Yadda na yanzu da yanayi a cikin abubuwa masu karamin kwalba na birnin SF6

Fuska na tsohon karamin sanka, ko kuma fuska na tsohon karamin sanka, suna da kyakkyawan abin da yaɗuwa. Su zai iya gudanar da kuma yin hankali ga rarrabbin bayanai da rarrabbin adadin tsari a cikin fuskar tsohon karami. Amma, idan yanayin yi ne a cikin al'adu, suke maimaita da wasu tushen ingantaccen da kuma wasu tushen automatikin zuwa gudanar da karamin yanayi a baya, wanda yake taimaka wajen dogara sakamako da ƙasa. Wannan yana da muhimmanci a kan haɗin kawo shugaban ta hanyar al'ummar tsohon karamin.

An yi fuskar tsohon karamin sanka daga fuska mai shanu, fuska mai ƙaramin hawa, fuska mai ƙaramin tsakiyar ƙarfi, zuwa fuska mai ƙaramin SF₆. Daga cikinsu, an samu biyu na farko da suka fito, kuma fuska mai ƙaramin SF₆ yana amfani da ita a fili da biyu na biyu. An fara amfani da fuska mai ƙaramin SF₆ a baya na shekara 1970. Suna amfani da gas sulfur hexafluoride (SF₆) a matsayin gas mai tsakiyar ƙarfi. Wannan nau'in fuska na da kyakkyawan abin da yaɗuwa. A cikin halin yadda aka gudanar da karamin, kyakkyawan abin da yaɗuwan fuska mai ƙaramin SF₆ yana da 10 kafuwar ɗaya a kawai na sa biyu na biyu. Yana da muhimmanci a kan haɗin kawo shugaban da kuma jama'a a kan fanni da tattalin arziki.

1. Kyakkyawan Fuska Mai ƙaramin SF₆

Fuska mai ƙaramin SF₆ ba na shanu, amma ana amfani da gas SF₆ a matsayin gas mai tsakiyar ƙarfi da kuma gas mai haɗin gwiwa. Kyakkyawan haɗin gwiwarsa da kyakkyawan tsakiyar ƙarfisa suna da muhimmanci saboda su na da kyakkyawan abin da yaɗuwa a kawai na fuska mai shanu. Fuska mai ƙaramin SF₆ suna da wasu muhimmanci:

• Kyakkyawan tsakiyar ƙarfi, kyakkyawan haɗin gwiwa, da kuma kyakkyawan haɗin gwiwa ta ɗaya. Saboda haka, a cikin sama da darajar da ke tsayi, an samu ƙaramin ƙaramin da ke da ƙwarewa, wanda ya taimaka wajen taimaka kyakkyawan tattalin arziki na ƙaramin.

• Yanayin da ya fi shi da tsari. Zai iya gudanar da karamin tsari 50kA 19 kere, kuma adadin karamin da aka gudanar da su za a iya duba 4200kA. Tsarin gudanar da karamin yana da tsari, kuma yana daidai a amfani da shi.

• Kyakkyawan gudanar da karamin. Saboda electronegativity gas SF₆, yana da kyakkyawan tsakiyar ƙarfi. Tsakiyar ƙarfi a cikin SF₆ yana taimaka wajen ƙare "tsayin tsakiyar ƙarfi" (ƙarfin tsakiya da ƙarfin tsakiyar). Diffusion ionized plasma yana dogara, wanda yake taimaka wajen ƙare ionization. Karamin da aka gudanar da su yana da tsari, kamar 80-100kA, kuma kuma 200kA. Tsayin tsakiyar ƙarfi yana da tsari, kamar 5-15ms. Amma, kyakkyawan gudanar da karamin a cikin hali-halai kamar reverse-phase, near-zone faults, unloaded long lines, da kuma transformer no-load conditions yana da kyakkyawan abin da yaɗuwa.

• Kyakkyawan haɗin gwiwa. Kyakkyawan haɗin gwiwa gas SF₆ yana da 5-10 kafuwar ɗaya a kawai na hawa.

• Gas SF₆ ba na lafiya, ba na lafiya, ba na duɗu, ba na ƙwayoyi, kuma yana da kyakkyawan haɗin gwiwa. Amma, idan an yi gudanar da karamin, ziyartar pressure da aka yi saboda tsakiyar ƙarfi yana da tsari, wanda yake taimaka wajen taimaka haɗin gwiwa da kuma taimaka ƙwarewa.

2. Tashar Fuska Mai ƙaramin SF₆
2.1 Fuska Mai ƙaramin SF₆ Na Ƙaramin Ƙarfi Biyu

An yi biyu na gas SF₆ (ƙaramin ƙarfi da ƙaramin ƙarfi ɗaya) a cikin fuska. An yi gudanar da ƙaramin ƙarfi zuwa ƙaramin ƙarfi ɗaya a cikin halin yadda an yi gudanar da karamin, a kan taimakawa blowing valve. Idan an kammala gudanar da karamin, an yi kofin blowing valve. Tsarin ƙarfin tsakiya yana da compressor gas da pipes a cikin ƙaramin ƙarfi da ƙaramin ƙarfi ɗaya. Idan pressure gas a cikin ƙaramin ƙarfi yana ƙara, ko kuma idan pressure gas a cikin ƙaramin ƙarfi ɗaya yana ƙara zuwa ƙaramin, compressor gas zai ƙara tsakiyar gas SF₆ a cikin ƙaramin ƙarfi ɗaya zuwa ƙaramin ƙarfi, wanda yake taimaka wajen taimaka gas system mai tsari.

2.2 Fuska Mai ƙaramin SF₆ Na Ƙaramin Ƙarfi Ɗaya

Tsarin ƙaramin ƙarfi ɗaya yana da tsari, kuma yana iya amfani da shi a cikin ƙarin ƙarin ƙaramin temperature. Gas compression type ta yi tashar ƙaramin: a cikin tsakiyar ƙarfi, nau'in ƙaramin ƙarfi ɗaya na farko yana da tsayin tsakiyar ƙarfi ɗaya, kuma adadin karamin da aka gudanar da su yana da tsari (kamar 31.5kA) da kuma ƙaramin ƙaramin voltage yana da tsari (kamar 170kV). Nau'in ƙaramin ƙarfi ɗaya na biyu yana da tsayin tsakiyar ƙarfi biyu, kuma adadin karamin da aka gudanar da su yana ƙara zuwa (40-50kA), amma ƙaramin ƙaramin voltage yana da tsari. Karamin 252kV yana da ƙaramin ƙaramin biyu. Nau'in ƙaramin ƙarfi ɗaya na uku yana da tsayin tsakiyar ƙarfi biyu da kuma tsayin thermal expansion (arc extinguishing hybrid). Adadin karamin da aka gudanar da su yana ƙara zuwa 63kA, da kuma ƙaramin ƙaramin voltage yana da tsari. Ƙaramin ƙaramin ɗaya yana iya ƙara zuwa 252kV, 363kV, 420kV, kuma kuma 550kV.

Tashar ƙaramin ƙarfi ɗaya, a cikin ƙarfin tsakiya, an yi compressor gas mai ƙaramin ƙarfi ɗaya. Muhimmancinta da aka samu saboda ƙara compressor gas a cikin ƙarfin tsakiya sun hada:

• Mass of the entire motion system during the interruption process of the product is reduced.

• The operating power of the product is reduced.

• The buffering of the product becomes easier, and the mechanical life is long.

2.3 Self-energy SF₆ Circuit Breakers

Self-energy SF₆ circuit breakers have two arc extinguishing principles: the thermal expansion principle and the arc rotation principle. Currently, the vast majority of self-energy circuit breakers utilize the thermal expansion principle. The self-energy principle is to use the arc energy to heat the SF₆ gas in the expansion chamber, build pressure, form a gas flow, and extinguish the arc. However, when interrupting small currents, due to the small arc energy, a small piston is required to compress the gas to form an auxiliary blow. Due to the significant reduction in operating power, a spring operating mechanism with a simple structure can be used. The thermal expansion type has now developed to the second generation. The first-generation products achieve the effect of reducing the operating power by reducing the gas compression energy required for arc extinguishing. The diameter of the gas compression piston is designed according to the interrupting of 30% of the maximum fault current, and the motion mass is also small, which reduces the operating power. The second-generation products further improve the thermal expansion effect and the interrupting performance, not only improving the interrupting of capacitive current but also further reducing the operating power.

2.4 Intelligent SF₆ Circuit Breakers

Another characteristic of modern high-voltage circuit breakers is their intelligence, evolving from traditional electromechanical systems into modern intelligent systems centered around computers. Currently, the online detection contents of high-voltage circuit breakers are as follows:

• SF6 gas;

• Operating mechanism system;

• Release;

• Control and auxiliary circuits;

• Power transmission chain.

Through these detections, more than 90% of the faults can be discovered. Online detection can change the regular maintenance of circuit breakers to real-time condition-based maintenance.

3. Porcelain Post Type and Tank Type SF₆ Circuit Breakers and Their Applications

China first applied SF₆ circuit breakers in 1970 when the Northeast Electric Power Administration imported three H-912 type 220KV double-pressure porcelain post type SF₆ circuit breakers produced by Siemens from abroad and installed them in the HuShitai primary substation in Shenyang. They are still operating well today.

High-voltage sulfur hexafluoride circuit breakers are divided into porcelain post type and tank type according to their structure. When comparing the two, they each have their own characteristics:

• Both porcelain post type and tank type high-voltage SF₆ circuit breakers can meet the requirements of high voltage and large capacity. The arc extinguishing chamber of the porcelain post type is installed on the insulating support. By connecting the arc extinguishing chambers in series and installing them on the insulating support at an appropriate height, any rated voltage value can be obtained. The insulating support is mostly a porcelain post, and organic composite supports have also emerged. The arc extinguishing chamber of the tank type is installed in a metal tank connected to the ground potential. Under high voltage, multiple arc extinguishing chambers need to be connected in series and installed in the same tank for each phase.

• Installation of current transformers. In terms of installing current transformers, porcelain post type circuit breakers are at a disadvantage. Because the arc extinguishing chamber of the porcelain post type is installed inside the insulator and on top of the insulating support, the current transformer must be installed separately on its own insulating support. However, the bushing type current transformer can be installed on the bushing of the tank type circuit breaker. In some application scenarios, the circuit breaker does not need to be equipped with a current transformer, especially when used as a switch for switching capacitor banks and shunt reactors. Here, the price of the porcelain post type is only 60% of that of the tank type circuit breaker, and due to the use of multiple fracture ports, it can better withstand re-strikes.

• External withstand voltage capacity. From the perspective of external withstand voltage, multiple series arc extinguishing chambers of the porcelain post type circuit breaker can meet any rated voltage value, but its external insulation withstand capacity is limited by the length of the arc extinguishing chamber itself. For the tank type circuit breaker, as long as the necessary withstand capacity for reducing the number of fracture ports can be developed, an insulating bushing can be manufactured. Therefore, the tank type circuit breaker can achieve a single fracture port of 550kV/63kA and a double fracture port of 1100kV/50kA.

• Consumption of SF₆ gas. In terms of the consumption of SP6 gas, the porcelain post type is superior to the tank type. The gas consumption of the tank type circuit breaker is much higher than that of the porcelain post type.

• Environmental adaptability. From the perspective of environmental adaptability, the large-volume tank type circuit breaker shows its advantages. A heater can be installed in the tank type circuit breaker, while it cannot be installed in the porcelain post type.

• Seismic resistance. From the perspective of seismic resistance, the tank type circuit breaker is far better than the porcelain post type. Because the porcelain post type circuit breaker has a high center of gravity, its seismic resistance is poor.

• Price comparison. In terms of price, for the same capacity, the porcelain post type circuit breaker is better than the tank type. Generally, the price of the tank type circuit breaker is about 20% higher than that of the porcelain post type circuit breaker with an external current transformer (such as an SF₆ transformer).

4. Issues to be Noted During the Operation and Maintenance of SF₆ Circuit Breakers

In order to strictly control the gas leakage and prevent moisture and dampness from invading the box, the processing technology and material requirements are much higher than those of general high-voltage electrical appliances. At the same time, a special SF₆ gas system is required, including a valve with good sealing performance, leak detection equipment, a gas recovery device, and pressure monitoring. In addition, due to the large consumption of metal, the manufacturing complexity is increased.

Pure SF₆ gas is colorless, odorless, non-toxic, and non-flammable. However, in the synthesis of sulfur hexafluoride, low-fluoride compounds of sulfur are also produced, which are toxic. In the circuit breaker, the gas will be decomposed under the high temperature of the arc through dissociation and ionization, generating highly toxic gases. Therefore, an adsorber is installed in the circuit breaker, and activated aluminum is placed in it to absorb these toxic gases.

Even so, special attention should be paid to preventing poisoning during maintenance. Therefore, the gas must be evacuated and discharged cleanly before work. If an unpleasant odor is still smelled, a gas mask and rubber gloves should be worn. In addition, the arc decomposition products also contain some metal fluorides, which are scattered in the circuit breaker in powder form. Although these powders are not highly toxic substances, precautions should still be taken to prevent them from being inhaled during cleaning.

5. Conclusion

With the continuous increase in the voltage of the power system, whether it is the porcelain post type or the tank type of SF₆ circuit breakers, they are constantly evolving with technological progress. In particular, in recent years, the self-energy arc extinguishing principle has been developed and applied, that is, high pressure is used to form a gas blow to extinguish the arc. The number of fracture ports is reduced, and the consumption of materials is decreased.

Due to its relatively high price and high requirements for the application, management, and operation of SF₆ gas, it is not widely applied in medium voltage (35kV, 10kV). In general, high-voltage SF₆ circuit breakers have a broad application prospect, and the technological research, development, and upgrading of products will bring significant economic and social benefits.