About
Electric
substations are facilities in charge of the voltage transformation to provide
safe and effective energy to the consumers. This energy supply has to be
carried out with sufficient quality and should guarantee the equipment
security. The associated cost to ensure
quality and security during the supply in substations is high.
Even when all the magnitudes to be controlled
cannot be included in the analysis
(mostly due to the great number of measurements and status variables of
the substation and, therefore, to the rules that would be required by the
controller), it is possible to control the desired status while supervising
some important magnitudes as the voltage, power factor, and harmonic
distortion, as well as the present status.
Experimental Results
To
carry out the experiment, a software for the platform windows 9x/2000 using
Delphi was elaborated. Signal generators for the analog input variables were
used. The experiment was starting from
the status 0011. During the first 400 measurments,243 actions could not be
determined by the controller ,an expert gave the answers i.e., ,and as a
result,243 new controller rules were extracted.
Plant Description
The system under study
represents a test substation with two 30KVA three-phase transformers, two CBs,
two switches, three current transformers, and two potential transformers. It also contains an auto transformer (to regulate the input voltage) as well as
impedance to simulate the existence of a transmission line. The input voltage are the same (220V), this characteristic was selected in
order to analyze the operation of the controller in a laboratory scale in a
second stage of the development of the present work. Therefore, the first
transformer increases the voltage to a value of 13.2KV, while the second lowers
it again to 220V. fixed filter, an automatic filter for the control of the
power factor and the regulation of the voltage, and three feeding lines with
diverse type of loads of different nature
(including nonlinear loads) are connected through CBs to the output
bar.
Inference Module
The controller
outputs are decided
by searching in
the rule base.
In this step,
called inference, the
fire degree of
each rule is
calculated. Since the
consequence part in
each rule only
deals with status
variables whose values
are crisp numbers(0
and 1), use
of defuzzification method
is not necessary. Therefore, the
controller output in
each case will
be the consequent
part of the
rule with the
biggest fire degree.
Abstract
Controlling
a substation by a fuzzy controller speeds up response time diminishes up the
possibility of risks normally related to human operations. The automation of
electric substation is an area under constant development Our research has
focused on, the Selection of the magnitude to be controlled, Definition and
implementation of the
soft techniques, Elaboration of
a programming tool
to execute the
control operations. it is
possible to control the desired status while supervising some important
magnitudes as the voltage, power factor, and harmonic distortion, as well as
the present status. The status of the circuit breakers can be control by using
a knowledge base that relates some of the operation magnitudes, mixing status
variables with time variables and fuzzy sets .
Conclusion
Electric
substations are facilities in charge of the voltage transformation to provide
safe and effective energy to the consumers. This energy supply has to be
carried out with sufficient quality and should guarantee the equipment
security. The associated cost to ensure quality and security during the supply
in substations is high. Automatic mechanisms are generally used in greater or
lesser scale, although they mostly operate according to an individual control
and protection logic related with the equipment itself.
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