بڕیکردنی سەرچاوەی خراپی ڕێکخراوە SF6 لە ناو شارکەری ٧٥٠ کیلووۆڵت

Felix Spark

qalab: Daxwaza û Baxta

China

Birê çavkaniyên şînên elektrîkî û kêmûyên çendkirinê, gazî sulfur hexafluoride (SF₆) hatiye bikar bîn kirîn di sisteman de ku voltajê meh û zi vê meh. Hêsan bi sîfetanê da, SF₆ circuit breakers zêdetir tevniyên û demê xizmetê wê ya dêrhatîne. Lê, bi gumanan û baranîn, çewtiyan ên SF₆ circuit breakers dikare derbasên bigihînin, taybetmend derbasên çendkirina, ku guherandîna serperestîya wergerdê digirtin. Derbasên çendkirina nivîsandin navber û herî hêsan tarîkên xizmetê, lê dikare wekî pirsgirêka yekbûyî yên genzînên elektrîkî û kompanên metalî û hata pêşkeftina jengal û çendkirinan. Buna, li serastina derbasên çendkirina SF₆ circuit breakers, têkiliyên paşveganîyê bibînin û rêzikên parastînê bidin, hejmarên mezin ên li serastina serperestîya wergerdan.

Îma, navendiyên wan û navendiyên din hatine bikar bîn kirîn di ser rûsên derbasên SF₆ circuit breakers, navendî li ser testên performansê elektrîkî, analîzên cih û simulasyonên dagilatên elektrîkî. Lê, ji bo struktûra napsîtîn ên SF₆ circuit breakers û veguhestinên çend tiştan, wan biguherînin dikarin beşdar ne. Taybetmend bi derbasên çendkirina di seroperasyonda, ji bo berdewamên şertên ji bo malpera û kesandinê, nivîsandin navber û herî hêsan ne.

Buna, ma amadekirin analîz navber û herî hêsan, navendî li ser testên derbasê malpera, analîzên kesandinê û testên performansê elektrîkî, ji bo derbasên çendkirina SF₆ circuit breaker di substasyonê. Amacê ye ku serastina derbas ên bi serastî û pêşkeftina bînîyên ilmiyên û teknîkî yên parastînê, operasyon û perdekirinê û derbasên din di seroperasyonda.

(2) Testi Produktên Çendkirina Gazê SF₆, Mikro - Awa û Pêvajoyêt

Testên malpera hatine bikar bîn kirîn ji bo produktên çendkirina gazê SF₆, mikro - awa û pêvajoyêt di SF₆ circuit breaker. Daneyên testê divê di Cihê 1 de. Li ser analîzê daneyên testê, produktên çendkirina gazê SF₆ û mikro - awa di Cihê C di SF₆ circuit breaker de dikare bibeştar bibe ku standartên "Kodê Testên Pardekirinê Malpera Sisteman û Têrkîkirina Elektrîkî" (SO₂ ≤ 1 μL/L, H₂S ≤ 1 μL/L, mikro - awa ≤ 300 μL/L) [5]. Berhemîn, daneyên testê di gas chambers de di circuit breakers de hatine bibe navber. Ji bo daneyên di vir, dikare bêyîne ku dikare derbasên çendkirina di Cihê C di SF₆ circuit breaker de bibe.

Cihê 1 Daneyên Testê Produktên Çendkirina Gazê SF₆, Mikro - Awa û Pêvajoyêt

(3) Testi Direksiyonê Insulasyonê Mîn Circuit Breaker
Di testi direksiyonê insulasyonê Cihê C di SF₆ circuit breaker, dewletên operasyonê standard bêyîne û dibêje ku circuit breaker di state - open - circuit. Di testê de, birînîn bushing di ser ground, û voltage di ser birînîn bushing. Buna, performansa insulasyonê di har portê circuit breaker, û di navendîn conductive circuit û casing.
Li ser analîzê daneyên testê, dikare bibe ku performansa insulasyonê Cihê C di circuit breaker de navber bibe, taybetmend problemê insulasyonê di portê disconnection di side - Ⅱ - bus de. Daneyên testê di Cihê 2 de.

Cihê 2 Daneyên Testê Insulasyonê Portê Disconnection di Side - Ⅱ - Bus de

(4) Testi Capacitance û Dielectric Loss an Parallel Capacitors di Navendî Interrupting Ports

Ji bo şertên testi malpera, ji bo testi capacitance ên her interrupting port capacitor individual, metoda testi comparativ ên capacitance û dielectric loss an parallel capacitors di navendî interrupting ports ABC - phase circuit breakers. Di operasyonê têkiliyê, di state - open - circuit, metoda inter - bushing (positive connection) û bushing - to - ground (negative connection) bêyîne capacitance û dielectric loss. Daneyên testê di Cihê 3 de.

Cihê 3 Daneyên Testê Capacitance û Dielectric Loss an Faulty Circuit Breaker

Li ser analîzê comparativ Cihê 3, dikare bibe ku capacitance value di positive - connection test de navber bibe. Lê, ji bo stray capacitance di circuit breaker, dikare bibe ku measured value û calculated value. Lê, ji bo capacitances an interrupting ports among the ABC phases, differences in capacitance among the three phases were relatively small. Ji bo daneyên, dikare bibe ku state of the parallel capacitor of the C - phase interrupting port was normal.

(5) Testi Inside the Circuit Breaker Tank

Di seroperasyonê, gas ên Cihê C di faulty circuit breaker de hatine professional recovered. Dibêje, endoscope bêyîne testi deep inside the tank. Di testê de, dikare bibe ku closing resistance near the Ⅱ - bus side had a breakdown. Black resistance chip fragments scattered at the bottom of the tank. In addition, it was also found that the polytetrafluoroethylene sheath of one of the closing resistances had cracked and fallen to the bottom of the tank.

2.1.1 Testi Disconnect Switch

After a detailed on - site inspection, obvious burning marks were found on the arcing finger parts of the moving contacts on both sides of Cihê C di disconnect switches. Subsequently, by manually operating the disconnect switch of Cihê C on - site, the entire operation process was smooth without any jamming. Moreover, during the inspection, it was observed that there was no welding phenomenon between the moving and static contacts. After the opening operation was completed, a detailed inspection of the static contact base and the contact fingers was further carried out, and no serious burning marks were found.

2.1.2 Testi Secondary Equipment

At 12:31:50.758 on June 18, 2022, Cihê C di faulty circuit breaker in the 750kV substation was grounded. After the fault occurred, the line fiber - optic differential protection and the bus differential protection of 750kV Bus - Ⅱ both operated correctly. Through an in - depth analysis of the fault current and the operation of the bus differential protection and the line protection, when the disconnect switch was in the closed state (during which the system voltage remained stable without over - voltage), it was observed that 750kV Bus - Ⅱ supplied fault current to the fault point. It is worth noting that CT₇ and CT₈ involved in the bus differential protection of the faulty circuit breaker did not detect the existence of fault current. Based on this observation, it was determined that the fault point should be in the area between circuit breaker CT₇ and the bus. Meanwhile, CT₁ and CT₂ for line protection detected the existence of fault current, and the value of the fault current reached a primary current of 4.5kA. Therefore, it was further inferred that the fault point was in the area between CT₂ of the faulty circuit breaker and the interrupting port on the Ⅱ - bus side of the circuit breaker. This inference was consistent with the location of the fault point found in the on - site internal inspection.

2.2 Dismantling Inspection

As shown in Figure 2, during the inspection of the inside of the tank during the circuit breaker dismantling process, fragments of the closing resistance and its protective sheath were observed scattered around. Some resistance chips of the fourth - column closing resistance, which was connected in parallel with the main interrupting port on the mechanism side of the circuit breaker, had exploded, and the corresponding two resistance protective sheaths had also ruptured. End shield A of the resistance showed traces of discharge ablation on the inner wall of the tank, and shield B also had traces of discharge ablation on A. In addition, the surface of the insulating support rod showed blackened traces. By checking the assembly, factory test, and on - site installation data of the circuit breaker, and inspecting the main insulating parts, no abnormalities were found.

3 Fault Cause Analysis

Through dismantling analysis, the following conclusions were drawn: During the closing process of the disconnect switch, the end shield A of the resistance first discharged to the inner wall of the tank. This led to abnormal currents in the fourth, third, and second - column closing resistances. Subsequently, shield B discharged to A, causing the second and third - column resistances to short - circuit, and the current was mainly concentrated in the fourth column. This phenomenon caused the temperature of the resistance chips in the fourth column to rise sharply, eventually leading to explosion, and the resistance protective sheath broke and fell off. During the discharge process, the generation of high - temperature arcs caused the surface of the insulating support rod to become blackened.

The tank - type circuit breaker can withstand a lightning impulse voltage of up to 2100kV. During the normal closing process of the disconnect switch, although over - voltage may occur, under normal operating conditions, this level of over - voltage is not sufficient to trigger the discharge mechanism of the circuit breaker. However, through in - depth analysis and inference, it is preliminarily suspected that there may be foreign objects inside the tank. These foreign objects may have an adverse impact on the electric field distribution, causing the electric field to distort and exceeding the insulation strength that the SF₆ gas gap can withstand. In this case, end shield A of the resistance may first discharge to the inner wall of the tank. Considering that the foreign objects inside the tank may be hidden in imperceptible crevices, when the disconnect switch is closed with power on, the over - voltage generated may, under the action of the electric field force, move the foreign objects to areas with a stronger electric field, thereby causing electric field distortion and leading to the occurrence of discharge phenomena.

4 Conclusion

Given the extensive application of advanced switchgear in the power system, accidents such as tripping of tank - type circuit breakers and GIS equipment due to foreign objects occur frequently. To prevent such faults, it is necessary to strengthen live - line detection work, especially increasing the detection frequency for circuit breakers that operate frequently. At the same time, during on - site acceptance, it should be strictly checked whether the equipment has completed 200 mechanical operations to ensure the running - in of the mechanism and avoid the adverse effects of metal debris on the operation of the equipment after commissioning.