471 / 2022-03-15 23:57:05

Experimental Investigation of the Lightning Impulse Flashover of a Typical MV Overhead Line Insulator

lightning impluse,medium voltage insulators,flashover

Purpose/Aim

Lightning impulse flashover characteristics of a typical 24 kV pin–type porcelain insulator are experimentally investigated aiming at a better understanding of the flashover mechanism.

Experimental/Modeling methods

Positive and negative standard lightning impulses were applied to the insulator by using a Marx generator, 1MV/7kJ. Flashover probability distributions were obtained through the multiple levels test method according to IEC. The insulator was overstressed so as to investigate flashover characteristics as affected by the applied peak voltage. Probability distributions of flashover time, voltage and current were obtained and the associated charge and energy were computed.

Results/discussion

At relatively high overvoltage values flashover occurs sooner under negative than positive polarity impulses (Fig. 1) and through a higher discharge current and conductivity (Fig. 2). There is a critical overvoltage value, lower for negative than positive impulses, above which the discharge conductance increases markedly with applied voltage.

Conclusions

Probability distributions of the salient flashover characteristics of a typical 24 kV pin–type porcelain insulator stressed by standard lightning impulses of both polarities have been experimentally investigated and discussed.