating Tool Tester, EPRI Palo Alto CA #1001751.” The report details the test methodologies and results and summarizes the comparison results between high-voltage lab tests and the portable stick testers from A.B. Chance and Hastings. The EPRI comparison tests also found discrepancies. On occasion, portable testers would pass segment tests on sticks that the lab tests would fail. Yet portable testers also failed sections that the lab tests failed with some consistency. The high voltage of the lab tests showed that resistance is not always linear. In simple but I hope accurate terms, the lab test voltage created additional stresses above the 20-kV RMS (the approximate corona point) through the stick and capacitive current between the electrodes that do not appear in the portable testers. Those factors are likely to have some stress effects that result in a failed section under test. In fact, the EPRI paper made the following suggestions based on their analysis of results.
EPRI Solutions’ analysis of the results of this study led to the development of the following scientific guidelines for designing a portable insulating-tool tester:
- The tester should detect the resistive current between the electrodes, i.e., it should incorporate provisions to eliminate (electronically or through other means) the capacitive current between the electrodes.
- To avoid corona on the electrodes, the applied test voltage should be less than about 20 kV RMS.
- The distance between the electrodes should be greater than about 3 inches, but little advantage is gained by increasing the distance beyond about 5 inches.
The EPRI comparison was valuable to the industry in several ways, including observations about the potential for corona skewing of readings as well as some potential for corona damage to sticks. There was also the observation that corona generated between the test electrodes in the lab would not occur between a working-end phase contact and the worker holding the stick. In that way, testing does model the hot stick’s performance as an insulator, but it doesn’t duplicate the work environment stress between the hot end and the worker. Lab tests at high voltage produce a much higher order of electrical stress on a stick segment than the actual electrical stress in the use of hot sticks in the field.
What the EPRI testing did show was little correlation in the results between the four test modes they employed, including comparison of high-voltage AC and high RF “watts-lost” analysis of stick performance lab tests. The EPRI analysis indicates that there is some room for improvement in the way we test hot sticks, but the issues discovered did not rise to the level of an impending hazard. Current versions of portable testers have technology improvements over those tested at EPRI in 2002.
Now, about the portable testers. They were never intended to be used as a substitute for high-voltage lab testing of samples. As a reminder, a close look at the requirements reveals that electrical lab testing of hot sticks is not mandated by either OSHA or IEEE 516. Both standards require testing as conditions, such as after repair, refinishing or when there are suspect stick issues found during a visual inspection. What does that mean? Historically, visual inspection and cleaning have been effective even without annual or biannual testing. That doesn’t mean we should stop annual tests; this information is intended to help the reader clearly understand the practical application of hot sticks as well as how to properly care for and use them.
Portable testers are not a primary means of assuring hot-stick performance. There are anomalies in every meter system, and it’s essential to understand the limitations of a portable hot-stick tester. There are important considerations when choosing a tester, and one is employing competent operators who read and follow the manufacturer’s guiding material. A resource used in the composition of this article can be accessed at https://hubbellcdn.com/literature/BR09002E_Testing_HLineTools.pdf.
Again, portable testers are not a substitute for lab testing when it is required. Care, competent inspection and maintenance of hot sticks, plus silicone cloth wiping of the sticks, are effective in ensuring worker safety. Adding a portable tester to supplement hot-stick condition analysis, along with the inspection and wiping of hot sticks before use, is useful in the big picture of inspection protocols for your hot sticks.
About the Author: After 25 years as a transmission-distribution lineman and foreman, Jim Vaughn, CUSP, has devoted the last 24 years to safety and training. A noted author, trainer and lecturer, he is a senior consultant for the Institute for Safety in Powerline Construction. He can be reached at firstname.lastname@example.org.
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