The process of insulation pollution flashover and anti-pollution measures

1. Overview

Pollution flashover of electrical equipment refers to the pollution attached to the insulation surface of electrical equipment under humid conditions. Its soluble substances gradually dissolve in water and form on the insulation surface. A layer of conductive film greatly reduces the insulation level of the insulator, resulting in strong discharge phenomena under the action of the electric field. Because technical measures for adjusting insulation have their limitations, the general configuration level of external insulation for domestic power transmission and transformation equipment cannot meet the needs of special circumstances. For example, the anti-pollution level of the external insulation of electric porcelain products should be improved according to the standard configuration, and the leakage ratio of the insulator strings of lines above 110KV is not enough, etc. This causes the insulation of electrical equipment in dirty areas to be easily broken down in harsh climates, resulting in pollution. Flash, in serious cases, it will affect the safe operation of electrical equipment, bring unnecessary losses to production, and secretly threaten production safety.

With the increasing development of social industrialization, the safe and stable operation of the power system is becoming more and more important, especially for a petrochemical enterprise with continuous production, because fluctuations and failures of the power system will cause Work stoppages, production shutdowns, and even fire and explosion accidents have caused significant economic losses and social impacts;

In the five years from 1998 to 2002, the maximum operation of 110-220kV lines in Zhuhai was 38.286 hundred kilometers per year. Here, During this period, pollution flashover tripping occurred 9 times, and the pollution flashover tripping rate was 0.24 times/100km·year, which was far greater than the recommended value of 0.1 times/100km·year.

In mid-February 2001, a 12kV SF6 circuit breaker experienced a flashover fault in a county in southeastern Hunan Province. The wiring board at the three-phase end was in contact with the ground flange along the surface of the porcelain insulator. A flashover occurred on the disk, which also caused a phase-to-phase short circuit, resulting in a large-scale power outage in the area;

On April 8, 2001, a 12kV SF6 circuit breaker also experienced a flashover failure in Taiyuan City, Shanxi Province. The flashover burning situation is basically the same as the previous case.

In the early morning of February 22, 2002, a large-scale severe pollution flashover occurred in the Shenyang power grid due to dense fog. The pollution flashover caused the 220KV power supply system to collapse. Our company's 66KV and below power supply system collapsed and fluctuated severely. The power supply did not stabilize until 1 o'clock in the afternoon. This fog flash caused the entire plant's power supply, water supply, and steam supply to be interrupted. Atmospheric pressure, catalytic cracking, gas fractionation, Urea dewaxing product refining and other production equipment were shut down. In particular, important equipment such as the main fan and steam compressor of the catalytic device suddenly shut down, which can easily lead to deflagration and explosion accidents if operated carelessly. Therefore, new technologies, new materials and new methods for preventing pollution flashover of electrical equipment have attracted more and more attention.

2. Countermeasures

However, the contradiction is that the increase in voltage level, pollution of the atmospheric environment and pollution from enterprises will lead to frequent pollution flashover accidents in power transmission and transformation equipment. , heavy fog, acid mist, drizzle, humid air and other bad weather have seriously affected the safe operation of outdoor high-voltage electrical equipment.

There are many measures to prevent pollution flashover. The traditional method is power outage cleaning in spring and autumn, and the use of silicone oil, silicone grease and other coatings to reasonably adjust the creepage distance of external insulation. In recent years, there are Use anti-flash climbing skirts, use RTV anti-fouling flash coatings, etc.

1. Short-term silicone oil

The method of use is to clean the outdoor high-voltage electrical equipment every year in spring and autumn, wipe off the previous silicone oil, and then re-apply it. Last time. Since silicone oil has a certain degree of insulation and hydrophobicity, it plays a certain role in preventing pollution flashover; however, because silicone oil has a short validity period of only about half a year, and it is in a non-cured state, it is easy to adhere to dust, and then form in rainy and foggy weather. Pollution flashover is even more serious.

2. Reasonable creep adjustment

Climb adjustment refers to increasing the creepage distance of the external insulation of electrical equipment and improving the insulation level. For example, increase the number of insulators in polluted areas, or use dust-proof insulators, glass insulators and synthetic insulators, etc. Operation experience shows that in severely polluted areas, the use of new insulator strings has better anti-fouling effects, but this product is only suitable for transmission lines. In addition, the climb adjustment method of adding insulator strings involves the adjustment of the minimum air gap between the live conductors and the tower, the adjustment of the distance between the cross arms under the live conductors, and the windage calibration after the climb adjustment.

3. Anti-fouling flash-increasing auxiliary umbrella skirts

Anti-fouling flash-increasing auxiliary umbrella skirts are generally made of synthetic silicone rubber, which is made of original porcelain bottles and porcelain insulators. The adhesively mounted climbing auxiliary shed increases the curve and the flashover distance, thus increasing the flashover voltage. In addition, because synthetic silicone rubber has good insulation and hydrophobicity, the dust on it is not easily infiltrated by water and forms a flashover channel, thereby reducing the chance of pollution flashover. However, the synthetic silicone rubber anti-fouling flash-increasing auxiliary umbrella skirt also has some technical problems. For example: when bonding, the porcelain bottle must be very clean and flat, and the adhesive must be applied evenly, otherwise the interface will be uneven and easy to accumulate dust, or The glue is dry and cracked; another example: due to differences in manufacturers' processing techniques and raw material quality, some products are easily damaged, broken, deformed, cracked, etc.

4. One-component RTV electric anti-fouling flashover coating

In recent years, one-component RTV (RoomTemperatureVulcanizedSiliconeRubber) electric anti-fouling flashover coating is known for its long-lasting and cost-free performance. As a new technology and new material with outstanding advantages such as maintenance, it has been widely used in the field of anti-pollution flashover of power systems and has achieved remarkable results.

The one-component RTV coating has good hydrophobicity and hydrophobic migration, which greatly improves the resistance to pollution and lightning voltage of the external insulation of power transmission and transformation equipment. Compared with uncoated porcelain bottles, the resistance to pollution and lightning voltage is Can be increased by more than 2 times. Hydrophobicity means that the force between generally non-polar solid medium molecules and their surface water molecules is less than the cohesive force between the water molecules themselves, and the surface water often forms isolated water droplets instead of a continuous water film. The hydrophobic migration of RTV means that the hydrophilic dust and dirt accumulated on the surface of the RTV coating becomes hydrophobic after a certain period of time, that is, the hydrophobicity of the RTV coating migrates to the surface of the dirt layer; at this time, after water droplets are sprayed on the surface , the dirt layer is difficult to wet due to its hydrophobicity, and only discontinuous water droplets remain on the surface of the dirt layer. This performance greatly improves the anti-pollution flashover ability of electrical equipment.

One-component RTV electric anti-fouling flashover coating has good electrical, physical and chemical properties. Its breakdown voltage is above 17KV/mm; it can operate for a long time between -40℃~+80℃ and is temperature-resistant; it has good adhesion to porcelain insulators; it can be tack-dry after spraying at room temperature for 30 minutes and can be cured in 24 hours. Long-term elasticity; resistant to acid, alkali and oil corrosion, and will not cause blistering, wrinkling, discoloration and peeling; resistant to environmental aging, the coating will not crack, powder, peel or peel under natural conditions, suitable for outdoor use The lifespan is above 5. It can be used on the external insulation of electrical equipment in power plants, chemical industries, steel, cement and other heavily polluted areas and industries, and has a remarkable anti-pollution flashover effect.

Our company's 66KV outdoor substation*** has three incoming lines, two main transformers, and the busbar connection method is single busbar segmented type; for a long time, every time it rains, snows, and fogs, The pollution flashover situation of outdoor equipment is always serious, and abnormal operation conditions such as single-phase grounding or voltage fluctuations often occur. In the second half of 2002, based on the actual pollution flashover situation, the branch factory carried out RTV anti-pollution on outdoor electrical equipment. Flash paint spraying, a one-time investment of 38,000 yuan, has solved the serious problem of pollution flashover that has plagued our factory for a long time, ensuring safe and stable power supply. The operation has been very good so far. There is no discharge sound or flashover phenomenon in outdoor equipment during bad weather; Moreover, after the electrical equipment is sprayed with RTV anti-fouling flash coating, the equipment cleaning tasks during spring and autumn inspections are reduced, saving a lot of manpower and material resources, and reducing power outage time.

When mentioning the one-component RTV electric anti-fouling flashover coating, the two-component RTV electric anti-fouling flashover coating should also be mentioned. Compared with single-component RTV coatings, two-component RTV coatings also improve the anti-pollution flashover ability of electrical equipment after being applied on site. However, the two components of two-component RTV coatings are difficult to master when deploying on site. If the curing time is too long, the external environment will have a negative impact on it, or if the curing time is not sprayed in advance, it will cause trouble in the actual construction on site.

When spraying the single-component RTV electric anti-pollution flashover coating, attention should be paid to choosing a sunny, dry and less windy weather for construction. The surface of the porcelain bottle should be cleaned before spraying; the thickness of the coating is very important for its anti-fouling flashover effect. , in order to ensure that the coating thickness reaches the requirement of 0.25mm or above, spraying should be done 2 to 3 times, and the last layer should be sprayed after the previous layer is dry. For small area construction, brushing can be used, but care should be taken not to make the coating too thick or too thin, nor to apply it repeatedly to avoid peeling.

3. Conclusion:

Judging from the company’s electrical anti-pollution flashover experience over the past few years, the use of single-component RTV electric anti-pollution flashover coating is easy to construct, has a long validity period, and can significantly improve The external insulation pollution flashover of electrical equipment is an effective technical means to prevent pollution flashover and reduce the amount of cleaning and maintenance on the external insulation of the enterprise's power supply system, providing the necessary guarantee for the safe production of enterprises.