Views: 0 Author: Site Editor Publish Time: 2026-06-25 Origin: Site
High-voltage suspension insulators are critical components in power transmission systems, providing both electrical insulation and mechanical support for overhead lines. The reliability of these insulators is increasingly challenged by severe environmental conditions—pollution, fog, rain, and ice accumulation—which can lead to surface flashover and consequent power system outages.
Composite insulators, particularly those with silicone rubber housings, have gained widespread acceptance in electric power utilities worldwide due to their substantial advantages over traditional porcelain and glass insulators. Their low surface energy enables excellent hydrophobic properties under wet conditions, while their lightweight construction reduces tower design costs and maintenance requirements. However, the icing flashover performance of composite insulators requires further investigation, as the relatively short shed spacing makes adjacent sheds susceptible to ice bridging, reducing the effective leakage distance and lowering flashover voltage.
The shed profile—including shed diameter, spacing, inclination angle, and overall arrangement—has a prominent influence on the flashover voltage of polymeric insulators under wet and polluted conditions. Research has demonstrated that variations in shed geometry can impact pollution flashover performance by up to 22% for units with the same insulation distance.
2.1 Key Geometrical Parameters
The design variables for composite insulator optimization typically include the distance between sheds, shed radius, grading ring dimensions, and the physical properties of the insulator material. Among these, shed spacing is particularly critical: under non-uniform pollution conditions, larger shed spacing suppresses local arc bridging and increases flashover voltage. Insulators with densely arranged sheds are more susceptible to arc bridging, which compromises the effective creepage distance.
The IEC TS 60815-3:2025 technical specification provides systematic guidance for selecting appropriate insulator profiles, determining the reference unified specific creepage distance (RUSCD) from site pollution severity values, and applying correction factors for altitude, insulator shape, and size. This standard recognizes that shed profile correction is an essential factor in dimensioning insulators for polluted conditions.
2.2 The Optimization Paradox
An important insight from recent studies is that increasing leakage distance within a limited insulation distance—by excessively adding sheds or enlarging shed diameter—may paradoxically lower wet and pollution performance. This counterintuitive finding underscores the need for systematic optimization rather than simplistic geometric expansion. The finite element method (FEM) has emerged as a powerful tool for such optimization, enabling researchers to evaluate electric field distribution and creepage distance as dual criteria for shed parameter optimization.
Studies on polluted DC post composite insulators have shown that as the spacing between large sheds increases, the average electric field decreases gradually; as the overhang of large sheds increases, the average electric field increases by degrees; and as the difference between overhangs of large and small sheds increases, the creepage coefficient decreases monotonously. These findings provide valuable guidance for follow-up research on shed profile optimization.
The hydrophobic nature of silicone rubber materials is fundamental to the superior pollution performance of composite insulators. Weather sheds are typically fabricated from polymeric or elastomeric materials designed to provide extended creepage distance while presenting low surface energy for water repellency.
3.1 Hydrophobicity and Creepage Distance
The IEC TS 60815-3:2025 standard introduces the concept of hydrophobicity transfer and hydrophobicity transfer material (HTM), recognizing that a reduced creepage distance may be used for HTM insulators. This acknowledgment reflects the practical benefit of hydrophobic surfaces: by preventing the formation of continuous water films, hydrophobic materials effectively increase the electrical leakage distance across the surface and hinder the propagation of leakage currents.
3.2 Recent Advances in Hydrophobic Surface Design
Recent research on hydrophilic/hydrophobic alternating surfaces has revealed intriguing possibilities for enhancing flashover performance. When twenty 4 mm wide hydrophobic interfaces were distributed along a 16 cm creepage distance, the AC pollution flashover voltage was found to be 12.4% higher than that of a fully hydrophobic surface. The flashover voltage exhibited a saturated increasing trend as hydrophobic interfaces became more dispersed.
The underlying mechanism involves the coexistence of multiple dry bands induced by discrete hydrophobic interfaces, which enhances flashover withstand capability. These results indicate that appropriate design of hydrophobic interface distribution can achieve excellent pollution flashover performance even at relatively low hydrophobic coverage (≤50%).
The optimal design of high-voltage suspension insulators requires a holistic approach that integrates shed geometry optimization with hydrophobic surface engineering. Finite element method-based simulations using software such as COMSOL Multiphysics enable the evaluation of electric field distribution under various environmental conditions, including clean, uniformly polluted, and non-uniformly polluted states.
4.1 Design Considerations
Several critical factors must be considered in the optimization process:
· Shed spacing versus overhang: Proper ratio prevents arc bridging while maximizing protected creepage distance
· Shed inclination angle: Affects water runoff and pollution accumulation
· Creepage factor: An optimal creepage factor should be selected for insulators used in icing districts
· Hydrophobicity class: Maintaining HC1–HC2 levels is essential for long-term performance
4.2 Practical Implications
The economic and operational benefits of optimized insulator design are substantial. Enhanced creepage distance and hydrophobic performance translate to reduced maintenance requirements (less frequent insulator washing), improved reliability in heavily polluted environments, and extended service life. Hybrid solutions combining inorganic core materials with polymeric sheaths or silicone rubber coatings are increasingly adopted to leverage the mechanical reliability of ceramics with the hydrophobic performance of polymers.
The optimization of shed profiles for high-voltage suspension insulators represents a critical frontier in power transmission reliability. Research demonstrates that systematic optimization of shed geometry—considering spacing, diameter, inclination angle, and arrangement—can significantly enhance creepage distance and flashover performance without the paradoxical effects of excessive geometric expansion.
