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Distributed power
In rail transport, distributed power (DP) is a generic term referring to the physical distribution—at intermediate points throughout the length of a train—of separate motive power groups. Such "groups" may be single units or multiple consists,[citation needed] and are remotely controlled from the leading locomotive. The practice allows locomotives to be placed anywhere within the length of a train when standard multiple-unit (MU) operation is impossible or impractical. DP can be achieved by wireless (RF connectivity) or wired (trainlined) means. Wired systems now provided by various suppliers use the cabling already extant throughout a train equipped with electronically controlled pneumatic brakes (ECP).
Since the 1960s, railroad distributed power technology has been dominated by one company, Harris Controls (originally Harris Corporation—Controls & Composition Division, later purchased by General Electric—the division now known as GE Transportation), which has manufactured and marketed a patented radio-control system with the trade-name of Locotrol, which is the predominant wireless DP system in use around the world today.[citation needed]
With its origins in the early days of SCADA technology for the remote control of pipelines and electric utilities, and from an early concept of Southern Railway President D.W. Brosnan, Locotrol was a product of the North Electric Company (Galion, Ohio) which was later purchased by Radiation Inc. (Melbourne, Florida) and—in turn—purchased by Harris Corporation (also headquartered in Melbourne). The nascent technology was first tested on the Southern Railway in 1963, and the first production systems were installed on the Southern Railway in 1965.
The greatest benefit of distributed power—and the reason for development of the original concept—is the reduction of draw-gear draft forces, permitting a wholesale increase in the size of trains without exceeding draw-gear strength, through the use of mid- or end-of-train locomotives. There are also potential train-handling benefits. Over an undulating track profile, a skilful operator can manipulate the relative power outputs (as well as dynamic- and air-brake applications) to minimize run-in and run-out of coupler slack throughout the train.
Reduced draft forces along a train reduce the lateral force between wheel and rail on curves, thus reducing fuel consumption and wear on various running-gear components as well as the potential for a stringline derailment.
Another benefit is quicker application of air brakes. With all braking control on a conventional train being established at the head-end, it can take several seconds for brake pipe pressure changes initiated by the operator to propagate along the train. Under radio-controlled DP operation, the brakes are set at remote locomotives almost simultaneously with the command initiated on the lead locomotive, providing a more uniform air brake response throughout the train.
The main disadvantage is the operational time needed, and track configuration required, to add and remove additional locomotive units. Secondary disadvantages are the costs associated with equipping locomotives with the extra control apparatus and the potential for the intermittent loss of the telemetry signal. This latter is known as "communication interrupt" and is coped with by fail-safe software program inclusions.
Distributed power should not be confused with multiple-unit operation, which is a capability, generally found on all locomotives, that connects multiple locomotives directly together via MU cables and air brake control lines. MU operation in North America is designed so that any two locomotives so equipped, and regardless of age and manufacturer, can be coupled together and operated as a single locomotive by one operator in the cab of the lead unit. This is accomplished via a 27-pin MU cable and the connection of three additional air lines separate from the brake pipe (sometimes also called the "train line"). DP is an entirely separate arrangement to control locomotives that are physically separated from the lead unit(s) and therefore impossible to connect via multiple-uniting.
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Distributed power
In rail transport, distributed power (DP) is a generic term referring to the physical distribution—at intermediate points throughout the length of a train—of separate motive power groups. Such "groups" may be single units or multiple consists,[citation needed] and are remotely controlled from the leading locomotive. The practice allows locomotives to be placed anywhere within the length of a train when standard multiple-unit (MU) operation is impossible or impractical. DP can be achieved by wireless (RF connectivity) or wired (trainlined) means. Wired systems now provided by various suppliers use the cabling already extant throughout a train equipped with electronically controlled pneumatic brakes (ECP).
Since the 1960s, railroad distributed power technology has been dominated by one company, Harris Controls (originally Harris Corporation—Controls & Composition Division, later purchased by General Electric—the division now known as GE Transportation), which has manufactured and marketed a patented radio-control system with the trade-name of Locotrol, which is the predominant wireless DP system in use around the world today.[citation needed]
With its origins in the early days of SCADA technology for the remote control of pipelines and electric utilities, and from an early concept of Southern Railway President D.W. Brosnan, Locotrol was a product of the North Electric Company (Galion, Ohio) which was later purchased by Radiation Inc. (Melbourne, Florida) and—in turn—purchased by Harris Corporation (also headquartered in Melbourne). The nascent technology was first tested on the Southern Railway in 1963, and the first production systems were installed on the Southern Railway in 1965.
The greatest benefit of distributed power—and the reason for development of the original concept—is the reduction of draw-gear draft forces, permitting a wholesale increase in the size of trains without exceeding draw-gear strength, through the use of mid- or end-of-train locomotives. There are also potential train-handling benefits. Over an undulating track profile, a skilful operator can manipulate the relative power outputs (as well as dynamic- and air-brake applications) to minimize run-in and run-out of coupler slack throughout the train.
Reduced draft forces along a train reduce the lateral force between wheel and rail on curves, thus reducing fuel consumption and wear on various running-gear components as well as the potential for a stringline derailment.
Another benefit is quicker application of air brakes. With all braking control on a conventional train being established at the head-end, it can take several seconds for brake pipe pressure changes initiated by the operator to propagate along the train. Under radio-controlled DP operation, the brakes are set at remote locomotives almost simultaneously with the command initiated on the lead locomotive, providing a more uniform air brake response throughout the train.
The main disadvantage is the operational time needed, and track configuration required, to add and remove additional locomotive units. Secondary disadvantages are the costs associated with equipping locomotives with the extra control apparatus and the potential for the intermittent loss of the telemetry signal. This latter is known as "communication interrupt" and is coped with by fail-safe software program inclusions.
Distributed power should not be confused with multiple-unit operation, which is a capability, generally found on all locomotives, that connects multiple locomotives directly together via MU cables and air brake control lines. MU operation in North America is designed so that any two locomotives so equipped, and regardless of age and manufacturer, can be coupled together and operated as a single locomotive by one operator in the cab of the lead unit. This is accomplished via a 27-pin MU cable and the connection of three additional air lines separate from the brake pipe (sometimes also called the "train line"). DP is an entirely separate arrangement to control locomotives that are physically separated from the lead unit(s) and therefore impossible to connect via multiple-uniting.
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