Abstract
Santa Clara Valley Transportation Authority (VTA) required their original overhead contact system (OCS) along North 1st Street between interstate highway I-880 and West San Carlos Street at the Guadalupe River (opened in 1987) to be rehabilitated. HNTB was chosen to assist with the project and the first task included an overall inspection of the line to ascertain condition, operational deficiencies, and safety concerns. From this inspection, VTA prepared a scope of work for HNTB to perform and then prepare design documents for contractor bidding. During the inspection process, VTA further requested an evaluation of pole deflection in their Guadalupe Yard. Of interest is the line from Younger Street to the Guadalupe River at West San Carlos Street being joint pantograph and trolley pole compatible as VTA operates heritage streetcars during their Christmas holiday season.
The inspection of the OCS revealed deficiencies and safety concerns due to the age and type of equipment in use, most of it being original. Trolley frogs, crossover pans, and section insulators had field constructed gliders that were non-standard or inconsistent between assemblies. Trolley wires were suspended by clamps with no insulation requiring span wire insulators which made the span wire between the insulators alive at 750 volts. An open faced disconnect switch was too close to an apartment balcony with the possibility of the live parts being touched by people on the balcony, and some OCS poles were too short to raise span wires for adjustment. During inspection, a trolley wire broke at a trolley frog anchor tip and fell to the street at the pedestrian mall in downtown San Jose. VTA systems engineering had the idea of supporting the single contact wire supported and clamped to a Kevlar messenger wire. This support system in theory was proven to prevent the broken contact wire to hang 3.047m [10 feet] above ground, a CPUC G.O. 95 requirement. Similar Kevlar restraining supports were used by VTA to prevent the contact and messenger wires from falling down as a result of in-span insulator failure. VTA directed HNTB to use VTA’s idea to design a system of wire constraint using Kevlar synthetic rope to prevent wires from falling.
This paper describes the deficiencies and safety concerns discovered during inspection and how they were eliminated through creative OCS design. It further describes the process of inspection, direction, design, and operation of the rehabilitation project and how the use of Kevlar synthetic rope was used to keep trolley wire from falling during wire breaks both in theory and actuality. It also describes the issues encountered during construction, stagger issues from joint operation, pole extension implementation, and general improvements made to the OCS.
A meta-model for integrating safety concerns into systems engineering processes
