Protection against internal arcs in low-voltage systems.

Safety in industrial electrical installations is one of the greatest challenges for engineers, technicians, and maintenance managers. Among the most critical phenomena that can occur in low-voltage systems is the internal electric arc, an occurrence that combines high energy, extreme heat, and destructive mechanical effects.

An internal arc can cause anything from serious damage to equipment to direct risks to the lives of professionals, being responsible for numerous accidents in industrial environments around the world. Therefore, understanding its causes, effects, and especially how to mitigate it is essential to ensure operational continuity, the safety of people, and the reliability of electrical systems.

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What is an inner arc, its causes and effects?

An internal arc occurs when there is an unintentional electrical discharge inside an electrical panel, switchboard, or piece of equipment, usually as a consequence of a short circuit. This discharge creates a path of highly conductive plasma that can reach temperatures exceeding 20,000 °C—heat sufficient to melt metals, generate explosive pressure, and launch fragments at high speed.

The main causes of internal arching include:

Human errors: incorrect opening of energized compartments, improper use of tools, or failures in maintenance procedures.

Mechanical failures: loose connections, worn circuit breakers, damaged insulators, or compromised contacts.

Environmental factors: presence of conductive dust, excessive humidity, corrosion, or even animals entering the panels.

The effects of an internal arc flash are devastating. Beyond the immediate risk of severe burns and fatal injuries to nearby people, the event can completely destroy the panel, cause lengthy production interruptions, and generate millions of dollars in financial losses. It can also compromise the reliability of the installation, requiring the complete replacement of equipment.

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How to mitigate the internal arc?

While it is impossible to completely eliminate the risk of internal arcing, there are strategies and technologies that can mitigate its effects and increase the safety of operations:

1. Proper design of electrical panels

Low-voltage switchgear must be designed in accordance with international standards, such as IEC TR 61641, which defines test criteria for withstanding internal arcs. The use of tested switchgear ensures that, in the event of a fault, the effects are confined within the equipment, protecting operators.

2. Advanced protection devices

Installing protective relays with arc detection functionality and light sensors allows for the identification of an occurrence in milliseconds, quickly shutting off the power supply and minimizing damage.

3. Interlocking and compartmentalization systems

Compartmentalizing circuits and panel sections reduces arc propagation. Mechanical and electrical interlocks prevent incorrect operations that could expose the energized panel during maintenance.

4. Good maintenance and operation practices

Ongoing team training, thermographic inspections, periodic tightening of connections, and preventive cleaning are fundamental measures to reduce risks.

5. Personal protective equipment (PPE)

Even with all preventive measures, the use of appropriate PPE (flame-resistant clothing, face shields, insulating gloves) is mandatory for work in proximity to energized panels.

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Internal arcing is one of the greatest risks in low-voltage systems, but with appropriate technology, tested designs, and efficient maintenance practices, its effects can be significantly reduced.

Investing in internal arc flash protection solutions should not be seen merely as a regulatory requirement, but as a commitment to people's lives and business continuity.

At BTM, we develop electrical panels that are tested and aligned with international standards, reinforcing the importance of offering solutions that prioritize not only energy efficiency, but also the safety and reliability of our customers.