Critical power environments often rely on highly trained professionals to maintain worker safety while protecting facility equipment. “Safety by design” describes a comprehensive approach, incorporating practical and feasible electrical distribution saftey designs.
This concept can be examined by first understanding the three pillars of success for electrical safety.
- Eliminate hazards by establishing electrically safe working conditions.
- Implement designs that reduce the likelihood of a hazardous occurrence.
- Reduce the potential severity of injuries should an accident occur when justified energized work is required.
When the mission critical industry aims its focus on all three of these pillars, the result is safer conditions for electrical workers and better-protected equipment.
Eliminating Hazards
Every electrical product and system must be designed with worker and equipment safety in mind.
Hazard elimination is the act of establishing an electrically safe working condition. The National Fire Protection Association (NFPA) 70E committee provides clarity around this topic with its definition of an electrically safe work condition, which reads as follows:
“An electrically safe work condition is not a procedure; it is a state wherein all hazardous electrical conductors or circuit parts to which a worker might be exposed are maintained in a de-energized state for the purpose of temporarily eliminating electrical hazards for the period of time for which the state is maintained.”
Establishing an electrically safe working condition is critical. While de-energizing equipment is an important goal, a worker will always have to dress in appropriate personal protection equipment (PPE) and use a test instrument to verify the absence of voltage. Lock-out/tag-out procedures have to be followed, and these can range from simple to complex.
In fact, there can be situations (e.g., verifying absence of voltage) when there isn’t PPE with a rating high enough to protect the worker. For those situations, it is imperative to incorporate system designs and solutions that minimize the likelihood of an occurrence and the severity of injury should an accident occur.
Reducing the likelihood of occurrence
There are many different layers of safety precautions that can be put into place to reduce the likelihood of arc flash, arc blast, and/or shock. Below are seven important design considerations. If your facility is not currently designed to cover each of these areas, they can represent great starting points to create a stronger safety culture within your organization.
1. Electrical one-line diagrams
An important part of a facility’s electrical infrastructure life begins even before breaking ground. This document is developed and used by engineers, suppliers, inspectors, workers, and designers. Workers could be put at risk if one-line diagrams are not maintained and power system capabilities are not reviewed and updated as they change over time.
2. Barriers
Adding a local disconnect next to a panelboard or industrial control panel (ICP) that is accessed frequently for service provides electrical workers with clear visible indicators that the panel or ICP has been de-energized when the circuit breaker or switch is in the “off” position. When required absence of voltage testing is performed, the likelihood of an incident has been reduced.
3. Disconnects
By placing a circuit breaker or fuse and switch in their own enclosure next to the equipment, electrical workers have a readily accessible disconnect to remove voltage and establish an electrically safe working condition.
4. Visibility
Equipping a panelboard with a window that allows workers to visibly see the blades being disconnected aids in worker verification, reducing the likelihood of an incident.
5. Indicators
The presence of voltage indicators employed on equipment provides electrical workers a visible indication of which side of the disconnect is energized and which isn’t.
6. Knowledge
Information on the condition and maintenance of equipment can provide electrical workers details that are critical to safety when performing justified energized work. Knowledge of the equipment itself is critical to recognizing hazards.
7. Working space
Sometimes safety doesn’t come in the form of a product — it can simply be in the fact that a design provides adequate working space for the electrical worker to safely perform functions.
Reducing the severity of injuries
It is common knowledge that justified energized work must occur in critical power environments. However, minimizing the danger associated with electrical hazards to the point at which injuries may be minor can be designed into the system. To that end, the electrical industry is making efforts in the following ways to reduce the severity of injuries to workers should an accident occur.
1. Decreased clearing time
Placing a circuit breaker with arc-reduction maintenance switch technology — or a fuse and switch in its own enclosure next to an upstream of electrical equipment likely to be a part of justified energized work — provides reduced clearing times for arcing currents, reducing the level of incident energy exposure. The achieved incident energy reduction downstream can be significant such that minimal PPE is required.
2. GFCI shock protection
Ground-fault circuit interrupters (GFCIs) are specifically designed to protect people against electric shock from an electrical system and to monitor the imbalance of current between the ungrounded (hot) and grounded (neutral) conductor of a given circuit.
3. IEEE 1584 and arc flash calculations
New updates to the 2018 Guide for Performing Arc Flash Calculations offer significant changes that impact the way arc flash hazards in electrical systems are analyzed. More precise calculations reduce the risk to employees and contractors.
4. Arc reduction technologies
Arcing faults that occur within equipment need to be cleared as quickly as possible. Arc flash reduction technology reduces clearing times of arcing fault currents should a problem occur when working on energized electrical equipment. Arc quenching equipment can extinguish an arc flash in approximately 4 milliseconds.
A trio of documents critical to safety
The entire electrical industry looks to three key documents from NFPA that strategically work together to increase safety for electrical workers by providing guidance and recommendations. Those documents are:
- NFPA 70, which provides installation requirements outlined by the National Electrical Code (NEC).
- NFPA 70E-2021, which covers the topic of electrical safety in the workplace.
- NFPA 70B, which covers electrical equipment maintenance.
In particular, NFPA 70E includes requirements for safe work practices to protect personnel by reducing exposure to major electrical hazards, including shock, electrocution, arc flash, and arc blast. These requirements rely on the fact that an electrical system was installed in accordance with the NEC and that maintenance has been performed leveraging reference materials found in NFPA 70B.
Recent changes to 70E highlight how important it is to design safety into systems and provide more detailed guidance for electrical workers. For example, the document addresses when the estimated incident energy exposure is greater than the arc rating of commercially available arc-rated PPE. We now have guidance for the purpose of absence of voltage testing. The following examples of risk reduction methods could be used to reduce the likelihood of occurrence of an arc flash, thus reducing the severity of exposure.
- Using noncontact proximity test instrument(s) or measurement of voltage on the secondary side of a low-voltage transformer (VT) mounted in the equipment before the use of a contact test instrument, to test for the absence of voltage below 1,000 V.
- Observing visible gaps between the equipment conductors and circuit parts and the electrical source(s) of supply if the design allows.
- Increasing the working distance.
- Considering system design options to reduce the incident energy level.
In addition, the latest version of 70E recognizes the newly updated IEEE 1584, a resource the industry will continue to explore and apply to new power system analysis studies.
Never settle
The effort to protect electrical workers and electrical equipment always comes back to the three pillars of safety by design.
- Eliminate the hazard.
- Reduce the likelihood of an occurrence.
- Reduce the severity of injuries.
The goal is to establish electrically safe working conditions. For situations where justified energized work is required, designs must emphasize reducing the chances of something harmful occurring and reducing the severity of injuries should an accident occur.
When it comes to shock hazards, reducing the current flow is not an option, but there are ways to avoid inadvertent contact. This means choosing specialized equipment that provides more fingersafe solutions and options for barriers that prevent workers from coming in contact with energized parts.
When designing electrical systems and the devices that go into them, it’s critical to safeguard designs, so when systems need service or repair, electrical workers are safe in minimal PPE. Ultimately, electrical workers and our industry as a whole benefit most from a “never settle” approach to safety. Purchasing PPE at a higher calorie capability than your solution demands doesn’t spell success. The industry can do better than double-digit calorie events. Striving for solutions that drive energy into the dirt will lead to safer work environments.
