October-November 2024 Q&A
Q: We are looking for some direction and opinions regarding SF6 gas switches. The SF6 switches we use on our campus are older and starting to pose problems. Some are leaking and others are very difficult to operate. Can you help?
A: Sulfur hexafluoride, or SF6, isn’t a topic or problem we can effectively deal with in this venue, but we can offer some direction along practical lines as SF6 has greatly fallen out of favor with regulatory agencies and – as a result – the industry as a whole. We understand that several states have SF6 “remove from service” dates on their environmental calendars.
SF6 is nontoxic and nonflammable, but it is a huge issue among environmentalists as a primary greenhouse gas contributor. If your SF6 gas switches are leaking, you must get that under control or expect to become a target. Again, SF6 is nontoxic, so a leak is typically no issue for employees, but it can displace oxygen in confined spaces at lower levels.
The biggest mistake we recall seeing with recharging SF6 is overpressure in the refill injection. Overpressure can stir up debris in the chamber and cause a flashover inside the breaker.
We suggest performing an audit of your breakers to begin a replacement program. Get a manufacturer’s engineer to assist you; the engineer can help develop a checklist to determine remediation or replacement of those breakers that can be rehabbed. Of course, the engineer would be glad to replace all of them, but that includes a big SF6 hazardous disposal hit, too. The engineer should be able to help you set up an assessment matrix for replacement orders.
The International Electrotechnical Commission specification for SF6 – IEC 60376 – is a universal standard that provides good guidance on handling used SF6. Keep in mind that the IEC guide is not U.S. law. Many states have greater restrictions on control of SF6.
Q: Does OSHA prohibit lifting of hot-line clamps to make or break loads? The rule reads as follows: “(i) The employer shall ensure that devices used by employees to open circuits under load conditions are designed to interrupt the current involved. (ii) The employer shall ensure that devices used by employees to close circuits under load conditions are designed to safely carry the current involved.”
A: This rule is often mischaracterized both by wording and intent as prohibiting opening or closing under load using a non-load-break switch or a bare hot-line clamp. The rule does prohibit opening or closing a switch or hot-line clamp (device) under load if an employee performing the task could be injured by the act. If the employee can safely perform the act, there is no violation.
To explain, there are two keys to properly interpreting this rule. One is the location of the rule. It is found in 29 CFR 1910.269(l), “Working on or near exposed energized parts.” The purpose of the paragraph is protection of employees, as stated in this sentence following the section’s title: “This paragraph applies to work on exposed live parts, or near enough to them to expose the employee to any hazard they present.” Paragraph (l) is about protecting employees.
When OSHA reviews potential violations of the standard, they typically consider three issues: whether a rule existed, if the employer knew about the rule and if an employee was exposed to danger by violating the rule. The agency will also review consensus standards and best practices as well as non-adopted consensus standards, which are sometimes used in de minimis conditions and General Duty Clause violations. We know this because when we read public notice citations, we find non-adopted consensus standard language used in the notice of violation without reference to the non-adopted standard. Returning to the intent of the OSHA standard, in this case, the intent of 1910.269(l) is to prevent injuries to employees. In the case of non-load-break dropout switches that have been opened under load using hot sticks millions of times without injury, the case for safety is not difficult to argue.
As a rule, most utility safety procedures would have some established guidance limits on lifting hot-line clamps simply to prevent damage to stirrups or hot-line clamp jaws that result in hot spots and continuing problems. We are aware that some utilities generally prohibit operating hot-line clamps under load, but we are not aware of any utilities that prohibit opening dropouts. In many cases, dropouts do come with load-break tool hooks. Load-break tools are typically used on unswitched capacitor banks and heavier loaded banked transformers. Still, all of these tools and devices are operated from the safety of a shotgun switch stick. Both the hazards and the techniques to safely open a switch or lift a hot-line clamp have been understood since Tips Tool Co. delivered the first clamp stick and hot-line clamp in 1918.
Lastly – to support the employer’s argument for safety in opening non-load-rated switches or taps – is an obscure OSHA response to a 1996 question (Question 26) submitted by Michael L. Harbaugh (see www.osha.gov/laws-regs/standardinterpretations/1996-03-26-3). In the response, OSHA reviewed the reasons for load break and hazards that exist if a non-rated switch should fail in operation. The last part of the OSHA answer states the following: “The employer would not be cited for a violation of paragraph 1910.269(l)(10) when employees are not exposed to the hazards involved. This would be the case if the non-load-break disconnecting device was operated from a remote position from where the employee using the device nor other employees could not be injured in the event the device failed.”
Q: Are insulated elbows in a pad-mounted, dead-front transformer considered insulated for the purpose of employee protection? In other words, is it legal to touch or handle a hot elbow with rubber gloves?
A: This is a question that comes up often. We still have instances where workers are manipulating dead-front elbows with rubber gloves, and they are getting hurt doing so.
Anyone who reads the OSHA literature or rules knows the agency qualifies “insulated” and “insulation” differently according to the application. OSHA 1910.269(x), “Definitions,” is not the first place everyone goes when trying to understand OSHA rules, but it should be near the top of the list of research resources. Here are definitions from that section for “insulated” and “insulation” that apply to the question:
Insulated. Separated from other conducting surfaces by a dielectric (including air space) offering a high resistance to the passage of current.
Note to the definition of “insulated”: When any object is said to be insulated, it is understood to be insulated for the conditions to which it normally is subjected. Otherwise, it is, for the purpose of this section, uninsulated.
Insulation (cable). Material relied upon to insulate the conductor from other conductors or conducting parts or from ground.
It is worthwhile here to note that what the “insulation” definition does not state is “making it safe to touch.” To further confuse the issue, OSHA 1910.269(t) allows moving cables by hand after inspecting them, stating the following in 1910.269(t)(6), “Moving cables”: “Except when paragraph (t)(7)(ii) of this section permits employees to perform work that could cause a fault in an energized cable in a manhole or vault, the employer shall ensure that employees inspect energized cables to be moved for abnormalities.” Paragraph 1910.269(t)(7) has a listing of observations and practices designed to minimize risks for failing cable. Despite the provisions of (t)(7), we say don’t move energized primary cable. De-energize it.
Now, back to the question of elbows. Manufacturers refer to dead-front elbows as insulated. Using the definition as provided by OSHA, that would mean “for the conditions to which they are normally subjected.” However, all of the literature provided for installation and operation of dead-front terminals repeats throughout that no one should touch energized elbows at the risk of serious injury or death. The manufacturers’ literature does not include exceptions like using rubber gloves; simply do not touch the elbows. It would seem then that the conditions normally subjected to would include “not to be touched.” That instruction alone is the basis for a policy or procedures prohibiting contact. The manufacturers also instruct users to follow state, federal and industry consensus practices for safely operating the devices. Then the issue is that unless a state operating rule prohibits touching dead-fronts, the federal standard by definition does not prohibit touching elbows. The exception would be from the numerous references throughout the standard to follow manufacturer design and operating instructions, although that instruction does not appear in any references that we can find in dealing with insulated parts.
Finally, there is one interpretation available that seems to follow the observations made so far. Our research again brought us to a request for interpretation, this time in a 2006 letter sent to OSHA by Michael L. Harbaugh (see
www.osha.gov/laws-regs/standardinterpretations/2006-04-25-4). In their response, OSHA mentions a number of issues with the integrity of the insulation of elbows, including issues with leaking and poorly functioning drain wires that compromise the safety of the insulated elbows, closing with this instruction to Mr. Harbaugh: “Consequently, OSHA generally considers the elbow as not safe to touch with bare hands, and the employee would have to maintain a minimum approach distance of ‘avoid contact.’”
Q: Our company safety rules require that we test grounds yearly. We have been sending them to a lab to certify the tests, but economically, having increased the number of grounding cables by 600% in the last six years, both the turnaround and expenses are getting hard to manage. Our management seems to think testing must be performed by a testing lab. Can you help us understand the rules?
A: Testing and inspection to ensure grounds perform effectively is critical in assuring that the grounds perform as designed. Many companies, recognizing how important testing is, have adopted off-site testing – and over the years, many people have simply assumed that a certified lab is required. That’s not the case.
OSHA does not dictate testing methods or intervals for testing grounds, nor have they adopted any of the referenced standards for testing of grounds. That means the guides we use from IEEE and ASTM are not mandatory, but using them as guides is the right thing to do. OSHA does refer the employer to the IEEE and ASTM guides as “references” for information. There is some diligence and conscientious performance required to test grounds, but training and careful selection of personnel to do the testing are effective and expedient ways to keep grounds tested and ready for use in the field.
There are several test units available on the market. Buyers should do their research to determine which will provide the test criteria they need. DC units perform a DC resistance test. DC is not subject to induction or reactance, so a ground being tested by DC can be left coiled during the test. An AC test measures impedance, taking into account clamp spacing and arrangement of the cable, and can even be affected by the metal tube on the interior of a plastic or PVC table under the ground cable being tested. An AC test may be a better indicator of how a cable will perform in the field.
Besides AC/DC, there are essentially two ways to test your grounds in practice by utilities. One is the low-current ohm value method combined with a qualified visual inspection. The other is the full-current method. Both provide necessary information about the integrity of the grounds, and the information derived should be calculated into the peculiarities of the system they will be used on. Many grounds testers using low-current values simply show a pass/fail result. In reality, if we know the test values and the available system fault values, we can calculate risk to the worker and develop procedures and methods to provide the best possible protection.
High-current testing produces a two-part result and was considered by many to be a preferred method. The full-current test impresses a current across the ground under test, usually up to 200 amps, and will stress any poor connections to a degree not possible in a low-current ohms-resistance test. Comparisons of the two methods have regularly shown current testing to reveal connection issues not revealed in a low-current ohms test. Earlier editions of IEEE 1048, “IEEE Guide for Protective Grounding of Power Lines,” had discussions of grounds testing, including a discussion of high-current testing values, but eliminated that section from the most recent edition. For testing, IEEE 1048 now refers the reader to ASTM F2249, which does not describe in detail the value or process of high-current testing. ASTM does, however, include Annex B, which describes how high-current tests use the electrical stress imposed on the cable to proof-test the cable connections; this is done by performing an infrared scan of the cable after high-current loading it to check for hot spots that low-current resistance testing will not reveal. You will find the full-current test discussion and procedures in IEEE 1048-2009. Most high-current testing machines we are familiar with provide a graph associated with current rise and results in voltage drop calculated at maximum-rated fault current for the cable under test. Since voltage drop is critical in determining voltage across a lineworker, these readings are often preferred over impedance of a cable.
Do your research and select your test equipment in accordance with the needs of your system. Train your test operators to perform diligent and conscientious testing. It will pay off.
Do you have a question regarding best practices, work procedures or other utility safety-related topics? If so, please send your inquiries directly to kwade@utilitybusinessmedia.com. Questions submitted are reviewed and answered by the iP editorial advisory board and other subject matter experts
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