Karamin Gasu Yadda Ake Yawanci Da Kula Ƙarfin 500+ kV na Tashiyar Wadanda [Misalai]

0 Tsari
Bayanin gas da aka fuskantar zuwa shirin mai sarrafa mafi girman kofin gida na biliya yana da muhimmanci. Da samun bayanin gas chromatography, za a iya tabbatar da lafiya ko kawo karfi wajen shirin mai sarrafa mafi girma a cikin kofin gida, ya kuma zama da kyau a kan idan abubuwa masu nasara a matsayin tashin hoton sauran kirkiro ko fitaccen kawo karfi a lokacin tsohon rike, kuma ya bayyana tsari, nau'in da kuma yanayi a kan tashin hankali. Gas chromatography ta zama daya daga cikin hanyoyin da suka da amfani da su don hankalin da kuma ingantaccen adadin rayuwarsa, kuma an yi tasiri a kan hukumomin da kuma ma'aikatun kasar [1,2].

1 Misalai
Mafi girman kofin gida na farko a Makaranta Hexin ita ce model A0A/UTH-26700, da sashe 525/√3 / 230/√3 / 35 kV. An yi a ranar Mayu 1988, kuma an fara a ranar 30 ga Yuni 1992. A ranar 20 ga Satumba 2006, sabbin magana da aka yi a cikin wasu lura a takaice ya nuna "light gas relay operation on No. 1 main transformer." Bayan wannan, mafi girman da suka bar azumi sun nuna dukkukan da kuma kawo karfin shirin a kofin gida a fagen Phase B a kofin gida na 35 kV, kuma akwai gas a cikin gas relay, wanda ya ba su da shiga aiki. Idan a nan, bayanan ilimi na musamman da kuma bayanin shirin mai sarrafa mafi girman kofin gida ba suka nuna abubuwan da suka haifar da wani abu.

2 Tabbacin Gas Chromatography da Diagnosis
An kula shirin da gas a baya a bangaren shiga aiki don bayyana a cikin gas chromatography. Amfani da tabbata a cikin jikohin 1 da 2. Tabbacinta ta nuna adadin gas da ke cikin shirin mai sarrafa mafi girman kofin gida da kuma gas relay. An yi tattalin aiki da tabbacin gas chromatography da kuma equilibrium criterion method don bayyana adadin gas a cikin shirin da gas samples.

Jikohin 1 Tabbacin Insulating Oil Phase B of No. 1 Main Transformer a Makaranta Hexin (μL/L)

Jikohin 2 Tabbacin Gas from Gas Relay of Phase B of No. 1 Main Transformer a Makaranta Hexin (μL/L)

Daga Quality Standards for Transformer Oil in Service, ya kamata a duba idan wani adadin gas da ke cikin shirin mafi girman kofin gida na 500 kV ya fi shi a nan: total hydrocarbons: 150 μL/L; H₂: 150 μL/L; C₂H₂: 1 μL/L. Acetylene (C₂H₂) ta samun a cikin shirin mafi girman kofin gida da adadin φ(C₂H₂) 12.13 μL/L, wanda ya fi shi da 12 kowane. Daga bayanin component exceedance analysis [3], an samun cewa akwai abu a cikin mafi girman kofin gida.

Bayan tabbacin characteristic gases, an samun cewa akwai tashin kawo karfi da energy mai yawa, domin φ(C₂H₂) shine alamar da ke nuna hoton sauran kirkiro da kawo karfi. Daga IEC three-ratio method, an samun ratios:
• φ(C₂H₂)/φ(C₂H₄) = 1.2,
• φ(CH₄)/φ(H₂) = 0.56,
• φ(C₂H₄)/φ(C₂H₆) = 6.6,
wanda ya ba su da code 102. Wannan ya ba su da cewa akwai tashin kawo karfi mai yawa (i.e., arcing) a cikin mafi girman kofin gida.

Daga equilibrium criterion method [4] da kuma bayanin gas composition a cikin gas relay, an samun theoretical oil concentrations. An samun ratio αᵢ daga theoretical to measured concentrations a cikin shirin (da ake nuna a Jikohin 2). Daga experience a field, a nan da suka da shi, αᵢ values for most components fall within the range of 0.5–2. Amma, a lokacin tashin hakan, characteristic gases typically exhibit αᵢ values significantly greater than 2. In this case, all gas components in the gas relay showed αᵢ values much greater than 2, indicating a sudden internal fault.

Bayanan iliminta na musamman sun nuna cewa contact resistances, winding DC resistances, da maximum phase differences su ne a cikin limits. Leakage currents between windings and to ground, as well as their historical comparisons, showed no abnormalities. Dielectric loss and insulation resistance parameters were also normal. These results ruled out overall moisture ingress, major insulation degradation, or widespread insulation defects, confirming that the main insulation system was intact.

Based on comprehensive analysis of the above results, it was concluded that a sudden arcing fault had occurred inside the transformer. The concentrations of CO and CO₂ in the oil did not show significant increases, and although total hydrocarbon levels were rising, they had not yet exceeded limits. This suggested that large-scale solid insulation involvement was unlikely. However, due to the high αᵢ values for CO and total hydrocarbons, there was suspicion of a sudden discharge fault involving localized damage to solid insulation.

3 Internal Inspection and Remedial Actions
To further determine the root cause, the transformer was drained and inspected. The two 35 kV bushings and riser on Phase B were removed for examination, revealing that the voltage-equalizing grounding strip on the coil end pressure plate had been burned through. Upon lifting the tank cover, it was found that the insulating support of the upper yoke coil pressure plate had been damaged due to long-term mechanical stress, resulting in a two-point grounding. This created a circulating current, leading to arcing that burned through the grounding strip. The large volume and high rate of gas generation created significant internal pressure, causing cracks and severe oil leakage in the two 35 kV bushings near the discharge point. The inspection findings were fully consistent with the conclusions drawn from chromatographic analysis.

Remedial Measures:
• Replace the damaged insulating support components;
• Perform degassing and filtration of the insulating oil;
• Return the transformer to normal operation after successful acceptance testing;
• Enhance operational monitoring, and resume regular management only after confirming no further issues through continuous tracking and analysis.

4 Conclusion
(1) This study successfully applied gas chromatography to diagnose an internal arcing fault in Phase B of the No. 1 main transformer at Hexin Substation, providing valuable experience for the operation and fault diagnosis of large power transformers.

(2) When a transformer gas relay operates, oil and gas samples should be collected for chromatographic analysis. By combining chromatographic results, historical data, the equilibrium criterion method, and insulation tests, it is possible to determine whether the fault is internal or related to auxiliary components, and to identify the nature, location, or specific component involved. This enables timely maintenance and ensures equipment safety.

(3) Insulating oil chromatographic analysis is one of the most effective measures for monitoring the safe operation of oil-filled electrical equipment. Regular DGA allows for early detection and continuous monitoring of internal faults and their severity. To ensure the safe operation of large transformers and maintain awareness of their health status, gas chromatography should be performed in accordance with power industry standards, and the testing frequency should be increased when necessary.