Challenges of high voltage direct current contactors in high-temperature environments: Risks of insulation aging and increased contact resistance

1. High temperature accelerates aging of insulating materials
Insulating materials are an important component of high voltage direct current contactors. Their function is to isolate different potential points, prevent current leakage, and ensure the safe operation of equipment. However, under continuous high temperature conditions, the insulating material will undergo thermal degradation and molecular chain breakage, resulting in a decrease in material performance, such as reduced dielectric strength and weakened mechanical strength. This aging process not only shortens the service life of the insulating material, but also increases the risk of electrical breakdown, laying hidden dangers for electrical failures.

2. Changes in the surface of the contact terminal: oxide film and hot melt welding
The high temperature environment also has an adverse effect on the contact terminals of the high-voltage DC contactor. The surface of the metal terminal is easy to react with oxygen in the air at high temperature to form a dense oxide film. Although this oxide film protects the internal metal from further oxidation to a certain extent, it also increases the contact resistance and affects the smooth passage of current. What is more serious is that when the current passes through the contact point, due to the heat generated by the Joule effect, hot welding may occur between the contact terminals, that is, the contact surface is partially melted and bonded together, which not only deteriorates the contact state, but also makes the contactor face greater mechanical stress when disconnected, increasing the failure rate.

3. Impact of increased contact resistance
The increase in contact resistance is a direct consequence of the above phenomenon, which has a profound impact on the working state of the high-voltage DC contactor. First, at the moment of connection and disconnection, the larger contact resistance will cause the generation of arcs. The high temperature of the arc not only further accelerates the wear and oxidation of the contact terminals, but also may ablate the contact surface, forming pits, and further deteriorating the contact conditions. Secondly, the strong heating effect accompanied by arc discharge increases the internal temperature of the contactor, accelerates the aging process of the insulating material, and forms a vicious circle. In addition, the increase in contact resistance will also lead to increased energy consumption and reduced efficiency, which is undoubtedly unacceptable for modern power systems that pursue high efficiency and energy saving.

4. Safety hazards and countermeasures
Electrical failures caused by increased contact resistance, including but not limited to contactor failure, circuit short circuit and even electrical fire, pose a huge threat to personnel safety, equipment protection and stable operation of the system. Therefore, it is crucial to take effective measures to deal with these challenges in high temperature environments. On the one hand, the selection of insulating materials and contact terminal materials with excellent high temperature resistance and anti-aging performance is the basis; on the other hand, optimizing the contact design, such as using silver or gold plating surface treatment technology to reduce oxidation, and designing a reasonable heat dissipation structure to improve the heat dissipation capacity of the contactor, is also the key. In addition, regular inspection and maintenance, timely detection and handling of potential problems are also an indispensable part of ensuring the long-term stable operation of high voltage direct current contactors.