Analîz ya Sêbepên Xeta û Piramên Kardebikinê ya Dîmçananên SF6

Dîrokda SF₆ da, gazê SF₆ di envîromanê mezin de divê bibeke hatine wekhevîna berdewamên toxîk û korozîf. Vê divê bibeke jî neyê bibîne ser layera îzolekirina. Ji bo pêşandina vê rewşê, di demê ku hêsanîn proteksiyonê ya anîya elektrîkî ye, dêweha îzolekirinê taybet bikin. Di sora yekê de, pirsgirêka hêsan dibînin û çareserî yên peywist bike.

1 Analîza Rewşa

Yek switch 110 kV li ser biryarê ji bi şimşek xasîb kiribû, ku bi vekiliya yek bîrkarîya switch intervalê ve girîngkir. Ji nîşana switchê, tune rewanîn pirsgirêk nedeyê. Lê, di dema testkirina circuit breakerê de, hewceyê ku ampera phase A guhertir e yên phase B û C. Komîta testkirina li ser biryarê switchê tîra. Testkirina wê bi alîyatên taybetandîyê ve tîra, û wan biguherîn destpêkî û perestîna îzolekirinê, carakteristikên operasyonan ên switch, resistanceyê loop, û testê AC voltage. Bi vê rêbaza testkirinê, pirsgirêka arc ên switchê tîra, û komîtan gasê SF₆ ên switch ên circuit breaker ên test bikin. Circuit breaker ên intervalê ji SIEMENS ên Hangzhou hatiye were hatî, û modelê 3AP1FG e. Wan rezultatên testkirinê ji testkirina switch ên circuit breaker ên intervalê werin:

• Îzolekirina resistanceyê ên switch ên CT: phase A 22.5 G, phase B 17.4 G, û phase C 17.8 G.

• Carakteristikên operasyonan ên switch ên circuit breaker, li ser content ên rapora pêşketinê, closing time 65 ms; opening time 18 ms. Rezultatên ji testkirinê hatiye werin: ji bo phase A, closing time 61.1 ms, û opening time 16.8 ms; ji bo phase B, closing time 61.1 ms, û opening time 16.1 ms; ji bo phase C, closing time 58.9 ms, û opening time 16.4 ms. Closing synchronism 1.2 ms; opening synchronism 0.3 ms.

• Rezultat ên testê AC voltage ên switch disconnector: 75 kV, 1 minute, passed.

• Test ên komîtan gas ên SF₆ ên switch dikare ku ji bo phase A, sulfur dioxide 4.13 l/L, û hydrogen sulfide 3.15 l/L; ji bo phase B, sulfur dioxide 0 l/L, û hydrogen sulfide 0 l/L; ji bo phase C, sulfur dioxide 0 l/L, û hydrogen sulfide 0 l/L. Li ser rêzikên test procedures ên electrical equipment, content ên sulfur dioxide divê be herêmîn 3 l/L, û content ên hydrogen sulfide divê be herêmîn 2 l/L. Rezultat ên test ên komîtan gas ên SF₆ ên switch ên phase A dikare ku ji bo herêmîn be herêmîn, ji bo ku testyan divê li ser vê yekê bêtirînin.

• Test ên resistanceyê loop ên switch ên circuit breaker. Li ser rêzikên test procedures, measured value divê be herêmîn 120% ên value ên manufacturer. Loop resistance tester bi vê testê ve bikar îniyê, û data ên ji sê testan were hatî: first test result: phase A 1368 μΩ; phase B 694 μΩ; phase C 579 μΩ; second test result: phase A 38 μΩ; phase B 36 μΩ; phase C 35 μΩ; third test result: phase A 38 μΩ; phase B 39 μΩ; phase C 38 μΩ.

Li ser analîz ên data ên ji testkirinê hatiye werin, heman karakteristikên tune dikarin tayin bikin: Yekem, test value ên phase A guhertir e yên phase B û C, û hata herêmîn 1000 μΩ were keviriye, ku guhertir e yên normal resistance. Duwem, ji rezultatan ên sê testan, rezultatan ên test ên phase A diguhertin guhertir û nistan, û hata herêmîn repeatability ên sê testan. Sêyem, ji bo compare ên rezultatan ên phase A, B, û C, values dikarin guhertir diguhertin. Çardehem, test value ên phase A guhertir e yên previous tests. Li ser test method û analîz ên data ên ji testkirinê, dikarin tayin bikin ku insulation effect ên phase A ên circuit breaker tune e, û carakteristikên operasyonan ên switch ên circuit breaker comply with the relevant regulations. Lekin, komîtan gas ên SF₆ ên switch ên phase A herêmîn be standard, û loop resistance herêmîn be standard. Ji bo, after disassembly and analysis, characteristics of the circuit breaker are as follows: Firstly, there is black powder attached to the contacts of phase A. Although the amount is not large, the burrs and fuzz on the surface are very obvious. Secondly, traces of arc burning are found at the moving contacts.

2 Faults of SF₆ Circuit Breaker and the Causes of Faults

The above case is a fault of the switch of the SF₆ circuit breaker, manifested as a reclosing problem. When a faulty circuit breaker continues to be used, the existence of such a switch fault can lead to refusal-to-operate, misoperation faults, and insulation faults, which are very harmful.

2.1 Refusal-to-operate and Misoperation Faults of SF₆ Circuit Breaker

The refusal-to-operate of the SF₆ circuit breaker, that is, refusal-to-open and refusal-to-close, means that the circuit breaker does not perform corresponding actions after the opening or closing signal is sent. The misoperation of the circuit breaker means that the circuit breaker performs opening or closing actions without receiving an operation command, and it is also possible that the actions of the circuit breaker do not conform to the operation command. The SF₆ circuit breaker may also have the problem of "unauthorized tripping", that is, the protection device does not send an action signal, and the circuit breaker automatically trips without manual operation. There are many reasons for the refusal-to-operate or misoperation problems of the circuit breaker, such as mechanical faults of the circuit breaker, faults of electrical equipment, and faults of relay protection devices.

2.2 Insulation Faults of SF₆ Circuit Breaker

If the circuit breaker has insulation faults, SF₆ gas leakage will occur, and mechanical faults will also be caused, mainly manifested as internal insulation flashover breakdown to the ground, flashover breakdown caused by overvoltage due to lightning, capacitive bushing flashover, external insulation flashover breakdown to the ground, and flashover of porcelain bushings and insulating rods.

2.3 Main Causes of Refusal-to-operate and Misoperation Faults

The mechanical cause of the refusal-to-operate fault of the circuit breaker is that there are omissions in the production, installation, debugging, or technical maintenance of the circuit breaker, leading to quality problems. The refusal-to-operate of the circuit breaker caused by such mechanical faults accounts for more than 60% of all refusal-to-operate faults of the circuit breaker. The faults of the circuit breaker caused by electrical reasons are mainly manifested as problems in secondary wiring, jamming of the opening and closing iron cores, burnout of coils, burnout of the opening loop resistance, faults of the locking relay protection device, faults of the operating power supply, and faults of auxiliary switches.

2.4 Causes of Insulation Faults

The causes of internal insulation faults of the circuit breaker include the presence of metal objects inside the circuit breaker, which leads to conduction and discharge faults; the presence of a floating potential inside the circuit breaker, which causes discharge faults; flashover faults along the surface of the insulating parts of the circuit breaker, and imperfect design of the insulating parts. The causes of external insulation faults of the circuit breaker are that the creepage distance of the external insulation of the porcelain bushing does not meet the specified standard, and in terms of appearance, the specifications do not meet the requirements, which is likely to cause external insulation flashover of the porcelain bushing. If there are quality problems in the manufacture of the porcelain bushing and the working environment is dirty, insulation flashover will also occur.

3 Treatment Methods for SF₆ Circuit Breaker Faults
3.1 Measuring the Resistance of the Main Circuit

When the switch of the circuit breaker is in the closing state, measure the resistance of the main circuit between the incoming line and the outgoing line. The current can be any value between 100 A and the rated current. If the casing of the grounding switch's conductive rod can be effectively isolated from the insulation, the parallel resistance of the conductor casing can be measured, and the DC resistance of the conductor casing can also be measured.

3.2 Performing an AC Withstand Voltage Test on the Circuit Breaker

Performing an AC withstand voltage test on the circuit breaker can reveal the defects of the test specimen. Simulate the operation of the test specimen to understand its ability to withstand overvoltage. When inspecting various impurities of free conductive particles, the sensitivity of the AC voltage is very high.

3.3 Conducting Routine Inspections and Experimental Tests

To avoid faults during the operation of the circuit breaker, routine inspections and experimental tests should be carried out, including checking the rated operating voltage of the circuit breaker and testing its time characteristics. When checking the mechanical characteristics of the circuit breaker, all mechanical components should be inspected, and the appearance of the operating mechanism should also be inspected to ensure that the opening and closing coils are in good condition.

3.4 Testing the Circuit Breaker Using the Disassembly and Chemical Method

When the circuit breaker is in normal operation, SF₆ does not react chemically with metallic materials and organic solid materials. Arc discharge can play a catalytic role, resulting in chemical reactions. When detecting the decomposition products of SF₆ gas, the main chemical components to be detected include sulfur dioxide, hydrogen sulfide, methane, and carbon monoxide. By analyzing the concentration of the gas, potential hidden faults of the SF₆ circuit breaker can be judged.

4 Conclusion

In conclusion, the SF₆ circuit breaker plays an increasingly important role in the power system. Effectively maintaining the normal operation of the SF₆ circuit breaker is crucial for the safe operation of the system. For operation and maintenance personnel, understanding the performance of the circuit breaker, recognizing the causes of faults, and finding reasonable treatment methods according to the causes have become necessary professional skills to ensure the safe operation of the power system.