Isolation switch heating analysis The isolation switch is mainly composed of supporting base, conductive part (contact, knife, terminal block, lead wire clamp), insulator, transmission mechanism and operating mechanism. The overheated part is mainly concentrated on the contact of dynamic and static contacts. The causes of heat generation such as parts and lead wire clamps can be divided into internal and external causes. External causes include: ambient temperature, product manufacturing quality (material technology), external force, natural disasters, etc.; internal factors include: installation quality, operation management (early discovery) Poor contact between the contact part and the lead wire clamp. The following is an analysis of the causes of fever that are often seen during the actual operation of maintenance and repair:
1. When the isolation switch is in the closing operation state for a long time, if the quality of the finger spring is not good, metal fatigue will easily occur, the elastic index will decrease, and after closing, the contact pressure between the contact and the finger will be reduced. Small, resulting in increased contact resistance and heating of the contacts; heating of the contacts causes the spring to be heated, the elastic index is further reduced, and the contact resistance is further increased. Eventually the finger spring will lose its elasticity and the contact resistance will be greater, causing a sharp rise in temperature to burn the contact.
2. The isolation switch is in the open position for a long time. The surface of the static and dynamic contacts is dirty or forms an oxide film, which affects the closing contact effect. For the wiring mode of the double busbar of the substation, a set of isolation switches are in the opening position for each interval. Due to the erosion of water vapor, corrosive dust and chemically active gas, the static and dynamic contacts are corroded and fouled, and an oxide film is formed on the surface. When the switch is switched to the closed state, the contact surface oxidation increases the surface resistance of the conductor, resulting in poor contact. And fever.
3. In the summer and autumn seasons. The ambient temperature is high and the load current is large. At this time, the load current of the isolating switch is obviously increased. In addition, the temperature is high, the heat dissipation is difficult, the equipment is continuously operated under high load conditions under severe conditions, and the temperature of the equipment is continuously increased. For reasons such as power supply protection, it is impossible to timely power off and overhaul. If the equipment exceeds the maintenance period, it will easily cause the equipment material to age and the conductivity to decrease, causing the knife gate contacts to heat up. If the operation mode changes, the overload will occur, and the contact will even be caused. Burnt.
4. The contact points between the lead and the bolt type clamp are also frequently heated. The main reasons are: bolt fastening is not in place; vibration during operation and operation; thermal expansion and contraction, rain, dust and continuous erosion. These causes will result in insufficient contact pressure and contamination of the contact area, resulting in an increase in contact resistance resulting in heat generation. When the wind is strong, the wire will also swing. Causes the connecting screw to loosen and increase the contact resistance.
5. The operation personnel manually operate the knife gate is not standardized, the consequences are: mechanical wear, that is, the mechanical closing force impact is too large, the contact deformation cracks, peeling, jamming; arc erosion, closing operation process is not decisive and quick, touch The head is subjected to an arc for a long time and the surface metal is molten, which not only causes the contact to generate heat, but also shortens the service life of the contact.
6. During the initial installation adjustment or maintenance work, due to the limited technical level and unreliable responsibility of the installers and maintenance personnel, the installation and overhaul processes do not meet the requirements. The contact surface of the joint is improperly treated, burr, not smooth and flat; the bending or twisting angle of the conductor is not in place; the fastening force of the fixing screw is not balanced; the conductive paste is unevenly applied or excessive, and even the unqualified conductive paste is used.
7. The environmental conditions for the storage of the components before installation do not meet the requirements. At the construction site, the storage conditions did not meet the requirements due to objective reasons. In addition to the delay of the construction period, the equipment components are placed in the open space for a long time. If it encounters rain and fog weather, the conductive parts and fastening parts of the parts are easily dampened to form an oxide layer before being installed. If there is no inspection before installation, there will be hidden dangers of heat. The isolating switch heat treatment method handles the isolation switch heating fault. Maintenance personnel should strengthen contact and assistance with operators. Because the isolation switch is partially overheated, first locate the part. The color of severely heated parts is different from normal. When the copper conductor is severely heated for a long time, the color is dark. The aluminum conductor is whitish. However, under normal circumstances, the degree of discoloration or the discoloration of the discolored parts cannot be observed. This is to be judged by means of the instrument. At present, the infrared switch is used to measure the temperature of the isolated switch in operation. This method can accurately find the hot spot of the equipment in operation. If the equipment is in the state of inspection when the maintenance personnel arrives at the scene, the heating point can only be judged according to the description in the defect form reported by the operating personnel. This requires the operating personnel to specify the hot part when reporting the defect. If conditions are met, a temperature measurement picture should be attached. Otherwise, there may be repeated power outages due to inaccurate processing locations, and there are similar situations in actual work. The method of heat treatment of the contacts disassembles and decomposes the static contacts. Check whether the contact surface between the inner surface of the static contact and the conductive rod has discharge marks, oxides, whether the fixing nut is loose, whether the spring pad is annealed or not; remove oxides, smooth the burn marks, and reinstall the lock nut; Decompose, remove the burn marks and oxides on the surface of the moving contact, check whether the finger spring is annealed, check the contact finger and the internal contact surface for burn marks and oxides, replace the burnt fingers and springs, replace the aging bolts and The spring pad is finally reassembled according to the requirements of the process standard; after the overall reassembly, the adjustment test should be carried out according to the standard. The project includes: the contact depth and area of ​​the moving and static contacts, and the treatment of the contact resistance test lead and the bolt type clamp. Method Open the wire clamp to find the burned part and area of ​​the wire and the clamp, determine whether the wire breaks and the degree of fatigue, whether the burned wire clamp is deformed, whether the mechanical strength can be maintained, whether it can be used continuously; if it is a mild burn, the wire and the wire The clip can continue to be used, and the burn scars on the inner surfaces of the wires and clips should be removed first. And smooth with 0 sandpaper. Then use a wire brush to completely remove the oxide, sulfide, and dirt on the surface of the wire and the surface of the wire clamp, and then clean the wire gap and the metal debris on the wire clip with a metal cleaner or gasoline. Finally, follow the screw fastening process. Evenly tighten the diagonal. If the bolt, nut slip, slip wire or burn, it should be replaced; if the wire clip is deformed by burn, the strength is slack, the wire is fatigued and the strand is broken, the wire and clamp should be replaced in time. The prevention and control measures of the isolating switch heating shorten the overhaul period of the isolating switch in the main interval and the heavy load line interval from the operation level; the parts with heat hazard are replaced with qualified new parts during the overhaul process. Strengthen the inspection during the operation and find the fault in time.
From the level of installation and maintenance, select a construction team with strong technical force and strong sense of responsibility; strengthen the control of key points of maintenance, and eliminate hidden dangers from the maintenance level. When the installation and maintenance work is completed, check the clamping of the isolating switch and the wire clamp with a feeler of 0.05 mm × 10 mm; carefully check the results of the contact resistance test.
When operating the disconnector from the operating level, if manual splitting is used, the start should be slow and cautious. Observe the flexibility of the isolating switch drive system and the movement of the conductive rod, and observe whether the knife lock is in synchronization. When closing, the isolation switch should be quickly and decisively closed when the moving and static contact is in contact (information source: http://), but it should not be used too hard to prevent the damage of the knife drive mechanism and the insulator; When opening the brake, when the moving and static contact just leaves, it should be quickly opened to minimize the arcing time to reduce the arc burning loss of the moving and static contacts. After the operation is completed, carefully check the fit of the knife gate. Whether the insertion depth of the static and dynamic contacts meets the requirements, whether the knife gate is in place, etc. Make sure it works well.
After the equipment from the storage level is delivered to the destination, it should be placed in a ventilated and dry place. It should not be inverted. It should be checked and installed as soon as possible. If it is not used immediately, it should be kept in a rainproof and ventilated place and checked regularly. (no more than six months at a time). In addition, the acceptance of the pre-installation components and the equipment after installation is also particularly important. Some manufacturers are not strict with the assembly quality of the factory products, and the bolts are not in place. In particular, the inside of the terminal block is less likely to be found and will be run to the equipment. Bring hidden dangers, therefore, when installing and debugging and accepting the isolating switch, the installation process of the isolating switch must be strictly implemented. The acceptance personnel shall strictly check and accept according to the acceptance specifications. Disintegration sampling if necessary. The tightening and lubrication of each joint should be carefully checked. In the process of acceptance. It is necessary to make the transfer of the information and save the manual so that the model can be checked when a certain part needs to be replaced in the future.
The best way to completely solve the heating fault of the isolating switch is to perfect it and update it. However, in the case of non-performing conditions, the subjective initiative of technicians at all levels should be exerted from the aspects of maintenance management and operation and maintenance. Through the maintenance cycle management, maintenance process management, operation and maintenance management, operation operation key point control, daily inspection and other means to ensure the old Smooth and reliable operation of old equipment.
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