Determination of the karma wire temperature coefficient used in the high voltage arm of impulse divider

The resistance value of impulse high voltage arm should not be too large in order to achieve good dynamic performance. When impulse high voltage applies on the divider, the high current will flow through the high voltage arm resulting in karma wire interturn bearing large electrical forces. Therefore, it is necessary to closely winding the resistor wires around the skeleton, but it will affect the temperature coefficient of karma. Two dominant factors which affect the temperature coefficient are demonstrated. One is the thermal expansion coefficient of skeleton and the other is the bending strain caused by geometry structure of the skeleton.