Electrical shocks cause injuries through direct contact. Arc flash does not. The arc flash that results from a short circuit in the air releases heat radiation, pressure waves, and molten metal in all directions, meaning workers standing in front of the panel can be injured without ever touching a live part. The mechanism of injury is briefly explained in this clip. What is rarely explained is the numbers, yet it is these numbers that determine work clothing, standing distance, and inspection schedules.
Energy, not voltage, measures the danger
The danger of arc flash is expressed as incident energy in calories per square centimeter at a specific working distance. A study in the ITS Engineering Journal states that the heat radiation from an arc flash can reach around 35,000 degrees Fahrenheit, approximately 19,400 degrees Celsius, or about four times the surface temperature of the sun. The arc flash protection boundary is calculated at an energy of 5 J/cm2, equivalent to about 1.2 calories per square centimeter. Beyond this limit, second-degree burns are no longer expected to occur.
Five categories, and one chasm at the end
The NFPA 70E classification divides incident energy into five levels: category 0 below 2 calories per square centimeter, category 1 at 2 to 4, category 2 at 4 to 8, category 3 at 8 to 25, and category 4 at 25 to 40. Above 40, no personal protective equipment is available. Points with such high energy cannot be resolved by adding layers of clothing; instead, the system itself must be changed.
Time reduces the numbers
Simulations on the 6.3 kV system at PT Semen Padang show how significantly the interruption time affects the incident energy. Initially, one bus with an interruption time of 1.07 seconds produced an incident energy of 59.49 calories per square centimeter, far exceeding category 4. After the protection coordination was reset, the number dropped to 31.68, and the arc flash protection boundary for that bus was still 26.4 meters. Only after a differential relay was installed as the main protection did the interruption time become 0.13 seconds, and the incident energy dropped to 7.23 calories per square centimeter, entering category 2. The short circuit current did not change at all. What changed was merely how long the arc was allowed to burn.
The working distance is also calculated, not guessed. For the 6.3 kV system, IEEE 1584 uses a typical distance of 91 centimeters between the arc point and the worker, and its empirical model is constructed for three-phase systems from 0.208 kV to 15 kV. Arc flash studies themselves are one of several studies commonly conducted using power system analysis software, as discussed here.
What Indonesian regulations require
Minister of Manpower Regulation Number 12 of 2015 on Electrical Safety and Health at Work has been in effect since April 16, 2015, and is still valid. Its scope covers the generation, transmission, distribution, and utilization of electricity operating above 50 volts alternating current or 120 volts direct current. Some of its requirements can be directly matched with field conditions:
- Companies with electricity generation exceeding 200 kilo Volt-Amperes must have a K3 (occupational health and safety) Electrical Expert (Article 7).
- Periodic inspections at least once a year, periodic testing at least once every five years, and the results of both must be reported to the Provincial Head of Service (Article 11).
- Electrical equipment and tools used must be certified by authorized institutions or agencies (Article 12).
- Employers or managers who do not comply with these provisions are subject to sanctions under Law Number 1 of 1970 and Law Number 13 of 2003 (Article 14).
Article 5 addresses frequently asked questions about foreign standards. The electrical standards referenced include the Indonesian National Standard, international standards, and national standards from other countries as determined by the Specialist K3 Electrical Labor Inspector. Calculations based on IEEE 1584 and NFPA 70E therefore have a basis, not merely imported practices.
One provision shifting in 2026
Minister of Manpower Regulation Number 11 of 2026 on Employment Supervision Procedures, effective July 3, 2026, revokes part of Minister of Manpower Regulation 12 of 2015, specifically Article 1 number 13 and Article 10 paragraph (1), as well as Article 10 paragraph (1) of Minister of Manpower Regulation Number 33 of 2015 that amended it. These two provisions contain the definitions of Specialist K3 Electrical Labor Inspectors and the list of parties authorized to conduct inspections and testing. The note in the new regulation states that provisions regarding specialist labor inspectors in K3 and the issuance of certificates of compliance with K3 must adjust to it. The one-year and five-year intervals remain unchanged, but the reference to who is authorized to inspect has now shifted to other regulations.
Sources
- Minister of Manpower Regulation Number 12 of 2015 on Electrical Safety and Health at Work, JDIH BPK
- Minister of Manpower Regulation Number 33 of 2015 on Amendments to Minister of Manpower Regulation Number 12 of 2015, JDIH BPK
- Minister of Manpower Regulation Number 11 of 2026 on Employment Supervision Procedures, JDIH BPK
- Abstract of Minister of Manpower Regulation Number 33 of 2015, JDIH Ministry of Manpower
- Analysis of Arc Flash on Medium Voltage Systems at PT Semen Padang, ITS Engineering Journal Vol. 5 No. 2, 2016