How does armored withdrawable high-voltage switchgear optimize internal insulation in high-density electric field environments?

Publish Time: 2025-08-20

In modern power systems, with the continuous increase in power supply capacity and the growing demand for compact and highly reliable distribution equipment, high-voltage switchgear operates continuously in high voltage, high current, and complex electromagnetic environments. This creates highly concentrated internal electric fields, which can easily lead to serious faults such as partial discharge, insulation breakdown, and even arc short circuits. As the most widely used and mainstream switchgear type in China, armored withdrawable high-voltage switchgear significantly improves internal insulation performance in high-density electric field environments through a series of structural design optimizations and insulation technology upgrades, ensuring safe and stable operation of the power system.

1. Fully Enclosed Metal Armored Structure for Electromagnetic Shielding and Partitioned Isolation

The armored withdrawable high-voltage switchgear utilizes an all-metal enclosed structure. The switchgear body is constructed from high-strength aluminum-zinc-clad sheet metal or cold-rolled steel sheets, precisely bent and assembled to form a complete grounded metal enclosure. This structure not only provides excellent mechanical strength and internal arc resistance, but more importantly, provides complete shielding protection for high-voltage live components. By strictly separating the busbar compartment, circuit breaker compartment, cable compartment, and instrument compartment, and installing independent grounding barriers, electric field leakage and interphase interference are effectively suppressed, preventing creepage or air breakdown caused by concentrated electric fields. Furthermore, insulating partitions or metal shutters are installed between functional compartments, automatically closing when the circuit breaker is withdrawn or undergoing maintenance, further enhancing insulation safety.

2. Optimizing conductor layout and electric field distribution to reduce localized field strength

Under high voltage conditions, sharp corners and edges of conductors can easily cause electric field distortion, creating localized high-field intensity areas. To this end, armored cabinets utilize busbar structures with rounded corners and large curvature radii to avoid sharp angles and burrs. Grading covers (shielding covers) or stress cones are installed at all high-voltage connection points to ensure more uniform electric field distribution and significantly reduce the inception voltage of partial discharge. Furthermore, the busbar system is fully encapsulated with composite insulation or heat-shrink tubing, which not only improves insulation strength to ground and between phases but also effectively prevents dust and moisture intrusion that can cause creepage.

3. Select High-Performance Insulation Materials to Improve Dielectric Strength

High-performance insulation materials, such as SMC (unsaturated polyester glass fiber reinforced material), DMC (bulk molding compound), and epoxy resin castings, are widely used in the switchgear for support insulators, contact boxes, and partitions. These materials offer excellent dielectric strength, arc resistance, and aging resistance, maintaining stability under long-term high electric field stress. In particular, the encapsulated pole technology used in vacuum circuit breakers integrally casts the vacuum interrupter in epoxy resin, achieving integrated external insulation and significantly improving insulation reliability and environmental adaptability.

4. Enhanced Creepage Distance and Air Clearance Design

According to IEC and GB standards, armored withdrawable high-voltage switchgear requires sufficient air insulation distance and creepage distance in accordance with the rated voltage level. For example, for a 12kV system, the air clearance between phases and to ground must be no less than 125mm, and the creepage distance must be no less than 240mm. Furthermore, through appropriate layout, a safe isolation distance is maintained between the moving and static contacts even when the circuit breaker is in the test or disconnecting position.

5. Intelligent Monitoring and Environmental Control Assist Insulation Maintenance

Modern armored switchgear also integrates intelligent devices such as online partial discharge monitoring, temperature and humidity sensors, and condensation control systems to monitor the insulation status within the switchgear in real time. If abnormal discharge or excessive humidity is detected, the system provides an early warning and initiates heating and dehumidification to prevent insulation degradation.

For high-density electric field environments, armored withdrawable high-voltage switchgear utilizes metal shielding, electric field equalization, high-quality insulation materials, scientific gap design, and intelligent monitoring to create a multi-layered, comprehensive insulation protection system. This system not only meets the stringent reliability and safety requirements of modern power systems, but also provides a solid guarantee for continuous and stable power supply to power plants, substations, and large industrial and commercial users.