Electrical equipment heating is one of the main causes of accidents, and infrared diagnostic technology is an emerging discipline. It plays a significant role in the monitoring of equipment heating, providing effective prevention and monitoring. This article focuses on the causes of heating in electrical equipment and the principles and applications of infrared diagnostic technology.

1. Sources of Heating in Electrical Equipment

1.1 Sources of Heating in Electrical Equipment

When electrical equipment operates, the effects of current and voltage generate three types of thermal faults: resistive heating, dielectric heating, and iron loss heating.

1.2 Thermal Faults in Electrical Equipment

Thermal faults in electrical equipment can be divided into external faults and internal faults. Poor contact is an external fault of electrical equipment; various exposed electrical terminals often cause overheating faults due to poor contact when exposed to the atmosphere for extended periods.

1.3 Internal Faults of Electrical Equipment

This refers to faults caused by insulation failures, oil insulation, and internal electrical circuit faults within the equipment casing, as well as the degradation of insulating materials. Based on the internal structure and operating conditions of various electrical equipment, and according to heat transfer theory, we can analyze the conduction and convection caused by metal conductive circuits, insulating oil, and gases. By examining the temperature distribution thermal images displayed externally from the equipment, we can diagnose various internal faults. Most electrical equipment heating faults manifest as heating at connection points. Connection points refer to the electrical connections between devices and between them and busbars or cables. Overheating at connection points has long been an issue in power systems, but with the increase in equipment load and the rising demands for reliable power supply from users, it has become an increasingly prominent issue in equipment defect management, warranting our attention and thorough investigation into the causes of its occurrence and development to resolve it comprehensively.

2. Preventive Measures for Heating at Connection Points

2.1 Quality of Connectors

For busbars and equipment clamps in substations, high-quality products should be selected according to requirements, and the current-carrying capacity and thermal stability should meet design specifications. Especially for equipment clamps, advanced copper-aluminum diffusion welding technology should be actively adopted for copper-aluminum transition products, and inferior products must be strictly prohibited from entering the grid for operation.

2.2 Anti-Oxidation

The contact surfaces of equipment joints should undergo oxidation treatment, and priority should be given to using electrical composite grease (i.e., conductive paste) to replace traditional petroleum jelly.

2.3 Treatment of Contact Surfaces

The contact surfaces of joints can be smoothed with a file to remove severe unevenness and burrs, ensuring the contact surfaces are flat and smooth. However, attention should be paid to the reduction in cross-sectional area after processing: the reduction for copper should not exceed 3% of the original cross-section, and for aluminum, it should not exceed 5%.

2.4 Control of Tightening Pressure

Some maintenance personnel mistakenly believe that the tighter the connection bolts are, the better. This is incorrect. Since aluminum busbars have a small elastic modulus, when the pressure of the nut reaches a certain critical level, if the material strength is poor, continuing to apply excessive pressure may cause partial deformation and bulging at the contact, thereby reducing the contact area and increasing contact resistance. Therefore, when tightening bolts, they should not be overtightened; it is sufficient to compress the spring washer. If conditions permit, a torque wrench should be used to prevent excessive pressure.

2.5 Process Procedures

Establish technical specifications for the installation of connection points and develop different process regulations based on the various types of overheating at connection points. Installation should strictly adhere to these regulations.

2.6 Detection Measures

For operating equipment, personnel on duty should regularly inspect the heating condition of connection points. Some overheating connection points can be identified through observation; for example, overheated connection points during operation will lose their metallic luster, and the paint color near the connection points on the conductor will darken.

3. Application of Infrared Detection Technology

Currently, one of the most advanced methods for detecting heating is infrared detection. Infrared detection technology is a high-tech online monitoring method (without power interruption), integrating optical imaging technology, computer technology, and image processing technology. It receives the infrared radiation emitted by objects and displays their thermal images on a fluorescent screen, allowing for accurate assessment of the temperature distribution on the object’s surface, with advantages such as accuracy, real-time monitoring, and speed.

Infrared diagnostic technology provides reliable predictions for early faults and insulation performance in electrical equipment. It elevates traditional electrical equipment preventive testing (which was introduced from the Soviet Union in the 1950s) to predictive maintenance, which is also the direction of modern power enterprise development. As modern science and technology continue to develop and improve, the use of infrared state detection and diagnostic technology features long-range, non-contact, non-sampling, and non-intrusive capabilities, while also being accurate, fast, and intuitive. It enables real-time online monitoring and diagnosis of most electrical equipment faults. This technology has gained significant attention in the electrical industry both domestically and internationally and has developed rapidly. The application of infrared detection technology is crucial for enhancing the reliability and effectiveness of electrical equipment, improving operational economic efficiency, and reducing maintenance costs. It is currently an excellent method in the field of predictive maintenance.

The method of using infrared thermal imaging technology to detect online electrical equipment is known as infrared temperature recording. Infrared temperature recording is a new technology used in industry for non-destructive testing, assessing equipment performance, and monitoring operational status. Compared to traditional temperature measurement methods (such as thermocouples or wax pieces with different melting points rotating on the surface or inside the measured object), thermal imaging cameras can detect the temperature of hotspots in real time, quantitatively, and online from a certain distance. Scanning can also produce thermal images showing the temperature gradient of the equipment during operation, with high sensitivity that is unaffected by electromagnetic interference. It is convenient for field use. It can detect heating faults in electrical equipment within a wide range of 20 to 2000 degrees Celsius, with a high resolution of 0.05, revealing issues such as heating at wire connections and live clamps, as well as localized overheating within electrical equipment. Therefore, the development and research of infrared diagnostic technology are essential measures for further preventing and identifying heating faults in electrical equipment.