JPS646607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oil-filled power cable system for transmitting high voltages that includes at least one joint interconnecting a plurality of cables.

In conventional oil-filled high-voltage power cable systems, continuous cables are joined end-to-end by vertical joints or stop joints, and the two ends of the system are sealed ends. terminated by a section. In traditional single-core systems, a central oil duct is provided within each cable conductor, with a pressure tank connected at a suitable location, such as a sealed end or stop joint, to accommodate the load cycle. Thermal expansion and contraction of the oil during the
The pressure tank at the joint is filled by an oil stream that flows directly into the tank. Each stop
At the joint, a channel is formed extending from each conductor duct through the joint insulator into the space between the joint insulator and the inner surface of the joint casing, through which the external pressure tank and conductor duct are connected. Provides a direct flow of oil between. However, experience has shown that this oil channel is damaged not only when the joint is newly configured, but also especially after a period of time during system operation, when conductive particles suspended in the flowing oil - It has been observed that very often problems occur in electrical insulation when deposited on the insulating surfaces of channels.

According to the invention, the invention comprises at least two or more cables joined end-to-end by a cable joint, each of the cables having a conductor formed with a longitudinal duct; and a metal sheath surrounding the conductor and the insulator, the conductor duct is filled with insulating oil, and the oil further soaks into the cable insulation. and filling the space between the cable insulator and the cable sheath, and further configured to communicate with the space of the at least one cable during operation of the system. an oil supply pressure tank, such that during operation of the system, oil flow between the oil supply pressure tank and the conductor duct of the at least one cable is substantially controlled; caused by radial flow through the cable conductor and its insulation and longitudinal flow through the space of the at least one cable; means for electrically interconnecting the conductors of the cable; an insulator functioning to insulate the at least two or more cable conductors over their joint region; a casing surrounding the casing;
In oil-filled power cable systems,
The joint insulator extends from the outside to a region adjacent to the joint end of the cable conductor without directly communicating with the conductor duct,
An oil-filled power cable system is provided, characterized in that the oil-filled power cable system is formed with at least one channel that functions to facilitate bleed and initial impregnation of the joint insulation in the adjacent region.

Therefore, when the system is in operation, there is no or negligible oil flowing through the channels providing joint insulation. This is because, as mentioned above, the oil flow between the oil supply pressure tank and the cable conductor duct is essentially a radial flow flowing through the cable conductor and insulation and a space under the cable sheath. This is because it is caused by the longitudinal flow flowing through the Therefore, the accumulation of conductive particles suspended in the flowing oil in the channel is minimized. Channels providing joint insulation ensure that during the initial impregnation of the joint, the joint insulation is first sufficiently bled and then thoroughly impregnated with oil, even in areas adjacent to the joined ends of the conductors. Make it.

In each embodiment disclosed herein, the joint is a barrier joint, where a barrier joint is a joint configured to form a barrier between the oil systems of two cables. This means that each oil system is supplied with oil during operation of the system by communicating with the spaces below the sheaths of the individual cables. An oil supply pipe is led through the joint casing and directly into the space below the sheath of each cable. The end of each sheath is closed to separate the space beneath the sheath from the adjacent oil-filled space within the joint. The individual channels extend from the aforementioned individual joint spaces (one for each cable) to the area adjacent to the joined conductor ends. In each embodiment, the end of the conductor duct is closed, so there is no communication for direct flow of oil through the channel into the conductor duct. During operation of the system, the oil supply to the joint space occurs radially outward from the conductor duct via the cable conductor and the insulation.

An embodiment of the present invention will be described below with reference to the drawings.

Referring to Figure 1, it can be seen that two high voltage cables are joined end to end by a barrier joint, although the drawing only shows one high voltage cable and half of the joint. It will be understood. Although only one half of the joint is shown in FIG. 1, the other half is of substantially similar construction. Each cable (for example transmitting 400kV) has a conductor 1 formed with a central duct,
an insulator 2 (including an insulating layer and inner and outer screen layers) disposed around the conductor 1;
and a corrugated aluminum sheath 3 surrounding an insulator 2. On the underside of the sheath, a small space remains between the insulator 2 and the sheath 3 itself. Insulating oil is conductor 1
It is filled inside the sheath, penetrates into the insulator, and fills the space below the sheath.

Conventionally, the sheath and various insulation layers are cut from the ends of the cable conductors, and the exposed ends of the two cable conductors are mechanically and electrically interconnected by a joint ferrule 4. Each conductor duct is actually plug 5 as shown.
Closed by. Insulator 11 and ferrule 4 form a barrier between the oil systems of the two cables. The cutting end of each sheath is closed by a tubular closure member 6. The closure member 6 is sealed around the sheath itself at one end and around the cable insulation at the other end. A joint consists of an insulator 7 disposed around a section of cable from which some or all of the cable insulation has been removed for joining purposes, and a non-cutting joint extending longitudinally outwardly. Preformed paper tube insulation 8 surrounding a length of cable insulation
(one provided for each cable) and
Contains. The joint further includes a molded epoxy resin insulator sleeve 9 surrounding the ferrule and having a tubular stress relief electrode 10 embedded therein. Electrode 10
is electrically connected to the ferrule. The joint further includes molded tubular epoxy resin insulators 11 (one for each cable) fitted around the paper tube insulator 8 and inserted into each end of the insulator 9. There is. A paper insulator 12 surrounds insulators 9 and 11, and the complete assembly consists of a tubular metal joint.
It is enclosed within a sleeve 13. This complete construction is provided at each end with a closing plate 14 which is fixed to the outer end of the insulator 11. Each end of the joint is provided with a tubular metal end cap 15. The inner end of the cap 15 is fixed and sealed to the closure plate 14 and the outer end to the cable sheath 3. At the end of the joint shown, the end cap consists of two sections secured to each side of the annular insulator 15a.

For the initial impregnation of the joint, it is first necessary to bleed the joint. At each end of the joint, the space 16 in each end cap and the individual paper insulators 7 and 8 are evacuated through ports 17 in the end caps. To ensure that the paper insulators 7 and 8 are fully bleed, the joint insulators are provided with an area adjacent to the end of the cable conductor from joint space 16 (from joint space 16 and port 17). A channel 18 is formed which extends to a remote area. In the embodiment shown, the channels are made of insulator 11 and paper.
between tube insulator 8 (e.g. insulator 1
by a longitudinal groove formed on the inner surface of 1)
is provided and extends from the joint space 16 to the inner end of the insulator 8. The inner end of the channel 18 terminates in the space formed by the engagement of the insulator 11 and the ferrule 4 and the paper insulator 8. For example, four such channels are formed. Since the channel 18 extends into the area adjacent to the end of the cable conductor, it effectively bleeds air not only from the area adjacent to the joint space 16 but also from the area adjacent to the end of the cable conductor. It will be done. If this channel were not provided, not only would there be insufficient air extraction from the area adjacent the joint space 16, but there would be even less air extraction from the area adjacent the ends of the cable conductors. Probably. Following this bleed step, the joint is impregnated with oil, each space 16 and its insulation 7 and 8 being impregnated through the port 17, the entire impregnation being adjacent to the inner end of the cable conductor. This is ensured by channels 18 which provide a flow of oil to the area of the insulation. If the channel 18 were not provided, the oil impregnation of the insulators 7 and 8 would also be insufficient. Insulator 12 and space 21 within central sleeve 13 are bleed and then filled with oil via port 22. The joint further includes a pipe 19. A pipe 19 extends from a port 20 on the end cap 15 into the sheath closure 6 to carry oil from an external pressure tank and into the space below the sheath of the individual cables during system operation. It functions to provide direct communication. Therefore, when the system is in operation, the oil supply from the pressure tank is directed to the space below the sheath (this space is connected to the individual joint spaces 16 by means of the closure 6).
from which the conductor duct is fed by a longitudinal flow in the space below the sheath and a radial flow flowing through the cable insulation and conductor. During operation of the system, the flow of oil in the joint is from the conductor duct radially outward through the conductor and its insulation over the length of the cable between the inner end of the closure 6 and the ferrule 4. occur in the direction of The amount of oil flowing through each channel 18 is zero or almost negligible. In any case, the end of the conductor duct is closed by the plug 5, so that the channel does not provide direct communication into the conductor duct.

The joint space 21 shown in this embodiment communicates with the oil system of the other cables. This is then provided not at the joint shown, but at the joint at the opposite end of the other cable mentioned above. Each cable in the system is supplied with oil from a pressure tank. However, the oil supply need not necessarily be made at any joint for the other cables mentioned above; instead,
It may also be fed directly into the space under the sheath at other points along the length of the cable, for example via openings formed specifically for this purpose in the cable sheath itself.

Referring to FIG. 2, a variation of the barrier joint is shown. Parts common to those in FIG. 1 are given the same numbers. In this example, the channel 18 is radially connected to an annular stress control electrode 11a provided at the outer end of the insulator 11, instead of passing radially inwardly of the stress control electrode 11a as in the joint of FIG. It communicates with the joint space 16 by passing outward in the direction.
Thus, in the example of FIG. 2, channel 18 passes through an area that is subject to relatively small forces. The insulator 11 in the example of FIG. 2 has two parts: a tubular or trumpet-shaped part 11b with a flared outer end;
An electrode 11a is provided and a conical portion 11c fits within the flared outer end of the trumpet-shaped portion 11b with a channel 18 extending between the two aforementioned portions. For example, the channel 18 is formed in the inner surface of the trumpet-shaped portion 11b as a groove extending from its inner end to the junction with the conical portion 11c, and from there to the conical portion 11c.
It may be continuous as a groove formed on the outer surface of 1c.

[Brief explanation of the drawing]

FIG. 1 is a schematic longitudinal cross-sectional view of a barrier joint interconnecting two cables in an oil-filled power cable system;
The figure is a view similar to FIG. 1, showing a modification of the barrier joint shown in FIG. 1. 1...Conductor, 2...Insulator, 3...Sheath, 4
...Ferrule, 5...Plug, 6...Closing member, 7, 8...Insulator, 9...Sleeve, 10...
... Electrode, 11, 12 ... Insulator, 13 ... Sleeve, 14 ... Closing plate, 15 ... End cap, 16 ... Space, 18 ... Channel, 1
9...pipe, 21...space.

Claims (1)

[Scope of Claims] 1. A cable comprising at least two cables joined end to end by a cable joint, each of the cables comprising a conductor formed with a longitudinal duct, and the conductor and a metal sheath surrounding the conductor and the insulator, the conductor duct is filled with insulating oil, and the oil further soaks into the cable insulation. and filling the space between the cable insulator and the cable sheath, and further configured to communicate with the space of the at least one cable during operation of the system. Equipped with two oil supply pressure tanks,
Thereby, during operation of the system, the oil flow between the oil supply pressure tank and the at least one cable conductor duct flows substantially through the at least one cable conductor and its insulation. radial flow and longitudinal flow flowing through the space of the at least one cable, the cable joint electrically interconnecting the conductors of the at least two or more cables; an insulator that functions to insulate the at least two or more cable conductors over a joint region thereof, and a casing surrounding the cable and the joint insulator over the joint region. an oil-filled power cable system comprising: an oil-filled power cable system in which the joint insulator extends from its exterior to an area adjacent to a spliced end of the cable conductor without direct communication with the conductor duct; an oil-filled power cable system, characterized in that the oil-filled power cable system is formed with at least one channel that functions to facilitate bleed and initial impregnation of the joint insulation in the adjacent region. 2. The oil-filled power cable system of claim 1, wherein a closure is provided at the end of the conductor duct in each of the cables within the joint. 3. The joint insulator comprises a molded tubular insulation member disposed around the end of each cable, and the channel is formed on an inner surface of the tubular insulation member and An oil-filled power cable system as claimed in claim 1 or 2, comprising a longitudinal groove at the outer end of the member communicating with a joint space in the joint casing. . 4. The joint insulator comprises a two-part molded tubular insulating member disposed around the end of each cable, one of the two parts extending outside the other. a conical part fitted to the end, the channel being formed on the inner surface of the other part and extending from the inner end thereof to the junction with the conical part, and continuous between the two parts; 3. The insulating member of the two parts is provided with a longitudinal groove at the outer end communicating with a joint space in the joint casing. oil-filled power cable system. 5 The oil supply pressure tank is connected to the cable via the joint casing.
An oil-filled power supply according to any one of claims 1 to 4, which is connected directly into the space of each of the cables via a closure member arranged at the end of the sheath. cable system. 6. Any one of claims 1 to 4, wherein the oil supply pressure tank is connected outside the joint via the sheath of each of the cables and directly into the space. Oil-Filled Power Cable System as described in .