Tech Trends

2018-07-05 00:00:00    来源:    点击:71   

     Substations were either solid core porcelain or composite insulIn the past, the main options for support insulators at air-insulated HVAC ators up to 245 kV. In addition, RTV coatings have at times been applied to solid core porcelain post insulators to improve their pollution performance. New developments have recently been made when it comes to gas or foam-filled hollow core composite insulators as well as larger core diameters on solid core composite insulators. Nevertheless, the requirements for EHV and UHV AC installations in terms of length, mechanical strength, permissible deflection, creepage distance, shed profile and pollution performance still present a challenge for all existing insulator technologies. Realizing the need for high strength as well as low deflection under loads for applications such as earthing switches, disconnectors, reactors and busbar supports, a program was launched to develop hybrid post insulators. The basic concept was to combine the known service experience reported for solid core porcelain posts with the proven pollution performance of insulators with silicone rubber housings. The challenge was to provide a reliable and cost-effective solution that combines the mechanical advantages of solid porcelain and the electrical advantages of silicone housings for high pollution requirements. Selected design tests as well as electrical and mechanical type tests were conducted according to relevant IEC standards for composite and ceramic insulators. In addition, a long-term field test was set-up to establish more confidence in the concept. This installation was energized at 145 kV AC in May 2012 at the Koeberg Insulator Pollution Test Station (KIPTS) in South Africa and has provided final qualification for the new product. In addition, 420 kV AC hybrid posts were chosen for trial installations across several applications. This INMR article from 2015, contributed by Gustav Gödel, summarized the experience developing, designing, manufacturing, testing and applying post insulators made of ceramic and silicone materials, i.e. hybrid post insulators having a ceramic solid core.

 

     The aim of this project was to establish hybrid station post insulators as an alternative for power engineers across a range of support functions in AC high voltage apparatus as well as at HVAC substations. The porcelain solid core post insulator with external metal fittings is the most widely used type of station post insulator. Standard values for electrical and mechanical characteristics and dimensions – essential for the inter-changeability of these post insulators – are provided in IEC 60273 and ANSI C29.9. The ceramic solid core design provides advantages in terms of bending strength and deflection under bending load, and also for torsion and compression loads. In fact, this insulator type is used for all kinds of applications where these properties are required. Specific HV apparatus such as disconnectors and earthing switches are especially sensitive to deflection under load. Also busbar support applications need high mechanical strength and stiffness to cover short circuit demands as well as to carry wind loads without deflection. Support posts under reactors, filters and in capacitor banks face further compression loads.

     Many improvements in production technology and design optimization have been realized over the past several decades and alternative solutions have been developed in terms of pollution resistance, size and weight. These have included:

• Porcelain solid core post insulator with application of room temperature vulcanizing (RTV) silicone rubber coatings;
• Solid core composite station post insulators manufactured of fibre-reinforced resin tubes with silicone rubber housings;
• Gas or foam-filled hollow core composite station post insulators manufactured of fibre-reinforced hollow tubes with silicone rubber housings.

 


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