Innovation and Application of 12–24 kV Nitrogen-Insulated Ring Main Units

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• Using advanced insulating materials: replacing outdated materials to extend service life.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.