Comparatio unitatum anularium principalium isolatarum gas SF6 et unitatum anularium principalium solidis isolatarum

Introductio
Nunc, circuitus principis insulati SF6 (deinceps "SF6 RMUs" appellandi) dominatur in mercato. Tamen, gas SF6 agnoscitur inter primarios gases horti vitrei. Ad protegendum et restringendum emissiones, eius usus debet minui et restrigi. Emergentia circuituum principis insulati solidi (RMUs) solvit problemata associata cum SF6 RMUs, addens multa nova characteristica.

​1 Distributio Circuli Principis et Circuitus Principis Insulati (RMUs)​​
Processus "urbanizationis" ponit semper crescentes exigentias in fide distributionis electricitatis. Plures usus requirent duos (vel plures) fontes electricitatis. Usus systematis "radialis" potest ad difficultates in installatione cabling, diagnosticando defectus, et inconviniendo in renovationibus et expansionibus gridis. Contra, "distributio circuli principis" commodius potest praebere duos (vel plures) fontes electricitatis pro oneribus essentialibus, simplificat lineas distributionis, facilitat routing cables, reducit necessitatem switchgear, minuit rata defectus, et facilius identificat puncta defectus.

​1.1 Distributio Circuli Principis​
Distributio circuli principis refertur ad systema ubi duo (vel plures) ductus ex differentibus substationibus vel differentibus busbaris in eadem substatione interconnectuntur ad formandum circulum pro distributione. Eius advantage sunt: quod unusquisque ramus distributionis potest accipere electricitatem a principali ductu a sinistra parte vel a principali ductu a dextra parte. Hoc significat, si defectus occurrat in uno principali ductu, electricitas potest continuari ab altera parte. Licet esset distributio unius circuitus in essentia, unusquisque ramus distributionis efficaciter obtinet beneficia similis ad distributionem duorum circuituum, significanter meliorans fidem. Leges in China praescribunt ut principalis connection circuli in urbibus sequatur "Criterium Securitatis N-1". Hoc significat, si sint N onera in linea, quandoquidlibet unum onus experiat defectum, systema potest acceptare transferentem onus, securans ut reliqua "N-1" onera continue recipiant electricitatem absque interruptione aut shedding.

​1.2 Methodi Connectionis Circuli Principis​

• ​Connection Circuli Standard:​​ Supplied by a single source, forming a ring through the cables themselves, ensuring reliable power supply to all other loads when a section of cable fails.
• ​Ring Connection from Different Busbars:​​ This connection has two power sources, typically operated in open-loop, offering higher supply reliability and greater operational flexibility.
• ​Single Ring Connection:​​ Power sources are taken from different substations or two busbar sections. When any cable section in the network is under maintenance, it does not cause any load outage.
• ​Double Ring Connection:​​ Each load can receive power from an independent ring network, providing very high reliability.
• ​Dual Source Double "T" Connection:​​ Two cable circuits are connected from different busbar sections. Each load can draw power from both cables. This method essentially achieves no outage for dual-source users and is particularly suitable for certain critical users.

​1.3 Circuitus Principis Insulati (RMUs) et Eorum Characteristica​
RMUs referuntur ad armarios switchgear pro distributione circuli principis. Typi armarii includunt commutationes oneris, interruptores circuiti, combinationes commutationis oneris + fusoris, apparatus combinationis, bus couplers, unitates mensurae, transformatores tensionis (VTs), etc., vel quaelibet combinatio vel extensio earum.

RMUs feature a compact structure, small footprint, low cost, easy installation, and short commissioning times, meeting the requirement for "equipment miniaturization". They are widely used in residential complexes, public buildings, small & medium enterprise substations, secondary switching stations, compact substations, and cable junction boxes.

​1.4 Typi RMU​

• ​Air-Insulated RMUs:​​ Use air as the insulation medium. They have a large footprint and volume, and are susceptible to environmental influences.
• ​SF6 RMUs:​​ Use SF6 gas as the insulation medium. The main switch is enclosed within a sealed metal shell filled with SF6 gas, with the operating mechanism located outside the shell. Due to the sealed enclosure, they are unaffected by the external environment. Their volume is significantly smaller than standard air-insulated RMUs, making them the most commonly used type currently.
• ​Solid-Insulated RMUs:​​ Use solid insulation materials as the main insulation medium. The switch and all live parts are encased or potted with insulating materials like epoxy resin. Because the safe phase-to-phase and phase-to-ground insulation distances inside the switch are reduced, their size and volume are similar to SF6 RMUs. They produce no SF6 emissions and achieve true maintenance-free operation.

​2 Limitationes Usus SF6 RMUs​
SF6 est magnus contribuens ad effectus horti vitrei atmosphaerae. Tamen, SF6 possidet idealis proprietates electricas (insulation excellentis, arc-quenching, et cooling performance), fortis electronegativity, bonam conductivitatem thermicam et stabilitatem, reutilizabilis, insensibilis ad conditiones ambientales (humiditatem, pollutionem, altitudinem altam), et permittit designa cabinet compactor. Proinde, late usatur ut medium insulationis et arc-quenching in equipment electrico. Consumptio SF6 maxima est in industria electrica; statistica indicant 80% SF6 gas productus annuatim usatur in equipment electrico.

United Nations Intergovernmental Panel on Climate Change (IPCC) et US Environmental Protection Agency (EPA) ambo classificant SF6 ut gas horti vitrei extremus nocivus et impactus. EU F-Gas Regulation (2006) praescribit: nisi pro switchgear electrica ubi non existat alternativa viable, usus SF6 prohibetur in plerisque campis.

Praeterea, SF6 RMUs sunt complexi ad usum et requirunt investitionem substantialem, necessitantes multa auxilia dispositiva:

• ​Purchase SF6 Leakage Monitoring Equipment:​​ Used for SF6 gas leak detection, monitoring SF6 concentration and oxygen content, detecting trace moisture, etc.
• ​Equip SF6 Recovery Units:​​ By-products like SF4 are generated within the gas compartment during the SF6 arc-quenching process. Therefore, at end-of-life, not only must the remaining SF6 gas be recovered, but the residual toxic by-products require special treatment.
• ​Configure SF6 Gas Purification Equipment:​​ To purify and recycle the SF6 gas.
• ​Install Ventilation Equipment in Substations.​​

When using SF6 RMUs, it is imperative to:

• ​Minimize SF6 Leakage:​​ SF6 RMUs use pressurized sealed cavities, but gas leakage is unavoidable. Performing switching operations when SF6 pressure is low results in low reliability, directly threatening operator safety and reducing equipment lifespan.
• ​Before workers enter the substation, forced ventilation must be performed first, and they must wear special protective gear.​​
• ​Operations and procedures are complex, requiring repeated training for relevant personnel.​​

​3 Characteristica et Applicationes Solid-Insulated RMUs​
Periculum potentialis environmentalis SF6 RMUs limitat ulterius eorum developmentem. Inveniendi alternativas ad SF6 fuit subjectum researchi globalis. Solid-Insulated RMUs primum fuerunt developpati et introducti ab Eaton Corporation (USA) in fine 1990. Durante operatione, non generant ullum gas toxicum vel nocivum, nullum habent impactum environmentalis, offerunt maiorem fidem, et assequuntur veram operationem sine maintenance.

Solid-Insulated RMUs referuntur ad systema ubi circuitus conductivi principales—sicut vacuum interruptor, disconnector, earthing switch, busbar principale, busbar ramalis—sunt individualiter vel in combinatione inclusi cum materialibus insulationis solidis sicut resina epoxy. Sunt encapsulati intra modulos functionales totaliter insulatos et sigillatos, qui possunt ulterius combini vel expandi. Superficies exteriores modulorum accessibiles personae sunt tectae stratum conductivum vel semi-conductivum et possunt directe et secure terrari.

​3.1 Characteristica Solid-Insulated RMUs​

• ​Eco-Design:​​ Does not use SF6 as insulation or switching medium. Instead, vacuum is used as the arc-quenching medium for switches, and environmentally friendly materials with no environmental impact (and which are recyclable) are used as the main insulation medium. Furthermore, the number of components is minimized to ensure low energy consumption during operation and fewer potential failure points.
• ​Truly Maintenance-Free:​​ Solid-Insulated RMUs eliminate the SF6 pressure vessel. The internal insulation and arc-quenching of the switch body utilize a vacuum medium; external insulation uses solid dielectric materials like insulating cylinders. The insulating cylinder employs solid-casting technology, integrating the vacuum interrupter, main conductive circuit, and insulating supports into a single unit, sealed within a metal enclosure, unaffected by the external environment. Due to the fully insulated and sealed overall structure, and the absence of issues like SF6 leak detection, refilling, and waste disposal, true maintenance-free operation is achieved.
• ​High Cost-Effectiveness:​​ Although the initial investment for solid-Insulated RMUs is slightly higher than for SF6 RMUs, the total life-cycle cost is significantly lower, as shown in Table 1. User considerations are increasingly comprehensive, encompassing not only the initial purchase price but also overall life-cycle costs, including safety risks, grid quality, cost control, and sustainability. The costs required for maintaining, refilling gas, handling leaks, and final recovery of SF6 RMUs during their lifespan are almost equivalent to the purchase cost. In contrast, solid-Insulated RMUs involve one initial investment with essentially no subsequent costs. Therefore, from a long-term perspective, the economic efficiency of solid-Insulated RMUs is far superior to that of SF6 RMUs.

​Table 1: Life-Cycle Cost Comparison between SF6 RMUs and Solid-Insulated RMUs​

• ​Compact Structure:​​ Designed to be as compact as possible while ensuring cabinet safety and ease of operation. Their footprint and volume are even smaller than SF6 RMUs, helping users save space and providing direct economic benefits.
• ​Internal Arc-Resistant Design, Safer and More Reliable:​​ For primary and secondary switchgear, significant damage due to internal arcing occurs at least once annually. Most solid-Insulated RMUs incorporate internal arc-resistant design. When an internal arc occurs, its impact on the RMU is minimized as much as possible, ensuring safer and more reliable equipment operation.
• ​Visualized Isolation Gap:​​ Features a visual observation window for easily checking the contact status of the internal triple-position disconnector, providing visible isolation on-site and enhancing operator safety.
• ​Smart Capabilities:​​ Easier to implement distribution automation compared to SF6 RMUs. After installing a Distribution Terminal Unit (DTU) and communication devices, functions like status data acquisition and monitoring, "Four-Remote" functions (remote signaling, remote measurement, remote control, remote regulation), communication, self-diagnosis, and logging/reporting can be readily achieved.

​3.2 Status Applicationis​
Nunc, adoptionis generalis solid-Insulated RMUs cohibetur per eorum pretium relativum maius et processus manufacturae complexos. Eorum requisiti processuales superant SF6 gas-insulati RMUs. Si technicae processuales sint insufficiens, risus insulationis, probabilitates defectus, et pericula possunt esse maiora quam SF6 RMUs, necessitantes strictam qualitatis controllem materiarum primarum et craftsmanship. Praeterea, flexibilitas wiring solid-Insulated RMUs potest esse limitata, praecipue pro unitatibus functionalibus sicut PT (VT) cabinets et metering cabinets, offerens pauciores optiones connectionis et limitans electionem usus, quod etiam aliquantum cohibit operatio et development solid-Insulated RMUs.

Cum continua optimisatione structurarum productionis et incremento standardisationis in manufactura producti, qualitas producti solid-Insulated RMUs fit stabilior, et pretia gradualiter diminuuntur. Quaedam naciones offerunt incentives 5%~10% pro productis quae non utantur SF6, ad reducendum usum et emissiones. Hoc significat usus non considerant solum pretia emptionis in decision-making. Possumus etiam discere ex practicis internationalibus: prioritate utamur solid-Insulated RMUs in projectis sensibilibus environmentaliter et novis projectis (e.g., communities residentiales, edificia publica, constructiones municipalia), gradatim phasing out SF6 RMUs. Phasing out et substituendo vetustos vel operationales SF6 RMUs secundum eorum promissum manufactureris vitae et subsidia providendo usus adoptantes eco-friendly solid-Insulated RMUs ad supportandos tales productus. Cum crescendo awareness environmentalis usus et considerationes costi vitae, prospectus solid-Insulated RMUs est latus.

​4 Conclusio​
Solid-Insulated RMUs sunt technice equivalentes SF6 RMUs et possident quaedam characteristica quae SF6 RMUs desunt, sicut nulla emissio gas nocivus, vera operatio sine maintenance, et minus costus totalis vitae. Gradatim capiunt attentionem et preference usus.