Design and Study of Insulation Margin Test System for Direct-type Lead Exit of Ultra-high Voltage Transformer

An insulation margin test system for ultra-high voltage Direct-type lead exit is proposed, by using which the lead exit could be tested independently. The electric field calculation model including the lead exit and winding is established, and electric fields of those components within the test system is studied. Whilst, the electric field distributions of the lead exit installed in practical transformer or reactor are investigated. Of two cases, the electric fields and the insulation margin under operating of industrial voltage, lightning, switching, and long-time withstand are compared. The obtained calculated results verify the feasibility and reliability of the test system.