Power Measurements at High Voltages and Low Power Factors

Abstract

A description is given of the apparatus for the measurement of power as low as a fraction of a watt at power factors approaching zero and voltages as high as 175 kv. to neutral. A standard make of portable wattmeter was used having maximum ranges of 1.5 watts, 37.5, 75 and 150 volts and 20 per cent power factor. To this wattmeter was adapted a three-megohm water column resistance multiplier. In the original form of the wattmeter the origins of certain errors, due to capacitances chiefly, were studied and methods for their elimination were subsequently determined. Integrity tests were developed by which the values of error powers were obtained and used as guides in making subsequent adjustments for the reduction of such errors to zero. These integrity tests were checked by using the wattmeter for the measurement of known amounts of power. Reconnaissance studies were made of the voltage-corona power loss relations for rope laid copper, 0.91-in., lock wire smooth copper, 0.91-in. and concentric strand aluminum, 1.006-in. diameter transmission line conductors in rain and fair weather at differing degrees of humidity, temperatures, and barometric pressures, from ``initial'' to ``full'' corona formation. This class of studies was extended to corona loss values as offered by a wide variation of the ``surface roughness'' of conductors subjected to high voltages. The losses for a single brush were measured and the shielding effect of groups of brushes was studied. Losses to single strings of insulators under different conditions were determined.