Plant Technology Chester Electric Power Station - PECO Energy, Chester Pennsylvania

In the first decades of commercial electricity generation, the question of whether large consumers of electricity should build their own dedicated sources of power or obtain it from central stations operated by utilities sparked much discussion in engineering periodicals.

Several early power stations were designed specifically to provide direct current for street lighting systems, including the Sansom Street Station of Philadelphia's Edison Electric Light Company, heralded as the largest in the world when completed in 1890. For large industries and railroads considering electrification, construction of an "isolated" power plant had the advantage of independence from public utilities, still known for high rates and low dependability. Recognition of the substantial value of the contracts at stake in the isolated versus central station debate pressed utilities to enhance and promote the benefits of central station power. Aside from the challenge from isolated plants, private utilities were trying to win public trust as the rightful stewards of a public service. Toward that end, Philadelphia Electric executives sought to equate the technical prowess of their utility with the well-being of their service area: "The Philadelphia Electric Company's contribution to our city's prosperity is the supply of an adequate, reliable and economic power supply." The development of power plant technology in the Philadelphia Electric system reflected this search to balance reliability and economy of operation.

Construction of the Schuylkill A-l station in 1902 marked Philadelphia Electric's first major step toward a general-service central station system. The company's next two plants, Schuylkill A-2 and Chester, each reflected incremental steps in advancing the form of central station power. The A-2 station, essentially a self-contained addition to A-l built between 1914 and 1915, was the first in the Philadelphia Electric system to contain the major elements of modern power plant technology: specific design for surface condensing, horizontal-shaft steam turbines; mechanical, stoker-fired boilers; high-volume circulating water system with a screening house; and a separate switch house with a three-phase system divided functionally by floors. Over thirty years later, Vice-President in charge of engineering N.E. Funk commemorated the pioneering role of Schuylkill A-l and A-2 in a speech before a gathering of Philadelphia Electric supervisors:
Schuylkill Station is really the birthplace of virtually all of our basic operating procedure. Every one of our station superintendents learned his first lesson in the operation of the Philadelphia Electric system in the old Schuylkill Station. Methods were developed there for which the rest of the industry more or less damned us at the time. In this category is the load-dispatching system, the separate maintenance bureau, and the separate coal bureau. Our method of handling load dispatching by locating the dispatcher at Tenth Street away from the main generating station was thought to be a very silly move, but now most of the systems do it our way. The idea of taking maintenance out of the hands of the plant superintendent was thought so foolish than the president of one great company came all the way to Philadelphia to tell us what he thought about it.

Naturally, the design of Chester Station drew on lessons learned at A-2 and other stations, but it also departed from older practices in significant ways. The monumental architecture, tripartite layout facing the river, and certain standardized features implemented in the design for Chester served as a prototype for a future generation of plants that included the Delaware and Richmond stations. Several innovations introduced at Chester, including Babcock & Wilcox Stirling boilers and "island construction" in the turbine hall were also used at Delaware and Richmond.

The development of island foundations was likely a result of the increasing size of condensers and horizontal turbo-generators. A few years prior to Chester's construction, many plants placed turbo-generators parallel and adjacent to the boiler house wall, most likely to reduce the length of steam piping. In the turbine hall at Chester, the designers rotated the turbogenerators ninety degrees and built up isolated foundations for each unit, providing generous space on the lower level for access to pumps, condensers, pipes, and other auxiliary equipment. The Philadelphia Electric island foundation was well-suited to accommodating longer turbines, but width limitations precluded consideration of cross-compound turbines, a primary determining factor in the selection of turbines for Richmond Station.

At Chester, engineers also expanded their program of standardized designs, intended to reduce construction costs and provide familiar conditions for the workforce in any station. Standardizing the location of station equipment and controls, N.E. Funk explained, facilitated the transfer of men from plant to plant, reduced training time, and aided equipment maintenance.
In laying out control panels for all apparatus the instruments that are common to all stations are located in the same position on the control board wherever this is possible. This causes no inconvenience in the design, does not disturb the appearance of the board and has the advantage of giving the operator the fewest number of new instrument locations to learn... if this same policy is pursued throughout the plant control equipment, it is surprising how rapidly the operating force will fall into the operation of equipment in conjunction with the main apparatus in the plant with which they have been unfamiliar in the past.

Another precedent set at Chester was the exclusive generation of three-phase, alternating current electricity at 60 cycles and 13.2 kilovolts. Unlike the split-frequency system at Schuylkill A-2, all generators at Chester produced a standard electricity. This constituted a substantial step toward establishing uniform service in Philadelphia, as Chester's intended capacity of 120 MW nearly doubled the existing Philadelphia Electric system. The last major obstacle to standardized electricity lay in the Edison direct current district in downtown Philadelphia, a project tackled by Philadelphia Electric in 1924.

As previously mentioned, the plant layout differed in its orientation from the earlier Schuylkill stations, but was fairly typical of contemporary power plant designs and was continued in the Delaware and Richmond stations. Division of the plant into three sections; the boiler house, turbine hall, and switch house, minimized damage in the event of a fire or major equipment failure, particularly boiler explosions, which had long concerned producers of steam. Apart from erecting physical barriers between plant operations, the station workforce was also divided by the sectionalized plan: the boiler engineer and his assistant supervised a crew of water tenders, firemen, ashmen, and boiler cleaners in the boiler house; the running engineer, assistant running engineer, and oilers tended to the turbine hall; and the chief electrician, switchboard operators, excitermen, electric mechanics, and maintenance men staffed the switch house and fixed station electric motors and equipment. At least one observer expressed surprise that remarkably few workers were needed to generate so much power.

During the most useful years of production at Chester, the development of plant technology passed through several stages: original construction, 1916-1919; completion of intended capacity, 1923-1924; and World War II-era upgrade, 1939-1942. In keeping with Philadelphia Electric convention, Chester's equipment was numbered in relation to the river (in ascending order, from downriver to upriver sides of plant). The following discussion of plant technology is neither strictly chronological nor numerical. It aims instead to explain the plant's three basic functions, and is divided accordingly. In a sense, the history of Chester's technology is not one story but three. In each major section of the plant, the course of development reflected a different approach to balancing reliability against ease of maintenance, cost, and efficiency.