Auto Reclosing Circuit Breaker is widely used in overhead line transmission and overhead line power supply lines on the effective anti-accident measures (cable transmission, power supply can not be used).

That is, when the line fails, after the circuit breaker is tripped by relay protection, the automatic reclosing device closes the circuit breaker again after a short time interval. In most cases, line faults (such as lightning stroke, wind damage, etc.) are temporary. The insulation performance (insulator and air gap) of line can be restored after circuit breaker tripping, and the reclosure can be successful, which improves the reliability of power supply in power system.

The minimum interval allowed for Auto Reclosing Circuit Breaker is 0.15 to 0.5 seconds. The higher the rated voltage is, the longer the insulation deionization time is. The success rate of automatic reclosure depends on the line structure, voltage level, meteorological conditions and main fault types.

According to the statistics of China's power sector, it can reach 60% to 90%. Another widely used anti-accident measure in power sector is the automatic input of standby power supply, which usually takes 0.2-0.5 seconds. It does not require much investment and the economic benefits of maintaining normal power supply are great.

The main functions of Auto Reclosing Circuit Breaker are:
1. It greatly improves the reliability of power supply and reduces the number of power outages, especially for single-circuit lines with one-side power supply.
2. Reclosing on high voltage transmission lines can also improve the stability of power system running side by side.
3. In the process of design and construction of power grid, in some cases, the double-circuit line can be postponed to save investment due to the consideration of reclosure.

4. It can also correct the wrong tripping of circuit breaker itself caused by bad mechanism or misoperation of relay protection.

The economic benefit of reclosure should be measured by the national economic loss caused by power outage when there is no reclosure. Because the reclosing device itself has low investment and reliable operation, it has been widely used in power system.

What is over-under voltage?
Power supply instability, outdoor harsh environment, aging of household lines, high-power electrical appliances start-up, shutdown and other voltage caused by short-term or long-term instability.

What is the danger of over-under voltage?
When the line is in the overvoltage state, because the voltage exceeds the specified value of the power grid or the endurance value of the electrical appliances, the electrical components will be damaged, and serious electrical fires will occur. When the line is under-voltage, due to insufficient voltage, the internal components of electrical appliances will be damaged, and fire may occur. Especially when the motor is under-voltage, the motor speed will be reduced. For the automation industry, the uncoordinated motor speed will directly lead to equipment damage and major security risks.

Conventional voltage protection devices are over-under voltage protectors, which can be divided into manual and automatic ones. Automatic ones, such as reset over-under voltage protectors, can realize fast interruption when overvoltage reaches 270%% 5V and undervoltage reaches 170%% 5V. When voltage restores to stability, the internal relay of the protector will work with a delay of 30s. The right or left will automatically turn on the circuit. Process automatic processing, no artificial operation, simple and save time and effort. Over-voltage and under-voltage circuit breakers are based on over-voltage and under-voltage protection to increase the protection capacity of circuit breakers: overload protection, short circuit protection, leakage protection, etc. The conventional scheme is to install over-voltage and under-voltage accessories beside the circuit breaker, but this voltage protection devices can only be operated manually after the protection of the circuit breaker is released, and can not be reset movably, and does not have leakage protection. The first shield electronic over-voltage and under-voltage circuit breaker is a new type of voltage protection devices. It has self-repetitive over-voltage and under-voltage protection, and adds overload protection, short circuit protection and leakage protection. It is an integrated self-repetitive over-voltage and under-voltage protection. Its function is integrated on the circuit board, which greatly saves the internal space of the circuit breaker and increases the working stability of the product.