The following insulation tests are performed to meet the transformer insulation strength expectations.
Unless otherwise requested by the customer, the following tests are performed in the following order (IEC 60076-3) :
Switching impulse test: to confirm the insulation of the transformer terminals and windings to the earthed parts and other windings, and to confirm the insulation strength in the windings and through the windings.
Lightning impulse test: to confirm the transformer insulation strength in case of lightning hitting the connection terminals
Separate source AC withstand voltage test: to confirm the insulation strength of the transformer line and neutral connection terminals and the connected windings to the earthed parts and other windings.
Induced AC voltage test ( short duration ACSD and long duration ACLD ): to confirm the insulation strength of the transformer connection terminals and the connected windings to the earthed parts and other windings, both between the phases and through the winding.
Partial discharge measurement: to confirm the "partial discharge below a determined level property of the transformer insulation structure under operating conditions.
In order to simulate the lightning impulse voltage applied on the transformer. Huayi electric power company makes the impulse voltage generator test system, which is mainly suitable for the impulse full wave withstand voltage test of 110kV and below high voltage equipment, and can also be used for the impulse test of other products. It adopts PLC technology and uses two-core optical fiber to transmit control commands and feedback equipment status, thereby avoiding electromagnetic interference and improving the safety of the control system and computer. The control function has manual, fully automatic, and program control functions, and the functions at each level are relatively independent to ensure the reliability of the system. It adopts the thyristor voltage regulation method and has a charging voltage feedback measurement system. The distance between the ignition ball gap and the intercepting ball gap can be adjusted manually or fully automatically and is displayed on the LCD panel.