In a connecting device of an electrical apparatus in which a first solid insulator and a second solid insulator each molded as a solid insulator on a periphery of a center conductor are connected to each other via a flexible insulator, a high voltage electrode having an outer diameter larger than those of the center conductors is disposed in the second solid insulator, and a ground electrode having an inner diameter smaller than that of an outer ground layer of the second solid insulator and larger than the outer diameter of the high voltage electrode is disposed in the first solid insulator. Electric field directions at an interface between the first solid insulator and the flexible insulator and at an interface between the second solid insulator and the flexible insulator are directions along the respective interfaces.

The present invention provides a millable silicone rubber composition characterized by comprising: (A) two raw alkenylated organopolysiloxane rubbers (A-1) and (A-2), i.e., a raw organopolysiloxane rubber including a molecular chain which is represented by a specific empirical formula and in which each of both terminals has been blocked with a trialkenylsiloxy group and a raw organopolysiloxane rubber including a molecular chain which is represented by a specific empirical formula and in which each of both terminals has been blocked with a monoalkenyldialkylsiloxy group; (B) an organohydrogenpolysiloxane having at least two silicon-atom-bonded hydrogen atoms in the molecule; (C) carbon black having an average primary-particle diameter of 100-350 nm; (D) reinforcing fumed silica having a specific surface area, as determined by the BET adsorption method, of 50 m.sup.2/g or greater; and (E) a platinum-group metal catalyst. This millable silicone rubber composition has an excellent electric-field relaxation ability, a high elongation at break, a reduced tension set, and high dielectric or insulating properties.

A medium or high voltage electrical device includes a housing, a central conductor provided within the housing, and a sacrificial cap configured for mounting on the housing. The sacrificial cap includes an outer housing, an insulated body, and a sacrificial conductor provided within the insulated body, wherein the sacrificial conductor electrically communicates with the central conductor within the housing when the sacrificial cap is mounted on the housing. A voltage test point terminal is provided within the insulated body and accessible via the outer housing of the sacrificial cap to capacitively couple with the sacrificial conductor. The sacrificial cap includes a portion configured to be physically severed to confirm that the electrical connector is de-energized.

A medium or high voltage electrical device includes a housing, a central conductor provided within the housing, and a sacrificial cap configured for mounting on the housing. The sacrificial cap includes an outer housing, an insulated body, and a sacrificial conductor provided within the insulated body, wherein the sacrificial conductor electrically communicates with the central conductor within the housing when the sacrificial cap is mounted on the housing. A voltage test point terminal is provided within the insulated body and accessible via the outer housing of the sacrificial cap to capacitively couple with the sacrificial conductor. The sacrificial cap includes a portion configured to be physically severed to confirm that the electrical connector is de-energized.

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 invention relates to a cable fitting for cables that can be used for high-voltage direct-current (HVDC) energy transmission, where the cable fitting has an electrically insulating layer, to a process for the production of an electrically insulating layer of such a cable fitting, and also to use thereof.

The present invention relates to a cable fitting for cables that can be used for high-voltage direct-current (HVDC) energy transmission, where the cable fitting has an electrically insulating layer, to a process for the production of an electrically insulating layer of such a cable fitting, and also to use thereof.

Provided are a high dielectric insulating silicone rubber composition and an electric field relaxation layer. This high dielectric and insulating silicone rubber comprises: (A) 100 parts by mass of an organopolysiloxane represented by formula (1),

R.sup.1.sub.nSiO.sub.(4n)/2(1),

(in the formula, R.sup.1 represents the same or different, substituted or unsubstituted monovalent hydrocarbon groups, and n is a positive number of 1.95 to 2.04); (B) 60 to 150 parts by mass of thermal black having an average primary particle size of 150 to 500 nm; (C) 5 to 100 parts by mass of reinforcing fumed silica having a specific surface area measured by a BET adsorption method of 50 m.sup.2/g or more; and (D) 0.1 to 10 parts by mass of a curing agent. The composition is characterized in that a cured product thereof satisfies a dielectric constant of 10 or more, a volume resistivity of 1.010.sup.13 to 1.010.sup.17 .Math.cm, a loss tangent of 0.1 or less, and a dielectric breakdown strength (BDV) of 7 kV/mm or more.

Electric field grading compositions comprise a particulate cupric oxide dispersed in a matrix material, wherein the electric field grading composition has a threshold voltage, a breakdown voltage, and exhibits a reversible electric field switchable current-voltage relationship that substantially follows the equation:
I=kV.sup.
wherein: I is current in amperes; k is a constant greater than 0; V is applied voltage in volts, wherein V is between the threshold voltage and the breakdown voltage, inclusive; and is a real number greater than 1. The electric field grading composition is useful for reducing electric field stress at a joint or termination of a conductive substrate. Articles including the electric field grading disposed on a surface of a conductive substrate are also disclosed.

Electric field grading compositions comprise a particulate cupric oxide dispersed in a matrix material, wherein the electric field grading composition has a threshold voltage, a breakdown voltage, and exhibits a reversible electric field switchable current-voltage relationship that substantially follows the equation:
I=kV.sup.
wherein: I is current in amperes; k is a constant greater than 0; V is applied voltage in volts, wherein V is between the threshold voltage and the breakdown voltage, inclusive; and is a real number greater than 1. The electric field grading composition is useful for reducing electric field stress at a joint or termination of a conductive substrate. Articles including the electric field grading disposed on a surface of a conductive substrate are also disclosed.