Transient analysis of a distribution transformer using ATP-EMTP

Electrical systems are subjected to constraints more severe continuation with overvoltage's which can be due to lightning and switching strikes. Under the influence of the intense corona effect which accompanies of atmospheric overvoltage, these overvoltages undergo deformations at the same time as an attenuation of their amplitude, this phenomenon of distortion, which is superimposed on the distortion by skin effect, is due to the dissipation of energy by injection of space charges around the conductor, this process with place as soon as the instantaneous voltage exceeds the threshold voltage of the corona effect conductors. In this paper, an analogical model of the corona effect has been implemented in the Alternative Transients Program/ Electromagnetic Transients Program (ATP/EMTP). This model was incorporated into a transmission lines, the line is divided on a number of the short sections. This study is to have the attenuation and the distortion of the overvoltage waves due to the corona effect on this transmission line.

The gate-controlled series capacitor (GCSC) was proposed initially for series compensation of transmission line to control power flow. Then, it was shown that, in some conditions, the GCSC could damp SSR even if no specific controller is used. In the present work, the GCSC was tested for mitigation of subsynchronous resonance (SSR) including a control loop. A detailed analysis of the use of the GCSC with turn-off angle control for SSR damping is presented. The power system used for the analysis of this phenomenon was the first IEEE benchmark. The actual possibility of eliminating SSR was verified by digital simulation using the ATP/EMTP (alternative transients program /electromagnetic transients program). As a result is it possible to say that GCSC is a powerful device for controlled series compensation both for power flow control and SSR damping

This paper describes the design process of a fast pulse generator, based on a transmission line (TL) system and a spark gap, including its experimental validation. Design criteria and expected parameters are described. Simulation results for the pulse generator obtained with a TL model are presented. This model is implemented using the software package Electromagnetic Transient Program-Alternative Transient program (EMTP-ATP). A constructed pulse generator [based on the mentioned design as well as the simulation results using EMTP-ATP and finite-element method (FEM)] is presented and laboratory test results are described. Simulations and experimental results fit well, except for a difference of 15% in the rise time. The proposed design procedure, which combines TL simulations, theoretical models, and FEM simulations, has been experimentally validated and it can be used to design pulse generator systems for different applications.

Voltage sags and swells are among the power quality disturbances that represent the biggest economic losses for affected users. It is therefore necessary to undertake a suitable characterization of those events to conduct studies that permit the causes and possible mitigation techniques to be identified. This work describes the development of monitoring modules to characterize voltage sags and swells that could be used in Electromagnetic Transients Programs - EMTP (for example the ATP – Alternative Transients Program). The implemented module uses a novel method to characterize these disturbances. The results of the implementation show that the voltage sags and swells are appropriately characterized; furthermore, less sampled data is required from a voltage signal with respect to the conventional RMS voltage method. This could optimize the capture and analysis process of information in power quality monitoring.

The EMTP (Electromagnetic Transients Program) is a general purpose program originally developed for simulating transient phenomena in power systems. Although the EMTP has important limitations and drawbacks, it is a suitable tool for the simulation of power converters and electric drives. A new version, the so-called SALFORD ATP (Alternative Transients Program), has been recently released; this new program incorporates some capabilities very attractive for the simulation of power electronics. The authors present a short summary of these options and illustrate their advantages and limitations for the simulation of power converters and drives. >

Modelling for very fast transients (VFTs) requires good knowledge of the behaviour of gas insulated substation (GIS) components when subjected to high frequencies. Modelling usually takes the form of circuit-based insulation coordination type studies, in an effort to determine the maximum overvoltages and waveshapes present around the system. At very high frequencies, standard transmission line modelling assumptions may not be valid. Therefore, the approach to modelling of these transients must be re-evaluated. In this work, the high frequency finite element analysis (FEA) was used to enhance circuit-based models, allowing direct computation of parameters from geometric and material characteristics. Equivalent models that replicate a finite element model’s frequency response for bus-spacer and 90° elbow components were incorporated in alternative transients program-electromagnetic transients program (ATP-EMTP) using a pole-residue equivalent circuit derived following rational fitting using the well-established and robust method of vector fitting (VF). A large model order is often required to represent this frequency dependent behaviour through admittance matrices, leading to increased computational burden. Moreover, while highly accurate models can be derived, the data extracted from finite element solutions can be non-passive, leading to instability when included in time domain simulations. A simple method of improved stability for FEA derived responses along with a method for identification of a minimum required model order for stability of transient simulations is proposed.

This article presents a fast, hardware efficient logic for fault detection and classification in transmission lines. The proposed logic employs only one-terminal current samples and is based on multi-resolution wavelet analysis. First-level high-frequency details of the modal currents in the range of 5 to 10 kHz are extracted. Depending on the amount of high-frequency components in the transformed current signals after processing, the faults are classified into ten types. An adaptive threshold value is chosen, rather than a fixed threshold in the case of faults involving the ground, to make the classification reliable and accurate. The validity of the proposed logic was exhaustively tested by simulating various types of faults on a system modeled in Alternative Transient Program (ATP)/Electromagnetic Transient Program (EMTP).The proposed logic was found to be acceptably reliable and accurate even in the presence of fault resistance and current transformer (CT) saturation.

Most Brazilian utility companies normally do not treat failures in distribution transformers as a relevant problem in large financial point of view, since any preventive action to minimize them within the current reality can be more costly. Thus, proper policies for investigating faults in distribution transformers are usually disregarded by the power utilities and sometimes policies may not even exist. In this context, existing information on faulty distribution transformers may not contain important data. However, new laws affecting power distribution companies are becoming more severe and there are demands for greater efficiency. In this new scenario, a forensic methodology to analyse faults in distribution transformers, created some years ago by many utilities, has recently been resurrected with the analysis of 3,159 distribution transformers. This methodology is known as Forensic Analysis Applied to Distribution Transformers (FAADT). New tests and trials as measuring insulation resistance, polarization index and dielectric absorption, physical and chemical analysis among others, will be added to the forensic methodology to improve it. Moreover, the surgearresters, being part of the system of protection of distribution transformers, are also studied in order to evaluate possible design flaws and challenges to overcome.

Most Brazilian utility companies normally do not consider failures in distribution transformers to be a great economic issue, since detecting these faults can be more costly in terms of time and resources. Thus, proper policies for investigating faults in distribution transformers are usually disregarded by the power utilities and sometimes policies may not even exist. In this context, existing information on faulty distribution transformers may not contain important data. However, new laws affecting power distribution companies are becoming more severe and there are demands for greater efficiency. In this new scenario, a forensic methodology to analyze faults in distribution transformers, created some years ago by many utilities, has recently been resurrected with the analysis of 3,159 distribution transformers. This methodology is known as Forensic Analysis Applied to Distribution Transformers (FAADT). This paper, which analyzes eight damaged distribution transformers, randomly selected from ELEKTRO's distribution lines, validates and refines the FAADT methodology. In order to do this, in addition to FAADT parameters, other parameters, such as polarization and dielectric absorption indices, turns ratio, insulation resistance and physicochemical analyses were also verified.

This paper adapts a method of modeling internal winding faults of three-phase power transformers for single-phase distribution transformers. The model which is compatible with the alternative transients program, ATP, allows the simulation of turn-to-earth and turn-to-turn faults on either windings of a single-phase, two-winding, distribution transformer. Results of staged internal winding faults of a distribution transformer are compared with the simulation results to validate the model. The experimental results were found to be comparable to those of the simulation.

Summary form only given. For observing interior of dense plasmas, intense, point-spot X-ray source is generated by X-pinch technique <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . Required parameter of the pulse generator is the rate of current rise 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> A/s, i.e. 100 kA of current and 100 ns of current rising time <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .To generate X-ray source by using X-pinch system, PFN module3 was used, having the advantages of holding high peak current, simple fabrication, and so on. The circuit topology of the PFN module through circuit simulations has been optimized, and three-stage LC-ladder of PFN is suitable for the table-top power supply for X-pinch. The inductance component included in the generator is strongly affected to the rate of current rise. In order to reduce the inductance of the X-pinch system, we evaluate the inductance and the rate of rise, experimentally. The PFN modules were coaxially arranged in octagon plates, and 48 PFN modules can be connected to drive the X-pinch. The PFN module consists of a three-stage LC-ladder circuit, which 73 nH of the inductance and 2700 pF of the capacitance. The discharge device has a coaxial configuration to reduce the inductance. The load current flowing through the inductance measured using a Rogowski coil, contained in the device was determined by comparison between the calculated results with Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP)4. The rate of current rise obtained was 1.7 x 1011 A/s. From these experiments, the electrode inductance of 65 nH was estimated from the results calculated by the ATP-EMTP. The charging voltage to achieve the target rate of current rise is evaluated to be about 60 - 80 kV.

Distribution transformers are used widely for distributing electric power to industrial and commercial loads. Several techniques are used to prevent the damage of distribution transformers and their easy maintenance. However, this paper provides an internet of things (IoT) based scheme for monitoring, control, and protection of distribution transformers. Many distribution transformers must distribute power over a wide area, focusing on the transformer's performance. Presently, distribution transformers are monitored manually where; an engineer visits the transformer site at regular intervals to record parameters of importance that reflect the transformer's health. The hardware relay of this work does not require an engineer to visit the transformer. The data is directly received on the server, and a control action can be taken remotely from anywhere around the world, which is essential today. The developed IoT-based relay displayed the occasionally occurring overloads and the temperature of oil, winding, and humidity and protected the transformer against internal fault. Furthermore, the dual-slope bias differential algorithm protects the transformer facing the inrush current harmonic and external fault false-operation. The hardware implementation shows that the relay is cost-effective and accurate for monitoring, controlling, and protecting the transformer.

For distribution lines in Japan, protection measures against lightning induced overvoltages have been taken and can be considered almost complete. The focus of lightning protection measures has moved to overvoltages due to direct lightning strokes. Studies of such overvoltages require simulations using the EMTP (Electro-Magnetic Transients Program), and components of a distribution line must be modeled appropriately in the EMTP simulation environment. The authors have proposed an EMTP model of a distribution line in a separate paper.This paper consists of two parts. The first part presents surge characteristics of a distribution line obtained by measurement using an actual-scale test distribution line. Especially, the result reveals noteworthy characteristics of the surge impedance of a reinforced concrete pole and the wavefront-time dependence of insulator voltages. The second part presents validation of the distribution line model previously proposed by the authors. The validation shows that the distribution line model accurately reproduces the measured voltage and current waveforms for various wavefront times of injected currents.

Arcing horns interrupting fault current is a new type of arcing horns installed on transmission-line towers, which act to interrupt fault current independently within one cycle of commercial frequency. In this paper, we have developed an Electromagnetic Transients Program (EMTP) simulation model of the arcing horns interrupting fault current to ascertain the application effects and devise an installation strategy. The EMTP simulation model can consecutively simulate the entire process, from fault occurrence to fault clearing, by integrating two different kinds of macroscopic arc models, and is capable of dealing with the entire short-circuit current range by taking into account the characteristics of the arc parameters. Finally, we have verified the validity of the EMTP simulation model by comparing simulation and experimental waveforms, and have shown the simulation of current and voltage waveforms in the event of a system fault by using the Japanese Power System Model as an application example of the EMTP simulation model.

Implementation of the universal line model in the alternative transients program✰