The invention relates to a silicone rubber composition having specific dielectric properties which can be used as insulator material in high voltage direct current applications and a method for the manufacture of cable accessories like cable joints. The invention comprises as well a method for the determination of the optimum dielectric properties and the related amount of dielectric active additives.

The present disclosure describes an electrical cable accessory system for covering an electrical cable and/or cable connection. The electrical cable accessory system includes a pre-expanded cable accessory unit and a time-temperature indicator associated with the pre-expanded cable accessory unit. The pre-expanded cable accessory unit includes a pre-expanded cable accessory formed of an elastomeric material and a removable holdout mounted within the elastomeric cable accessory, wherein the holdout is operative to maintain the elastomeric cable accessory in an expanded state and to permit the elastomeric cable accessory to elastically contract when the holdout is removed from the elastomeric cable accessory. The time-temperature indicator is configured to undergo a visible change in appearance in response to a cumulative heat exposure and signal to a viewer when the elastomeric material of the pre-expanded elastomeric cable accessory unit has experienced a threshold cumulative heat exposure. Methods including the same are also described herein.

The present disclosure relates to a joint system of a power cable, in which pressure-resistance performance of a boundary area between a power cable and a joint box for connecting power cables is improved.

The present disclosure relates to a joint system of a power cable, in which pressure-resistance performance of a boundary area between a power cable and a joint box for connecting power cables is improved.

Nonlinear composite compositions comprise a dielectric matrix material and flakes of a mixed metal oxide having the formula M1.sub.xM2.sub.yO.sub.z dispersed in the dielectric matrix material. M1 is selected from the group consisting of alkali metals, alkaline earth metals, and combinations thereof. M2 is a transition metal or post-transition metal, wherein M2 has an atomic number no greater than 78. The number x is in the range 0.3x1, y is a number in the range 0.5y1.5, and z is a number selected such that the mixed metal oxide is electrically neutral, wherein the amount of flakes in the nonlinear composite composition is sufficient that the nonlinear composite composition has a nonlinear increasing conductivity in response to increasing electric field. Methods of making nonlinear composite compositions and articles including them are disclosed.

A high-voltage device for receiving a high-voltage cable having a conductor designed to conduct an electrical current and a cable insulation surrounding the conductor, includes an insulation and a waveguide. The insulation includes an at least partly transparent or translucent field control unit from a siloxane polymer which is designed to at least partly surround the cable insulation of the high-voltage cable, the siloxane polymer including, in at least one portion of the field control unit, covalently bonded fluorophores and/or dielectric pigments. The waveguide is arranged such that a light signal caused by a partial discharge in the field control unit can be coupled from the field control unit into the waveguide.

A high-voltage device for receiving a high-voltage cable having a conductor designed to conduct an electrical current and a cable insulation surrounding the conductor, includes an insulation and a waveguide. The insulation includes an at least partly transparent or translucent field control unit from a siloxane polymer which is designed to at least partly surround the cable insulation of the high-voltage cable, the siloxane polymer including, in at least one portion of the field control unit, covalently bonded fluorophores and/or dielectric pigments. The waveguide is arranged such that a light signal caused by a partial discharge in the field control unit can be coupled from the field control unit into the waveguide.

The invention relates to a cable accessory, said accessory being surrounded by at least one electrically insulating crosslinked layer comprising at least one polymer material, boron nitride and silicon carbide, to an electrical device comprising at least said cable accessory, to a process for manufacturing said accessory and said device, to the use of said crosslinked layer around an electric cable accessory or in an electrical device, in particular for promoting heat discharge, to a kit for connecting electric cables, and to a cable accessory, said accessory comprising two fillers of different thermal conductivities.

Electrical field grading material which comprises a non-polar elastomeric polymer, a phyllosilicate filler and a carbon black filler, wherein any carbon black filler present in the electric field grading material has a dibutyl phthalate (DBP) absorption number from 30 to 80 ml/100 g. The above material may be used in electrical cable accessories, particularly electrical cable joints or terminations for medium or high voltage cable. The electrical field grading material according to the present invention has varioresistive properties, particularly a significant variation of electrical conductivity as a function of the applied voltage within a reduced voltage range, so as to guarantee a high value of conductivity above a critical value of the electrical field, and therefore to ensure an even distribution of the electrical field lines within the material.

Electrical field grading material which comprises a non-polar elastomeric polymer, a phyllosilicate filler and a carbon black filler, wherein any carbon black filler present in the electric field grading material has a dibutyl phthalate (DBP) absorption number from 30 to 80 ml/100 g. The above material may be used in electrical cable accessories, particularly electrical cable joints or terminations for medium or high voltage cable. The electrical field grading material according to the present invention has varioresistive properties, particularly a significant variation of electrical conductivity as a function of the applied voltage within a reduced voltage range, so as to guarantee a high value of conductivity above a critical value of the electrical field, and therefore to ensure an even distribution of the electrical field lines within the material.