Development of an Electrochemical In Situ Detection Sensor for Grounding Grid Corrosion

An electrochemical in situ detection sensor for grounding grid corrosion was developed. Because the auxiliary electrode used to polarize the working electrode was encapsulated into an insulation cavity (carbon steel), the polarization current was made to flow through the pinhole to the working electrode and the confinement function of the sensor was implemented. The potential-time curve (E-t curve) as a response to a galvanic step was measured with the sensor and the polarization resistance was obtained by E-t curve-fitting software. The impact of the sensor hole diameter and the insertion depth into the soil on the measurement area were studied by measuring the polarization resistances of the grounding grid. The investigation results show that the optimum sensor diameter is 5 mm, the insertion depth of the sensor has a small impact on the current confinement at a range of 12.5 cm, and the ratio of area measured with current confinement sensor to that measured with the traditional one is about 1/80. This sensor was successfully used to carry out corrosion detection for a substation grounding grid without excavating the grounding grid or stopping its operation.