Various processes within electrical systems, such as corrosion, loosening of screws, and overload, may lead to malfunctions. A failure in an electrical panel can have serious consequences, ranging from work stoppages and equipment damage to loss of life. According to data from the Fire and Rescue Services, up to 58 percent of fires in buildings and industrial facilities are caused by electrical short circuits, which are typically not sudden events but the result of a developing process.
Causes of Overheating
A. Poor Contact
According to the preventive maintenance approach, it is customary to inspect all panel connections annually and tighten screws. Those who operate according to this method assume that most electrical panel problems result from loose connections. However, a defective contact or cable lug connection may stem from additional causes, including improper screw installation, broken screws, worn threads, use of unsuitable washers, and more. Tightening screws resolves the issue only when it originates from a loose connection. In all other cases, there is no logic in tightening screws, and the action may even crush conductors or cables.
Another significant factor contributing to faulty contacts is corrosion within the electrical panel, which may create contact problems and accelerate the deterioration of existing defects. Foreign substances, such as dirt present at connection points, may also impair contact quality. Excessive tightening can cause copper to spread sideways, creating a smaller contact area. This condition is generally stable. The temperature of the defect will change only with variations in load or with additional tightening.
A break in the neutral conductor within a three-phase circuit may cause voltage increases in some phases and result in the burning of devices connected to the network.
B. Internal Equipment Defects
A defect may develop in any component or connection point. For example, contact welding in a circuit breaker means the breaker becomes stuck and will be unable to perform its function during an emergency.
In cases of internal defects, the relationship between measured temperature and the severity of the defect is even more problematic. The thermal image obtained reflects the heat observed on the external cover of the component or on the copper conductors exiting it. Only rarely is it possible to observe the actual internal heat at the defect point. The temperature measured on the outer surface results from infrared radiation emitted by the internal heat source and depends on several variables: defect temperature, physical size, distance from the outer surface, presence of insulating elements, and wall thickness. Therefore, the external temperature does not necessarily reflect the severity of the internal issue.
For example, in a circuit breaker, the contacts are usually the largest physical component. The amount of heat and corresponding infrared radiation generated there is relatively significant, thus strongly affecting the outer casing temperature. In contrast, the flexible fuse element inside the breaker is physically small, so even if its temperature is high, the amount of heat it generates is relatively limited. Consequently, its influence on the casing temperature will be minor. A moderate temperature rise on the surface of a breaker may therefore indicate a moderate rise in contact temperature, which may not require urgent intervention, or an extremely high temperature in the flexible fuse element, which demands immediate attention.
Another defect characterized by relatively low temperature yet high severity is contact welding. When an internal defect begins to develop, it causes a temperature increase. If the temperature at the defect point exceeds a critical value, it may cause the faulty contact to weld. Electrical conductivity then improves, and heat decreases accordingly. A relatively low temperature reading at this stage may be misleading, as the defect has become highly severe since the breaker or contactor can no longer be disconnected.
C. Overload
Overload is typically caused by connecting too many consumers to a specific line. Strict adherence to professional installation standards for electrical panels nearly eliminates overload situations. Conversely, improvised modifications and adding loads beyond permitted capacity are dangerous and may cause overheating. In some cases, overload problems may indicate harmonics in the electrical voltage.
D. Environmental Influences
Exposure to harsh environmental conditions can accelerate defect progression and even cause new faults. High density, lack of ventilation, or insufficient ventilation increases the temperature of all panel components and elevates the damage potential of any defect. There are cases where overheating resulted from poor ventilation and others where it resulted from overcrowding within the panel.
Another risk factor is water infiltration into panels, which may create short circuits between contacts and lead to corrosion. Dust and dirt in the vicinity of panels also contribute to malfunctions.
A particular issue arises in electrical cabinets rated at 100 amperes or higher, where a fire detection system integrated with automatic gas suppression must be installed in accordance with Israeli Standard 1220 Part 3. Since the gas used for suppression is relatively expensive, the required gas quantity is calculated on the assumption that the panel is sealed. However, sealing the panel interferes with ventilation. Thus, in order to enable gas-based fire suppression, panel temperature increases, consequently elevating fire risk.