Composite insulator external insulation design methods under dc voltage, the line suspension insulator outer insulation is how to choose at present, the uhv dc transmission project construction the key problem.
, but the guide for the selection of uhv dc composite insulator
has not, IEC60815 on international standards are revised, external insulation selection guide of dc power transmission and transformation project will be put on the agenda, guideline of remains to be time, cannot satisfy the need for engineering construction in our country.
So far, no external insulation composite insulator under dc voltage is about basic problems of research reports, select guideline so urgently need to conduct in-depth on the issue of corresponding system research.
1 empirical method for constructing HVDC project, according to the existing dc power transmission and transformation engineering of high voltage insulator creepage than from determine the outer insulation level.
The advantages of this method is consistent with the HVDC project operation experience of existing;
Limitation is that when determining external insulation level, the filth of the two lines is the same or similar, and require of the engineering of the insulator creepage more appropriate than distance.
This method is generally not directly used for design, are commonly used to validate the result of the design review.
Than 2 creepage distance method this method to divide pollution area, then according to the district level to determine than creepage distance.
For HVDC project to build, but according to adjacent existing ac transmission line insulator than from determine the outer insulation level.
Under dc voltage is due to the composite insulator has the effect that the electrostatic dust collection, insulator under dc voltage is unclean above communication product, in addition, in the same product the unclean condition of composite insulator dc lightning down in communication, so than the dc creepage distance should be greater than in the design of communication.
Its deficiency is ac, dc creepage than from the conversion coefficient of certainty is empirical, lack of scientific basis, under dc voltage is still need to continue to accumulate experience in running.
In addition, the same straight, ac insulator surface pollution of natural environment condition is different, so in the same area ac and dc transmission lines to the level of the corresponding pollution are not the same, need to be polluted area level correction, otherwise there is no comparability.
When determining dc insulator than distance, adjacent to the exchange of insulator more appropriate than distance.
Differences of different types of ac insulator valid creepage distance can also affect the reliability of the dc line insulation configuration.
3 fouling compression method according to the actual test for composite insulator under the different levels of impurity dirt resistant lightning pressure, make the selected insulator string of fouling resistance pressure is greater than the line lightning * big operating voltage, and leave the certain safety margin, the method and the real insulator pollution resistance associated directly, is a kind of ideal determination of insulator string.
Limitation is: to do a lot of experiments, especially the actual lines of insulator pollution flashover experiments, may choose to uhv dc transmission lines is to be a large tonnage of insulator pollution flashover test.
Fouling resistance method is first applied constant voltage start again after wet process, and the system running in the working state of polluted insulator is consistent.
The artificial pollution and natural defile the equivalence of the problems, solve the problem there are two ideas: one is based on lines and natural product test station insulator pollution law research, and make the artificial contamination of the ash density, impurity distribution non-uniform conditions and filth and natural equivalence as possible types of salt;
Another kind is to study the distribution of clear with grey density, filthy uneven status and factors such as the kinds of salt effect on fouling lightning pressure respectively, and the influence coefficient, the conventional artificial contamination test results are corrected.
Fouling resistance method is an ideal method to long line insulator string design, therefore, need to accumulate experience, and vigorously promoted.
Comparing the above three methods, the first two are empirical, not reflect the influence of the shape of composite insulator, and a large number of experiments show that the shape of the insulator has a great influence on the pollution flashover resistance ability.
Fouling resistance method is close to the actual insulator pollution flashover resistance ability, us, Japan and other countries mainly USES the method of fouling resistance, our country should vigorously strengthen the research of this method.
This paper focuses on the use of fouling resistance for insulator key issues involved in the selection.
Actual design can choose according to method of fouling resistance in the process of insulator and its string length and number, than according to the empirical method and creepage distance method to check, by the method of three kinds of engineering design, each other can verify the rationality and reliability of the design results.
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