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The processes of inception, growth, and propagation of Partial Discharge (PD) along the dielectric are complicated. Their analysis requires a thorough understanding of underlying physics. A software simulation tool has been developed to study typical PD processes. The simulator generates pulses of varying amplitudes, shapes and time of occurrence of pulses observed in practice using National Instruments LabVIEW software as a base platform. The rise time of PD pulses plays an important role in the characterization of PD. The rise time formulation has been attempted based on the approach using the dipole moment development and law of conservation of energy. PD phenomenon is usually studied with the assumption of an air-filled void being energized by parallel plate/ coaxial cylinder electrode configuration. An SF 6 -filled spherical void inside a dielectric between two coaxial cylinder electrode plates is used as another configuration. Phase-resolved partial discharge (PRPD) pattern and the characteristics of PD pulses simulated are in agreement with results reported in literature. The contribution of this paper is versatility of the simulator for detailed study and comprehensive analysis of PD without the use of high voltage (HV) setup.

Supercapacitors complement the limitations of battery storage technologies, and therefore, a battery-supercapacitor hybrid storage device (HSS) has established as a viable option for mitigating the renewable energy variability. For optimal sizing of both batteries and supercapacitors, batteries are treated as low-frequency variation mitigation device and supercapacitors as high-frequency variation mitigation device. However, the maximum amount of current injected or extracted from the battery for a given capacity rating is limited, failing which, supercapacitors would replace batteries to mitigate low-frequency variability. Both slow and fast varying components are defined respecting a cutoff frequency, and in this problem, the objective is to minimize the annualized cost of HSS with optimal cut-off frequency. The sizing of the HSS should also minimize the variability for a given statistical significance. The cut-off frequency is iterated over the solution space using mode pursuing sampling method to obtain the optima. The proposed method is illustrated with a sample dataset and results are discussed. Additionally, an additional problem where the frequency of operation of the supercapacitors is limited to two hours to limit the self-discharge rate of the supercapacitors is also discussed.

Electrical Discharge Machining (EDM) is a manufacturing process in which erosion takes place due to sparking between a workpiece and a tool electrode. The EDM circuit consists of DC-DC converters, the EDM load and an interfacing circuit to regulate the machining. The DC-DC converter topologies are modified to suit requirements of the EDM load. Such modifications along with the nature of load and the interfacing circuit, give rise to issues specific to the EDM power supplies. For a particular topology with two DC-DC converters, such issues in modelling and control of the converters are addressed in this work. A new methodology to determine sizing of passive components is discussed. Pulsed current reference scheme is also illustrated, which can improve input to the EDM load efficiency by more than 30%.

Renewable energy (RE) resources are non-dispatchable due to their intermittent nature, and battery storage devices (BSDs) play an important role to overcome their inherent variability. Therefore, for optimal operability, BSDs must be appropriately sized. Historical RE generation data can be used for sizing, with the objective to minimize the annualized planning cost. Application of high and low pass filters about a given cut-off frequency on the frequency spectrum of the historical generation data, calculated using discrete Fourier transform approach, segregate the fast and slowly varying components. The proposed methodology is based on ${3} {\sigma }$ principle and will ensure minimum injection of RE-generation variability into the grid for day-ahead scheduling with both fast and slowly varying components. The analysis shows that the batteries with the minimum unit capacity cost to throughput ratio provide minimum annualized planning cost for both slow and fast varying components. Determination of sizing of BSDs for a given cut-off frequency is numerically “costly” and to obtain the optimal cut-off frequency, a derivative-free mode-pursuing sampling method is applied. Exponential reduction in the daily injection of variability with increasing statistical significance in sizing is observed. Impact of unit-capacity cost to throughput-ratio on the sizing of BSDs is also studied.

Ion Cyclotron Resonance Heating (ICRH) system has two different impedance matching systems for RF transmission. One is offline matching which has been used before applying the experimental shots. Another is online impedance matching which has been used during experimental shot. Offline matching network consists of two coarse tuner, static stubs and coarse phase shifter which are identical in both the transmission lines. There are motorized arrangement installed in each stubs and phase shifters. Both static and coarse stubs are used to vary length in order to match the source impedance with load impedance. Phase shifter is used for matching impedance via varying the phase of the power. Programmable Logic Controller (PLC) based instrumentation has been implemented for the system. Offline matching should be operated below 1 kHz frequency in order to move stepper motors using square pulses employed to motor controller. In existing system this operation has been carried out by VME instrumentation and control. In order to reduce load on VME, PLC based system has been designed and integrated with VME based DAC. SIMATIC Windows Control Center (WinCC) software has been used as SCADA i.e. front end user interface. WinCC SCADA can communicate with OPC (Open Process Control) server using different PLC signals. This paper describes technical details, design and development of PLC based offline impedance matching system using WinCC as SCADA. The developed system has proved accurate and reliable in use of application as per system requirement. The SCADA system also shows motor frequency and motor speed profile with upper and lower limits. It logs data at the end of operation by which it retrieve the last run status of each motor when it starts again.

Programmable logic controller (PLC) has been used for the development of data acquisition and control (DAC) system for 45.6 MHz, 100 kW ICRH system using EPICS. DAC can monitor and acquire 16 digital inputs, 16 analog outputs, 16 digital outputs and 32 analog inputs signals. Graphical user interface (GUI) has been developed using JAVA based control system studio (CSS) on eclipse platform. WebOPI module can display CSS BOY OPI in web browsers without modification to the original OPI file. Data acquisition needs multifunctional data acquisition hardware which comprises digital input, digital output, analog output and analog input channels with counters for synchronization of the system. LabVIEW based software has been developed for the same using proprietary USB based multifunctional DAQ hardware. Procured USB based DAQ module is capable to acquire data sample at 10 kHz rate with software as well as hardware trigger. PLC software has been developed using open source technologies. Acquire module has been proprietary items which can only use LabVIEW as development platform. It is necessary to develop an interface between PLC software based on EPICS to acquire module based on LabVIEW. Module has been integrated with required driver and tested with developed user interface. This paper explains the interface using EPICS PV which is an external variable from LabVIEW can be used to trigger an event in LabVIEW.

Isolated dc-dc converters are increasingly being used in many industrial and utility applications such as shipboard, hybrid and electric vehicles, microgrids, etc., for integrating the dc sources and storage devices. A modified dual transformer based asymmetrical dual bridged isolated dc-dc (MDT-ADB) converter is proposed in this paper. MDT-ADB consists of three stages: input, isolation, and output. The input stage consists of a full bridge converter (FB), the isolation stage consists of two high-frequency transformers, and the output stage consists of a semi-active three-leg converter (STL). In the isolation stage, the primary windings of the transformers are connected in series and the secondary windings are connected in parallel across the load via STL to share the load power equally which decreases the currents flowing through some of the switches of STL. Therefore, the switching losses of these switches are reduced. Further, MDT-ADB results in reduced circulating currents in the transformer windings as well as in a wider range of the output voltage and power as compared those in the existing dual transformer based asymmetrical dual bridge converter (DT-ADB). Additionally, all switches of MDT-ADB can be operated with soft switching to obtain reduced losses. A detailed analysis of the modeling and control of MDT-ADB is presented. The discussed theoretical analysis is verified using simulations and experimental results.

A recent huge interest in Machine to Machine communication is known as the Internet Of Things (IOT), to allow the possibility for autonomous devices to use Internet for exchanging the data. The Internet and the World Wide Web have caused a revolution in communication between the people. They were born from the need to exchange scientific information between instrumentation. Control System Studio (CSS) (Best Operator Yet Operator Interface) BOY OPI is not only an application but also a framework that can be extended with widgets and data sources. The framework provided implementations for all the common functionalities, such as XML file reader and writer, PV connection handling, abstract widgets, properties, OPI Runtime and OPI Editor. The framework can be extended using the extension points provided by the framework. Monitoring systems CSS are extremely important in Experimental Physics and Industrial Control Systems (EPICS). Most of them are based on client/server(C/S). This paper designs and implements a web based real time programmable logic controllers (PLC) data monitoring system on EPICS data. This system is based on browser and server (B/S). Using MODBUS/TCP communication data have been archived in EPICS. Then all data is displayed in a real time chart in browser (Internet Explorer or Firefox/Mozilla). The chart is refreshed every regular interval and can be zoomed and adjusted. Also, it provides data tips showing and full screen mode. Acquire of the data would be handled by multi-data acquisition card which has been hardwired communication with PLC using 24 VDC to 5 VDC and vice versa electronics circuit.

Anisotropy is an important phenomenon, which should be taken into account by the designers of magnetic circuits in electrical machines. Even the so-called non-oriented (dynamo) steels feature significant anisotropy. It is thus essential to work out new analytical methods and mathematical models, which may be easily implemented in CAD routines. The paper describes one of possible approaches to address the problem. The results of model prediction are compared to available measurement data for chosen grades of non-oriented and grain-oriented steels.

HTML5 [1] has been recently evolution in web technologies which enables user to create web based control system user interfaces (UI). These user interfaces can work on cross browser and cross device compatible. Control system studio (CSS) Operator Interfaces (OPI) allow user to create user interfaces with drag and drop fashion. These developed interfaces developed in CSS BOY[2] can be seamlessly display in web browsers without any modification in original OPI file using WebOPI [3]. For this purpose, WebOPI was implemented by SNS as a web-based system using Ajax (asynchronous JavaScript and XML) with Experimental physics and instrumentation control system (EPICS) [4]. On the other hand, it uses generic Python/JavaScript and a generic communication mechanism between the web browser and web server. This interface uses the epics channel access gateway in glue with OPI which enables monitor and control process EPICS variables with different widgets. Apache Tomcat web server has been used to deploy application. Programmable logic controller (PLC) based data acquisition and control (DAC) system has been developed for 45.6 MHz, 100 kW Ion Cyclotron Resonance Heating (ICRH) system using EPICS and MODBUS. It can monitor and control 32 analog inputs, 16 digital inputs, 16 analog outputs and 16 digital outputs using MODBUS protocol. Several python embedded as well as external script have been used in design of the control system software. WebOPI provides seamless interface between with local CSS OPI and EPICS process variables using channel access gateway. Multiple web browser based client can communicate with single instance of user interface simultaneously. This paper introduced WebOPI that facilitate the goal of bringing control system UIs to the web.

The VME based Ion Cyclotron Resonance Heating (ICRH) Data Acquisition Control system (DAC) is integrated for auxiliary heating experiment on SST-1 Tokamak. VME processor board contains real-time operating system which works as server and Linux based host computer contains client user interface and additional support software. ICRH-DAC is distributed into two sections one at RF Lab and second at SST-1 hall which are 200 meter far away from each other. RF Lab DAC is installed to take care of RF power generation part. SST-1 hall DAC is installed to take care of diagnostics, matching networks and interface vacuum. Both DACs are running on master-slave mode when synchronized operation is needed. This synchronization of both DAC could be possible with EPICS (Experimental Physics and Industrial Control System) process variables, which broadcast and describe itself in Ethernet. The existing system uses the TCP/IP socket communication between both DAC clients. EPICS provides channel access protocol layers which broadcast required process variable on periodic time interval which are available on network for communication. Master DAC communicates with central control system using high speed trigger network and message passing interface on Ethernet network. During experiment shot details available using TCP/IP socket communication to master DAC only with hardware trigger event. Slave DAC acquires data using experimental shot details available on network which are broadcasted by master DAC using EPICS process variables. Same way the interface vacuum monitored at slave DAC will be available to master DAC for interlock. The prototype program is used for real-time parameters transmission, dynamic graphical user interface, modification of the existing system with synchronization. This paper will describe the prototype software design of EPICS based ICRH DAC software to achieve desired goal of experiment.

Ion Cyclotron Resonance Heating (ICRH) Data Acquisition Control system (DAC) for 100kW, 45.6 MHz has been conceptualized for RF ICRH experimental activities in tokamak. This system will be used for control and monitoring for 2 kW, 20 kW and 100 kW RF amplifier stages respectively. Each lower stage amplifier output is fed to next higher stage amplifier. ICRH system consists of different power supplies for each stage. First two stages need single high voltage power supplies and 100 kW stage needs four power supplies named plate, filament, screen grid and control grid. For failsafe operation of the system, it needs DAC for control, monitor and synchronization of each RF stage respectively. As per requirement of the DAC, it needs 32 analog inputs, 32 digital inputs, 16 digital outputs and 4 analog outputs with 4 counter channels for synchronization of the system. This paper will describe engineering design of LabVIEW based DAC for 45.6 MHz, 100 kW ICRH system. There are three different threads for application development. (1) Data monitoring in graph/chart form as well as textual values which runs on every 100ms timescale periodically. (2) Control and interlocking for failsafe operation of ICRH system which will be catered by different digital and analog channels. Counter/timer cards will be used for triggering as well as pulse generation as per experiment requirement. (3) Data plotting after shot analysis. The data acquisition hardware should be facilitated with 32 analog inputs, 48 digital input/output and 4 analog outputs. User interface will be designed in LabVIEW with control logic implementation. DAC hardware low device driver should communicate with application logic which will be interfaced with user interface module. National Instruments (NI) data acquisition hardware will provide sufficient channels with required resolution needed for DAC.

This paper describes the development of a test bench for FPGA in the acquisition module of Ultrasonic flow meters. The test bench provides a very useful platform to test the FPGA code and locate the errors. It includes verification of the dual port memories and its functionality. It also is very useful for comparing current output with the desired one. The test bench gives errors where there is a flaw in the functionality or any module dysfunction. It gives high testability to the FPGA of acquisition module. The basic operation to be performed is the development of test bench which is written in Altera Quartus II and simulated using Modelsim Altera software. Simulation result for one of the test cases is described here along with the test bench code for the same.

This paper focuses on the development of a transformer model which can be used to study phenomena involving large range of frequencies. It takes into account real transformer geometries including constructional details. The winding is divided into number of sections and is represented by a ladder network. The magnetic field associated with each of the sections is solved by using 2-D axi-symmetric Finite Element Method (FEM) and connected to the ladder network at appropriate points giving a strongly coupled field-circuit model. First, the distribution of impulse voltage is obtained by using time domain analysis. Consequently, the model is used to realize the frequency response analysis with radial deformation condition. Merits of the model, which can take into account frequency dependent complex permeability, are finally explained along with possibilities of potential future work.

Solid state transformers (SSTs) have found widespread power applications in traction locomotives, distribution systems, smart grids, etc., where they are going to replace conventional transformers and associated power enhancement equipments to provide better power quality features and functionalities. An eminent structure of SST comprises of three power conversion stages: input (AC-DC), isolation (DC-DC), and output (DC-AC). Multilevel converters are incorporated in several SSTs for operating at high voltage levels. This paper presents a three phase multilevel converter based SST (MCSST) which contains Cascaded H Bridge (CHB) multilevel converters in its input stage. Most of the reported topologies of MCSST have a common low voltage DC (LVDC) bus and a common control block for the entire SST structure. The presented MCSST consists of three independent phase modules and each phase module is controlled separately. Therefore, the outputs of these modules can be applied to both three phase loads as well as three independent single phase loads. Such a configuration can also be used to operate effectively under unbalanced load conditions. The discussed analysis of the reported work is verified using PSCAD/EMTDC simulation results.

Transformers are the most vital parts of any electrical supply system. The reliability of a supply system is largely dependent on the reliability of the transformers. Thus, timely fault diagnosis in a transformer can contribute to the robustness of the electrical supply system. Available techniques for diagnosis of abnormalities in a transformer are part specific and do not detect complete range of all possible faults. Also, different techniques may not be concurrent while detecting the same fault. To overcome this issue, three popular techniques which cover a wide range of faults are integrated using multi-agent systems (MAS). These techniques are modeled as agents using Java Agent Development Environment (JADE) platform to make them capable of communicating among themselves to ensure effective decision making. The goal is to design an approach enabling detection of problems in transformers which can lead to accurate prediction of faults without continuous human monitoring. A tool with a graphical user interface (GUI) is also made using java programming.

In the axial magnetic field (AMF) type of vacuum interrupters (VI), the design of their contact system is such that the magnetic field is oriented parallel to the arc. AMF keeps the arc diffused, and the value of the currentup to which the arc stays diffused depends on the contact diameter and the magnitude of the axial field. A certainminimum AMF is required to keep the arc diffused. AMF also induces eddy currents in the contact discs. This paperanalyses the effect of eddy currents induced in the discs on AMF between the contacts, especially near the currentzero region. This analysis incorporates the opening motion of the contacts along with the variation of the coil currentwith time. Initially, a 2-D axis symmetric model of the AMF contact is simulated to determine the radial variation ofthe magnetic field along a plane mid-way between the two separating contacts. A 3-D model of the AMF contact is then analyzed to include the effect of radial slots in the contact plate. The change in the magnetic field profile with the number of slots is studied.

In multi-element coupled lines, the effect of junction discontinuity is unavoidable. These are found prominent in the high power coupled lines for HF and VHF applications because of larger structural dimensions. For the development of a 200kW tandem 3±0.2dB ultra-wideband hybrid coupler, design and simulation of a 3-elements 8.34±0.2dB coupled section is performed. In simulation results, coupling and output parameters of the designed coupled section are found significantly deteriorated from the theoretical prediction. The problem is investigated and found associated to the effect junction discontinuity. Junctions that are employed to join the elements produce undesirable reactive effect known as junction discontinuity effect. An analysis of the junction discontinuity effect in multi-element coupled lines and its compensation using novel approach is presented.

The use of few terminal capacitance measurements at selected high and low frequencies can help in determining the location and extent of deformation in a transformer winding. A deformation coefficient derived from the measurements is used for this purpose. The mathematical basis and characteristics of the coefficient are elaborated. The method is tested for detecting radial and axial deformations in a real size coil. Two case studies involving radial and axial deformations are presented to demonstrate the efficacy of the approach. The suitability of the method for detecting combined axial and radial deformations is also demonstrated. Finally, the method is validated on a 500 kVA transformer.

In recent years, Power Electronic Transformers (PETs) are being used in micro-grids, distribution systems, renewable energy systems, traction applications etc., due to their power quality enhancement capability and reduced weight as well as size. The design and operation principles of a three phase active rectifier based PET are analysed in the paper. The structure of PET consists of three parts: a three phase active front end rectifier, a dual active bridge (DAB) based isolation stage, and an inversion stage. A novel dq-vector based control strategy for the rectification stage is explained that does not require phase locked-loop (PLL) to calculate the phase angle, maintains unity power factor at the input side, and provides constant DC voltage at the rectifier output terminals under variable load conditions. A modest controller is used for DAB to generate a desired DC-link voltage signal for the inverter circuit. In addition to unity power factor and constant voltage characteristics, bidirectional power flow can also be possible using the discussed topology. Simulation results using PSCAD/EMTDC are presented to validate the discussed topology and the controller.

The main focus of this article is to investigate the relation between recovery voltage peaks and moisture content in oil-paper insulation system in power transformers. It investigates the causes of non-standard recovery voltage peaks and uses an algorithm to simulate different oil-paper moisture conditions. Two different transformers have been studied and an attempt has been made to correlate the shifting of recovery voltage peaks in the response to variations in oil and paper moisture contents. A brief discussion on the appearance of subdominant peaks has also been given to relate their presence with interfacial polarization processes.

Frequency response analysis (FRA) is a well accepted condition monitoring technique for power transformer windings. The low-frequency region (generally, below 10 kHz) of the response is governed by the magnetic circuit. It is generally observed that the shape of frequency response in terms of the driving point impedance for the central phase and the end phases is inverted `V' and inverted `W', respectively, in the low-frequency region. A qualitative explanation for the above phenomenon is presented in this work. A step-by-step calculation of core parameters and their variation with frequency for different phases have been explained. Two different approaches, viz. a coupled field-circuit approach based on finite element formulation and a method based on duality principle, are employed for modeling. Results of the two methods have been verified with experimental data.

This paper discusses an elegantly simple on-line approach for deformation diagnostics of transformer winding. The Current Deviation Coefficient (CDC) derived from terminal current measurements at a selected high frequency (HF) is found to be an effective indicator for locating deformed section of the winding. Also, any deviations of HF terminal currents from their fingerprint values can be used to find the extent of deformation. An on-line method for detecting winding deformations in three-phase star- or delta-connected winding is also elaborated in the paper. Finally, a proposal for simultaneous on-line monitoring of HV and LV windings using the novel on-line approach is discussed.

Partial discharge (PD) is one of the main causes for eventual equipment failure and it occurs where the electric field exceeds the local dielectric strength of the insulation. The PD signal captured at UHF has many advantages. The finite difference time domain (FDTD) technique, which is a widely used electromagnetic computational method, has been used to model propagation PD discharges generated in the form of a Gaussian pulse. The wave propagation in free space, oil and with a cylindrical metallic obstruction representing core/winding, in the two dimensions is realized and presented in this work. The perfectly matched layer (PML) which is a flexible and efficient absorbing boundary condition (ABC) has been incorporated in the simulations. Further, for localization time difference of arrival (TDOA) approach has been used.

Directional couplers are used to monitor forward and reflected high RF powers. At Mega Hertz range of frequencies, normally loop type directional couplers are used. The loop samples electric or magnetic fields. The penetration and orientation of the loops are adjusted in such a way that the magnitude of electric and magnetic current is same in the two arms of the loop. In this configuration one arm of the loop shows incident power while the other arm gives reflected power. Secondary arm is terminated into 50 ohm in order to avoid multiple reflections. The rectangular coupling loop used in the developed directional coupler is having the dimensions of 46 mm times 19.5 mm (W X H). It is made up of copper. The directional coupler developed can be pressurized up to 3.0 bar absolute pressure. A specific Teflon cup design is used to pressurize the directional coupler. The size of the directional coupler is 6 1/8" EIA standard. The inner and outer conductors are made from 99.5% ETP copper. Flanges are made from 60:40 electronic grade brass. Inner conductor joints are of brass with silver-plating. The return loss obtained is better than 30 dB. The coupling factor is variable from 40 dB to 57 dB depending upon probe penetration.

The vacuum interrupter is extensively employed in the medium voltage switchgear for the interruption of the short-circuit current. The voltage across the arc during current interruption is termed as the arc voltage. The nature and magnitude of this arc voltage is indicative of the performance of the contacts and the vacuum interrupter as a whole. Also, the arc voltage depends on the parameters like the magnitude of short-circuit current, the arcing time, the point of opening of the contacts, the geometry and area of the contacts and the type of magnetic field. This paper investigates the dependency of the arc voltage on some of these parameters. The paper also discusses the usefulness of the arc voltage in diagnosing the performance of the contacts.

High amount of direct current is essential in many industrial processes. Conventional methods for obtaining high amount of direct current involve parallel operation of converters with interphase or five-legged rectifier transformer. The interphase transformer (IPT) and/or rectifier transformer employed in the system increase overall size of the system and also provide limited control over the operation. This paper presents simpler topology of high frequency AC-DC converter specially for low-voltage high-current industrial applications. In the proposed topology, rectifier module and low frequency L-C filter in the primary stage (required for conventional high frequency converters) are eliminated. The topology provides better control over the operation and helps in reducing size of the overall rectifier system. The topology is simulated for a practical application of 12 V, 5000 A rectifier system. The three-phase high frequency transformer present in the topology is designed and its estimated size is compared with the existing five-legged rectifier transformer for the conventional system.

The Electrical Engineering undergraduate programme at Indian Institute of Technology, Bombay (IIT-B) gives students an exposure to power engineering subjects, while the department offers a specialization in Power Electronics and Power Systems at the graduate level. Whereas the laboratories in power engineering are an integral part of both programmes, traditional power engineering laboratories, i.e., machines, power electronics and power systems have undergone changes in style and content, and in line with the new developments in the field. This paper describes the salient features of the instructional laboratories at IIT-B.

This work presents the use of terminal capacitance measurements to detect deformations in transformer windings. The lumped parameter representation of windings is considered. The deformation coefficient (DC) derived from the measurements is used to detect winding deformations. The extent and location of deformation can also be determined by this method. This paper presents the mathematical basis underlying the method of using DC for windings. The formulation of DC is also explained. Simulation results are given to demonstrate the applicability of the method for deformation diagnostics.

Insulation degradation is the primary reason for aging and eventual failure of electrical equipment. Any measurement that forewarns an impending breakdown of the equipment can be a boon to asset managers. Partial discharge (PD) is one such phenomenon that can be monitored for assessing the quality of insulation. However, the phenomenon of PD is quite intricate and requires an understanding of various concurrent processes. In this paper, some of the methods used to simulate this complex event have been reviewed. At the fundamental level, PD is a localized breakdown that occurs without complete bridging of the insulation. These are feeble and extremely fast, nanosecond discharges. They can be thought of as motion of charges under the influence of an external electric field, which has exceeded the breakdown strength in a small region of the insulation. When such discharges occur in voids in solid insulation, they generate signals in the electrical, chemical and acoustic domains. Also, PD causes physical damage due to bombardment of these charged particles on the walls of the void. The charges are generated by ionization of the gas filled in the void. Once ionized, the motion of these particles is governed not only by the external field, but also by the space charge so created. There are various methods that can be used to simulate the motion of these charges.

Summary form only given. The split-winding arrangement requires special short circuit design considerations. During short circuit conditions, there is a considerable distortion of the leakage field, which in turn produces high axial short circuit forces. This paper deals with the computation and analysis of electromagnetic forces in windings of split-winding transformers. A nonlinear-transient field-circuit coupled finite element model is used to simulate the split-winding transformer. A 70 MVA, 3-phase, 220/6.9/6.9 kV split-winding transformer is modeled under pre-set and post-set short circuit test conditions. Under the pre-set condition, the transformer is analysed with one as well as both the LV windings short-circuited to compare the axial forces produced in the windings for these two cases. The results show that there is a considerable rise in the axial forces when one winding is short circuited as compared with the case when both windings are short-circuited. The effect of initial magnetization of core on axial short-circuit forces is calculated and discussed. It is also shown that even though post-set method eliminates inrush related problems there is not much respite in short circuit forces.

Sympathetic inrush current phenomenon occurs when a transformer is switched on in a power system network containing other transformers which are already energized. In this paper, the phenomenon of sympathetic inrush current is investigated using nonlinear-transient field-circuit coupled finite element formulation. The cases of the transformers connected in parallel and in series have been considered. The results obtained for a 31.5 MVA, three-phase transformer are presented and discussed in detail. This work also includes the investigation of parameters affecting the magnitude and duration of sympathetic inrush phenomenon, such as series resistance, switching-on angle, residual flux density and load conditions. These analyses provide a sound theoretical basis for a thorough understanding of the phenomenon.

The half-turn effect is present in transformers if the winding leads are taken out from the different sides of the core. The result is an additional half-turn in one of the core windows in a single-phase transformer, which can create overfluxing of the core leading to excessive losses and temperature rises. This paper presents a methodology to analyze the half-turn effect in power transformers. A nonlinear field-circuit coupled model is used to simulate the half-turn effect; the magnetic field is modeled using the finite-element method. The results show that there is a considerable increase in the flux density values in the core during load loss test, and the increased core losses can be comparable to the values under the rated voltage condition. The results obtained by the proposed methodology are validated with the experimental test results on a single-phase 40-MVA autotransformer. The half-turn effect can be eliminated by taking both the leads from the same side of the core. However, in order to reduce insulation clearances, a few compensating turns are wound on the end limbs to eliminate the half-turn effect. The paper also reports the experimental and the simulation results with the compensating turns. Analysis of the high induced voltages in the unexcited windings of the other phases during the load-loss test on the middle phase of three-phase three-limb transformers is also reported. In the three-phase five-limb transformers, the effects of half-turns in the three phases are almost cancelled under the balanced load conditions; this paper highlights the possibility of the core saturation due to the half-turn effect under appreciable unbalanced load conditions., IEEE

The parallel operation of two three-pulse controlled converters with interphase transformer (IPT) is modeled and analyzed. An IPT absorbs voltage difference between DC voltages of the two converters at any instant and ensures independent operation without any circulating current. It also results in six-pulse output voltage resulting in less harmonic distortions. The complete circuit is solved by using modified nodal analysis (MNA) and magnetic nonlinearity in the IPT core is taken into account by dynamic inductance model. Power electronic switches are modeled as small and large resistances during ON and OFF states. A code has been written to model and simulate the circuit under balanced and short circuit conditions.

Electromagnetic force calculation is essential in the analysis and design of any electrical machine. There are two kinds of forces, the magnetization force and the JtimesB force, which play an important role in the behavior of any electrical machine. This work involves development of finite element code for the calculation of electromagnetic force on a permeable material. Maxwell's stress tensor (MST) method has been implemented to calculate the force. This has been used to analyze the forces on an embedded conductor slot of a rotating machine.

The 200 kW generator is designed and developed for ion cyclotron resonant heating (ICRH) experiments on Aditya Tokamak and 1.5 MW stage for SST-1 (steady-state super-conducting tokamak 1). The 200 kW stage uses 4CM 300,000GA tetrode. An existing DC power supply capable of delivering 30 kV, 20 A has successfully reconfigured with necessary protections and controls. This is being used for ICRH experiments in Aditya tokamak. screen grid power supply of 1 kVDC, 1 amp, filament power supply of 18 VAC, 430 Amp, have been developed in-house, while the control grid power supply is procured indigenously. High voltage power supplies for the pre-driver stage (2 kW), driver stage (20 kW) have been designed and commissioned along with necessary protections. All the high voltage and auxiliary power supplies can be operated and controlled in manual or remote mode through data acquisition and control (DAC) system. The existing 200 kW system would be augmented with the 1.5 MW stage for experiments on SST1 tokamak This paper presents the details of auxiliary and high voltage power supplies that are developed in house for 200 kW stage. The monitoring and arc protection circuits are described. Results of the wire-burn test are highlighted.

Hybrid optimization model for electric renewables (HOMER), developed by National Renewable Energy Laboratory (NREL), enables economic analysis for single source and hybrid distributed energy resources (DERs). However, current version of HOMER does not support microgrid analysis. In this paper, economic analyzer for distributed energy resources (EADER) is developed. It finds minimum cost of energy (COE) and optimal mix of DERs with multiple sources and sinks. In addition to single source distributed generator (DG) and hybrid DG, EADER is also capable to analyze microgrid. EADER results are validated for single source DG and hybrid DG with results obtained from HOMER for the same systems. Further, a sample practical system from Western Maharashtra, India, is analyzed using EADER. The results which consider all practical constraints are presented and discussed.

This paper discusses power sector reforms and restructuring in India. After the initiation of economic reforms in the year 1991, the Government of India also embarked on the reforms in the power sector. Power development and reform programme scheme which has started yielding results in various region of the country. The projects funded under this scheme are aimed at: improving financial viability of state, reducing T&D loss, improving reliability and bringing transparency.

Experiments were conducted to detect partial-discharge (PD) pulses in the presence of solid dielectrics (PTFE and glass-filled epoxy) as well as breakdown pulses in SF/sub 6/, N/sub 2/, and SF/sub 6/-N/sub 2/ mixtures under uniform field conditions using a broadband detection system. The effects of circuit parameters, overvoltages, gas pressure, and the distance between electrodes on pulse shapes were studied for various proportions of SF/sub 6/ in SF/sub 6/-N/sub 2/ mixtures. The observed PD pulses are similar to breakdown pulses for longer electrode gaps (>0.3 cm). In the case of surface discharges the pulses are oscillatory in nature and inconsistent in shape and magnitude. The effect of saturation on the increase in breakdown voltage of SF/sub 6/-N/sub 2/ mixtures with increase in percentage of SF/sub 6/ (i.e. synergism) is also observed in the presence of the solid dielectric. This synergistic effect is reflected in corresponding observed PD pulse shapes. >

In broadcast fading channel, channel variations can be exploited through what is referred to as multi-user diversity and opportunistic scheduling for improving system performance. To achieve the gains promised by this kind of diversity, the transmitter has to accurately track the channel variations of the various receivers, which consumes resources (time, energy, bandwidth), and thus reduces the resources remaining for effective data transmissions. The transmitter may decide not to acquire or probe the channel conditions of certain receivers, either because these receivers are presumably experiencing severe fading, or because the transmitter wishes to spare resources for data transmissions. It may also decide to transmit to a receiver without probing its channel; in such cases, the transmitter guesses the channel state, which often results in a reduction of the transmission rate compared to when the transmitter knows the channel state. Ultimately, the transmitter has to decide to which receiver it should transmit. In this paper, we identifying the joint probing and transmission strategies realizing the optimal trade-off between the channel state acquisition and the effective data transmission. The objective is to maximize the system throughput. Finally, we propose several extensions of the proposed strategy, including a scheme to maximize the system utility and a scheme to ensure the system stability., 10.1109/78.845940, © IEEE

Although eddy current losses in flitch plates of large power transformers may form a small part of total transformer losses, they are important because they can appear concentrated in a small area and cause hazardous hot-spots. An analytical method to calculate flitch plate eddy loss is a very useful practical guide to a transformer designer, but for high power transformers, a more accurate analysis by techniques such as the finite element method (FEM) is desirable. A series of 2-D FEM simulations, using a statistical technique-orthogonal array design of experiments, have been carried out to find the effect of various factors on the losses in a mild steel flitch plate. The procedure for carrying out the experiments and the results obtained thereof are presented. The more involved analysis of slotted flitch plates, has been done using 3-D FEM. Loss and eddy current patterns in mild steel and stainless steel flitch plates have been studied. In both cases, the effect of the number of slots and dot length on the losses is discussed. Effect of slots on eddy current pattern is explained. Results of simulation of laminated flitch plate are presented. The eddy loss distribution obtained by 3-D FEM electromagnetic analysis is used in 3-D FEM thermal analysis to estimate temperature rise of the pitch plate Verification of 3-D FEM analysis has been done by measurement of temperatures on a slotted mild steel flitch plate of a 33 MVA, single phase, 220/132/11 kV autotransformer. The estimated temperatures have been found to be in good agreement with that obtained by measurements., IEEE