Thesis Abstract and Dissertation Abstracts

Abstract Category: Engineering
Course / Degree: Ph.D
Institution / University: Delhi College of Engineering, Delhi, India
Published in: 2008

Thesis Abstract / Summary:

Electrical power is one of the most important infrastructure inputs necessary for the rapid socio-economic developments of a country. Currently it constitutes about 20% of the total annual energy consumption on a worldwide scale with an ever-rising demand. This increase in demand has led to the installation and incorporation of a large number of electric power generation units with increased capacities in a common power grid, making the operation of the entire system sensitive to the prevailing conditions. Therefore, the extensive and complex power systems have become unmanageable using the conventional instrumentation and control schemes. Intelligent system based on microprocessors and computers, Supervisory Control and Data Acquisition (SCADA) system, have been employed for online monitoring and control of modern large-scale power systems, thereby overcome the complexities and drawbacks of the conventional instrumentation schemes, in generation, transmission and distribution.

SCADA systems have now become an integral part of power system operations. It communicates with the operator on real time basis about the health of the power system and analyzes the performance. The SCADA system is a real time on-line monitoring and control system, which provides coordinated operations for selected functions.

After a literature survey keeping in view the thrust areas, it is observed that the existing SCADA system for power system poses several limitations. The limitations can be overcome by building intelligence at every level of the design and by reducing the human involvement to decrease the risk of errors and mal operations in the power system. It was desired to design and test the intelligent SCADA system, which minimizes the limitations of the conventional methods for supervision and control.

As the large amount of data is handled by the main component of SCADA i.e. remote terminal unit (RTU), whose principle function is to capture the data, process it and communicate it to higher hierarchy or to display, it is required that the RTU components are reliable enough to handle any emergency. An effective and reliable design of the RTU is required to handle large amount of data and to take corrective action when needed. The operator, sitting in the control centre, supervises the health of the power system, and also analyzes data gathered.  The design of a human-friendly control centre is the key to enhancing the efficiency of the operator. The data captured by the RTU has a certain amount of uncertainties and errors, which require pre-processing of the data. Fuzzy logic method is one of the alternatives for improving the quality and reliability of such data before processing it further. As the knowledge base degrades, the response of processing with fuzzy logic algorithm is also reduced. This requires tuning of the fuzzy function. Traditionally, the tuning of fuzzy function is done manually. However, this is a time consuming process and can result in a local solution only. This difficulty of the fuzzy logic algorithm has been overcome by integrating genetic algorithm with fuzzy function.

Thus, the main contributions of the thesis are:

1. Design of SCADA system based on Transputer and Field Programmable Gate Array (FPGA).

2. Design and testing of RTU.

3. Design of human friendly central control centre.

4. Fuzzy logic technique for pre-processing data at RTU.

5. Fuzzy Genetic algorithm for pre-processing data at RTU.

An integrated power system has a large amount of data, to be acquired, processed and presented to the operator and system engineer for effective operation of the power grid. These functions can be handled very effectively using a distributed processing system. It provides a powerful tool to the engineer and operator for immediate access to large amount of current information from the data highway, and can see & display the past processed conditions by calling archived data. These microprocessor based SCADA systems are sequential and does not fulfill the requirements of parallel processing. Thus the proposed SCADA system has been designed using Transputer (con-current processing) and FPGA systems.The FPGA based SCADA system is an excellent means for providing the process control facilities and it has the greatest logic capabilities, enormous processing resources, high clock speed and negligible delay. It provides the facility of on-off control, and presentation of data only higher hierarchy. This approach suits to the processes, which are otherwise very slow. For the processes where the speed of scanning and control is the important task, Transputer based SCADA systems will be required. This is a parallel processor based system and requires con-current  (parallel) programming.  The different variables are assigned to different parameters in order to avoid the dependency. Thus maximum utilization of the processor is possible for processing. These systems overcome the limitations of the FPGA based SCADA and the sequential based SCADA systems.

 

The Remote Terminal Unit (RTU), main component of SCADA system, acquires all the field data from different field devices, processes it and transmits the relevant data to the master station. At the same time it distributes the control signal received from the master station to the field devices. A large number of equipments viz. transformers, feeders, energy meters etc. are connected at remote locations, and they require are to be monitored at short intervals of time. Because of this wide spread locations, with consumers switching from one state to another (on / off) very frequently, the possibility of faults increases. To overcome the limitations of the conventional methods of supervision and control, it was desired to install an Intelligent Monitoring Instrument having upward communication facilities. The success of a SCADA project primarily depends upon the proper design of the RTU, which captures the data through appropriate sensors, transducers and communicates to higher hierarchy through the communication channel. Selection of the processor, database structure, communication buses, field buses, etc. plays a vital role in design and configuration of the RTU for meeting the desired functional requirement. The reliability testing of the RTU was done, which shows that the introduction of redundant processors increases the reliability of the RTU by 30% (app.). The hardware testing of the RTU was done using Petri Net technique, which is used to write the software program for the entire control operation of the system. 

The Control centre is the place which provides the facility to the operator / system engineer to monitor the health of the power system viz. generation, transmission, and distribution systems, and issue the necessary instructions to the operator at substation / power stations to ensure that the power system shall remain in optimum stable state. This needs the Computer system / server, Telemetry system, and communication system for online real time continuous monitoring and control of the system. These systems have to be housed in an appropriately suitable environment to meet the fault tolerance and ensure reliable operation. The design of the operator console should also ensure easy functioning of the operator in all situations without undue stress in any part of the body. Broadly, the housing rooms for the systems and various equipments are control room / operator console, server room / computer hardware, training and development room, conference hall, auxiliary facility room viz. entertainment room, exercise room, refreshment room, rest room and changing room, UPS and battery room, and miscellaneous rooms.

The control centre and the individual facility room were designed to meet the functional requirements, with control of temperature, humidity and illumination. The control centre and other housing rooms and facilities was designed considering the factors such as the view angle of the operator (which is initially required in deciding the dimensions of the control room), height of the visual display unit (VDU), (which displays the variables to be monitored and the mimic diagram with the help of separate panel mounted CPU in windows environment) and the dimensions of the average human operator, (which decides the parameters of the engineer and the operator console, the auxiliary rooms in the control centre etc). Based on the above-mentioned parameters, height, width and the spacing between the consoles were designed, which decides the dimensions of the control room and the other auxiliary rooms. The ergonomics was applied for design of seat of operator in control centre, distance of the operator from the mimic board and the VDU, height, width and depth of the operator room and other facility rooms and illumination and the power requirement of the control centre was computed. The sensitivity study of illumination with respect to the view angle of operator has also been computed and presented in the thesis.

The proposed design is based upon the functional requirements of the control centre and the facility required. The authors have considered the following parameters viz. analysis of voltage, MW flow, frequency, tie line interconnection, the economic load flow, and the mimic diagram (which gives the online information of the interconnected areas / grid) in deciding the size of the VDU. The typical view of angle of 8o- 20o (typically 15o) has been considered, which decides the dimensions of the control room viz. height, width and the length. The sensitivity of the control room parameters are thus calculated with respect to the view angle and the results show that change in the view angle (from 15o to 18o), will affect the dimensions (width and length) of the control room by 6.8%, and change the illumination requirement by 13.6%. Similarly, the change in the average dimensions of the operator by 4.35% will affect the height of the control room by 0.91% and the designed consoles dimensions by 10%. Thus a little change in the dimensions of the average operator and view angle (dimension of the VDU) will have the effect on the overall design and the facilities required in the control room.

The main component of the SCADA is RTU, whose principle function is to capture the data from the power system, process them and communicate them to higher hierarchy or to display the data to the operator. The data captured by the transducers in the field are conditioned and converted to digital data and used in RTU for onward transmission to higher hierarchy and for display. The data captured by the RTU has certain amount of uncertainties and errors. To take care of these uncertainties and errors present in the data, pre-processing of data is necessary. Fuzzy logic method is one of the alternatives for improving the quality of such data before processing it further, and it also improves the reliability of measurement.

Fuzzy logic is a convenient method of processing information with uncertainties. It is basically a rule-based algorithm, which can handle noisy and non-linear systems. With fuzzy logic it is possible to construct a solution where no model is available. However, a good qualitative understanding of the system is required in order to understand the reliable fuzzy logic algorithm. Fuzzy logic processing is an expert processing system, which uses the set of rules framed by experts.

Table-1 shows the comparison of percentage of the measurand (M), fuzzy pre-processed (FP) and estimated values (E) for voltage, current and the power factor

 

VOLTAGE	Counts	M	FP	E
	20000	98.0392	106.8875	102.4634
	22000	98.522	95.692	97.1068
	24200	99.01	99.013	99.012
	26000	98.522	99.604	99.063
	27500	98.039	93.239	95.639
CURRENT	7000	98.039	109.574	103.807
	9000	98.522	144.101	121.302
	14000	99.01	105.728	102.369
	19000	98.522	108.893	103.708
	22000	98.039	89.913	93.976
POWER-FACTOR	27000	99.01	99.01	99.01
	27500	98.761	101.271	100.016
	28000	98.522	99.103	98.812
	28200	98.28	99.99	99.064
	29000	98.039	96.204	97.122

The measurand is transformed to a set of possible true values, which are processed according to these rules and an attempt is made to estimate the true value of the measurand. Using this fuzzy logic (intelligent) technique / algorithm, fuzzification of counts with percentage of voltage, current and power factor has been done. It is noted that as measured (voltage, current, and power factor) moves away from the nominal value, the error in the measurand is increased considerably and it is appropriate to use the fuzzy logic technique before data is presented to the operator.

It is noted that the estimated values are near to fuzzy pre-processing values and far away from measured values. This deviation is more when the measurand values are far away from nominal values of the parameter. Also it is observed that the errors are present in the data, which are to be either removed or taken care of before processing and presenting.

As the knowledge base degrades, the response of processing with fuzzy logic algorithm is reduced. This requires tuning of the fuzzy functions as shown in fig.1.

Table-2 shows the Comparison of results for Measured (M), Fuzzy pre-processed (F) and Estimated value (E) for the new universe of discourse

Thesis Keywords/Search Tags:
SCADA, soft computing, RTU, control centre

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Submission Details: Thesis Abstract submitted by Dr. Vinay Chandna from India on 11-Oct-2011 12:56.
Abstract has been viewed 4333 times (since 7 Mar 2010).

Dr. Vinay Chandna Contact Details: Email: vinaychandna@yahoo.co.in Phone: +91-9891406784

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