Analysis of Thermal Defects of GW5 Type Isolating Switch and Elimination Countermeasures
The GW5 series isolating switch has the advantages of simple structure, reliable performance, complete specifications and varieties, flexible installation method, wide application range, strong versatility, convenient operation, maintenance and repair. It has been widely used in power systems and plays a very important position in the power grid. However, while experiencing the many advantages of the GW5 series isolating switch over the years, we have also gradually realized that the heating problem of the electrical circuit has seriously affected the safe, stable and economic operation of the power grid, and must be paid great attention to, lightning arrester manufacturers.
1 Early diagnosis of overheating defects of GW5 type isolating switch
It is very important to fully understand and master factors such as the actual location of thermal defects in the isolating switch, the severity of heating in each part, and the development and change trends of thermal defects. Through investigation and statistics, it can be learned that the thermal defects of the GW5 isolating switch occur in the contact contact, terminal base, left contact and other parts. These overheating defects are not obvious in the early stage, but under the harsh conditions of high temperature and large load, they will quickly develop into critical defects that endanger the safe operation of the power grid. Therefore, early diagnosis is particularly important. Operators can conduct early diagnosis by observing rain, snow, frost and dew in various conductive parts during rainy and snowy weather and morning inspections. They can also test based on the color change of the color-changing paint or use temperature test wax sheets. The most reliable method is to use far-infrared temperature measuring instruments for quantitative testing.
Based on past experience, it has been found that the heating of some parts is indeed caused by its own defects, while the overheating of some parts is caused by heat conduction from adjacent parts. For example, if the soft connection inside the terminal block is overheated, the terminal block will heat up through heat conduction and convection. If the temperatures of the two are not compared and analyzed, the specific location of the heat cannot be accurately determined. This phenomenon also often occurs at the left and right contacts. Therefore, when using an infrared point thermometer to measure temperature, the instrument function should be set to the real-time temperature position, and the object to be measured should be moved slowly to find the highest temperature point, and then analysis, comparison and diagnosis can be performed to find out the real heating location. To make early diagnosis of thermal defects, in addition to using direct judgment method. Comparative analysis of infrared temperature measurement data should also be carried out. Comparative analysis should be carried out between different parts and different phases of the same equipment, between the same part and the same phase of different equipment, and between different time periods of the same part. Then the relative temperature difference judgment method recommended in the "Guidelines for the Application of Infrared Diagnostic Technology for Live Equipment" is used to accurately characterize and classify various types of thermal defects and cold shrink cable terminals.
2 Analysis of the causes of overheating defects of GW5 type isolating switch
2.1 The contact area of the left and right contacts of the GW5 type isolating switch and the left contact are overheated
The contact point of the high-voltage isolating switch contact is a part where overheating occurs more frequently. The heating of the left contact of the isolating switch is generally not noticed by people, because the left contact is close to the joint contact, and its heating phenomenon is easily covered by the heating of the joint contact. During on-site measurements, it is often found that the temperature of the left contact is significantly higher than the contact point of the contact. The main reasons for heating at these two places are: insufficient closing or excessive closing, resulting in insufficient contact pressure on the contact surface, resulting in heating; overheating or corrosion, etc., causes the elasticity of the left contact spring to decrease, resulting in insufficient contact pressure between the left contact finger and the contact finger base, and the right contact of the isolating switch, resulting in heating; left and right contacts are burned and the surface is uneven, resulting in a reduced effective contact surface, leading to heating.
2.2 The isolating switch terminal block is overheated
Overheating of the isolating switch terminal block is a relatively complex type of overheating, and sufficient attention should be paid to the concealment and severity of its heating. The heating of the terminal block is caused by the following factors:
(1) Due to the large temperature difference between day and night, water vapor in the air condenses or due to the infiltration of moisture on rainy and snowy days, electrochemical corrosion occurs at the connections between the aluminum conductive rods, terminal clamps and copper conductive tapes of the old products, resulting in increased contact resistance and heat generation. Although some new products are changed to copper conductive rods and terminal clamps, similar problems still exist.
(2) The conductive tape of the old product is fastened by screwing 4 M6 screws into the aluminum conductive rod. Because the strength of aluminum is not high, you do not dare to use too much force when tightening or use too much force to cause the internal thread to slip, resulting in insufficient contact pressure and causing overheating.
(3) The conductive belt is installed backwards, causing its rotation direction to be opposite to that of the isolating switch operation, or other parts generate heat, causing the copper conductive belt to lose elasticity due to overheating, or the conductive belt loses its elasticity due to long-term corrosion by corrosive gases, thus causing the copper conductive belt to break during long-term operation, resulting in a decrease in actual flow capacity and causing overheating.
3. Countermeasures to eliminate overheating defects of isolating switches
3.1 Carry out early diagnosis of overheating defects
Temperature test wax sheets or color-changing paint should be affixed to the terminal blocks, contacts and other parts of the isolating switch so that operators can detect overheating defects in time. It is best to carry out infrared temperature measurement on the isolating switch regularly or irregularly to more accurately grasp the real-time temperature, temperature rise and other operating conditions of the equipment.
3.2 Check the initial state
The isolating switch should be disassembled and inspected before being put into operation. It is strictly forbidden to use defective and inferior wire clamps, bolts and other parts. Use crimp-type equipment clamps to replace bolt-type equipment clamps. Copper-copper and copper-aluminum connections use tin enameling technology. The contact surfaces of the joints should be cleaned and conductive grease should be applied in time. Bolts should be used correctly and tightened with moderate strength.
3.3 Arrange maintenance construction scientifically and rationally
For bus-side isolating switches with high overheating frequency, it is necessary to ensure that the maintenance is in place and the quality of the maintenance is ensured. For the terminal block, focus on checking the connection at both ends of the conductive tape, ensuring that both ends are clean, flat, coated with conductive grease, and tightly crimped; for the contact area, ensure the smoothness of the contacts, apply neutral Vaseline, and check the burning of the contacts. If necessary, replace the contact and contact finger if necessary. The contact finger seat of the left contact should be polished clean, and the spring that is overheated or rusted should be replaced. It is necessary to ensure that the three-phase opening and closing are synchronized, the insertion depth of the right contact meets the requirements, and the pressure of the contact fingers on both sides is uniform. In order to check the quality of maintenance, the circuit contact resistance should also be measured to ensure that each contact surface is in good contact.
Yichang Hengyuan Technology Co., Ltd. specializes in the production of European-style cable joints, plug-and-pull heads, cable branch boxes, American-style elbow joints, high-voltage vacuum circuit breakers, high-voltage load switches, arresters, zinc oxide arresters, tank arresters, over-voltage protectors, counters, monitors, heat-shrinkable cable accessories, Manufacturer of cold shrink cable accessories, T-heads, wall bushings, European cable accessories, American cable joints, transformer neutral point protection devices, fuses, isolating switches, PT cable heads, elbow cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products
