On-line Monitoring Device For Equipment Parameter At Neutral Point Of Distribution Network

With the intensive power grod charge,the intelligent development of power equipment.It poses a huge challenge to the safety of the power distribution system and the stability of the power supply.In the power distribution system,single-phase ground fault is the main fault of the distribution network,which will seriously damage the operating environment.In severe cases,an arc that is not easy to extinguish is generated,which is likely to cause fire.The effective online monitoring device can detect daults in time,and cooperate with related equipment to prevent the damage from further expansion,so as to ensure the stable and safe power supply for user in the power distribution system.First,this article introduces the background and significance of the topic seletion of the neutral point equipment parameter online monitoring device,and introduce the neutral point grounding method and the development process.It describes the mainstream grounding method of neutral point of the current power system int our country.Then,the relationship between the online monitoring device of neutral point equipment the parameters and the automatic tuning device of the arc suppression coil is introduced.At the same time,the development history of arc suppression coil and the tuning method of the arc suppression coil are introduced.Then the physical meaning of the parameters measured by the online monitoring device and the mathematical relationship between the parameters are explained.It also analyzes in detail the resonance method and the three-frequency method,which can only measure some parameters.Aiming at the shortcoming of the measurement method,an improved inter-frequency signal injection method is proposed.The corresponding equivalent circuit model is established,and the calculation formulas for all parameters are derived.Secondly,in order to verify the feasibility of the inter-frequency signal injection method,a neutal point device parameter online monitoring device id designed with STM32F407ZGT6 as the core for data processing and control,and Dwin LCD screen as the core of human-computer interaction.At the same time,the characteristics and selection of the main chips are briefly explained.In terms of hardware circuit design,this design follows a modular design method.First,the overall structure of the online monitoring device and the overall picture of the external measurement environment are introduced.Then the design and composition of the power supply board,main control board,sampling board,and switch-in board are introduced in sub-modules,and the specific hardware circuit design inside each board is given.In terms of sofeware,first introduced the development software platform and development process,and introduced the main control process of the online monitoring device in detail.Then,the program design of each communication module communicating with STM32F407,the design of the corresponding communication date frame structure and the introduction of the communication protocol are given.Finall,the data processing flow and the design flow of Dwin LCD screen UI interface ard given.Finally,through the establishment of a simulation test platform in the laboratory,a single test of various parameters of the neutral point is carried out,and the experimental data shows the online monitoring device.Within the allowable range of error,the monitoring of various data and the realization of data upload are basically completed.And localized preservation.The long and stable cycle test operation shows that the online monitoring device basically realizes online real-time monitoring.