IEEE Power & Energy Magazine - November/December 2014 - 61

The natural gas system is generally reliable and able
to manage local and short-term pipeline disruptions without
affecting the electric power system.
gas generators start. As shown, the morning electric load
increase begins at approximately 3 a.m. The majority of daily
generator starts occur during this same time period; most of
these natural gas generators have the flexibility to cycle.
Ideally, a standard natural gas day would accommodate the
electric morning load pickup and meet the peak electric load
period in a single operating day. A closer synchronization of
the natural gas and electricity energy operating days would
facilitate the generators' purchase of natural gas to meet their
daily electricity supply.
At present, if generators buy natural gas ahead of time
to match their day-ahead electrical commitment, they are
not forced to sell any unused portion of the natural gas at
a loss. This situation will cause additional problems, however, if real-time conditions are very different from the
electric day-ahead schedule. Shifting the natural gas day
start time from 10 a.m. to no later than 4 a.m. would allow
generators to procure and schedule fuel for their entire
daily commitment.

Reliability Issues for the Natural Gas System
The electricity and natural gas infrastructures are increasingly vulnerable to outages. Power lines, substations, pipelines, processing facilities, LNG terminals, and tankers all
require physical hardening and protection against cyberattacks. The natural gas system is nevertheless generally
reliable and able to manage local and short-term pipeline
disruptions without affecting the electric power system. The
reasons are as follows:
✔✔ Since the natural gas system is underground, the probability of outages is very low.
✔✔ Many compressor stations that keep the pressure in
the pipelines at serviceable levels are powered from

Control Center

the natural gas in the pipelines themselves, allowing
for continued operation.
✔✔ Interruptible delivery contracts can be curtailed, further reducing demand. The risk of interruptions to
natural gas supply during this type of outage can be
reduced by enrolling in firm delivery contracts with
transmission companies.
✔✔ Most natural gas appliances work even when the
electricity is out. In addition, demand for natural gas
would decrease if the natural-gas-fired electricity generation were offline.
Figure 26 shows a supervisory control and data acquisition system that would monitor natural gas operations and
transmit a set of important parameters, such as natural gas
pipeline pressure and valve positions, to a control center. The
control center would use the data to locate and operate compressors, valves, switches, and pressure settings and perform
other pipeline operations for the purpose of economic operation and reliability. But because natural gas is largely delivered on a just-in-time basis, vulnerabilities in the natural gas
supply and transportation systems must be sufficiently evaluated in the planning stage to inform power system operators
about credible contingencies and flexibility options.

Final Thoughts
Until mid-2009 when, energy planners were scrambling to
find a low-cost, reliable fuel source that could replace coalfired electricity generation. Before then, energy planners and
investors still saw coal plants, which accounted for much
of power generation and industrial CO2 emissions, as a safe
choice for additional generating plants, even with the decreasing levelized cost of renewables. This was due to coal's low
price and stable supply in many parts of the world. Since 2009,

Communication Network

figure 26. A natural gas control system (source: Congressional Research Service).
november/december 2014

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