Cable train : a platform for in-situ manufacturing of underground cable

Abstract

As the demand for and viability of renewable energies has increased, connecting remote power generation stations to demand centers has become more important. High Voltage Direct Current (HVDC) transmission systems offer efficiency and cost effectiveness over long distances, allow for the linkage of incompatible AC grids, and can be immune to telluric currents and aggressive EMP attacks, which all make these systems particularly applicable to connecting to remote renewables. With the current state-of-the-art in HVDC, overhead lines (OHL) are several times cheaper than underground cables (UGC). However, OHLs have security risks and create substantial visual pollution, which has resulted in significant public opposition and lengthy delays in project permitting. Project developers have reluctantly agreed to replace portions of overhead line with underground cable as a concession to these stakeholders. One way to make UGCs more attractive to developers is to reduce cost by locating UGC systems along railroad right of ways. The increased mobility of heavy machines and materials on railroads and the state-of-the-art in railroad construction machinery provide both precedent and process advantages, which make the concept of augmenting railroads with underground cable systems an attractive one. The practice of installing and maintaining such systems could be less complex than traditional methods required by independent transmission corridors. The use of private railways may avoid conflicts with external stakeholders and eliminate the regulatory delays that have plagued many renewable energy transmission projects. Additionally, taking advantage of the increased accessibility of railroads by in-situ manufacturing high voltage, extruded cable in lengths far greater than what is currently able to be transported by road haulage, may reduce overall project costs by eliminating expensive and vulnerable cable splices. To accomplish this, here we present a method for continuously manufacturing and installing high voltage undergourd cable from a moving "Cable Train" using public-private railway systems. There are three primary challenges associated with such a mobile platform -- extrusion, curing, and degassing. Several promising countermeasures have been presented, which require varying levels of further development continuous extrusion, horizontal curing, and inline degassing. Herein, further discussions on standards, system topology, earthworks, practical limitations to cable production length, and cost estimation, can also be found. The technology and methods to accomplish this vision can be achieved by a pre-competitive technology consortium with member companies capable of completing and fully realizing the proof-of-concept designs proposed.