Highly efficient energy transmission between Overhead Catenary System (OCS) and pantograph is paramount for high speed railway lines. However this is not usually considered relevant for low speed railway lines. But interruptions in mechanical and electrical contact interfaces increase maintenance costs and can lead to EMI problems with its surrounding environment.
In order to avoid this, OCS systems are carefully designed using complex programs for calculation of pantograph/OCS interaction and compared with registered data. This means that it is necessary to invest valuable resources (time and money) to design a proper OCS.
At the end of the day, in order to obtain full benefits of a well designed OCS, both careful calculation and installation of all the elements of the system are a must. If no balance between design, calculation and installation is achieved, the overall procedure can present cost ineffectiveness due to wrong or careless installation.
The first step of a proper OCS installation process is taking into account all the geometrical and mechanical characteristics and restrictions of the system (maximum and minimum span lengths, slopes, cants, etc.) as well as the relative position of masts, portal structures and head spans to the track. The forces applied by the conductors to each mast and cantilever are established bearing all these data into account.
Cantilevers are calculated using these efforts as an input data together with all the geometrical restrictions that the system imposes, thus obtaining their complete geometry and the stresses and strains that they will have to support. These stresses and strains are compared to different standards as well as to rate and calculate masts and foundations. The geometric parameters of the cantilevers are used to prefabricate these elements in order to speed the installation process and to avoid onsite installation errors.
A precise calculation process is needed to assure that the contact wire is in the correct position.
That’s why a proper calculation tool is needed. CLARA, is a tool developed to perform geometrical and mechanical calculations of OCS cantilevers and rate both masts and masts foundations. This tool has been designed in AECOM Madrid Transportation Design Center by the authors. It is an IT tool that performs this calculation in a precise and quick manner, taking into account all the necessary input data and determining output data to the required level of detail as presented in this paper.
This tool provides useful data to design OCS controlling parameters that are of paramount importance for final OCS behavior. Some of these parameters are usually non-controlled due to onsite installation procedures. The authors believe that the use of this tool avoids recalculation, inefficiencies and systematic errors and hence it provides the basis for a more cost efficient design and building process.