FI72233C - Conduit building component functions as a device for the prevention of arc damage. - Google Patents

Description

1 72233

The present invention relates to an arc damage component acting as an arc damage prevention device for use in connection with coated alloy aluminum open conductors treated by a precipitation hardening process, comprising an elongate at least one end for attaching a solid body and means to the body.

If, for one reason or another, bright arc lights ignite, for example, between two phase conductors, it will travel towards the load without damaging the conductors.

However, in the case of insulated conductors, the insulating plastic constitutes an obstacle to the propagation of the arc, leaving it burning at the insulation interface, or to 15 holes in the insulation, damaging the conductor.

Under normal circumstances, an overshoot occurs and the arc ignites on the pole at the point where the wires are attached.

Various devices have been developed to prevent conductor damage such as that described above. U.S. Patent No. 4,398,057 discloses a method in which a conductor is peeled from an insulator under a bond and metal pieces are placed at the exposed conductor and insulation interfaces. The arc propagates after igniting the peeled part of the conductor into the load-side metal body and remains on it without damaging the conductor.

In the devices according to Finnish patent applications 832181 and 832182, an additional mass is placed at the ends of the conductor hanger. The hanger is connected to a galvanically coated conductor, whereby after a possible arc ignites, it burns the end of the hanger and the conductor remains intact.

The base point of the arc thus moves towards the load-side end of the metal piece mounted at the interface of the insulation, and the arc remains in place until the relaying of the wire 35 cuts off the circuit, whereby the arc goes out.

2,72233

Nowadays, however, it has been found that the use of arc damage prevention devices such as those described above is associated with problems which weaken the conductor from the point of attachment of such a device and may even lead to cable breakage. One such problem is related to wind-induced conductor vibrations, the inflection point of which forms at the device in question. Since the higher the amplitude of the device, the greater the amplitude of such wind-induced conductor oscillations, attempts have been made to reduce the mass of the device to the amount necessary to withstand the burning effect of the arc. Surprisingly, this has not been found to be of much help in improving the durability of the conductor.

It has now been realized that when an arc burns, thermal energy is transferred to a metal body, causing the body to heat to a certain temperature. This temperature depends on e.g. the magnitude of the oi-blocking current, the burning time of the arc, the heat capacity of the metal mass, and the environmental conditions. From the hot metal mass, the thermal energy is transferred partly to the conductor in galvanic contact with the mass 20, whereby the temperature of the conductor also rises, and partly to the ambient air.

It is this heat transferred from the metal mass to the conductor that can cause the strength of the conductor to deteriorate. In the case of aluminum alloy conductors reinforced with a precipitation hardening process, the danger is high if the metal mass is dimensioned too small. Measurements have shown that an aluminum alloy with conductors, e.g. about a minute at a temperature of ^ + 200 ° C, is sufficient to drop the tensile strength of the conductor by 30 <10%. Because the temperature of the arc is in the order of thousands of degrees, the metal body heats well above +200 ° C at the base of the arc.

Thus, in order to maintain the strength of the conductor, it is essential to transfer the thermal energy in the metal core to the ambient air as quickly as possible instead of the conductor.

Il 3 72233 This is accomplished in the present conduit component such that the body portion associated with the massive portion or portions comprises protruding rib-like portions for cooling the massive portion or portions. These rib-like parts may perhaps be most preferably axial with respect to the body, but may also be transverse or possibly otherwise fitted in an effort to provide the component with the largest possible outer surface area to provide efficient cooling.

The cable construction component according to the invention, which acts as an arc damage prevention device, can act either as an arc damage prevention device per se or as various types of suspension brackets provided with suitable accessories or as a fastening part for earthing.

15 By equipping the component with ribs, its total female weight can be reduced, which reduces vibration damage and manufacturing costs, and also simplifies storage, transport, etc. With the help of the ribs, the component is also mechanically very strong, despite the lower mass.

In the following, one exemplary embodiment of the invention will be described with reference to the accompanying drawing, in which Figure 1 shows a component in partial section, Figure 2 shows a cross-section of the component of Figure 1 in the direction of arrows II-II in Figure 1, and Figure 3 shows the component of Figure 1.

Figures 1 to 3 show a wire construction component suitable for use mainly in accordance with U.S. Pat. No. 4,398,057 and FI Patent Application No. 842102. It comprises a body 2 which is in two parts and arranged around the coated conductor 1 in galvanic contact with its conductor. At one end 35 of the body 2 there is a solid part 4 shaped to be rounded and at the other end there is an elongate part with ribs 3. The ribs 3 4 72233 are axial in the embodiment of Figures 1 and 2 in order to maximize their connection surface and thus the heat conduction surface to the massive part 4. However, other rib positions are also possible.

The body part 2 is axially split in the middle as shown in Figures 2 and 3 and the parts can be connected to each other around the conductor by means of bolts 5 and 6. The splitting of the massive part 4 into the halves 4a and 4b is formed in a stepped manner in order to prevent the formation of a straight gap between the bare conductor and the environment. The spherical part 4 of the body 2 further has an inlet formed around the entry point of the conductor 1, by means of which it can be ensured that the bare conductor does not extend beyond the massive part 4.

In practice, the component according to Figures 1 to 3 is mounted so that the massive part 4 is located in the direction of the load. If this direction can change, as can happen in the case of ring nets, a component with a solid part at both ends can be used. Such a basic structure is also suitable as a starting point for forming hangers or earthing connection parts.

Only one substantially exemplary embodiment of the invention has been described above, and it is to be understood that the basic principle of the invention, i.e. cooling improvement, can be applied to all corresponding components without departing from the scope of the appended claims.

Il

Claims (2)

5,72233 A wire construction component acting as an arc damage prevention device for use in connection with coated alloy aluminum open conductors (1) treated by a precipitation hardening process, comprising an elongate body (2) at least at one end and means (5, 6) for attaching the body to the conductor, (4) or the part of the body 10 (2) associated with the parts comprises projecting rib-like parts (3) for cooling the massive part (4) or parts in a manner known per se. Cable construction component according to Claim 1, characterized in that the rib-shaped parts 15 (3) are axial with respect to the component body (2).