Designing for Electrical Safety

When it comes to electrical safety in product and system design, merely following the code, statutory standards, or other regulations without deeper analysis can almost guarantee you an invitation into the legal forum. Similarly, expecting human behavior that contradicts human nature inevitably can lead to litigation as well. The bottom line is expecting that a product will not cause injury — no matter how innocuous it may be — is a recipe for disaster. Therefore, it's critical to use a well-defined design process that complies with legal standards.

Unfortunately, few engineers come to understand or really appreciate this aspect of the design process prior to finding themselves in a courtroom. Although engineers need not be lawyers, they do need to understand how the law views the process of engineering design. For any product or system that brings electrical energy into close proximity with human users, the risk of electrical injury must always be deemed “foreseeable.”

Design considerations must be constructed upon knowledge of foreseeable risks from intended as well as unintended uses of the product or system. To comport with legal standards, foreseeable modes of failure must be identified and dealt with before the product or system ever enters the marketplace. Negligence in design attaches when the design process fails such that the designer's duty to follow the appropriate and proper design procedure has been breached.

The risk of electrical injury and ensuing litigation can be decreased by considering the design process in the context of the current legal environment. Electrical safety experts need to learn how to view design for electrical safety as it may someday be viewed in a legal forum. The ultimate goal is to better approach their responsibilities and maximize the safety of the electrical environment while minimizing liability exposure.

Attention to detail

The engineering design process, as defined in most engineering texts, may vary slightly. However, it generally contains a methodology consisting of the following:

1. Identification
2. Problem definition
3. Search
4. Constraints
5. Criteria
6. Alternative solutions
7. Analysis
8. Decision
9. Specification
10. Communication.

Simply stated, engineering design is an iterative process whereby the final product or system is reached through the process of design, analysis, and redesign until the final design (the optimal balance among all competing considerations) is reached.

Negligence

This term is defined as “The omission to do something that a reasonable man guided by those ordinary considerations, which ordinarily regulate human affairs, would do, or the doing of something that a reasonable and prudent man would not do.” The duty is defined in the context of what a reasonable person in a similar position would do.

Negligence in engineering design arises when an engineer fails to do what a reasonable engineer would have a responsibility to do in those same circumstances. Thus, to avoid negligence, it's important for an engineer to avoid failing in his duties. The question that is always difficult to answer when looking into the future is: How will a jury of non-engineers define an engineer's duties when examining in hindsight?

Engineering design, duty, and negligence

To understand how negligence arises in engineering design, it's critical to focus on the “analysis” step in the design process. Design analysis includes every aspect of design review — from considering whether the design meets technical specifications to an economic analysis, to an extensive study of product safety. The goal for the reasonable engineer is to hone in on the design of a safe product that meets the needs of the target consumer.

It is the analysis step of design that puts lawyers and engineers forever on a collision course. Engineers typically view design prospectively while lawyers look at design in retrospect. Engineers are taught that designs must be safe. Lawyers look to see if the design was negligent. Engineers are taught to design for the target consumer. Lawyers consider if the design was reasonable when considering a single consumer (their client), who has been injured.

When there is an injury, the battlefield is the courtroom, and the jury gets to choose who wins the war. The language between the professions may be different, but the goal is ultimately the same. The engineer must design a safe product/system for a reasonable consumer. The lawyer is tasked with testing the sufficiency of the design to see if it did, in fact, breach the legal standard for negligence, which, by default, makes the product or system unsafe in the eyes of the law.

Avoiding negligence

The engineer is seeking safety with the underlying (and often unstated) goal being to avoid negligence. Although taught in many different ways, the approach to minimizing liability exposure is largely the same for all design work. It requires identifying and managing the risks associated with all foreseeable uses and misuses of the product as part of the engineering design process. If the risk associated with a foreseeable mode of product failure is significant, such as the risk of substantial injury or death, proper design dictates that the engineer must modify the design per the following protocol (sometimes referred to as the “safety hierarchy”):

1. The risk must be removed by changing or altering the design.

2. If the risk cannot be removed, then the design must be altered so the device or system will fail on the side of safety.

3. If the device cannot be designed to fail on the side of safety, then adequate warnings must be provided so that those in proximity are appropriately made aware of the risks. Warnings must never be used as a substitute for good design (Steps 1 and 2) but, if used, should be used only as a last resort.

Good design ultimately hinges on knowing what should be foreseeable to a reasonable engineer and how a reasonable consumer will use (or misuse) the product/system. It all hinges on having a true understanding of what creates “reasonableness.”

Designing for the reasonable consumer

In order for a designer to assess foreseeable risk, he or she must know what defines a reasonable consumer. This is clearly a moving target that must consider the pool of consumers, the nature of their interaction with the design, and the scope of risks posed by the design. The definition of a reasonable consumer who might purchase a surgical tool used only by physicians is vastly different than the reasonable consumer purchasing a shovel at a home repair warehouse.

When designing for electrical safety, knowing all foreseeable end-users becomes critical. Providing a product to be used by individuals trained to interact with electrical systems (such as linemen or electricians) sets a vastly different bar than providing products or systems to be used by or interacted with the general population. Placing erroneous expectations on the reasonable consumer sets the perceived bar for negligence at the wrong level.

One example that has been litigated with mixed results involves cases where laypersons contact power lines with ladders. The California Public Utility Commission reported 17 “ladder-related contacts” from the period of 1989 to 1997. On its face, it seems hard to blame the power companies when they spend an incredible amount of money on public campaigns to make people aware that power lines are lethal. All cities have codes mandating that power lines not be in vertical or horizontal proximity to structures. Ladders all have warnings about power line contacts. Still, these incidents occur with considerable frequency. Is it possible that the power companies are negligent in failing to understand their reasonable consumer?

Research has demonstrated that humans, even with knowledge of the risk posed by power lines — and even when acting with normal and reasonable diligence — can still contact overhead power lines because of the nature of human design and physical limitations. Accepting these facts as true, it becomes arguable that the power companies are negligent when they fail to consider all aspects of human nature and thus erroneously define their reasonable consumer.

A second example occurs when those designing for electrical safety fail to consider all that defines the current state of science regarding risk of injury from electrical contact. The current state of science dictates that contacts once thought to pose little to no risk can cause (in a small number of cases) long-term and debilitating injury. Still, the design of many systems and products relies solely on risk curves that are now antiquated and are not all inclusive when defining the limits for risk. Therefore, the response of the reasonable consumer is not properly anticipated. The designers have a duty to use the most modern definitions for the risk of harm during the analysis phase of their design process. When design is done properly, foreseeable injury should be abated and liability reduced, if not eliminated.

Final thoughts

For those designing for electrical safety, the magic word becomes foreseeability. The designer must be able to foresee modes of failure, the risks they pose, and who will ultimately consume or interact with the design or system. Not only must the design be forward looking with regard to issues of safety, but it must also consider how a jury of laypersons will look at the actions of the engineer in the context of the adversarial legal environment where every aspect of the design process will be questioned and tested. There is no guarantee that following a bulletproof process will yield bulletproof results; however, this strategy will create a position that is far more defensible in a courtroom, which will hopefully reduce the risk of injury and lessen the chance of you ever reaching the courthouse steps.

Morse is a researcher, consultant, and full professor of electrical engineering at the University of San Diego. He can be reached at [email protected].

Based on “Designing for Electrical Safety That Can Withstand Legal Scrutiny,” by Michael S. Morse. © 2009 IEEE.