Bushing Tests

The value of power-factor tests on bushings at higher voltages has been demonstrated. Tests at low voltages, while valuable, are inadequate. The power-factor and capacitance vs. voltage characteristics at voltages up to or above the operating voltage are important in judging the condition of the insulation. The nature of bushing deterioration and the significance of high power factor have been shown by laboratory examinations. The findings help to establish a basis for power-factor limits, and for improvements in design and maintenance.