Determining Safe Working Distances
Limits of Worker Protection in Electric Arc Hazard SituationsThis is necessary to determine the dangerous thermal energy that will be generated in the event of a short circuit in the electrical grid and the safe working distance, in order to maximize the safety of workers.
Limits of Worker Protection in Electric Arc Hazard Situations
Safe working distances are defined by IEEE 1584, IEEE 1584-2018, and NFPA 70E standards, which specify the distance limits at which a worker can be protected from thermal energy damage in the event of a short circuit in an electrical system. Multiple safe distance zones are defined, such as arc flash boundary (5 cal/cm² limit), limited approach distance, and restricted approach distance; each zone has its own protocols and PPE requirements.
At AES Innovation, we help electrical system designers and employers determine safe working distances based on arc flash analysis results, ensuring maximum safety for electricians and maintenance personnel.
The limited approach distance must be maintained by untrained personnel, who must remain outside this distance, and the factory must be marked with "electrical hazard" warning signs. If untrained personnel exceed this limit, it constitutes a violation of occupational health and safety, and the employer will be held legally liable.
The limited approach distance applies in very high voltage environments (10kV and above); personnel working within this limit must have obtained a special “Arc Flash Working Authorization”.
Untrained Personnel and Restricted Areas
Limited Approach Distance
Determining Safe Working Distances
Arc Flash Boundary and Limits:
Arc Flash Boundary (5 cal/cm² Limit)
The arc flash boundary is the distance at which the incident energy is 5 cal/cm²; those working within this boundary must wear at least Category 2 PPE. Outside the boundary, the energy decreases with increasing distance; those working outside this boundary do not require a hot work permit.
Limited Approach Distance
The limited approach distance is the minimum distance that trained personnel may approach; within this limit, personnel acknowledge that they are working in high-voltage conditions. Violation of the limited approach distance may result in serious injury.
Restricted Approach Distance
The restricted approach distance is a more precise limit, and only specially trained and authorized personnel may work within this boundary. Violation of this boundary almost certainly results in electrical damage.
1.2 cal/cm² Limit (Minimum Hazard Limit)
A value of 1.2 cal/cm² is considered the minimum energy level that poses a risk of mild burns; beyond this limit, human tissue is not damaged.
Labeling and Reporting
Based on the results of the risk assessment, an NFPA 70E label is designed and affixed to the boards.
Voltage Level and Formulas
Approach Distance Calculation
Approach distance calculation varies depending on the voltage level and is done using the tables provided by NFPA 70E:
Between 50V and 600VLimited approach distance: 0.3 meters (1 ft)
Between 601V and 2.5kVLimited approach distance: 0.5 meters (1.5 ft)
Between 2.5kV and 15kVLimited approach distance: 1.2 meters (4 ft)
Between 15kV and 35kVLimited approach distance: 1.8 meters (6 ft)
35kV and above: Limited approach distance depending on voltage. increases
These distances apply to employers' operational procedures; violations of these distances may result in penalties.
WHY AES INNOVATION?
Establish safe working distances and protect your workers!
Establishing safe working distances is one of the most practical applications of electrical safety. Determine distance limits and prepare operational procedures with professional arc flash analysis!
Frequently Asked Questions
Electrical internal installation inspections are the most effective way to guarantee safety and operational continuity in your workplace. At AES Innovation, we perform electrical inspections to the highest standards in your facilities with our TÜRKAK accredited laboratory and expert engineering team.