Dry type outdoor cable terminations and dry pluggable solutions for GIS and transformers have been developed now for over 25 years – driven by ease of installation as well as service stability and performance. In recent years, growing demand for such cable accessories at onshore and offshore substations has seen special adaptation of these for a wide range of applications. These include pluggable terminations for GIS and transformers with offshore certification, pluggable solid epoxy-joints, pluggable surge arresters as well as optimized dry outdoor terminations with the option of integrating a surge arrester along with the possibility to install these products onto ultra-bendable HV cables with EPR insulation. Adaptation of a high voltage component for any special application requires design verification, which is one of the most important steps during the development and qualification process. In the process, one of the main challenges for HV cable accessories is to be able to work with different cable constructions since these vary depending on manufacturer, customer requirements and operating conditions.
In order to verify accessory design, numerous internal tests as well as official qualifications witnessed by or in a third party HV laboratory must be performed. These are the topics of this edited article based on a contribution by Matthias Freilinger and Filippo Bionda of Pfisterer, Switzerland, from their presentation at the 2015 INMR WORLD CONGRESS.
Dry Outdoor Terminations Adapted for Substations
Adapting Mechanical Design
Dry type terminations are well known for many advantages:
• Dry design with no oil or gas insulation;
• Easy and safe installation;
• Reduced installation costs;
• Explosion proof behaviour.
These terminations can be divided into two groups: flexible or self-supported for various applications.
Both versions are well accepted on the market. While he flexible termination is one of the most cost effective solutions, the supported termination gives maximum mechanical stability – including a rotation system for lifting on overhead line towers.
The first step in adapting this design to substation applications is combining both advantages. The flexible termination can be installed onto the cable on the ground. Afterwards, it is lifted onto a prepared support with an open baseplate. With height limited to 6 m and less weight of the cable, an optimized solution is possible in regard to mechanical design, with easy installation and high cost effectiveness.