Design Of On-line Monitoring System For Transformer Core Grounding Current Based On STM32

The power transformer is responsible for the transmission of electric energy and the transformation of electric power in the entire power system,occupying an irreplaceable role.At present,the traditional method of manual periodic detection has been used to monitor the grounding current of the transformer core,which is inefficient and not conducive to the further improvement of the safety of the entire power system,so it is of practical significance to propose a new monitoring method.The purpose of this article is to change the traditional monitoring method of core grounding current,uphold the concept of intelligent development of power system,and strive to design a transformer core grounding online monitoring system based on STM32 without changing the original structure of the transformer.The structure of the monitoring device can be divided into two parts: upper computer and lower computer.The lower computer selects STM32F103 as the core control chip,collects the current value of the ground wire drawn from the transformer bushing through the current transformer,and then judges the current value,and performs gear switching to make the signal size meet the needs of the acquisition and conversion chip.When the system determines that the current has exceeded the specified threshold,it will initiate a fault protection action and store the fault value and the corresponding fault time.The communication module selects Modbus-RTU protocol based on RS485,with CRC check,so that the data can be sent and received reliably.The entire lower computer software code is combined with uCos-II embedded real-time operating system to complete the coordination between different tasks.The host computer part is an important window for human-computer interaction.I chose a configuration software with a database to complete the real-time data reception display and historical data recording.This article makes a comprehensive theoretical analysis of the monitoring system and summarizes three key technical points: different from the measurement of conventional alternating current,because the current value of the iron core will be from mA in two states of single-point grounding and multi-point grounding accidents The level is changed to the ampere level,the change range is wide,and the acquisition is difficult.Compared with the previous several acquisition schemes,a programmable operational amplifier is directly used to complete the measurement process;the working environment of the device requires it to have high anti-interference,and is designed on hardware The second-order low-pass filter and the isolation of important interfaces through components.The software uses median value average filtering method,root mean square value method and other comprehensive filtering and measurement algorithms to complete the elimination of singular values;in order to improve the accuracy of the data Performance,the calibration is approached by bins and completed using a combination of fitting formula and manual calibration.The device also improves the way that the single sensor monitors the grounding current of the iron core in the past,and adding the monitoring of the grounding current of the clamp helps to determine the fault point.Finally,test the function for performance and overall operation of the system.In the performance test,the filter cut-off frequency and the filtering effect are verified,and the anti-interference of the power module is tested with the EFT group pulse tester.The overall test is through control.The single-variable method enables the system to complete bottom-up tests in environments with different temperatures and different currents.Analyze the test results and error values,and further improve the system so that the system can meet the normal online monitoring of the transformer grounding current and reduce the impact of the transformer core multi-point grounding fault on the power system.