The Case Of the Ladder & Line Collision
Sometimes when human nature and human-made technology collide, what we know we should do and what we actually do often end up causing injury or death. Contact with power lines is a perfect example. Although most adults are very much aware that contact with a power line is quite dangerous, if not lethal, such contacts continue to occur each year. One interesting aspect of many of these instances lies in the fact that the victims knew — at some point — that the power line was there; they may have even made a mental note to stay clear of it. In this case, we explore an accident where an individual made contact with a power line in the course of his work. He knew power lines were dangerous; he also knew the power line was present at his work site. Tragically, the result of the contact was lethal. The result of the litigation that followed was surprising.
A self-employed painter, the victim was hired to paint a rural church. Surrounded by fields, the church property sat near a road that ran past the structure, separating the property from the fields across the road. Power was delivered to the church via a 7.2kV service drop.
The distribution lines delivering power to the church ran for a great distance along the opposite side of the road. Approaching the church, the 7.2kV line was brought across the road to power poles that then paralleled the front of the building. At the point where the power line was contacted by the victim, the power line had a horizontal clearance of 15 ft from the building, which was permissible under local code. The power line had a vertical clearance with the ground of just under 24 ft. The question of which came first — the power line or the building — was never clearly answered. The fact that the power lines crossed the road for no other apparent reason than to create specific proximity to the building suggested that it was designed to be proximate to the church and to minimize the length of the service drop. It was this proximity that ultimately led to this electrical contact incident.
The victim arrived at the work site, accompanied by his wife, who served as his helper. Preparing the surface for painting, he began pressure washing the church first, using a 32-ft aluminum ladder. Each time he needed to move the ladder, instead of lowering and raising it again, he angled the ladder upward and then moved it as necessary. Presumably, this was done to save time and unnecessary motions. Absent the proximity of the 7.2kV line, this method of repositioning the ladder posed no obvious risk.
At the instant of the contact, the victim was in the process of moving the ladder. The 32-ft ladder was upright, extending beyond the height of the power line. The sole witness to the incident, the decedent’s wife, offered testimony that her husband was standing with arms outstretched, holding the ladder. Before collapsing to the ground, he asked, “What happened to me?” Efforts to perform CPR were unsuccessful, and the man died without ever regaining consciousness.
Upon further examination, entry burns were noted on the decedent’s hands, as were exit burns on his feet. Burns were also noted on the ladder, and there was a contact mark on the power line. Describing the sound of the contact as a load roar, the witness explained that the contact lasted for a significant duration, during which time the decedent appeared unable to release the ladder, until he fell free from the connection several seconds later.
The decedent’s wife (plaintiff) and estate sued the electric utility (defendant), alleging that it was negligent by failing to reduce hazards, follow good engineering practices, and take local conditions into consideration. I was retained by plaintiff’s counsel to serve as an expert in the areas of electrical engineering, pain and suffering, and human factors.
The defendant argued that it had met all statutory clearance requirements in its design of the power distribution system at the point of contact. Electric utility representatives also argued that the decedent was liable for his own death, because he’d placed the ladder in proximity to the power line in violation of local code. (Note: In most power line contact cases, defendants correctly take the position that for the contact to occur, the plaintiff would have had to have violated OSHA guidelines/local code by coming into close enough proximity to the power line to cause the contact.)
As noted in OSHA Standard 1910 Subpart S, unqualified personnel maintain a clearance at least 10 ft from overhead power lines rated 50kV or less. Section 1910.333(c)(3)(i)(A) states: When an unqualified person is working in an elevated position near overhead lines, the location shall be such that the person and the longest conductive object he or she may contact cannot come closer to any unguarded, energized overhead line than the following distances:
(1) — For voltages to ground, 50kV or below: 10 ft (305 cm);
(2) — For voltages to ground more than 50kV: 10 ft (305 cm) plus 4 in. (10 cm) for every 10kV greater than 50kV.
For more information on this standard, click HERE
Investigation and analysis
After analyzing the accident details and considering testimony of the witness, I concluded that this was a significant shock, amounting to more than instantaneous duration, and estimated the current at 7A. (Note: Current was derived by applying Ohm’s law. The voltage was 7,200V with 1,000 ohms used as a typical value for human resistance, thus yielding a current calculated at approximately 7A. Human resistance can vary wildly. In shocks such as this, resistance can be much lower, once the current breaches the skin barrier, which leads to much greater current flow than my conservative calculation of 7A.)
Based on the parameters of the shock, coupled with the fact that the witness indicated that the decedent had cognizance of his injuries before his death, I offered testimony that it was likely that the victim experienced significant pain and suffering prior to losing consciousness. In contacts such as this, it is probable that the cause of death was electrically initiated ventricular fibrillation. It is generally accepted that individuals who die from electrically induced ventricular fibrillation have a period of 10 sec to 30 sec in which they have an awareness that would include a knowledge of their plight and awareness of pain from the electricity and electrically induced burns. In the state in which this incident occurred, the plaintiff could collect damages for pain and suffering, even if the pain and suffering were extremely brief.
The biggest question to be argued in court was that of liability. Electric utilities spend considerable time and money educating the public. They disseminate electrical safety information in the schools, through public service announcements, through advertising, on their websites, and through inclusion in monthly electric bills. Arguably, no adult should be able to claim that they are unaware of the danger of power lines. It’s also debatable that anyone who uses ladders as part of their profession has a duty to inspect the work area for risks, such as proximity to energized power lines. Certainly, they have a duty to adhere to OSHA guidelines regarding power line clearances. In addition, all aluminum ladders have a clearly displayed warning label regarding electric shock risk.
Assuming that the decedent did a proper inspection of his work area, he would have been aware of the presence of these power lines. Assuming that the power lines had proper horizontal and vertical clearances as per code — and assuming that the decedent had adequate education as to the risk present from such power lines and was at least slightly aware of OSHA guidelines — it would seem impossible for the electric utility to be held liable for this type of power line contact. However, in cases such as this, I maintained that human nature often conflicts with the presence of human-made technology.
In my opinion, electric utilities, having superior knowledge to that of the general public, have a duty to consider human nature in the design of their power distribution systems. It was my testimony that such knowledge required a design that superseded mere adherence to code. Explaining to the jury that these types of cases are not only foreseeable but also probable, humans often know of the presence of power lines but are then shortly thereafter injured by them. I call this the “wet paint phenomenon.” One paints a wall, knows that the paint is wet, but shortly thereafter comes back and touches the wet paint without thinking.
Humans are designed to focus their finite reservoir of processing powers on the tasks at hand and rapidly start to exclude facts of ancillary importance. For a painter, the task at hand is his job, while the presence of power lines above and behind him becomes ancillary very quickly. Humans are also not designed to see static objects in the periphery of their visual field. Power lines are both static and in the periphery. We sense objects in the periphery of our visual field with the rods in our eyes. Rods are designed to detect objects in motion. This is most likely an evolutionary defense mechanism to detect attacks from the sides or above. Historically, static objects rarely pose a threat. As such, for humans focusing on their work, power lines rapidly become invisible.
Taken in totality, I testified that the electric utility should have foreseen this type of accident, considered human factors, and had a duty to go beyond mere adherence to the code. Had it placed the power lines a greater distance from the building, honoring the human factors that could come into play, the victim would not have died that day — as the openness of the area would have made it easy to dramatically increase horizontal clearances.
Examination indicated that the service drop cable to the residence had a severed neutral, as shown on Photo 1. The failure of the neutral conductor appeared to be caused by deterioration due to age and possible contact with tree limbs. Examination of the coaxial cable indicated melted insulation on a bend (Photo 2), indicative of heat caused by current flowing through the shield.
The cable technician testified that when he measured the voltage on the coax shield, he got readings of 20V to 35V, which was not normal. He called his supervisor to discuss the situation and was told to remove the ground connection. After removing this connection, the voltage measurement increased to 200V on the shield. Realizing this created an even bigger problem, he reconnected the ground and again called his supervisor. After another discussion, the technician was directed to cut the coax (although the reason for this action was not provided).
Theoretically, electrical current flows through all bonding and grounding connections to return to the electric utility transformer. The lower the resistance path, the more current will flow. The neutral conductor in the service drop cable provides the lowest resistive path to the transformer. When the neutral wire in the service drop cable was severed, electrical current sought other paths to return to the transformer. Those paths included the ground, through ground rods and a water pipe, and the cable shield that was bonded to the neutral on the electric utility pole where the transformer was located. Current flowing through the shield created heat that caused melting of the jacket. Losing the neutral also eliminated the 0V reference so that voltage on one line conductor increased while voltage on the other line conductor decreased. This resulted in the dimming and brightening of lights.
The case was settled prior to trial, the terms of which were confidential. However, several lessons can be learned from the sequence of events in this case.
The lineman was aware of the dimming light problem and that it could indicate a problem with the neutral, but he did not investigate further since the service drop cable was owned by the homeowner. Although he saw deterioration of the cable, he testified that if he had visually identified a severed neutral conductor he would have de-energized the transformer until cable repairs were made, which would have prevented the fire.
The cable technician testified he was aware that lights dimming and a melted jacket on the coax were indications of electrical problems. Furthermore, measurements indicating voltage on the cable shield also indicated an electrical problem. Therefore, he should have told the homeowner to call an electrician. If he had done so without cutting the coaxial cable, the fire would not have occurred. It was also noted that the cable technician violated OSHA requirements by cutting the coax (i.e. working on energized equipment without wearing personal protective equipment).
SIDEBAR: Importance of the Neutral Conductor
Electrical current typically flows from an electric utility transformer into a residential dwelling unit’s panelboard. From there, it flows through individual branch circuits to end-use receptacles. For 120V loads, the return path back to the utility transformer is the neutral conductor. If the neutral conductor is severed, the current seeks other paths to return to the transformer. One path is through the earth, since the neutral at the panelboard is connected to a grounding electrode conductor that is connected to a ground rod. Of course, the electric utility transformer also has its neutral connected to a ground rod at the utility pole. Another available current path is the shield on a coaxial cable, which is also connected to ground rod at the house as well as to the neutral on the electric utility pole.
The neutral provides a 0V reference. When the neutral is severed, this reference is lost, and voltages can exceed 120V — depending upon the loads connected to each branch circuit. As in this case, this situation can cause some lights in the house to be brighter and some to be dimmer. Changes in higher loads, such as refrigerators or air conditioners turning on and off, can also cause lights to brighten and dim. In addition, higher voltages on the branch circuits can damage appliances.
In the final analysis, the jury agreed with the plaintiff. The jury was given the option to consider applicable code, but could also consider if circumstances dictated that the defendant had a greater duty. The electric utility was found 85% liable, while with the decedent was deemed 15% responsible for the incident. The jury awarded $4.85 million to the plaintiff, including more than $3 million in punitive damages. (Punitive damages are awarded to punish or make an example of a defendant who the jury deems has gone beyond mere negligence to behavior that is willful or wanton.)
This case teaches us several lessons. Anyone who purveys a technology in which they have greater knowledge than the end-user has a duty that goes beyond meeting minimum standards and adhering to applicable code. Human factors and the nature of human interaction with technology must always be considered when making electrical design decisions. Expecting humans to adhere to ideals that exceed the nature of human design and performance is a recipe for disaster and liability. Mere warnings are never enough and should always be considered a last resort.
The best design is one that takes the risk out of the reach of those near the technology. Liability is foreseeable when designers rely too heavily on end-users to act to prevent injury. For the individual, knowing a bit about your own human nature can be a lifesaver. Knowing that power lines will become invisible, it never hurts to ask the electric utility to put protective shields on wires or to de-energize wires that might pose a risk. In the end, it all comes down to good design choices made with a broad consideration of all foreseeable risks.
Dr. Morse is an academic, researcher, and consultant who has reviewed hundreds of electrical injury cases. A full professor of electrical engineering at the University of San Diego, he can be reached at: DrMMorse@ElectricalInjury.com.