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2020 High Voltage Circuit Breaker Failure Repair Guide

By:Nader Updated:September 09,2020 12:02PM

At present, in the power distribution network with voltage levels of 10KV and below, vacuum circuit breakers have gradually replaced oil circuit breakers, and have played an active role in the process of oil-free transformation. Compared with oil circuit breakers, vacuum circuit breakers have the advantages of being suitable for frequent operation, long electrical life, small maintenance workload, flame-proof, explosion-proof, and high operational reliability. There are several advantages that should be paid attention to during installation, debugging and application. The problem makes its superiority fully displayed.

1. Overvoltage protection

Because the vacuum circuit breaker breaks a small current. In particular, when a small induced current such as the excitation current of a no-load transformer is interrupted, the current is often intercepted and the intercepted over-voltage is generated, and the greater the intercept value, the higher the over-voltage generated. In addition, when the vacuum circuit breaker breaks the capacitive current of the capacitor bank, it is also difficult to achieve absolutely no arc reignition. Once reignition occurs, reignition overvoltage will also occur. For the interception or reignition overvoltage, it is necessary to install a metal oxide arrester or resistance-capacitance protection device with good performance to prevent it.

2. Detection of vacuum degree of vacuum interrupter

The vacuum degree in the vacuum interrupter tube is usually 10-4-10-6Pa. With the increase of the use time of the vacuum interrupter and the increase in the number of breaks, and the effect of external factors, the vacuum degree gradually decreases to A certain degree will affect its breaking capacity and withstand voltage level. Therefore, the vacuum circuit breaker must regularly check the vacuum in the arc extinguishing chamber tube during use. The current inspection methods are:

Regular visual inspection can be performed on the vacuum interrupter of the glass shell. Normally, the surface of the internal shielding cover and other components should be bright, and emit a light blue arc when the current is interrupted. When the degree of vacuum drops severely, the internal color will become dark, and a dark red arc will be emitted when the current is interrupted.

Conduct a power frequency withstand voltage test (42KV) regularly (about 3 years). When the static and dynamic contacts are kept at the rated distance, if the withstand voltage is very low, and after repeated discharge and aging, the withstand voltage still does not reach the specified withstand voltage standard, it means that the vacuum degree of the vacuum interrupter has been seriously reduced. It can no longer be used, and should be replaced in time.

3. The aging of vacuum arc extinguishing.

The electrical burn-in of the vacuum interrupter includes voltage and current burn-in. The new vacuum interrupter has been aging before the product leaves the factory. However, after a period of storage of the vacuum interrupter, due to various reasons, its work withstand voltage level will drop. After the switch manufacturer is assembled and the user department still needs to re-experience the voltage and perform it under the specified conditions. Power frequency withstand voltage test.

4. Contact overtravel and contact pressure control:

The specifications of the 10KV vacuum interrupter produced in my country have fixed standards, the more the contact overtravel is 3mm, the opening distance is about 12mm. Under normal circumstances, 10KV circuit breakers use the rated contact pressure of the arc extinguishing chamber, and the specific rated currents vary.

For the installation and repair of the vacuum circuit breaker, not only should the measuring contact overtravel be adjusted according to the manual, but also the contact spring should be checked repeatedly to see if it meets the standard, and shape changes are prohibited.

5. Detect contact wear value.

When the vacuum interrupter is in operation, it is mainly the contact breaking and dropping. After many times of operation, the contact surface of the contact will discharge and wear, which will increase the distance of the contact movement. At the same time, the work of the bellows is also formed. It increases and reduces the service life. Under normal circumstances, the maximum contact wear is about 3 mm. If it reaches or exceeds this value, it means that the vacuum interrupter can no longer be used.

In order to ensure that the vacuum interrupter meets the standard, measurement should be performed during installation, and the wear value should be counted during maintenance work. When the vacuum interrupter reaches its service life, it should be replaced immediately.

6. The impact of vacuum circuit breaker rebound on the arc extinguishing chamber.

Affected by the docking structure, the contacts of the circuit breaker will rebound during the opening and closing operation of the operating mechanism. The rebound has two forms, one is the opening rebound and the other is the closing rebound. Both rebounds affect the circuit breaker. The operation of the device. Specific hazard performance:

  1. The contact is severely burned, even welded.
  2. The bellows may crack when subjected to forced vibration, which may cause air leakage in the arc extinguishing chamber.
  3. The impact speed and large impact force during opening and closing may cause deformation of contacts and conductive rods, and even cracks.
  4. If the vacuum circuit breaker that is connected to the capacitor bank bounces, the capacitor will be damaged.

7. Measurement of opening and closing speed.

The opening and closing speed of a new circuit breaker should be measured before it is put into operation, because it can not only establish the original technical data, but also find some problems in product quality in time, so that timely measures can be taken.

Through the analysis and judgment of the above issues, operators and maintenance personnel find hidden dangers and eliminate them in time, avoid accidents, ensure the good operation of high-voltage circuit breakers, and ensure that the power grid is efficient, safe, and reliable, and the people can use the power of peace of mind.