Apparent Impedance Research Articles

A new on-line technique to identify fault location within long transmission lines

Identification of fault location within transmission lines is essential in order to restore service rapidly, reduce unplanned outage time, minimise revenue loss, and improve network reliability. Several transmission line fault-locating techniques based on travelling waves, apparent impedance and direct circuit analysis have been introduced in the literatures. However, these methods are either impractical or too expensive to implement. In this paper, a new online technique is introduced to accurately detect the fault location within transmission lines. The technique relies on constructing a voltage-current (V-I) locus diagram that could be measured at every power frequency cycle to provide up-to-date condition state of the line. The technique does not call for special equipment as it utilises the existing metering or protection devices connected to the sending and receiving ends of the transmission line to monitor the voltage and current at both ends. To assess the robustness of the proposed technique, various types of faults have been simulated on transmission lines of various lengths and voltage levels using DIgSILENT PowerFactory software. Variations in load conditions, effect of fault resistance, different line configurations are also investigated. Results reveal the ability of the proposed technique to detect fault locations in transmission lines with high accuracy. In contrary with existing fault-locating techniques that are only employed to identify the location of faults after their occurrence, the proposed technique has the potential to detect high impedance faults. Thus an early warning signal can be issued to avoid any catastrophic consequences. The proposed technique is cost effective and easy to implement for new and existing transmission line installations.

A faulted side identification scheme-based integrated distance protection for series-compensated transmission lines

This paper introduces an integrated distance protection technique for series-compensated transmission lines (SCTLs) based on a new scheme to identify the faulty side with respect to the compensator. Conventional distance algorithms suffer from mal-operation under faults behind the Series Compensator (SC). Therefore, the modified mathematical algorithm of the distance relay treats with these faults via compensating the voltage drop through the SC to integrate the relay performance along the line. Consequently, the faulty side either upstream or downstream the SC must be identified. This identification is accomplished via a new function inserted in the mathematical algorithm. The presented function is a voting system based on both of the angles of the obtained conventional and modified apparent impedances. The presented voting scheme is based on basics theories of the fault analysis and the phasors diagrams of the equivalent apparent impedances seen by the conventional and modified algorithms whether the fault is upstream or downstream the SC. The presented scheme is suitable for all fault types even with high fault resistances. MATLAB package is used to simulate 400 kV compensated transmission lines and also to implement the presented algorithm. Diverse fault cases are investigated to test the response of the presented voting system under different fault conditions including the fault type, location, and impedance. The results confirm the efficacy of the presented scheme.

IMPACT OF REAL AND REACTIVE POWER CONTROLLABILITY OF STATCOM ON TRANSMISSION LINE PROTECTION

Static synchronous Compensator (STATCOM) is a shunt connected Voltage Source Converter (VSC) based FACTS controller which is useful in improving the voltage regulation. VSC based FACTS controllers facilitate connection of energy storage devices like battery, fuel cell, Super Magnetic Energy Storage(SMES) etc. at the DC bus. Addition of energy storage device results in better real and reactive power flow control, transient stability enhancement and power oscillation damping. However, FACTS controllers with energy storage device in the line poses new challenges for the line protection device. Operating region of STATCOM with energy storage device (STATCOM – ES) encompasses all the four quadrants in P – Q plane. Impedance contribution by STATCOM operating in any of these four quadrants can modify apparent impedance seen by distance relay and hence needs to be investigated thoroughly. Main aim of this paper is to analyze the impact of emulated conductance and susceptance by four quadrant operation of STATCOM on the performance of distance relay in a hybrid compensated system. A novel control strategy to dynamically modify the reference for real power exchange by STATCOM is proposed to avoid damage to the STATCOM during fault. Possibilities of distance relay under reach and over reach due to operation of STATCOM - ES in various operating modes and impact of fault resistance on the relay performance is discussed.

Analysis and Design of a Doherty-Like RF-Input Load Modulated Balanced Amplifier

This paper presents an analysis and design technique for an RF-input load modulated balanced amplifier (LMBA) with Doherty-like efficiency enhancement characteristics. The LMBA is a recently introduced power amplifier (PA) architecture in which a control signal is injected into the isolation port of the output coupler of a balanced amplifier. This control signal modulates the apparent load impedance of the two main devices. In the RF-input LMBA presented in this paper, the control signal is generated from the single-modulated RF input using a class-C control amplifier, producing an overall Doherty-like response. A complete theoretical analysis of the RF-input LMBA is presented, by assuming generalized networks for the output combiner and input splitter which are then solved in terms of transistor parameters and boundary conditions for high efficiency. Based on this analysis, a generalized design technique is presented. The LMBA is, thereby, shown to have advantages over the Doherty PA, including the device periphery scaling between the main and control devices for a given back-off range. The design technique is demonstrated at 2.4 GHz using packaged GaN devices. The prototype has a peak CW output power of 45.6 dBm, with a power-added efficiency of 60% at peak power and 50% at 6-dB output back-off, including the power dissipated by the control PA. A long-term evolution signal at 2.4 GHz with a 7.5-dB peak-to-average power ratio is demonstrated with an unlinearized ACLR of −27 dBc and an average drain efficiency of 47% for a 38-dBm average output power.

Magnetotelluric transfer function distortion assessment using Nyquist diagrams

Magnetotelluric (MT) inversion is using impedance data as input data, which is traditionally presented via the apparent resistivity and impedance phase. Since high-quality MT data are necessary to improve the reliability of inversion results, the distortions in the curves should be assessed and removed. Usually, this smoothing procedure acts individually on the apparent resistivity and phase and does not consider the dispersion relationship between the real and imaginary parts of the impedance. Therefore, how to assess the distortion while retaining the inherent relationship in the impedance should be addressed. In this study, Nyquist diagrams were used as a tool to illustrate the inherent feature of the MT complex response. The MT impedances of 2-D and 3-D models were computed and illustrated in the corresponding diagrams. From these curves, we found that the Nyquist curves or part of them are continuous and smooth. When the model is 1-D or 2-D, Zxy and Zyx try to stretch around a line at a 45° slope, whereas in the 3-D case, the Nyquist diagrams of the full impedance elements rotate clockwise from low to high frequencies. If the frequency is high or low enough, the curves of Zxx and Zyy become approximate ellipses. The phases of Zxx and Zyy are also out of scope (−π,π), which is beyond the traditional knowledge of the phase, which making data distortion removal in the phase confusing. Cole-Cole model could be used to explain above features. And these features behind the Nyquist diagrams could be used as tools to guide the distortion removal in the MT complex response in the field. When MT impedance data are not severely distorted, it is possible to recover high-quality data when obeying the following two rules: (1) both the amplitude and phase should be smooth and (2) the Nyquist curve of the complex response should also be smooth or at least smooth in segments.

Geoelectric studies of the oil and gas bearing area on the southern slope of the central Dnieper-Donets Basin part

In 2017 modern synchronous magnetotelluric and magnetovariational investigations were carried out on the Nesseno-Irzhuets—Abramovka profiles in eleven points for the study of the deep structure of the central part of the southern Dnipro-Donets Basin (DDB) board, where the Kirovograd electrical conduction anomaly crosses the Lokhvytsky and Poltava blocks of the DDB. The processing of experimental materials was carried out using known programs PRC_MTMV and PTS. Reliable estimates of the types for periods of geomagnetic variations from 30 to 3700 s and parameters of apparent electrical resistance (amplitude values and phase of impedance) from 40 to 10 000 s are obtained. A joint analysis of complex types and curves of apparent electrical resistance and impedance phases indicates the presence of a surface conductor. Which extends from northwest to southeast and associated with superficial conductivity of the sedimentary strata of the DDB. Also spatially detailed heterogeneity, which is assumed in deep horizons with an upper edge of 20—30 km in the middle part of the profile and corresponds to Kirovograd electrical conduction anomaly. The qualitative interpretation of experimental MT/MV data allows us to clarify the perspective on the oil and gas bearing area in the area of the southern side, which outlines the central part of the DDB between the settlements of Khorol and Reshetilivka. In addition, confirm and detail previously allocated oil and gas prospecting sites, namely Glydinintsiv, with which the anomaly is connected in its southeastern part and extend to the southeast by 20 km. Information about the existence of a deep conductor and its parameters should be the basis for quantitative interpretation and construction of 3D deep geoelectric model.

Modeling for Development of Simulation Tool: Impact of TCSC on Apparent Impedance Seen by Distance Relay

The impact of thyristor controlled series capacitor (TCSC) on distance protection relays in transmission lines is analyzed in this paper. Voltage and current data are measured and collected at the relay locations to calculate the apparent impedance seen by distance protection relays in the different operating modes of the TCSC connected to the line. Short-circuit faults which occur at different locations on the power transmission line are considered in order to locate the fault for the purpose of evaluating the impact of TCSC on the distance protection relay. Matlab/Simulink simulation software is used to model the power transmission line with two sources at the two ends. Voltage source, transmission line, TCSC, voltage and current measurement, and discrete Fourier transform (DFT) blocks are integrated into the model. Simulation results show the impact of TCSC on the distance protection relay and determine the apparent impedance and fault location in the line.

Modeling for Development of Simulation Tool: Impact of TCSC on Apparent Impedance Seen by Distance Relay

Modeling for Development of Simulation Tool: Impact of TCSC on Apparent Impedance Seen by Distance Relay

A Discrete Wavelet Transform based STATCOM Compensated Transmission Line

This paper describes the Discrete Wavelet transform (DWT) applied for classification and detection of fault with respect to the position of the Static Synchronous Compensator (STATCOM). STATCOM is positioned at mid-point of the transmission line. The reactive power injection or absorption (i.e shifting phase voltage with respect to bus voltage) depends upon the apparent impedance during the fault. The current signals of each phase are retrieved from both sending and receiving end of three phase transmission line synchronously. It starts processing through DWT to acquire spectral energy (SE) content of each phase current signals from both end of the transmission line. Differential spectral energy (DSE) of each phase current signals (i.e SE of current signal recovered from sending end minus SE of current signal recovered at receiving end) of transmission lines is used to record the fault configuration.

Tensor CSAMT and AMT Studies of the Xiarihamu Ni-Cu Sulfide Deposit in Qinghai, China

The frequency domain electromagnetic sounding method is one of the important means of exploring mineral resources. This paper combined tensor controlled source audio frequency magnetotelluric (CSAMT) and audio frequency magnetotelluric(AMT) methods to investigate Xiarihamu copper‑nickel ore in Qinghai Province. Spliced tensor CSAMT high frequency (200 Hz–8533 Hz) and AMT low frequency (1 Hz–200 Hz) apparent resistivity and impedance phase data, as well as spliced data, were used for a 2D inversion and to generate a 2D geoelectric model. Coupled with the known geological, geophysical, and drilling data, the inversion results were analyzed. The results show that the combined use of tensor CSAMT and AMT can overcome the inherent defects of these methods, such as limited exploration depth and the “dead band” effect. This method produced good results in terms of exploring the underground electrical structure, finding the low resistivity body, and determining the thickness of the overburden, as well as the occurrence and the buried depth of the ore body. These results provide an effective method and exploration strategy to find similar potential deposits in the surrounding areas.

Locating Fault on Transmission Line with Static Var Compensator Based on Phasor Measurement Unit

The flexible alternating current transmission systems (FACTS) have been widely used in modern power systems. Because of the presence of the FACTS devices, distance relays in transmission lines may inaccurately locate fault locations. Therefore, it is significant to find a mechanism for locating fault in transmission lines connected to FACTS in which a static var compensator (SVC) is investigated in this work. Based on the development of a phasor measurement unit (PMU) with global positioning system (GPS), this paper proposes a new method for calculating apparent impedance seen by the distance relay location while a short-circuit fault occurs in a transmission line connected the SVC to the midpoint of the line. According to the method, sampled voltage and current measurement at the relay and SVC locations are synchronized using PMUs and the synchronized measurements are then used to calculate a new apparent impedance and to locate the fault location in the line. The method in this paper has the capability for fast calculation and it also has the robustness for identifying different fault types in power systems. Matlab/Simulink software is applied to simulate the study results and to evaluate the correctness of the modeling and effectiveness of the proposed method for locating fault in this paper.

Mapping of buried faults using the 2D modelling of far-field controlled source radiomagnetotelluric data

Controlled source radiomagnetotellurics (CSRMT) is a relatively new geophysical method for near-surface applications. A rectangular signal with base frequencies between 0.1 and 150 kHz is injected through a grounded electric dipole which is used as a transmitter. Electric and magnetic field components are observed at these frequencies and at their subharmonics, usually in the far-field zone so that apparent resistivities and impedance phases can be obtained in a broad frequency range between 1 and 1000 kHz. Inline or broadside configuration can be used for measurements. Similar to the controlled source audiomagnetotelluric method, tensor measurements are also possible when locating two transmitters perpendicular to each other. A scalar CSRMT survey was carried out on the buried faults in the Vuoksa region, 110 km north of St. Petersburg to test the applicability of this method to the mapping of near-surface faults. A 700 m electric dipole with base frequencies of 0.5, 11.3, 30 and 105 kHz was used as a transmitter. Smooth apparent resistivity and phase values as a function of frequency from 1 kHz to 1 MHz were observed in the far-field zone for the inline configuration at 57 stations using a station distance of 20 m. Electric fields observed in the direction of the transmitter were perpendicular to the assumed strike direction of the buried faults so that they could be associated with the TM mode. The observed apparent resistivity and phase TM mode data were interpreted using the 2D inversion algorithm, and a good data fitting could be obtained. The resistivity structure beneath the survey area (down to a depth of 80 m) could be derived and the buried faults could be mapped successfully. In addition to the CSRMT observations, a conventional radiomagnetotelluric (RMT) survey was also carried out on the same profile. An excellent correlation of the observed RMT and CSRMT transfer functions and 2D conductivity models was achieved.

Faulted Branch Location in Distribution Networks Based on the Analysis of High- Frequency Transients

Electric Power Distribution Systems (EPDS) are steadily growing in both size and complexity, and thereby faults on distribution feeders tend to affect more customers and take more time to be located and fixed. Hence, fast and accurate fault location is of primordial importance in minimizing the economic loses for both customers and utilities. Some methods such as those based on the apparent impedance analysis are able to accurately identify the fault distance from the local terminal. However, as the distribution systems have multiple branches and monitoring infrastructure is usually limited to the substation, the location of the faulted branch is a problem not solved yet. This paper proposes the transient analysis of the fault-generated traveling wave in order to identify the faulted branch of radial distribution feeders. The method is based on the correlation of theoretical frequencies calculated for each wave propagation path and characteristic frequencies inferred from the transient spectrum. A frequency-dependent modal transformation matrix is formulated by modifying the Carson's equations thus allowing to accurately model the propagation of high-frequency transients in unbalanced distribution networks. Aiming to verify the performance of the proposed methodology, simulations were carried out considering several fault scenarios in the IEEE 13 nodes distribution system.

Impedance Control Using a Cascaded Loop Force Control

In this letter, a cascaded loop force control is implemented on a robot while considering the flexibility of the force sensor connecting the end effector to the tool. A classical frequency approach using a bandwidth and a phase margin is used to tune this controller. The aim is to find an equivalence between the proposed control law and a classical impedance control law. The apparent impedance of this system is calculated and can be seen as the desired impedance for a classical impedance control law. Using this equivalence, the cascaded loop force controller can be tuned to an impedance controller, and can be shown to behave equivalently in simulations and experiments on a one degree of freedom robot.

Effect Evaluation of Fault Resistance on the Operating Behavior of a Distance Relay

This paper presents an application of a certain distance protection relay with a quadrilateral characteristic approach for the protection of the 110kV Duy Xuyen - Thang Binh transmission line in Vietnam using measured data from one terminal line. We propose the building process of a Matlab Simulink model for this relay that combines fault detection and classification block, apparent impedance calculation block for all types of faults and a trip logic block of three zone protection coordination. The proposed relay model is further tested using various fault scenarios on the transmission line. It is important to assess what happened, the actual conditions, the causes of mal-operation etc. Detailed explanation and results indicate that the proposed model behavior will help users to perform tests which correctly simulate real-world conditions besides that it properly interprets test results and troubleshoot distance function problems when results are not as expected.

Possible mechanisms of co-seismic electromagnetic effect

We analyze theoretically two possible sources of co-seismic electromagnetic response to the propagation of various types of seismic waves caused either by the electrokinetic phenomena or geomagnetic inductive effect. The differences between these two generation mechanisms have been examined for different types of seismic waves (P, S, and Rayleigh-Love). Theoretical relationships describing the dependence of the co-seismic signal amplitude, polarization and apparent impedance on the earthquake seismic moment and magnitude have been derived as a function of distance. We indicate an observational possibility to discriminate seismo-electrokinetic and seismo-magnetic effects and to estimate their contribution into a recorded co-seismic electromagnetic signal. Magnitudes and polarization of these signals are shown to depend strongly on the type of seismic wave and local crust parameters, such as streaming potential coupling coefficient, conductivity, inhomogeneity, etc. Co-seismic electromagnetic signals, though not directly applied for earthquake prediction, contain a useful information on local crustal phenomena, and can be used to identify “sensitive” zones perspective for the monitoring of precursory electromagnetic disturbances.

Effect of an additional large disturbance during power swings on the impedance seen by the out-of-step blocking function

This short article analyzes the effect of an additional large disturbance during power swings on the apparent impedances seen by the out-of-step blocking function of a distance relay. An additional large disturbance during power swings can imply a sudden change of the apparent impedance, which should be considered for the setting of out-of-step functions. The goal of this article is to describe this phenomenon, which has not been previously shown in the literature. A Venezuelan case is taken as an example, and the analyzed additional large disturbance is due to the operation of a special protective scheme for the islanding of one specific area. Maximization of the region between concentric characteristics and minimization of correspondent setting time can be useful actions to improve the expected behavior of out-of-step blocking functions. However, these actions are insufficient for the analyzed example, and two non-traditional solutions were proposed. In general, as these additional large disturbances could fortuitously occur when the apparent impedance is near of the trip region, the logical proper solution should be provided by future improvements of the algorithms from relay manufacturers.

An Impedance-Based Method for Distribution System Monitoring

This paper presents a new approach in monitoring of a power distribution system. It uses the bus voltage and injected current to extract the apparent impedance seen from the measuring unit location. Then the apparent impedance variation is used for the monitoring of different electrical quantities of the feeder such as feeder power factor, and the minimum and maximum of active and reactive power flow. This paper also presents the mathematics for defining the monitoring zone on the R-X plane to detect those parameters variations. The proposed method was tested with the unbalanced distribution system feeder loading, distributed and lumped model of solar, and wind power generations. OpenDSS and MATLAB are used to test the effectiveness of the method with the IEEE 8500 node test feeder. The dynamic performance of the proposed method is studied for online monitoring of the reactive power capability requirement of a Canadian utility for a wind farm integrated to the system. The results show that the monitoring method based on the apparent impedance has a good capability to detect different operation conditions. In addition, the simplicity of the proposed method allows easy application of it in smart grid and traditional distribution system.

A DWT Based Differential Relaying STATCOM Integrated Wind Fed Transmission Line

This paper presents the differential scheme of relaying protection of transmission line in a Static Synchronous Compensator (STATCOM) integrated wind fed single circuit line. The Discrete Wavelet Transform (DWT) and Discrete Fourier Transform (DFT) technique are applied for classification and detection of fault in STATCOM including wind farm. The STATCOM is positioned at central point of the transmission line and wind farm is connected at receiving end of the transmission line. The reactive power injection or absorption (i.e, shifting phase voltage with respect to bus voltage) depends upon the apparent impedance during the fault. The individual fault current signal (i.e, A, B and C) of three phase is extracted at both end of sending and receiving side of single circuit transmission line synchronously. It starts processing with the DWT and DFT to find the spectral energy content of each phase current signals at both end of transmission line. The Differential Spectral Energy(DSE) of current signals (i.e spectral energy of current measured at sending end minus spectral energy of current measured at receiving end) of each phase of transmission lines is used to register the fault pattern. This scheme is very accurate, effective and simple for fault classification and detection of transmission line.

Apparent Impedance Analysis: A Small-Signal Method for Stability Analysis of Power Electronic-Based Systems

In this paper, a new method for power system stability analysis is introduced. The method is based on injection of a small voltage or current in an arbitrary point of a power system. The apparent impedance is then defined as the ratio between the voltage and current at the injection point. It is shown that the apparent impedance can be used to estimate the eigenvalues of the system that are observable from the injection point. The eigenvalues are obtained by applying system identification techniques to the measured set of apparent impedances. The method is similar to the well-established impedance-based stability analysis based on source and load impedance models. However, while the source/load impedance ratio is viewed as the minor-loop gain, the apparent impedance can be viewed as a closed-loop transfer function. It can also be expressed as the parallel connection of the source and load impedance. It is shown, in this paper, how the system eigenvalues can be extracted based on a set of apparent impedance values. The apparent impedance holds, therefore, complementary information compared with the existing impedance-based stability analysis. The method can also be used as a tool to validate analytically derived state-space models. In this paper, the method is presented as a simulation tool, while further work will extend it to include experimental setups. Two case studies are presented to illustrate the method: 1) a dc case with a buck converter feeding a constant power load and 2) a three-phase grid-connected voltage source converter with a current controller and a phase lock loop. The estimated (apparent) eigenvalues of the studied systems are equal to those obtained from the analytic state-space model.