Many factors influence the selection of
the proper type of substation for a given application. This selection
depends on such factors as voltage level, load capacity,
environmental considerations, site space limitations, and
transmission-line right-of-way requirements.
While also considering the cost of
equipment, labor, and land, every effort must be made to select a
substation type that will satisfy all requirements at minimum costs.
The major substation costs are reflected in the number of power
transformers, circuit breakers, and disconnecting switches and their
associated structures and foundations.
Therefore, the bus layout and switching
arrangement selected will determine the number of the devices that
are required and in turn the overall cost. The choice of insulation
levels and coordination practices also affects cost, especially at
EHV. A drop of one level in basic insulation level (BIL) can reduce
the cost of major electrical equipment by thousands of dollars.
A careful analysis of alternative
switching schemes is essential and can result in considerable savings
by choosing the minimum equipment necessary to satisfy system
requirements. A number of factors must be considered in the selection
of bus layouts and switching arrangements for a substation to meet
system and station requirements.
A substation must be safe, reliable,
economical, and as simple in design as possible. The design also
should provide for further expansion, flexibility of operation, and
low maintenance costs. The physical orientation of the
transmission-line routes often dictates the substation’s location,
orientation, and bus arrangement. This requires that the selected
site allow for a convenient arrangement of the lines to be
accomplished.
For reliability, the substation design
should reduce the probability of a total substation outage caused by
faults or equipment failure and should permit rapid restoration of
service after a fault or failure occurs. The layout also should
consider how future additions and extensions can be accomplished
without interrupting service.
Traditional and Innovative
Substation Design
Traditionally, high-voltage substations
are engineered based on established layouts and concepts and
conservative requirements. This approach can restrict the degree of
freedom in introducing new solutions.
The most that can be achieved with this
approach is the incorporation of new primary and secondary technology
in preengineered standards. A more innovative approach is one that
takes into account functional requirements such as system and
customer requirements and develops alternative design solutions.
System requirements include elements of
rated voltage, rated frequency, system configuration present and
future, connected loads, lines, generation, voltage tolerances (over
and under), thermal limits, short-circuit levels, frequency tolerance
(over and under), stability limits, critical fault clearing time,
system expansion, and interconnection.
Customer requirements include
environmental consideration (climatic, noise, aesthetic, spills,
right-of way), space consideration, power quality, reliability,
availability, national and international applicable standards,
network security, expandability, and maintainability. Carefully
selected design criteria could be developed to reflect the company
philosophy.
This would enable consideration and
incorporation of elements such as life-cycle cost, environmental
impact, initial capital investment, etc. into the design process.
Design solutions could then be evaluated based on established
evaluation criteria that satisfy the company interests and policies.
No comments:
Post a Comment