1 Characteristics of Nitrogen-Insulated Ring Main Units
The new generation of nitrogen-insulated ring main units has the following main characteristics:
Excellent insulation performance. All live components are sealed inside, with external surfaces made of insulating material, effectively blocking current flow and preventing interference from external charged objects.
Strong resistance to external environmental conditions. Both the enclosure and internal insulation materials possess high resilience against natural disasters and adapt well to harsh weather conditions.
Low operating pressure, generally not exceeding 0.2 MPa.
Compact structure with minimized component spacing, enabling rational and centralized layout within a single space.
2 Development
2.1 Reducing Gas Gaps
Reducing gas gaps is an effective way to enhance insulation. Smaller gaps yield better insulation. Key methods include:
Using round busbars: helps reduce electric field non-uniformity and creates space for other components, lowering field intensity;
Employing high-performance insulating materials: blocks electron movement, significantly reducing charge distribution and field variations;
Adopting rotary switches: provides dual isolation breaks, shields electric fields at static contacts, and embeds flanges within insulating material.
2.2 Insulation Structure Design
The design involves two aspects:
Reducing electric field intensity around bushings: achieved by enhancing insulation strength, optimizing the height of grounding components, and shaping flanges and bushings (circular shapes outperform rectangular ones);
Optimizing support insulators: rationally designing the insulator radius in coordination with internal layout and shielding to reduce field intensity.
2.3 Shielding Effect
Shielding is critical for insulation performance:
Flange shielding: applying shielding around flanges, bushings, and insulation to reduce local electric field intensity;
Insulator shielding: installing metal shields near insulators to suppress electron motion;
Using advanced insulating materials: replacing outdated materials to extend service life. Additionally, nitrogen acts as an antioxidant, effectively preventing equipment oxidation.
3 Application
Nitrogen-insulated ring main units hold great promise in the eco-friendly power sector. In the early 21st century, SF₆-insulated units were widely used in power and industrial applications. Developing environmentally friendly alternatives aligns with sustainability goals and drives industrial upgrading. As a key link between power plants and end users, replacing this component with eco-materials brings mutual benefits to both utilities and society.
4 Conclusion
Ecological crises and ozone depletion highlight the severe environmental impact of SF₆. The development of 12–24 kV nitrogen-insulated ring main units replaces this greenhouse gas with zero-pollution nitrogen. By optimizing busbars, bushings, insulators, and shielding structures, these units significantly reduce environmental burden and contribute to environmental protection.
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