In addition to protecting the safety of the person, the pressure transformer is used for machine maintenance, protection, mine protection and filtering. The isolation transformer, of course, is also not safe for the person, and in a low-pressure system, when any line of physical contact of a person does not form a circuit, it reduces the harm to the person. For high-voltage power systems, however, although neutral points in the isolation transformer are absent, because both the transformer or the generator have leaked electricity to the ground, they are in fact equivalent to passing through a large electrical barrier, although the current is small and does not affect the grid, but when a person approaches a high-voltage line, he or she forms a circuit between the body and the ground, causing a shock。