The switches of the
direct current circuits are hand-operated and are located upon boards
at the right and left of the control board.
A novel and important feature introduced (it is believed for the first
time) in these sub-stations, is the location in separate brick
compartments of the automatic circuit breakers in the direct current
feeder circuits. These circuit breaker compartments are shown in the
photograph on page 93, and are in a line facing the boards which
carry the direct feeder switches, each circuit breaker being located
in a compartment directly opposite the panel which carries the switch
belonging to the corresponding circuit. This plan will effectually
prevent damage to other parts of the switchboard equipment when
circuit-breakers open automatically under conditions of short-circuit.
It also tends to eliminate risk to the operator, and, therefore, to
increase his confidence and accuracy in manipulating the hand-operated
switches.
[Illustration: ASSEMBLY OF CONTACT RAIL AND PROTECTION]
The three conductor cables which convey tri-phase currents from the
power house are carried through tile ducts from the manholes located
in the street directly in front of each sub-station to the back of the
station where the end of the cable is connected directly beneath its
oil switch. The three conductors, now well separated, extend
vertically to the fixed terminals of the switch. In each sub-station
but one set of high-potential alternating current bus bars is
installed and between each incoming cable and these bus bars is
connected an oil switch.
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