The hysteresis loop of the core material in a test current transformer is simulated using the Jiles-Atherton theory. Comparisons are made between recorded and simulated waveforms and it is found necessary to replace the modified Langevin function used by Jiles and Atherton. Using an alternative function described in the paper, good agreement is achieved between test and simulated waveforms.

A current transformer model based on the Jiles-Atherton theory of ferromagnetic hysteresis

Throughout the history of power system protection, researchers have strived to increase sensitivity and speed of apparatus protection systems without compromising security. With the significant technological advances in wide-area measurement systems, for transmission system protection, current differential protection scheme outscores alternatives like overcurrent and distance protection schemes. Therefore, in this paper, we address this challenge by proposing a methodology for adaptive control of the restraining region in a current differential plane. First an error analysis of conventional phasor approach for current differential protection is provided using the concept of dynamic phasor. Subsequently, we extend the methodology for protection of series compensated transmission lines. Finally, we also evaluate the speed versus accuracy conflict using phasorlets. Electromagnetic Transient Program simulations are used to substantiate the claims. The results demonstrate the utility of the proposed approach.

Adaptive Current Differential Protection Schemes for Transmission-Line Protection

Transformer modeling for transient simulations has many challenges because of nonlinear and frequency-dependent behavior. Some of the model parameters are relatively easy to obtain from standard factory tests. Other parameters can only be obtained from special tests or by estimation. This paper provides guidelines for the estimation of transformer model parameters for low- and mid-frequency transient simulations. The paper also discusses several transformer models that can be used for transient simulation.

Parameter determination for modeling system transients-Part III: Transformers

Overhead line parameters are calculated, taking into account the length of the line and the frequency range of the transient to be simulated. Depending on the frequency range and the origin of the transient, several parts of the line (phase conductors, shield wires, towers or poles, footing impedances, insulators) have to be included in the model. In all cases, the most important part is phase conductors. This paper describes an input requirement for obtaining electric overhead line parameters and investigates the sensitivity of these parameters with respect to some input data. The aim is to conclude on the accuracy with which input values must be specified. An illustrative example is included to support the main conclusions.

Parameter determination for modeling system transients-Part I: overhead lines

This paper presents a novel time-domain fault location algorithm for parallel transmission lines using two terminal currents. Parallel transmission lines with faults can be decoupled into the common component net and differential component net. Since the differential component net is only composed of the parallel lines and its terminal voltages equal zero, the proposed algorithm is based on the fact that the difference between voltage distributions, calculated from two terminal currents, is the smallest at fault point. To be practical, unsynchronized data and the transient transferring ability of the current transformer are taken into consideration. The algorithm needs a very short data window, and any segment of current data can be used to locate faults. The proposed algorithm is verified successfully using the simulation data generated by the frequency-dependent line model of the Alternative Transients Program and the field recording data provided by traveling-wave fault locators. Locating results show the satisfactory accuracy of the algorithm for various fault types, fault distances, and fault resistances.

Parallel transmission lines fault location algorithm based on differential component net

This paper reviews a number of mathematical models used to represent the nonlinear behavior of the magnetic core of instrument transformers. Models of instrument transformers using these core representations are presented. The transient response of the instrument transformer is compared to actual test results recorded in the laboratory. The paper provides practical guidelines as to which of the physical elements of instrument transformers are important to model during transient studies and which elements could be ignored without sacrificing the accuracy of the simulation results. The electromagnetic transients program (EMTP) data files used to generate the models are also provided in the appendix to help new EMTP users model instrument transformers for evaluation of high-speed protective relaying systems.

http://smartgridcenter.tamu.edu/resume/pdf/per/Mathematical%20models%20for%20current,%20voltage,%20and%20coupling%20capacitor%20voltage%20transformers.pdf

Mathematical models for current, voltage, and coupling capacitor voltage transformers

G. Swift comments on the paper by Working Group C-5 of the Systems Protection Subcommittee of the IEEE Power System Relaying Committee (see ibid., vol.15, no.1, 2000). The author points out an error in the article. The Working Group reply to the comments.

M. Glinkowski

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Mathematical models for current, voltage, and coupling capacitor voltage transformers

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