Distribution of Ground Fault Currents Along Transmission Lines -- An Improved Algorithm
The calculation of fault current distribution between ground wires and ground is important for the operation of modern power systems. A new method is presented based on an approach whereby the current distribution is solved through the computation of driving-point impedances. The method is applied to three phase systems with mutual couplings between conductors (phase and ground, respectively) included. Currents computed by this method and methods published in recent literature are compared and are found in good agreement. Results show that the method is more efficient in terms of CPU time and memory space.
Analysis of Transmission Tower Potentials During Ground Faults
Since ground fault currents in high-voltage systems are on the increase, the hazards associated with transmission tower voltages during ground faults have become of concern. An analytical method is presented to determine these voltages for long and short lines, arbitrary ground network terminations, and any combination of skywires and counterpoise conductors. The proportion in which the fault current is supplied by the line on both sides of the fault location is taken into account, and the effect of fault currents flowing in parallel external circuits is also considered. The touch and step potentials at the faulted tower are determined and an assessment is given of the hazard they may represent. In a numerical example, several measures aimed at reducing this hazard are compared.
UV-B radiometry and dosimetry for solar measurements.
Biologically effective irradiance or dose of solar UV radiation was determined using a spectroradiometer, two broadband radiometers and two types of passive UV-dosimeters. The absolute erythema irradiance and the actinic irradiance were calculated from the solar spectrum measured with the spectroradiometer. It was demonstrated that the erythema irradiance is proportional to the actinic irradiance of solar radiation. The erythema irradiance was also determined using the two broadband radiometers which utilize a filter transmitting erythema spectra. Personal UV-dosimeters such as polysulphone and CR-39 were used to determine the erythema dose for a selected period of time. These results were used to estimate the accuracy of the broadband radiometers and UV-dosimeters. It was found that the results obtained from the broadband radiometers deviate from the absolute erythema irradiance by less than 20% during clear days between the hours of 11:00 and 13:00 Eastern Standard Time (EST) in Australia. The assessment of the erythema dose using passive dosimeters such as polysulphone and CR-39 could introduce an error as high as 40% if the calibration was not performed before undertaking experimental measurements.