American Audio VELOCITY - REV 4-05 Betriebsanleitung PDF herunterladen (Seite 144)

METRO RAIL DESIGN CRITERIA SECTION 9 / SYSTEMS

DE304.09 9-139 Revision 4 : 05/09/12

Metro Baseline Re-Baseline: 04/29/10

High Voltage Switchgears shall receive power from the Utility Incoming

Switchgear and distribute it to the individual Transformer-Rectifiers and, when

applicable, to the various Auxiliary Transformers of the Stations. The 34.5 kV

circuit breakers shall consist of SF6 insulated assemblies. Lower voltages circuit

breakers may be of conventional vacuum type.

D. Transformer-Rectifier Units

1. Rectifier transformers shall be indoors, ventilated, dry-type, self-cooled,

class AA, configured as required to power the rectifier units further

described. The 34.5kV transformers shall be of cast coil construction. The

lower voltage transformers may be conventional dry-type or cast-coil.

2. Rectifier Units shall be solid state diode, indoors, air cooled, and self-

ventilated, configured for 12-phase operation (ANSI Circuit 31). Thyristors

can be used in lieu of diodes, if technically and economically feasible and

advantageous, with Metro approval. Each individual diode shall be provided

with individual fuse protection. The rectifier shall maintain all its performance

requirements even with one diode out of service per rectification leg.

3. Each Transformer-Rectifier Unit shall provide the following overload

capacities:

a. 150% continuous overload for two hours, following continuous operation

at 100% load with stabilized temperature.

b. 300% overload for five one-minute cycles equally spaced within the two

hour overload period.

c. 450% overload for 15 seconds at the end of the two hour overload

period.

4. Internal regulation shall be specified on a line specific base, from 4.5% to

6%, but shall be uniform throughout the same line.

5. All wiring inside rectifier cabinet associate with snubber circuits and diode

fuses, shall not touch the diode heat sinks and the wire shall be rated for

2kV insulation.

E. DC Feeder Switchgear

1. DC Switchgears shall include all the feeder breakers to be connected to

each individual section of the Third Rail and/or OCS.

2. DC Switchgears shall also contain isolation means from the Rectifier Units,

consisting of one positive breaker and one negative no-load switch,

mechanically interlocked to prevent in any circumstances a configuration in

which the positive cathode breaker is closed or being closed while the

negative switch is open or being opened.

3. DC feeder circuit-breakers shall be single pole, extra high speed, including

an internal mechanical over-current device, and with sufficient short-circuit

capacity to interrupt the maximum short-circuit that may occur in the system.

F. System Protection

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