Most electrical equipment today include openings for ventilation of air. Those ventilation openings are a vital part of the design of the electrical equipment as they help in maintaining the component temperatures inside the enclosure within some design limits. When these openings are not included or are blocked, either intentionally or inadvertently, the electrical equipment can overheat. The overheating may further lead to a thermal runaway condition, which can result in a catastrophic failure and breakdown of the equipment.
Ventilated electrical equipment is described as equipment with ability to allow circulation of air in order to remove an excess of heat. The ventilated electrical equipment is enclosed, in order to prevent accidental contact by personnel. The design of ventilated electrical equipment is controlled by standards and it needs to be visually noticeable. It needs to be strictly governed by standards for electrical power equipment, given from the regulative body in the countries. For ventilation openings, the standards specify all the critical details, including size, location and configuration of the ventilation openings, which improve the overall performance of the electrical power equipment and prevent the access to energized conductors.
Many people are worried that ventilated electrical equipment exposes them to many hazards, but in fact, it does not. Recent reviews of the safety standards of ventilated electrical equipment addressed the concerns of personnel being accidentally or inadvertently exposed to hazards through the ventilation openings. Actually, the potential hazard is that the electrical power equipment is capable being accidentally touched or approached by a person than a safe distance, but this applies for electrical parts that have no protection or isolation. So, the most important thing with ventilated electrical equipment is to avoid a contact. The concept of safe-approach distance is very efficient and exists where there are possible hazards, including shock or flash hazards.
Recently, it was estimated that about 25,000 non-fatal electrical shock accidents occur every year in Australia. Also, each year over 1,500 people are reported to burn centers with minor and severe arc flash burns. Many of these accidents happen when people work on exposed energized conductors. However, the enclosed ventilated or non-ventilated electrical power equipment are effective at preventing such electric shock injuries or arc flashes. Misinterpretations about the safety of ventilated electrical power equipment appear occasionally, but the careful reviews of the standards and terminology can lead to truly understanding the construction features used in electrical power equipment enclosures.
