Development of Traction Substation Simulation Panel Based on AT89C52

1. Introduction

According to the railway technical regulations of the Ministry of Railways, traction substations and power distribution stations should be equipped with simulation screens. Simulation screens are essential equipment for substations and play an important role in the manual inversion gate operation, maintenance, and safe operation of substations. At present, most of the substation simulation screens on the road are simple simulations or have no light indication. Even the more advanced simulation screens have a key locking function, but due to unreliable performance, the key often fails to pop out; there is no automatic function and it cannot truly reflect the disconnection and closing status of the disconnector and circuit breaker; the human-machine interface is not friendly, and a large amount of coding needs to be memorized. There is no display interface and the operation is inconvenient. Therefore, it is necessary to develop an intelligent simulation screen with advanced technology to meet the actual needs of the site with as little one-time investment as possible. This article introduces a traction substation intelligent simulation screen developed for the Xikang Line.

2. Working principle and hardware circuit

The switch automatic display signal of the simulation screen is collected from the actual status of the circuit breaker and disconnector in the substation, and photoelectric isolation technology is used to enhance the interference introduced by the simulation screen from the indoor and outdoor signals of the substation. The single-chip control adopts a three-bus control (DB, AB, CB) structure. The 25-pin bus output and the 89C52 connection interface are: P0 port as the address line 8 bits; P1 port as the data output line 8 bits; P2 port as the input line 8 bits; plus a ground wire, these lines are driven and output through the 74HC245 bus.

The T1 interrupt port of the AT89C52 single-chip computer is used as an external keyboard input. The human-machine interface part uses the ZLG7289 keyboard intelligent control chip, which has a serial interface and can drive 8-bit LED digital tubes at the same time. It can also connect up to 64-key keyboard matrices, and can complete all the functions of LED display and keyboard interface. The RXD and TXD of the P3 port are connected to the communication MAX232 chip, providing a reserved RS-232 serial interface, which can be easily connected to the local area network or connected to the telephone line through a MODEM, so as to upload the information of the substation to the section production dispatch, so that the dispatcher can immediately understand the switch information of the substation. In addition, the PC panel used in the intelligent simulation screen of the traction substation is a new process, which is applied to the panels of microcomputer protection devices, intelligent instruments and other equipment. The panel adopts the photolithography technology and screen printing technology of printed circuit boards, prints the main wiring of the substation and its graphic symbols on the reverse side of the PC mask, and hides the key switches, signal lights and circuits behind the PC mask or in its interlayer, so as to achieve both beautiful and not easy to fade and durable.

The intelligent simulation screen of the traction substation adopts AT89C52 single-chip microcomputer control and monitoring, and has good human-machine interface and communication functions. The developed simulation screen can automatically and truly reflect the opening and closing status of all disconnectors and circuit breakers in the traction substation, and provide a complete switch status information for the substation duty personnel, which is both intuitive and real. At the same time, the simulation screen has two simulation operation modes: single operation and switching operation, and also has voice alarm and prompt. In the two simulation operation modes of single operation and switching operation, the circuit breaker and disconnector of the substation can be operated separately or simulated switching operation on the simulation screen through the keyboard and LED display on the simulation screen. In these two operation modes, the key can be locked and ejected. When the switching operation is correct, the corresponding circuit breaker or disconnector corresponding unlocking key is ejected and there is a voice prompt. If the switching operation is wrong, the corresponding circuit breaker or disconnector corresponding unlocking key is locked and there is a voice alarm. It can effectively train the substation duty personnel to switch, examine their proficiency in the switching sequence, effectively prevent the substation duty personnel from making mistakes, and play an important role in reducing mistakes and preventing accidents. The software structure diagram is shown in Figure 1.

Figure 1 Main program flowchart of simulated screen switching operation

3. Reliability measures

The technical difficulty of this device lies in solving the anti-interference ability in the process of information transmission and the recovery of the AT89C52 microcontroller crash under abnormal conditions. In order to solve these problems and improve the reliability of the device, we adopt the following measures:

1). High reliability TLP521-4 optocoupler is used in both the automatic control circuit of the device and the AT89C52 single chip microcomputer control drive circuit to electrically isolate the input circuit from the output circuit, thus improving the reliability and anti-interference ability of the device.

2). In order to overcome the freeze of the MCU in the strong electromagnetic interference environment of the substation and under abnormal circumstances and ensure the reliable operation of the MCU, the analog screen MCU main control circuit adopts the popular self-recovery technology today. The hardware watchdog X25043/5 device is used on the AT89C52 MCU main control circuit motherboard. The device monitors the operation of the MCU all the time. Once the MCU system runs normally, the device automatically restores the MCU to run, so that the AT89C52 MCU can work reliably.

3). In order to detect whether the signal lights on the analog screen are working reliably and whether the driving circuit is working normally, self-test technology is adopted. When the microcontroller is powered on, all the signal indicator lights on the analog screen are first set to red, and then set to green in turn, so as to achieve the purpose of self-testing the signal indicator lights on the analog screen.

4. The intelligent simulation screen of traction substation has the following functions:

1). It can automatically and truly reflect the opening and closing status and operation mode of all disconnectors and circuit breakers in the traction substation, and provide a complete switch status information for the duty personnel and managers of the substation, which is both intuitive and true.

2). Flexible operation, with two simulation operation modes: single operation and switching operation. ① In single operation mode, each circuit breaker and disconnector on the simulation screen can be opened and closed separately; when the operation is correct, the corresponding unlocking key of the circuit breaker or disconnector will pop up with a voice prompt; if the operation is wrong, the corresponding unlocking key of the circuit breaker or disconnector will be locked with a voice prompt.

②. In the switching operation mode, each circuit breaker and disconnector on the simulation screen can be opened and closed according to the switching operation procedure; when the switching operation is correct, the corresponding unlocking key of the circuit breaker or disconnector will pop up with a voice prompt. If the switching operation is wrong, the corresponding unlocking key of the circuit breaker or disconnector will be locked with a voice prompt.

3). With voice alarm and prompt.

4). When the switch is not opened or closed normally, the operating key cannot be removed.

5). It has RS232 communication port, which can be connected to the local area network or the telephone line through MODEM at any time. The substation information can be uploaded to the section production dispatch so that the management personnel can understand the actual status of the substation equipment in time.

5. Conclusion

The intelligent simulation screen of the traction substation can intuitively display the actual operating status of the equipment, with flexible operation and reliable action, which greatly reduces the labor intensity of the operators, especially in the case of telecontrol. It can be applied to on-site actual teaching, reduce the cost of employee training, solve the contradiction between off-site training and safe production, prevent the misoperation of the substation duty personnel, and provide a good guarantee for the safe power supply of the railway. The equipment has been in operation for two years in the traction substations of the Xikang Line. It has reliable operation and full functions, and has received good feedback. It has passed the technical and product appraisal of the Railway Bureau and has been promoted and applied to the traction substations of the Xiangyu Line and Yang'an Line.

References

1. Xue Junyi, Zhang Yanbin, MCS-51/96 Series Single-Chip Microcomputers and Their Applications, Xi’an Jiaotong University Press, 1997.

2. Tan Xiubing, Liu Xiangyang, AC Electrified Railway Traction Power Supply System, Southwest Jiaotong University Press, 2001