Оптоволоконні датчики температури INNO ,системи контролю температури.
- SF6 (гексафторид сірки) is a synthetic, colorless, без запаху, non-flammable gas with exceptional dielectric strength and arc-quenching capability, making it indispensable in high-voltage electrical equipment.
- SF6 gas has a dielectric strength approximately 2.5 times that of air at atmospheric pressure and roughly 3 times at typical operating pressures used in розподільні пристрої з елегазовою ізоляцією (ГІС).
- Primary applications include Елегазові вимикачі, розподільні пристрої з елегазовою ізоляцією, gas-insulated transformers, і gas-insulated transmission lines (GIL) across voltage classes from 72.5 кВ до 1,100 кВ.
- SF6 is classified as a potent greenhouse gas with a global warming potential (GWP) з 23,500 over a 100-year horizon and an atmospheric lifetime of approximately 3,200 років.
- Правильно Системи моніторингу елегазу, including density monitors, leak detectors, and decomposition analyzers, are essential for safe operation and environmental compliance.
- Regulatory pressure in the EU and other jurisdictions is driving research into SF6 alternatives such as fluoronitrile mixtures (C4F7N) and fluoroketone (C5F10O) blends for new equipment designs.
- The installed base of SF6-insulated equipment worldwide contains an estimated 250,000+ metric tons of SF6 gas, requiring rigorous lifecycle management from filling to recovery and recycling.
Зміст
- What is SF6 Gas?
- Physical and Chemical Properties of SF6 Gas
- Dielectric and Arc-Quenching Performance
- Applications of SF6 Gas in Electrical Equipment
- SF6 Gas Monitoring and Detection Systems
- SF6 Gas Handling, Зберігання, і Безпека
- Environmental Impact and Regulations
- SF6 Gas Alternatives for Electrical Equipment
- Часті запитання
1. What is SF6 Gas?
елегаз, або гексафторид сірки, is a synthetic inorganic compound with the chemical formula SF₆. It consists of one sulfur atom bonded to six fluorine atoms in an octahedral molecular geometry, forming one of the most chemically stable and electrically insulating gases known to science. First synthesized in 1900 by French chemists Henri Moissan and Paul Lebeau, SF6 found its defining industrial purpose in the mid-20th century when its extraordinary діелектрична міцність і arc-quenching properties were harnessed for high-voltage electrical equipment.
At standard temperature and pressure, SF6 є безбарвним, без запаху, нетоксичний, and non-flammable gas approximately five times denser than air. Its molecular weight of 146.06 g/mol gives it a distinctive heaviness that contributes to its insulating behavior. In the electrical power industry, sulfur hexafluoride gas serves as the primary insulating and arc-interrupting medium in equipment ranging from medium-voltage switchgear в 12 кВ до ultra-high-voltage circuit breakers і GIS systems operating at 1,100 кВ і вище.
Why SF6 Became the Industry Standard
Before SF6, high-voltage equipment relied on air, масло, or vacuum as insulating and interrupting media. Air-blast circuit breakers were physically enormous. Oil circuit breakers posed fire and explosion risks. SF6 offered a compelling alternative — compact equipment with superior interrupting performance, менші вимоги до обслуговування, and dramatically reduced footprint. By the 1970s and 1980s, SF6 gas-insulated equipment had become the global standard for high-voltage substations, particularly in urban areas and indoor installations where space is constrained.
2. Physical and Chemical Properties of SF6 Gas
The exceptional performance of SF6 in electrical applications is rooted in its unique combination of physical and chemical properties. Understanding these properties is essential for engineers specifying, operating, and maintaining SF6-filled electrical equipment.
| Property | Значення | Значимість |
|---|---|---|
| Molecular Formula | SF₆ | Octahedral symmetry, highly stable |
| Molecular Weight | 146.06 г/моль | ~5× heavier than air |
| Boiling Point (1 atm) | −63.9 °C (−83 °F) | Remains gaseous in most climates |
| Критична температура | 45.6 °C (114 °F) | Defines upper pressure limits |
| Critical Pressure | 37.6 бар (545 psi) | Operating pressures typically 4–8 bar |
| Density at STP | 6.16 g/L | High density aids insulation |
| Діелектрична міцність (1 atm) | ~2.5× air | Enables compact equipment design |
| Теплопровідність | ~1.3× air | Good heat dissipation in equipment |
| Toxicity | Non-toxic (pure state) | Decomposition byproducts are toxic |
| GWP (100-рік) | 23,500 | Potent greenhouse gas |
| Atmospheric Lifetime | ~3,200 years | Extremely persistent once released |
2.1 Chemical Stability
Sulfur hexafluoride is one of the most chemically inert compounds known. The six fluorine atoms completely shield the central sulfur atom, creating an extremely strong and symmetric molecular bond structure. This stability means that SF6 does not react with other materials inside sealed electrical compartments — it does not attack copper, алюміній, epoxy resin insulators, прокладки, or other components commonly found in розподільні пристрої з елегазовою ізоляцією і Елегазові вимикачі.
2.2 Behavior Under Electrical Stress
When SF6 gas is subjected to an electrical arc — as occurs during circuit breaker operation — the gas molecules dissociate into sulfur and fluorine atoms and ions. The critical advantage is that SF6 rapidly recombines after the arc is extinguished, restoring its full dielectric strength within microseconds. This self-healing property is what makes SF6 uniquely effective as an arc-quenching medium. Проте, the arc-induced dissociation also produces trace amounts of decomposition byproducts, including sulfur dioxide (SO₂), фтористий водень (HF), and various sulfur fluoride compounds (S₂F₁₀, SOF₂, SO₂F₂), some of which are highly toxic and corrosive.
3. Dielectric and Arc-Quenching Performance
The dielectric performance of елегаз is the primary reason for its dominance in high-voltage equipment. At atmospheric pressure, SF6 має діелектричну міцність приблизно 2.5 разів більше повітря. При типовому робочому тиску 4–6 бар (абсолютний) використовується в ГІС обладнання, діелектрична міцність підвищується до приблизно 3 разів більше повітря, дозволяє різко зменшити розміри обладнання.
3.1 Електронегативні властивості
SF6 є сильно електронегативним газом, тобто його молекули легко захоплюють вільні електрони. В електричному полі, будь-який електрон, вивільнений через іонізацію, швидко поглинається молекулою SF6, утворюючи важкий, повільний негативний іон. Цей механізм захоплення електронів пригнічує розвиток електронних лавин — фундаментального процесу, що лежить в основі електричного пробою. Ця властивість дає перевагу SF6 insulation performance порівняно з повітрям, nitrogen, або CO₂.
3.2 Механізм розриву дуги
в Елегазові вимикачі, процес гасіння дуги заснований на тому, що газ продувається через дугу поршневим механізмом (пуховий тип) або теплову енергію від самої дуги (self-blast type). The high thermal conductivity and electronegative nature of SF6 rapidly cool the arc channel and extract energy from it. At current zero crossings in AC systems, SF6 quickly rebuilds dielectric strength across the contact gap, successfully interrupting fault currents that can reach 63 kA or higher in modern high-voltage circuit breakers.
Dielectric Strength Comparison Across Gases
| газ | Relative Dielectric Strength (Air = 1.0) | Use in Electrical Equipment |
|---|---|---|
| Air | 1.0 | Air-insulated switchgear (AIS) |
| Nitrogen (N₂) | 1.0 | Some transformer blankets |
| CO₂ | 0.9 | Limited applications |
| SF6 | 2.5 (в 1 atm) | ГІС, автоматичні вимикачі, GIL, GIT |
| C4F7N / CO₂ mixture | ~2.0–2.3 | Emerging SF6 alternative |
| C5F10O / Air mixture | ~1.5–1.8 | Emerging SF6 alternative |
| Clean Dry Air | 1.0 | AIS, clean-air switchgear |
4. Applications of SF6 Gas in Electrical Equipment
Sulfur hexafluoride is used across a wide range of electrical power equipment where high dielectric strength, arc-quenching capability, and compact design are required. The global installed base of SF6 equipment spans transmission, розподіл, and generation systems on every continent.
4.1 SF6 Circuit Breakers
Елегазові вимикачі are the dominant technology for interrupting high-voltage AC circuits at voltage levels from 72.5 кВ до 1,100 кВ. Modern designs include single-pressure puffer-type breakers and self-blast (thermal-assist) рубильники. These units can interrupt short-circuit currents of 40–80 kA with operating times under 3 cycles (50 ms at 60 Гц). Dead-tank SF6 breakers і live-tank SF6 breakers are the two principal configurations, each suited to different substation designs and seismic requirements.
4.2 Розподільні пристрої з елегазовою ізоляцією (ГІС)
Елегоізольовані розподільні пристрої (ГІС) encapsulates circuit breakers, роз'єднувачі, заземлювачі, трансформатори струму, трансформатори напруги, and bus conductors within sealed aluminum or steel enclosures filled with pressurized SF6. GIS installations occupy 10%–20% of the floor space required by equivalent air-insulated switchgear (AIS) підстанції. This makes GIS essential for urban substations, підземні установки, морські платформи, і будь-яке місце, де обмежений простір або суворі умови навколишнього середовища.
4.3 Трансформатори з елегазовою ізоляцією (GIT)
Трансформатори з елегазовою ізоляцією використовуйте елегаз як ізоляційне та охолоджувальне середовище замість традиційного мінеральне трансформаторне масло. Оскільки SF6 негорючий, ці трансформатори ідеально підходять для чутливих до пожежі установок, таких як підземні підстанції, будівлі, тунелі, і морські платформи. Трансформатори з елегазовою ізоляцією зазвичай доступні в рейтингах до приблизно 300 МВА і 170 кВ, хоча деякі виробники пропонують вищі рейтинги.
4.4 Лінії електропередачі з елегазовою ізоляцією (GIL)
Елегазові лінії електропередачі (GIL) використовуйте газові суміші SF6 або SF6/N₂ як ізоляційне середовище всередині герметичних металевих трубок для передачі електроенергії високої напруги на відстані, як правило, від кількох сотень метрів до кількох кілометрів. GIL is used where overhead lines or conventional cables are not feasible — such as through tunnels, across bridges, in densely built-up areas, and for river or strait crossings.
4.5 Other SF6 Applications
Beyond the major applications above, SF6 is also used in SF6 gas-insulated current transformers, SF6 gas-insulated voltage transformers, SF6 gas-insulated bushings, and certain types of surge arresters і load break switches at medium- and high-voltage levels.
| Equipment Type | Діапазон напруги | SF6 Function | Typical SF6 Pressure |
|---|---|---|---|
| SF6 Circuit Breaker | 72.5–1,100 kV | Ізоляція + Arc Quenching | 5–7 bar (abs) |
| Розподільні пристрої з елегазовою ізоляцією (ГІС) | 72.5–1,100 kV | Ізоляція + Arc Quenching | 4–6 bar (abs) |
| Gas-Insulated Transformer (GIT) | До 170 кВ | Ізоляція + Охолодження | 1.5–3 bar (abs) |
| Gas-Insulated Line (GIL) | 145–550 kV | Ізоляція | 4–8 bar (abs) |
| SF6 Instrument Transformer | 72.5–800 кВ | Ізоляція | 3–5 bar (abs) |
| Medium-Voltage Switchgear | 12–40,5 кВ | Ізоляція + Arc Quenching | 1.3–1.5 bar (abs) |
5. SF6 Gas Monitoring and Detection Systems
Given the critical role of SF6 in maintaining the insulating and arc-interrupting integrity of high-voltage equipment, and the severe environmental consequences of uncontrolled emissions, комплексний Системи моніторингу елегазу are an essential component of modern substation design and operation. These systems ensure that gas quality, тиск, and containment are continuously verified across every SF6-filled compartment in the installation.
5.1 SF6 Gas Density Monitors
The SF6 gas density monitor (also called a density relay) is the most fundamental monitoring device installed on every SF6 gas compartment. Unlike a simple pressure gauge, a density monitor compensates for temperature variations to provide an accurate indication of the actual mass of SF6 gas inside the sealed compartment. If the gas density drops below a preset alarm threshold — indicating a leak — the monitor triggers an alert. If density falls to a second, lower threshold, it can initiate a lockout to prevent equipment operation under unsafe conditions.
Сучасний electronic SF6 density transmitters replace older mechanical dial-type monitors with continuous digital output signals (4–20 mA or digital protocols) that feed directly into the substation’s SCADA система або інтелектуальні електронні пристрої (СВУ). This enables real-time remote monitoring and trending of SF6 inventory across an entire fleet of GIS bays і автоматичні вимикачі.
5.2 SF6 Gas Leak Detection Systems
While density monitors detect the consequence of a leak (reduced gas quantity), dedicated SF6 gas leak detectors identify the location and rate of the leak itself. Several technologies are in widespread use.
Portable SF6 Leak Detectors
Portable SF6 leak detectors based on negative ion capture (electron capture detector) or non-dispersive infrared (NDIR) technology are standard tools for maintenance crews. Modern handheld units can detect SF6 concentrations as low as 0.1 ppmv and pinpoint leak locations on GIS flanges, bushing interfaces, valve stems, and weld seams. Leading manufacturers of SF6 leak detection equipment include DILO, Ion Science, Fluke, and Besantek.
Fixed Area SF6 Monitoring Systems
Fixed SF6 area monitors are permanently installed in enclosed GIS rooms, підземні підстанції, and cable tunnels where SF6 equipment is housed. These systems use infrared photoacoustic sensors or NDIR sensors to continuously measure the ambient SF6 concentration in the room air. They serve two purposes: безпека персоналу (SF6 is an asphyxiant in high concentrations as it displaces oxygen) and early warning of equipment leaks. IEC 62271-1 and IEEE C37.122 both reference requirements for gas detection and ventilation in GIS installations.
5.3 SF6 Gas Quality Analyzers
After electrical arcing events, maintenance activities, or prolonged service, the quality of елегаз inside equipment must be verified. SF6 gas analyzers measure moisture content, чистота (percentage of SF6), and the concentration of decomposition byproducts such as SO₂ and HF. IEC 60480 specifies the quality requirements for SF6 gas used in electrical equipment, including limits for moisture (< 25 ppmv for new gas), чистота (> 99.9%), and acidity.
| Пристрій моніторингу | Що він вимірює | Розташування | Output / Interface |
|---|---|---|---|
| SF6 Density Monitor (Mechanical) | Gas density (temp-compensated) | Each gas compartment | сигналізація + lockout contacts |
| SF6 Density Transmitter (Electronic) | Gas density (безперервний) | Each gas compartment | 4–20 мА / SCADA |
| Portable Leak Detector | SF6 concentration at source | Handheld / обслуговування | Display + audible alarm |
| Fixed Area Monitor | Ambient SF6 in room | GIS room / cable tunnel | сигналізація + ventilation trigger |
| SF6 Gas Analyzer | Purity, вологи, SO₂, HF | Портативний / lab | Display / report |
| Online Decomposition Monitor | SO₂, HF, CF₄ levels | Critical GIS bays | Безперервний / SCADA |
5.4 Integrated SF6 Asset Management Platforms
Progressive utilities and transmission system operators now deploy integrated SF6 gas management platforms that aggregate data from density transmitters, leak detection surveys, gas quality test results, and gas handling records into a centralized database. These platforms track SF6 inventory by equipment serial number, calculate annual SF6 leakage rates as required by EPA (in the U.S.) or EU F-Gas Regulation reporting, and generate compliance documentation. Leading utility asset management software vendors increasingly include dedicated SF6 tracking modules.
6. SF6 Gas Handling, Зберігання, і Безпека
Правильно SF6 gas handling requires specialized equipment and trained personnel. SF6 is shipped and stored in pressurized steel cylinders as a liquid under its own vapor pressure. Before filling into electrical equipment, the gas must be verified for purity and moisture content per IEC 60480 or applicable utility specifications.
6.1 SF6 Gas Handling Equipment
SF6 gas handling carts (also called SF6 service carts or SF6 reclaimers) are purpose-built systems that perform the complete lifecycle of SF6 management: evacuation of equipment compartments, recovery of SF6 from equipment, filtration and purification, зберігання, and re-filling. Modern units from manufacturers such as DILO, Enervac, Comde-Derenda, and Mega conform to IEC 62271-4 standards and can achieve SF6 recovery rates exceeding 99.5%, minimizing emissions during maintenance operations.
6.2 Personnel Safety Considerations
Чистий SF6 нетоксичний і хімічно інертний. Проте, two safety concerns are paramount. перше, because SF6 is five times denser than air, it can accumulate in pits, траншеї, cable basements, and low-lying enclosed spaces, displacing oxygen and creating an asphyxiation hazard. друге, SF6 decomposition products generated by electrical arcing — including SO₂, HF, S₂F₁₀, SOF₂, and SO₂F₂ — are highly toxic and corrosive. Workers must use appropriate personal protective equipment (ЗІЗ) including respiratory protection and chemical-resistant gloves when handling used SF6 gas or opening compartments that have experienced internal arcing faults.
Key Safety Standards
The principal international standards governing SF6 handling and safety include IEC 62271-4 (handling procedures for SF6 and its mixtures), IEC 60480 (specifications for re-use of SF6), and EPA 40 CFR Part 98 Subpart DD (mandatory reporting of SF6 emissions in the United States). The EU F-Gas Regulation (немає. 517/2014, revised 2024) imposes strict reporting requirements and phase-down measures on high-GWP gases including SF6.
7. Environmental Impact and Regulations
The environmental profile of елегаз is the most significant challenge facing its continued use. With a global warming potential (GWP) з 23,500 — meaning one kilogram of SF6 released to the atmosphere has the same warming effect as 23,500 kilograms of CO₂ over 100 years — and an atmospheric lifetime of approximately 3,200 років, SF6 is among the most potent greenhouse gases regulated under the Kyoto Protocol and the Paris Agreement.
7.1 Emission Sources and Rates
SF6 emissions from the electrical industry occur through equipment leakage during normal service, losses during maintenance and gas handling, and end-of-life disposal. The IEC standard for acceptable annual leakage from new sealed-pressure GIS equipment is less than 0.5% per year per gas compartment. Well-maintained modern equipment routinely achieves leakage rates below 0.1% на рік. Проте, older equipment, particularly units installed before the 1990s, can exhibit significantly higher leakage rates.
7.2 Regulatory Landscape
| Регіон | Regulation | Key Requirement |
|---|---|---|
| European Union | F-Gas Regulation (revised 2024) | Ban on new SF6 MV switchgear from 2030; HV restrictions phased |
| США | EPA 40 CFR Part 98 Subpart DD | Mandatory emission reporting for utilities |
| Каліфорнія (США) | CARB SF6 Regulation | Annual emission rate target of 1% за 2020 |
| Японія | High Pressure Gas Safety Act | Reporting and handling requirements |
| International | Kyoto Protocol / Paris Agreement | SF6 listed in basket of regulated GHGs |
8. SF6 Gas Alternatives for Electrical Equipment
The environmental pressure on SF6 has driven major equipment manufacturers to develop and commercialize alternative insulating and interrupting gases, particularly for new installations.
8.1 Fluoronitrile-Based Mixtures (C4F7N)
Fluoronitrile gas mixtures, marketed by GE Vernova under the brand name g³ (Green Gas for Grid), blend C4F7N with CO₂ and O₂ as buffer gases. These mixtures achieve approximately 90%–100% of SF6’s dielectric performance at equivalent pressures with a GWP reduction of more than 99%. GIS systems using fluoronitrile mixtures are commercially available and installed at voltage levels up to 420 кВ.
8.2 Fluoroketone-Based Mixtures (C5F10O)
Fluoroketone gas mixtures — blending C5F10O with air or nitrogen — have been commercialized primarily by ABB (now Hitachi Energy) under the AirPlus brand for medium-voltage switchgear at 12–40.5 kV. The GWP of C5F10O is less than 1, making it virtually climate-neutral. Проте, the lower dielectric strength of these mixtures compared to SF6 means larger compartment sizes or higher pressures.
8.3 Clean Dry Air and Vacuum Technology
для medium-voltage switchgear, вакуумні вимикачі combined with clean dry air insulation have become the standard SF6-free solution. At distribution voltage levels (12–40,5 кВ), vacuum interruption technology is mature and widely available. At higher voltages, pure air insulation requires substantially larger equipment, limiting its applicability where space is constrained.
SF6 Alternatives Comparison
| Alternative | GWP | Dielectric Strength vs. SF6 | Діапазон напруги | Commercial Status |
|---|---|---|---|---|
| C4F7N / CO₂ / O₂ mixture | ~328 (mixture) | 90%–100% | До 420 кВ | Commercially available |
| C5F10O / Air mixture | <1 | 60%–80% | До 40.5 кВ | Commercially available |
| Clean Dry Air | 0 | ~40% | До 420 кВ (large enclosure) | Commercially available |
| Вакуум (MV breaker) | 0 | N/A (interruption only) | До 145 кВ | Зріла технологія |
| CO₂ / O₂ mixture | <1 | ~35%–40% | До 72.5 кВ | Limited deployment |
Часті запитання
Q1: What does SF6 stand for?
SF6 stands for sulfur hexafluoride, a chemical compound consisting of one sulfur atom and six fluorine atoms (chemical formula SF₆). It is a synthetic gas not found naturally in the environment.
Q2: Why is SF6 gas used in circuit breakers?
SF6 is used in circuit breakers because of its exceptional dielectric strength (2.5× повітря) and rapid arc-quenching capability. It can extinguish high-energy electrical arcs and restore insulation strength within microseconds, enabling compact and reliable high-voltage circuit breaker конструкції.
Q3: Чи небезпечний для людини елегаз?
Чистий SF6 нетоксичний і хімічно інертний. Проте, it poses an asphyxiation risk in enclosed spaces because it is five times heavier than air and displaces oxygen. Додатково, SF6 decomposition byproducts formed by electrical arcing — including SO₂ and HF — are highly toxic and corrosive, requiring proper safety precautions during maintenance.
Q4: What is an SF6 gas density monitor?
Ан SF6 gas density monitor is a temperature-compensated measuring device installed on each gas compartment of SF6 equipment. It monitors the actual gas mass inside the compartment and triggers alarms or equipment lockouts if the density falls below safe thresholds, indicating a gas leak.
Q5: How do you detect an SF6 gas leak?
SF6 leaks are detected using portable SF6 leak detectors (based on electron capture or NDIR infrared technology), fixed area SF6 monitors in GIS rooms, and density trending from electronic SF6 density transmitters. Modern detectors can identify leaks as small as 0.1 ppmv.
Q6: What is the global warming potential of SF6?
SF6 has a 100-year global warming potential (GWP) з 23,500, meaning one kilogram of SF6 has the same greenhouse effect as 23,500 kilograms of CO₂. Its atmospheric lifetime is approximately 3,200 років, making it one of the most persistent greenhouse gases known.
Q7: Can SF6 gas be recycled?
так. SF6 gas can be recovered from equipment using specialized SF6 gas handling carts, purified through filtration and adsorption processes to remove moisture and decomposition byproducts, and re-used. IEC 60480 specifies the quality requirements that reclaimed SF6 must meet before re-use in electrical equipment.
Q8: What are the alternatives to SF6 in switchgear?
Commercially available alternatives include fluoronitrile-based gas mixtures (C4F7N/CO₂), fluoroketone-based gas mixtures (C5F10O/air), vacuum interruption technology, and clean dry air insulation. These are available for different voltage classes, with the most mature SF6-free solutions at medium-voltage levels.
Q9: What is gas-insulated switchgear (ГІС)?
Елегоізольовані розподільні пристрої (ГІС) is a type of high-voltage switchgear where the busbars, автоматичні вимикачі, роз'єднувачі, and other components are enclosed in sealed metal housings filled with pressurized SF6 gas. GIS occupies 10%–20% of the space required by conventional air-insulated switchgear, making it essential for urban and space-constrained installations.
Q10: How often should SF6 gas quality be tested?
IEC and IEEE standards recommend testing SF6 gas quality (вологи, чистота, and decomposition products) before initial energization, after any maintenance involving gas handling, after internal fault events, and periodically during service — typically every 5–10 years depending on utility policy and regulatory requirements.
Відмова від відповідальності
Інформація, наведена в цій статті, призначена виключно для загальних інформаційних і освітніх цілей. FJINNO (www.fjinno.net) strives to ensure the accuracy of all technical data, технічні характеристики, and regulatory references presented herein, but makes no warranties or guarantees regarding completeness, timeliness, or suitability for any particular application. Electrical equipment specifications, gas handling procedures, стандарти безпеки, and environmental regulations vary by jurisdiction and are subject to change. This content does not constitute professional engineering, безпеки, або поради щодо дотримання нормативних вимог. Readers must consult qualified engineers, equipment manufacturers, and relevant regulatory authorities before making technical, закупівлі, or compliance decisions. FJINNO assumes no liability for any losses, damages, injuries, or regulatory penalties arising from the use or interpretation of information contained in this article.
Оптоволоконний датчик температури, Інтелектуальна система моніторингу, Розповсюджений виробник оптоволокна в Китаї
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