Arc Flash Studies
What is Arc Flash?
An arc flash can occur when there is a rapid release of energy due to a ground fault, or phase to phase fault. This is not merely a short circuit event. This is a short circuit that results in so much energy release that the equipment is vaporized. Even the air around the equipment becomes a conductor when the vaporized metal of the equipment forms a plasma in the blast itself. Temperatures in the center of an arc flash can reach 35,000 degrees Fahrenheit. This sudden and violent release of energy destroys anything and everything in its vicinity and can, and often does, result in injury and or death.
What can be done to eliminate or reduce injury from the risk of Arc Flash? The only way to eliminate the risk of Arc Flash is to turn off power to equipment before any work is done on electrical equipment. Proper procedures for Lock out Tag out (LOTO) should be performed. But performing proper LOTO places the electrician at risk because equipment must be tested to verify that power has actually been turned off. This testing places the electrician in harms way. To mitigate this exposure an Energized Electrical work permit must be completed detailing the risks and the procedures that will be used to mitigate that risk. Proper PPE must be evaluated and used to protect the worker from arc flash exposure. The problem with selecting the proper PPE before an arc flash study has been performed is that the energy level present at the equipment is unknown. In cases like this the safest course of action would be to turn off all sources of electrical energy. If that is not an option than the highest level of PPE must be worn when performing any testing or work.
Why is it important to know what your exposure level is?
Knowing what level of incident energy exists at a piece of equipment will allow the proper PPE to be known before any work is performed. The label details important information such as, Nominal Voltage, Arc Flash boundary, The Cal/cm^2 of the PPE needed to perform work on or near the equipment, as well as the shock hazards present.
Steps involved in an arc flash study
- The first step in any arc flash study is the collection of data. This includes equipment ratings, breaker ratings, wire sizes, conductor lengths, etc… and, depending on the size of the facility, may require a significant amount of time to gather. The utility should also be contacted to find out the maximum short circuit current available from the utility transformer.
- With the data collected, a one-line diagram is then created of the facility electrical system.
- Once all this data is known and the one line has been created then the process of finding out how much arching short circuit current is present at each panel bus and at each breaker, fuse or device in the electrical system.
- The process then continues with a coordination study to determine what adjustments can be made with breaker settings and fuse selection to reduce the incident energy at each location. This study also helps to coordinate electrical equipment to trip in an orderly fashion in the event of a short circuit. In other words, you don’t want the main breaker for a facility tripping when something that is far down the line shorts to ground. You would expect the nearest upstream disconnecting device to trip first. That is the goal of a coordination study. To set the equipment up in such way that at any point in the electrical system the nearest upstream device trips in the event of a short circuit.
- Finally, now that all this work has been done, proper labeling of equipment can take place to ensure that personnel are properly informed to the hazards associated with working on each piece of electrical equipment in the facility and what level of PPE must be worn to protect them from an arc flash.
How can we help?
If you would like to begin the process of performing an arc flash study at your plant give us a call to ask about our services and to schedule the process of data collection.
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