Текущие применения и будущие тенденции твердотельных изолированных кольцевых главных распределительных устройств (RMUs)

1.Текущее состояние применения твердотельных секционных ячеек в средневольтных распределительных сетях

1.1 Широкое применение в городских жилых районах

Основные компоненты средневольтных секционных ячеек (RMU) в основном состоят из коммутационных аппаратов и предохранителей. Эти устройства предлагают несколько преимуществ, таких как простая конструкция, компактные размеры и относительно низкая стоимость. Кроме того, они эффективно улучшают качество электроэнергии и повышают надежность и безопасность электроснабжения. Наблюдения показывают, что максимальный номинальный ток для средневольтных RMU составляет 1250А, при типичном значении 630А. В зависимости от изоляционного материала RMU обычно делятся на два типа: с воздушной изоляцией и с изоляцией SF₆. Они主要用于城市住宅区的广泛应用。中压环网单元（RMU）的核心组件主要由负荷开关和熔断器组成。这些装置具有几个优点，包括结构简单、体积小、成本相对较低。此外，它们有效提高了电能质量，增强了供电的可靠性和安全性。观察表明，中压RMU的最大额定电流为1250A，典型值为630A。根据绝缘介质的不同，RMU通常分为两类：空气绝缘和SF₆气体绝缘。它们主要用于切换负荷电流和中断短路电流，并提供一定的控制和保护功能。 在空气绝缘RMU中使用的负荷开关包括四种类型：产气型、压缩空气型、真空型和SF₆型。其中，SF₆负荷开关是空气绝缘RMU中的主要开关。密封外壳内的负荷开关通常有三个操作位置：负荷中断、可靠接地和电路隔离。 一般来说，RMU的设计紧凑。鉴于这一特点，大多数负荷开关（通常是高压开关）具有相对简单的结构，并配备了高压熔断器。RMU的正常运行主要依赖于负荷开关，而熔断器则有效地中断了短路电流。这两个组件的有效结合最大限度地替代了断路器，尽管这种替代仅限于特定容量范围。 2. 固体绝缘环网单元的发展趋势和技术特点 2.1 封装极技术的有效应用 环氧树脂通常用作固体绝缘的主要绝缘材料，以真空作为灭弧介质。为了有效实现负荷和电流隔离等功能，必须正确驱动操作机构，以实现对配电系统的有效控制，进一步保护设备和人员安全。固体绝缘显著减少了开关柜内的相间绝缘距离，将空气绝缘间隙从125毫米缩短到几毫米。没有SF₆气体，整体体积比传统的C-GIS要小。此外，使用相对简单的操作机构有效减少了部件数量，提高了设备的可靠性。 2.2 固体绝缘RMU的技术特点 与带有SF₆开关的空气绝缘RMU和SF₆气体绝缘RMU相比，固体绝缘RMU具有几个优势：首先，外壳结构更简单。通过消除压力容器、压力表、充气阀等与气体相关的部件，大大提高了RMU的可靠性，降低了维护成本，并有效提升了开关的操作状态。其次，主开关配备有隔离组件，提供了明显的断开点。固体绝缘主要使用环氧树脂套管和绝缘管。这些材料有效缓解了寒冷地区SF₆液化的问题，并减少了高温区域热膨胀的不利影响，展示了在极端环境中的广泛适用性。 3. 固体绝缘环网单元需要注意的问题 3.1 绝缘和表面涂层技术 根据局部放电形成机制，固体绝缘内部放电主要是由于空隙的存在。目前的密封技术通常涉及预热金属模具，将预热的组件放入模具中，缓慢注入并在真空中固化。这个过程不仅效率低下，而且成本高昂。不完全去除气泡会导致固体绝缘中存在大量空隙，可能导致运行时出现局部放电，导致绝缘组件长期开裂，影响设备的安全可靠运行。 因此，必须引入先进的高质量高效的环氧树脂封装技术。此外，由于表面屏蔽直接影响设备性能，在设计和生产过程中必须解决表面屏蔽问题——即表面屏蔽技术。绝缘材料表面镀金属的目的是为固体绝缘组件提供可靠的接地，减少环境因素的影响，并提高产品性能。目前，市场上相当一部分固体绝缘RMU缺乏适当的表面处理，导致提供的产品局部放电水平较高。 3.2 缺乏运行和维护经验 固体绝缘RMU是一项相对较新的技术。由于电网缺乏科学合理的试运行安排，目前总运行量较小，运行时间较短，省级电网连接不完整。例如，在高温高湿、沿海、多雨和昼夜温差大的地区，需要解决实际问题。必须在全国范围内积累全面的工作经验，针对固体绝缘RMU进行有针对性和前瞻性的改进，不断提高产品的安全性和稳定性。 3.3 固体绝缘RMU设备的发展 近年来，随着中国配电网的快速发展，配电系统技术水平显著提高。SF₆气体已在中压RMU中得到广泛应用。从中国目前的发展状况来看，SF₆气体总体性能最佳。然而，随着环保意识的增强和自然保育的重要性日益凸显，RMU中广泛使用SF₆气体存在一定的环境危害和对人体健康的潜在风险。因此，减少SF₆气体RMU的使用并推广固体绝缘RMU将成为高压开关设备发展的主要目标。国内制造商已经预见了这一趋势，并逐渐开始开发和生产固体绝缘RMU产品。 3.4 绝缘模块结构设计的优化 绝缘模块的结构设计必须在满足功能、检查和安装要求的同时，旨在减少材料消耗并防止残余应力。残余应力的存在会导致固体绝缘组件内外部出现裂纹，导致运行时出现局部放电，甚至可能导致绝缘击穿。因此，有必要深入研究绝缘模块的整体结构、厚度和过渡部分，并考虑散热概念。 3.5 屏蔽层的研究与设计 外部设计的主要目的是规划金属屏蔽接地：首先，在绝缘失效的情况下，将短路故障限制在相间，减少电弧能量和故障风险；其次，在任何环境中保持绝缘性能，无需清洁模块外表面，即使机柜内有金属异物也能确保电场分布不变。 4. 固体绝缘环网单元技术的发展方向 4.1 新型高性能绝缘材料的开发 虽然环氧树脂作为固体绝缘材料表现良好，但在真空陶瓷灭弧室中的浇注过程会损坏原材料。因此，开发超越当前材料特性的先进环氧树脂至关重要。2014年，《科学》杂志发表了一篇关于发现一种新型可回收热固性聚合物的文章，标志着“聚水杨酸”热固性塑料回收的重大进展。这种聚合物表现出高可回收性，解决了热固性塑料以前不可回收的问题。在未来十年，新产品将越来越多地使用可回收热固性材料。 4.2 内部组件接口连接方法的研究 由于固体绝缘RMU是通过将主电路导体和安装部件封装在固体绝缘材料中制造的，嵌入式组件的不灵活性要求不同铸件之间的标准化连接。RMU的整体配置是线性的，连接导体必须用环氧树脂浇注，这要求在产品合理化过程中有一定的自由度。为此，提出了一种使用硅橡胶材料进行门到导体连接的接口技术。这种方法实现了标准化，允许组件相互连接并合理配置，简化了整体绝缘外壳的设计复杂性。 4.3 固体绝缘RMU的市场推广前景 固体绝缘RMU具有结构简单、体积小、无毒、无污染、环保等特点，符合全球绿色发展理念。然而，要使产品成功，制造商必须从销售中获利，因此市场应用是一个关键焦点。了解并满足用户需求对于新产品的成功引入至关重要。根据用户需求分析固体绝缘产品的应用前景。 4.3.1 满足消费者需求的产品 在使用过程中，用户首先要求产品技术参数符合相关标准（技术规范、国家标准和行业标准等），并获得国家电力行业的认证。由于目前尚无具体的固体绝缘产品标准，制造商必须协助制定国家标准或行业标准。据报道，截至2002年12月31日，已提交约1500万吨固体绝缘产品的索赔。 4.3.2 用户对配电网产品的高要求 中压配电设备是电网中广泛使用的基本组成部分。随着电网基础设施的不断扩展，作为主网与终端用户之间桥梁的中压设备需求不断增加。用户要求产品具有长寿命、强环境适应性、符合环保标准、体积小、安装快捷方便、经济实惠以及可靠的运行历史。 固体绝缘RMU尺寸紧凑，单个负荷开关柜单元的尺寸为860毫米（深度）× 420毫米（宽度）× 1200毫米（高度）或850毫米（深度）× 500毫米（宽度）× 1600毫米（高度）。其尺寸介于空气绝缘开关设备之间。基于上述技术性能，固体绝缘RMU提供了增强的人身安全。然而，由于运行历史相对较短，目前在中国几家工厂中只有少量设备在运行。由于运行数据有限，目前无法评估环氧绝缘的老化情况或确定检查周期。 一些国内设备制造商通过先进的生产设备（车间、模具和自动化激光焊接）保证产品寿命超过20年。这是一个竞争优势。从经济角度来看，目前生产固体绝缘外壳需要大量投资专用设备、模具和材料，导致市场价格较高。此外，由于电力系统主要采用低价竞标的方式采购设备，SF₆ RMU模块的成本竞争力越来越强，短期内固体绝缘RMU难以在市场上占据主导地位。 4.3.3 产品环境要求 在大多数地区，用户要求正常工作环境不超过40°C且不低于-10°C。然而，全球自然灾害频发，用户需求也在提高。例如，安装在恶劣环境中的RMU必须完全封闭且免维护，确保完全绝缘。断路器设备必须具有强环境适应性、防尘防水、短期浸水保护和增强抗震能力。 将断路器内部组件用环氧树脂浇注，显著提高了绝缘材料的介电强度，防止运输和使用过程中的振动导致的降解。与气体绝缘RMU产品相比，一些制造商在青海和沿海潮湿地区以及海拔约4000米的地方进行了测试，达到了IP68防护等级。因此，固体绝缘RMU产品更好地满足了环境要求。 5. 结论 基于中国固体绝缘RMU目前的发展状况，绝缘技术相对成熟，有效解决了空气绝缘和气体绝缘RMU的不足，适用于高海拔等特殊环境。采用固体绝缘RMU可以有效促进中国电网的发展，推动经济社会可持续发展。随着环保意识的不断增强，可以肯定地说，固体绝缘RMU具有广阔的应用前景。 被用于切换负荷电流和中断短路电流，并提供一定的控制和保护功能。

1.2 Вакуумные коммутационные аппараты RMU обеспечивают надежные изолирующие промежутки

Коммутационные аппараты, используемые в RMU с воздушной изоляцией, включают четыре типа: газогенерирующие, сжатого воздуха, вакуумные и SF₆. Из них коммутационные аппараты SF₆ служат основными выключателями в RMU с воздушной изоляцией. Коммутационные аппараты в герметичных корпусах обычно имеют три рабочих положения: прерывание нагрузки, надежное заземление и изоляция цепи.

1.3 Улучшенный уровень практического применения

В целом, RMU имеют компактную конструкцию. Учитывая эту характеристику, большинство коммутационных аппаратов (обычно высоковольтные выключатели) имеют относительно простую конструкцию и оснащены высоковольтными предохранителями. Нормальная работа RMU в основном зависит от коммутационных аппаратов, а короткие замыкания эффективно прерываются предохранителями. Эффективное сочетание этих двух компонентов максимизирует замену автоматических выключателей, хотя такая замена ограничена определенными диапазонами мощности.

2.Тренды развития и технические характеристики твердотельных секционных ячеек

2.1 Эффективное применение технологии закрытых полюсов

Эпоксидная смола обычно используется в качестве основного изоляционного материала в твердой изоляции, а вакуум служит средой для гашения дуги. Для эффективного выполнения функций, таких как переключение нагрузки и изоляция тока, механизм управления должен быть правильно активирован, чтобы обеспечить эффективное управление системой распределения электроэнергии, тем самым дополнительно защищая оборудование и безопасность персонала. Твердая изоляция значительно уменьшает фазовое расстояние до земли внутри оборудования, сокращая воздушные изоляционные зазоры с 125 мм до нескольких миллиметров. Без SF₆ газа общий объем уменьшается по сравнению с традиционным C-GIS. Кроме того, использование относительно простого механизма управления эффективно уменьшает количество компонентов, повышая надежность оборудования.

2.2 Технические характеристики твердотельных RMU

По сравнению с RMU с воздушной изоляцией, имеющими выключатели SF₆, и RMU с газовой изоляцией SF₆, твердотельные RMU имеют ряд преимуществ: во-первых, конструкция корпуса проще. Устранение резервуаров под давлением, манометров, заправочных клапанов и других компонентов, связанных с газом, значительно повышает надежность RMU, снижает затраты на обслуживание и улучшает эксплуатационное состояние выключателя. Во-вторых, основной выключатель оснащен изолирующим элементом, обеспечивающим четко видимый разрыв. Твердая изоляция в основном использует эпоксидные рукава и изоляционные трубы. Эти материалы эффективно снижаютliquefaction of SF₆ in cold regions and reduce adverse effects from thermal expansion in high-temperature areas, demonstrating broad applicability in extreme environments.

3.Issues Requiring Attention in Solid-Insulated Ring Main Units

3.1 Insulation and Surface Coating Technology

According to the mechanism of partial discharge formation, internal discharges in solid insulation are primarily caused by the presence of voids. Current sealing techniques typically involve preheating metal molds, placing preheated components into the mold, slowly injecting under vacuum, and curing. This process is not only inefficient but also costly. Incomplete bubble removal can lead to numerous voids in the solid insulation, potentially causing partial discharge during operation, leading to long-term cracking of insulation components and affecting the safe and reliable operation of equipment.

Therefore, advanced, high-quality, and efficient epoxy resin encapsulation technology must be introduced. Additionally, since surface shielding directly affects equipment performance, the issue of surface shielding—i.e., surface shielding technology—must be addressed during design and production. The purpose of metallizing the surface of insulation materials is to provide reliable grounding for solid insulation components, minimize the impact of environmental factors, and enhance product performance. Currently, a significant portion of solid-insulated RMUs on the market lack proper surface treatment, resulting in high partial discharge levels in supplied products.

3.2 Lack of Operation and Maintenance Experience

Solid-insulated RMUs are a relatively new technology. Due to the lack of scientific and reasonable trial operation arrangements by power grids, the current total operational volume is small, operational time is short, and provincial grid connections are incomplete. For example, in high-temperature, high-humidity, coastal, high-rainfall, and large diurnal temperature variation regions, practical issues need to be addressed. Comprehensive work experience must be accumulated nationwide to conduct targeted and forward-looking improvements to solid-insulated RMUs, continuously enhancing product safety and stability.

3.3 Development of Solid-Insulated RMU Equipment

In recent years, with the rapid development of China's distribution network, the technical level of the distribution system has significantly improved. SF₆ gas has been widely used in medium-voltage RMUs. From China's current development status, SF₆ gas offers the best overall performance. However, with the increasing awareness of environmental protection and the importance of natural conservation, the extensive use of SF₆ gas in RMUs poses certain environmental hazards and potential risks to human health. Therefore, reducing the use of SF₆ gas RMUs and promoting solid-insulated RMUs will be a primary goal for the development of high-voltage switchgear. Domestic manufacturers have anticipated this trend and have gradually begun developing and producing solid-insulated RMU products.

3.4 Optimization of Insulation Module Structure Design

The structural design of insulation modules must, while meeting functional, inspection, and installation requirements, aim to reduce material consumption and prevent residual stress. The presence of residual stress can cause internal and external cracks in solid insulation components, leading to partial discharge during operation and potential insulation breakdown. Therefore, in-depth research on the overall structure, thickness, and transitions of insulation modules is necessary, with consideration given to heat dissipation concepts.

3.5 Research and Design of Shielding Layers

The primary purpose of external design is to plan metal shielding grounding: first, in the event of insulation failure, to confine short-circuit faults to phase-to-ground only, reducing arc energy and fault risk; second, to maintain insulation performance in any environment without requiring cleaning of the module's outer surface, ensuring unchanged electric field distribution even with metallic foreign objects inside the cabinet.

4.Development Directions for Solid-Insulated Ring Main Unit Technology

4.1 Development of New High-Performance Insulating Materials

Although epoxy resin performs well as a solid insulation material, the casting process in vacuum ceramic arc-quenching chambers can damage raw materials. Therefore, developing advanced epoxy resins that surpass current material characteristics is essential. In 2014, the journal Science published an article on the discovery of a new recyclable thermosetting polymer, marking a significant advancement in the recycling of "polysalicylate" thermosetting plastics. This polymer exhibits high recyclability, addressing the issue that thermosetting plastics were previously non-recyclable. In the next decade, new products will increasingly utilize recyclable thermosetting materials.

4.2 Research on Internal Component Interface Connection Methods

Since solid-insulated RMUs are manufactured by encapsulating main circuit conductors and mounting parts within solid insulation, the inflexibility of embedded components necessitates standardized connections between different cast elements. The overall configuration of the RMU is linear, and connecting conductors must be cast with epoxy resin, requiring a certain degree of freedom during product rationalization. To address this, an interface technology using silicone rubber material for gate-to-conductor connections is proposed. This method enables standardization, allowing components to be interconnected and reasonably configured, reducing the design complexity of the overall insulated enclosure.

4.3 Market Promotion Prospects for Solid-Insulated RMUs

Solid-insulated RMUs feature a simple structure, compact size, non-toxicity, pollution-free operation, and environmental friendliness, aligning with the global green development concept. However, for a product to be successful, manufacturers must profit from sales, making market application a key focus. Understanding and meeting user needs is critical to the successful introduction of new products. The application prospects of solid-insulated products are analyzed based on user requirements.

4.3.1 Products Meeting Consumer Needs

During use, users first require that product technical parameters comply with relevant standards (technical specifications, national and industry standards, etc.) and obtain certification from the national power industry. As no specific standards currently exist for solid-insulated products, manufacturers must assist in establishing national or industry standards. It is reported that by December 31, 2002, claims for approximately 15 million tons of solid-insulated products had been filed.

4.3.2 High User Requirements for Distribution Network Products

Medium-voltage distribution equipment is a fundamental component widely used in power grids. With the continuous expansion of grid infrastructure, demand for medium-voltage equipment as a bridge between main networks and end-users is growing. Users require products with long service life, strong environmental adaptability, compliance with environmental standards, compact size, easy and quick installation, economic convenience, and a reliable operational history.

Solid-insulated RMUs have compact dimensions, with single load switch cabinet units measuring 860mm (depth) × 420mm (width) × 1200mm (height) or 850mm (depth) × 500mm (width) × 1600mm (height). Their size falls between that of air-insulated switchgear. Based on the above technical performance, solid-insulated RMUs provide enhanced personal safety. However, due to their relatively short operational history, only a limited number of units are currently in service across several Chinese factories. Given the limited operational data, it is currently impossible to evaluate the aging of epoxy insulation or determine inspection cycles.

Some domestic equipment manufacturers guarantee a product lifespan of over 20 years through advanced production facilities (workshops, molds, and automated laser welding). This represents a competitive advantage. Economically, current production of solid-insulated enclosures requires significant investment in specialized equipment, molds, and materials, resulting in higher market prices. Additionally, as power systems primarily use equipment bidding with a focus on low prices, SF₆ RMU modules have become increasingly cost-competitive, making it difficult for solid-insulated RMUs to gain market dominance in the short term.

4.3.3 Product Environmental Requirements

In most regions, users require normal operating environments not exceeding 40°C and not below -10°C. However, the increasing frequency of natural disasters globally has raised user demands. For example, RMUs installed in harsh environments must be fully enclosed and maintenance-free, ensuring complete insulation. Circuit breaker equipment must exhibit strong environmental adaptability, dust and moisture resistance, short-term immersion protection, and enhanced vibration resistance.

Casting internal components of circuit breakers with epoxy resin significantly increases the dielectric strength of insulating materials, preventing degradation due to vibration during transportation and use. Compared to gas-insulated RMU products, some manufacturers have conducted tests in Qinghai and coastal humid regions, as well as at altitudes around 4000m, achieving IP68 protection ratings. Therefore, solid-insulated RMU products better meet environmental requirements.

5.Conclusion

Based on the current development status of solid-insulated RMUs in China, the insulation technology is relatively mature, effectively addressing the shortcomings of air-insulated and gas-insulated RMUs, and suitable for special environments such as high-altitude regions. The adoption of solid-insulated RMUs can effectively promote the development of China's power grid and contribute to sustainable socioeconomic development. With growing attention to environmental protection, it can be confidently stated that solid-insulated RMUs have broad application prospects.