Overvoltage control during restoration

During the early stages of restoring high-voltage overhead and underground transmission lines, the authors discuss three related overvoltage areas: sustained power frequency overvoltages, switching transients, and harmonic resonances. During restoration certain line-transformer configurations when energized generate a combination of sustained, transient, and harmonic overvoltages which may cause surge arrester failures and thus system faults. or the subsequent flash-over and damage to equipment. The energy stored in long high-voltage lines is large causing significant transient or resonant overvoltages which must be carefully considered during restoration. With the help of analytical tools such as the electromagnetic transients program (EMTP) and those described it should be possible to establish general procedures and restoration guidelines to avoid overvoltages.<>