First, the leakage of vacuum arc extinguishing chamber
1. Fault phenomena and causes
Vacuum circuit breaker is characterized by arc extinguishing in vacuum, but not in any vacuum degree can be, but in a certain vacuum degree range has good insulation and arc extinguishing performance. The internal vacuum in the vacuum switch is usually in the range of 6.5×10-1.3×10 Pa. The performance of vacuum arc extinguishing chamber WILL BE AFFECTED by the different vacuum arc extinguishing chamber, the different structure of dynamic and static contact, the different sealing of shield, the different shell material, the different bellows material and processing method, etc. The vacuum technology in our country has ensured the vacuum degree needed in vacuum switch, and the sealing technology can ensure that does not leak, maintains the vacuum degree. The electric life of the vacuum circuit breaker is determined by the electric life of the vacuum arc extinguishing chamber. The pollution level, humidity, and salt spray of the application or storage environment of the HV vacuum circuit breaker are not appropriate. The harmful gas and condensation may cause spotty corrosion of the bellows, resulting in air leakage of the bellows, cover plates, and sealing surfaces.
With the increase of the service time and the number of breaks, the vacuum degree of the vacuum interrupter chamber will gradually decrease, which will affect its breaking ability and pressure resistance level to a certain extent. The contacts of the vacuum circuit breaker are mostly of the butt type structure, which may produce different degrees of rebound during the opening and closing operation, which will bring harm to the operation. When the impact velocity and impact force are large, the deformation of the contact and the conductive rod may occur, and even cracks may occur. The rebound may lead to cracks in the bellows subjected to forced vibration, and the air leakage in the arc quenching chamber may occur.
The vacuum circuit breaker interrupts the current and interrupts the arc in the vacuum bubble, but the vacuum circuit breaker itself has no device to monitor the vacuum characteristics qualitatively and quantitatively, so the vacuum degree reduction fault is a hidden fault, and its danger degree is far greater than the explicit fault. The reduced vacuum degree will seriously affect the ability of the vacuum circuit breaker to break the overcurrent, and lead to a sharp decline in the service life of the circuit breaker, and even cause the switch explosion.
2. Fault prevention
Vacuum circuit breaker must periodically check the vacuum degree in the arc extinguishing chamber during use. The current inspection methods are as follows:
(1) The glass shell vacuum arc extinguishing chamber can be inspected regularly by visual inspection. Normally, the surface color of the internal shielding cover and other components should be very bright, and light blue arc light will be emitted when the current is broken. When the vacuum degree drops very badly, the interior color will become dark, and when the current is turned off, it will emit a dark red arc light.
(2) regular (3 years or so) a power frequency voltage test (42 KV). If the power frequency tolerance voltage is not lower than the rated power frequency tolerance voltage, it indicates that the vacuum degree meets the requirements. If the continuous breakdown or glow discharge occurs in the vacuum arc extinguishing chamber during the voltage boost process, it indicates that the vacuum degree of the vacuum arc extinguishing chamber has seriously decreased and can no longer be used.
3. Troubleshoot the fault
The IMPORTANT measures to solve the problem of air leakage in vacuum extinguishing chamber are to ensure that the overstroke and contact stroke of HV vacuum circuit breaker are in the prescribed range, and the reasonable choice of use and storage environment.
During the installation or maintenance of vacuum circuit breaker, in addition to strictly according to the requirements of the product installation manual to adjust the measuring contact excess stroke. Vacuum arcing chamber of the contact interface will gradually be after after a lot of open circuit current electrical wear and increase contact trip, is quite a corrugated pipe working stroke increases, the service life of bellows will fell rapidly, often contact electrical wear a maximum of 3 mm to the left or right when the cumulative wear value reach or exceed this value, the breaking performance of vacuum arcing chamber and electric conductivity will decrease, The service life of the vacuum arc extinguishing chamber has reached.
4. In order to accurately control the electrical wear value of each vacuum arc extinguishing chamber contact, it is necessary to accurately measure the opening distance and overstroke and compare them from the beginning of the installation and use of the arc extinguishing chamber, each preventive test or maintenance. When the contact wear decreases, the cumulative electrical wear value of the contact is the cumulative electrical wear value
The new circuit breaker should be measured before the operation of points, closing speed, because it can not only establish the original technical data, but also timely find some problems in product quality, in order to take timely measures.
When the vacuum degree is reduced, it is necessary to replace the vacuum bubble, or replace the vacuum circuit breaker, and do a good job of travel, the same period, bounce and other characteristics of the test.
Zhejiang Zhi Duoxin Electric Co., Ltd.
