Innovative thermoplastic pole design sets new reliability and environmental standards for vacuum breaker technology

ABB has over 10 years of experience in the use of embedded pole technology based on epoxy insulation in medium-voltage circuit breakers with vacuum interrupters. The next significant step in this technology is the development of embedded poles that use a thermoplastic material. The technological challenge is to balance the different coefficients of thermal expansion of the ceramic, metallic and thermoplastic materials. Compared to the epoxy material used previously, the thermoplastic material has a lower density while its dielectric strength as well as its mechanical stiffness and strength are significantly increased. Function, form, processing and cost are also decisive factors. These superior features enable the thermoplastic pole to directly replace the epoxy pole since the outer dimensions of the epoxy poles are not exceeded; in addition, all the functional dimensions are kept constant. The contact terminal distance and their shapes as well as the bore pattern to fix the pole onto the circuit breaker are similar to the epoxy pole. Furthermore, self-tapping screws are used to fix the poles to the breaker, which ensures mechanical stability, both statically and dynamically, as well as already being successfully implemented with thermoplastic materials in other industries. With those advantages, ABB developed and launched the new generation embedded pole with thermoplastic, call PT1. All the above mentioned technical properties are achieved with this new technology. In order to guarantee all the necessary functionality over the product life-cycle, exhaustive tests have been carried out in addition to the IEC and GB standard. These include various mechanical, climatic and dielectric long-term tests as well as creep and relaxation. A further advantage of the PT1 pole compared to the epoxy technology is the reduction of the CO₂ emission, the capability to use fully automated production processes and the consequent improvement in quality control.