Protections Aerei – Defectus et Dispositiva Protectionis

Communes Defectus in Lineis Aereisque

Causae maximae defectuum in lineis aereisque sunt:

• Impactus Externi: Collisio aeroplani et incidentia vehicularia quae laedunt lineas et structuras supportantes.

• Interferentia Faunae: Aves et animalia causantes perturbationes, sicut sedendo ita ut interficiant componentes electricos vel creent circuitus breves.

• Degradatio Isolatorum: Isolatores contaminati, qui possunt ducere ad defectus electricos.

• Problema Meteorologicum: Accumulatio nimia glaciei et nivis quae onerat lineas, et fulgura quae possunt laedere apparatus.

• Phenomena Electrica: Discharge parcialis (corona) non controlata quae potest gradualiter deteriorare integritatem lineae.

• Damage Isolatorum: Isolatores perforati vel fracti, compromittentes insulationem electricam lineae.

• Ingressio Vegetationis: Arbores crescendo nimis prope lineas, potentialiter facientes contactum et causantes defectus.

• Tensio Ventorum: Venti fortes qui possunt nutare lineas, causantes damnum mechanicum vel circuitus breves.

Articulus Relativus: Protectio & Defectus Transformatoris Electrici

Apparatus Protectionis Lineae Aereae

• Lineae Aereae Basi Voltaginis (LV): Fusi vel interruptores circuiti sunt usi ad tueri contra overcurrents, praebentes protectionem basicam systematis basi voltaginis.

• Lineae Aereae Mediae Voltaginis (MV): Relays overcurrent (sicut 50, 50N, 51, 51N, 67, 67N) connecti ad current transformers (CT) sunt communiter usi. Hi relays monitorant fluxum currentis et tripunt interruptores circuiti quando overcurrents abnormalis deteguntur.

Protectio overcurrent temporis graduata inefficax est pro lineis aereis transmissionis altae voltaginis (HV). Hoc est propter praesentiam plurium fontium interconnectarum fault currents, quae possunt restrictari per limitatores fault current. Requisiti claves pro schematis protectionis in lineis aereis transmissionis HV sunt sequentes:

• Detectio Defectus: Systema protectionis electricum debet esse capax identificandi omnes defectus occurrentes in linea protegente prompte.

• Discriminatio Defectus: Debet esse capax distinguendi inter defectus in linea protegente et defectus in lineis adjacentibus, bus, transformatoribus, et alio apparatu connecto.

• Eliminatio Celeris Defectus: Defectus debent eliminari intra minus quam 1 secundum ne systema electricum instabile fiat.

• Reliability: Systema protectionis debet esse altissime fidendum, assecurans quod possit eliminare defectus etiam si unum ex apparatu deficiat.

Ad haec requisita implenda, hi apparatus protectionis sunt communiter usi in lineis aereis HV:

• Protectio Differentialis et Comparativa Phasalis

• Protectio Distancialis

Protectio differentialis saepe applicatur ad lineas aereas breves, protectio distancialis autem magis convenit lineis aereis longis. Classificatio lineae aereae ut brevis vel longa fit per comparationem inductivitatis, resistentiae, et capacitatis lineae. Linea brevis habetur cum resistencia et capacitatis eius negligibiles sint comparate ad inductivitatem. Haec aestimatio saepe fit per diagrammam π lineae aereae.

Plures factores influunt impedimentum lineae, responsionem physicam eius ad conditiones circuiti brevis, et currentem charging lineae. Hi includunt nivellum voltaginis, constructionem physicam lineae transmissionis, typum et magnitudinem conductorum, et spatium inter conductores. Praeterea, numerus terminorum lineae afficit fluxum currentis load et defectus, quod systema protectionis debet considerare. Lineae parallelae quoque impactant relaying, quia coupling mutuum potest affectare currentem ground mensuratum ab apparatibus protectionis. Praesentia transformatorum tapped vel dispositiva compensationis reactiva, sicut series capacitor banks vel shunt reactors, ulterius influunt selectionem systematis protectionis et settings apparatus protectionis. Itaque, studium detailatum lineae aereae necessarium est ad determinandum protectiones relays optima. Generaliter, linea longitudine usque ad 80 - 100 km potest haberi ut brevis, licet hoc variare possit secundum nivellum voltaginis et characteristics network.

Circa 90% defectuum lineae aereae sunt transientes natura. Defectus possunt categorizari ut sequitur:

• Phase - to - Earth: Defectus ubi una phase facit contactum cum terra.

• Phase - to - Phase: Defectus occurrens inter duas phases.

• Phase - to - Phase - to - Earth: Combinatio defectus phase - to - phase et phase - to - earth.

• Three - Phases: Defectus involvens omnes tres phases simul.

Pro talibus defectibus, singulus trip pole potest requiri, permitens lineam restituendam ad servitium statim post tripping interruptores circuiti. Proinde, singuli schemata trip pole et auto - reclose communiter usi sunt in interruptoribus circuiti associatis cum lineis aereis transmissionis (solito cum voltagine 220 kV vel maiore). Quando interruptores circuiti interrumpunt currentem defectus, arcus flashover extinguetur, et aer ionizatus dissipatur. Auto - reclosing saepe successu est post moram paucorum cyclorum. Tamen, quando opus energizatum perficitur, dispositiva reclosing automatica in lineis sub opere debent poneri in modum non - reclosing. Interruptores circuiti usi in his applicationibus debent specialiter designari ad hanc operationem gerendam et immunes esse ad pole inconstancy donec ordo definitivus trip edatur.

Protectio Differentialis et Comparativa Phasalis

Protectio differentialis fundatur in lege Kirchhoff de currente. In contextu lineae transmissionis, operatur comparando currentem ingredientem lineam in uno terminali cum currente egressu lineam in altero terminali. Relays differentiales lineae in utroque extremitate lineae transmissionis commutant data de currente lineae per link communicationis fibrae opticis. Hoc link saepe constituitur per Optical Power Ground Wire (OPGW) cable, qui etiam ad designum protectionis fulminis lineae aereae usus est et continet fibrae opticis in structura sua. Figura 1 illustrat diagrammam systematis protectionis differentialis.

Figura 1 – Diagramma Protectionis Differentialis Lineae Aereae
Aliud systema relaying protectionis pro lineis transmissionis altae voltaginis (HV), quod fundatur in principio protectionis differentialis et nunc usum est etiam pro lineis longis, est protectio comparativa phasalis.
Hoc systema operatur comparando angulum phasalem inter currentes in duobus extremis lineae protegente. In casu defectus externi, currentis ingrediens lineam habet idem angulum phasalem relativum ut currentis egressus lineam. Quam ob rem, relays comparativi phasales in utroque terminali regunt parvum vel nullum differentiam anguli phasalis. Consequentia, systema protectionis manet stabilis, et non occurrit tripping. Contrario, in defectu interno, currentis fluit in lineam ab utrisque extremis, causans disparitatem anguli phasalis quae relays comparativi phasales detectare possunt. Post identificationem huius differentiae, relays activantur ad isolandum et eliminandum defectum.
In schematis comparativis phasalibus, relays initiatores partem crucialem agunt. Hi relays initiatores incipiunt processum comparativum phasalis simul atque conditio defectus detegitur. Designum eorum operari certificat pro defectibus internis et externis, praebens monitoring comprehensivum.
Ad effectivam functionem protectionis comparativae phasalis, canalis communicativus fidelis indispensabilis est. In applicationibus modernis, fibrae opticis integratae in cabled Optical Ground Wire (OPGW) factae sunt electio praeferenda ad constituendum hoc link communicativum.
Figura 2 depictat diagrammam unilineam systematis Merz Price voltage balance, qui ad protectionem lineae tris phase utitur.

Protectio Comparativa Phasalis et Protectio Distancialis
Protectio Comparativa Phasalis
Figura 2 – Diagramma Protectionis Comparativae Phasalis

In protectione comparativa phasali, transformatores currentis (CTs) identici strategicamente ponuntur in unicuique phase in utroque extremitate lineae transmissionis. Utraque pars CT, unus in utroque extremitate lineae, connectitur in serie cum relay. Sub normalibus, non - defectuosis conditionibus, voltages secundariae generatae a his CTs aequalis sunt magnitudine sed oppositae directione, effecte se invicem compensantes.

Durante operatione systematis sanis, currentis ingrediens lineam in uno extremitate precise concurrit cum currente egressu eam in altero extremitate. Quam ob rem, voltages aequales et oppositae inducantur in secundariis CTs in duobus terminis lineae. Hoc equilibrium tensionis assecurat quod nullus currentis fluit per relays, stabilitatem systematis protectionis maintinens.

Tamen, quando defectus occurrit in puncto sicut F in linea, ut illustratur in Figura 2, distributio currentis turbatur. Specificiter, currentis multo maior fluit per CT1 comparativus CT2. Hoc disparitas in currente facit secundarias voltages CTs inaequales. Consequentia, currentis circulans constituitur, fluens per pilot wires et relays. In responsione ad hunc currentis fluxum, interruptores circuiti in utroque extremitate lineae triggeruntur ad aperiendum, prompte isolantes lineam defectam ab reliquo systemate electrico.

Legi etiam: Protectio Primaria et Secundaria vel Backup in Systemate Electrico

Protectio Distancialis

Protectio distancialis dependet a relays distanciali, qui metiunt impedimentum lineae transmissionis analysando signa tensionis et currentis applicata ad eos. Quando defectus occurrit in linea, duo mutamenta significativa eveniunt: currentis surge ad multo altior nivellum, et tensio cadit precipue.

Dato quod impedimentum lineae transmissionis directe proportionalis est longitudini eius, relays distanciales designantur ad metiendi impedimentum usque ad punctum praedeterminatum notum ut "reach point." Hi relays, saepe appellati relays impedientiales, calculant impedimentum usque ad legem Ohmi, expressa per formulam Z = U/I, ubi Z repraesentat impedimentum, U tensio, et I currentis.

Relays distanciales ingeniantur ad operari exclusiva pro defectibus quae occurrunt inter locum relay et selectum reach point. Hoc design feature permittit eis efficaciter distinguere inter defectus in diversis sectionibus lineae. Impedimentum apparent calculatum a relay tunc comparatur cum praesetto reach point impedimento. Si impedimentum mensuratum minor est quam reach point impedimentum, infertur quod defectus existit in linea inter relay et reach point. Quando calculatum impedimentum cadit intra setting reach relay, relay activatur, initiando actionem protectionis.

Ad assecurandam protectionem comprehensivam, systemata protectionis distancialis installantur in utroque extremitate lineae transmissionis, et link communicativus constituitur inter hos finales, ut depictum in Figura 3. Haec communicatio permittit operationem coordinatam relays in utroque extremitate, augmentans efficaciam totalem schematis protectionis.

Performantia et Characteristica Relays Distancialium
Figura 3 – Diagramma Protectionis Distancialis Lineae Aereae

Performantia relays distancialium principaliter evaluatur secundum duos parametras claves: accuratia reach et tempus operationis.

Accuratia Reach

Accuratia reach involvit comparationem actualis ohmic reach relays distancialis sub conditionibus realis, practica cum suo praesetto valorem ohmic. Hic metricus significanter influetur a nivello voltaginis applicata ad relay durante conditiones defectus. Tensio inferior vel distorta potest ducere ad inexactitates in mensurato impedimento, affectans ability relay correcy identificare locationem defectus intra suum designatum reach. Praeterea, technicas mensurandi impedimenti usitatas in specificis designibus relays ludunt partem crucialem. Algoritmi et configurationes hardware varii possunt producere diversos niveles precisionis, consequenter impactantes accuratiam reach totalis relay.

Tempus Operationis

Tempus operationis relays distancialis est quantitas variabilis quae dependet a multis factoribus. Magnitudo currentis defectus habet effectum directum; currentes defectus maiori potest aliquando causare operationem celeriorem, dum currentes minores fortasse resultent in response tempora longiora. Positio defectus relativus ad setting relay quoque importat. Defectus propinquiores ad fontem vel intra certam proximitatem ad relay possunt triggerare responsionem celeriorem comparate ad illos ultra remoti. Praeterea, punctum in wave tensionis in quo defectus occurrit potest introducere variabilitatem in tempus operationis.

Quaedam errores transitori signalis mensurandi, qui associantur cum specificis technicis mensurandi usitatis in designo relays, possunt ulterius complicare res. Exempli gratia, errores generati a Capacitor Voltage Transformers (CVT) vel saturating Current Transformers (CT) possunt significanter retardare operationem relay, praesertim pro defectibus occurentibus propinqui reach point. Huiusmodi errores transitori possunt distorquer tensionis et currentis signa, ducendo ad misinterpretationem impedimenti et subsequentem moram in activatione relay.

Characteristica Relays Distancialium

Characteristica relays distancialium, saepe appellata forma protectionis, graphic representantur ut functio resistance (R) et impedimenti (X) lineae in diagramma R/X vel admittance. Duas formae typicae sunt circular (characteristic mho) et quadrilateral. Has formas characteristicas illustrant Figures 10 et 11, respective. Ut forma suas proprias habet advantagia et est designata ad optimizandum performantiam relay sub diversis conditionibus systematis electrici, praebens means fidelem distinguendi inter conditiones operationis normales et defectus reales intra sectionem lineae protegente.

Figura 4 – Characteristic mho

Characteristica, Setting Reach, et Reclosing Relays Distancialium
Figura 5 – Characteristic Quadrilateral

Elementum impedientiale mho nominatur ex sua characteristica appearance in diagramma admittance, ubi manifestatur ut linea recta. Tamen, characteristica impedientialis polygonal, sicut forma quadrilateral, obtinuerunt popularitatem significativam. Hae characteristicae offerunt flexibilitatem remarcabilem in covering impedimenta defectus pro defectibus phase et earth. Haec adaptabilitas fecit eas electionem praeferendam pro plerisque modernis relays distancialibus.

Relays distanciales possunt configurari cum usque ad quinque distinctis zonis, quibusdam quae sunt set ad measuring impedimentum in directione reversa. Haec reverse - measuring zones servunt ut backup protection pro bus bars. Unica zona associatur cum specifico tempore actuationis pro relay, permittens responsionem nuances et coordinatam ad defectus occurrentes in diversis locationibus intra systema electricum protegente.

Quando relays distanciales installantur in utroque extremitate lineae transmissionis, tempora eorum responsionis ad defectus variat secundum distantiam puncti defectus (F) ab utroque extremitate lineae. Exempli gratia, consideretur linea aerea connectens Substations A et B. Relay distancialis situs in statione proximiori ad punctum defectus F prius defectus detectabit, et circuit breaker correspondens tripabit antequam ille in altera statione.

Ad prohibendum defectus short - circuit a continuando recipere potentiam ab extremitate opposita lineae donec relevans protectionis distancialis activetur, link communicativus inter relays protectionis essentialis est. Saepe, haec communicatio constituitur via fiber optic cables integrated within Optical Ground Wire (OPGW) cables. Hoc setup permittit simultaneous tripping of both circuit breakers, ensuring rapid and effective isolation of the faulty section.

Impracticabile est programmari relay impedientiale ad accurate metiendi impedimentum lineae usque ad breaker in remote end. Hoc est propter errores et inexactitates inherentes in componentibus sicut current transformers (CTs), voltage transformers (VTs), ipsos relays, et in calculationibus impedimenti lineae. Ad account for these uncertainties, the relay's reach is set to measure an impedance value less than the total impedance corresponding to the full length of the line. For example, setting Zone 1 to cover up to 85% of the line's impedance is a common and safe practice. The remaining 15 - 20% serves as a safety margin, effectively preventing Zone 1 protection from over - reaching the protected line due to measurement errors and inaccuracies. Without this margin, there would be a risk of losing the ability to discriminate between faults on adjacent line sections, particularly when dealing with fast - acting protection schemes.

Careful calibration of the reach settings and tripping times for each measurement zone is crucial for achieving proper coordination among distance relays across the power system. This meticulous adjustment ensures that faults are cleared in the correct sequence, minimizing disruptions and maintaining the stability of the electrical grid.

Related Read: Introduction to Harmonics – Effect of Harmonics on Power System

Reclosing

As discussed in Section 4.2, the majority of faults on overhead lines are asymmetric and transient in nature. Auto - reclosing, a critical functionality in power systems, is executed by an auto - recloser relay. This relay is triggered by the protection devices of the overhead line, as illustrated in Figure 6.

Auto - Reclosing in Power Systems
Figure 6 – Auto - Recloser Relay

The decision to reclose an electrical line is influenced by numerous factors. Input and guidance from planning and operational teams are essential for determining the most suitable reclosing practices tailored to the specific requirements of a utility company and its region. Key considerations for transmission - level reclosing include:

Major Considerations

• System Stability: Maintaining the stability of the power grid is crucial. Reclosing decisions must account for how the action will impact the overall dynamic behavior of the system, including frequency and voltage stability.

• System Security: Ensuring the security of the electrical infrastructure is paramount. Reclosing should not expose the system to unnecessary risks that could lead to cascading failures or widespread outages.

• Continuity of Service: Minimizing disruptions to power supply for consumers is a primary goal. Reclosing can help restore service promptly, but it must be balanced with other operational considerations.

Key Parameters of Auto - Reclose Schemes

The most critical parameters of an auto - reclose scheme are:

• Dead Time: The interval between the opening of the circuit breaker due to a fault and the initiation of the reclosing attempt.

• Reclaim Time: The time required for the system to recover and be ready for a subsequent reclosing operation if the first attempt fails.

• Single or Multi - Trip: Determines whether the system will attempt a single reclosing operation or multiple attempts after a fault.

These parameters are influenced by several factors:

• Type of Protection: Different protection systems may have specific requirements or limitations that affect the reclosing parameters.

• Type of Switchgear: The characteristics and capabilities of the switchgear, such as its operating speed and endurance, play a role in setting the reclosing parameters.

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