The smart circuit breaker mechanism is located on the front of the circuit breaker. The mechanism adopts a five-link free release mechanism and is designed in the form of energy storage. During the use of the smart circuit breaker, the mechanism is always in the pre-storage position. As long as the circuit breaker receives the closing command, the circuit breaker can be closed instantaneously. The release of the pre-stored energy is done by the button or the closing electromagnet. The electric transmission mechanism is self-contained, and the energy storage shaft and the main shaft are movably connected by concave-convex wedges, which are convenient for assembly and disassembly.
1. The role of smart circuit breakers
Smart circuit breakers are used to control and protect low-voltage power distribution networks. smart circuit breakers are generally installed in low-voltage power distribution universal circuit breaker cabinets as the main switch for general protection. The technical performance of the universal circuit breaker has reached the advanced level of similar products in the world.
2. Characteristics of smart circuit breakers
2.1 Rated working voltage AC690V and below;
2.2 The universal circuit breaker has 3 poles and 4 poles.
3. Selection of smart circuit breaker
When the smart universal circuit breaker is used as electrical equipment or line protection, the user mainly considers the following four points when selecting the type:
3.1 The rated current of the selected circuit breaker is greater than or equal to the rated current of the circuit or electrical equipment;
3.2 The rated short-circuit breaking capacity (current) of the selected circuit breaker is greater than or equal to the expected (maximum) short-circuit current of the line;
3.3 The protection function of the selected circuit breaker is relatively complete and comprehensive, which can meet the requirements of its workplace;
3.4 The size of the selected circuit breaker is relatively small, which saves space, and the smart circuit breaker is convenient for installing multiple circuit breakers in the same cabinet.
4. Classification of smart circuit breakers
Low-voltage circuit breakers are divided into structure, use and functions. smart circuit breakers mainly include universal type (also known as frame type) and plastic shell type. There are also some special-purpose circuit breakers, such as vacuum circuit breakers.
5. Working principle of smart circuit breaker
Smart circuit breaker is a new secondary system of circuit breaker built with microelectronics, computer technology and new sensors. Its main feature is that the execution unit is composed of power electronic technology and digital control device, which replaces the auxiliary switch and auxiliary relay of the conventional mechanical structure. The new sensor cooperates with the digital control device to collect operating data independently, detect equipment defects and faults, and send out alarm signals before defects become faults, so as to take measures to avoid accidents. The smart circuit breaker realizes electronic operation, changes the mechanical energy storage to capacitor energy storage, and changes the mechanical transmission to the direct drive of the inverter through the motor, which improves the reliability of the mechanical system.
Smart circuit breakers have been developed accordingly. Circuit breakers with smart operation functions are based on the introduction of smart control units on the basis of existing circuit breakers. It consists of three basic modules: data acquisition, smart identification and adjustment devices. The smart identification module is the core of the smart control unit. The microcomputer control system composed of a microprocessor can automatically identify the grid in which the circuit breaker is located during operation according to the grid information collected before operation and the operation signal sent by the main control room. In the working state, the appropriate opening and closing motion characteristics are determined according to the results of the simulation analysis of the circuit breaker, and adjustment information is sent to the actuator, and the opening and closing signal is sent after the adjustment is completed; the data acquisition module is mainly composed of new sensors. The data of the power grid is provided to the smart identification module in the form of digital signals for processing and analysis; the actuator is composed of components that can receive quantitative control information and drive actuators, and is used to adjust the parameters of the operating mechanism so as to change each operation. motion characteristics. In addition, display modules, communication modules and various detection modules can also be installed as needed to expand the smart functions of the smart operation circuit breaker.
The basic working mode of the smart circuit breaker is to automatically select the preset working conditions of the operating mechanism and the arc extinguishing chamber according to the detected different fault currents. Higher speed opening to obtain the best opening effect in terms of electrical and mechanical performance.
This kind of smart operation requires the circuit breaker to be controllable in terms of mechanism action time. Pneumatic operating mechanisms, hydraulic operating mechanisms and spring operating mechanisms commonly used in circuit breakers have large control time discreteness due to factors such as intermediate conversion media, and their motion characteristics are difficult. To achieve the ideal controllable state. Circuit breakers using electromagnetic operating mechanisms use capacitor energy storage, permanent magnet retention, electromagnetic drive, electronic control and other technologies. When the mechanism is determined, there is only one moving part, and there is no intermediate conversion medium. The opening and closing characteristics are only related to coil parameters, which can be determined by Microelectronics technology is used to achieve microsecond-level control, and the smart operation of the circuit breaker is realized by controlling the speed characteristics.
The working process of the smart operation circuit breaker is: when the system fails, the relay protection device sends out the opening signal or the operator sends out the operation signal, first start the smart identification module to work, judge the current working conditions of the circuit breaker, and adjust the adjustment device Send out different quantitative control information to automatically adjust the parameters of the operating mechanism to obtain the motion characteristics suitable for the current system working state, and then make the circuit breaker act.
6. Application of smart circuit breaker
The circuit breaker is used to monitor the power supply and protect the power grid system. When the load of the grid system continues to be overloaded within a set period of time, it will issue a trip command, and the mechanical actuator of the circuit breaker will immediately switch off the power supply to protect the power grid. system. In fact, the fuse is also like this. It is impossible to blow the fuse with a very short pulse overload. Only when the load continues to be overloaded for a certain period of time will it be blown. The difference between a circuit breaker and a fuse lies in its "intelligence". The threshold of the load is not fixed, but can be set; the time allowed for the load to continue to overload can also be set. In addition, smart circuit breakers have other smart functions.