Length Of Transmission Line Research Articles

Design of Broadband Compact Grid Array Antennas Using Gradient Slow-Wave Structures

Compact grid array antennas (GAAs) with the gradient slow-wave structures are designed in this letter. The electrical lengths of slow-wave transmission lines (SW-TLs) with gradient structures are investigated based on the equivalent microwave network. By utilizing SW-TLs with exponential gradient structure on the long sides of GAAs, the proposed antenna achieves an area-reduction factor of 24.4%, with a measured 10 dB impedance bandwidth from 27.50 to 33.86 GHz and a maximum gain of 15.71 dBi.

Benchmarking of the Electricity Sector in East Africa: An Assessment of Technical Efficiency

The electricity sector has globally been subject to reforms since the 1990s. The reforms consisted of unbundling vertically integrated monopolies and attracting the private sector with a view of improving quality of service (QoS) and technical efficiency. In some East African countries, however, the electricity sector remains vertically integrated. Controlling electricity losses has been difficult, resulting in poor QoS. This paper analyzes and compares the performance of the East African power sector with regard to QoS. A non-parametric approach, Data Envelopment Analysis (DEA) was used to estimate the technical efficiency scores and the Total Factor Productivity Change (TFPC) for productivity improvement under two models, generation and transmission-distribution (TD). Data comprising two outputs and three inputs was collected in Burundi, Ethiopia, Kenya, Rwanda, Tanzania, and Uganda for the period 2008-2017. On average, the East African power sector exhibits performance gaps of 20% for the generation model, and 22% for the TD model. In the generation model, it exhibits Decreasing Returns to Scale (DRS) at a frequency of 34 out of 60, compared to 16 for Increasing Returns to Scale (IRS) and 10 for Constant Returns to Scale (CRS). However, in the TD model, IRS are the most dominant, with a frequency of 31 out of 60 compared to 19 and 10 for DRS and CRS respectively. Inefficiency is largely attributed to excess inputs, including high-voltage transmission line lengths and electricity losses, as well as a shortage of outputs, such as the number of customers. The study also shows a global productivity improvement, which is linked to efficiency change for the generation model and technological change for the TD model. Specifically, countries that have attracted the private sector into the generation and/or distribution sectors have improved their productivity compared to others with state-owned utilities.

Improvement of the Iraqi Super Grid Performance Using HVDC/HVAC Links by the Integration of Large-Scale Renewable Energy Sources

The increasing use of renewable energy sources (RES) and their integration into transmission systems requires extensive studies to get more benefits from these sources. Stability analysis is one of the most crucial issues in these systems, and therefore needs to be studied in depth. In this paper, an analytical study was conducted for the stability assessment of the Iraqi super grid after adding a solar power plant with a capacity of 1000 MW using both HVAC and HVDC links for comparison purposes. Thus, the objective of this study was to determine the best way to integrate RES into the power grid while improving its performance. The system’s stability was evaluated for two types of faults: line and bus disturbances. The strength of the grid and its ability to absorb the newly added energy was also studied. The simulations were performed with the PSS/E software using the Newton-Raphson method for a 500 km transmission line length. The results showed that the HVDC link outperforms the HVAC link in improving the overall performance of the power system.

Development of a Software Package for Digital Forest Inventory Based on Aerial Photography Data

When clearing protective strips for linear infrastructure such as power lines, it is important to minimize tree felling. The purpose of the study is to develop and test a software package for digital forest inventory of tree and shrub vegetation in the zones of linear infrastructure facilities. In the study, a software package for digital forest inventory based on aerial photography with UAVs was developed and tested, based on the methods of multilayer perceptron and a self-organizing network based on competition (Kohonen network). The approbation has shown that it allows to accurately identifying the presence and height of trees and shrubs in the protection zones, to obtain precise coordinates for planning clearing works. At present, the areas of the territory where it is necessary to remove trees and shrubs are determined manually with an overestimation of 25-50%. Therefore, the use of a software package for digital forest inventory allows you to save up to 0.8 hectares of trees and shrubs per 1 kilometre of the length of the power transmission line, as well as save about 27 thousand rubles (about 375 US dollars) per 1 kilometre during work.

Estimation of stored energy for TWIN source HVDC transmission line

TWIN source is a two driver based negative ion source currently operational at IPR. The two driver RF negative ion source test bed to extract and accelerate H- ion beams up to 50 keV. For Negative Neutral Beam Injectors (NNBI) utilizing RF negative ion source, grid breakdown is a routine phenomenon during system conditioning and operation phases. During the grid breakdown event, there are chances that electrostatic energy stored in the transmission line is dumped in the grids, which may possibly damage them. In case of NNBI system with long high voltage transmission line, contribution for the stored energy emanates from their inter-conductor capacitance. The inter-conductor capacitance and thus stored energy could be reduced by proper designing of the HVDC Transmission line. However, it is equally difficult and challenging to estimate the inter-conductor capacitance of the transmission line with non-generic cross sections. This paper discusses estimation of inter-conductor capacitance, an experimental set up to realize a grid breakdown and thus estimate the stored energy of a HVDC transmission line prototype (1m length). The HVDC transmission line prototype (1m length) has vertical placement of conductors. Inter-conductor capacitance is estimated for vertical topology. The stored energy values from estimated inter-conductor capacitance value is compared with experimental results for HVDC transmission line prototype (1m length). Also, modeling of HVDC transmission line is done to simulate a grid breakdown and thus compute the stored energy for entire transmission line length (120m).

CHARACTERISTICS OF ELECTRIC COMPANIES BY THE NUMBER AND LENGTH OF TRANSMISSION LINES AND SUBSTATION CAPACITY

The article presents statistical data on the number and length of power transmission lines, the number and capacity of substations of different voltage classes in the branches of the Public Joint Stock Company «Rosseti Center and Volga Region». A review of the literature shows that there is no information about the specific values of the length of the power transmission line, substation capacity and transformer capacity per square kilometer and per inhabitant of the regions where the branches of the Public Joint Stock Company «Rosseti Center and Volga Region» are located. (Research purpose) The research purpose is analyzing the structure of electrical companies on the example of the electric company PJSC Rosseti Center and Volga Region. (Materials and methods) In the research was used literary sources, statistical data on the structure of electrical equipment of the Public Joint Stock Company «Rosseti Center and Volga Region» by area and number of residents in the regions where the branches are located. (Results and discussion) Calculations of average and specific values of the number and length of power transmission lines, the number and capacity of substations by branches of the Public Joint Stock Company «Rosseti Center and Volga Region» were performed. The branches were compared according to the specified values, the largest and smallest values of the considered characteristics. (Conclusions) The characteristics of electric companies providing electricity to rural consumers were given on the example of branches of the Public Joint Stock Company Rosseti Center and Volga Region in terms of the number and length of power transmission lines, the number and capacity of substations of different voltage classes, including their specific values. The described characteristics, when further compared with the values of population density, agricultural production indicators and other indicators of the regions, make it possible to analyze the dependence of the development of regions on the characteristics of electric networks and vice versa. The data obtained for January 2022 make it possible to assess the dynamics of the development of grid complexes of branches of the Public Joint Stock Company Rosseti Center and Volga Region.

Data mining model and Gaussian Naive Bayes based fault diagnostic analysis of modern power system networks

In this paper, different machine learning (ML) algorithms like Gaussian Naïve Bayes (GNB), K-Nearest Neighbours (KNN), Decision Tree (DT), Support Vector Machine (SVM), Random Forest (RF) and Adaptive Boosting Classifier (ABC) are used to classify the different types of faults on the transmission line. The faults and non-faults on the transmission line are created by simulating the transient behaviour of the long length transmission line by using PSCAD/EMTDC software. While simulating the faults and non-faults on the transmission line, fault resistance, fault inception angle, fault location and fault type are varied within their practical range. During the simulation, currents and voltages of three phases on both sides of the TL are measured using Current Transformers (CT) and Potential Transformers (PT) . Measured currents and voltages are pre-processed to produce the time series and frequency series parameters data set by using Fourier Transform in full cycle, half cycle, and quarter cycle from the fault instant. Feature reduction techniques select very important parameters among the calculated time series and frequency series parameters. After completing the data generation and pre-processing and application of feature reduction techniques, the machine learning algorithms are applied to the data in python software to get the comparative analysis. Noise analysis is also carried out in this work to assess the performance of the ML algorithms in dealing with the nonlinear data due to CT, PT saturation, and measurement errors.

The Impacts of the Transmission Line Length in an Interconnected Micro-Grid on its Performance and Protection at Different Fault Levels

The Impacts of the Transmission Line Length in an Interconnected Micro-Grid on its Performance and Protection at Different Fault Levels

Environmental Efficiency Evaluation of China's Power Industry Based on the Two-Stage Network Slack-Based Measure Model.

How to achieve the continuous improvement of the environmental performance level of the power industry within the requirements of clean and low-carbon energy development is the fundamental requirement and inevitable choice for the construction of ecological civilization and sustainable development. From the perspective of environmental protection, based on the Data Envelopment Analysis (DEA) method and the internal mechanism of power system production and supply, the power industry environmental efficiency evaluation index system was constructed, and the two-stage Network Slack-based Measure (NSBM) model considering undesired output was used to calculate China’s 30 provinces and municipalities from 1998 to 2019. The environmental efficiency is divided into two links: power generation efficiency and transmission and distribution efficiency. The study found that, within the research interval, the overall environmental efficiency of China’s 30 provinces is low, and the differences between provinces and cities are large, but they have gradually developed in a better direction after 2015. The power generation efficiency of the first link in most provinces and municipalities is higher than the transmission and distribution efficiency of the second link, and the low transmission and distribution efficiency is an important reason for the low comprehensive level of environmental efficiency. The overall evolution trend of environmental efficiency in the six regions of China is roughly the same, but the regional differences are obvious, showing a trend of “high in the southeast and low in the northwest”. The economic and natural resource differences in different provinces and cities in each region have led to varying degrees of redundancy in five aspects, including investment in power assets, installed power generation capacity, and length of transmission lines, which seriously affect the environmental efficiency of the power industry. This research attempts to open the “black box” of the environmental efficiency conversion process of the power industry, which can provide directions and strategic suggestions for the improvement of the efficiency of the power industry in China.

Surface wave transmission line theory for single and many wire systems

Examining cables using the many conductor transmission line theory has shed light on the modes supported by various cable types. However, so far, the theory disregards the fundamental surface wave mode whose lateral confinement increases with frequency and hence is expected to play an important role in high-frequency applications. To address this issue, we propose an extension to the theory that incorporates surface waves on uncoated, cylindrical wires. Crucially, this requires new definitions of the per unit length transmission line parameters, which are derived using the single wire surface wave solution. By closely examining a two-wire and a three-wire system, we show that these new parameters can predict surface waves as well as modes found using conventional many conductor transmission line theory. Furthermore, all calculated modes are validated experimentally by diagonalization of a measured coupling matrix. Additionally, the propagation constants for the modes predicted by the model are validated against full numerical simulations. Good agreement is observed when proximity effects can be neglected.

Inside-wind-farm/Wind-farm-grid sub-synchronous oscillation characteristics analysis in grid-connected system of multiple DFIGs

Aiming at the sub-synchronous oscillation (SSO) problem of the grid-connected system of multiple DFIGs, most of the existing theoretical studies take the entire wind farm as a single-machine model, the stand-alone model cannot reflect the inside-wind-farm oscillation mode produced by the interactions among DFIGs in the wind farm. Therefore, this paper takes the equivalent value of DFIG-based wind farm to three DFIGs, establishes a mathematical model of the grid-connected system of three DFIGs, and studies the sub-synchronous oscillation modes existing in the system through eigenvalue analysis and participation factor analysis. The results show: When the length of transmission line increases, the oscillation frequency of the inside-wind-farm/wind-farm-grid sub-synchronous oscillation mode increases, the damping decreases and the stability weakens; when the number of grid-connected DFIGs increases, the oscillation frequency of the inside-wind-farm/wind-farm-grid sub-synchronous oscillation mode decreases, the damping increases and the stability enhances. Finally, a time-domain simulation model of the grid-connected system of multiple DFIGs was built in PSCAD/EMTDC to verify the correctness of the theoretical analysis results.

Collective Impact of Multiple Doubly Fed Induction Generators With Similar Dynamics on the Oscillation Stability of a Grid-Connected Wind Farm

This paper examines the small-signal oscillation stability of a grid-connected wind farm affected collectively by multiple doubly fed induction generators (DFIGs) with similar dynamics. An analysis of this issue, which is referred to as the collective impact of similar DFIGs, revealed that the interconnection of a standalone DFIG with the rest of the wind farm determines whether the collective impact of similar DFIGs is beneficial or detrimental to the oscillation stability of the wind farm. The network topology and parameters of the wind farm affect the scale of the collective impact in several respects. First, increasing the length of the transmission line connecting the wind farm to the AC grid leads to an increase of the collective impact. Second, when the transmission line is much longer than the cables within the farm, the collective impact is approximately proportional to the number of DFIGs. Accordingly, increasing the transmission line length and/or number of DFIGs may magnify the detrimental collective impact, resulting in growing oscillations in the wind farm in the worst case. The analysis of the collective impact of similar DFIGs in this study revealed a new mechanism through which grid-connected DFIG wind farms can lose oscillation stability.

Grid-connected resonance analysis of half-wavelength transmission system with wind power and photovoltaic power supply

New energy centers such as wind power and photovoltaic power generation are generally too far away from the load center. Half wavelength AC transmission technology can solve this problem. However, harmonics may be generated when new energy is connected to half wavelength transmission system. Harmonics will do harm to the normal operation of power grid. Therefore, this harmonic resonance problem is studied in this paper. Firstly, this paper expounds the principles of classical resonance analysis method and modal analysis method, and explains the advantages of modal analysis method through analysis and calculation. Then, the grid connected resonance of large-scale wind farm and photovoltaic power station connected to half wavelength transmission system is studied by modal analysis method. The effects of transmission line length, the number of groups of wind power and photovoltaic inverters on typical modal harmonic resonance are analyzed. The results show that the length of half wavelength transmission line and outgoing line only affect the low-frequency harmonic resonance of some modes; The length of collector cable has an effect on the harmonic resonance of each typical mode; The number of wind power and photovoltaic inverter groups has an impact on the harmonic resonance of some modes, but will not change the location of resonance.

STUDI KOORDINASI KERJA RELAI JARAK SEBAGAI PENGAMAN CADANGAN PADA SALURAN 150 KV GIS PESANGGARAN-GI NUSA DUA

The development of Pesanggaran Conventional Substation into the Pesanggaran GasInsulated Switchgear (GIS) as a form of increasing the reliability of the electric power system inBali which led to changes in the protection system configuration on the transmission lineconnecting the GIS Pesanggaran and Nusa Dua Substation. The distance relay that waspreviously functioning as a primary protection was changed to backup protection due to the lackof selectivity of the distance relay in isolate the disruption and as the backup protection if themain protection experiencing a failure. Simulation testing using power system analysis softwareafter determining the value of the distance relay setting and tested with short circuit at 110%and 180% of the transmission line length shows the distance relay has worked according to theP3B JB regulation No. 211/151/P3B/2010 and distance relay can detect disruption in zone 2with a delay time of 0,815 seconds and detect disruption in zone 3 with a delay time of 1,615seconds.

Methods for alleviation of impacts of axial diffusion on decomposition products monitoring in gas‐insulated transmission lines

Considering the long length of gas-insulated transmission lines (GILs), novel methods are required to alleviate the impacts of axial diffusion on decomposition products' monitoring. The diffusion process of two typical decomposition products, SO2 and SO2F2, was studied. During the diffusion experiments, SO2 and SO2F2 were generated by partial discharges. Based on Fick’s law, an axial diffusion model of SO2 and SO2F2 was proposed. By combining the experiment and simulation results, it was found that the diffusion coefficient of SO2 was greater than that of SO2F2. In addition, the concentration variation at different positions would experience some delay and decay in axial direction. The delay and decay were inversely related to the diffusion coefficient and increased with prolongation of the distance. Based on the diffusion characteristics determined, methods for optimising the monitoring positions, correcting concentration, and using the concentration ratio and generation rate were proposed to alleviate the impacts of diffusion. The methods could allow the decomposition products to be monitored in 1 month and reduce the monitoring error to 10% or less. The diffusion model and the methods could be useful for monitoring decomposition products in GILs.

Compact and Narrow-Band Bandpass Filter Using Spoof Surface Plasmon Polaritons

This letter presents a novel narrow-band bandpass spoof surface plasmon polarition (SSPP) filter, which has a controllable passband, good rejection, and a compact structure. It is composed of two end-extending SSPP transmission lines and a pair of L-shaped coupling branches. Both the bandwidth and the central frequency can be adjusted by changing the depth of the SSPP unit and the length of SSPP transmission line behind the coupling branches. The dispersion curves of the SSPP unit are analyzed, and the influences of some structural parameters are investigated. A SSPP band-pass filter is fabricated and measured based on the proposed method, showing a wide 3-dB fractional bandwidth of 11.2% centered at 6.25 GHz and an out-of-band rejection below -15 dB within 1-10 GHz. The measured result shows good agreement with the simulated one.

Parametric Geometrical Study of OOO-Microstrip Circuit with Dual-Band Bandpass NGD Behavior

This paper introduces a bandpass (BP) NGD circuit design engineering. The developed circuit is designed and implemented using distributed microstrip technology and operates with outstanding dual-band bandpass NGD performance added with low attenuation. The BP NGD topology presents an innovative geometrical shape represented by an OOO (triple O) structure composed of multi-parameter parallel transmission lines (TLs) based elements. The OOO type NGD circuit is mainly composed of different physical length TLs and two identical coupled lines (CLs). Then extensive parameter NGD analyses are elaborated to investigate on the influences of each physical size of OOO circuit on the NGD performances. Through the difference of physical length of transmission line, the delay can be adjusted. Through the results of simulation and measurement, it can be seen that the center frequency points are about 0.75 GHz and 1.46 GHz respectively, and the time delay is about –1.83 ns and –2.6 ns respectively.

A Game-Theoretic Approach for Electric Power Distribution during Power Shortage: A Case Study in Pakistan

Power supply is the cornerstone for the sustainable socio-economic development of any country. In a developing country like Pakistan, shortage of power supply is the main obstacle to its economic growth, making it a disputed and contested resource among different administrative units/provinces and socio-economic sectors. A key challenge is allocating the limited available power among provinces with conflicting and competing needs amid the supply-demand gap. In this research, the allocation of energy during a shortage is considered as a game-theoretic bankruptcy problem. Five bankruptcy rules namely the Proportional Rule, Constraint Equal Award Rule, Constraint Equal Loss Rule, Talmud Rule and Piniles Rule are used for power allocation among the provinces of Pakistan. Each province is characterized by its power demand. A new framework is also proposed for power allocation, which synthesizes the Nash bargaining solution concept with bankruptcy theory to resolve power-related disputes among the four provinces within Pakistan. Additionally, a new method is introduced in this study to compare and contrast the different allocation rules. The results suggest that the basic power demands of the provinces can be satisfied by the proposed disagreement points among the provinces, and the bargaining weights can highlight the role of different levels of power claims, lengths of transmission lines, and variations in population among provinces. The findings also suggest that, due to the lowest dispersion, the proportionate rule is the most suitable method for power allocation among the provinces. The paper combines relevant bankruptcy rules with Nash bargaining theory to propose an algorithm for addressing power sector supply-demand mismatches in Pakistan.

Single-end fault identification scheme for multi-terminal DC grid based on amplitude similarity of injection signal

Effective fault identification scheme plays an important role in the fault isolation stage and system recovery stage of multi-terminal DC grid. Therefore, an active detection based single-end DC fault identification scheme is proposed to improve the reliability and sensitivity of fault identification. The control strategy is suggested of the generation of sinusoidal signals at different frequencies by the hybrid modular multilevel converters. Based on the blocking effect of the fault branch on the injection signal, by introducing the improved correlation discrimination algorithm, a single-end fault identification scheme is proposed by using the amplitude difference between the measured and calculated values of injection signals. The proposed scheme can be used for fault isolation and adaptive system recovery. Intensive simulation studies prove the improved sensitivity, and reliability of the proposed scheme for the full length of transmission line without relying on DC boundary. Moreover, the scheme can identify the permanent fault during the system recovery stage.

Small-Disturbance Stability Limit of a Grid-Connected Wind Farm With PMSGs in the Timescale of DC Voltage Dynamics

This paper analytically derives the small-disturbance stability limit of a grid-connected wind farm with multiple PMSGs in the timescale of DC voltage dynamics. The derived stability limit reveals the mechanism about how the dynamics of DC voltage control and the PLLs may jointly affect the small-disturbance stability of the wind farm. Flagging the impact of PMSGs by a computational function, the stability limit indicates that decreasing value of flagging function or/and increasing maximum eigenvalue of network reactance matrix implies increased instability risk. Particularly, increasing the loading conditions and number of PMSGs in the wind farm or/and the length of transmission line connecting the wind farm with main grid may make the wind farm more prone to the loss of small-disturbance stability. Although the stability limit is derived under the assumption of identical dynamics of PMSGs, the derived small-disturbance stability limit can be applied to approximately assess the small-disturbance stability of the wind farm in the timescale of DC voltage dynamics, where dynamics of PMSGs may be either similar or considerably different. The approximate small-disturbance stability assessment is simple because the assessment does not need to establish the parametric model of the wind farm.