Present-Day Power Distribution Infrastructure - Compaq 226824-001 - ProLiant - ML750 Basics Manual

coordinating committees or organizations. The data center administrator can research the history of
service availability from the local utility or the grid manager. Planning for temporary power
generation and for using uninterruptible power supplies (UPSs) to back up the electric power system
can eliminate interruptions due to distance or weather conditions.
Figure 3 shows a typical electric power infrastructure for the generation, transmission, and distribution
of electric power. Throughout the transmission process, the power passes through several voltage
levels. The power station's three-phase generator passes current through a step-up transformer. From
the step-up transformer it passes onto the grid at a transmission voltage level. The electric power is
transmitted over transmission lines to a step-down transformer that produces a distribution-level
voltage. The distribution voltage continues over pole lines or distribution lines to small industrial,
commercial, and residential customers.
Figure 3. Simplified representation of electric generation, transmission and distribution infrastructure

Present-day power distribution infrastructure

The North American power grid includes approximately 158,000 miles of high-voltage transmission
wires. It is a vast, self-governed grid of ad hoc standards, highly compartmentalized yet broadly
interconnected and with fault tolerance and recovery built into the system to as great a degree as
possible.
In the United States, the transmission grid is made up of three national networks (the Eastern,
Western, and Texas Interconnects) and ten regional grids (plus Alaska, with connections to Canada
and Mexico). No matter what its origin or method of generation—whether it comes from a dam, a
nuclear facility, or the closest river, coal or gas-fired electric plant—power is first transmitted in large
blocks or megawatts over relatively long distances across the North American power infrastructure. It
goes from one central generating station to another or from a central station to main substations close
to major load centers. In the United States, the transmission grid switches these power blocks between
the national networks, regional grids, and individual utilities at extra high and high voltage to
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