Power Supply Study and New Rectifier Installation for the United Electric Railways of Providence

A study of the power supply to the United Electric Railways was initiated when new construction necessitated the re-location of rotary converters. Replacement with modern equipment was considered in conjunction with a comprehensive study of the entire power supply. It was evident that the losses on the United Electric Railways feeder and trolley system would be the controlling economic factor. A method of calculating the losses in this d-c supply system was developed, correlated with a measured value of losses, and extended to determine the relative merits of proposed feeder changes and rectifier installations. It is believed that this is the first published study that has made use of available probability methods for calculating losses, voltage drop, flicker, and capacity requirements in a study of the power supply for an electric transportation system. The rotary converters were replaced with 60-cycle rectifiers at two new locations. The design of these substations incorporated certain novel features for the protection of equipment and personnel.