Nonhomogeneous Lines Research Articles

Synthesis of Bandpass Filter as a Four-Pole Based on a Non-Homogeneous Line

Synthesis of Bandpass Filter as a Four-Pole Based on a Non-Homogeneous Line

A new unsynchronized fault location approach based on sequence voltage profiles and a multiconductor line detailed model: Application to symmetrical transmission lines

This paper presents a new, improved approach to fault location in long and very long transmission lines, which uses measurements at both terminals of the line that do not need to be synchronized, using the satellite time-reference. The new method employs symmetrical component sequence voltage profiles that are computed using an innovative approach in which the detailed three-phase model of a multiconductor transmission line is represented as the series connection of several chain matrices. This allows the new method achieve the best performance, when compared to other 4 similar fault location approaches, requiring measurements at both terminals of a symmetrical line, considering all types of faults, under realistic variations in variables and parameters of the test system, including the effect of saturation of current transformers, and arc faults. The main advantage of this proposed technique is that it can be applied with no major changes in symmetrical and unsymmetrical transmission lines keeping its good performance. In addition, division of the line in chain matrices allows the new proposed approach to be applied in non-homogeneous lines. In this paper, for space reasons, the new approach is initially applied to symmetrical (ideally transposed) transmission lines only, with very successful and encouraging results.

Fault location for general AC/DC transmission lines: Multi-phase, non-homogeneous, partially mutually coupled and multi-terminal lines

The complexity of a general AC/DC transmission line is mainly caused by the components such as multi-phase line, non-homogeneous line, partially mutually coupled line and multi-terminal line. This paper proposes a systematic methodology to accurately locate faults in a general complex AC/DC transmission line. Instantaneous measurements only at line terminals are required. First, the modeling methodologies of symmetrical/asymmetrical multi-phase line, non-homogeneous (including partially mutually coupled) line and multi-terminal line are proposed. The distributed parameter line model is fully considered with partial differential equations (PDEs) in time domain. Second, the voltage distribution along the entire line is obtained via numerical solutions. Third, the faulted segment and fault location is determined based on the calculated voltage distribution. The proposed method is carefully designed to ensure applicability for a general AC/DC transmission line, independent of the numbers of phases/poles, non-homogeneous (including partially mutually coupled) sections, terminals, and joint points. Numerical experiments in two example complex transmission lines prove that the proposed method can accurately identify faulted segments and locate faults under different fault conditions. The method works with a relatively low sampling rate of 20k samples/sec and a data window of 5 ms after the fault occurs.

Two-terminal traveling-wave-based non-homogeneous transmission-line protection

This paper presents a two-terminal traveling-wave-based protection algorithm applied to non-homogeneous transmission lines comprising any number of sections with different topologies and considering the effect of the sampling rate. Existing two-terminal traveling wave protection functions cannot protect the line under close-in faults and present limitations in non-homogeneous transmission lines. However, the effects of the sampling rate, considered in the proposed method, result in well-defined protection and unprotected zones, essential for protection security and coordination to deal with the issue of close-in faults in non-homogeneous transmission lines. Furthermore, the algorithm can accurately detect the faulted section, allowing its use in advanced protection functions such as adaptive automatic auto-reclosing and high-speed protection schemes. A protection device was modeled considering a sampling frequency equal to 1 MHz, including functions to detect traveling waves via wavelet transform, and the proposed protection algorithm to discriminate line internal from external faults, and to select the faulted section. The algorithm was evaluated using a large number of ATP fault simulations. The results show that the algorithm is robust and reliable for protection devices installed in non-homogeneous lines.

Edge Computing-Based Fault Location in Distribution Networks by Using Asynchronous Transient Amplitudes at Limited Nodes

The feeders in distribution networks can be generally classified into two types: homogenous and hybrid feeders. Hybrid feeders consist of non-homogeneous line segments. In this paper, a fault location scheme is proposed for distribution grids with both homogenous and hybrid feeders using the edge computing. The standard transient amplitude ratio arrays of the hybrid feeders are first constructed and stored at the edge nodes. Then, an accurate fault location model is trained by the radial basis function neural network and stored in the substation server. To achieve this goal, the transients are first sampled at the measurement nodes and transmitted to the edge nodes nearby. The amplitudes are then extracted to determine the faulty branch. For a hybrid feeder, the actual amplitude ratio array is compared with the standard one to identify the faulty line segment. Finally, the amplitude ratio of the two transient components with different frequencies at one terminal of the faulty section is computed and transmitted to the server. Based on the model of a distribution network built by PSCAD/EMTDC, extensive fault simulations are studied. The results demonstrate the effectiveness of the scheme.

Non-uniform lines – review of the theory and measured / simulation examples

This paper reviews existing theories dealing with non-uniform lines both in time domain and in frequency domain. Some papers discussed a non-homogeneous line composed of cascaded homogeneous lines. The theory in the papers neglected lead wires between the cascaded lines. This is mathematically permissible, but physically impossible and thus the theory result in an in-accurate or erroneous solution of the non-homogeneous line. The lead wires are non-uniform because the geometrical configuration at the sending end of the lead wires, i.e. the first homogeneous line, differs from that at the receiving end, i.e. the next homogeneous line. Measured results in time and frequency domains and FDTD computed results are demonstrated for the non-uniform line characteristics. Finally, approximate calculations by a circuit-theory based approach including EMTP are compared with the measured and FDTD computed results, and the limit of the circuit-theory approach is explained.

Closed-Form Solution for Traveling Wave-Based Fault Location on Non-Homogeneous Lines

In this paper, a closed-form solution for traveling wave (TW)-based fault location on non-homogeneous lines (NHLs) with multiple sections is proposed. It is able to accurately estimate the fault location on NHLs, taking into account the different propagation velocities, irrespective of the number of sections, including the effects of line electrical parameters uncertainties. The algorithm can be applied to non-homogeneous transmission networks composed by overhead transmission lines (OHLs), underground cable lines (UCLs), submarine cable lines (SCLs), or by any other line section with considerably different electrical characteristics. A wide variety of fault scenarios were simulated in a 380 kV/50 Hz NHL consisting of multiple OHL, UCL, and SCL sections. In each simulation, the proposed algorithm performance was compared against those obtained from an existing two-terminal TW-based fault location approach. The obtained results reveal that the proposed closed-form TW-based solution is generalist and reliable, being useful for fault location applications on NHLs.

Performance analysis of non-homogeneous hybrid production lines based on decomposition method

For analysing performance of non-homogeneous hybrid lines, several new techniques are proposed to transform non-homogeneous production lines into homogeneous lines so that the traditional decomposition method can be utilised to analyse non-homogeneous hybrid lines. The techniques are complementary to the current transformation technique. The techniques are tested and discussed by numerical experiments based on the decomposition method. It is shown that the new transformation techniques have good estimations on the performance of the lines with weak non-homogeneousness in comparison with the traditional technique. Furthermore, the discussion of the techniques clears several questions about the traditional transformation technique, which were answered in former studies. The new techniques help promote the application of the homogenisation technique of non-homogeneous lines.

High‐impedance fault location using matching technique and wavelet transform for underground cable distribution network

AbstractLocating the faulty section of a high‐impedance fault (HIF) is quite challenging for the underground distribution network of a power system. The complexity of the distribution network, such as branches, nonhomogenous lines, and HIF, contributes to the difficulties in locating the faulty section. In this paper, the shortest distance (SD) technique and a database approach have been proposed to determine the faulty section. A multiresolution analysis based on discrete wavelet transforms is chosen to extract the unique features from voltage signals during the HIF event. The output coefficients from the decomposition process is stored in a database and used as the input data for the SD algorithm. The first, second, and third level of detailed coefficients of the post‐disturbance voltage signal were utilized for the identification of the faulty section using the proposed method. A ranking analysis was created to provide a number of possibilities of faulty section. In this paper, a 38‐node underground distribution network system in a national grid in Malaysia was modeled using the PSCAD software. The proposed method was able to successfully determine the faulty section. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

An Algorithm for Locating Faults in Three-Terminal Multisection Nonhomogeneous Transmission Lines Using Synchrophasor Measurements

This paper presents a fault location algorithm for three-terminal multisection nonhomogeneous transmission lines using synchronized phasor measurements (synchrophasors) obtained from GPS based PMUs or digital relays with embedded PMUs or off-line data synchronization algorithms. The algorithm is extended from a two-terminal fault location technique to an algorithm for three-terminal multisection nonhomogeneous lines which combine overhead lines with underground power cables. An exclusively three-terminal faulty branch indicator/fault locator for nonhomogeneous lines is proposed, which can not only distinguish an external/internal fault but is able to locate a fault on an overhead line or an underground cable as well. The algorithm provides an exact solution for fault location estimation and excludes computational costs since neither fault type selections nor iterative operations are required. An extensive series of simulations and field evaluations have been conducted to show the effectiveness of the method. The proposed algorithm has already been implemented in Taiwan 161 kV transmission system. So far the technique yields excellent accuracy and robustness compared to existing fault location functions of digital relays in Taiwan.

Performance Analysis of Non-Homogeneous Hybrid Production Lines

 Abstract—For analyzing performance of non-homogeneous hybrid lines, a new technique of dealing with nonhomogeneous lines is proposed to transform a non-homogeneous production line into a homogeneous line, which is based on decomposition method. The technique extends the applicability of decomposition method to nonhomogeneous lines. The technique is discussed by numerical experiments comparing with aggregation method, what's more, the advantages and disadvantages are specified. The technique complements and develops the system analysis techniques of hybrid production lines. Index Terms—Hybrid system, system performance, Non-homogeneousness, decomposition method.

Lockout/tagout and optimal production control policies in failure-prone non-homogenous transfer lines with passive redundancy

This paper considers a production problem for a transfer line subject to random failures and repairs, and differs from other studies on transfer lines. It considers a manufacturing system consisting of three machines (two machines with passive redundancy, and one in series with the previous ones) producing one part type. The control problem is subject to non-negative constraints on work-in-process (WIP). The decision variables are the production rates of two main machines and a standby machine, and influence the WIP levels, the inventory levels and the system's capacity, which is assumed to be described by a finite-state Markov chain. The objective of this paper is to minimise WIP and finished goods inventory costs; it also aims to respect the essential space–time during intervention on machine down, in order to minimise the possibility of the circumvention of protection devices or of the retraction of lockout/tagout procedures through a passive redundancy system. This paper therefore verifies the effect of passive redundancy on optimal stock levels. Given that an analytical or even a numerical solution of the problem is very difficult to find, and that we want to have a more realistic model for industries, we present a combined approach, which is presented based on a combination of analytical formalism, simulation modelling, design of experiments, and response surface methodology to optimise a transfer line with passive redundancy, producing one part type. The usefulness of the proposed approach is illustrated through a numerical example and a sensitivity analysis.

A Method for Performance Evaluation of Transfer Line with Unreliable Machines and Finite Transfer-Delay Buffers

Performance evaluation techniques of manufacturing systems are powerful decision support tools especially at system design stage. In this paper, an approximate technique based on decomposition method is proposed for performance evaluation of serial homogeneous transfer lines with unreliable machines and finite transfer-delay buffers. The characteristic of transfer-delay buffers means that it takes some transit time to transfer the parts through buffers, which increases the complexity of transfer lines. In order to address the problem, we firstly transform the initial transfer line into an equivalent transfer line, a serial non-homogeneous transfer line with unreliable machines and finite buffers. Then another transformation which replaces the equivalent line by an approximate homogeneous line is introduced. Finally, decomposition method is used to deal with the approximate model. The accuracy and efficiency of the method are validated by simulation results.

FREQUENCY PROPERTIES OF THE NON-HOMOGENEOUS PERIODICAL LINE

Frequency properties of the non-homogeneous periodical line are analyzed. The model of the signal path containing the non-homogeneous periodical line is presented. The programs for calculation of line input impedance and transfer coefficient were developed. Calculation results are presented and analyzed. They show that the stop–band appears due to periodical inhomogeneities. Its central frequency depends on the length of the period of the line. The width of the stop–band and the attenuation in it depend on intensities of periodical inhomogeneities.

Homogenisation Techniques for the Analysis of Production Lines with Unreliable Machines Having Different Speeds

This paper deals with production lines consisting of a series of machines separated by finite buffers. The processing time of each machine is deterministic, i.e., a fixed amount of time is required to perform the operation. The machines are subject to failures. We assume that the times to failure and the times to repair are exponentially distributed. In the case of homogeneous lines, i.e. production lines in which all machines have the same processing time, the use of decomposition methods is now well established. One approach for extending the applicability of these decomposition techniques to non-homogeneous lines consists in first transforming the original line into an approximately equivalent homogeneous line. The purpose of this paper is to investigate the behaviour of the methods based on this approach and compare them. We also propose a way of combining different methods.

Wave-modes and parameter matrices of non-symmetrical coupled lines in a non-homogeneous medium

The 4 × 4 A BCD, impedance and admittance matrices of non-symmetric coupled lines in a non-homogeneous medium, are expressed in terms of the properties of the normal, uncoupled wave-modes of the system. The even voltage-mode and odd current-mode pair was introduced by Ekinge (1971) for homogeneous lines and then utilized by Allen (1975) and Speciale (1975) in their study of non-homogeneous lines. In the information that follows, the dual odd voltage-mode and even current-mode pair is introduced. Both are normal modes, applicable under two different specific conditions inter-relating the line parameters.

Analysis of Gain Interaction in a Multimode Gas Laser

In this paper a theory of the gain interaction among n oscillating modes is developed starting from the rate-equations viewpoint. This approach permits one to evaluate the gain interaction terms among modes due to the well-known hole burning effect in laser gain with nonhomogeneous line shape. No account was taken of phase differences among modes and the nonlinear polarization of the medium, which give rise to combination tones. By this treatment, it is also possible to find the gain and saturation terms in single frequency operation, which are similar to those derived by Lamb. Some results on the time behavior of two modes and a set of n modes are given in the subsequent sections. Finally, formal results in second-order approximation are given, as well as an evaluation of the range of validity of first-order theory for one-mode operation at the center of Doppler curve of gain.