DIELECTRIC STRENGTH OF OVERHEAD LINE INSULATORS UNDER OVERVOLTAGE CONDITIONS

An examination is made of the results of investigating long insulation strings of different types with various test impulse forms. Tests hav e been carried out on a single-circuit supporting insulation string, w ith its length varying from 4 to 8 m, with four types of cup-and-pin g lass units and long rod composite insulators. Tests have also been car ried out with a wide range of impulse forms, from lightning surges to switching overvoltages with long time fronts. The dependences of disch arge voltages on string length and impulse time to crest have been det ermined. Results of measurements of predischarge times are given.