Design And Implementation Of Smart Grid Fault Recorder

As part of the smart grid construction,the fault recorder integrates sensor technology,communication technology,data storage and processing technology.The real-time field-related data information when the fault occurrs recorded by fault recording system can be used to analyze the cause of the fault,locate where the fault occurred,etc.It is an important reference for handling the fault in time,reducing losses,improving the configuration and management of power grid,and avoiding similar incidents from happening again.This paper mainly solves the shortcomings of traditional recorder,such as complex design,concentrated system functions and heavy load,designing a new distributed recorder system with low power consumption and high synchronization accuracy.In addition,GPS and external crystal were used to generate high-precision clock to achieve synchronous acquisition of three-phase current.This paper mainly completed the following work:First of all,this article analyzed the performance requirements and technical focus of fault recorders according to the development status at home and abroad.For the disadvantages of traditional front-back mode microcomputer fault recorders,such as low reliability,difficulty in long-term operation,and high power consumption,ST Microelectronics' STM32L4 + series 32-bit microcontroller is selected as the system core to design a novel distributed,low-power,high-precision fault recorder system for the sampling and recording detection of the ground fault and short-circuit fault in smart grids.The system consists of 5 modular terminals,including a monitoring unit,a data collection unit and three acquisition units.The GPS,4G,and Lo Ra in each unit adopt a modular design to facilitate design,installation,replacement,and maintenance.In the hardware circuit design,the design work of low-power microcontroller(STM32L4R5ZIT6)peripheral circuits,power-taking circuits,data acquisition and storage circuits,Lo Ra and 4G communication circuits,GPS timing and interface circuits and LED fault indication circuits is completed.Among them,the acquisition unit and the collection unit have the same Lo Ra module which realizes the information interaction of fault event,line low voltage,module battery low voltage,and parameter modification.The cloud master server is used to receive real-time data from the acquisition unit and send control commands to collection unit.When the monitoring device finds that the zero-sequence voltage is abnormal,it may mean that a fault occurs in the distribution network.The monitoring unit will send a data call command to the cloud server,and then the server will call the recorded wave data of each acquisition node.This system can meet the needs of monitoring and judgment of the ground fault in distribution network with different neutral grounding methods.Furthermore,the synchronization requirement for all terminal equipment,especially the three-phase current acquisition unit in the analysis of power grid data is extremely high,but the synchronization performance of previous products is not ideal.According to the complementary characteristics of the accuracy of the global positioning system(GPS)and the crystal oscillator clock signal,the crystal oscillator signal is used as the MCU's clock source in this paper,and the GPS clock is used to calibrate the 1 Hz signal generated by the MCU timer to achieve a high-precision microsecond-level clock.The accurately synchronous sampling of the three-phase current in the distribution network was obtained by three acquisition units,and the synchronization error reaches the microsecond level.Thirdly,in terms of software functions,the overall functional flow of the fault recording system is realized,including the collection and storage of three-phase current and zero-sequence voltage,the call-up and upload of fault data and operating condition information,Lo Ra and 4G communication,fault indication using LED,GPS time calibration,and the low-voltage processing of super capacitor and battery.Finally,the system prototype debugging and functional test are completed,and the experimental results show that each module unit of the fault recorder system operates normally and reliably,the function implementation meets the design requirements,and the synchronization accuracy reaches the microsecond level.The fault indicator developed in this paper has the advantages of compact structure,strong environmental adaptability,low cost,low power consumption,high synchronization accuracy,etc.It has great practical significance for the safe operation of power systems.