Switchgear Power Systems and Arc Flashes: Frequently Asked Questions

An arc flash (a.k.a. arc fault) occurs when electrical current flows through the air between one phase bus bar and another, or between a phase bus bar and a neutral or ground. The severity of the arc depends on the voltage of the switchgear that releases it, and whether the gear is open or closed at the time of release. Arc flashes are a serious concern in any commercial or industrial power system. Along with causing fires and explosions that ruin electrical systems, these flashes also cause injury and loss of life. If you are concerned about arc flashes in switchgear power systems, and you wish to know more about their causes, effects, and how to prevent them, the answers below can help.

What are the main causes of arc flashes in industrial switchgear?

The main causes of arc flashes in industrial switchgear are: the application of tools to energize switchgear, deteriorated insulation on phase bus bars, and loose electrical connections that overheat. These things can be prevented by proper safety measures and regular maintenance.

What is the lowest voltage at which arc flashes occur?

120 volts is generally considered the lowest voltage at which arc flashes occur. The voltage of industrial switchgear can exceed this voltage by hundreds of thousands of times.

Under what conditions should technicians work on energized switchgear?

Although de-energizing switchgear power systems before maintenance is always preferable, the Occupational Safety and Health Association (OSHA) lists two conditions in which technicians can work on equipment energized above 50 volts: when de-energizing the equipment would result in a dangerous condition, and when the design of the equipment - or the work being performed on it - requires it to be energized.

How do you choose the right equipment to protect against arc flashes?
Personal protective equipment (PPE) is chosen based on the incident energy that is present at any point where technicians are required to work on energized switchgear. To calculate incident energy, refer to the guidelines in National Fire Protection Association (NFPA) standard 70E.

What is a flash protection boundary and how is it determined?

An arc flash protection boundary is the distance from an arc fault at which a person who is not wearing PPE has a 50% chance of becoming inflicted with second degree burns. NFPA 70E lists four methods for determining a boundary. Of these methods, Institute of Electrical and Electronics Engineers (IEEE) standard 1584 is the most frequently used.

What is arc flash analysis and when should it be performed?

In arc flash analysis, a technician determines the amount of current that could occur at any point in a building's electrical system. A facility should undergo arc flash analysis when there is a change to its electrical system, or when it is required to be NFPA 70E compliant.

Prime Power Performs Arc Flash Analysis

At Prime Power, we know the danger of arc flashes, and the financial devastation that it can cause a company. Let us examine the situation and suggest corrections before something tragic happens.

For over twenty-five years, Prime Power has performed arc flash analysis and training, load banking, system modernization and retrofitting, infrared scanning, and breaker testing in Georgia. If your medium or high voltage power system needs attention, call us today.