Alternative Transient Program-Electromagnetic Transient Program Research Articles

Design and Performance Analysis of a Subnanosecond Pulse Generator

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.

Spectral analysis of voltages and currents during different modes of ferroresonance in switchgear

This paper presents a spectral analysis of three different modes of ferroresonance. Voltage and current signals of the fundamental, subharmonic and chaotic ferroresonance modes are processed. The signals are obtained by modeling a ferroresonance circuit in alternative transient program-electro magnetic transient program (ATP-EMTP). The magnitude spectrum and total harmonic distortion are calculated for each case. The results show that voltages and currents of different modes of ferroresonance produce different features, which may be used for ferroresonance identification, classification and mitigation in the future.

Design, Implementation and Simulation of Non-Intrusive Sensor for On-Line Condition Monitoring of MV Electrical Components

Non-intrusive measurement technology is of great interest for the electrical utilities in order to avoid an interruption in the normal operation of the supply network during diagnostics measurements and inspections. Inductively coupled electromagnetic sensing provides a possibility of non-intrusive measurements for online condition monitoring of the electrical components in a Medium Voltage (MV) distribution network. This is accomplished by employing Partial Discharge (PD) activity monitoring, one of the successful methods to assess the working condition of MV components but often requires specialized equipment for carrying out the measurements. In this paper, Rogowski coil sensor is presented as a robust solution for non-intrusive measurements of PD signals. A high frequency prototype of Rogowski coil is designed in the laboratory. Step-by-step approach of constructing the sensor system is presented and performance of its components (coil head, damping component, integrator and data acquisition system) is evaluated using practical and simulated environments. Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP) is used to analyze the designed model of the Rogowski coil. Real and simulated models of the coil are used to investigate the behavior of Rogowski coil sensor at its different stages of development from a transducer coil to a complete measuring device. Both models are compared to evaluate their accuracy for PD applications. Due to simple design, flexible hardware, and low cost of Rogowski coil, it can be considered as an efficient current measuring device for integrated monitoring applications where a large number of sensors are required to develop an automated online condition monitoring system for a distribution network.

New model for overhead lossy multiconductor transmission lines

A new model for time-domain electromagnetic transient analysis of overhead multiconductor transmission lines with frequency-dependent electrical parameters is presented. The model is based on the method of characteristics, which has been used before by means of the application of finite difference schemes. Conversely to the regular method of characteristics, the model presented here does not require the spatial discretisation along the line. Also, the frequency dependence of the electrical parameters is included by means of a transient resistance matrix. To validate the model, the results are compared to those from a frequency-domain method, the alternative transients program/electromagnetic transients program (ATP/EMTP) and the electromagnetic transients program-restructured version (EMTP-RV).

Effect of Terminating Resistance on High Frequency Behaviour of Rogowski Coil for Transient Measurements

Partial Discharge (PD) current measurements have been widely used to assess the insulation condition of power components. Rogowski coil is a low cost current sensor specifically meant for high frequency transient diagnostics such as PDs in high voltage (HV) power apparatus. This paper presents the design of Rogowski coil for transient measurements. For the designed prototype of Rogowski coil, correct selection of terminating resistance is of high importance to calibrate its response for accurate measurement of the PD current waveforms. Effect of terminating resistance for the coil model is analysed based on theoretical, practical and simulated investigations. Simulated model of the coil is used to determine the behaviour of induced current through non-physical inductive and capacitive elements of Rogowski coil. The Electromagnetic Transient Program-Alternative Transient Program (EMTP-ATP) is used to implement and to analyze the model of Rogowski coil. The comparison of practical and simulated results validates the designed model of the coil. The paper explores EMTP-ATP as an efficient tool to analyze and modify the transient behaviour of Rogowski coil for high frequency pulse measurements.DOI: http://dx.doi.org/10.5755/j01.eee.19.7.2070

A novel discrete wavelet transform based on traveling wave technique for identifying the fault location for transmission network systems

AbstractThis paper proposes a technique to identify fault location on transmission systems using discrete wavelet transforms (DWTs). Fault conditions are simulated using alternative transients program/electromagnetic transients program (ATP/EMTP) in order to obtain the current signals. Various cases based on Thailand electricity transmission systems are studied to verify the validity of the proposed technique. The comparisons among the maximum coefficients in first scale of all buses that can detect fault are performed to detect the faulty bus. The first peak time of positive sequence current obtained from the faulty bus is used as input data for the traveling wave equation. It is shown that the proposed technique gives satisfactory accuracy and is suitable for all types of fault occurring in different sections of transmission lines. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Turn‐to‐earth fault modelling of power transformer based on symmetrical components

In this paper, a new approach to simulate transformer turn to earth fault, by using symmetrical components approach, has been presented. In the suggested novel modeling technique, the transformer turn to earth fault is simulated as a new healthy transformer with new short circuit (SC) impedance. This SC impedance is considered as the SC impedance of the transformer with the fraction part of the transformer winding through which the turn to earth fault occurs. The SC impedance of the reminder part of the transformer winding is added to the transmission line impedance or load impedance as external impedance. Hence, by using this suggested modelling technique, the system of turn to earth fault transformer is represented with a new system of a new healthy transformer, and the turn to earth fault is represented as an external line to ground fault. The values of the turn to earth fault current from this novel modelling technique (using the symmetrical components approach) were compared with those obtained by Electromagnetic Transient Program/Alternative Transient Program (EMTP/ATP). Finally, a suggestion method to estimate general information about the SC impedance of a three-phase three-winding transformer at different percentages of turn to earth fault is discussed.

Transient overvoltage phenomena on the control system of wind turbines due to lightning strike

This study proposes a simulation process for lightning protection. In addition, it analyzes and proposes lightning protection methods by simulating the effects of transient over-voltage on the control system that occur when lightning directly strikes a wind turbine. This study used Electro Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) to build a lightning model and a tower-control line model according to actual wind turbine structures and local lightning characteristics in Taoyuan, Taiwan. Various lightning strikes and ground resistances were simulated with consideration to whether the tower and the control system were individual or interconnected ground systems to observe transient phenomena in the control line. The transient over-voltage of the insulating layer and conductor of the control line, and the coupling voltage between the control line and the tower were analyzed based on three simulation cases to propose lightning protection methods that are applicable to Taoyuan. Consequently, an applicable lightning protection method for wind turbines was developed according to requirements of the different installation sites, and the lightning information and a decision maker were used to estimate the degree of protection. Specific proposals can be made using the method proposed in this study, avoiding waste in lightning protection.

A novel probabilistic neural network‐based algorithm for classifying internal fault in transformer windings

AbstractThe major function of protective devices in a power system is to detect the occurrence of faults and to isolate the faulty sections from the rest of the system. Much progress has been made in the development algorithms for detecting faults in power transformers, which depend on transients‐based techniques. This paper presents an algorithm based on a combination of discrete wavelet transforms and probabilistic neural networks (PNNs) for classifying internal faults in a two‐winding three‐phase transformer. Fault conditions of the transformer are simulated using alternative transients program/electromagnetic transients program (ATP/EMTP) in order to obtain current signals. The mother wavelet Daubechies4 is employed to decompose the high‐frequency components from these signals. All three phases of the differential current signals are used in the fault detection decision algorithm. The variations of first‐scale high‐frequency component that detects fault are used as an input for the training pattern. The training process for the neural network and fault diagnosis decision is implemented using toolboxes on MATLAB/Simulink. Various cases and fault types based on the Thailand electricity transmission and distribution systems are studied to verify the validity of the algorithm. Backpropagation neural network is also compared with the PNN in this paper. It is found that the proposed method gives satisfactory accuracy with less training time, and will be particularly useful in the development of a modern differential relay for a transformer protection scheme. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Multi-end correlation-based PD location technique for medium voltage covered-conductor lines

In Finland, overhead covered conductors (CC) are commonly used in the medium voltage (MV) networks because the distribution loads in rural areas are not heavy and are widely distributed in the forested terrain. Such parts of the network are exposed to leaning trees and therefore partial discharging into the overhead CC frequently occurs. In this paper, a multi-end correlation-based technique for locating partial discharge (PD) sources on CC lines is presented. The theory of maximum correlation factor is used in order to find the time differences between signal arrivals at three synchronized-measuring points. This helps to solve the problem of varying parameters of the CC line that can change the propagation velocity and the problem of identifying the arrival times of the corresponding PD pulses at different measuring points. The algorithm is developed and tested using a simulated study and experimentally verified using an alternating current (ac) energized system. The Electromagnetic Transient Program-Alternative Transient Program (EMTP-ATP) is used to implement and analyze a PD monitoring system. The Discrete Wavelet Transform (DWT) is used to de-noise PD signals measured from a Rogowski coil utilized as a high frequency transducer. The noise model is added to the simulated-power network signals and then a DWT-based de-noising process is carried out. The proposed algorithm performance is evaluated by extracting the high frequency features using a windowed-standard deviation. The simulated and experimental evaluations prove that accurate PD source location can be achieved using the proposed algorithm technique.

Dynamic modeling of a hybrid wind/solar/hydro microgrid in EMTP/ATP

Microgrids are LV or MV electric networks which utilize various distributed generators (DG) to serve local loads. In this paper, dynamic models of the main distributed generators including photovoltaic (PV) cell, wind turbine, hydro turbine as well as the equivalent power electronic interfaces, battery unit of PV and excitation system of hydro turbine have been made in ElectroMagnetic Transient Program/Alternative Transient Program (EMTP/ATP) software package. Control strategies based on active power/frequency and reactive power/voltage droops for the power control of the inverters have been also developed. Case studies have been carried out in a distribution network to investigate the dynamic behavior of the micro-sources in both steady state and fault scenarios. Simulation results verify the feasibility of the proposed models.

Lightning attachment models and maximum shielding failure current of overhead transmission lines: implications in insulation coordination of substations

The maximum shielding failure current of overhead transmission lines is an important parameter in evaluating the shielding performance of the lines and in insulation coordination of substations. General expressions for the estimation of the maximum shielding failure current of transmission lines, derived by employing several lightning attachment models in shielding analysis, are presented. An application to typical 110 kV up to 1150 kV overhead transmission lines shows that there is a great variability in maximum shielding failure current among lightning attachment models. The importance of maximum shielding failure current in insulation coordination of substations is demonstrated with the aid of alternative transients program-electromagnetic transients program (ATP-EMTP) simulations. The computed overvoltages impinging on 150 and 400 kV gas insulated system (GIS) substations because of shielding failure of the incoming overhead transmission lines, being dependent upon shielding failure current, vary with the lightning attachment model employed in shielding analysis of the lines. Implementation of the electrogeometric model adopted by IEEE Std 1243:1997 in shielding analysis imposes high requirements on protection of the substations against incoming shielding failure surges.

Power-Line Communication Channel Model for Interconnected Networks—Part I: Two-Conductor System

This paper presents a generalized transmission-line approach to determine the transfer function of a power-line network of a two-conductor system (two parallel conductors) with distributed branches. The channel frequency responses are derived considering different terminal loads and branches. The model's time-domain behavior is validated using commercial power system simulation software called Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP). The simulation results from the model for three different topologies considered have excellent agreement with corresponding ATP-EMTP results. Hence, the model can be considered as a tool to characterize any given power-line channel topology that involves the two-conductor system. In the companion paper (Part II), the proposed method is extended for a multiconductor power-line system.

Channel Model for Broadband Power-Line Communication

This paper presents a novel approach to model the transfer function of a power-line network. The channel frequency responses of a single-phase power-line channel with interconnections are derived considering different loading at different branches. The model is verified using Alternative Transients Program-Electromagnetic Transients Program (ATP-EMTP). The model simulation results are comparable to ATP-EMTP results. Therefore, the modeling can be considered as a procedure to characterize the power-line channel

A Novel Digital Directional Transformer Protection Technique Based on Wavelet Packet

This paper presents a novel digital technique for transformer protection. The technique is based on deriving a directional quantity proportional to the fault current signal and the prefault voltage signal. Standard fast wavelet transform (FWT) schemes may not be as effective for data that has chiefly oscillatory features. An effective solution to discrimination involves examining the signal in both the time and frequency domains simultaneously. The wavelet packet transform is an extension of the FWT that allows for finer characterization of signal content for both time and frequency together. A 11/132-kV transformer connected to a 132-kV power system was simulated using Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP). Results indicate that the proposed technique is stable, reliable, and fast during the discrimination between internal and external faults, magnetizing inrush currents, and internal faults, ratio-mismatch, and saturation of current transformers (CTs).

Interaction of electromagnetic fields from cloud and ground lightning flashes with an artificial low-voltage power installation

In most of the studies dealing with electromagnetic field interaction between nearby lightning flashes and electrical installations, the cloud flashes are assumed to play an insignificant role. However, our studies show that cloud flashes can generate induced voltages with amplitudes comparable to those of ground flashes when the electrical installation has a limited size or length and the lightning flash is a few tens of kilometers away. Furthermore, the voltages generated by cloud flashes have much shorter risetimes and pulse widths than those of ground flashes. This paper presents the results of a study conducted to investigate the coupling mechanism between lightning electromagnetic fields from both cloud and ground flashes and an artificial low-voltage power installation (LVPI). In the experiment, a Y-shaped artificial LVPI was constructed and exposed to lightning-electromagnetic fields. In the experiment, both the vertical electric field and the induced voltage in the LVPI were measured simultaneously. The analysis was conducted in the time domain by using the Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP) and the horizontal electric field at the installation was calculated by applying the concept of wavetilt to the measured vertical electric field. A reasonable agreement between the measured and simulated induced voltages was found. However, the results given in this study might not be true for longer structures such as power distribution lines and close lightning flashes.

Transient modeling of electromechanical relays

An electromechanical, plunger type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the Type 50 devices and incorporating them into a power system transient analysis. This paper is the second part of a summary report by Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration. (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for plunger type 50 instantaneous overcurrent relays that compare with actual tests performed on the devices on a power system simulator.

Transient modeling of electromechanical relays. Part I: armature type overcurrent relay

An electromechanical, armature type 50 relay is modelled in EMTP/ATP using TACS. Mechanical, magnetic, and electrical characteristics are represented in the form of simple mathematical models that can provide a useful tool for studying the dynamic responses of the armature type 50 devices and incorporating them into a power system transient analysis. This paper is the first part of a summary report by the Rensselaer Polytechnic Institute (RPI) of work on relay modeling sponsored by the Bonneville Power Administration (BPA). It presents the Electro-Magnetic Transient Program/Alternative Transient Program (EMTP/ATP) model for armature type 50 instantaneous overcurrent relays that compares with actual tests performed on the devices on a power system simulator (PSS).