The Security Research On Grounding Network Under The Action Of Impact

With the development of the power system, the grounding grid area of power plant andsubstation becomes larger increasingly and the structure is also more complex. As the highfrequency characteristics of lightning current and the inductance effects of ground grid, thereis a big difference between frequency current situation the lightning current in the process ofthe discharge in the ground. In many cases, even if the ground resistance meets therequirements of the grounding grid that there may also is dangerous potential differencebetween two points. The high potential difference would threaten the normal operation andthe safety of the staffs and the equipments. Meanwhile, as the automated substations arewidespread, large-scale and high-precision integrated modules made of microelectronicdevices are widely used in the power system controlling, protection and communication in thesecondary system, but the operating voltage are low of these devices, and currently theprotection of these devices have not yet get attention widely, the protective measures taken onthese devices are far enough, so the high potential difference of grounding grid between thetwo devices invades in these devices easily through counter attack, and make damage.In addition, there are many substation that have to built on open the mountains where thesoil resistivity is high because of the geographical conditions, their characteristics and otherreasons. On the one hand, the cost of the reduction in resistance in these areas is high,economically feasible; The other hand, even though spending a lot of manpower and materialresources to reduce the resistance, the results are often unsatisfactory, that is, the groundingresistance is still unable to meet the requirements.In summary, it is unreasonable to determine the safety of a ground grid only based thatthe ground resistance meets the requirements or not. On the foundation of analysising on theexisting national and international standards for the safety criterion of the grounding grid, thepaper analysis the impact parameters of the grounding grid: the grounding resistance, thepotential distribution on field area, the potential gradient, the maximum step and touchvoltages and the counter voltage of the secondary equipment, according to the three aspects ofcalculations, the actual site measurements and computer simulation based on EMTP-ATPsoftware, and assess the safety of the ground network. Finally, it proves that the method haspractical engineering significance for the safety assessment of grounding grid throughpractical the project...