Commuter Rail AC Electrification Load-Flow Simulation Report - RTD

Commuter Rail AC Electrification Load-Flow Simulation Report Revision 1
9.0 CONCEPTUAL DESIGN OF THE DENVER RTD TRACTION
ELECTRIFICATION SYSTEM
9.1 GENERAL
Based on the traction power system study results, a conceptual design of the traction power
supply and distribution system has been developed.
For electrification of the three commuter rail lines, an autotransformer-fed system (ATF) has
been studied. The system will operate at 2x25 kV electrification voltages, single-phase, at the
commercial frequency of 60 Hz.
For the East Corridor and the Gold Line, preliminary locations of the two traction power
substations were selected in consultation with RTD, while the preliminary locations of the
paralleling stations and the switching station were developed by FRSC. The study results
enabled to confirm that the locations of substations and autotransformer paralleling stations are
suitable and to propose transformer and autotransformer ratings.
9.2 TRACTION POWER SUPPLY SYSTEM
9.2.1 Traction Power Substations
The load-flow simulations confirmed that an autotransformer-fed system, with traction power
supply system consisting of two substations, is adequate. Considering the Denver Union
Station being at milepost (MP) 0.0, the substations are proposed to be located at Sandown and
Argo:
• Traction Power Substation TPS-1, Sandown, located at approximate MP 6.0 on the East
Corridor
• Traction Power Substation TPS-2, Argo, located at approximate MP 2.0 on the Gold Line
The study confirmed that no substation is required for the North Metro Corridor. The North
Metro Corridor will be supplied by the Argo substation.
If it is possible to install two traction power transformers at both Sandown and Argo substations,
it is recommended is that each substation be equipped with two continuously-rated 12.5 MVA
single-phase traction power transformers. In the event that only one traction power transformer
can be installed in Argo substation, it is recommended that all transformers be rated at 15 MVA.
These ratings will allow for substation outage conditions, future increase in traffic density, and
for unusual operating conditions, such as train bunching. The recommended overload ratings
are shown in Table 4. The transformer primary windings will be connected phase-to-phase to
the 115 kV transmission lines owned and operated by Xcel Energy. Connections to the utility
high voltage lines are required to ensure an adequate and highly reliable power supply with low
susceptibility to phase unbalance, harmonic distortion, and voltage flicker that may result from
the addition of traction load. In order to limit the system unbalance, the transformer primary
windings should be connected to alternate phases of the 115 kV transmission system.
The transformer secondary winding will be rated at 50 kV nominal voltage and will feed the
feeder/catenary distribution system. The secondary windings will be center-tapped, with the tap
solidly grounded and connected to the traction power return system. Consequently, this
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