Commuter Rail AC Electrification Load-Flow Simulation Report - RTD

Commuter Rail AC Electrification Load-Flow Simulation Report Revision 1
the bus-tie circuit breakers to close only when one of the buses is deenergized (the busbar
voltage is monitored by potential transformers) and the associated circuit breaker feeding the
deenergized busbar is open. The interlocking prevents the bus-tie circuit breakers to close
when both buses are energized.
10.0 CONCLUSIONS AND RECOMMENDATIONS
The load-flow simulation results show that the studied traction electrification system design of
the three Commuter Rail Corridors, East Corridor, Gold Line, and North Metro Corridor is in
compliance with the RTD Design Criteria and accepted industry practices, specifically:
• Train voltages are well above the minimum design values for normal and contingency
operations.
• Change in substation, paralleling station, and switching station locations may be made
for operational requirements and due to real estate availability. Changes in facility
locations will not materially impact the minimum system voltages.
• Substation and autotransformer ratings were selected to enable the system to operate
during normal and contingency situations.
• Catenary and feeder currents are well below the overhead feeder and catenary system
conductor thermal capabilities.
Since the autotransformer-fed system performed with a significant operational margin,
consideration should be given to the utilization of 1x25 kV direct-fed system. Preliminary results
indicate that the 1x25 kV system might be effective but more comprehensive simulations would
be required to ensure its viability. It is believed that this alternative system would be much
simpler, substantially less expensive to build and maintain, and provide more efficient utilization
of equipment.
Regardless of whether an autotransformer-fed system or direct-fed system is selected for
implementation, it is recommended that a utility impact study be performed. A key element of
the study should be investigation into the effects of the highly fluctuating traction power load on
the transmission system including a voltage flicker study. The unbalanced nature of the load
due to phase-to-phase substation transformer connections should be evaluated and the levels
of negative sequence currents in nearby generators determined. Further, the study should
evaluate the effects of harmonics on total and individual harmonic distortion of voltages and
currents and assess the likelihood of utility system resonance.
02/27/2009 FRSC Page 36 of 250