Causes of temperature rise and temperature measurement of high voltage switch cabinet

As an indispensable and important equipment in the power system, the operating status of high-voltage switchgear is directly related to the safety and stability of the power grid. However, in actual operation, high-voltage switchgear often faces the problem of excessive temperature rise, which not only affects the performance of the equipment, but may also cause failures or even safety accidents. Therefore, in-depth analysis of the causes of temperature rise in high-voltage switchgear and taking effective temperature measurement methods for monitoring are of great significance to ensure the normal operation of the power system.

1. Excessive load current

During the operation of high-voltage switchgear, if the load current exceeds its design rated value, a large amount of heat will be generated inside the equipment, thereby causing temperature rise. Especially when the load current exceeds 75% of the rated current of the switch, the temperature rise phenomenon is particularly obvious, far exceeding the standard requirements.

2. Differences in expansion effects of different metals

The interior of the high-voltage switchgear contains a variety of metal materials, such as steel bolts, copper and aluminum busbars, etc. These materials have different expansion coefficients when the temperature changes. When the equipment is running, changes in load current and temperature will cause differences in expansion and contraction between different metals, thereby causing creep. Creep can cause the contact surface to be misaligned, forming tiny gaps and oxidation, increasing contact resistance, forming a vicious cycle, and further exacerbating temperature rise.

3. Improper tightening bolt pressure at the connection part

Some installers or maintenance personnel mistakenly believe that the tighter the connection bolts are, the better when connecting conductors. However, for materials with a small elastic coefficient such as aluminum busbars, when the nut pressure reaches the critical value, continuing to increase the pressure will cause the contact surface to deform and bulge, which will reduce the contact area, increase the contact resistance, affect the contact effect of the conductor, and then cause temperature rise.

4. The conductivity of the conductor material does not meet the requirements

The purity of the conductor material directly affects its conductivity. If the purity of the conductor raw material is not enough, the conductivity will not meet the requirements, resulting in more heat generated during the current transmission process, causing temperature rise.

5. Other factors

In addition to the above main reasons, the temperature rise of the high-voltage switchgear may also be affected by other factors, such as improper installation and maintenance process, inadequate busbar contact surface treatment, equipment aging, unreasonable wiring and connection, etc. These factors may lead to increased contact resistance and thus temperature rise.

Temperature measurement method of high-voltage switch cabinet

In order to effectively monitor the temperature rise of high-voltage switch cabinets, timely discover and solve problems, it is necessary to adopt a scientific and reasonable temperature measurement method. At present, the commonly used temperature measurement methods mainly include the following:

1. Infrared thermal imaging method

Infrared thermal imaging method is a non-contact temperature measurement method. The infrared radiation of the target surface is captured by an infrared thermal imager and converted into a temperature distribution image. This method is suitable for a wide range of temperature detection and can monitor temperature changes in multiple locations in real time. However, due to the airtightness of the switch cabinet, the infrared imager cannot directly measure the temperature of the internal equipment through the cabinet door, so it is subject to certain limitations in practical applications.

2. Contact wireless temperature sensor method

The contact wireless temperature sensor method is a common and reliable high-voltage switch cabinet temperature measurement method. By installing the contact sensor inside the switch cabinet or at a key position, it directly contacts the surface of the object to be measured and obtains the temperature data of the object surface in real time. Common contact sensors include thermocouples, thermistors, etc. This method has the advantages of high accuracy and fast response speed, and is suitable for accurate monitoring of specific locations or specific components.

3. Fiber Bragg Grating Sensor Method

Fiber Bragg Grating Sensor Method is a temperature measurement method based on fiber optic sensing technology. It uses the grating structure in the optical fiber to measure and monitor the temperature. By placing fiber Bragg Grating sensors inside the high-voltage switch cabinet, the temperature information at different locations can be obtained in real time. This method has the advantages of high precision and strong anti-electromagnetic interference ability, and is suitable for continuous monitoring of multi-point temperature.

4. Infrared Temperature Measurement Method

Infrared temperature measurement method is a handheld temperature measurement tool suitable for fast, non-contact high-voltage switch cabinet temperature detection. By aiming at the target surface, the surface temperature value of the location can be quickly obtained using infrared temperature measurement. This method is simple to operate and has a fast measurement speed, but it is limited by the measurement distance and angle and may not accurately reflect the actual temperature inside the equipment.