1. Gariyar Gari
1.1 Tashar da Kungiyar Saita na Turanci 35kV GIS
An yi amfani da ZX2 gas-insulated double-bus switchgear a watan Maris 2011 kuma an yi aiki a watan Yuli 2012, tana da sauran bus voltage transformers (PTs) bi masu hukuma guda daga cikin kungiyar bus. An yi tasirin PTs bi masu hukuma guda a cikin babbanta 600 mm. An yanke PTs bi na turanci a cikin babbanta a kwanaki.
An haɗa PTs zuwa disconnectors a cikin chamber na bus na PT switchgear ta hanyar short cable plugs. An haɗa disconnectors zuwa three-phase bus ta hanyar moving contacts a cikin SF₆ fully-enclosed bus chamber. Tashar fully-enclosed bus yana rage muhimman nasarorin, kuma bus ba ta da sabbin babban bus protection. Ana koyar bus faults ta hanyar backup protection na power incoming switch.
1.2 Na'urar Aiki Idan Ma Duni Gariya
Idan ma duni gariya, an yi aiki a cikin power grid haka:
220kV System: Qiaoshi Line da Huishi Line sun yi aiki a cikin parallel da bus tie switch closed.
Main Transformer Load: No.1 main transformer ya shiga 47 MW, kuma No.2 ya shiga 14 MW.
35kV System: Unit A ta yi aiki a cikin double buses a split operation. Generator No.2, ya shiga 30.5 MW, an haɗa shi zuwa Bus II na Unit A ta hanyar Bus 1 na Unit E, hot oil interconnection line switchgears 361 da 367, kuma ta yi aiki a cikin parallel da No.2 main transformer.
1.3 Tsarin Gariya
Alamun Gariya
Gariyar Equipment
Nasara na Gariya
Babban babbanta ta fito. Phase A PT ta shida daidai, kuma plug na Phase B ta zama fractured. Zafi na iyakoki ta shida.
Secondary wires na arrester cabinet na jirgin yanki ta shida. Chamber pressure da insulation tests na bus sun zama normal.
2. Tashar Muhimmanci
2.1 Kasuwanci da Kungiyar Amfani Da Defects
2.2 Abnormal Operating Conditions
Secondary Circuit Faults
Overloading in the secondary circuit due to excessive parallel loops, resulting in increased heat generation according to \(Q = I²rt\).
Secondary short circuits triggering primary current surges and overheating.
System Overvoltage
Ferroresonance caused by switching operations or arcing grounding, generating overvoltages up to 2.5 times the rated value.
Waveform distortion accelerating insulation aging.
Three-Phase Imbalance
2.3 Manufacturer's Disassembly Analysis
Fault Location
Stress Analysis
Non-flexible cable connections generated transverse stress concentrated at flange holes.
Fault progression: Intermittent grounding → Aluminum coating ablation → Fault reset → Final breakdown.
3. Retrofit Plan
3.1 Equipment Monitoring Optimization
3.2 Structural Design Improvement
Cabinet Expansion: Increase cabinet width from 600 mm to 800 mm to improve heat dissipation.
Connection Upgrade: Replace short cable plugs with direct connections to reduce stress.
Modular Design: Adopt pluggable PTs/arresters to minimize maintenance time.
3.3 Protection System Enhancement
Add dedicated circuit breakers for PT switchgears with overcurrent/overvoltage protection.
Install dedicated bus protection devices for rapid fault isolation.
Optimize zero-sequence circuit design to reduce resonance risk.
3.4 Operation and Maintenance Strategy Adjustment
Establish full lifecycle management records for equipment, documenting installation and maintenance data.
Perform quarterly SF₆ moisture content tests with a threshold ≤300 ppm.
Conduct annual PT volt-ampere characteristic tests for comparison with factory data.
4. Lessons Learned and Preventive Measures
4.1 Key Lessons
Design Flaw: Co-location of PTs increased fault propagation risk.
Maintenance Gap: Failure to detect cumulative stress damage.
Protection Deficiency: Reliance on backup protection delayed fault clearance.
4.2 Preventive Measures
Strengthen equipment manufacturing supervision, focusing on insulation processes and structural integrity.
Promote condition-based maintenance using vibration monitoring to assess stress levels.
Revise design specifications to mandate flexible connections between PTs and buses.
Conduct anti-accident drills to standardize emergency response procedures for PT faults.
4.3 Implementation Results
Post-retrofit data shows:
Partial discharge reduced from 80 pC to 15 pC.
Temperature rise under full load decreased by 12°C.
Fault response time shortened from 600 ms to 40 ms.
5. Conclusion
This accident revealed multiple hidden risks in GIS equipment design, installation, and maintenance. Through structural optimization, protection system upgrade, and management enhancement, a comprehensive risk prevention system has been established. Continuous monitoring of equipment performance will provide replicable retrofit experience for similar substations.
