Quid sunt causae collapsus et combustionis transformatoris tensionis GIS 35 kV?

1. Summarium Accidentis
1.1 Structura et Coniunctio Transformatoris Tensionis Armarii Commutationis GIS 35kV

Armarium commutationis duplici busbar gas-insulatum ZX2, fabricatum in mense Martio 2011 et officio in operationem positum iulio 2012, est configuratum cum duabus groupis transformatorum tensionis (PT) pro unoquoque sectione busbar. Duas PT groupes eiusdem sectionis busbar sunt designatae in uno armario commutationis latitudinis 600 mm. Triphasica PT sunt disposita in forma triangulari in fundo armarii.

PTs sunt coniunctae ad disiunctiones in camera busbar armarii PT per breves cables. Disiunctiones sunt coniunctae ad triphasicum busbar per contactus mobiles in camera busbar SF₆ totaliter inclusa. Structura totaliter inclusa reducit rationem defectus, et bus non est instructus cum protectione bus speciali. Defectus busbar sunt eliminati per protectionem backup interruptoris incoming power.

1.2 Modus Operationis Antequam Combustio

Antequam accidente, rete electricum operabatur ut sequitur:

• Systema 220kV: Linea Qiaoshi et Linea Huishi erant in operatione parallela cum switch bus tie clauso.

• Carga Transformeris Principalis: No.1 transformer principalis portabat 47 MW, et No.2 portabat 14 MW.

• Systema 35kV: Unitas A operabatur cum bis bus in operatione separata. Generator No.2, portans 30.5 MW, erat coniunctus ad Bus II Unitatis A per Bus 1 Unitatis E, switchgear interconnectionis olei calidi 361 et 367, et operabatur in parallelism cum No.2 transformer principali.

1.3 Processus Accidentis

• Praecursor Defectus

• A hora 15:11:20.393 die 19 Aprilis, dispositivum protectionis switch 367 Unitatis E (Unitas Bus pro Generatoribus 1 et 2) repetitissime emittebat alarmas disiunctionis PT, quae intermittenter resetabantur.

• Combustio Aparatus

• Ad horam 15:12:59, fumus et arcing observabantur in armario PT Bus 1 Unitatis E. Protectio overcurrent zero-sequence switch 361 et 367 activata est, ambo switch tripantes.

• Inspectio In Situ

• Ianus armarii erat expulsus. Phase A PT erat graviter combusta, et plug Phase B fractus. Aparatus interni erant carbonizati.

• Filiae secundariae armarii adjacentis arrestoris erant laesae. Testes pressionis et insulationis camerae busbar erant normales.

2. Analyse Causarum
2.1 Defectus Qualitatis Aparatus et Installationis

• Questio Design et Fabricationis

• Processus insulantis pigmenti infirmus ducens ad disiectam partialis.

• Laxitas laminarum ferreorum causans calefactionem eddy current.

• Coilis irregulariter avolutis augebatur periculum circuitus inter-turn short.

• Defectus Installationis et Maintenanceis

• Sutura infirma vitiis terrae augmentans resistentiam contactus.

• Deformatio nucleorum ferreorum in transportatione/installatione.

• Stress transversalis a brevibus cable plugs causans fissuras epoxy tempore.

2.2 Conditiones Abnormales Operationis

• Defectus Circuitus Secundarii

• Overloading in circuitu secundario ex nimis circulis parallelis, resultante in incremento generationis calefactionis secundum \(Q = I^2rt\).

• Circuitus secundarii short circuiting provocantes surges currentis primarii et overheating.

• Systema Overvoltage

• Ferroresonance causata a operationibus switching vel grounding arcing, generans overvoltages usque ad 2.5 vicies valorem nominalem.

• Distortio waveform accelerans senescens insulantis.

• Imbalance Triphasica

• Contentus harmonicus altus (praecipue harmonici impari) causans imbalance impedentiae.

• Current displacement puncti neutralis ducens ad calefactionem in circuitu zero-sequence.

2.3 Analyse Disassembly Manufactureris

• Locatio Defectus

• Fissura epoxy in foramine montage flange Phase A PT duxit ad grounding intermittens.

• Fractura mecanica plug Phase B triggeravit short circuit phase-to-phase.

• Analyse Stress

• Connectiones cable non flexibilis generantes stress transversalis concentratus in foraminibus flange.

• Progressio defectus: Grounding intermittens → Ablatio coating aluminum → Reset defectus → Final breakdown.

3. Planus Retrofit
3.1 Optimizatio Monitoring Aparatus

• Implementa monitoring online partial discharge pro armariis commutationis GIS eodem modello et stabilit data basica.

• Conducta testes periodicis resistentiae insulantis cum limine 200 MΩ.

3.2 Melioramentum Design Structuralis

• Expansio Armarii: Auge latitudinem armarii ab 600 mm ad 800 mm ad meliorandam dissipationem calefactionis.

• Upgrade Connectionis: Replace short cable plugs cum connectionibus directis ad reducendum stress.

• Design Modular: Adopta PTs/arrestores pluggables ad minimandum tempus maintenance.

3.3 Enhancere Systema Protectionis

• Add circuit breakers dedicatos pro switchgears PT cum protectione overcurrent/overvoltage.

• Install dispositiva protectionis bus dedicata pro isolatione rapida defectus.

• Optimiza design circuitus zero-sequence ad reducendum periculum resonantiae.

3.4 Adjustatio Strategiae Operationis et Maintenanceis

• 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. Lectiones Acquasitae et Praeventiva Medialia
4.1 Lectiones Claves

• Flaw Design: 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.