Protection of the Inter-Tie between an Industrial Cogenerator and a Utility

This thesis is submitted in partial fulfilment of the requirements of the Council for National Academic Awards for the degree of Doctor of Philosophy in Electronic and Electrical Engineering, November 1990.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 173-180).The work presented in this thesis is concerned with the development of a microprocessor based technique to detect and locate symmetrical and unsymmetrical faults on the interfacing network of a utility interconnected industrial cogenerator system; and to identify the type of the detected fault. In order to provide operational flexibility and supply security to such an interconnected industrial cogenerator plant, fault location is regarded as being of prime importance. Current protection practices using conventional technology for this sort of interconnected cogeneration system were reviewed. A relay coordination study was carried out on a simulated utility interconnected cogeneration system. This resulted in identification of the problems and limitations of the application of standard IDMT relays for overcurrent protection of such a system. A review of digital protection, and its various algorithms, was undertaken. This provided the basis for a rational choice of algorithm for the proposed new technique. The sequence of functions of the protection scheme's algorithm, based on the proposed technique, can be presented in brief as follows: First, phase currents at selected positions on the system are sampled. The positive phase sequence (pps) currents at those positions are then obtained in digitised form from the sampled phase currents. Then, these pps currents, containing fundamentals along with other harmonics and dc offsets, are used in a Fourier filtering algorithm to extract only fundamental components in rectangular forms. Signs of imaginary parts of these components are then used to determine the directions of pps currents at the selected positions. The industrial bus voltage is used as the polarising reference. Finally these directions are based in a fault detection aridlocat1on subroutine to determine the location of any fault under such conditions. After detecting a fault and locating its position, the type of fault is determined from off-line analysis of the postfault phase currents. The analysis is based on identifying the phases carrying the maximum fault current and checking the presence of zero sequence current. The proposed protection scheme has been tested on a computer simulated system which consists of a utility interconnected to an industrial plant with cogeneration. The performance has been found to be satisfactory for all kinds of solid and low are resistance faults anywhere on the interfacing network between the systems.Abdur Rahim MollahDoctor of Philosophy in Electronic and Electrical Engineerin

Some Studies on Heat Transfer in Circulating Fluidized Beds

This thesis is submitted to the Department of Mechanical Engineering, Indian Institute of Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering, December 1990.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 381-398).Experimental investigations were made to study the effect of fin and vertical probe height on hydrodynamics and heat transfer in circulating fluidized beds (CFB). The experiments were conducted in a 100 mm I.D., 5.15 m tall CFB unit. Air was supplied by a high pressure centrifugal blower. The distributor plate used was straight hole onfice type having 12.4% open area. The test section was located at 2.75 in above the distributor and electric tape heater was used as the source of heat. The temperatures of the inside wall and the bed at about the midpoint in the test section were measured with copper constantan thermocouples. Five plain and five finned test sections have been examined, three of which had rectangular fins and two had pin fins. Local sand of mean diameter 310 μm was used as the bed material. Measurements covered a range of superficial air velocity from 5.6 to 12.5 m/s, suspension density from 18 to 76 kg/m3 and bed temperature from 330 to 365 K. Three bed inventories of 20, 26 and 32 kg and five heat fluxes in the range of 3580 to 7876 W/m2 were used. One empirical model was developed with the help of dimensional analysis to predict heat transfer in a hot CFB to bare tube surfaces. One analytical model has been developed for the prediction of heat transfer to finned surfaces in a CFB both for long and short fins. An empirical equation has been developed correlating the parameters Nup, Rep and Lh/D to estimate heat transfer from the probes of different vertical heights. In addition one expression for calculating particle residence time has also been derived. The results predicted from the models and correlations have been compared with the present experimental results as well as those of other investigators and good agreement is observed. With the use of fins, the heat transfer coefficient was found to decrease by a maximum of 32% but the total heat transfer got enhanced by about 103% due to the additional surface area provided by the fins. Heat transfer coefficient was found to decrease and particle residence time was found to increase with the increase of vertical height of the probe.Md. Nawsher Ali MoralDoctor of Philosophy in Engineerin

Study of the yaw stability of a downwind horizontal axis wind turbine

This thesis is submitted to the Department of Mechanical Engineering, Bangladesh University of Engineering & Technology, Dhaka in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering, January 1990.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 97-101).Present thesis discuss a method to calculate the overall design, performance and structural analysis of a horizontal axis wind turbine. For a particular wind velocity, the optimum rotor configuration for twist and chord is determined using the momentum theory and the blade element theory, assuming zero drag,no coning and no tilting angle. After determining the optimal aerodynamic shape of the blade, the forces and moments on blades and tower top are calculated. At this stage, the equations may be extended to include the effects of coning and tilting angles, and the effect of several wind conditions such as wind gradient, wind shift and tower shadow. In this thesis, effects of coning and tilting angles are not considered. But the analysis of stability by determining the forces and moments acting on a horizontal axis wind turbine when yawed to non-axial flow is presented. The effect of tower blockage on the stability at various yaw angle is also considered. Three types of blade shape such as, Optimum-chord Optimum-twist, Linear-chord Linear-twist and Linear-chord Zero-twist are considered.Khandkar Aftab HossainMaster of Science in Mechanical Engineerin

Study of Mechanical Behaviour of Jute Fibre Reinforced Plastics

This thesis is submitted to the Department of Mechanical Engineering, Bangladesh University of Engineering and Technology in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering, September 1986.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 45-47).Some strength characteristics of jute fibres, yarns, fibre bundles, yarn bundles, mats, and jute mat reinforced plastics, have been determined. The hardness, fatigue life, flexural modulus and percentage increase in weight due to immersion in water of jute mat reinforced plastics have also been investigated. The mean experimental value of strength of jute fibre bundle correlates well with that obtained theoretically on the basis of Daniels' theory. It was observed that the mean experimental value of strength of jute fibre decreased with the increase of the gage length. There is a reduction of about 40% in strength when the gage length changes from 1 cm to 10 cm. The mean experimental values of strength of jute fibre for three different gage lengths (10 cm, cm,i cm) correlated well with that obtained theoretically on the basis of Coleman's theory. The mean experimental value of strength of jute mat was found to be about 1 times greater than the mean experimental value of strength of jute yarn bundle. It was Observed that the mean exPerimental values of strength and Young's modulus of jute mat reinforced plastics increased with the increase of volume fraction of jute in the composite. But the experimental Young's modulus values of Jute reim'orcea PaSt1CS Were found to he about 11/2 times greater than the theoretically calculated values on the basis of Netting-type analysis. It was also observed that the mean experimental values of flexural modulus, fatigue life, hardness, and Dercentare increase in weight due to immersion in water, of jute mat reinforced plastics increased almost linearly with the increase of volume fraction of jute in the composite.K. A. KazimMaster of Science in Mechanical Engineerin

On MHD Flows of Viscous Incompressible Fluids

This thesis is submitted to the Department of Mathematics, Faculty of Science, Banaras Hindu University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mathematics, August 1986.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 167-170).The presented thesis entitled “ON MHD FLOWS OF VISCOUS INCOMPRESSIBLE FLUIDS” is being presented for the award of the degree of Doctor of Philosophy in Mathematics. It is the outcome of my researches conducted in the Department of Mathematics, Banaras Hindu University during the years 1983-86 under the esteemed guidance of Dr. Newal Kishore, Reader in the Department of Mathematics, Banaras Hindu University, Varanasi, India. The whole thesis consists of six chapters. The first chapter is introductory, giving the general description and fundamental equations of magnetohydrodynamics, free conviction flow, flow through porous media, rotating fluid flow, oscillatory flow and flow with Hall currents. Lastly a brief review of the past researchers related to the thesis have been given. Throughout the work we are considering the flows of electrically conducting viscous and incompressible fluids. The magnetic Reynolds number is assumed small for all the problems except the problems discussed in chapter two. The second chapter has been divided into parts. Part A of this chapter deals with the flow between two infinite, non-conducting, parallel porous flat: plates, when the lower plate is injecting fluid and the upper one is absorbing it. The flow is subjected to a uniform transverse magnetic field and the magnetic Reynolds number of the flow is sufficiently large so as to include the effect of induced magnetic field. The expressions for the velocity and induced magnetic fields have been obtained by using Laplace transform technique. The effect of the magnetic parameter on the velocity and induced rnagnetic field has been studied. It is found that the velocity decreases with increase in M in the lower region between the plates and increases with increase in M in the upper region. The induced magnetic field decreases with increase in M. In part B of this chapter, the effect of uniform transverse magnetic field on unsteady MHD free convictive flow past an impulsively started infinite vertical non-conducting plate has been discussed. Here also, the magnetic Reynolds number is assumed to be sufficiently large to take account of the induced magnetic field. There is constant heat flux at the plate. Expressions for the velocity and induced magnetic have been obtained by Laplace transform technique. The effect of the different parameters on the flow have been discussed with the help of tables. In part A of the third chapter, the effect of a uniform transverse magnetic field on the steady free convective flow through a porous medium, occupying a semi-infinite region of space and bounded by a steadily moving vertical porous plate has been studied. The flow is subjected to constant suction. Approximate solutions to the equations relevant to the problem have been obtained. The influence of the different parameters on the velocity and temperature fields have been discussed with the help of graphs and tables. The problem considered in part 3 of this chapter is an extension of the problem considered in part A. Here we have taken into account the effect of rotation on the flow. Due to rotation the flow become three dimensional. Approximate solutions to equations relevant to the problem have been obtained. Effects of the various parameters on the primary velocity, secondary velocity, the components of skin friction and the temperature have been discussed. The fourth chapter is concerned with the unsteady free convective flow past on impulsively started infinite vertical porous plate in presence of a uniform transverse magnetic field. The free stream is assumed to oscillate in time about a constant mean. The flow is subjected to content suction velocity and there is constant heat flux at the plate. Approximate solutions for the mean flow and transient flow have been obtained and the results have been discussed with the help of tables and graphs. In the fifth chapter we have studied the effects of flail currents on the unsteady MHD free convective flow past an impulsively started infinite vertical porous plate in presence of a uniform transverse magnetic field. The p1ate temperature is assumed to oscillate in time about a constant mean and the flow is subjected to constant suction at the plate. Approximate solutions for the mean flow and transient flow have been obtained. The inf1uence of the various parameters on the mean and transient flows has been discussed with the help of tables and graphs. In the last chapter, an attempt has been made to study the effects of rotation and Hall currents on the unsteady MHD free convective flow through porous medium occupying a semi-infinite region of space and counted by an infinite vertical porous plate in presence of a transversely applied uniform magnetic field. The plate is assumed to oscillate in time about a constant mean and there is constant heat flux at the plate. Approximate solutions for the mean flow and transient flow have been obtained and the results have been discussed with the help of graphs and tables.Fouzia RahmanDoctor of Philosophy in Mathematic