Design Of Distributed Corrosion Detection Device Of Grounding Grids Based On Electric Network Theory

The grounding grid is buried in the underground soil,which is an important part of maintaining the safe and reliable operation of the power system and ensuring the safety of operators and electrical equipment.After burying for a period of time,the grounding grid will be corroded,making the grounding conductor thinner or even broken,affecting the safety of production.In order to prevent the safety accidents caused by the corrosion of the grounding grid,the methods of regular power outage and random excavation are generally adopted to monitor the operation status of the grounding grid.this method has the advantages of low efficiency,large engineering quantity and poor effect.Therefore,this paper proposes a distributed grounding grid corrosion detection device based on electrical network method,in order to detect the grounding grid without power outage and excavation.The structure of the grounding grid corrosion detection device is designed.The distributed measurement scheme is adopted,and the system consists of a host computer,a master computer and 16 slaves.The master and slaves and each slave use RS-485 communication.Each slave is connected to the ground lead,and the relays of any two slaves are gated to build a stimulus-response measurement port,which forms a fourterminal electrode method resistance measurement loop with the measurement line,which can eliminate the measurement line.Influenced by the small resistance value of the relay contact,the accurate resistance value of the port is obtained.By switching the strobe slaves,the system can build 120 measurement ports.The main and slave parts of the distributed grounding grid corrosion detection device are designed.The host consists of an excitation source module,a data acquisition module,a master control module and a 485 signal conversion circuit,and the slave consists of a 485 transceiver circuit,a relay and its drive circuit.The host MCU and the slave MCU communicate in a hand-in-hand manner through the RS-485 bus,and the slave MCU receives the command and drives the relay to act.When the device is running,the host selects the relay groups of the two slaves to form two loops,which collect the voltage and current signals of the ports respectively.The 16-channel slaves are powered by the same power supply through the bus cable.In order to reduce power consumption,the device uses a magnetic latching relay and designs a drive circuit.In order to reduce the influence of electromagnetic interference,the excitation source of the device adopts a 1Hz square wave signal,and a random error elimination algorithm based on residual threshold is designed to process the collected signal.The whole machine test of the designed distributed grounding grid corrosion detection device is carried out.The port resistance of self-made resistance grid and galvanized carbon steel grid is measured in the laboratory,the device runs stably,and the error of multiple measurements at the same port is less than 0.1mΩ.Comparing the mean value of multiple measurements at the same port with the results of Multisim simulation and high precision DC micro resistance tester,the measurement error of this device is less than 0.1mΩ.Laboratory tests verify the stability and accuracy of the device,which has application value.