Driven by ease of installation as well as service stability and good behaviour in the event of failure, dry type outdoor cable terminations and dry pluggable solutions for GIS and transformers have been used widely for over 25 years. More recently, driven by growing demand for such cable accessories in onshore and offshore substations, a special design has been realized for a range of applications, including pluggable terminations for GIS and transformers requiring off-shore certification, pluggable solid epoxy-joints and pluggable surge arresters. Moreover, cost optimized dry outdoor terminations now include an option to integrate the surge arrester and also the possibility to install all products onto ultra-bendable HV cables having EPR insulation.
Adapting any high voltage component for special new applications requires verification of design, which is one of the most important steps during the development and qualification process. One of the key challenges for the HV cable accessory is being suitable across different cable constructions that vary depending on manufacturer, customer requirements and operating conditions. Moreover, in order to verify accessory design, internal tests as well as official qualifications witnessed by or in a third party HV laboratory have to be performed.
This article, based on a presentation at the 2015 INMR WORLD CONGRESS by Matthias Freilinger of Pfisterer in Switzerland, discusses these applications and offers examples of how modern day cable accessories are being adapted to meet these needs.
Adapting Dry Outdoor Terminations for Substations
Dry type terminations are known to offer advantages, such as:
- No need for oil or gas insulation;
- Easy and safe installation on the ground;
- Reduced installation costs;
- Explosion proof behaviour.
Such terminations can be divided into two sub-groups: flexible or self-supported for various applications.
Both versions are well known on the market. The flexible type of termination is considered among the most cost effective solutions while the supported termination offers maximum mechanical stability, including a rotational system for lifting onto towers.
The first step in adapting these terminations to meet the requirements of substation applications is to combine both advantages. A flexible termination can be installed onto the cable while on the ground. It is then lifted onto a prepared support with an open baseplate. Due to height restrictions of 6 m and less cable weight, an optimized solution has been developed in regard to mechanical design, ease of installation and cost effectiveness.
Integrated Surge Arrester
In a second step, a combination product has become another option. Replacing the post insulator by integrating a surge arrester in its place offers significant space and cost savings during substation design. This combination product requires only the space of one conventional termination and is fixed onto the same support.