Safe earthing design has a objective to assure that a person in the vicinity of earthed facilities is not exposed to the danger of critical electric shock which is caused by touch voltage or step voltage of human body. The current through the body and touch/step voltage depend on the contact resistance between the earth and the feet. In the substation，high resistivity material such as gravel is spread on the earth’s surface above the earthing grid to increase the contact resistance. This paper investigates the resistivity measurement method of silicon coated gravel，and proposes reduction measure of touch/step voltage by using the silicon coated gravel which is high resistivity material.
