Tahalilin da kiyasin hanyar ƙarin shiga gida na GIS na 550 kV
Gas - insulated metal - enclosed switchgear (GIS) shi ne karamin abubuwa da ke cikin fadin kwalaye da take dacewar da masana'antuwa kamar circuit breakers (GCB), disconnectors (DS), earthing switches (ES), da kuma abubuwan da dama kamar voltage transformers, current transformers, surge arresters, da kuma enclosed busbars. Abubuwan da suka fi sanya wajen gurbin zafi suna cikin fadin kwalaye da ke ciki, wanda an yi tashar gas SF₆ da yake da kyau a tsari da kuma idan ya faruwa a kan harsuna. GIS na da kaya mai girma, karshen da ya gina, ya fi kyau a iya koyarwa, da kuma ba sa iya faruwa, kuma ana amfani da ita a cikin jihohin kwabtaka daidai.
550 kV GIS a 500 kV step - up substation ta kamfanon da aka sani ne ana amfani da wiring arrangement structure na double - busbar, da 2 main transformer incoming lines, 1 starting and standby transformer incoming line, 2 outgoing lines, da kuma 1 bus - tie, da suka hasashen 6 circuit breakers. Kowane 1M da 2M ana samun 1 PT bay. An yi amfani da ita a ranar 28 ga Oktoba, 2022, kuma an yi koyarwa a gida a ranar 10 ga Disamba, 2022. A lokacin handover withstand voltage test, an samu supporting insulator da ya faruwa da abin da ba daidai ba.
An yi bincike daga ma'aikata masu ilimi kamar yadda abin da ba daidai ba ya faru, na ingancin koyarwa, na tsarin rawa, tarihin ingantaccen factory, X - ray flaw detection, resin dissolution, da kuma electric field simulation. An samu sababin da supporting insulator ta faru, kuma an bayar da muhimman yanayin da za a yi don cin gwamnati da neman lafiya a cikin ingantaccen GIS.Na koyarwa a gida da na tsaftaci masu ilimi a kan gas - insulated metal - enclosed switchgear, da kuma na tsohon rikitar da aka bayyana.
Test Voltage
Ana yi amfani da 80% na rated short - time power - frequency withstand voltage value of 740 kV da masana'anta ta bayyana, wanda yake 592 kV, da tsari 1 minute.
Conditions that the Tested Equipment Should Meet
Test Method and Criteria
Voltage na tested GIS yana da kyau a cikin 0 V zuwa 318 kV, ya yi tsari 5 minutes, sannan ya zuwa 473 kV da tsari 3 minutes. Duka, an yi amfani da voltage zuwa 592 kV da tsari 1 minute. Idan ba a faruwa, an samu ita da kyau.
Searching for and Handling of Abnormal Points
Overview of the Breakdown Abnormality
A lokacin 14:03 a ranar 11 ga Disamba, 2022, an yi insulation handover withstand voltage test a kan main circuit na 550 kV GIS a substation. A lokacin an yi phases B da C, an yi voltage zuwa 318 kV da tsari 5 minutes, an samu ita da kyau. A lokacin an yi voltage zuwa 473 kV da tsari 2 minutes, an samu abin da ba daidai ba. Voltage ya zama 0 V, kuma an samu abin da ba daidai ba a substation, wanda ya haɗa test. Ba a yi amfani da takardun daidai, an samu insulation resistance to ground na 1M - C phase main circuit 400 MΩ, da kuma 200 GΩ na mafarko. Ana samun cewa akwai abin da ba daidai ba a cikin abubuwan da 1M - C phase ta da. Wiring na withstand voltage test da kuma area na abin da ba daidai ba suka samu shirhe a Figure 1. Part na blackened a figure yana nuna range na voltage - applying.
Idan a nemi Figure 1, range na voltage - applying yana ciki: 6 circuit breakers da 1M ta da, 6 bus disconnectors, 2 line - side disconnectors, 5 sets of air bushings, 1 bus disconnector na PT da 1M ta da, da kuma 6 bus disconnectors na 2M. Point na voltage - applying an samu a riser na incoming line na Main Transformer No. 2 a gida.
Process of Searching for Abnormal Points
GIS na da kaya mai kasa, da abubuwan da suka fi sanya da ƙasashe suka yi ƙungiyar. Abubuwan da 1M ta da suka da 83 independent gas compartments, wanda yana ƙarfin lokacin lokaci domin samun abin da ba daidai ba. Ba a yi amfani da takardun daidai, an yi point - by - point elimination method don haɗe area na abin da ba daidai ba.
Saboda kaya mai kasa na GIS, ba a iya samun insulation kafin a yi amfani da exposed parts, da kuma points na insulation suka ciki a 15 - meter - high riser seats a gida. Lokacin samun insulation, akwai ƙarfin da suka ƙara. Misali, mutanen da suka yi amfani da crane don ci gaba, amsa da tools don amsa, da kuma an yi amfani da test leads don samun. Ba a yi amfani da takardun daidai, an samun cewa closing na PT disconnecting switch na 1M da kuma removal na secondary ground wire na PT yana ba da kyau don amfani da PT as insulation measurement point, wanda za su iya amsa da kuma bayyana a lokacin samun insulation.
Duk disconnecting switches da suka da ƙasashe GIS 1M suka cika, da kuma circuit breakers suka da ƙasashe. Sannan, kadan kadan tun ƙasashe interval na voltage - applying point, disconnecting switches na 1M (da ba 1M VT disconnecting switch ba) suka da ƙasashe kadan kadan, da kuma insulation suka samu kadan kadan. Duka, a 5W11 outgoing line interval na 1M - C bus, an samu insulation na main circuit 400 M&Ω;. An yi amfani da takardun daidai, an samu abnormal point a cikin area daga line - side disconnecting switch na circuit breaker zuwa outdoor GIS bushing.
Area na abnormal na Figure 1 an haɗe, sannan an yi amfani da second voltage application a cikin non - abnormal parts don main insulation withstand voltage test procedure. Amfani da takardun daidai, an samu ita da kyau. Power - frequency withstand voltage tests an yi amfani da takardun daidai, da kuma an samu duk da kyau.
Handling of Abnormal Points
Akwai 5 independent gas compartments a cikin area na abnormal. Don samun abnormal point, ya kamata a yi amfani da takardun daidai, an yi amfani da gas compartments kadan kadan don samun.Saboda gas na SF₆ a cikin GIS ya zama toxic ba a yi amfani da takardun daidai, a ranar 12 ga Disamba, 2022, ba a yi amfani da takardun daidai, an yi recovery gas da kuma an yi disassembly da equipment, an samu cewa supporting insulator na three - way busbar a lower section na vertical busbar a 02 - 5 gas compartment na 1M - C busbar ta faru. Busbar conductor, casing, da kuma insulators na maza suka da kyau a cikin product technical requirements.
Masana'anta an yi replacement da abnormal insulator a ranar 13 ga Disamba, an yi reinstall da busbar, da kuma an yi amfani da gas treatment, leak detection, moisture measurement, da kuma main - circuit resistance measurement. Ba a yi amfani da takardun daidai, an samu ita da kyau, a ranar 14, an yi amfani da power - frequency withstand voltage test daidai don wiring method na test da main - circuit insulation withstand voltage test procedure. Amfani da takardun daidai, an samu ita da kyau (592 kV da tsari 1 minute).
Analysis of the Causes of Supporting Insulator Fracture
Akwai 145 supporting insulators a cikin GIS. Idan supporting insulator da ya faru yana da kyau ko yana cikin problem na batch - wide, yana da muhimmanci don safe da reliable commissioning na step - up substation. Saboda haka, don samun sababin fault insulator, an yi bincike daga ma'aikata masu ilimi kamar haka.
Inspection of Busbar On - site Assembly Quality
Busbar CX1 - 1C (factory number, the same below) an yi assembly on - site a ranar 3 ga Disamba, 2022. A lokacin assembly, on - site representative na masana'anta an yi verification kadan kadan don "On - site Docking Confirmation Operation Item Card". Owner da supervisor suka haɗa process, da kuma assembly ya yi amfani da takardun daidai bayan an yi signing formalities. Ba a yi amfani da takardun daidai, an yi on - site verification tests kamar gas moisture content, leak detection, da kuma loop resistance. Wannan ya haɗe possibility cewa insulator fracture ta faru saboda quality, process, da kuma abubuwan da ba daidai ba a lokacin assembly.
Inspection of the Material Compliance of Supporting Insulators for Busbars
Supporting insulator da ya faru ta da factory - out number Z220704 - 1G1, wanda anakawa subsidiary company na masana'anta a watan Yuli, 2022. Ba a yi amfani da takardun daidai, supporting insulator ya yi inspections da tests kamar visual inspection, dimensional measurement, vitrification temperature testing, X - ray flaw detection, da kuma electrical testing, da kuma an samu duk da kyau.
Factory - out inspection reports da incoming - inspection records na insulators suna nuna cewa both factory - out da incoming - inspection results suka da kyau a cikin requirements.
Inspection of Busbar Manufacturing History
Bincike a history na assembly na CX1 - 1C busbar unit an nuna cewa masana'anta ta faru production da assembly a ranar 20 ga Satumba, 2022, da kuma an samu work a ranar 12 ga Oktoba, 2022. Records a table na assembly history sun nuna cewa internal da external assembly processes suka da kyau a cikin technical requirements da process standards na drawings, ba a samu abin da ba daidai ba. Saboda haka, za a iya haɗe cewa processes na manufacturing history table suka haɓaka fracture na supporting insulator.
Inspection of Busbar Factory - out Tests
CX1 - 1C busbar an yi lightning impulse, power - frequency withstand voltage, da kuma partial discharge tests a factory na masana'anta a ranar 6 ga Oktoba, 2022, wanda duk suna samu da kyau, da kuma an samu results qualified. Wannan ya nuna cewa busbar da insulators suka da kyau a lokacin an fitar da factory.
Inspection of Abnormal Supporting Insulators
Binciken an yi daga ma'aikata masu ilimi kamar nature na failure na abnormal supporting insulators da kuma verification tests (including dimensional inspection, flaw detection, material analysis, etc.).
Failure Nature
Binciken na surface discharge path na insulator yana nuna cewa akwai through - damage a cikin insulating part daga high - voltage electrode zuwa low - voltage electrode. Idan insulator ta faru, yana da kyau cewa akwai defects a cikin insulating part, ko additional mechanical stress, wanda yana haɓaka cracks a cikin insulating part, da kuma through - breakdown yana faru a kan cracks.
Verification Tests
Dimensional re - inspection. Dimensional re - inspection na abnormal supporting insulator an samu da kyau. Results na re - inspection suna nuna a Table 1.
X - ray flaw detection. X - ray flaw detection an yi amfani da takardun daidai, da kuma an samu cewa ba a samu external defects saboda fracture cracks ba.Resin material re - inspection. Samples an yi amfani da takardun daidai don re - inspection da density, filler content rate, da kuma glass transition temperature, da kuma an samu duk da kyau. Resin material detection results suna nuna a Table 2.
Re - inspection of the resin - to - electrode bonding interface. Non - discharged area na insulator an yi cut, da kuma resin - to - metal bonding surface na insulator an yi dye don flaw detection. Sakamakon haka, local slight penetration na coloring agent a fracture, area na maza an samu da kyau, wanda ya nuna cewa ba a samu defects a cikin resin, da kuma resin an samu da kyau a cikin electrode.
Re - inspection of resin melting. Ba a yi amfani da takardun daidai, an yi melt resin na abnormal supporting insulator a high temperature, da kuma an yi re - inspection da electrode. Akwai local abnormal deformation a position na discharge point a arc - shaped surface na high - voltage electrode. In conclusion, during the manufacturing process of the supporting insulator, improper operation caused abnormal deformation of the arc - shaped surface of the high - voltage electrode. Since the deformation was minor, the operators failed to detect it in a timely manner, allowing defective components to enter the next process and eventually leading to the pouring of the insulator.
This failure was caused by non - standard operation of the operators, which led to abnormal deformation of the electrode and subsequent fracture of the insulator. The structure of this supporting insulator is an insulation structure that the manufacturer has been using. Since 2003, more than 36,000 insulators have been manufactured and are operating reliably in the field. Therefore, the fracture of this supporting insulator is an isolated case.
Simulation Verification
For safety reasons, simulation verification was carried out on the busbar with this insulator structure.Voltage application: The central conductor and the high - voltage electrode of the insulator are at 1675 kV, while the casing, support base, and low - voltage electrode of the insulator are at 0 potential.
Judgment criteria: Under the minimum functional gas pressure of 0.45 MPa, the surface - flashover electric field strength of the insulator should not exceed 12 kV/mm, and the electric field strength of the high - voltage electrode of the insulator should not exceed 50 kV/mm.
The simulation results show that the maximum surface - flashover electric field strength of the insulator is 10.5 kV/mm, which is less than 12 kV/mm, and the result is qualified. The maximum electric field strength on the surface of the high - voltage electrode is 21.2 kV/mm. Converted to the condition of a power - frequency voltage of 318 kV, the maximum electric field strength is 40.2 kV/cm, which is less than 50 kV/cm, and the result is also qualified.
The 550 kV GIS of the 500 kV step - up substation was successfully energized for the first time on December 28, 2022. Unit 2 was connected to the grid for the first time on November 29, 2023. All equipment in the substation has withstood the pressure test and is operating normally.
Conclusion
For important high - voltage equipment of 110 kV and above, it is necessary to strictly follow the relevant requirements of DL/T 586—2008 "Technical Guidelines for Supervision of Power Equipment Manufacturing" to strengthen the factory - based supervision of equipment and control the manufacturing quality of equipment from the source. GIS manufacturers must enhance their quality control awareness, comprehensively sort out the quality - related risk points at each post, and improve documents such as operation specifications, operation standards, and operation procedures for product assembly at all voltage levels. Comprehensive control should be carried out over links such as component procurement, product design, component processing technology, incoming inspection, product assembly, testing, and on - site installation to ensure the safety, stability, and reliability of products.
