Nterface test device with low power switch

An interface test device for testing a high voltage circuit of a high power transformer, the interface test device comprising:

• a low power instrument transformer powered by the high voltage circuit and including a capacitive voltage divider, and a Rogowski coil;
• a low voltage monitoring circuit provided with signals from the low power instrument transformer;
• a low power switch including a test block and a test plug insertable into the test block, the test block including at least one pair of contacts biased towards each other that are electrically connected and in line with the low voltage monitoring circuit configured to open and close the low voltage monitoring circuit provided with signals from the low power instrument transformer;
• and
• a test circuit connected to the low voltage monitoring circuit before or substantially simultaneously with the low voltage monitoring circuit being opened by inserting the test plug into the test block,
• wherein the low power switch is configured to provide at least one output based upon at least one parameter of the low voltage monitoring circuit to the test circuit in order to measure the at least one parameter by an external tester connected to the test circuit.