Paggamit sa mga Intelligent Solid Insulated Ring Main Units (SIRMUs) sa Distribusyon Network sa Qinzhou

1 Paglakip​

Ang mga rehiyon sa baybayin ay naghaharap ng mga pagsubok sa kapaligiran kabilang ang malakas na ulan, kidlat, mataas na temperatura, mataas na humidity, at mataas na corrosion sa asin. Upang matiyak ang seguridad ng urban distribution grids sa ganitong mga kapaligiran, minimuhin ang power outages dahil sa maintenance ng equipment, at iwasan ang mga aksidente dahil sa pagtatapos ng buhay ng equipment at iba pang mga kadahilanan na nakakaapekto sa seguridad ng grid, nag-research tayo tungkol sa paggamit ng bagong uri ng Solid Insulated Ring Main Unit (SIRMU). Ang SIRMU na ito ay nagbibigay ng mahabang buhay, walang maintenance, pagsunod sa kapaligiran, karunungan, at mas mapagkakatiwalaang supply ng kuryente.

Sa kasalukuyan, higit sa 90% ng medium-voltage Ring Main Units (RMUs) ay umaasa sa SF₆ gas bilang insulating medium. Ang SF₆ gas ay napakatagal sa chemical, may mahusay na insulation at arc-quenching properties, at malawakang ginagamit sa mga power equipment. Ang SF₆ gas-insulated switchgear ay kompakto. Gayunpaman, ang SF₆ gas ay nali-liquefy sa mababang temperatura, bumababa ang kanyang insulation at arc-extinguishing capabilities. Sa mataas na temperatura, ito ay nabubuwag sa mga highly toxic byproducts, nagpapataas ng malaking panganib sa tao. Bukod dito, hindi maiiwasan ang pag-leak at emissions sa panahon ng gas filling, operasyon, at recovery, kaya't ang SF₆ ay isang pangunahing environmental pollutant. Ang SF₆ ay kilala sa pandaigdig bilang isa sa anim na pangunahing greenhouse gases; mula sa perspektibo ng kapaligiran, dapat itong minumize o iwasan. Ang disenyo ng Solid Insulated Ring Main Unit ay fundamental na nag-eeliminate ng pangangailangan para sa SF₆ gas, nagbibigay ng pundamental na guarantee para sa emission reduction at environmental protection sa sektor ng distribution network, na lubos na sumasalamin sa mga pangangailangan ng kapaligiran.

Ang Intelligent Solid Insulated Ring Main Unit (SIRMU) para sa extension ng distribution network ay nagbibigay hindi lamang ng eco-friendliness at outstanding resistance sa harsh environments, kundi pati na rin ng mataas na degree ng karunungan. Ang kanyang functionality ay sumasaklaw sa lahat ng mga features na tradisyonal na ibinibigay ng primary at secondary power system equipment sa loob ng iisang unit. Ang produkto ay gumagamit ng integrated at modular design approach para sa high-voltage at low-voltage components, nagbibigay ng excellent versatility at expandability, kumakatawan sa isang tunay na smart electrical device.

​2 Teknikal na Paggamit ng Intelligent Solid Insulated Ring Main Units (SIRMUs)​​

​2.1 Paggamit ng Solid Insulation Technology​

Ang teknolohiya ng solid insulation pangunahing umuukol sa pag-encapsulate at pag-seal ng mga live parts ng main circuit ng medium-voltage switchgear gamit ang solid materials, o pag-transfer ng mataas na electric field intensity sa interior ng solid insulating material. Ito ay nagpapahintulot sa solid material na makatitiyak ng mas mataas na potentials, kaya't binabawasan ang field strength sa hangin. Ang pinakakaraniwang solid insulating materials ay epoxy resin at silicone rubber.

Ang Solid Insulated Ring Main Unit (SIRMU) ay gumagamit ng solid insulating material bilang pangunahing insulation medium. Ang mga key conductive circuit components tulad ng vacuum interrupters at kanilang mga koneksyon, disconnecting switches, grounding switches, main busbars, at branch busbars ay individual o collectively encapsulated sa solid insulation, bumubuo ng isang o ilang modules. Ang mga modules na ito ay fully insulated, fully sealed, functionally specific, at designed para sa recombination at expansion. Ang mga human-accessible surfaces ay coated ng conductive o semi-conductive shielding layers at direktang at reliably grounded. Ang mga key characteristics ay kinabibilangan ng full insulation, full sealing, modularity, compact size, at karunungan. Ang mga SIRMUs ay nagpapakita ng significantly superior performance kumpara sa SF₆ RMUs sa resistensya sa harsh environments tulad ng extreme cold, mataas na altitude, humidity, at strong wind/sand. May fully sealed, waterproof design at walang exposed high-voltage conductors, sila ay partikular na suitable para sa damp at flood-prone areas, capable ng pagbibigay ng reliable power supply sa damp o submerged conditions.

​2.2 Paggamit ng Intelligent Protection Technology​

Ang integration ng microprocessor at computer technology sa electrical equipment ay nagbibigay nito ng intelligent functions habang nagbibigay ng bidirectional communication sa control centers. Ito ay bumubuo ng intelligent monitoring, protection, at network management system. Sa pamamagitan ng simple parameter configuration, ang isang single intelligent device ay maaring conveniently magperform ng mga functions na tradisyonal na nangangailangan ng ilang devices.

Ang structural design ng SIRMU ay sumasalamin sa mga requirement ng modern resilient smart grids. Ito ay gumagamit ng rapid algorithms upang bigyan ang circuit breakers ng fast tripping capabilities, nagbibigay ng mabilis na isolation ng faulty lines at effectively preventing cascading tripping. Equipped with a single-phase ground fault protection system, it enables online detection of such faults in ungrounded (or high-impedance grounded/PET/PEN) systems without needing additional configuration, providing alarms or trip commands according to set values. The main circuit employs single-phase modular design, which entirely avoids phase-to-phase short circuits during operation and significantly enhances maintenance efficiency while reducing costs. An integrated embedded operating system features a core CPU architecture, including an ARM processor (ARMP) for general processing and system control, alongside a powerful DSP for efficient multi-tasking, enabling high-speed data processing, control, and communication. The units are structurally compact, small in size, light in weight, and easy to install. Isolation gaps are visibly verified for safe operation. Automatic supply mode recognition enables flexible automatic changeover for dual power supplies, improving power supply reliability. Offering flexible communication support (GSM SMS, GPRS, CDMA universal wireless services, fiber, twisted pair, wireless, carrier), and supporting multiple communication protocols, facilitates easy implementation of distribution automation.

​2.3 Maintenance-Free at Eco-Friendly​

Ang main switch ay gumagamit ng maintenance-free vacuum circuit breaker na kilala sa stability at reliability, na hindi nangangailangan ng periodic maintenance. Ang integrated design ng disconnecting switch at grounding switch kasama ang circuit breaker ay nagbibigay ng compact structure na may reliable mechanical at electrical interlocks, effectively preventing misoperation.

​2.4 Key Manufacturing Processes at Quality Assurance para sa SIRMUs​

Upang matiyak ang production stability, consistency, at product quality—na nagbibigay ng guarantee sa long-term insulation withstand voltage ng SIRMU products—ang solid insulated poles ay gumagamit ng Automatic Pressure Gelation (APG) process kapag gawa sa epoxy resin. Ang manufacturing process requirements para sa SIRMUs ay lumampas sa mga requirements para sa SF₆ gas-insulated RMUs. Insufficient production process control significantly increases the likelihood and severity of hidden insulation defects and faults compared to SF₆ units. Stringent quality control of raw materials and advanced process capabilities are essential.

The external insulation of its vacuum interrupter is achieved through multiple media, including epoxy, silicone rubber, and air. Therefore, the insulation strength of individual materials and the interfacial treatment between different insulating media are crucial. Both epoxy and silicone rubber offer excellent dielectric strength, reaching 5-6 times that of air. Achieving this strength requires strict control over the molding process—optimal temperature and pressure—along with ensuring material degassing and venting during molding to avoid entrapped micro-bubbles. Failure to do so not only reduces insulation strength but also causes uneven electric field distribution, increasing partial discharge (PD) activity and posing operational risks. Interfacial treatment ensures sufficient interfacial insulation strength under stress, thermal cycling, etc., preventing insulation failure. Reliable detection methods for interface quality are necessary. Currently, PD measurement, X-ray inspection, and lightning impulse tests can accurately assess interfacial insulation strength.

Employing X-ray inspection as a factory test prevents defects like bubbles, pores, or cracks in solid insulation assemblies and ensures vacuum interrupters, their connections/terminals, and solid insulated busbars show no visually apparent abnormal deformations in X-ray images relative to their positions. Performing PD measurements prevents PD inception and extinction in weaknesses or defects within the SIRMU's insulation caused by high electric fields, avoiding cumulative degradation leading to insulation breakdown over time.

​3 Teknikal na Design Scheme para sa Intelligent SIRMU​

Batay sa malawak na karanasan sa distribution grid operation at analysis ng advanced domestic at international equipment, considering practical grid operation conditions and environmental requirements, we determined through comprehensive comparison to develop and apply the "Application Research of 10kV Intelligent Solid Insulated Ring Main Unit" project.

​3.1 Main Technical Content​

New AVR-12 type Solid Insulated Ring Main Units (SIRMUs) are installed at the original site. A dual-power supply configuration is utilized, leveraging the SIRMU's intelligent functions for rapid isolation of fault lines, quick detection of single-phase ground faults, and transmission of all switch information via optical fiber to the Distribution Automation Master Station (DMS) or via SMS to maintenance personnel phones. Utilizing the master station monitoring platform enables data statistics and fault analysis.

This project is implemented in the following aspects:

• Based on the original RMU scheme and considering user importance, power is supplied via dual incoming lines. During normal operation, Incomer #1 supplies power while Incomer #2 is on hot standby.
• The main equipment is the AVR-12 type Ring Main Unit, consisting of 7 bays: 6 circuit breaker (CB) bays and 1 Potential Transformer (PT) bay.
• The 6 CB bays adopt a CB + Disconnector (DS) + Grounding Switch (ES) structure, equipped with integrated protection devices.
• The PT bay uses a DS + single-phase PT structure, providing communication power. The PT can be switched in/out using the DS in the PT bay, allowing PT or line maintenance without requiring a complete SIRMU outage.
• Using CB-type SIRMUs allows multiple interruptions of short-circuit fault currents. Compared to fuse protection, besides eliminating the inconvenience and waste of fuse replacement, they provide comprehensive short-circuit protection coverage through setting adjustments.

​Normal Operation:​​
The intelligent controller acquires parameters (breaker status, disconnector status, primary current/voltage, zero-sequence current/voltage, DMS master station status) for each incoming/outgoing bay. Real-time data upload via optical fiber to the Intelligent Distribution Switch Master Station enables remote operation.

​Short-Circuit Fault:​​
The intelligent controller's rapid protection feature detects fault current and power flow within 15ms and clears the fault within 25ms, ensuring normal line supply, preventing cascading tripping, and minimizing outage scope. Instantaneous characteristics (voltage, current, switch status) allow control over the permanent magnet actuator's action characteristic, shortening the fault clearing time to quickly isolate the fault line. Simultaneously, the controller transmits SIRMU action information via fiber to the monitoring center, allowing timely assessment of product status and facilitating fault location and power restoration.

​Single-Phase Ground Fault:​​
The controller uses zero-sequence current magnitude/phase and zero-sequence voltage magnitude/phase to determine if a fault occurs on the SIRMU's load side. Only for ground faults on the load side does the controller issue a protection trip or alarm command and upload fault information via fiber. Faults on the source side do not trigger actions from this SIRMU's controller.

​3.2 Main Technical Challenges​

(1) Applying solid insulation technology and APG manufacturing process to ensure SIRMU reliability, long lifespan, and maintenance-free operation under high-temperature and high-salt-fog environments.
(2) Utilizing an integrated, flexible design concept combining the circuit breaker's high-voltage primary section with the secondary intelligent control section. Built-in combined current/voltage sensors enable real-time acquisition of primary voltage/current signals and switch status for flexible control of the breaker's actuator, optimizing vacuum interrupter operation.
(3) Rapid detection of fault current and execution of protection actions.

​Project Implementation:​​
This project employs solid insulated RMUs with integrated intelligent control devices. The main switch uses a combination device comprising a Permanent Magnet Actuated Vacuum Circuit Breaker (VCB) with integrated Disconnector (DS) and Grounding Switch (ES). Equipped with an intelligent control system, it performs automatic control functions even without DMS coordination. The permanent magnet actuator offers high reliability and maintenance-free operation. Optical fiber communication enables real-time collection of all RMU operating parameters, simplifying remote power restoration and power fault analysis, and accumulating experience for smart grid terminal devices. An external stainless steel cabinet minimizes future maintenance.

​4 Conclusion​

The Intelligent Solid Insulated Ring Main Unit (SIRMU) is a safe, eco-friendly, stable, reliable, and highly intelligent next-generation RMU. It is particularly well-suited for deployment in harsh locations characterized by high altitude, extreme temperature variations, contamination, and humidity.