1. Introduction China's power industry is full of vitality, which brings both unprecedented development opportunities and severe challenges to the high-voltage switchgear manufacturing industry. The high-voltage switchgear manufacturing industry must continuously innovate technologically and launch new generations of products to meet the ever-growing demands of the power market. Currently, high-voltage switches are showing good development momentum. However, as an important switching device in the power system, the operating status of high-voltage disconnecting switches directly affects the transmission, distribution, and safe and reliable operation of electrical energy. In recent years, with the increase in electricity load and the construction of new substations, various new structures and materials of electrical equipment have emerged one after another. High-voltage disconnecting switches have also diversified in function, structure, and application to adapt to the needs of different regions and different wiring methods. Although various models of disconnecting switches have the same purpose, their structures and applicable ranges are different, and the maintenance work of various disconnecting switches is also very different. With the widespread use of high-voltage switches, accidents involving high-voltage switches are also frequent, causing great losses to national production. Therefore, it is necessary to implement intelligent control of high-voltage switches to achieve intelligent control of high-voltage switches and monitoring of the power grid status. 2 Intelligent Switch Integrated Protection Device The intelligent switch integrated protection device is a new type of protection device specifically designed for explosion-proof high-voltage power distribution equipment in mines. It is suitable for power supply and transformation systems with ungrounded neutral points such as 3.3 kV, 6 kV, and 10 kV, and can replace various existing analog protectors and digital display protectors. Its core part adopts ultra-large-scale integrated circuit and virtual instrument technology, with good electrical stability; at the same time, it adopts special anti-interference measures, and its operation is accurate and reliable. The product has multiple protection functions such as good overload inverse time protection, overcurrent protection, phase loss protection and leakage current lockout protection, and each protection function has test simulation experiments and corresponding data display; in addition, it also has real-time communication function, can be connected to industrial control computer to realize remote data acquisition, and can accept remote network control and operation. The specific functions are as follows: (1) Short circuit protection. When a short circuit fault occurs in the high-voltage power grid, instantaneous overcurrent protection is implemented. The short circuit protection setting current value is adjustable in stages, and the short circuit instantaneous overcurrent action time is less than 0.1 s. At the same time, it also has a specific overcurrent direct protection function. In the case of a sudden severe short circuit in the power grid, the impact current is used to directly drive the protection relay to cut off the load, which greatly shortens the protection response time. (2) Overload protection. When the high-voltage power grid experiences intermittent or continuous overload, time-limit protection and inverse-time protection are implemented. Among them, the inverse-time overload protection starts when the load current reaches 1.1 times the overload current, and adopts inverse-time characteristic operation. The overload multiple is adjustable in 4 stages. They all use heat accumulation to achieve overload protection under intermittent overload conditions. When the load current is less than 1.0 times the setting current, the heat accumulation energy begins to dissipate. The error between the overload action time and the theoretical calculation value is less than ±5%. (3) Monitoring protection. Insulation monitoring protection is implemented for the shielded core wire and shielded ground wire of the double-shielded cable used on the load side of the power distribution device. An alarm is triggered when the limit is exceeded. The insulation monitoring protection function can be turned on and off through parameter settings. (4) Overvoltage protection. When the incoming voltage Uac of the power grid is greater than 110% to 130% of the rated voltage, the overvoltage protection will operate with an accuracy of ±15%. (5) Undervoltage protection. When the incoming voltage Uac of the power grid is less than 75% to 55% of the rated voltage, the undervoltage protection will operate with a delay of 0.1 to 300 seconds with an accuracy of ±5%. (6) Leakage protection. For single-phase grounding faults in the subordinate power grid, leakage protection can be performed using either zero-sequence current directional leakage protection or power directional leakage protection. An alarm will be issued when leakage occurs. (7) Phase imbalance protection. Phase imbalance protection can be performed on the three phases of the load. The operation delay range is selectable, and the phase imbalance function can be turned on or off as needed. (8) Coal mine gas over-limit protection. An external gas detection instrument can be connected. When the coal mine gas concentration exceeds the limit, after the gas detection instrument outputs its action, the power distribution device will perform a lockout to prevent closing or a refusal to open the circuit. (9) Audible and visual alarm output. When a fault occurs in the high-voltage power grid, it can send a signal to the audible and visual alarm system to trigger an alarm. (10) Remote communication function. It has a remote communication function, which can realize group control and can be remotely controlled, tested and adjusted from the ground. (11) Multiple intelligent memory functions. It has self-test function, interlock function, fault nature display function, etc., and can also remember and save the fault nature after tripping and power failure. 3 Integrated protection unit based on microcontroller and SJA1000T intelligent switch The hardware composition principle of the integrated protection system based on microcontroller and SJA1000T CAN bus is shown in Figure 1. It includes: microcontroller 89C51, analog signal conditioning circuit, A/D conversion circuit, serial E2PROM storage circuit, RAM and opto-isolation circuit, etc. The sampling of current and other waveforms is actually the conversion process of input continuous analog quantity to discrete sampled digital quantity, which is achieved here by sampling interrupt. External inputs to the microprocessor-based protection system, such as auxiliary contacts for switch and knife switch positions, and transceiver status contacts, are processed by opto-isolation technology in the input circuit before being sent to the central processing system. Outputs from the microprocessor-based protection system, such as trip commands and alarm messages, are processed by opto-isolation technology in the output circuit before the central processing system outputs its judgment. Opto-isolation technology effectively resists interference. The 89C51 microcontroller, acting as the central processing system, calculates, analyzes, processes, and judges various raw data input from the data acquisition system to complete various relay protection functions. The 89C51 microcontroller is the core of the microprocessor-based protection system. A simple and efficient data acquisition and processing system is constructed using a 40 MIPS embedded digital signal processor. An analog input converter is installed on the AC module to isolate and convert secondary AC voltage or current signals into small voltage signals, which are then adjusted and input to the A/D converter. The principle of the analog input device is shown in Figure 2. The voltage transformer (TV) is 120 V/5.66 V; the current transformer (TA) has a measuring TA of 6 A/3.53 V and a protection TA of 120 A/3.53 V, and the TAs are of the through-type. The selected isolation transformers are of high precision, have good isolation effect, and possess high immunity to disturbances. The zero-sequence transformer model is GLL-5, 1 A/0.097 V, manufactured by Baoding Sanhuan Electric Factory. 4. CAN bus and CAN232MB. CAN (Controller Area Network) is a type of fieldbus popular internationally. It is particularly suitable for building interconnected device network systems or subsystems. First proposed by Bosch in Germany, it is one of the most widely used fieldbuses internationally. CAN is a multi-master serial communication bus. Its basic design specifications require high bit rate, high immunity to electromagnetic interference, and the ability to detect any errors on the bus. CAN can still provide a data transmission rate of up to 50 kb/s when the signal transmission distance reaches 10 km. CAN (Controller Area Network) is a type of industrial fieldbus. Compared to general communication buses, CAN bus offers superior reliability, real-time performance, and flexibility in data communication. Due to its excellent performance and unique design, CAN bus is gaining increasing attention. Its application is most widespread in the automotive industry. World-renowned automakers such as Mercedes-Benz, BMW, Porsche, Rolls-Royce, and Jaguar all use CAN bus to achieve data communication between the vehicle's internal control system and various detection and actuator mechanisms. Furthermore, due to the inherent characteristics of CAN bus, its applications are no longer limited to the automotive industry but are expanding into fields such as automatic control, aerospace, marine, process industries, machinery, textile machinery, agricultural machinery, robotics, CNC machine tools, medical devices, and sensors. CAN has become an international standard and is widely recognized as one of the most promising fieldbuses. Typical application protocols include: SAE J1939/ISO11783, CANOpen, CANaerospace, DeviceNet, NMEA 2000, etc. According to the ISO11898 standard, to enhance the reliability of CAN-bus communication, terminating resistors (120 Ω) are typically added to both ends of the CAN-bus network, as shown in Figure 3. The size of the terminating resistor is determined by the characteristic impedance of the transmission cable. For example, if the characteristic impedance of the twisted pair cable is 120 Ω, then 120 Ω terminating resistors should also be integrated at both ends of the bus. The CAN232MB converter does not have an integrated 120 Ω terminating resistor (the terminating resistor is included). When the CAN232MB converter is used as a terminal device, the user can connect a 120 Ω terminating resistor between pin 7 ("Res+") and pin 8 ("Res+") of the CAN interface of the CAN232MB converter. The CAN232MB intelligent protocol converter uses Philips' SJA1000 CAN controller (16 MHz crystal oscillator) and PCA82C251 CAN transceiver to implement the CAN communication interface function, as shown in Figure 4. When the CAN232MB converter connects to the CAN bus, CANL connects to CANL and CANH connects to CANH. The CAN232MB converter has a built-in watchdog timer to ensure long-term reliability; it also has built-in non-volatile memory to save the user's last configured parameters. During normal operation, the CAN232MB converter monitors the CAN bus and RS 232/RS 485 bus in real time. Once data is detected on one side of the bus, it is immediately parsed, loaded into its respective buffer, processed according to the set operating mode, and converted before being sent to the other side of the bus, thus achieving data format conversion. In the CAN232MB converter, the CAN-bus communication circuit uses electrical isolation with an isolation voltage of DC 2500 V. The RS-232 communication interface uses a 3-wire connection (TXD, RXD, GND), and the RS-485 communication interface uses a 2-wire differential connection (A+, B-). 5. LabVIEW Programming The data processing software development platform is LabVIEW. LabVIEW's graphical programming interface greatly facilitates the creation of this data processing software. The functions of the data acquisition and processing system software are: real-time display of data transmitted back via serial port after conversion through CAN232MB, synchronous display of data acquisition waveforms, data processing, and providing turtle status indication signals. 6. System Testing The system software testing of the intelligent switch integrated protection device includes software testing and field operation testing. Software testing mainly uses a microcontroller to simulate data sent from CAN232MB to the serial port, and then uses software designed in LabVIEW to read the data. The performance of the tested software is good. The microcontroller's serial port data transmission program is as follows: The principle of the intelligent switch integrated protection device system field test is based on the fact that the zero-sequence voltage and zero-sequence current are both zero when the high-voltage power grid is working normally. Therefore, the power supply status of the power grid is judged by detecting the zero-sequence voltage and zero-sequence current of the high-voltage power grid. After the system connection is successful, the data is tested, and the operation is normal. The zero-sequence voltage data obtained from the database is as follows: From the above data, it can be seen that the zero-sequence voltage fluctuates within 0 to 10 V. Fluctuations within this range are acceptable. The final detected status is that the power grid power supply performance is good. The zero-sequence current data detected from the database is as follows: From the above data, it can be seen that the zero-sequence current is within 1 A. This is an acceptable phase imbalance for the high-voltage power grid. It can be considered as normal power supply. 7 Conclusion The intelligent switch integrated protection device realizes the status detection of the high-voltage power grid and the intelligent control of the switch through the data converted from CAN. After the network is formed, the system operation interface of the central control station needs to select and control the protected power distribution equipment. The protection mode of a certain high-voltage power distribution device can be selected by the central control station through interruption and filtering. In the interruption mode, each integrated protection device only protects its own switch when no control command is received. The collected data is not sent to the CAN bus. If the central station needs to obtain data from a protection device, it sends the corresponding control word. After the control word is sent to the CAN bus, the integrated protection device processes the received control word. If it requests data from the device itself, it sends the data required by the central station. If it is not a command to control the device itself, it discards the command. In the filtering mode, each integrated protection device collects data from its own protected switch, continuously monitoring and protecting it. The collected data is continuously forwarded to the CAN bus. The data is then transmitted to the central control station via CAN232MB. The central station filters the received data. If the received data contains parameters that need to be monitored for the switch, it is accepted; otherwise, it is discarded. The future development direction is to form a network-based high-voltage power distribution device protection network. This can not only be well applied in neutral ungrounded high and low voltage power distribution systems, but can also be widely used in other industrial control fields.