In energy distribution systems there is an extreme danger of fault in electrical and electronical systems (electrical equipment, computers, telephone lines, alarm systems etc.), caused by harmonics, needed by voltage changes and involved into process thyristor trigger devices (AC/DC Speed Control devices, Softstarters, UPS etc.) and all kinds of welding machines. These harmonics are current and voltage of electrical energy systems, arising in multiple frequency from basic frequency by non-linear power connections.