Conducting an arc flash study on your electrical system is a major step towards compliance with OSHA requirements for providing safe work environments for your employees, and this is one of the biggest motivations I hear from customers who decide to hire us. Other reasons include corporate policy, insurance requirements, certifications, etc. My hope is that as time goes on, the main reason is to create a safe electrical environment. After all, this is the motivation behind NFPA 70E and OSHA.
Electrical safety is the driving force behind all of this and an effective arc flash study accomplishes this by providing multiple benefits beyond just compliance or corporate policy.
An arc flash study is a labor intensive process that includes multiple steps. Each of these steps build upon one another to create a clear picture of your electrical distribution system, warts and all. In addition, each step provides you with valuable benefits.
Step 1: Data Collection
The first section of an arc flash report contains a goldmine of information for plant engineers and maintenance personnel. In spreadsheet form you receive all of the information you will ever need about each electrical device in your facility.
Breakers: Manufacuturer –Type – Frame/Sensor Rating – Trip Settings – Voltage-Amps
Transformers: Type – KVA -Impedance – Primary Voltage – Secondary Voltage – Winding Design
Fuses: Manufacturer – Type – Amp Rating – Switch Rating
Cables: Size – Insulation – Length – Number per phase – Netural/Ground Info – Load Type
In most cases maintenance teams have never had the time or resources to catalog this information.
Step 2: Arc Flash Drawings
Once the data is collected an arc flash drawing is created. This drawing is a map of the electrical system from main utility transformer all the way down to branch panel boards and mechanical disconnects. Some maintenance personnel are as excited as kids on Christmas morning when I show them these drawings. For many facilities the current drawings they have are out of date or a hodge-podge of documents created during various expansions and additions. Finally, they now have one concise, detailed map of the entire electrical distribution system. And just as important, they have a simple plan in place to ensure that future changes can easily be updated and that they always have an accurate drawing of their system.
Step 3: Arc Flash Calculations
This is where the rubber meets the road in regards to the data collection and drawings. All the labor intensive work so far leads to this point where we calculate the hazard at each electrical device. This is important because this is where we find out two key points of information: the incident energy and the PPE level required to work on the device energized. This is important for two reasons:
- It provides us with minimum requirements for protection so we can work safely.
- Because we know the precise hazard, we don’t have to go through the inconvenience of over-protecting. Over-protection can be cumbersome, hot and tedious. Without all of the data collection from earlier we wouldn’t be able to do this. We would constantly be overestimating and in some cases underestimating the risk involved.
Step 4: Coordination & Mitigation
This steps provides benefits to safety and plant operation. Coordination identifies circuits in your electrical distribution system in which the over-current protective devices (breakers and fuses) aren’t opening in the proper sequence. If you were to have an incident or fault in the electrical system, it would be ideal if the breaker that trips is the closest breaker to the fault. For safety reasons, it clears the fault more quickly. For operational reasons, it shuts off power to only the panel where the fault occurred. In a mis-coordinated system, the breaker that trips is often all the way back at the main switchboard creating a more hazardous situation and likely shutting down a larger portion of your operations.
Mitigation is different than coordination. During the mitigation analysis we identify areas where we might be able to reduce the hazard. As an example, let’s say you have a control panel that is identified as a category IV hazard. A category IV is the highest level of hazard and requires the most PPE to work on energized. Often, we can mitigate this hazard to a Level I or even a Level 0. This not only makes your electrical system safer, but it allows you to work on the equipment with a lower level of PPE.
Many times coordination and mitigation issues can be corrected by simply changing an upstream breaker setting. Other times it requires the expense of adding new equipment. Either way, it is designed to make your electrical system safer and more efficient.
Step 5: Installing Labels
The next step is label installation. An arc flash warning label such as the one shown below is placed on every electrical device. This label identifies the level of hazard for that specific piece of equipment along with shock and arc flash boundaries. It is invaluable information during the process of deciding whether or not to work energized and if working energized, what precautions and PPE should be considered.
These labels allow you to make decisions based on real information and not just guesswork.
Sample arc flash label with incident energy, PPE requirements and hazard boundaries
Step 6: Training
All arc flash studies should end with a comprehensive training session. The training session should not only include arc flash topics, but should also address NFPA 70E. The goal of each training session is not just to raise awareness about electrical safety, but also the incentive to make electrical safety practices habitual. Awareness is great, but forming safety habits that become automatic over time is the real goal.
Arc Flash Studies are not only important in order to be compliant or fulfill a corporate policy. They are designed to create a safer electrical environment for you and your workers. Each step in the process provides its own unique benefits that contribute to this goal along with the added benefits of valuable information and resources you can use in your day to day work.