Research On The System And Corrosion Of Grounding Resistance Reduction To Grounding Grids By Electrochemical Measurement Methods

The grounding grids play an important role in transformer substation which canreduce resistance. However,in areas of high soil resistivity, the effect of grounding gridshas been weakened.In order to avoid consuming a lot of steel, people developedgrounding resistance reduction. They have good electrical conductivity, diffusion,osmosis, adsorption which can increase the flow area, and complete the goals to reduceground resistance.But most of them would cause a certain degree of corrosion togrounding systems, and then bring serious hidden danger to the substation and security ofpeople. Electric power industry standard roles all kinds of performance about thegrounding resistance reduction, and the corrosion rate is stipulated less than0.03mm/a.In this paper, the electrochemical method, the inductance probe methodand theweightlessness method would be used to verify the accuracy of the measurementresults.Most of all, a better method would be selected.The weightlessness method is a standard, but the sixty days operating time andcomplicated operation process is uncomfortable.The electrochemical method is fast andsensitive. Especially polarization resistance method is the key point of thisresearch.Inductive probe can determine trends and magnitude of corrosion through signalchanges. It can observation data online and calculate the corrosion processto achievetimely processing of data.The topic selected six kinds of physical grounding resistancereduction.Different originsanddifferent prices endow them broadly representative.Bycomparing three measurement methods, the results are as follows. The electrochemicalmethod is sensitive and accuratewhich can replace the traditional weight loss method.Theinductive probe method has poor sensitivity and precision, therefore the way is failure.Based on the experiment above, some practical experience about the corrosive ofgrounding resistance reduction byelectrochemical measurements has been summarized. It can be used for field measurements.(1) Electrochemical measurements time should be guaranteedmore than two days.At the end of the measurement time,the corrosion rate valuesare representative.(2) Measurement time can be relied upon open circuit. If open circuit stabilizequickly, the measuring time can be shorten.(3) The electrochemical methodis accurate and reliable. When the measurementsare less than0.03mm/a, the corrosion characteristics of the grounding resistancereduction have reached standard. When the measurements are more than0.05mm/a, thecorrosion characteristics of the grounding resistance reduction have not up to standard.