October-November 2020 Q&A
Q: We have a crew performing pole change-outs with the line energized. They are suspending phases with a link stick and digger derrick to provide more clearance between phases to install new poles and hardware. The question is, can the operator leave the controls with the phase lifted? We thought they could, but it seems there has been a change to OSHA 29 CFR 1926.1417(e).
A: The good news is that you cited the wrong rule. Pole change-outs fall under the 1910.269 operation and maintenance rules. You cited the rule for construction (OSHA 1926). The operation and maintenance rule – found at 1910.269(p)(1)(iv) – states the following: “The operator of an electric line truck may not leave his or her position at the controls while a load is suspended, unless the employer can demonstrate that no employee (including the operator) is endangered.”
Of course, it’s not as simple as that. The likely intent of both the operation and maintenance rule and the construction rule is to give an operator a break from the seat for inclement weather exposure or water or bathroom breaks. The issue with the construction rule is that the lift must meet “all of the following,” which are these requirements: no other duties for the operator, the operator stays next to the lift equipment, the equipment is stabilized and locked down, and barricades block the fall zone. Those requirements reflect the Cranes and Derricks in Construction standard (1926.1417(e)). The only requirement with the operation and maintenance rule is assuring no one is at risk.
If we’re being honest with ourselves, most of the time the operator leaves the seat to assist with work, which compromises the construction rule. If we remember correctly, OSHA added the conditional language to the construction standard in 2014 to further restrict exceptions because they generally do not accept an unattended suspended load.
We don’t know for sure, but OSHA does broadly examine the nature of both operations and construction, so there may be a practical consideration for the difference between the rules. In construction, the work typically is estimated, engineered and planned ahead. A construction crew should have enough people to attend to all of the tasks. A maintenance crew often consists of fewer persons called on to perform tasks that are unplanned, and they may find themselves multitasking.
The bigger problem with the construction rule is that a violation negates the digger derrick exception and brings the operation of the digger derrick back into the 1926.1400 cranes in construction rule, allowing OSHA to cite violations of the crane standard, including licensed operator citations. In the operation and maintenance rule (1910.269(p)(1)(iv)), if someone gets hurt, you cannot argue that it was safe to leave the seat.
We are aware of two state OSHA cases over this rule. Both involved holding poles, and one was a cut-and-kick. In the construction case, the operator was holding a tag line when he got off the boom for a second digger swinging in a crossarm. Rigging failed, they lost the arm and two people went to the hospital. OSHA prevailed and cited the company under the cranes and derricks standard. In both cases, the crews did not address leaving the seat during their tailboards. In any event, leaving a suspended load should be well-examined beforehand as there is an obvious element of risk. It can be and is done safely every day, but there are rules, and we need to understand and follow them for good reason.
Q: What are the rules requiring a utility to install high-voltage signs on their jointly owned wood poles?
A: With any facilities owned by a utility, prevailing conditions and difficulty of access determine when warning signs are required. The basis for a warning sign is when hazardous facilities are accessible to unqualified persons who might not recognize a hazard exists. With access to facilities, there also is the condition known as “reasonable person,” where access is at ground level and low level of difficulty signs are required. These are locations – usually behind enclosures or barriers – that can be breached or crossed with moderate effort, like substations, vault doors and aerial banks on a ground-level pad that can be reached over.
The ANSI sign standards don’t specify exactly when signs are required, but they do have placement conditions. Where a fenced-in facility contains exposed electrical equipment, sign placement and size should be such that the sign can be observed and read at a safe distance from the hazard. Section 110 of the National Electrical Code contains requirements for conspicuous signage on entrances to rooms and other guarded locations that warns against entry by unqualified persons. Part C of Section 110 has the same requirements for high-voltage enclosures. The National Electrical Safety Code requires safety signs at the entrances and gates of substations and on the exterior length of fences and walls. Part 217 of the NESC addresses what are described as “readily climbable” structures. These include lattice structures that have braces that can be used as steps and climbed by almost anyone. The rule for these structures requires barriers as well as safety signs above the barriers warning of the electrocution hazards. All of these spaces are of some relative access at ground level. Normally, untrained persons could not ascend a pole without training, equipment or unusual effort.
To summarize, poles – unless they have steps installed at ground-access level – cannot be readily accessed except by trained persons who are expected to recognize the hazards noted above. So, for that reason, warning signs normally are not required on poles or structures. It’s up to the owner to decide if their facilities are accessible to untrained persons who would not normally be able to recognize a hazardous condition.
Q: Can an extendable hot stick or switch stick be used from the ground with direct contact to transmission conductors? We have extendable sticks marked by foot/inch and can’t find the manufacturer’s prohibition against such use. How do we decide what to do?
A: This is a hard question to address because we can’t find any direct references to application and applied voltages, even from the manufacturers themselves. If we get this wrong, Incident Prevention invites any manufacturer of collapsible sticks to contact us.
As to the question, we suggest that the answer comes from the design and application of hot sticks. If you read the manufacturers’ advertisements or cut sheets for their collapsible sticks, they describe the top-end section as being the part of the stick that provides insulation for maximum protection. All of the stick specs we looked at stated that their insulating sticks met ASTM F711, which is the standard for foam-filled fiberglass hot sticks. There may be additional references for certification in cut sheets, but we didn’t find them. We looked specifically for references to compliance with ASTM F3121, which outlines certification and testing of hollow tube sectional insulating sticks. Certification or not, each of the ASTM standards uses disclaimers stating the following: “This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.”
We did find references to minimum collapsed length for hot work and references for a safety lock on the end section to ensure maximum protection provided by the foam core section. Reading between the lines, it seems that there are some limits that should be imposed on the voltages contacted across the hollow sections. Certainly, and not unexpectedly, manufacturer use specifications take into account limitations for liability worst-case scenarios. So, that brings us to the insulating value of the tested foam-filled section.
Foam-filled sticks are designed at 100,000 volts per foot and in-service tested at 75,000 volts per foot. This would suggest that the only reliable insulating section is the 4-foot-long foam-filled section. Extrapolating the combined length tested, we would be at 300,000 volts, but we are not sure it is technically appropriate to assume a cumulative total electrical rating since none of the technical testing standards address that. Be cautious when using this method for extendable/telescoping sticks. Ensure all water is drained prior to the electrical test.
Part 5.3 of the ASTM F3121 in-service maintenance guide requires internal wiping of collapsible sections to ensure against flashover. As such, the best practice is to only make contact with circuits within the test voltage, which is 75,000 volts per foot for in-service testing. Generally, with the above information in mind, our experts who validate iP’s Q&A section agree that contact above 69 kV should be avoided unless the employer can assure that sticks are disassembled and internally wiped before use.
We also suggest non-contact measuring as a better practice. A tool some 60 years old made just for that job is the Chance Teleheight and tape measure that uses the much older Pythagorean right-angle formula to determine wire height. It costs about $40 and certainly won’t flash over in use. Of course, there are some electronic range-finder measuring tools for hunting and shooting that can be repurposed for measuring conductor height.
Q: What is the best resource to get up to speed on three-phase pad-mount transformer grounding? One of my supervisors asked about grounding three-phase URDs using grounding caps on the bushings on one side, closing the feed-selector switch and relying on the switch to ground both primary sides. I’m uncomfortable with that, but it’s been a long time since I’ve had to do it. It is my understanding that we should not be relying on switches; we should ground both sides with two sets of three-phase grounding elbows. Can you help?
A: Technically, your supervisor is grounding the circuit. If it was working before you switched it out, it might be reasonable to assume it’s closing properly now. The problem is that you have no way of knowing if the internal switch is connecting all three phases together since they are not visible. The visibility part is the problem with most observers. There is no rule against grounding through a switch that’s visible. We do that every time we ground an overhead bus when there are dozens of disconnect switches between our location and the substation. We can’t see them, and nobody checks them, but we don’t seem to have a problem with that.
The work to be done matters, and the method you described as pulling an elbow on either side of the switch means that cable is no longer grounded unless you are using a grounded bushing for the cables. If you are not working on the cables, parking them is acceptable.
If they are working on the transformer and cable, the best idea to protect the worker is to isolate both feeds at the nearest source, park the elbows and disconnect the neutrals for the isolated cable. The neutrals are part of the system, and not isolating them creates a fault current path into the work area if a fault occurs on a different part of the system. We must work it hot (not a choice here), isolate it or ground it. The problem with grounding is that it doesn’t necessarily protect the worker if it isn’t equipotentially bonded, which is now required by OSHA rules (see 1910.269(n)(3)). Of course, there really is no way to equipotentially bond the elbows together, which is why OSHA allows isolation as a means of protection. This is especially so if they are working on the cable (see 1910.269(n)(2)).
Q: In the world of grounding, what is meant by “balanced,” “balanced chain” and “imbalanced chain”?
A: These words describe the manner of connection of three-phase grounding. The value of the descriptions has to do with equipotential arrangements and the voltage between phase and pole that develops if a fault should occur on the grounded circuit.
With equipotential bonding, the goal is to keep the voltage that rises during inadvertent energizing low enough that the worker between the pole and grounded phase will not be injured. There is no such thing as perfect equal potential because there is resistance in the bonded system, and resistance results in voltage rise across the bond connection. That resistance will create a slight difference in voltage between the pole and the grounded phases. This voltage is very low and, though measurable, is too low to be detected by the worker. But that voltage is dependent on resistance in the connected system. The more resistance, the higher the voltage difference will be between pole and phases. This is especially so if the grounding of the bus is a span or two away from the work location. If the phase being worked on is bonded to the pole at the work location, that phase will have very low voltage between phase and pole. If the other two phases are not bonded to the pole at the work location, the pathway to pole bonding is down the span to the grounding jumpers and back through the phase that is bonded to the pole at the work location. In that arrangement, the two phases not bonded at the work location will have a higher voltage between pole and phases because of the distance across the spans.
Now, back to the connection descriptions. “Balanced” means each phase is connected independently to the pole, and each bonding jumper being the same length means the voltage between each phase and the pole will be the same, as will the voltage between phase to phase.
“Balanced chain” means the center phase is bonded to the pole and the two outside phases are bonded to the center phase. In this arrangement, the center phase will have the lowest phase-to-pole voltage, and the outside phases will have a slightly higher voltage phase to pole because of the added resistance in the path to the pole.
The “imbalanced chain” will have an outside phase bonded to the pole, and the remaining phases will be series connected to the grounded phase. In this arrangement, the outside phase will have the lowest voltage phase to pole. The next phase connected will have a slightly higher voltage than the first. The last phase will have the longest path to ground, so it will have the highest voltage between phase and pole and the highest voltage difference between grounded phases of all three systems.
Does it matter? Not if your connections are clean and your cables are short. The voltage differences are very low and typically inconsequential if diligent application of grounds is undertaken. The highest voltage that could rise to the level of risk is when grounds are a couple spans away and only one phase is bonded to the pole at the work area. Also, don’t read too much into the balanced application. The balanced connections are three independent connections to ground, which means that all three phases are dumping their peak fault current into the ground connection on the pole. In the chain arrangements, a large portion of the fault current circulates within the three-phase chain, limiting current to ground at the pole connection.
Do you have a question regarding best practices, work procedures or other utility safety-related topics? If so, please send your inquiries directly to firstname.lastname@example.org. Questions submitted are reviewed and answered by the iP editorial advisory board and other subject matter experts.
- Leading Change Through Faith, Hope and Tough Love: Part I
- Creating a Culture of Safety Through Elite Leadership
- Line and Substation Insulator Refresher
- When OSHA Electric Power Safety Standards Apply
- A Practical Review of the ANSI A92.2 Standard
- Inspect and Test to Prevent Wood Poles from Falling
- October-November 2020 Q&A
- Emotional Intelligence: Perceive and Apply Emotions in Yourself and Others