High-voltage cable plug (or socket) breakdown: high-voltage cable plug or socket breakdown, mostly due to plug and socket between the insulation filling time dry and damp; filling material contains impurities, or plugs, socket treatment is not clean; high-voltage plug, socket between the bubble, causing high-voltage breakdown. Because the liquid contains impurities, when added voltage, there is a leakage current through the interior, the current generated by the heat, so that the filling melts out of the heat, air into the gap between the plug socket, causing plug surface discharge breakdown.