High Pollution Conditions Research Articles

DC flashover performance and effect of sheds configuration on polluted and ice–covered composite insulators at low atmospheric pressure

How to choose external insulation under high altitude, pollution and icing conditions for UHVDC transmission project is a complicated problem. To provide technical reference to this engineering roadblock, the dc icing flashover performance of seven types of pre-polluted short samples of composite insulators at low air pressure simulated by the multifunction artificial climate chamber was researched in this paper. The influences of ice thickness, pollution and air pressure on icing flashover performance were analyzed. The correct formula of dc icing flashover gradient of seven types of pre-polluted specimens at high altitude was presented. The influence of the sheds configuration parameters on the flashover gradient was discussed. And the selection of sheds configuration was suggested.

Leakage Current Phenomenon on Ceramics and Epoxy Resin as 20 kV Outdoor Insulator at Tropical Environment

This paper explains the research results of leakage current, hydrophobicity and flashover voltage comparison on ceramics and epoxy resin 20 kV outdoor insulator in a chamber at tropical climate conditions. The waveform of leakage current (LC) was measured using a digital oscilloscope. The digital data was transferred to a personal computer using a RS-232 cable. The digital data was analyzed using Fast Fourier Transform. The result showed that LC was affected by various environment conditions like temperature, humidity and pollution. LC of ceramics insulator was higher than epoxy resin insulator in low temperature, high humidity and high pollution condition.

Stability of alternating current discharges between water drops on insulation surfaces

Discharges between water drops are important in the ageing of hydrophobic outdoor insulators. They may also be important in the processes leading up to flashover of these insulators in high pollution conditions. This paper considers discharges between drops when a limited alternating current is available, as experienced by an ageing insulator in service. A phenomenon is identified in which the length of a discharge between two drops is reduced through a particular type of distortion of the drops. This is visually characterized as a liquid protrusion from each of a pair of water drops along the insulator surface. This process is distinct from vibration of the drops, general distortion of their shape and the very fast emission of jet streams seen in very high fields. The process depends upon the discharge current, the resistivity of the moisture and the hydrophobicity of the insulation surface.

Enzyme activities as biomarkers of freshwater pollution: Responses of fish branchial (Na+K)-ATPase and liver transaminases

The water toxicity of the Reconquista river, an urban and industrial polluted watercourse was tested. Surface water samples from two points up and downstream of low and high pollution conditions were assayed. Continuous-flow renewal bioassays under controlled laboratory conditions were run for 21 days. Alterations in the activity of enzymes involved in ion balance and hepatic metabolism were determined in juvenile carp Cyprinus carpio used as test species. Branchial (Na+K)-ATPase and hepatic glutamic oxalacetate transaminase (GOT) and glutamic pyruvate transaminase activities were the selected biomarkers of toxicity. Sublethal Cd solutions were used as a reference toxic. Results showed that the activity of the enzymes were affected according to the deterioration of the river water quality. Branchial (Na+K)-ATPase and liver GOT activity results were reliable indicators to discriminate river water samples of dissimilar pollution state. ©1999 John Wiley & Sons, Inc. Environ Toxicol 14: 313–319, 1999