Analysis and Elimination Countermeasures of Thermal Defects of GW5 Type Isolating Switch

GW5 series isolation switch has the advantages of simple structure, reliable performance, complete specifications and varieties, flexible installation methods, wide application range, strong versatility, convenient operation, maintenance and maintenance. It has been widely used in power systems and has a very important position in the power grid. However, while experiencing the many advantages of the GW5 series isolating switch for many years, I have gradually realized that the heating problem of the electrical circuit has seriously affected the safe, stable and economic operation of the power grid. We must attach great importance to lightning arrester manufacturers.

1 Early diagnosis of overheating defect of GW5 isolating switch

It is very important to fully understand and grasp factors such as the actual location of the thermal defect of the isolation switch, the severity of heat at each location, and the development trend of the thermal defect. Through investigation and statistics, it can be understood that the thermal defects of the GW5 isolation switch occur in the contact contact, terminal block, left contact and other parts. These overheating defects are not obvious in the early stage, but under the harsh conditions of high temperature and heavy 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 make early diagnosis through rain and snow weather and morning inspections to observe the rain, snow, frost and other conditions of the conductive parts. They can also test according to the color change of the color-changing paint or use the temperature test wax chip. The most reliable method is Use far-infrared temperature measuring instrument for quantitative test.

According to past experience, it is found that some parts of heating are indeed caused by their own defects, while some parts of overheating are caused by heat conduction in adjacent parts. For example, if the soft connection inside the terminal block is overheated, the terminal block can generate heat through heat conduction and convection. If the temperature of the two is not compared and analyzed, the specific part of the heat generation cannot be accurately judged. This phenomenon often occurs at the left and right contacts. Therefore, when using an infrared spot thermometer to measure temperature, the instrument function should be set at the instant temperature position, and the measured object should be moved slowly to find the highest temperature point. Then analyze and compare the diagnosis to find out the real fever site. To do an early diagnosis of thermal defects, in addition to using the direct judgment method. Infrared temperature measurement data should also be compared and analyzed. Different parts of the same equipment, between different phases, the same part of different equipment, between the same phase, and between the same part and different time periods, should be compared and analyzed, and then use " The relative temperature difference judgment method recommended by the "Guidelines for the Application of Infrared Diagnosis Technology for Live Equipment" is used to accurately characterize and classify various thermal defects, and cold shrink cable terminals.

2 Cause analysis of overheating defect of GW5 isolating switch

2.1 Overheating of the left and right contacts of the GW5 isolation switch and the left contact

The contact part of the high-voltage isolating switch contact is the part where overheating occurs frequently, and the heat of the left contact of the isolating switch is generally not noticed, because the left contact is close to the joint contact, and its heating phenomenon is easily covered by the heat of the joint contact . In the field measurement, it is often found that the temperature of the left contact is significantly higher than that of the contact contact. The main reasons for the heating of these two areas are: insufficient closing or excessive closing, resulting in insufficient contact pressure on the contact surface, resulting in heating; due to overheating or corrosion The elasticity of the left contact spring is reduced due to other reasons, resulting in insufficient contact pressure between the left contact finger and the contact finger seat, and the right contact of the isolation switch, resulting in heating; the left and right contacts are burned and the surface is uneven, which reduces the effective contact surface. Causes heat, etc.

2.2 Overheating of the isolating switch terminal block

The overheating of the isolating switch terminal block is a kind of more complicated overheating. The concealment and seriousness of the heat generation should be paid enough attention. There are several factors for the heating of the terminal block:

(1) Due to the large temperature difference between day and night, which causes the condensation of water vapor in the air or the infiltration of water in rain and snow, electrochemical corrosion occurs at the connection between the aluminum conductive rod, terminal clamp and the copper conductive tape of the old product, resulting in an increase in contact resistance. Fever. Although some new products are changed to copper conductive rods and wiring clamps, similar problems still exist.

(2) The conductive tape of the old product is fastened by 4 M6 screws screwed into the aluminum conductive rod. Because the strength of aluminum is not high, dare not use force or excessive force when tightening, causing the internal thread slide buckle, which makes the contact pressure insufficient and causes overheating .

(3) Due to the reverse installation of the conductive tape, the direction of rotation is opposite to that of the isolating switch, or the heat of other parts causes the copper conductive tape to lose its elasticity due to overheating, or the conductive tape loses its elasticity due to long-term erosion by corrosive gas, which will cause it to lose its elasticity for a long time. During the operation, the copper conductive tape is broken, resulting in a decrease in the actual flow capacity and overheating.

3 Countermeasures for isolation switch to eliminate overheating defects

3.1 Do a good job in the early diagnosis of overheating defects

The terminal block, contact and other parts of the isolation switch should be pasted with test temperature wax or color-changing paint, so that the operator can find the overheating defect in time. It is best to carry out infrared temperature measurement work on the isolating switch regularly or irregularly, so as to more accurately grasp the real-time temperature, temperature rise and other operating conditions of the equipment.

3.2 Close the initial state

The isolation switch should be disassembled and repaired before it is put into operation. It is strictly forbidden to use defective and inferior clamps, bolts and other parts. Replace the bolt-type equipment clamps with crimping equipment clamps. The copper-copper, copper-aluminum connection adopts tinning process, and the joints are contacted. Clean the surface and apply conductive grease in time, use correct bolts and moderate tightening force.

3.3 Scientifically and rationally arrange maintenance and construction

For the bus-side isolating switch with high overheating frequency, it is necessary to ensure that the overhaul is in place and the quality of the overhaul. For the terminal block, focus on checking the connection of the two ends of the conductive tape to ensure that the two ends are clean, flat, smeared with conductive grease, and tightly crimped; for the contact part, ensure the smoothness of the contact, and apply neutral petroleum jelly to check the contact. If the head is burned, replace the contacts and fingers if necessary. The contact finger seat of the left contact should be polished clean, and the springs with overheating and rust should be replaced; the three-phase opening and closing synchronization and the insertion of the right contact should be ensured. The depth meets the requirements and the contact finger pressure on both sides is even. In order to check the quality of maintenance, the contact resistance of the loop should also be measured to ensure that the contact surfaces are in good contact.

Yichang Hengyuan Technology Co., Ltd. is a professional manufacturer of European-style cable connectors, plug connectors, cable branch boxes, American elbows, high-voltage vacuum circuit breakers, high-voltage load switches, lightning arresters, zinc oxide arresters, tank arresters, overvoltage protectors, Counters, monitors, heat-shrinkable cable accessories, cold-shrinkable cable accessories, T-heads, wall bushings, European cable accessories, American cable joints, transformer neutral point protection devices, fuses, isolating switches, PT cable heads, elbows Manufacturers of type cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products