Research On Tower Grounding Resistance Measurement Device And Application By Injecting Multi-frequency Current

With the development of grid technology, tower grounding is getting more and more seriously as a main factor influencing the trip-out rate of transmission line, and ensuring the grounding resistance conform to the requirement is the premise of the power system in reliability. Thus, accurate and efficient measurement of transmission line tower grounding resistance has realistic engineering significance. Based on the original tower grounding resistance measurement, this paper proposed a new method of measuring the tower grounding resistance through the injection of a multi-frequency current, which overcomes certain problems such as low efficiency, low accuracy and poor applicability,and a measuring system was developed. The main works are as follows:①This paper constructed a model of transmission line with grounding protection on basis of field investigation. A new tower grounding resistance measurement without disconnecting grounding wire was put forward through the analysis of the existing measurement considering grounding wire and inductive effect of grounding connector. Based on the model, the condition for the accurate measurement of grounding resistance was established, the frequency range of the injected current determined and the processing of measured data was proposed. In addition, the proposed multi-pole method measurement shortened the distance of electrode arrangement and expanded the applicability of the measurement method and system.②The equivalent model of tower grounding measurement without disconnecting grounding wire was built based on Multisim software for different influencing factor as number of towers, grounding wire inductance,tower resistance and inductance to prove the validity of this method.③In view of the measurement requirement, a hardware measurement system was constructed on basis of the method including variable frequency excitation source, signal collection module, display module and USB storage module. Finally, system software code was developed on MPLAB software and system was debugged to assemble and test the measurement device based on the system control.④Confirmatory experiment in a laboratory and field test of tower grounding resistance measurement were completed by the measurement system. Based on the simulated transmission line formed by power resistor and power inductor, this paper verified the practicability of the method and the system under laboratory conditions, analyzed the influencing factors to tower grounding resistance measurement without disconnecting grounding connector through electrolytic experiment, and comparative analysis was done with help of clamp-on method and digital grounding resistance measurement instrument.the results fully showed the superiority and effectiveness of the proposed method and the measurement system.