What are the precautions for using a circuit breaker?

In the 35KV standardized substation, the ZW32-24 Outdoor High Voltage Vacuum Breaker uses the principle that the control bus and the closing bus are separated.

Between the auxiliary normally closed contact of the circuit breaker and the closing coil, a pair of normally open contacts of the circuit breaker’s energy storage stroke switch are connected in series into the control circuit. Thus, when the circuit breaker does not store energy, the closing operation cannot be performed. Prevents the circuit breaker from closing without storing energy, maintaining the closing circuit, and burning the closing coil.

At the same time, during the wiring process, it should be noted that the polarity of the closing bus and the control bus in the energy storage stroke switch contact should be consistent to prevent the arc of the closing circuit from breaking through the stroke switch when the switch stores energy, causing the control insurance to fuse or the control air switch to fall off. This should be paid special attention to in integrated automated substations.

Operation maintenance and repair test

The ZW32-24 Outdoor High Voltage Vacuum Breaker has a short arc burning time, high insulation strength, high electrical life, small opening distance and stroke of the contacts, and low operating energy, so the mechanical life is also high. In daily operation, the maintenance workload is very small. The main thing is to check the wear of the moving parts of the mechanism, whether the fasteners are loose, remove dust from the insulation surface, inject some grease into the moving parts, etc.

In the preventive test, the DC resistance test of the switch should be compared with historical data, and problems found should be dealt with and replaced in a timely manner. The power frequency withstand voltage test of the broken port is an effective method to check whether the vacuum bubble is leaking air. (The indoor vacuum circuit breaker can draw on the color of the flash inside the vacuum bubble to initially judge the vacuum level of the vacuum bubble when the load is disconnected. When the color is dark red, the vacuum level is low, when the color is light blue, the vacuum level is good.) During protection and planting verification, the circuit breaker is tested for low voltage to check whether the switch works reliably when the bus is in a state of failure and when the voltage drops.

Advantages of vacuum circuit breakers

1. The ZW32-24 Outdoor High Voltage Vacuum Breaker stops the arc in a sealed container, and the arc and hot gas are not exposed. As a separate element, the arc extinguishing chamber is simple and convenient to install and debug.
2. The contact gap is very small, generally around 10mm, the closing force is small, the mechanism is simple, and the service life is long.
3. The arc extinguishing time is short, the arc voltage is low, the arc energy is low, the contact loss is small, and the number of breaks is high.
4. The moving guide rod has low inertia and can be used frequently.
5. The operating mechanism is small, the whole machine is small in size and light in weight.
6. Low control power and low motion noise during switch operation.
7. The arc extinguishing medium or insulation medium does not use oil, there is no risk of survival or explosion, and is safe.
8. The contact part has a completely sealed structure, and its performance will not be affected by moisture, dust, harmful gases, etc. It works reliably and has stable on-off performance.
9. After the arc is broken, the medium between the fractures recovers quickly, and the medium does not need to be replaced.
10. It will not age or need to be replaced. During the service life, the contact part does not require maintenance or inspection. Generally, it can be about 20 years without maintenance. The maintenance workload is small and the maintenance cost is low, only about 1/20 of a low-oil circuit breaker.
11. It has multiple reclosing functions and is suitable for distribution grid application requirements.

Disadvantages of vacuum circuit breakers

1. When the inductive load or capacitive load is switched off, it is easy to cause overvoltage due to interception, proper combustion, etc., and appropriate overvoltage protection should be taken.
2. The ZW32-24 Outdoor High Voltage Vacuum Breaker has a high one-time investment price, which is mainly determined by the professional production and institutional reliability requirements of the vacuum arc extinguishing chamber. If operation and maintenance costs are taken into account, the price is not high.
3. Since the contact structure of the vacuum circuit breaker is docked, the actuating mechanism uses springs, which are prone to closing and splitting bounce. Closing and bouncing will not only cause a high overvoltage to affect the stable operation of the power grid, but also cause contact burnout or even welding, especially when the input capacitor pack generates an inrush current and when a short circuit is closed. The split gate rebound will reduce the contact spacing after the arc, causing a heavy breakdown after the arc. The consequences are very serious.

Vacuum circuit breaker application

Vacuum circuit breakers commonly used in high voltage switch cabinets are indoor vacuum circuit breakers, such as the ZW32-24 Outdoor High Voltage Vacuum Breaker. At present, vacuum circuit breakers with 6KV and 10KV voltage grades in China have basically replaced oil circuit breakers, and their utilization rate has exceeded 96%; the utilization rate of vacuum circuit breakers at 35KV voltage grades exceeds 62%. The ZW32-24 Outdoor High Voltage Vacuum Breaker has become the most widely used circuit breaker in the medium voltage field below the 35kV level.