Perpustakaan Digital ITB

Overhead transmission or distribution lines are widely used in the present power system to transmit electric energy from generation stations to customer points. Their performances strongly depend on the insulation system. Outdoor insulators, as part of transmission or distribution lines, experience various stresses, such as electrical, mechanical and environmental stresses. Besides experiencing those stresses, some kinds of insulators may have different endurances to them. Thus, there are many aspects which influence the insulator performances. These aspects should be investigated and/or quantified in terms of the influence on the insulator performance. This doctoral research was conducted mainly to investigate the performance of porcelain and epoxy resin insulator samples installed at Pangandaran substation, near the coast, and at Kamojang substation, near the geothermal power plant. A coastal area is one kind of severely polluted area. In contrast, a geothermal area creates emission of chemical materials. As scientifically hypothesized, those materials, at a certain level, might reduce outdoor insulator performance. Therefore, it is important to carry out a research concerning outdoor insulator performance related to coastal and geothermal areas, with more than one kind of insulator samples and by developing new methods. This research is the measurements of leakage currents from each new-clean up to eight polluted identical 20 kV porcelain and epoxy resin insulators. The polluted insulators were installed at Pangandaran substation, around 500 m from the Southern Sea, on December 15th, 2006, and at Kamojang substation, around 1447m above sea level, on December 14th, 2006. These insulators were taken gradually in the period of 3 to 4 months to be tested in a hermetically sealed chamber, for leakage current measurements, on various temperatures, humidity, pressures and applied voltage amplitudes simultaneously. The leakage current and applied voltage waveform measurements used a two-channel storage digital oscilloscope. The data were recorded and transferred to a computer using USB, and saved in softcopy forms. The leakage current waveforms were analyzed by using fast Fourier transform, so that the frequency spectra and total harmonic distortion could be obtained. The relations among parameters were analyzed by using multivariate statistical tools, namely correlation coefficient, principal component and canonical correlation analyses. The tests were done on SEM, EDAX, deposited pollutant solution, hydrophobic conditions and some supporting researches, such as on-site leakage current, artificially polluted, discharge current measurements and computer simulation. Generally, the results indicate that the porcelain insulators are more susceptible to environmental conditions than the epoxy resin ones. The influences of coastal contamination are greater than those of geothermal emission. These cases are indicated by either the individual correlations or statistical computations. The ratios of porcelain insulator impedance at Pangandaran substation on the high and low humidity range between 0.46 and 0.03. On the high humidity (99% RH), the minimum phase angles of porcelain insulator leakage currents range between 58.8 and 7.2 degrees, and the minimum THDs range between 14.9% and 4.9%, whereas the ratios of the epoxy resin insulator impedances on the high and low humidity range between 0.85 and 0.57. On the high humidity, the leakage current phase angles range between 73.6 and 58.1 degrees, and the minimum THDs range between 20.7% and 8.8%. At Kamojang substation, the ratios of the porcelain insulator impedances on the high and low humidity range between 0.87 and 0.13. On the high humidity, the leakage current phase angles range between 66.8 and 25.7 degrees, and the minimum THDs range between 12.4% and 7.8%. The ratios of the epoxy resin insulator impedances on the high and low humidity range between 0.98 and 0.64. On the high humidity, the minimum leakage current phase angles range between 90 and 57.4 degrees. Finally, the minimum THDs range between 22.4% and 14.1%. The scatter plots of canonical correlation analyses on the epoxy resin insulators are usually more dispersed than that of the porcelain insulators at each substation. The averages correlation coefficients of the humidity on the THD, phase angle and the leakage current amplitude were -0.5613,-0.5150 and 0.4150 for the coastal polluted porcelain insulators respectively. The input parameter influence on the leakage current parameters for the coastal and geothermal polluted porcelain insulators were 0.9568 and 0.9262 of canonical correlations respectively. The surface of the epoxy resin insulator specimen was more degraded than that of the porcelain one at the same substations and on the same withdrawals. The epoxy resin specimens at Pangandaran substation are more significantly degraded than that of at Kamojang substation. The average contact angle reductions of the epoxy resin specimens at Pangandaran and Kamojang substations were 0.12 and 0.08 degrees/day respectively. The significant chemical elements of pollutants from the coastal area were Cl, Ca and Na, and that from the geothermal area was sulphur.