Preventive test: is the electric power system has not yet begun to run before it is full load or overload, to ensure that the actual operation of normal.
Mechanical test: tooth decay is some components of the power system is a mechanical structure, such as vacuum switch and so on, he has a mechanical movement structure in the inside, so it is also necessary to use the appropriate instrumentation for the test to ensure that the three-phase opening and closing speeds are the same and so on.