The application of vacuum circuit breakers to study the use of vacuum circuit breakers and the protection of Ren Mingxia, the thermal power plant of the Shanxi branch of the China Mistakes Corporation, should pay attention to the maintenance process, and pointed out that attention should be paid not only to the upgrading of equipment but also to the overhaul of equipment. Home care can ensure its good operation.
A Article No. 1 Use Characteristics of Vacuum Circuit Breakers Currently in power distribution systems with voltage levels of 10 and below. Vacuum circuit breakers have gradually replaced oil circuit breakers. Compared with the oil circuit breaker, the vacuum circuit breaker has high insulation strength and strong arc extinguishing ability. The travel of the contact is very small. The operating power of the operating mechanism is very small and the circuit breaker is small, light and no noise. The arc extinguishing time is short, the arc voltage is at the end, the arc energy is small, and the contact loss is low. Therefore, there are many breaks. long lasting. Suitable for frequent operation. During the service life of the vacuum interrupter, the contact part does not require maintenance inspection. Even if the operating agency needs maintenance inspection, it is very simple.
2 It should be noted during use and maintenance 2.1 Overvoltage protection. Due to the small breaking current of the vacuum circuit breaker, especially when the small induction current such as the excitation current of the no-load transformer is opened. There will often be closure and electricity. The more the closure value. The higher the generated electricity is. In addition; true; broken; with; in the breaking capacitive current capacitor bank. It is difficult to achieve absolutely no re-ignition of the arc, and if re-ignition occurs, re-ignition overvoltage will occur. For shutoff or re-ignition overvoltage. Must install better performance metal oxide arrester or resistance capacity protection device to prevent, 2.2 vacuum interrupter vacuum detection. The degree of vacuum in the vacuum interrupter tube is usually at the time of (1) (1) rejection along with the use time of the arc extinguishing chamber, the length and the number of times of breaking, and more. As well as being affected by external factors, the degree of vacuum is reduced, and reducing it to a certain degree will affect its breaking capacity and withstand voltage level. Therefore, vacuum circuit breakers must periodically check the degree of vacuum in the arc chamber during use.
For glass enclosure vacuum interrupters, inspections can be performed visually at regular intervals. When the degree of vacuum is normal, the interior shield surface is very bright. Light blue arc when breaking current. When the vacuum level drops, the internal color becomes dark and a dark red arc is emitted when the power is turned off.
i! tj3HiIUrlI;l,ii! miA42kVLil static and dynamic contacts maintain nominal open distance conditions. If the pressure is very low, and after repeated discharges after aging. The pressure resistance value is still not up to the specified pressure standard, indicating that the degree of vacuum in the vacuum interrupter has been seriously reduced. Can not continue to use.
2.2.3 Vacuum interrupter aging. The vacuum arc extinguishers include voltage aging and current aging. The new arc extinguishing chamber is old before the product leaves the factory.
But after a period of time stored. Its power frequency withstand voltage level will drop, and it still needs 1å£¬æ˜Žéœž. Female. Born in April 1966. In 1988, he graduated from the Department of Electrical Engineering of University of Applied Sciences. engineer. The Hejin City of Shanxi Province has been re-performing the voltage aging and the power frequency withstand voltage test under the specified conditions.
4 contact overtravel and contact pressure control. , Domestic various types of 10 series vacuum interrupter contact over-travel in 3,1. Open distance 12, about.
Domestic 10 government vacuum circuit breaker rated voltage of the arc extinguishing chamber rated current 63, long, 4 are right. The rated current is 125. The person is a vacuum circuit breaker during installation or overhaul. In addition to adjusting the measuring contact overtravel in strict accordance with the requirements of the product installation instructions, the contact springs should also be carefully checked. There should be no deformation damage phenomenon, 5 contact wear value monitoring. The contact surface of the vacuum interrupter contacts the arc gradually after many times of breaking current, the contact stroke increases, and the life of the bellows rapidly decreases. The maximum allowable contact wear is 3,1 when the cumulative wear value reaches or exceeds this value. The vacuum interrupter's breaking performance and electrical conductivity will decrease. The service life of the vacuum interrupter has come. In order to more accurately control the electrical wear value of each vacuum interrupter contact. Must be installed from the start of the arc extinguishers. Each pilot test or maintenance must accurately measure the open distance and compare it with the overtravel when the contacts wear out. The cumulative reduction is the cumulative electrical wear of the contacts and the effect of the vacuum circuit breaker bounce on the interrupter. The contacts of the vacuum circuit breaker are mostly butt-type structures, and they are in separate operations. There may be different degrees of rebound. No matter whether it is a trip or a rebound, it will bring harm to the operation.
The rebound may cause severe burning of the 1 contact, or even welding. This bellows undergoes forced vibration that may generate cracks that allow the arc-extinguishing chamber to leak. The impact speed and impact force at the time of closing and closing are large, and bounce occurs. Deformation of the contacts and conductive rods, and even cracks. If a vacuum circuit-breaker with a capacitor bank is used, the closing of the circuit breaker will cause damage to the capacitor.
2.2.7 Closing speed measurement. The new circuit breaker is in operation. Measure points.
Explain the speed and establish original technical data. In order to promptly find the quality of the product asked. 1 Miao Qing. Vacuum circuit breakers are used to remove the vacuum in the room and check the degree of scraping. Power automation production I2I Court. The vacuum circuit breaker is opened and closed, and the operating overvoltage at the same moxibustion load is used. Beijing China Electric Power Press, 2001.157.
The requirement does not exceed 1.5 when 3.0. Motor loss will increase 26.
In this case, the motor will overheat, and the heat generated by the motor itself will often cause short-circuit between windings or between windings. The windings are grounded, and the leads are overheated due to overheating of the windings caused by the imaginary soldering; the core silicon steel sheet is damaged by insulation and forms eddy currents and generates heat; the rotor broom generates friction and heat; and bearing failure causes the motor bearings to overheat. Such as burned motor stator windings, overheating often occurs during operation after maintenance. This is mainly due to the use of stator stator windings and motor cores in the stator core silicon steel sheet, which causes insulation damage between the stator and the steel sheet. When the motor winding is used after repair, the eddy current loss increases to cause the motor core to overheat. This happens mostly on motors that have been overhauled and replaced with windings.
2.3 Heat caused by the load Long-term overload operation will cause the motor windings to heat over long-term overload current. Some winches use motors with short working cycles to start the motor too often. Improper motor selection can also cause the motor to overheat. Selecting the motor according to the use condition of the motor is the key to the normal operation of the motor. The author once went to a crane that should use a type of motor. A repeated short-duration duty motor with a duty cycle of 25 was selected, resulting in overheating of the motor. When choosing a short-duration duty motor, when the load continuation rate is too small, or when the short-time work motor is selected, the standard operating time is too short, and when the short-duration work motor is used instead of the repeated short-time work motor, A comparison was made between the standard operating time and the load persistence rate, but no overload checking was performed. Causes the motor to overload. Causes the motor to overheat.
2.4 Bad heat dissipation causes the motor to generate heat If the ambient temperature is too high, there is too much dust inside the motor. Any blockage in the air duct will increase the temperature of the motor. The overheating of the motor caused by reverse mounting of the fan or reverse rotation of the fan is the most easily overlooked issue. We know that most motors rely on coaxially installed fans to force air-cooling. If the axial fans are installed in reverse maintenance, especially if the phase fan attached to the motor is out of phase, the reverse rotation is often not the case. Note that the amount of ventilation is reduced as a result. The motor will also overheat.
In recent years. In the coal mine. The distribution voltage increased from 380 in the original list to 380,660, 4, and other voltage levels. There were many 40 660 and 660 to 380 motors. Incorrect wiring of the installer will cause the motor to overheat.
3 Preventive measures 3.1 Strengthen the monitoring of the power supply, generally allow the power supply voltage to change within the range of +105 when the motor output does not change. If the change is too large, relevant departments should be notified to make adjustments. At the same time, special attention should also be paid to the phase of the power supply voltage balance. If it is too abnormal, it should be analyzed and handled in a timely manner. 3.2 Periodic pre-testing and regular maintenance should be strengthened so that timely detection can be done to eliminate hidden dangers. Important motor pre-test cycles can be set to 1 year. It is not important to set the motor for 2 years and 3 years. The pre-test items include insulation resistance and absorption ratio test, winding DC resistance test, DC stator withstand voltage and leakage test of more than 1000. The regular maintenance schedule stipulates that the motor will be repaired twice a year for 3 years and repaired twice. Minor repairs 2 times. In the wet. Dust corrosive place motor. The number of minor repairs should be appropriately increased, maintenance and repair should follow the normal operating procedures, should not only save time and effort.
3.3 timely adjust the motor load, regular inspection of the dragged machinery and its transmission mechanism to ensure that it is running well and without failure. According to the size of the load. Correctly calculate the motor that matches the rated capacity and load. 3.4 Improve the ventilation condition of the motor and keep the surrounding environment clean. 4 Concluding remarks Aiming at the causes of motor heating, aim to prevent accidents, reduce motor accidents, and reduce accident losses. It is of great significance to improve the economic efficiency of enterprises. If the motor is overheated. Be sure to find out why. Timely treatment will eliminate the danger in the bud, which is conducive to the safe operation of the motor.
1 Xu Shizhang. Electrical Engineering. Beijing Mechanical Industry Press. 1984.
Editor-in-Chief Xue Peirong Continued on page 60
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