Key words: insulator; wind power; cleaning; device
Presently, insulator which is widely used in electric power system is easy to get dirty. So we must clean the insulator in time. Even so, every year flashover faults happen continuously. Safe operation in electric power system is imperiled seriously. According to the statistics, insulator accident caused by contamination flashover is the second in the total electric power net accidents. These accidents are merely after lightning strike accidents. However, contamination flashovers’ loss is ten times more than lightning strike accidents. Cleaning by manpower it must take much time and the cost is high. So a kind of totally new scheme is brought forward to solve the problem.
1 Disquisition content:
I have created a kind of cleaning rings for insulator driven by wind. It can automatically clean contamination on insulator surface by wind power. (The invention has already gained China Patent, and Patent Number: 01228431.9, International Application Number: PCT/CN02/00393). Picture 1 as follow.
1- bowl moved by wind 2- insulating ring
Picture 1: The sketch map of cleaning rings for insulator driven by wind.
1- bowls moved by wind 2- insulating ring 3- Plate-shaped hanging insulator
Picture 2: Insulator using the cleaning ring driven by wind.
Specific technique scheme: An insulating ring threads some bowls driven by wind. These bowls are arranged in the same direction forming cleaning rings driven by wind. And cleaning rings driven by wind are tied on plate-shaped hanging insulators, as picture 2. When wind blows, cleaning rings driven by wind will turn. Then the edge of the cleaning bowls driven by wind can ceaselessly scrape off the dirt on the surface of insulator to keep it clean and prevent it from the contamination flashover faults. Cleaning ring adopts light insulating material. By practical wind cleaning test, the effect is very remarkable. The places where is cleaned are bright and clear, but where dosen’t use cleaning ring are begrimed seriously.
Picture 3: Comparison tests photo in practical operation.
Picture 3 is the photo which is after 6 months from practical operation test’s beginning. We can see that the surface of insulator which haven’t used the cleaning ring is begrimed seriously, but the surface of the insulator using the clean ring is very clean.
Refer to GB/T4585.2-1991 (China standard), comparison tests have been carried out in national insulator lightning arrester quality supervise examine center. Comparison test samples adopt type in X-4.5 plate-shaped hanging insulator, and plate’s diameter is 254mm, the discharge distance of insulator’s surface is 300mm, the surface area is 1450cm2, the downward surface area is 910cm2. Test condition: turbid measure, and it’s measurement is (3×3×3)m2 , salt density is 0.2mg/cm2, dust density is 2.0mg/cm2,and stain method is quantificationally paint with brush(according to GB/T5582-93, it corresponds 4 degree’s contamination level. As chart 1, comparison tests result of insulator’s upward and downward surface area using and not using cleaning ring after paint contamination:
Chart 1 Comparison tests result of Flashover voltage caused by manpower contamination
Sample Flashover voltage /kV average value/kV
Three groups insulators not 7.9
using cleaning rings 7.8 7.8
Three groups insulators 11.6
using cleaning rings 12.1 11.8
Compared to JB/T5895-91 standard, 11.8kV corresponds to the flashover voltage of 2 degree's contamination. In other words, in the area where stain is equal to 4 degree's contamination on the surface of insulator, after using the cleaning ring, every insulator's contamination flashover voltage can improve about 4kV.
Because the cleaning ring has a certain number of blows moved by wind, the discharge diatance of insulator's surface has been extended. And passing the resist voltage test, its insulation intensity is higher than the air's, so the influence of the cleaning ring to insulator is able to not be considered.
2.The advantages of using cleaning rings for insulator driven by wind.
110kV transmit electricity lines commonly use 7pieces of insulator. According to the result of test, if X-4.5 or XP-70 insulator is selected and used, and it reaching 4 degree's contamination, and the air humidity reaching definite level, the flashover faults may be happened. But if the cleaning ring has already be fixed, and the air humidity reaching 100%, the flashover faults can't be happened.
The problem of gathering contamination can't be avoided. For example, documentary  introduces the iron tower lied on the left of 220kV nanjing Changjiang crossing river line. It uses LXP-160 glass insulators. 25 pieces of insulator string, and on average every piece support voltage in 5.1kV. November 16, 1976, on the evening of rain and fog, the flashover faults were happened, and 11 pieces of insulator were destroyed. The cause is that the surface of insulators gather contamination reaching 5--20mm. Again for example, the No.249 pole of the 500kV line from pingyao to doushan uses LXY3-160 glass insulators, and 37 pieces string. May 20 , 1999, in the situation of the light rain, the flashover faults were happened, and 9 pieces of insulator were destroyed. The cause is that the surface of insulators gather contamination reaching 0.5--5mm. If the cleaning ring driven by wind were used at that time, the surface may be begrimed not at so level.
The level of gathering contamination is difficult to be defined. Cleaning is twice in one year, and the main assignment is cleaning contamination. Sometimes, the insulators are cleaned a moment ago, but the sand and dust windstorm may begrime the insulator again. The flashover faults will be happened at any time. If the cleaning ring driven by wind were fixed, the cleaning may change twice in one year into once in three years, or much longer time. Thus, the economic benefits will add because of the much electricity selling. Maybe the income is hundreds times to the investment of using cleaning ring.
If in substation, the insulator's outside shape of the equipment are allocated the cleaning ring when they are designed and made preparing to leave the factory, also maybe water cleaning many times in one year will be avoided and power cut due to unnecessary cleaning will be reduced. Then the economic benefits will be huge.
Compared with present technology, using the cleaning rings for insulator driven by wind has such advantages as follows:
(1) The moment the wind blows, it cleans the dirt on insulator. So the surface of the insulator can't be begrimed for a long time to prevent the flashover faults.
(2) The times of cleaning is reduced or avoided to save quite a bit of manpower and material resources.
(3) It avoids unsafe factors caused by other cleaning methods.
(4) The power cut caused by cleaning is greatly reduced. And the reliability of power supply is improved.
 Cai Wei, Li Min, Yang Yanhong, and so on. Insulator Supervision System's design and achievement [J]. China Electric Power, 2002, 35(8):37-40
 GB/T4585.2-1991, In Interflow Electricity using high voltage's insulator carry on Manpower Contamination Test Method--Solid Method.
GB/T5582-93, High Voltage equipment's insulators' outside shape contamination degree.
JB/T5895-91, Insulator's use rule in contamination area.
DL/T626-1997, Plate-shaped hanging insulator's examine rules.
Gu Honglian, Sun Zehui. Glass insulators' run and analyze[J]. Electric Power Construction, 2000, 21(11) : 48-50