Title of Invention

A MODULAR GAS -OIL BUSHING ASSEMBLY FOR DIRECT CONNECTION OF A GAS INSULATED ELECTRICAL POWER EQUIPMENTS

Abstract

This invention relates to a modular gas-oil bushing assembly for direct connection of a gas insulated electrical power equipment to an oil insulated electrical power equipment, said assembly comprising an insulated and voltage graded conductor (01), a gas side insulator (02); an oil side insulator (03), and an earthed enclosure (04), said insulated and voltage graded conductor (01) being disposed in a cavity formed by said two insulators (02,03) and said earthed enclosure (04), characterized in that two low resistance and expansion compensated electrical connectors (05,06) being provided at both ends of said conductors, said conductor (01) being coated with a conducting rubber (8) before being extruded with a polymeric insulation (9) and said insulators (02,03) having epoxy molded metal inserts provided with fluid sealing means at either end.

Full Text

FILED OF THE INVENTION The invention relates to a modular gas-oil bushing assembly for direct connection of a gas insulated electrical power equipment of different voltage class. The invention relates in particular to a modular gas-oil bushing assembly for direct connection of a gas insulated power equipment to oil insulated power equipment like transformers, reactors and capacitors. BACKGROUND OF THE INVENTION Conventional gas to oil bushings generally use a central metal conductor with a radial built-up insulation of resin impregnated paper (RIP) layers. Aluminum foil conductor is inserted, at regular intervals, in this radial insulation built-up, to modify the natural voltage gradient and achieve uniform voltage distribution across the insulation thickness. The length of the bushing on either side of the assembly commensurate with the medium (gas and oil). The conductor and insulator is housed in a metallic enclosure with suitable flanges featuring matching diamension for the two systems. The reliability of the above assembly governed by following parameters: . Quality of the RIP material and manufacturing environment, . Void free execution of the insulation and the grading. » Heat conduction and thermal expansion based i ncomp a ti b i1i t i es „ Creep—age of the insulation from one medium to other. . Leakage currents and partial discharge levels and « Life of seals and gaskets at interfaces. It is therefore an object of the invention to propose an improved gas-oil bushing assembly having higher insulation thickness achieving lower leakage currents. Another object of the invention is to propose a gas-oil bushing assembly constructed under modular method resulting in easy replacement of each modular component as opposed to replacement of the en ti re assemb1 y. Yet another object of the invention is to propose s modular gas-oil bushing assembly which maintains a low partial discharge level and eliminates creep-age of system fluid. A further object of the invention is to propose a modular gas-oil bushing assembly which is provided with a plug-in mechanism permitting stress-free expansion/contraction of the central conductor. Yet a further object of the invention is to propose a modular gas-oil bushing assembly which is simple to manufacture and cost- e f f e c t i v e . SUMMARY OF THE INVENTION According to the invention there is provided a modular gas-oil assembly for direct connection of a gas insulated power equipment to an oil insulated power equipment. The assembly comprising an insulated and voltage graded conductor; a gas side insulator; an oil side insulator; and an earthed enclosure, said insulated end voltage graded conductor being disposed in a cavity formed by said two insulators and said earthed enclosure, said two low resistance and expansion compensated electrical connectors being provided at both ends of said conductor. Further characteristics, advantages and purposefulness of the invention can be understood from the following description on the basis of the preferred embodiment shown in the accompanying drawings. The following are shown: Fig. 1 - A schematic total view of a conventional gas-oil bushing assembly. Fig. 2 ~ A schematic total view of a modular gas-oil bushing assembly according to a preferred embodiment of the invention. Fig. 3 - A cross sectional view of the embodiment of Fig.2 indicating in details insulation and voltage grading components;;.. DETAILED DESCRIPTION OF THE INVENTION In figure 1, a conventional gas-oil bushing has a central metal conductor (01) with an insulation layer consisting of resin impregnated paper (RIP). To achieve uniform voltage distribution across the? insulation thickness and to modify the natural voltage gradient, aluminimum foil conductor is inserted at regular intervals. The conductor (01) and the insulators (03,04) is disposed within a metallic enclosure (05) having suitable flanges. .Tn the invented modular assembly (Fig.2), four basic components are used. The insulated and voltage graded conductor (0.13), the gas side insulator {02), the oil side insulator -(03)- and an earthed enclosure (04}. The insulated and voltage graded conductor is placed in the cavity formed by said two insulators and said earthed enclosure. Two low resistance and expansion compensated electrical connection {05 and 06> are achieved by a plug-in arrangement, specifically incorporated in this equipment. Figure 3 gives the cross.--see t ion of the assembly detai .1 ing, insulation and voltage grading components C0S,09,10 and 11> and the earthed enclosure C043-. The electrostatic field, at high-tension end, is controlled using appropriate geometry of the insulator and shaping the HT conduction The central conductor (made from alloy copper/aluminum, Fig.3) is coated with a conducting rubber before extruding with a polymeric insulation. The insulation thickness is acting ss a controller with respect to the system voltage and the design. The outer surface of this insulation is covered by a thin layer of conducting rubber before application of another layer of a different but soft, mechanically, insulation. This insulation is molded to suit respective insulator in the system. A central but shorter layer of conducting rubber is finally inserted between the earthed enclosure and the insulated and voltage graded conductor assembly. The central conductor is tubular and hass provision for assembly of multilayer contacts at either end (Fig.2 item 05.06). The insulators are filled epoxy insulators with molded metal inserts. The profiled metal inserts are provided for controlling electrical field at HT end and to ensure firm electrical contact to the central conductor. Fluid sealing arrangements have been made in the insulators at either end. Elastomers have been used as sealants. The earthed enclosure is equipped with arrangements -for fixing the two insulators and is dimensioned such as to perfectly fit in the central conductor. Voids if any are plugged with silicon paste using special techniques. WE CLAIM 1. A modular gas-oil bushing assembly for direct connection of a gas insulated electrical power equipment to an oil insulated electrical power equipment, said assembly comprising an insulated and voltage graded conductor (01), a gas side insulator (02); an oil side insulator (03), and an earthed enclosure (04), said insulated and voltage graded conductor (01) being disposed in a cavity formed by said two insulators (02,03) and said earthed enclosure (04), characterized in that two low resistance and expansion compensated electrical connectors (05,06) being provided at both ends of said conductors, said conductor (01) being coated with a conducting rubber (8) before being extruded with a polymeric insulation (9) and said insulators (02,03) having epoxy molded metal inserts provided with fluid sealing means at either end. 2. The bushing assembly as claimed in claim 1, wherein an outer surface of said polymeric insulation (9) is covered by a conducting rubber layer (10) before being applied with an insulating material (11). 3. The bushing assembly as claimed in claim 2, wherein a layer (12) on the outer surface of said conductor (01) comprising a high permitivity material is applied to control an earthside or a low tension electrostatic field. 4. The bushing assembly as claimed in claim 1, wherein said earthed enclosure (04) is dimensioned to fit in said conductor (01) and having fixing means to accommodate said insulators (02,03) and wherein a silicon paste being used to fill when any voids arises between said conductor (01) and said earthed enclosure (04).

Documents:

895-del-2003-abstract.pdf

895-del-2003-claims.pdf

895-del-2003-correspondence-others.pdf

895-del-2003-correspondence-po.pdf

895-del-2003-description (complete).pdf

895-del-2003-drawings.pdf

895-del-2003-form-1.pdf

895-del-2003-form-19.pdf

895-del-2003-form-2.pdf

895-del-2003-form-3.pdf

895-del-2003-gpa.pdf

abstract.jpg

abstract1.jpg