is an international standard titled: "Power installations exceeding 1 kV AC and 1.5 kV DC – Part 1: AC."
Generation sites and individual site-based power stations. iec 61936-1 pdf
Perhaps the most frequently referenced section of the standard deals with clearances. High voltage electricity can arc through the air if a conductor is too close to a person or a grounded surface. IEC 61936-1 defines strict minimum distances based on the voltage level and the type of insulation coordination used. iec 61936-1 pdf