Commuter Rail AC Electrification Load-Flow Simulation Report - RTD

Commuter Rail AC Electrification Load-Flow Simulation Report Revision 1
9.3 TRACTION POWER DISTRIBUTION SYSTEM
9.3.1 Overhead System Conductors
The traction power substations will distribute power along the system route by the
feeder/catenary system. The traction power distribution system considered in the study
consisted of the following conductors:
• Feeder Conductor, 556.5 kcmil, Aluminum Cable Steel Reinforced (ACSR) Wire
• Messenger Conductor, 4/0 A.W.G., Stranded Hard-Drawn (H. D.) Copper Wire
• Contact Conductor, 4/0 A.W.G., Grooved H. D. Copper Wire
The study demonstrated that this, or similar, configuration of the distribution system would be
suitable for electrification of the three RTD corridors as it would be capable to carry the
envisioned load currents for both normal and contingency operations, including a section of
track out of service. The conductor configuration of the overhead feeder and catenary systems
should be confirmed by the catenary system design team.
9.3.2 Paralleling and Switching Stations
The proposed distribution system will be equipped with six paralleling stations and one
switching station. Each paralleling station will include one autotransformer while the switching
station will include two autotransformers. All autotransformers will utilize a 50 kV primary
winding and 25 kV secondary winding. It is proposed that each autotransformer be rated at a
continuous rating of 2.5 MVA. The overload ratings are shown in Table 4.
The autotransformers transform the 50 kV feeder/catenary voltage to the 25 kV catenary/rail
voltage. The autotransformers will be connected to the traction power distribution system via a
medium voltage indoor switchgear line-up or outdoor circuit breakers enabling equipment
protection, emergency operation, and maintenance.
Additional simulations with autotransformers out of service in paralleling station PS-5 and PS-6
were performed to investigate the strength of the power distribution system. In both studies the
voltages were well above the study limits. Therefore, only one autotransformer is sufficient for
each of the paralleling station. Further, the locations of the paralleling stations can be changed
to suit operational requirements or real estate availability.
9.3.3 Distribution System Design and Protection
The distribution system switchgear and circuit breakers are constructed and tested in
accordance with IEEE 37 series of standards. Typically, vacuum or SF 6 types of circuit
breakers are used.
The traction power distribution system is recommended to be protected by three-zone distance
protective relays. Modern relays have completely independent and adjustable resistive and
reactive reach settings and are capable of operating with forward and backward reach. The
zone 1 typically operates in one cycle while zones 2 and 3 have adjustable time delays and train
start detection using di/dt, dv/dt, and dφ/dt functions. Other features include polygonal
characteristic, two-stage backup overcurrent protection, thermal overload protection, and a fault
locator unit capable of indicating fault distance from the relay.
02/27/2009 FRSC Page 30 of 250