Introduction to the basic principle, working mode

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Introduction to the basic principle, working mode and working process of intelligent circuit breaker

with the rapid development of power construction in China, digital substation has become a hot spot of construction and research. The core of digital substation lies in the intellectualization of primary equipment and the networking of secondary equipment. For the circuit breaker, which is an extremely important power primary equipment, the realization of its intelligence is of great significance. The intellectualization of circuit breaker lies in the real-time monitoring of operation status, accurate on-off, intelligent control and information transmission networking. With the wide application of power electronic technology and automatic control theory, the rapid development of computer and network communication technology, as well as the in-depth research and comprehensive application of technology and artificial intelligence, the function of intelligent circuit breaker has been greatly expanded and improved

first, what is intelligent circuit breaker

circuit breakers are divided into high-voltage circuit breakers and low-voltage circuit breakers according to their scope of use. The division of high-voltage and low-voltage boundaries is relatively vague. Generally, those above 3KV are called high-voltage appliances

low voltage circuit breaker, also known as automatic switch, is an electrical appliance that not only has the function of manual switch, but also can automatically protect against voltage loss, undervoltage, overload and short circuit. It can be used to distribute electric energy, start asynchronous motors infrequently, protect power lines and motors, and automatically cut off circuits when they have serious overload, short circuit, undervoltage and other faults. Its function is equivalent to the combination of fuse switches and over and under heating relays. Moreover, it is generally not necessary to change parts after breaking fault, which has been widely used

high voltage circuit breaker (or high voltage switch) is the main power control equipment of the substation, which has arc extinguishing characteristics. When the system operates normally, it can cut off and connect the no-load and load current of lines and various electrical equipment; When the system fails, it can quickly cut off the fault current in cooperation with the relay protection to prevent expanding the scope of the accident. Therefore, the working quality of high-voltage circuit breaker directly affects the safe operation of power system

with the development of the national economy and the continuous progress of technology, both industrial production and daily life have put forward higher and higher requirements for the power supply quality of the power system: to achieve uninterrupted power supply, even if the power is cut off, the power cut time must be as short as possible and the power cut range must be as small as possible. This requires the power supply system to have a relatively high degree of automation and intelligence. When there are some faults in the power system, the intelligent protection equipment in the system can identify the fault type in time, quickly cut off the fault part in the system, prevent the further expansion of the fault, and make the whole system operate normally. In addition to the normal opening and closing of the rated current of the relevant system, the short-circuit fault current of the relevant system should be able to be quickly, selectively and reliably disconnected when the relevant system fails, and there should be no skip tripping or refusal to operate

when the relay protection or control device sends an external tripping command, when the command reaches the circuit breaker, the control device of the circuit breaker determines whether the circuit breaker is ready to perform the opening and closing operation. If it is ready, the control device is responsible for completing the command operation. On the contrary, if the circuit breaker is not ready, the control device locks the required operation, and the circuit breaker cannot complete the corresponding command operation. Therefore, the circuit breaker needs corresponding control and monitoring circuits, such as gas density, opening and closing position of the circuit breaker, etc. In addition, the control circuit is required to monitor the key parameters that reflect the operating status of the circuit breaker. If these parameters change, the circuit breaker will be locked so that it is not allowed to act, and a warning will be issued to the operation personnel on duty, so that the operation personnel can take action in time. Taking the substation of Longkou power supply company as an example, in the secondary circuit of general 10kV or 35kV outgoing switchgear, the opening and closing position of circuit breaker and whether the spring energy storage is completed are the most important monitoring circuits

there are many kinds of high-voltage circuit breakers at present, which can be divided into: oil circuit breaker (more oil circuit breaker, less oil circuit breaker), sulfur hexafluoride circuit breaker (SF6 circuit breaker), vacuum circuit breaker, compressed air circuit breaker, etc. At present, our company has the most vacuum circuit breakers and SF6 circuit breakers, and some substations in Longkou use GIS composite appliances. GIS switchgear combines circuit breakers, isolation switches and grounding switches, conventional TA and TV, and bus bars in a SF6 insulated sealed shell to realize the compactness of substations, but its manufacturing cost is high, and it is mostly used in substations with expensive land or limited space. According to the survey of the International University of electricity, SF6 circuit breakers and GIS will continue to be the mainstream of high-voltage circuit breaker equipment in the next one to two decades

in iec62063 standard, the definition of intelligent circuit breaker equipment is: circuit breaker and control equipment with high performance, equipped with electronic equipment, sensors and actuators, which not only has the basic functions of circuit breaker, but also has additional functions, especially in detection and diagnosis

the intelligent circuit breaker realizes electronic operation, changes mechanical energy into capacitor energy storage, and changes mechanical transmission into frequency converter, which is directly driven by the motor. The mechanical moving parts are reduced to one, and the reliability of the mechanical system is improved. The intelligent circuit breaker has a digital interface, which can transmit position information, status information, opening and closing commands through the network. The life and reliability of electronic circuits in the control circuit will become the key to the engineering application of intelligent circuit breaker technology

II. Working principle and mode of intelligent circuit breaker

intelligent circuit breaker uses microelectronics, computer technology and new sensors to establish a new circuit breaker secondary system. Its main feature is that the executive unit is composed of electric power technology and digital control device, which replaces the auxiliary switch and auxiliary relay of conventional mechanical structure. The new sensor cooperates with the digital control device to collect operating data independently, which can detect equipment defects and faults, and send an alarm signal before the defects become faults, so as to take measures to avoid accidents. The intelligent circuit breaker realizes electronic operation, changes mechanical energy storage into capacitive energy storage, and changes mechanical transmission into frequency converter, which is directly driven by motor, so the reliability of mechanical system is improved

at present, the intelligent circuit breaker has been developed accordingly. The circuit breaker with intelligent operation function introduces the intelligent control unit based on the existing circuit breaker, which is composed of three basic modules: data acquisition, intelligent identification and regulation device. The working principle is shown in Figure 1. The solid line in the figure is the relevant structure and correlation of existing circuit breakers and substations. The intelligent identification module is the core of the intelligent control unit. The microcomputer control system composed of microprocessors can automatically identify the electrical working state of the circuit breaker during operation according to the electrical information collected before operation and the operation signal sent by the main control room, determine the appropriate opening and closing motion characteristics according to the simulation analysis results of the circuit breaker, and send adjustment information to the actuator, Send the opening and closing signal after the adjustment is completed; The data acquisition module is mainly composed of new sensors, which provide the electrical data to the intelligent identification module in the form of digital signals at any time for processing and analysis; The actuator is composed of components that can receive quantitative control information and drive actuators, which are used to adjust the parameters of the operating mechanism in order to change the motion characteristics during each operation. In addition, display modules, communication modules and various detection modules can be added as needed to expand the intelligent function of the intelligent operation circuit breaker

Figure 1 working principle of intelligent circuit breaker

the basic working mode of intelligent circuit breaker is to automatically select the preset working conditions of the operating mechanism and arc extinguishing chamber according to the monitored different fault currents, such as opening at a lower speed when the normal operating current is small, and opening at a higher speed when the system short-circuit current is large, so as to obtain the best opening effect in electrical and mechanical performance

this kind of intelligent operation requires the circuit breaker to have the controllability of mechanism action time. At present, the pneumatic operating mechanism, hydraulic operating mechanism and spring operating mechanism commonly used in circuit breakers have large discreteness of control time due to factors such as intermediate conversion medium, and their motion characteristics are difficult to achieve the desired controllable state. The circuit breaker with electromagnetic operation mechanism uses technologies such as capacitor energy storage, permanent magnet holding, electromagnetic drive, electronic energy environment development strategy formulation and control. When the mechanism is determined, there is only one moving part, there is no intermediate conversion medium, and the opening and closing characteristics are only related to coil parameters. Microsecond control can be realized through microelectronics technology, and the intelligent operation of the circuit breaker can be realized through speed characteristic control

the working process of intelligent operation circuit breaker is: when the system fails, the relay protection device sends the opening signal or the operator sends the operation signal, first start the intelligent identification module to work, judge the current working conditions of the circuit breaker, send different quantitative control information to the regulating device, and automatically adjust the parameters of the operating mechanism to obtain the motion characteristics suitable for the current system working state, Then make the circuit breaker act

III. advantages of intelligent circuit breaker technology

compared with traditional circuit breakers, intelligent circuit breakers have their own advantages:

1. After adopting intelligent circuit breaker technology, for non fault operation, the circuit breakers can be disconnected at a lower speed, reducing the impact and mechanical wear when the circuit breaker is disconnected, so as to improve the service life of the circuit breaker and achieve better economic and social benefits in engineering

2. Intelligent functions such as detection, protection, control and communication of high-voltage switchgear can be realized by using intelligent circuit breaker technology

3. The traditional reclosing adopts reclosing relay. During normal operation, the capacitor of reclosing relay is charged. When the fault circuit breaker is disconnected, the capacitor discharges instantaneously to achieve the purpose of reclosing. When reclosing in fault, because the capacitor is not recharged, reclosing can only be carried out once. After adopting intelligent circuit breaker technology, it is possible to change the current working mode of tentative automatic reclosing and realize adaptive automatic reclosing, that is, after the short-circuit fault is broken, if the fault still exists, reclosing will be rejected, and reclosing will be carried out only after the fault disappears. After adopting intelligent technology, the disadvantage that traditional reclosing can only reclose once will be avoided

4. Realize phasing closing, reduce closing operation overvoltage, cancel closing resistance, and further improve reliability; We are optimistic about the future growth by realizing phase selection and opening and controlling the actual arcing time, so that the arcing time of the circuit breaker is controlled at the phase angle that is most conducive to arcing, which is not limited by the requirements of the system arcing time difference, so as to improve the actual breaking capacity of the circuit breaker

with the rapid development of microcomputer technology, microelectronics technology, computer network and digital communication technology, as well as the application of artificial intelligence technology in the field of product research and development and research, the energy circuit breaker will develop from a single closed device that simply uses microcomputer control to replace the traditional relay function to an electrical intelligent system with a complete theoretical system and multidisciplinary intersection, and become a power switchgear in the field of electrical engineering The new development direction of power system relay protection, industrial supply and distribution system and industrial control network technology

IV. technological progress of intelligent circuit breaker

intelligent circuit breaker has integrated the functions of measurement, control and communication, making it possible to modularize and systematize power equipment. With the continuous development of microcontroller technology

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