... issues that today's transmission
providers, operators, planners, designers, users and regulators
must address. Reliability is the measure of the network's
ability to transfer power from point/s of delivery to point/s of
receipt. This could be a system-wide figure such as system minutes,
or the impact and probability of occurrence of the worst single
contingency. Or it could be customer-specific, such as the expected
unserved energy for an industrial plant. For the most part, reliability
is measured technically and does not become real or tangible until
the impact cost of unreliability is determined. Hence, Cost
is an important issue. What is the damage cost of unserved energy?
What is the cost of overloads and voltage criteria violations? Finally,
there is clear a tradeoff between improving reliability and minimizing
costs. So Risk is an issue, as one weighs between reinforcing
the system or accepting an existing level of unreliability. Risk
is an important aspect of the decision-making process for transmission
systems. It becomes even more important as industry structures move
to deregulated generation markets.
Reliability is …
… a network’s ability to
deliver power from generation to load within the operating limits
of equipment, and without loss of continuity of supply or widespread
failure. To users and customers of transmission networks, reliability
is an expectation of service; for example, that light will
come forth when the switch is flicked. Providing this service is
very much like attempting to steady a boat in bouncy seas --- boundary
conditions keep changing: loads increase and diminish, generators
go on and off line, equipment fail or require maintenance ... now
and then a storm happens by.
The most common method of providing
for reliability is the so-called (n-1) criterion. The criterion
says that a system is sufficiently reliable if it is able to operate
acceptably under any unplanned outage of equipment due to a single
cause.
