Influence of Seasonal Factor on Seasonal Factor on Safety of Ground Surface High Resistivity Layer in Substations
SUN Wei-min HE Jin-liang;ZENG Rong,et,al
The permissible step and tonuch voltage of grounding system for human body in suhstatinos may be increased byincrease of surface soil resistivity, and the current through human body may be correspondingly reduced. However, seasonalfactor may affect the safety characteristic of high ground resistivity layer. causing the change of step and touch voltage. Thepermissible step and touch voltage calculated from DI/T621-1997 standard formula seens too high, higher than that byIEEE Std80-1997 standard recommended formula. When using high resistivity layer. the touch voltage will be lower duringrainy season, but during cold season, it will be higher than those without using high resistivity layer.Therefore,the effect ofseasonal factor on safety of grounding system shall be considerde.