Non-soluble Deposit Density Research Articles

Study of AC Pollution Flashover Performance of Porcelain Insulators at High Altitude Sites of 2800 $\sim$ 4500 m

The external insulation of electric equipments will be affected by the atmospheric conditions in the high altitude regions. However, a few investigations at the high altitude sites of 3000 m and above have been conducted. This paper reports on the laboratory tests of artificially polluted cap-and-pin porcelain insulators performed at the high altitudes of 2800 m to 4500 m. The test results and analysis show that the pollution flashover voltages in high altitude regions are affected not only by the pollution grades but also by the atmospheric parameters. The exponent characterizing the influence of equivalent salt deposit density is 0.26 to 0.29 and the one characterizing the influence of nonsoluble deposit density is 0.09 to 0.15. The ac pollution flashover voltage <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> will decrease with the decrease of air pressure <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> and increase with the decrease of ambient temperature <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> . <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> is a power function of the ration of air pressure <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and also is a power function of the ambient temperature coefficient (1 + 0.02( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</i> - 20)). The average exponent characterizing the influence of air pressure is about 0.56 and the exponent characterizing the influence of ambient temperature is about 0.21 for the three types of insulators in the paper.

Study on AC pollution flashover performance of composite insulators at high altitude sites of 2800-4500 m

The newly constructed Qinghai-Tibet Railway connecting Golumd and Lhasa is the highest railway in the world, which is located on the hinterland of Qinghai- Tibet Plateau with the average altitude of above 4000 m. Therefore, the external insulation of electric equipments will be affected by the atmospheric conditions in the high altitude regions. In contrast to many test investigations in the artificial climate chamber, there are few ones at the high altitude sites of 3000 m and above. In the paper, the AC artificial pollution tests of four types of composite insulators are carried out at three high altitude sites of 2820 m, 3575 m and 4484 m along the Qinghai-Tibet Railway. The test results show that the AC pollution flashover voltages in high altitude regions are affected not only by the pollution grades but also by the atmospheric parameters. The pollution flashover voltages will decrease with the increase of air pressure but increase with the decreases of ambient temperature. The exponent characterizing the influence of equivalent salt deposit density is 0.26 to 0.32 and the exponent characterizing the influence of non-soluble deposit density is 0.12 to 0.16, the influence of non-soluble deposit density cannot be neglected. The exponent characterizing the influence of air pressure is 0.507 to 0.587. The exponent characterizing the influence of ambient temperature is about 0.20. Considering the combined influence of the air pressure and ambient temperature, the AC flashover voltage of the polluted composite insulators will decrease by 4.0% to 6.4% for the altitude increased per 1000 m.

Study on AC pollution flashover performance of cap-and-pin and rod insulators at high-altitude sites

The external insulation of electrical equipments is affected by the atmospheric parameters in high-altitude regions. However, there is a lack of studies conducted at the high-altitude sites of 3000 m and above worldwide so far, in contrast to many fruitful ones carried out in the artificial climate chamber. The authors investigate AC pollution flashover performance of cap-and-pin and rod insulators at high-altitude sites with a view to bridging the gap and enriching our understanding in the aspect. The AC artificial pollution tests are conducted at three high-altitude sites of 2820, 3575 and 4484 m, respectively. The results show that the exponents characterising the influence of salt deposit density, non-soluble deposit density and air pressure are 0.297–0.352, 0.122–0.142, 0.535–0.580, respectively; ambient temperature has an obvious effect on the pollution flashover voltages; there is no obvious relation between the insulator profiles and the influence exponents of salt deposit density, non-soluble deposit density, air pressure or ambient temperature.

Insulator Leakage Distance Dimensioning in Areas of Winter Contamination using Cold-fog Test Results

Electrical utilities have adapted insulator leakage distances to a wide range of contamination environments. This has led to development of guidelines for unified specific creepage distance, for example in IEC 60815. Under freezing conditions, a number of factors change. The surface conductivity of ice is much lower than that of water, but there is the countervailing possibility of accumulating a significant amount of ice. One of the crossover points between applications occurs when a very light layer of hoar frost or freezing fog, simulated in a cold test, fully wets a pre-contaminated insulator. The leakage distance requirements for these conditions are compared with those suggested for conventional clean-fog requirements. The possibility of treating fog accretion as a form of non-soluble deposit density is explored.

Study on AC Artificial-Contaminated Flashover Performance of Various Types of Insulators

Artificial pollution tests have been carried out to study AC flashover performances of various types of porcelain, glass, and polymeric insulators in this paper. The experimental results show that the polluted flashover voltage Uf is affected by equivalent salt deposit density rhoESDD and nonsoluble deposit density rhoNSDD, the influences of which are independent of each other. Based on the analyses of the flashover voltages, the correction formulas of the flashover voltages Uf of various insulators at various rhoESDD and rhoNSDD levels are pointed out. The experimental results also show that there is a distinct difference among the flashover voltages of various types of polluted insulators. At the same pollution degree, the antipollution performance of the fog-type glass insulator is better than those of the outer-rib porcelain insulators. In terms of the effectiveness of creepage distance of insulators, the antipollution performance of polymeric insulators is superior to those of porcelain and glass insulators.

Natural insulator contamination test results on various shed shapes in heavy industrial contamination areas

In Shanghai, China, industrial contamination is very severe and periodic insulator washing is performed not only in substations but also on transmission lines. In order to review the present insulator contamination design and maintenance practices, a series of periodical contamination measurements under de-energized conditions were made. Also insulators that had been energized at two sites for one year were removed, and withstand voltage tests were conducted in an artificial fog chamber. Unexpectedly high ESDD (Equivalent Salt Deposit Density) values >1 mg/cm/sup 2/ and NSDD (Nonsoluble Deposit Density) values over >5 mg/cm/sup 2/ were measured. Aerodynamic type insulators showed a smaller accumulation of contamination than deep-rib type insulators. However, no significant difference can be seen between aerodynamic type and deep-rib type insulators in the withstand voltage per unit insulator string length. CaSO/sub 4/1/2H/sub 2/O (Bassanite) is identified as the most dominant soluble contaminant. >