Commuter Rail AC Electrification Load-Flow Simulation Report - RTD

Commuter Rail AC Electrification Load-Flow Simulation Report Revision 1
3.0 TYPICAL AUTOTRANSFORMER-FED SYSTEM CONFIGURATION
3.1 GENERAL
This Section of the report discusses common features of typical modern autotransformer
systems and their application in general. More specific requirements and recommendations
applicable to Denver RTD autotransformer system are discussed in Section 9.0 – Conceptual
Design of the Denver RTD Traction Electrification System. The Traction Electrification System
(TES) will provide electrical power to the trains by means of the traction power supply system,
traction power distribution system, and traction power return system. Each system is comprised
of the following:
• Traction Power Supply System - includes traction power substations located along the
route at predetermined locations.
• Traction Power Distribution System - consists of the overhead catenary system, feeder
system, paralleling stations, switching stations, and isolating switches.
• Traction Power Return System - comprises of the running rails, impedance bonds,
cross-bonds, static wires, grounding connections, and the ground (earth) itself.
The traction power substations normally receive electrical power from the local utility company
at high voltage, 115 kV or 230 kV. The substation traction power transformers step-down the
power to 50 kV with the center point of the secondary winding grounded and connected to track
rails. Such arrangement provides two 25 kV voltages on the secondary windings suitable for
supply to the feeder/catenary system. The trains will collect their propulsion power from the
overhead catenary system by means of pantographs and return the power to the substations via
the running rails which are a part of the traction power return system.
3.2 TRACTION POWER SUPPLY SYSTEM
3.2.1 Utility Power Supply
For economic reasons, the traction power substations should receive power directly from the
power utility high voltage substations or transmission lines located in close proximity to the rail
corridors.
Connections to the utility high voltage system is required to ensure optimal supply reliability and
to limit voltage flicker, phase unbalance, and harmonic distortion that may result from the
addition of the highly fluctuating, single-phase, and non-sinusoidal traction loads.
It is desirable to supply the traction power substations by two high voltage lines that are as
independent of each other as possible.
3.2.2 Substation Type and Equipment
The traction power substations transform the utility power from high voltage of 115 kV to the AC
electrification system utilization voltage of 2x25 kV. The substations will include all the
necessary equipment in order to transform and control the AC voltage between the utility
company and the traction power system which is used by the rolling stock.
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