JPH0326017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas/liquid circulation self-cooling terminal junction box for power cables that utilizes natural convection.

For large-capacity power transmission cables (cross-linked polyethylene insulated vinyl sheathed cables, oil-filled cables, etc.), a method has been adopted in which the cable itself is directly or indirectly cooled with water or the like in order to suppress an increase in resistance due to heat generation in the cable. In this case, the capacity of the cable itself can be increased by forced cooling, but unless the capacity of the cable termination junction box can be increased, it is impossible to increase the capacity of the system as a whole.

For this reason, in the past, it was necessary to increase the size of the cable conductor at the terminal connection or to install a dedicated cooling system.For economic efficiency and ease of maintenance, a heat sink was installed at the top of the connection box. It has been proposed to utilize natural convection circulation of insulating oil to form a self-cooled terminal junction box. However, in this conventional self-cooling system, the temperature of the insulating oil, which has risen in temperature due to heat absorption from the cable conductor, drops while being carried to the radiator, making it impossible to obtain sufficient convection circulation and, therefore, reducing the cooling effect. It won't be enough.
In other words, the heat generated by the current in the cable conductor causes the temperature of the insulating oil filled through the cable insulator to rise,
This expands the insulating oil and reduces its specific gravity.
This will cause the oil to move upwards,
Heat is radiated from the oil within the radiator tube, increasing its specific gravity, canceling out the oil's circulation driving force and causing a loss of cooling effect. Therefore, conventionally, even if such a self-cooling system was used alone, it did not sufficiently contribute to increasing the capacity of the cable.

An object of the present invention is to provide a self-cooling type terminal junction box with excellent cooling effect by eliminating the conventional causes of inhibiting natural convection of insulating oil, thereby increasing the capacity of power transmission cables.

According to the present invention, a conductor pull-out rod is used as a gas/liquid passage to a radiator provided at the top of a junction box, and the cross-sectional area of the air/liquid passage portion of this pull-out rod is increased by heat generation due to the current flowing there. The above objective is achieved by selecting the temperature to be equivalent to the temperature of the gas/liquid flowing there.

The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 is a partial sectional view showing one embodiment of the present invention. In FIG. 1, since the structure of the terminal junction box is concentric, only the right half thereof is shown in cross section. Note that FIG. 2 is a sectional view taken along the line of FIG. 1. In Figs. 1 and 2, on the insulator of the cable 1 inserted through the insulator tube 2, there is an electric field relaxation part consisting of an insulation reinforcing layer 3 and a bell mouth 4, and a gap is provided on the circumference of the cable 1 and the electric field relaxation part. capacitor 5
is located. Further, a radiator 9 is provided at the top of the insulator tube 2, and the inside thereof is filled with an insulating oil 7 such as OF oil or silicone oil. The insulating oil 7 passes through the gap between the cable 1 and the capacitor 5, passes through the hollow part of the hollow conductor pull-out rod 8 connected to the tip of the cable 1, is led to the radiator 9, and is further passed from the radiator 9 to the capacitor 5. It passes through the gap between the pipe and the insulator 2, forming a circulation loop as shown by the arrow.

The conductor pull-out rod 8 is made of aluminum or copper, and is hollow as shown in FIG. selected.

According to such a configuration, the insulating oil 7 is thermally isolated from the outside air temperature due to the heat generated by the current flowing through the conductor pull-out rod 8, so that the oil temperature does not drop and the heat generated by the cable conductor is removed from the cable. The insulating oil 7 in the gap between the insulating oil 1 and the capacitor 5 absorbs the insulating oil 7, increases its temperature, expands, lowers the specific gravity of the insulating oil in this part, and rises toward the top of the radiator 9 in that state. From then on, as before, the insulating oil whose specific gravity has increased due to the heat radiated by the radiator 9 flows into the insulator tube 2 according to gravity.
and the capacitor 5 and descend through the gap.

As described above, according to the present invention, factors that weaken the circulation driving force due to natural convection are removed, sufficient circulation can be obtained, and therefore, a sufficient cooling effect can be obtained.

FIG. 3 is a diagram showing an embodiment in which the present invention is applied to a termination box in SF ₆ gas, in which an epoxy insulator tube 12 is used instead of the insulator tube 2 in FIG. 1, and an insulating tube 15 is used instead of the capacitor 5. The structure is basically the same as that shown in FIG. 1, and the effect is also the same.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of one embodiment of the present invention, and FIG.
The figure is a sectional view taken along the line of FIG. 1, and FIG. 3 is a partial sectional view of another embodiment of the present invention. 1... Cable, 2... Insulator tube, 3... Insulation reinforcing layer, 4... Bell mouth, 5... Capacitor, 7...
...Insulating oil, 8...Conductor pull-out rod, 9...Radiator.

Claims (1)

[Claims] 1. An insulating tube filled with an insulating gas or liquid, with a capacitor or insulating tube arranged with a gap between the cable and the electric field relaxing section placed on the cable insulator inserted into the insulating tube, and the above-mentioned insulating tube. In a termination box consisting of a heat radiator that allows circulation of insulating gas/liquid, a hollow drawer connected to the cable conductor is used as a gas/liquid passageway that connects the insulating gas/liquid in the capacitor or insulating cylinder to the top of the radiator. Using a rod, the cross-sectional area of the pull-out rod in the air/liquid passage portion is selected such that the pull-out rod generates heat to a temperature equivalent to the temperature of the air/liquid in that area due to the current flowing therethrough. A self-cooling terminal junction box for power cables.