Describe the process of testing the insulation resistance of a transformer winding and what the results indicate.

Testing the insulation resistance of a transformer winding is a crucial maintenance procedure to assess the condition of the winding insulation. The process involves using a megohmmeter, also known as a megger, which applies a high DC voltage to the winding and measures the resistance of the insulation. Before testing, the transformer is de-energized and isolated from the power source. All connections to the winding being tested are disconnected to prevent false readings. The megohmmeter is connected betwe....