Spatial double-wedge auto-compensated  contact mains russionenglish

The main specific design feature of Automatically Compensated Spatial Catenary (ACSC) is a new arrangement of the location of the contact wire and the messenger wire. There are several modifications. The basic design of an ACSC is shown below.





a = plan view

b = location of the wires fixed to the supporting pole

c = location of the wires under the tunnel vault

1 = messenger wires

2 = contact wires

3 = hinged strips

4 = fixing strips


The catenary consists of two messenger wires and of two contact wires. The messenger wires are located along both sides of the track axis and they are rigidly fixed through insulators to supporting points.


The contact wires which form a rhombic figure in a horizontal plane are located symmetrically in relation to the track axis. This is ensured through linking them with a hinged strip-out at the anchor span whereas in the middle of the span between two neighboring strips each contact wire is linked to the corresponding messenger wire through fixing components. The fixing components have a dual function: they serve as supporting points for the contact wire and at the same time they are used to fix the contact wires in relation to the axis of the track.


The length of a section of the ACSC is depending on the operational conditions. On mainlines the length of a section corresponds to the standard length of presently existing sections whereas on bridges and in tunnels they are reduced to correspond to the clearance of those structures.


Theoretical and experimental investigations resulted into developing a specific feature of the ACSC catenary and that is the self-compensating feature.


With the messenger wire and the contact wire being fixed rigidly onto the anchors the catenary seems to be non-compensated in terms of its form and implementation but in terms of its operational features it is indeed compensated. At a loaded status the contact wires generate load which is transferred to the messenger wires causing thereby a certain deformation of the latter. This load consists of two forces - a vertical force stemming from the gravitation force of the contact wire and a horizontal force stemming from the force generated by the zigzag of the contact wires.


As the temperature goes up the sagging of the messenger wires increases in the vertical plane while the wire goes down. The contact wires are expanding under the temperature impact as well as their tensioning declines. Due to this the angle of sagging of the contact wires changes at the fixing points and the horizontal forces affecting the messenger wires change correspondingly. Consequently the load upon the messenger wire increases as a function of reactional forces caused by the changes of the angle of fracture of the contact wires.


Similar processes take place in the messenger wires but the forces resulting thereof remain balanced. The precise corresponding of the changing forces to the temperature-effected expansion of the components of the system depends on the type of material used and on the specific design features of the catenary which are determined through calculations.


No horizontal displacement of the wires of spatial type catenaries has been observed with regard to the longitudinal plane of the track even with a semi-compensated alternative of this type of catenary. Temperature effected displacements normally take place in the transversal direction in relation to the axis of the track.


The ability of spatial type catenaries of self-compensation makes it possible to remove all restrictions as regards the length of the anchor section which, in this case, primarily is determined by the power supply and sectionalizing arrangement.


The expanding of the anchor sections on mainlines makes it also possible to do away with such a complex problem like their interfacing. Also there is no need any more for a frequent adjusting and the reliability of the catenary as a whole has been improved since most of the damages of current collectors take place at the points of power supply section interfacing.


Increasing the length of the anchor sections in a combination with the self-compensating feature of the spatial catenary when installing it in tunnels makes it possible to reduce construction work considerably. This is attained because cells for the housing of compensators can be dispensed with since any distance of the tunnel can be spanned with a single anchor section.


The spatial rhombic type of catenary is void of supporting wires as well as other fixing components which are part of the conventional type of catenary of mainlines. Due to this maintenance operations become much simpler. There is no need for any periodic adjustment whatsoever. The position of the contact wire is adjusted in the longitudinal and transverse planes during its installation only.


Running maintenance of such a catenary system can be arranged applying the so called "module" exchange method. In order to apply this method only suspension components are required, that is sets of insulators and components used to fix the contact wire to the messenger wire. The replacing of any of these components does not require much time. One more essential feature should be pointed out: the suspension system consists of standard parts and components only. There is not a single component which had not undergone intensive testing under operational environment. Yet the list of components of this catenary is smaller than that of a conventional catenary. All this contributes to an improved reliability of the spatial rhombic type of catenary.


In case of damages the zone affected is limited this is another most important operational feature. For instance, in case of disruption of one of the contact wires of the spatial rhombic type of catenary the tension is redistributed through articulated strips between the second contact wire and the messenger wires. The zone affected by the damage is limited to one link only. The length of the zone remains the same even if both contact wires are disrupted and this is due to the rigid fixing of the messenger wires at the suspension points. Thus, the length of the zone affected by a damage of the contact wires of the spatial-rhombic catenary is 15 to 20 times shorter (depending on the length of a link) compared to the vertically suspended type of catenary.


When carrying out repair operations involving the joining of the contact wires no adjustment of the suspension system is required at all. The contact wires are themselves taking their original position both in the longitudinal and transversal planes.


As there are neither dropping wires nor components to fix them with the new catenary which would require constant monitoring and maintenance, the scope of maintenance work is substantially reduced. Moreover, the complex work involved in the installation and adjustment of the spatial rhombic type of catenary does not exceed that required with the conventional type of catenary.


One of the most important features of any catenary designs is the change in the tension of its wires caused by atmospheric impacts that is by the impact of the temperature and by the load caused by changing the length of the wires, their positioning and tensioning.


When making mechanical calculations of the catenary, based on the knowledge of the clearance and the tensioning corresponding to certain temperature and load, parameters are identified which correspond to other environmental conditions as well. The dependence of the parameters of the wire upon the changes in the loads is determined, as it is known, by an equation of the condition.


When making calculations of the spatial catenary this tasks turns out to be far more complex compared to conventional catenaries. The reason for this lies in the necessity to take into consideration the changes in the wires in three dimensions which is needed for positioning of wires. Apart from distributed vertical loads the catenary is exposed to concentrated vertical and horizontal loads. They can not be replaced by distributed loads as it is done when making calculations for vertically suspended catenaries where simplified methods are applied.


T. Demchenko

D-r of Technological Science
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