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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