• Energy Research
• 2021-2025close

Abstract In this paper, the effects of stray capacitances that may appear on the coupling capacitor voltage transformer (CCVT) during field operation are addressed. Those stray capacitances are usually ignored in the existing limited frequency bandwidth CCVT digital models reported in the literature. A sensitivity analysis is carried out to evaluate how the equipment magnitude and phase frequency responses can be affected when such capacitances are taken into account. Besides, the feasibility of classical CCVT transient response compensators is analyzed in these scenarios. The impact of these features is investigated on the performance of one- and two-ended traveling wave (TW)-based fault location techniques. The obtained results attest that the presence of the stray capacitances improve the performance of two-ended TW-based fault locators, but the classical CCVT compensator may not accurately reproduce the voltage TWs.

Abstract This paper presents a steady-state electromagnetic interference study between a 500 kV overhead transmission line and a neighboring pipeline, based on data from a real project with a complex geometry and with emphasis on how the soil structure affects the inductive coupling mechanism, as well as the effectivity of grounding devices to reduce potentially hazardous pipeline induced voltages. Soil parameters are determined from actual field measurements, which results in a soil model composed of three layers. Conductor impedances are computed using a modification of the original Carson equation, in which the term describing the soil resistivity is replaced by an equivalent uniform of the multilayered structure, and then a circuit model is built using the Alternative Transients Program (ATP) to predict the resulting induced voltages. Results show an excellent agreement between the proposed approach and the reference values, with a comprehensible evaluation of the risks to which the interfered pipeline is exposed and how to mitigate them.

This paper highlights the evolution of wind power sources in the modern energy scenario, emphasizing the impacts of inverter-based generators, namely Full-Converter and DFIG (Doubly-Fed Induction Generator), on fault currents and fault voltages in transmission systems. The studies were carried out through computer simulations, with an EMTP (Electromagnetic Transients Program) type software. A power system with high penetration of such renewable generations was modeled and several contingency scenarios were simulated in a transmission line that performs the connection of the wind power plant to the grid. The scenarios included the variation of parameters such as fault type, inception instant angles, resistance, and distance, to explore the main differences between the contributions to the fault of a wind power plant and conventional generation. Among the atypical analyzed characteristics, the following can be highlighted: the absence of the DC (Direct Current) component for Full-Converter generation, independent of fault inception instant angle and distance variation; low levels of the fault contributions at the wind power plant terminal; low levels of voltages at the wind power plant terminal, evidencing the high SIR (Source Impedance Ratio) characteristic of these generations; atypical relations between the fault resistance and measured currents; and others. The obtained results show the importance of further studies on the impacts of inverter-based generations on fault currents and voltages, allowing developments that are able to improve control and protection systems for grids with high penetration of this wind generation topologies

Abstract This paper presents a new time domain busbar protection algorithm which uses current samples and their half-cycle incremental quantities to implement a fast and reliable tripping logic. The sign of incremental quantities is used to determine the fault direction and to distinguish internal from external busbar faults. Also, a differential incremental current is calculated for properly selecting the circuit breakers that must be opened to clear the fault. In order to test the proposed technique, a double-bus single-breaker busbar configuration was modeled in ATP/ATPDraw software and several types of internal, external and evolving faults are simulated. The results reveal the proposed function quickly operates for internal faults and ensures security for external faults. Moreover, the proposed approach allows a fast detection of internal faults during an external fault. Hence, although the proposed function is based on well-known fundamentals, it achieves the principal requirements for a busbar protection scheme with a high degree of adaptability and reliability for severe cases.

Abstract An improved single-ended traveling wave (TW)-based fault location technique is proposed in this paper. It uses a correlation function to estimate the time delay between the fault-induced incident and reflected signals. Different from other classical one-ended correlation-based TW fault locators, the proposed algorithm does not depend on pre-classification of the fault type and it is not affected by low frequencies that may show up in the correlation function output. Besides, it needs only the first incident surge to be detected at the monitored bus by any TW-based detection method. Its validation is carried out through comparisons with the performance of one-terminal TW-based fault location approaches reported in the literature. The obtained results attest that the proposed technique is reliable and suitable to be used in fault location applications.

Abstract Commutation failure (CF) is an inherent issue for Line-Commutated Converter (LCC) HVDC technology. Whenever it happens, voltage and current waveforms throughout the AC system in the near vicinity of LCC-HVDC links become quite distorted. In this paper, it is assessed the impact of such kind of distortion on transient response of phasor estimation algorithms and, in turn, on the performance of AC transmission lines protection. Different discrete Fourier transform (DFT) based algorithms are implemented, and distance, differential and directional protection functions are evaluated. The obtained results reveal that phasor estimation errors arise whenever CFs take place, which may lead protection functions to misoperate, such that false trip command may be issued for external faults.

Abstract This paper analyzes the impacts of different transmission line (TL) modeling approaches in Electromagnetic Transients Programs (EMTP) during the evaluation of traveling wave (TW)-based fault location (TWFL) functions. Massive EMTP fault simulations are carried out to compare the performance of TWFL solutions when the system model considers Bergeron or JMarti models, accounting for homogeneous or heterogeneous soil characteristics, as well as ideal or real transposition schemes. Firstly, TWFL errors are presented in the form of scatter plots to compare the relative performance between four fault location solutions when different modeling approaches are taken into account. Then, the fault location absolute errors are presented as boxplots individually for each analyzed TWFL method and modeling approach, allowing to perform quantitative analysis of the obtained errors. From these results, the impacts of the evaluated modeling strategies on the assessed TWFL methods are addressed, highlighting the model features that can yield more challenging scenarios during the evaluation of TWFL solutions.