CTC Insulators has the quality certification ISO9001. World Class supplier of Composite insulators established in 2002 in Dalian, China. But there are also terminations still under operation that are filled with mineral oil in spite of the fact that environmental impact of leaks has caused the shift in technology towards the silicone oil, which is also non-flammable. The consequence is a relatively high viscosity if the stress cone is made from silicone. A certain chain length of silicone molecules is necessary to avoid migration into the silicone rubber of the stress cone. 1: Typical outdoor termination, filled with silicone oil.Īs mentioned, silicone oil is the main insulating fluid in use these days. The outer insulator can be porcelain or a composite housing, depending on customer preference. The main component of this accessory is the stress control element, which uses a semi-conductive electrode made of silicone rubber or EPDM for geometric field grading.

Much the same design is used for voltages Un = 60 kV to 500 kV. These can be classified into indoor terminations for connection with transformers and gas-insulated switchgear or outdoor terminations for connection to an overhead line or switchyard.ĭesign of Fluid-Filled Outdoor TerminationsĪ typical fluid filled outdoor cable termination is shown in Fig.

This edited 2015 contribution to INMR by Jan Debus of Brugg Cables in Switzerland described methods to assess terminations used on cables with extruded insulation and which are the interfaces to other components of the power grid. The key parameters in this regard are moisture content, dielectric properties and dissolved gases. Most outdoor terminations these days are filled with an insulating fluid, typically silicone oil, and a diagnostic of this fluid therefore offers another means of overall assessment, apart from PD measurement. Temperature measurement on the cable surface and partial discharge sensors are examples of such monitoring systems and partial discharge measurements are established tools for condition assessment of cable accessories as well. There are mature technologies that allow both continuous monitoring and also periodic assessment of the condition of a cable system. This aspect is also relevant for cable systems with extruded insulation. For example, diagnostics of oil-filled cables is important for transmission system operators to provide an indication of remaining lifetime. Condition assessment of power transmission devices such cable systems is essential for their reliable operation.

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