Electrification of the New York, New Haven, and Hartford Railroad

The New Haven's electrification was the first of its kind; no previous railroad had practical experience operating a high voltage distribution system above a steam railroad. Many of the system's ultimate specifications were the result of educated design decisions based on the state of the electrical technology in 1907.

Proposals were obtained from General Electric (GE) and Westinghouse. Both companies submitted a variety of AC and DC schemes, though GE favored DC electrification. But New Haven chose single-phase AC at 11 kV, 25 Hz as proposed by Westinghouse, who had been researching AC electrification of railroads since 1895 and in association with Baldwin supplied Baldwin-Westinghouse locomotives. Later GE also supplied some locomotives.

Voltage

The designers considered several voltages for the transmission segment of the system including 3–6 kV, 11 kV, and 22 kV. Ultimately, the transmission and catenary systems were combined into a transformerless system, that utilized the same voltage from output of generator to catenary to locomotive pantograph. As 11 kV was the highest voltage that could be obtained directly from the output of the generators of 1907, 11 kV was selected as the transmission and catenary voltage of the system.

Frequency

The New Haven had considered two different operating frequencies for use in their electrification: 15 Hz, and 25 Hz. Although 15 Hz was desirable from an engineering perspective, as it would afford a reduced motor size, lower inductive losses, and a higher motor power factor, choosing that frequency was viewed by the railroad as akin to a "break in gauge", thus limiting the commercial prospects of their system. 25 Hz had by 1907 already become a commercial standard, and the railroad already operated a number of trolley power houses at 25 Hz and had equipped many of its shops with 25 Hz motors; thus, the railroad selected the 25 Hz standard.

Catenary

The New Haven had no precedent to follow when designing its catenary system. Overhead catenary had previously been the domain of trolleys, except for a few three-phase railways in Europe. No prior experience existed with operating high-speed railways with an overhead contact system. The catenary designed by the New Haven was a unique, relatively rigid triangular cross-section.

The triangular cross-section of catenary used in the original electrification was only repeated by one other railway. The London, Brighton and South Coast Railway used a similar triangular catenary from 1909 until 1929. The New Haven's 1914 extensions dispensed with the triangular catenary design.

Catenary support spacing was set at 300 feet (91 m). This was based on keeping the straight line deviation from center of track to within 8.5 inches (220 mm) with a curve radius of 3 degree, which was the tightest curve between the original system's termini at Woodlawn and Stamford.

Generators

The generators at the Cos Cob Power Station were designed to supply single-phase power directly to the catenary. They were also required to supply three-phase power both to the New Haven itself for use along the lines, and to the New York Central's (NYC) Port Morris generating station to compensate the NYC for the power consumed by New Haven trains on the NYC's third-rail supplied line to Grand Central Terminal. The Cos Cob generators were three-phase machines, but wired to supply both three phase and single phase power simultaneously.