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Arc Flash studies – An arc flash is a phenomenon where a flash-over of electric current leaves its intended path and travels through the air from one conductor to another or the ground. The results are often violent and when a human is close to the arc flash, serious injury and even death can occur. Arc flash can be caused by many things including Dust, Dropping tools, Accidental touching, Condensation, Material failure, Corrosion, and Faulty Installation.
The factors to determine the severity of an arc flash injury are Proximity of the worker to the hazard, Temperature, fault current, and Time for the circuit to break. The main objective of an arc flash study is to identify and analyze high-risk arc flash areas in your electrical power system with greater flexibility by simulating and evaluating various mitigation methods in arc flash study.
The National Fire Protection Association (NFPA) has developed specific approach boundaries designed to protect employees while working on or near energized equipment. These boundaries are
• Flash Protection Boundary (outer boundary)
• Limited Approach
• Restricted Approach
• Prohibited Approach (inner boundary)
The software used for the arc flash study is ETAP and DigSilent Powerfactory.
WHY ARC FLASH STUDIES?
• To determine maximum incident energy at MV and LV switchgear
• To establish the Arc flash boundary limit based on the arc fault current and fault clearing time.
• To specify the hazard/risk category
• To recommend suitable PPE for the safety of workers.
• To generate suitable danger and warning labels.
HOW DO ARC FLASH STUDIES? (METHODOLOGY)
• Collection of inputs (SLD, equipment parameters – Voltage kV rating, Power MVA rating, Impedance, System fault level, X/R ratio, protection settings).
• Check the electrode configuration of the panel based on IEEE 1584 such as VCB, VCBB, HCB, VOA, HOA
• Modeling in study software.
• Determining the bolted fault current and performing short circuit studies at each switch gear for the worst scenario.
• Determine the arc fault current.
• Determine the duration of arc fault current based on protection settings/relay coordination.
• Determine the incident energy for each switchgear at the working distance and suitable PPE.
• Generating danger and warning labels.
• Submission of a detailed report including labels.
OUTCOMES OF ARC FLASH STUDIES
• A detailed report explaining the input data, system configuration, observations, and recommendations
• Fault currents at various buses and branches in the system.
• Maximum incident energy at MV and LV switchgear.
• Arc flash boundary limit.
• Recommendation on suitable PPE
• Danger and warning labels with necessary safety information
REFERENCE STANDARDS
• NFPA70E, “Standard for electrical safety in the workplace”,
• IEEE Std 1584, “IEEE Guide for Performing Arc flash hazard calculation”,
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