What is Arc Flash?
Arc flashes are one of the most prevalent hazards present in industrial, commercial, and institutional environments. At their simplest, an arc flash is a dangerous electrical explosion that occurs when an electrical fault creates a high and unexpected flow of current between two or more conductors. In addition to the hazards associated with the flames and excessive temperature, arc flashes are often accompanied by a rapid release of expanding gases that can produce a fast-moving blast wave or pressure wave. This can shatter glass, cause equipment damage, send metal projectiles flying, and, depending on the personnel and their relative location at the time of the arc flash, cause injury or even death .
The cause of an arc flash can be as straightforward as one or more of the conductors unintentionally coming into contact with each other or with a circuit path. Poor maintenance and inadequate equipment design and installation can lead to loose connections and pitting or corrosion and compromise insulation, making it more likely for conductors to touch. Environmental factors can contribute as well, for example by creating paths for moisture, dust, or metal particles. Finally, excessive loads or short circuits can create short term voltage fluctuations in the utility service, which can "trip" voltage-sensing relays and cause lots of electrical activity before the fault is cleared. Even a minor arc flash can cause significant damage to equipment, and a more severe one can result in catastrophic damage and/or physical injury.
Importance of Arc Flash Assessment
Given the obvious dangers posed by arc flash hazards, many employers have questions regarding when they are required to conduct an arc flash assessment with regard to NESC and NEC. It is unfortunate, but even with the strength of OSHA, NESC and NEC requirements and guidelines, many employers will continue to overlook the fact that personnel and equipment could be at risk of electrocution and fire causes when working in an area where arc flash hazards may exist.
The following summarizes the importance in assessing equipment with regard to these standards.
OSHA
OSHA standards are expressed as "performance based", meaning that it is the employer’s responsibility to adopt and maintain certain criteria which are then measured and audited for conformance by their designated professional(s). The NESC and NEC have specific requirements that set engineering and administrative measures for certain high-energy distribution systems. Below is a summary of some relevant OSHA standards in relation to NFPA 70E:
● OSHA 1910.335(a)(1) requires employees to use PPE suitable for the work being performed, as well as for the workplace hazard, including protection from electric shock and arc flash and arc blast.
● OSHA 1910.335(a)(1) requires arc rated PPE to be used whenever employees face a risk of electric shock or electrocution.
● OSHA 1910.335(a)(2) requires employees to become trained periodically on the safety-related work practices of electric shock and electric arc flash.
● OSHA 1910 Subpart S requires that electric circuit components and other application of electricity should be designed and used in accordance with applicable NESC and NFPA standards.
NESC
NESC outlines the requirements for an electrical supply utility to define and further protect from electrical safety hazards, specifically with regards to its high energy electrical system equipment. OSHA and NFPA 70E regulations, while voluntary for NESC members (NESC-Utility Operated Equipment), are specifically required to be observed. Any utility that is tasked with any of the following considerations is required to comply with NESC:
● Section 410: Well defined definitions for shock and electrocution
● Section 800: Clear definition of different electrical hazards, required safety measures and types of PPE and work methods required for using electrical equipment
● Section 420: Defining the parameters of minimum electrical approach distance and protective boundary
NEC
NEC outlines the regulations and standards needed for safe electrical wiring, installation, etc. in order to minimize electrical hazards to personnel and equipment. NEC is a publically adopted electrical equipment installation standard. As a result, all states and local jurisdictions are mandated to adopt "no less than" this standard.
Components of Arc Flash Assessment Requirements
In addition to the requirement for a complete, updated Electrical Safety Program, the key components of the arc flash assessment requirements are:
Arc Flash Assessment
The arc flash assessment shall be the basis for selecting the PPE to be used in the event an employee is exposed to electrical hazards while performing energized electrical work. The purpose of the arc flash assessment is to provide:
• An evaluation of the potential exposure of employees performing work on or near electrical equipment to energy levels resulting from an arc flash event;
• The classification of the degree of arc hazard associated with the operation and/or maintenance of the electrical equipment; and
• The estimation of the probability of occurrences of an arc flash event so that PPE, work practices, and training can be properly established.
Safety Protocols
The arc flash safety protocols (NFPA 70E-2015), policies, and procedures shall be used as a guide in developing the electrical safety program and safety-related work practices and procedures that protect employees from arc flash and electrical shock, electrical hazards, and hazards related to exposure to electromagnetic field (EMF).
Depending on the arc flash potential of electrical equipment, containment measures shall be implemented that may include the following:
• Engineering controls, such as the installation of physical barriers or shields.
• Personal protective equipment (PPE) with a minimum arc rating that is appropriate for the level of hazard. PPE shall be provided at no cost to employees.
• Specific work practices and job procedures, to the extent that the identified hazards are not effectively mitigated through the above measures.
It is the responsibility of management to ensure employees are qualified, trained, and provided with the necessary PPE to safely perform electrical maintenance and testing practices.
Technical Considerations
The arc flash hazard analysis shall be performed by a qualified person that has an electrical engineering background, documented experience, and is knowledgeable about electrical systems and equipment, and understands the properties of electricity and how electrical hazards can cause injury and the necessary safeguards to prevent electrical shock and arcing fault burns. The analysis shall define the operating modes of the electrical equipment and shall consider, but not be limited to:
Standards Governing Arc Flash Assessments
The arc flash assessment process is governed by a variety of national and even international industry and safety standards. As you probably already know, OSHA, the Occupational Health & Safety Administration, requires employers to provide a safe work environment for their employees, but many of these regulations are rather general in nature, allowing manufacturing, operations and engineering experts to determine the specifics. In the case of arc flash assessments, OSHA continues to defer to the National Fire Protection Association standard known as NFPA 70E for its arc flash safety requirements and guidelines.
The NFPA is long known as being the equivalent of the National Building Code when it comes to safety and hazards involving electrical equipment. NFPA standards also extend to all electrical installations under the jurisdiction of the National Electrical Code.
According to the NFPA 70E Guidelines, arc flash assessments are required every five years. Once an arc stroke study has been performed and is a matter of record, the guidelines don’t require them to be updated more frequently, though there are federal, state and local jurisdictions that differ from the NFPA guidelines on this point. However, even if the NFPA guidelines aren’t actually carried out, they are still used as best practices and are still regarded as the "cutting edge" of safety standards.
How to Perform an Arc Flash Assessment
A step-by-step process for conducting an arc flash study involves the following 4 essential steps:
Step 1: Preliminary Survey
A preliminary survey is conducted to determine if there are any, but not limited to, the following conditions: the size and layout of the area; types of utility service (overhead, underground, padmounted transformers); types of circuit breakers (air or oil circuit breakers); switchgear and other enclosures; capacity and types of transformers serving the facility; protected equipment in the distribution and utilization systems; motors and generators; transformers; solid-state equipment; industrial equipment and machinery; and lighting, fire alarms, and emergency systems. The survey should include a list of equipment and the location of that equipment.
Step 2: Data Collection
Data collection is conducted by the qualified personnel previously discussed.
Step 3: Data Analysis
The collected data is used to assess the risk of an arc flash and to develop mitigation recommendations. This is generally done using one or all of the following methods: NFPA 70E, IEEE 1584, and/or the manufacturer’s guidelines. The analysis will identify those work zones where the incident energy levels are sufficient to support the occurrence of an arc flash. It is important to note that the minimum distance a worker needs to stay away from the identified hazard zone is referred to as the arc flash boundary. This boundary is referred to as the Restricted Approach Boundary. The Restricted Approach Boundary is the distance at which a worker must wear an arc rated face shield to protect himself from an arc flash. In cases where the incident energy is low (e.g., less than one calorie per centimeter squared per second), arc rated face shields may not be required.
Step 4: Documentation
All documentation should be stored in an accessible format like a computer spreadsheet or database. It should include:
As discussed earlier, there is no such thing as an easy way to predict an arc flash. However, understanding which employee population faces the greatest risks helps in understanding what preventative measures should be taken. This proactive approach to minimize employee exposure is consistent with OSHA’s approach to protecting employees.
Necessary Tools and Equipment
The tools and equipment needed to conduct an arc flash assessment vary depending on the complexity of the analysis being conducted. At a minimum, a measurement device called a multimeter is necessary to gather voltage, current, voltage log, and amps data points. The preventative maintenance records for all of the major components of the electrical system should be reviewed during this phase of the analysis, including the circuit breakers, disconnects, transformers, and other critical components of the system. A powerful computer with the analytical software installed (typically an analytic software type called SKM or ETAP) is also critical. This software will take all of the measured data, as well as the schematic data input by the analyst, and conduct the actual arc flash analysis to determine the actual current available during a fault condition, and the arc flash category for all of the principal areas of the system. In addition , thermographic software, power quality analyzers, harmonic distortion monitors, and other similar hardware and software may be used, depending on the status and health of the system. Portable single-point testers, such as the Fluke 740 or Fluke 289, are used to measure voltage across circuit branches. For three-phase circuits, the whole circuit must be taken apart and tested separate from each other. For larger panels, point-to-point and system-wide measurements can be used through the distribution grid, with recorders placed within the entire scope of the circuit. Protective equipment will also be necessary for the analyst. Since the survey team will often be working in an energized and in service or potentially in service capacity, all personnel must use appropriate protective equipment. It is possible that tap test equipment or infrared testing will be required.
Common Issues and Solutions
When it comes to arc flash assessment compliance, there are some common challenges the regulated community faces. The following is a short list of what those challenges tend to be and some solutions that will help tremendously in overcoming those obstacles.
Challenge: Proper recordkeeping of electrical equipment nameplate information can be time-consuming and expensive.
Solution: Keep hard copies of electrical equipment documentation with the equipment when possible. If not, have this information added to a dedicated Company database (this will save you time in the long run). Review the ARC Flash audit documentation requirements under the OSHA General Industry Standards (29 CFR 1910.138(a)(6), 1910.335(a), and 1910.132-135) to ensure proper documentation is being collected.
Challenge: Getting information from subcontractors is difficult due to confidentiality issues and reluctance to provide information because of liability protection risks.
Solution: Make sure the scope of work includes providing this information. Check to see if the service providers are using information you might seek as part of their scope of work and then try to aggregate the required information into a Company database if possible. Be diligent with the vendors you choose and weight the costs associated with limiting risk of AML versus the cost of the vendor’s services or obtaining the information in another manner.
Challenge: A lack of understanding of the different methods for assessing arc flash hazards.
Solution: Understand that the hierarchy of risk control options is generally as follows: (1) hazard elimination and engineering controls, (2) administrative controls, and (3) PPE (OSHA 1910.132-135 and NFPA 70E). Part of the challenge when it comes to compliance with OSHA and NFPA requirements is the audit. The audit needs to be thorough and accurate to be effective; unfortunately, there tends to be confusion with stakeholders regarding the audit’s findings.
Real-Life Applications and Case Studies
In addition to theoretical insights into the importance of arc flash assessments for ensuring safety and compliance, real-world applications of these requirements are also essential. One case study from a large manufacturing plant illustrates the effectiveness of a systematic approach to arc flash assessment. The plant had a history of electrical incidents and a comprehensive safety program that included a focus on electrical safety training. However, their prior safety audits had not addressed arc flash hazards specifically. After conducting a full assessment of all major electrical equipment within the facility, an arc flash study was developed and documented. This study provided the data necessary to ensure that their safety program addressed arc flash protections and that all employees, from general workers to electrical maintenance staff, received adequate training.
In another example, a large hospital system engaged in regular risk assessments and workplace inspections had not conducted a formal arc flash risk assessment. A sudden arc flash incident effectively pushed them into compliance, and they subsequently hired an engineering firm to undertake a full hazard analysis of all electrical equipment. Even though the equipment did not date back to the earliest days of electricity, they discovered that many had not been adequately updated or maintained, and several were found to contain vintage electrical components that were no longer manufactured. Companies contemplating an arc flash assessment will often have the notion that they can focus on their newer machinery or just focus on areas that face electrical events (e.g., maintenance shops), but the reality is that every company can benefit from a full assessment.
One South American mining operations company performed a full arc flash risk assessment and realized that it could avoid significant risk by increasing the distance that workers were required to maintain from exposed equipment during maintenance activities. The risk assessment gave them the ability to set clear policy regarding worker safety roles and distance from equipment.
In the world of information technology, one utility company is developing an electronic version of an arc flash mitigation program for use in training and compliance documentation. Many of the elements of this electronic version are also applicable to other industries and organizations, particularly those involved in manufacturing, because of the extensive reliance of machinery within these workplaces. This company has proposed an electronic hazard identification and assessment form that consists of 10 required questions and five optional questions. Much of the language in this proposal will be familiar to readers as the language closely follows the "ASCE/IEEE/CIGRDEC 738." This company sees this program as being able to increase compliance with both arc flash and lockout/tagout policies.
These case studies show that companies can benefit from facilitating compliance with arc flash requirements by incorporating path-of-least-resistance methods that have been proven effective elsewhere. For many companies, the only reason to conduct arc flash assessments or studies is to stay compliant with the regulatory requirements. However, there are other benefits, such as improvements in safety and operations. The companies that have successfully complied with these requirements have seen benefits such as the following: In order to encourage compliance with arc flash requirements and find solutions to any problems that may be found, many professional engineering firms will offer a consultation service to discuss the results of an arc flash study. The results of successful assessments will often be made public by these firms so that other companies can be motivated to engage in compliance efforts for both safety and regulatory compliance.
Future Directions in Arc Flash Safety
As with most industries, constant evolvement in the arc flash safety realm is necessary as protocols and technologies change. Some of the discussions over the past few years at major U.S. and international electrical safety conferences and forums have focused on a couple of major themes.
One theme is considering an "inside-out" methodology for arc flash safety. Most arc flash compliance was based on electrical equipment inside the "locked room," where no one except those with arc-rated Personal Protective Equipment (PPE) could be. However, most workers are not in the "locked room" — they are outside. While the NFPA 70E standards make reference to whether someone is an inside worker or an outside worker, a complete analysis of PPE requirements based on the location of the worker was considered overkill. That seems to be changing. There is growing interest in taking communication and other systems design concepts and applying them to arc flash safety, so the inside-out approach is trending.
The second theme is a recognition that arc flash safety protocols must be global. After all, electrical safety is consistent around the world. Whether in China, Singapore, Germany or Argentina, a short circuit in a transformer can have the same impact on the electrical utility infrastructure and life of non-electrical workers. So, now that arc flash safety protocols are being introduced on a worldwide basis , there is conversation about how those protocols must be consistent with other safety programs in use. Brazilians, for example, have an in-depth practical electrical safety standard that includes a process approach to communications that can inform standards development in other countries. As collaboration like this continues between countries, consistent communications tools and guidelines will become more common.
Another theme is the application of arc flash safety principles to new environments, such as solar energy facilities, offshore wind farm systems, wireless communications towers and many other sites that combine energized electrical equipment with the electrical infrastructure. It is not only because of the presence of voltages but also the fact that electrical safety and explosion prevention in numerous cases is also critical. Indeed, some of the natural gas stations and pipeline systems in wide use throughout the United States today are a century old and still in use, requiring special attention to arc flash safety.
Yet another trend has to do with sharing arc flash safety regulations and processes in the developing world. Often, arc flash safety training and procedures must be completely re-translated without standard reference points for those who are inexperienced in the arc flash safety requirements. Still, even in areas where a consistent approach is still being developed, opportunities to share health and safety training are valuable, if not critical.