What are the unique features of the normal pressure sealed fully insulated ring main unit (NPS) in improving insulation performance?

Publish Time: 2025-10-15

In modern urban distribution network construction, ring main units (RMUs), as key node equipment in the power system, undertake crucial functions in energy distribution, protection, and control. With increasing demands for power supply reliability, environmental friendliness, and space efficiency, traditional RMUs using SF6 gas as insulation have gradually exposed issues such as the greenhouse effect, potential leakage hazards, and complex maintenance. As an innovative power distribution device, the normal pressure sealed fully insulated ring main unit, with its unique structural design and insulation technology, demonstrates significant advantages in improving insulation performance, making it an ideal choice for the development of green smart grids.

1. Environmentally friendly dry air insulation achieves stable dielectric strength at zero gauge pressure

The core innovation of the NPS lies in its use of clean, dry air as the primary insulation medium and its operation at zero gauge pressure. Unlike traditional high-voltage gas insulation, which relies on high gas pressure to enhance dielectric strength, this device achieves excellent insulation performance even at ambient pressure through its sophisticated sealing structure and fully insulated design. Dry air is non-toxic, non-flammable, and has no greenhouse effect, completely eliminating the environmental and safety risks associated with SF6 gas leaks. Furthermore, as a natural medium, air is chemically stable and will not age or decompose over long periods of operation, ensuring long-lasting and reliable insulation performance.

2. Fully enclosed, fully insulated structure eliminates external environmental interference

This ring main unit utilizes a fully sealed metal enclosure. All live components, including busbars, switch contacts, and connection terminals, are completely enclosed in solid insulation material, creating a "fully insulated, fully sealed" protection system. This structure effectively isolates the insulation from the effects of external dust, moisture, salt spray, and contaminants, making it particularly suitable for harsh environments such as high temperature, high humidity, coastal areas, and industrial pollution. Even in heavy rain, condensation, or extreme temperature swings, the equipment maintains stable insulation levels, significantly reducing the risk of flashovers, short circuits, and other faults caused by foreign objects.

3. Vacuum arc extinguishing technology improves insulation recovery during the switching process.

During switching operations, arcing can instantly damage local insulation. Atmospheric pressure sealed ring main units (RMUs) use vacuum circuit breakers or vacuum load switches as their core arc-extinguishing components. Arcs are difficult to sustain in a vacuum environment, so they are rapidly extinguished when the current crosses zero, and the dielectric recovers quickly, effectively preventing reignition. This feature not only extends equipment life but also rapidly restores system insulation strength after frequent operation or fault interruption, ensuring continuous and stable grid operation.

4. Optimizing Electric Field Distribution to Prevent Partial Discharge

The fully insulated design not only provides physical protection but also eliminates electric field concentration points and suppresses partial discharge through electric field homogenization technologies, such as shielded electrodes, stress cone structures, and smooth surface treatments. Partial discharge is a contributing factor to insulation aging, and long-term presence gradually weakens insulation performance. The RMUs utilize sophisticated electric field management to ensure no significant partial discharge under both rated voltage and overvoltage conditions, thereby extending the service life of the insulation system and enabling maintenance-free operation for over 20 years.

5. Modular Design Ensures Insulation Consistency and Extended Reliability

The equipment utilizes a modular architecture, with each functional unit being a separate, sealed, and insulated module. Modules are connected via fully insulated connectors, ensuring quick installation and stable electrical performance. This design not only facilitates flexible expansion but also ensures consistent insulation standards throughout the entire system, preventing insulation weaknesses caused by improper on-site assembly and improving overall system insulation reliability.

6. Oil- and Gas-Free, Intrinsically Safe, Reducing Operation and Maintenance Risks

Because it does not use SF6 or insulating oil, the equipment is leak-free, explosion-proof, or toxic, making it intrinsically safe. During routine operation, it requires no gas pressure monitoring, gas replenishment, or exhaust gas recovery, making it truly maintenance-free and significantly reducing operation and maintenance costs and safety risks.

The normal pressure sealed fully insulated ring main unit utilizes a technical combination of "normal pressure dry air + fully enclosed + fully insulated + vacuum arc extinguishing" to achieve a high degree of insulation safety, environmental friendliness, and reliability. It not only adapts to complex and changing operating environments but also meets the demands of sustainable development. It provides an efficient, green, and intelligent power distribution solution for urban power grids, industrial parks, commercial buildings, and other scenarios, and represents a key direction for the future development of medium-voltage distribution equipment.