Kourosh Takami - Academia.edu (original) (raw)

Papers by Kourosh Takami

Kanthal AB, the market's foremost supplier of heating solutions to industry, often creates op... more Kanthal AB, the market's foremost supplier of heating solutions to industry, often creates optimum solutions for each customer. One of their solutions is the High Power Reflector, which consists of a vacuum formed ceramic fibre 'hood' with an integrated Kanthal Super ceramic heating element. The performed project is to optimize heat performance of the High Power Reflector with respect to output power and temperature distribution. The task was solved using heat transfer simulations in with reflector different models. The simulation in COMSOL software environment in two-dimensional was performed to find the best reflector shape. Authors have simulated five different types of proposed reflectors. The temperature distributions were simulated as well as temperature profile and curve in 20 cm on the top of element until 50 cm have obtained, in this way with respect to higher out power and uniform temperature distribution, was found the optimized model of reflector and hood for...

Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs sh...

Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs sh...

Hotspottemperature (HST)isthemostimportant parameter intheoperation ofpower transformers. TheHSTh... more Hotspottemperature (HST)isthemostimportant parameter intheoperation ofpower transformers. TheHSThasto beheldunderaprescribed limit. HSThasaconsiderable effect ontheinsulation aging. Therefore detecting, monitoring andremoving theHST couldbea very important andnecessary action forUtilities. A newdesign ofoil spraying anditseffect, alongwithathermal management ina transformer cooling system hasbeenstudied inthis paper. The effect ofoilfluidflow ontheHSTproblem hasbeenconsidered in thispaper;andthecalculations andsimulation havebeen performed byAntsalgorithm. Thesimulation results havebeen validated basedona230/63/20 kV,250MVAtransformer atthe Sarisubstation inIran,andtheresults indicate thatthenew design could mitigate thelimitations oftransformer loading dueto theHSTproblem. TheAntsalgorithm havebeenproposed and appliedfor accomplishing this taskandtogiveanimproved level ofaccuracy.

In medium voltage high MVA Turbo-generators, generally Roebel bars are used in slot area. To redu... more In medium voltage high MVA Turbo-generators, generally Roebel bars are used in slot area. To reduce the circulating current in slot area of Turbo-generators, transposed Roebel bars are located in slots. Because of that large turbo-generators trend to offer a top power density, winding strands being as a Roebel transposition form and strands are insulated against each other. Optimized structure of the Roebel bar can remove the circulating currents which have been generated in the stator windings. The structure of the bar causes an increase in volume of copper used in strands of windings. With increasing the copper volume and length of strands, the rugged magnetic field increases in the slot area. Because of this reason, eddy current losses grow in solid winding strands. Thus there must be a balance between eddy current losses and circulating current losses in Turbogenerators. The optimal transposition way based on a finite analysis model is used to create this balance so to optimize ...

Transformers are more complex devices, consisting of an iron core around which are wrapped variou... more Transformers are more complex devices, consisting of an iron core around which are wrapped various coils of insulated wires, inside a tank filled with insulating oil, along with connectors, bushings and various other small components. Overloading causes excess heat in a transformer, the negative effects of which are degradation of the kraft paper insulation around the wires (leading to internal failures of the coils), excessive tank pressure or degradation of the insulating oil (either of which can cause catastrophic failures, even explosions), and leaking gaskets and seals. (Since the copper used in the windings is already soft (annealed) and is not under tension, overheating of the conductors is generally not a concern.) Thermal cycling contributes to mechanical damage by loosening connections. Because of hysteresis in the transformer core, overloading generates harmonics and these can cause mechanical vibration of the transformer, contributing to physical damage. Overloading also...

Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is needed for aluminium melting, oil drying equipment using for power transformers and same that materia ...

Simulering av temperatur och varmeforluster i karna och lindning for en hogspanningstransformator... more Simulering av temperatur och varmeforluster i karna och lindning for en hogspanningstransformator “... Ett ljus som lyser dubbelt sa starkt, varar halften sa lange …”, i analogi med ljuset sa kan ...

Energy Procedia, 2009

Condensers for separation of CO 2 and steam are central devices in oxygen-fired power plants for ... more Condensers for separation of CO 2 and steam are central devices in oxygen-fired power plants for CO 2 capture. This work is the first part of a project aiming to optimize the design of a H 2 O/CO 2 Oxy-Fuel condenser. The project aims to achieve an in-depth understanding of the separation process at varying thermal conditions and with varying fluid compositions. COMSOL simulation tool has been used to study fluid flow, heat transfer and condensation process for H 2 O/CO 2 mixtures. The simulated condenser is a tank with all of its accessories. Boundary and initial conditions are set based on earlier works. H 2 O and CO 2 are considered as the main components for flue gas. The results show that with the proposed design, the condenser will be able to condense about 75% of water content in flue gas stream. The resulting flue gas stream after the condenser contains more than 97% CO 2. The information gained through the proposed project are important design data for improved condenser solutions that need to be implemented in order to reduce capital cost and increase the thermal efficiency of the power plants.

Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software's. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which design...

Electricity losses are one of the big anxieties for utilities. Electricity loss in Iran network a... more Electricity losses are one of the big anxieties for utilities. Electricity loss in Iran network according to Tavanir report is over 15% but individual researchers have different comments. Also, the lack of sufficient information is a network problem. To overcome on the problems authors used Top-Down/Bottom-Up method to estimate of losses in Iran’s electricity network. To achieve the model, at a certain moment measurements of input complex power in the feeder and voltages in the farthest network node and power flow calculation has been done. Using the estimated losses, authors suggest a strategy to losses reduction in every different part of distribution networks. Due to different culture, climate and network topology, losses are different and separate solution is needed. Proposed method was carried out by performing tests on a feeder with 88+35 nodes according to the IEEE 123 node test feeder. An economical investigation showed the benefits for utilities and improved the proposed plan. The main innovation in the presented paper is to combine a forecasting approach with experimental data to define a model for networks with unknown parameters.

Wide world's utilities are generating, transmitting and distributing of electricity throughout th... more Wide world's utilities are generating, transmitting and distributing of electricity throughout the country and are responsible to its quality. Distributed automated distribution system has been proposed for planning to reduce losses, optimize capacity and load balancing in electricity networks. The world electricity average loss is about and outage per customer time is about min/ year. The indices are needed to optimize in developing countries. This paper deals on a modeled distribution system in Sari distribution region and evaluates three mentioned parameters on network quality. Restoration, maneuvers to achieve the minimum loss, reactive power controlling, load balancing etc are investigated. Modeling performs by MATLAB software, EMTP for transient modeling and Digsilent with real data by Sari Distribution Company. In this paper, a new approach by rearrangement aimed at reducing losses and improving of load balancing in distribution networks was presented.

A parallel injection of short circuit current and transient voltage to medium and high voltage ci... more A parallel injection of short circuit current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is studied. Transient recovery voltage is created by a capacitor bank and is applied to CB. Also short circuit current is supplied by a Kv short circuit transformer. Texas DSP is used as controller and programmed in code composer. To test of circuit breakers by synthetic test equipments, an accurate control system can satisfy the test criterion. An optical triggered spark gap has been used to interrupt short circuit current and to initialize of transient recovery voltage (TRV) that is applied across the contacts of circuit breaker. Modeled results are verified by a laboratory based synthetic test system. Test object CB is a Kv, KA with vacuum type chamber. To find a desired sequence to open/close of backup-test object and auxiliary circuit breakers within appropriate time to inject of recovery voltage is main goal of the presented paper. Modeling and simulation has been done in MATLAB software. Test procedure has been done under IEC- ,- .

3rd IGEC conference, Sweden, 2007

“…A candle that burns twice as bright lasts half as long …” So too transformers can run at over r... more “…A candle that burns twice as bright lasts half as long …” So too transformers can run at over rated loadings within limits, consequently shortening their expected service life. Power transformers are vital devices in power industries. Electrical utilities have to pay a significant portion of capital investment costs for Power transformers. Although the useful service life of transformer is around of 30 years, but some times utility needs to achieve over loading of transformers. It can decrease transformer expected life. Over loading and other problems make a hottest spot point in windings and core and as a result, these lead to insulation degradations, loss of life and cooling problems. There fore, here is an increased interest in safely utilizing all available capacity. In order to design a power transformer it is essential to understand its performance in loading times, same as hottest spot temperature, temperature profile in windings and losses. Exactly these can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One important benefit on using of simulations before prototype is that the transformer can be modelled and simulated before it is built physically and that the consequences of varying dimensions and parameters easily can be tested. During the operation of power transformers, the critical parameter is the hottest temperature. The hot spot temperature (HST) has to be held under a prescribed limit. A cumulative effect of insulation aging, depending on time change of hot spot temperature, should be less than a planed value. Therefore, essentially utilities need to find a new method for hot spot detecting, monitoring and removing. In this thesis, I have suggested a new apparatus and system for hot spot point removing. The effects of oil spraying has been assessed, simulated and calculated. Using test data of 230/63/20kV Sari substation, simulation and calculation (using this device) have been performed; consequently it has been shown that electrical utility can mitigate the limitations of loading due to HST problem in transformers. Oil spraying system are investigated and modified to apply for local cooling. A robust algorithm have been proposed and trained for working out this task and are further optimally combined to give an improved accuracy. One important result of the thesis is the possibility to simulate temperature including the hot spot temperature and losses in the magnetic core material and windings.

This thesis investigates optimization of the control of electrical and thermal equipment by using... more This thesis investigates optimization of the control of electrical and thermal equipment by using numerical, FEM and CFD modelling in combination with dynamic simulation models. The thesis focuses on the production of electrical strips and the control system with the aim of reducing losses and improving magnetic properties. Several parameters and factors contribute to core losses. Thickness deviations in strip production, strip's grain sizes, high levels of impurities in the core, orientation, ageing, surface oxidation, overloading, and hot spot temperature (HST) are among the reasons for losses in the core. Some of the losses occur during strip cutting and core assembly. This dissertation focuses on the reduction of losses in the cold rolling and annealing in manufacturing steps, building factor in design of core sizes and HST managing in operation stages.

Power transformer parameter estimation with on-line data aquisition using the Kalman filter method

The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold r... more The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold rolled strip is being manufactured from hot rolled strip, the uniformity of width, thickness, hardness, etc. are all now intended for improvement. To reach to this target, need to abound control system to reach the higher quality of slabs. It should satisfy the several factors, as regards geometrical, mechanical, chemical and surface properties.Process control has taken advantage of new measurement equipments, new control actuators and algorithms. Automation and automatic process control can advance the quality further than what is achievable by manual control. This is an important desideration in rolling industry that rolling of slabs needs advanced and optimized process control to increase the productivity and reduction of the variations in the final properties.A typical cold rolling stand performs one step in a chain of processes in the cold rolling mill, which can include pickling, rolling, annealing, temper rolling and downstream processes. All these processes contribute to the final properties of the strips. When the main process or the main objective is well controlled, it is important to continue with the other processes. In continuous annealing furnaces, the temperature controls the mechanical properties, but temperature differences and bending around rollers change the flatness. Temper rolling needs the same flatness control as other cold rolling processes. Cooling and lubrication can affect several properties of the strips.Precise general control of the strip in a cold steel rolling mill will be discussed in this article.Typically, the rolling process is modelled with numerical techniques. But these are not appropriate for a controller design, because they are too difficult. Thus, a linear mathematical model for the rolling process is presented here, which describes the interaction of the required influencing parameters. The attempt leads to numerically professional algorithms, which are essential to run in a real-time situation. With the help of these linear descriptions, the vital elements for the control are investigated. Modern rolling mills are equipped with a servo-hydraulic gap adjustment system, eccentricity control of the rolls, thickness, speed, force and tension controls.A model to optimize of the control design process and increasing of accuracy is presented. In this way using the process transfer function in system at different control mode like to thickness, flatness, shape and etc designed a PID and PI optimized controller with using of the best optimization method, final properties increased. The measurements are used to verify the model approach and to detect the most significant sources of disturbances.A new linearised numerical model for the rolling process which is suitable for closed loop control has been developed. The model is based on the calculation of the operating point using an available numerical method, followed by determining the partial derivatives at the operating point with respect to all input parameters. Finally, the partial derivatives are combined using superposition to describe the behaviour of the complete system. In this manner, the changes in the output parameters can be determined for small changes in the input parameters. This calculation is numerically efficient and suitable for use in closed loop control.Moreover, the roll eccentricity problem and the possibilities to perform compensation will be explained here. Due to the great variety of solutions, a classification of the methods will be sketched. The basic properties of these classes are discussed. Then, a special solution is presented, which has proved its worth already in a practical application. The investigation of its properties is proposed to be typical for the every class, to which the method belongs.Finally measurement data which can be used to verify the new model will be performed. The model has been incorporated as a simulation system developed by the authors who enable the simulation of a multi-pass single stand rolling process. To get practical information about the rolling process, a data logging system was developed and installed in Sura AB for data collection.

Kanthal AB, the market's foremost supplier of heating solutions to industry, often creates op... more Kanthal AB, the market's foremost supplier of heating solutions to industry, often creates optimum solutions for each customer. One of their solutions is the High Power Reflector, which consists of a vacuum formed ceramic fibre 'hood' with an integrated Kanthal Super ceramic heating element. The performed project is to optimize heat performance of the High Power Reflector with respect to output power and temperature distribution. The task was solved using heat transfer simulations in with reflector different models. The simulation in COMSOL software environment in two-dimensional was performed to find the best reflector shape. Authors have simulated five different types of proposed reflectors. The temperature distributions were simulated as well as temperature profile and curve in 20 cm on the top of element until 50 cm have obtained, in this way with respect to higher out power and uniform temperature distribution, was found the optimized model of reflector and hood for...

Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs sh...

Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software’s. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which designs sh...

Hotspottemperature (HST)isthemostimportant parameter intheoperation ofpower transformers. TheHSTh... more Hotspottemperature (HST)isthemostimportant parameter intheoperation ofpower transformers. TheHSThasto beheldunderaprescribed limit. HSThasaconsiderable effect ontheinsulation aging. Therefore detecting, monitoring andremoving theHST couldbea very important andnecessary action forUtilities. A newdesign ofoil spraying anditseffect, alongwithathermal management ina transformer cooling system hasbeenstudied inthis paper. The effect ofoilfluidflow ontheHSTproblem hasbeenconsidered in thispaper;andthecalculations andsimulation havebeen performed byAntsalgorithm. Thesimulation results havebeen validated basedona230/63/20 kV,250MVAtransformer atthe Sarisubstation inIran,andtheresults indicate thatthenew design could mitigate thelimitations oftransformer loading dueto theHSTproblem. TheAntsalgorithm havebeenproposed and appliedfor accomplishing this taskandtogiveanimproved level ofaccuracy.

In medium voltage high MVA Turbo-generators, generally Roebel bars are used in slot area. To redu... more In medium voltage high MVA Turbo-generators, generally Roebel bars are used in slot area. To reduce the circulating current in slot area of Turbo-generators, transposed Roebel bars are located in slots. Because of that large turbo-generators trend to offer a top power density, winding strands being as a Roebel transposition form and strands are insulated against each other. Optimized structure of the Roebel bar can remove the circulating currents which have been generated in the stator windings. The structure of the bar causes an increase in volume of copper used in strands of windings. With increasing the copper volume and length of strands, the rugged magnetic field increases in the slot area. Because of this reason, eddy current losses grow in solid winding strands. Thus there must be a balance between eddy current losses and circulating current losses in Turbogenerators. The optimal transposition way based on a finite analysis model is used to create this balance so to optimize ...

Transformers are more complex devices, consisting of an iron core around which are wrapped variou... more Transformers are more complex devices, consisting of an iron core around which are wrapped various coils of insulated wires, inside a tank filled with insulating oil, along with connectors, bushings and various other small components. Overloading causes excess heat in a transformer, the negative effects of which are degradation of the kraft paper insulation around the wires (leading to internal failures of the coils), excessive tank pressure or degradation of the insulating oil (either of which can cause catastrophic failures, even explosions), and leaking gaskets and seals. (Since the copper used in the windings is already soft (annealed) and is not under tension, overheating of the conductors is generally not a concern.) Thermal cycling contributes to mechanical damage by loosening connections. Because of hysteresis in the transformer core, overloading generates harmonics and these can cause mechanical vibration of the transformer, contributing to physical damage. Overloading also...

Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 oc is needed for aluminium melting, oil drying equipment using for power transformers and same that materia ...

Simulering av temperatur och varmeforluster i karna och lindning for en hogspanningstransformator... more Simulering av temperatur och varmeforluster i karna och lindning for en hogspanningstransformator “... Ett ljus som lyser dubbelt sa starkt, varar halften sa lange …”, i analogi med ljuset sa kan ...

Energy Procedia, 2009

Condensers for separation of CO 2 and steam are central devices in oxygen-fired power plants for ... more Condensers for separation of CO 2 and steam are central devices in oxygen-fired power plants for CO 2 capture. This work is the first part of a project aiming to optimize the design of a H 2 O/CO 2 Oxy-Fuel condenser. The project aims to achieve an in-depth understanding of the separation process at varying thermal conditions and with varying fluid compositions. COMSOL simulation tool has been used to study fluid flow, heat transfer and condensation process for H 2 O/CO 2 mixtures. The simulated condenser is a tank with all of its accessories. Boundary and initial conditions are set based on earlier works. H 2 O and CO 2 are considered as the main components for flue gas. The results show that with the proposed design, the condenser will be able to condense about 75% of water content in flue gas stream. The resulting flue gas stream after the condenser contains more than 97% CO 2. The information gained through the proposed project are important design data for improved condenser solutions that need to be implemented in order to reduce capital cost and increase the thermal efficiency of the power plants.

Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is n... more Super heater elements concentrated in very high and clean power at temperature up to 1800 ºc is needed for aluminium melting, oil drying equipment using for power transformers and same that material. There fore, always it is need to minimize power consumption and increase effectiveness at power reflector customers. This means to minimize heat losses in the High Power Reflector, and to optimize heat performance with respect to output power and temperature distribution. This can be done by altering the size and form of the insulating ceramic fiber to have as much power as possible 'reflected' out from the module. It can also be done by altering the size and form of the element .It has been done and the task solved mainly by heat transfer simulations, using COMSOL and MTLAB software's. To minimize the number of different designs (and thus the number of calculations) were studied; it is also done that statistical methods for experimental design used to determine which design...

Electricity losses are one of the big anxieties for utilities. Electricity loss in Iran network a... more Electricity losses are one of the big anxieties for utilities. Electricity loss in Iran network according to Tavanir report is over 15% but individual researchers have different comments. Also, the lack of sufficient information is a network problem. To overcome on the problems authors used Top-Down/Bottom-Up method to estimate of losses in Iran’s electricity network. To achieve the model, at a certain moment measurements of input complex power in the feeder and voltages in the farthest network node and power flow calculation has been done. Using the estimated losses, authors suggest a strategy to losses reduction in every different part of distribution networks. Due to different culture, climate and network topology, losses are different and separate solution is needed. Proposed method was carried out by performing tests on a feeder with 88+35 nodes according to the IEEE 123 node test feeder. An economical investigation showed the benefits for utilities and improved the proposed plan. The main innovation in the presented paper is to combine a forecasting approach with experimental data to define a model for networks with unknown parameters.

Wide world's utilities are generating, transmitting and distributing of electricity throughout th... more Wide world's utilities are generating, transmitting and distributing of electricity throughout the country and are responsible to its quality. Distributed automated distribution system has been proposed for planning to reduce losses, optimize capacity and load balancing in electricity networks. The world electricity average loss is about and outage per customer time is about min/ year. The indices are needed to optimize in developing countries. This paper deals on a modeled distribution system in Sari distribution region and evaluates three mentioned parameters on network quality. Restoration, maneuvers to achieve the minimum loss, reactive power controlling, load balancing etc are investigated. Modeling performs by MATLAB software, EMTP for transient modeling and Digsilent with real data by Sari Distribution Company. In this paper, a new approach by rearrangement aimed at reducing losses and improving of load balancing in distribution networks was presented.

A parallel injection of short circuit current and transient voltage to medium and high voltage ci... more A parallel injection of short circuit current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is studied. Transient recovery voltage is created by a capacitor bank and is applied to CB. Also short circuit current is supplied by a Kv short circuit transformer. Texas DSP is used as controller and programmed in code composer. To test of circuit breakers by synthetic test equipments, an accurate control system can satisfy the test criterion. An optical triggered spark gap has been used to interrupt short circuit current and to initialize of transient recovery voltage (TRV) that is applied across the contacts of circuit breaker. Modeled results are verified by a laboratory based synthetic test system. Test object CB is a Kv, KA with vacuum type chamber. To find a desired sequence to open/close of backup-test object and auxiliary circuit breakers within appropriate time to inject of recovery voltage is main goal of the presented paper. Modeling and simulation has been done in MATLAB software. Test procedure has been done under IEC- ,- .

3rd IGEC conference, Sweden, 2007

“…A candle that burns twice as bright lasts half as long …” So too transformers can run at over r... more “…A candle that burns twice as bright lasts half as long …” So too transformers can run at over rated loadings within limits, consequently shortening their expected service life. Power transformers are vital devices in power industries. Electrical utilities have to pay a significant portion of capital investment costs for Power transformers. Although the useful service life of transformer is around of 30 years, but some times utility needs to achieve over loading of transformers. It can decrease transformer expected life. Over loading and other problems make a hottest spot point in windings and core and as a result, these lead to insulation degradations, loss of life and cooling problems. There fore, here is an increased interest in safely utilizing all available capacity. In order to design a power transformer it is essential to understand its performance in loading times, same as hottest spot temperature, temperature profile in windings and losses. Exactly these can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One important benefit on using of simulations before prototype is that the transformer can be modelled and simulated before it is built physically and that the consequences of varying dimensions and parameters easily can be tested. During the operation of power transformers, the critical parameter is the hottest temperature. The hot spot temperature (HST) has to be held under a prescribed limit. A cumulative effect of insulation aging, depending on time change of hot spot temperature, should be less than a planed value. Therefore, essentially utilities need to find a new method for hot spot detecting, monitoring and removing. In this thesis, I have suggested a new apparatus and system for hot spot point removing. The effects of oil spraying has been assessed, simulated and calculated. Using test data of 230/63/20kV Sari substation, simulation and calculation (using this device) have been performed; consequently it has been shown that electrical utility can mitigate the limitations of loading due to HST problem in transformers. Oil spraying system are investigated and modified to apply for local cooling. A robust algorithm have been proposed and trained for working out this task and are further optimally combined to give an improved accuracy. One important result of the thesis is the possibility to simulate temperature including the hot spot temperature and losses in the magnetic core material and windings.

This thesis investigates optimization of the control of electrical and thermal equipment by using... more This thesis investigates optimization of the control of electrical and thermal equipment by using numerical, FEM and CFD modelling in combination with dynamic simulation models. The thesis focuses on the production of electrical strips and the control system with the aim of reducing losses and improving magnetic properties. Several parameters and factors contribute to core losses. Thickness deviations in strip production, strip's grain sizes, high levels of impurities in the core, orientation, ageing, surface oxidation, overloading, and hot spot temperature (HST) are among the reasons for losses in the core. Some of the losses occur during strip cutting and core assembly. This dissertation focuses on the reduction of losses in the cold rolling and annealing in manufacturing steps, building factor in design of core sizes and HST managing in operation stages.

Power transformer parameter estimation with on-line data aquisition using the Kalman filter method

The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold r... more The main aim of cold rolling is reduction of strips to the desired final thickness. As the cold rolled strip is being manufactured from hot rolled strip, the uniformity of width, thickness, hardness, etc. are all now intended for improvement. To reach to this target, need to abound control system to reach the higher quality of slabs. It should satisfy the several factors, as regards geometrical, mechanical, chemical and surface properties.Process control has taken advantage of new measurement equipments, new control actuators and algorithms. Automation and automatic process control can advance the quality further than what is achievable by manual control. This is an important desideration in rolling industry that rolling of slabs needs advanced and optimized process control to increase the productivity and reduction of the variations in the final properties.A typical cold rolling stand performs one step in a chain of processes in the cold rolling mill, which can include pickling, rolling, annealing, temper rolling and downstream processes. All these processes contribute to the final properties of the strips. When the main process or the main objective is well controlled, it is important to continue with the other processes. In continuous annealing furnaces, the temperature controls the mechanical properties, but temperature differences and bending around rollers change the flatness. Temper rolling needs the same flatness control as other cold rolling processes. Cooling and lubrication can affect several properties of the strips.Precise general control of the strip in a cold steel rolling mill will be discussed in this article.Typically, the rolling process is modelled with numerical techniques. But these are not appropriate for a controller design, because they are too difficult. Thus, a linear mathematical model for the rolling process is presented here, which describes the interaction of the required influencing parameters. The attempt leads to numerically professional algorithms, which are essential to run in a real-time situation. With the help of these linear descriptions, the vital elements for the control are investigated. Modern rolling mills are equipped with a servo-hydraulic gap adjustment system, eccentricity control of the rolls, thickness, speed, force and tension controls.A model to optimize of the control design process and increasing of accuracy is presented. In this way using the process transfer function in system at different control mode like to thickness, flatness, shape and etc designed a PID and PI optimized controller with using of the best optimization method, final properties increased. The measurements are used to verify the model approach and to detect the most significant sources of disturbances.A new linearised numerical model for the rolling process which is suitable for closed loop control has been developed. The model is based on the calculation of the operating point using an available numerical method, followed by determining the partial derivatives at the operating point with respect to all input parameters. Finally, the partial derivatives are combined using superposition to describe the behaviour of the complete system. In this manner, the changes in the output parameters can be determined for small changes in the input parameters. This calculation is numerically efficient and suitable for use in closed loop control.Moreover, the roll eccentricity problem and the possibilities to perform compensation will be explained here. Due to the great variety of solutions, a classification of the methods will be sketched. The basic properties of these classes are discussed. Then, a special solution is presented, which has proved its worth already in a practical application. The investigation of its properties is proposed to be typical for the every class, to which the method belongs.Finally measurement data which can be used to verify the new model will be performed. The model has been incorporated as a simulation system developed by the authors who enable the simulation of a multi-pass single stand rolling process. To get practical information about the rolling process, a data logging system was developed and installed in Sura AB for data collection.