Design Of Automatic Detection System And Research On Seasonal Coefficient Of Grounding Resistor

Grounding referred to as an important lightning protection measures in the modern building. Grounding seasonal coefficient is a significant indicator to judge the grounding level of buildings. But it was affected by the seasonal factor. There is a great significance reason how seasonal coefficient influence on grounding resistance. With the development of the modern electronic technology, develop the digital ground resistance meter and improve its test accuracy become a research hotspot for buildings lightning protection.This paper discussed the relationship between grounding resistance and building environments. Analysised the mechanism of the seasonal coefficient how influence on grounding resistance and pointed out the soil moisture, temperature, salinity, soil types, grounding structure and soil hierarchical structure influence on grounding resistance. Proposed that long-term grounding resistance measurement is the premise of seasonal coefficient study.In order to achieve the purpose of long-term grounding resistance measurement and solve the measurement data long-distance transfer problem. According to the principle of three-pole grounding resistance measurement and using MCLU design an automatic grounding resistance detection system with GPRS wireless data transmission function. The system consists of two parts. One is software another is data acquisition and transmission circuit. Data acquisition and transmission is mainly include the MCU the DDS constant current source, the AD sampling circuit, GPRS circuit and human-computer interaction circuit. The system uses pilot frequency method to select signal frequency and use automatic frequency conversion to eliminate the grounding grid power-line interference.Using Delphi7.0to design PC system software. The system mainly consists of the login window, the main interface and submenu. Using graph and tables to display grounding resistance data in the main interface and send a detection command after setting season coefficient. The submenu contains the entry properties of the grounding grid, system setting, report printing and data maintenance window. Using the Access database to storage system and ADO component to design database program in system. It using Indy10.0components to complete of network communication.Implant two common seasonal coefficient into the system to correct the grounding resistance. It can output data with report and Excel. This system has characteristics of remote automatic measuring grounding resistance. User can define seasonal coefficient base on local meteorological characteristics to correction grounding resistance measurement value. The measurement system is unmanned operation during overall process to avoid the operating error introduced.