| The performance of grounding grid is of great significance to the safety of substation power equipment and operators.Its function of diversion and voltage equalization is facing higher requirements because of the improvement of the scale,capacity and voltage level of power system in China.At present,the design of grounding grid in substations in China has basically met the power frequency characteristics,and the abnormal distribution of grounding resistance and ground potential caused by impulse current is more likely to be set up.Preparedness and personal safety pose a threat,so it is valuable to study the transient characteristics of grounding grid Impact and optimize them.Aiming at the safety requirement of substation grounding grid,the transient characteristics of substation grounding grid under high current impulse are studied on the real test site of substation grounding grid.The optimization method is proposed and applied to the actual substation grounding grid.The main work of this paper is as follows:Firstly,based on the design criterion of substation grounding grid,an experimental platform is built to study the transient characteristics of substation grounding grid impact.The layout of zero potential point,injection point and reflux point is determined,the shock wave generator is selected,and the test method and flow chart are designed.Secondly,a test platform for grounding grid impulse characteristics is built on the basis of a real test site,and a scheme for measuring transient characteristics parameters of substation grounding grid is proposed,including the measurement methods of impulse impedance distribution of substation grounding grid,ground potential(difference)distribution of grounding grid under lightning impulse and impulse current dispersion distribution of grounding grid,and an optimization method for encrypted conductor of grounding grid is proposed.The transient characteristics of the dense grounding grid are tested and the optimization method is verified.Finally,aiming at the requirement of transient characteristic research for 110 kV substation expansion in new area,the parameters of impulse impedance distribution of substation grounding grid,ground potential(difference)distribution of grounding grid under lightning impulse and impulse current dispersion distribution of grounding grid under lightning impulse are tested,and the transient characteristic measurement method of substation proposed in this paper is applied.The work of this paper can provide useful reference for checking the existing grounding grid design scheme and improving the existing protective measures of substation. |
