Casus Analyse de Mala Operatione Relai Protectionis Overcurrent Transformatoris Grounding

Modus neutralearthing referre ad connexionem inter punctum neutrum systematis electricitatis et terram. In systematibus Sinensium 35 kV et inferius, methodi communes includunt neutrum non-terratum arcu-suppressionis bobina terren et parvi-resistens terren. Modus non-terratum latissime utitur quia permittit operationem brevem tempore defectus uniphasalis, dum parvi-resistens terren propter celerem remotionem defectus et limitationem overvoltage factus est mainstream. Multae substationes installant transformatores terrenos ad renovandum neutrum terren, sed mutatae characteristicae defectus affectant protectionem relais, periculum maloperationis vel refusi.

Hoc scriptum introducit principia et characteristica transformatoris terreni, explicat configurationem/setting protectionis currentis in systematibus parvi-resistentis, analizat causas maloperationis, et exemplificat casum uniphasalis terreni ad dissecandum actiones protectionis et radices deficiendi. Praebet reference pro gestionibus/praeventione defectuum, profundificat intellectum personarum maintenance, augit efficientiam troubleshooting, et eliminat potentialia pericula.

Principium Operationis Transformatoris Terreni

Durante transformatione substationis cum systemate delta-connecto, neutro non-terreno in systema parvi-resistentis, ad introducendum punctum neutrum, praxis communissima est addere transformator terreni ad busbar. Nunc, generaliter selectus est Z-typus transformator terreni ad introducendum punctum terreni. Sequitur analysin principii operationis Z-typus transformatoris terreni.

Z-typus transformator terreni structura similis est transformatori electricitatis ordinario. Tamen, avolutio in corde cuiusque phasalis dividitur in duas partes aequalis numeri spire, superiore et inferiore, quae connectuntur in forma zig-zag. Methodus eius connectionis ostenditur in Figura 1.

Quando defectus terreni breve circuitum occurrit, currus zero-sequenciales fluit via puncti neutri. Connectionis zig-zag Z-typus transformatoris terreni facit ut currus zero-sequenciales superioris et inferioris avolutionis opponantur, cancellantes fluxus magneticos et minimizando impedimentum zero-sequenti ad vitandam overvoltage arcu-terreni excesivam. Pro curribus positivis/negativis-sequentibus, proprietates electromagneticae sicut transformatoris ordinarii creant impedimentum altum, restrictive fluitus eorum.

Sub normali operatione, transformator terreni operatur circa sine onere (nulla onera secundaria). Durante defectu terreni, curru defectus positivi, negativi, et zero-sequentiales transibunt per ipsum. Owing to "high positive/negative-sequens, low zero-sequens impedimentum", dispositivum protectionis principaliter mensurat currum zero-sequenti grid.

2 Configuratio et Analysin Protectionis Currentis pro Transformatoribus Terrenis

Protectionis currentis transformatoris terreni typice usatur phase-to-phase et zero-sequens protectionis currentis. Hic est deconstruction:

2.1 Setting Phase-to-Phase Current Protection
2.1.1 Principia Setting

Haec protectio includit instantaneam trip et over-current protection:

• Instantaneous Trip: Coordinare cum backup over-current protectione transformatoris power supply ipsilateralis. Assecura sensibilitatem durante defectibus biphasalibus (minima operationis modus) et evita currents inrush (7–10× rated current transformatoris terreni) et currents defectus lateris low-voltage.

• Over-Current Protection: Set ad evitandum rated current transformatoris terreni et maximum current defectus phasalis externo durante defectus uniphasalis terreni, assecurans fiduciam.

• Operational Logic: Instantaneous trip agit immediate (nulla mora); over-current protection (backup pro defectibus phase-to-phase) habet moram brevem et setting minores pro coordinatione gradatim.

2.1.2 Modus Tripping

Basati in connectione transformatoris terreni ad transformator power supply:

• Connectus ad busbar low-voltage: Instantaneous trip/over-current protection trippit circuit breaker ipsilateralis ad isolandum defectus celeriter.

• Connectus ad lead low-voltage: Protectio trippit circuit breakers omnilateralis ad sectandum viam defectus et praeventionem escalationis.

2.2 Setting Zero-Sequence Current Protection for Earthing Transformers
2.2.1 Principia Setting

• Valorem setting currenti debet assecurare sufficientem sensitivitatem quando defectus uniphasalis ad terram occurrit.

• Cooperare cum valore setting long-delay protectionis pro sensitivitate full-line protectionis zero-sequenti inferioris.

• Pro primo limite temporali zero-sequenti, consideranda sunt ad evitandum successivam occurrence defectus uniphasalis ad terram in duabus lineis.

• Tempus operationis debet esse longius quam maximum tempus operationis Section II zero-sequenti cuiusque componentis coniuncti bus.

Cum protectionis zero-sequenti transformatoris terreni non serviat ut protectionis principalis, sunt tres limites temporales, qui ostenduntur sequenter:

In formula: \(t_0^1\), \(t_0^2\), \(t_0^3\) sunt primus, secundus, et tertius limites temporales protectionis zero-sequenti transformatoris terreni respectiviter; \(t_{0\text{I}}'\) est valor setting temporis Section I zero-sequenti lineae emissariae; \(t_{0\text{II}}'\) est maximus valor setting temporis Section II protectionis zero-sequenti omnium equipmenti in busbar excepto transformatore terreni; \(\Delta t\) est set 0.2 - 0.5 s.

2.2.2 Modus Tripping

• Quando transformator terreni connectus est ad busbar correspondingem substationis, protectionis zero-sequenti operatur: primus limes temporis trippit circuit breaker bus tie vel section circuit breaker et bloccat dispositivum automatic standby power supply input (breviter "automatic standby input"); secundus limes temporis trippit circuit breakers ipsilateralis transformatoris terreni et power supply.

• Quando transformator terreni connectus est ad lead correspondingem power supply, protectionis zero-sequenti operatur: primus limes temporis trippit circuit breaker bus tie vel section circuit breaker et bloccat automatic standby input; secundus limes temporis trippit circuit breaker ipsilateralis power supply; tertius limes temporis trippit circuit breakers omnilateralis power supply.

2.3 Analysis of Current Protection Operation for Earthing Transformers

Analysis configurationis protectionis transformatoris terreni ostendit significativas differentias inter modos tripping protectionis phase-to-phase et zero-sequenti: protectionis zero-sequenti bloccat auto-standby input durante operatione, dum protectionis phase-to-phase non.

Si currus zero-sequenti mensuratus ab dispositivo protectionis attingit valorem operationis et defectus terreni occurrit (cum transformator terrenus sit unicam viam zero-sequenti in systema parvi-resistentis), dispositivum detexit defectum sed non potest localizare. Si defectus est in linea emissaria, postquam protectionis trippit transformator terrenus, auto-standby input switchit ad busbar standby. Si busbar standby recloses ad lineam defectus, transformator terrenus in eo adhuc detexit currum zero-sequenti, provocans iterum trip. Quoniam auto-standby input nondum finivit charging, ambitus outage potest expandi. Ergo, protectionis zero-sequenti debet bloccare auto-standby input.

Quando protectionis phase-to-phase operatur (sed non protectionis zero-sequenti), dispositivum iudicat defectum short-circuit phase-to-phase in ipso transformatore terreno. Trippit transformator terrenus, parallel-trippit circuit breaker ipsilateralis power supply, et auto-standby input switchit ad busbar standby. Quoniam defectus est in transformatore terreno trippito, busbar standby reconnectit ad lineam normalem, restituendo electricitatem.

In summa, protectiones phase-to-phase et zero-sequenti transformatoris terreni differunt magnopere in iudicio causae et locationis defectus, requirunt distincta setting et configurationes. Tamen, durante defectu terreni breve circuitum, protectionis phase-to-phase potest maloperare propter componentes zero-sequenti mensuratos. Data logica diversa auto-standby input, maloperatio potest expandere ambitum defectus vel etiam causare blackout totius substationis.

3 Case Analysis
3.1 Processus Defectus

Diagramma primary wiring substationis 110 kV ostenditur in Figura 2. Ante defectum, circuit breaker 018 lateris low-voltage Transformer 1 clausus erat, circuit breaker 032 lateris low-voltage Transformer 2 clausus erat, et circuit breaker 034 erat in positione test.

Die 30 Iulii 2023, hora 06:14, protectionis over-current I section No. 2 earthing transformer activavit, trippit circuit breaker No. 2 earthing transformer 022. Simul, interlocktus est ad cuttendum circuit breaker 032 lateris low-voltage Transformer 2, causans amissionem electricitatis in busbars 10 kV Section II et III. Dispositivum automatic standby power supply (auto-standby) operavit ad claudendum circuit breaker 10 kV Section I/II bus tie 020.

Hora 06:36, protectionis over-current I section No. 1 earthing transformer activavit, trippit circuit breaker No. 1 earthing transformer 015 et interlocktus est ad cuttendum circuit breaker 018 lateris low-voltage Transformer 1, ducens ad amissionem electricitatis in omnibus busbars 10 kV Section I, II, et III. Dispositivum auto-standby tum clausit circuit breaker 032 lateris low-voltage Transformer 2 et circuit breaker No. 2 earthing transformer 022. Tamen, defectus persistit, provocans iterum protectionis over-current I section No. 2 earthing transformer. Circuit breaker 022 trippit et interlocktus est ad cuttendum circuit breaker 032, ultime causans completam amissionem electricitatis in systema 10 kV substationis.

3.2 Resultati Inspectionis Equipmenti In Situ
Inspectionis equipmenti primarii resultati:

• Corpus transformatoris terreni: Nulla abnormalitas inventa in No.1 et No.2 transformatoribus terrenis, sine manifestis vestigiis defectus in avolationibus aut coribus.

• Interval PT 10 kV Section III (switchgear 040):

• Manifestae maculae aquae in tegmine superiori cabinet switchgear, indicantes infiltrationem pluvialis.

• Severa ablatio in positione C-phase shutter baffle handcart chamber, cum duobus foraminibus in shutter superiori.

• C-phase upper contact box et static contact cremati et damni, cum aqua liquida collecta in box.

• Arc burn marks in C-phase upper/lower moving contacts arrester handcart, annealed springs, et damni insulating cylinders contact arm.

• Outer insulating sleeve C-phase bus in bus chamber combusta et fissura. Penetratio macularum aquae observata in area C-phase backplate bus chamber, et guttae aquae condensatae in sensor live display.

• Quantum parvum aquae collectum in fundo voltage transformer chamber, tres PTs phasales nullas manifestas externas abnormalities ostenderunt.

Pluvialis infiltratio ex steel support supra 10 kV Section III bus PT chamber penetravit switchgear, degradans insulationem et causans discharge C-phase evolvendo in metallic ground fault. In systema parvi-resistente, No. 2 earthing transformer detectavit curru zero-sequenti ~4.3 A/phasalis (excedens setting 2.5 A overcurrent I-section), provocans tripping. Overcurrent protection non bloccat 10 kV auto-standby, ducens ad repetitiones operationum. Ultimus trip reliquit auto-standby non-charged, causans completam amissionem 10 kV.

Factor contribuens key: Verbum control "phase current zero-sequens cancellation" erat disabilitatum (set ad "0"), praeventans software filtering componentum zero-sequenti in currentibus phasalibus. Cum 13 A currus zero-sequenti, overcurrent protection maloperavit. Proprie enabled, hoc control praeventisset defectum. Insteade, zero-sequenti overcurrent protection I-section (set ad 1.4 A) operavit: 1st time-limit tripped bus tie et bloccavit auto-standby; 2nd time-limit tripped earthing et main transformer breakers, isolating Sections II/III while Section I remained powered.

Causa radicans: Verbum control zero-sequenti cancellation disabilitatum permisit misinterpretationem currentis phasalis.

4 Conclusio

Hoc scriptum delineat setting protectionis transformatoris terreni, analizat pericula maloperationis sub curribus zero-sequentibus altis, et praebet studium casus. Ad praeventionem recurrence:

• Enable features software-based zero-sequenti cancellation (e.g., verbum control "phase current zero-sequenti cancellation") in systematibus parvi-resistentis.

• Si tales features non sunt disponibiles, optimiza coordinationem inter setting overcurrent et zero-sequenti protectionis.

Key takeaway: Proactiva configuratio software protectionis critica est ad praeventionem maloperationum durante defectibus terreni.