Major Transmission Lines Research Articles

Study of direct and indirect risk assessment of landslide impacts on ultrahigh-voltage electricity transmission lines

Ultrahigh-voltage electricity systems are a vital part of energy networks, often across wide regions passing through mountainous terrains. The instability of slopes forming tower foundations along transmission lines poses a large risk to the entire energy network. Moreover, the tower foundations along extra-high-voltage electricity transmission lines are a very special type of element that are also highly vulnerable to landslides. In this study, an integrative risk assessment framework, including a hazard assessment, vulnerability analysis for the specified element at risk, and consequence estimation, is proposed to quantify the direct and indirect risks of landslides to power transmission lines. The Yanzi landslide, where a tower of the major ultrahigh-voltage transmission line from Sichuan (western China) to Shanghai (eastern China) has just been constructed, is taken as a case study. The correlation between landslide displacement and tower structure tilting is studied. In terms of the precipitation return period, factors of safety, failure probability, and deformation are simulated. A physical vulnerability curve is fitted by assuming a Weibull relationship between the horizontal deformation (hazard intensity) of the landslide and the tower inclination ratio. The total risk is calculated as the sum of the direct and indirect losses, among which the potential indirect risk due to tower damage is much greater than the direct risk. This work demonstrates the importance of landslide treatment strategies along electricity transmission lines by considering the potential indirect risks. The risk assessment model of landslides affecting ultrahigh-voltage electricity transmission lines proposed in this study could be useful for other types of indirect landslide risk evaluations.

Convolutional Non-Homogeneous Poisson Process and its Application to Wildfire Ignition Risk Quantification for Power Delivery Networks

To quantify wildfire ignition risks on power delivery networks, the current practice predominantly relies on the empirically calculated fire danger indices, which may not well capture the effects of dynamically changing environmental factors. This article proposes a spatio-temporal point process model, known as the Convolutional Non-homogeneous Poisson Process (cNHPP), and applies the model to quantify wildfire ignition risks for power delivery networks. The proposed model captures both the current (i.e., instantaneous) and cumulative (i.e., historical) effects of key environmental processes (i.e., covariates) on wildfire risks, as well as the spatio-temporal dependency among different segments of the power delivery network. The computation and interpretation of the intensity function are thoroughly investigated. We apply the proposed approach to estimate wildfire ignition risks on major transmission lines in California, using historical fire data, meteorological and vegetation data obtained from the National Oceanic and Atmospheric Administration and National Aeronautics and Space Administration. A comprehensive comparison study is performed to show the applicability and predictive capability of the proposed approach.

Geoelectric Field Estimations During Geomagnetic Storm in North China From SinoProbe Magnetotelluric Impedances

AbstractEvaluating the impact of geomagnetic disturbances on power grid infrastructure is critical to mitigate the risk posed by geomagnetically induced currents (GICs). In this paper, the geoelectric field and induced voltage distribution in North China were estimated from the SinoProbe magnetotelluric (MT) impedance data together with the geomagnetic observatory data of six INTERMAGNET stations recorded during the significant geomagnetic storm of 17th March 2015. The measured impedances from 119 SinoProbe MT sites were convolved with geomagnetic observatory data to account for the Earth's complex three‐dimensional electrical resistivity structure. The resultant geoelectric field was then used to model the induced voltage distribution across the regional power transmission network in North China. Due to the large inter‐site distances of the SinoProbe MT program, the derived geoelectric field is mostly homogeneous, except in the Ordos Basin that displays a polarization of the geoelectric field, and with higher magnitudes in the orogenic belts. The estimated geoelectric fields in Taihang‐Lvliang, Yanshan, and Luxi orogenic belts of North China were large (>1 V/km) during the storm, due to high‐resistivity lithosphere resulting in large voltage gradients in the Earth. However, in relation to locations of major power transmission lines, only the central part of North China experienced induced voltages exceeding 100 V.

Numerical and Experimental Investigation of Time-Domain-Reflectometry-Based Sensors for Foreign Object Detection in Wireless Power Transfer Systems

Foreign object detection (FOD) is considered a key method for detecting objects in the air gap of a wireless charging system that could pose a risk due to strong inductive heating. This paper describes a novel method for the detection of metallic objects utilizing the principle of electric time domain reflectometry. Through an analytical, numerical and experimental investigation, two key parameters for the design of transmission lines are identified and investigated with respect to the specific constraints of inductive power transfer. For this purpose, a transient electromagnetic simulation model is established to obtain and compare the sensor impedance and reflection coefficients with experimental data. The measurement setup is based on parametrically designed sensors in laboratory scale, using an EUR 2 coin as an exemplary test object. Consequently, the proposed simulation model has been successfully validated in this study, providing a comprehensive quantitative and qualitative analysis of the major transmission line design parameters for such applications.

Structural performance of buried pipeline undergoing fault rupture in sand using Taguchi design of experiments

Nonlinear structural response of buried continuous steel pipeline undergoing fault rupture deformation is studied in a systematic manner. A detailed and efficient analysis framework for design is proposed and explained with a case study. A three-dimensional nonlinear finite element (FE) model previously developed and validated by the authors is used for this study. Taguchi method for design of experiments is employed to evaluate the structural performance of buried pipeline. It is also used to identify the influence of different parameters such as, the fault crossing angle, faulting type, the operating conditions of the pipeline, geometry of the pipe cross-section and material properties of the pipe and soil on the structural behavior of buried pipelines. The proposed method can be successfully employed to derive peak strain demands as a function of fault displacements for a given set of input conditions in an efficient manner leading to an efficient and safe design solution to this problem. A case study involving NPS 24 steel pipeline with a maximum operating internal pressure of 9.1 MPa is also carried out. The method presented here is suitable for pipeline strain hazard analysis, applicable for major oil and gas transmission lines crossing seismically active faults. • An efficient design approach for oil and gas transmission pipelines crossing active faults is presented. • Only 18 analysis are carried out instead of a full factorial design of total 2916 possible combinations. • Overall, the analysis methodology will be useful in performing strain hazard analysis of pipeline fault crossings.

English

Many rural households do not have access to treated drinking water. However, some households may be in regions where a water treatment plant has excess capacity to supply some additional households. In such circumstances, small diameter low-pressure supply systems can be connected to major transmission lines to give these households access to water. These typically occur in locations that do not belong to recognized municipal or other local government. Such supply systems, commonly referred to as “trickle fill,” have been implemented in South America, Africa and Canada. This paper explains the concept of trickle fill supply systems. A user-friendly decision-making framework is proposed to assist the decision maker to determine whether the implementation of a trickle fill system is economically feasible for a given rural area. The decision-making assessment template (DMAT) takes into projects the economic, energy and carbon footprint changes. A case study for a rural municipality in the province of Alberta, Canada is presented to illustrate the value of the DMAT and the feasibility of trickle fill water supply as a solution. In this case study, a trickle fill water supply solution is found to be technically and economically viable and would reduce energy consumption and the carbon footprint. It is shown that trickle fill solution can be implemented, resulting in an average cost of water to be $165 per month per household. This is higher than the affordability threshold of 2% of the median household income, but comparable to the cost that the end users currently pay for drinking water in the area. A capital grant from a higher level of government, or low interest rate financing, would reduce the end user costs to the level of the affordability criterion mentioned here. Hence, a trickle fill solution is worth investigating for some rural residents. Key words: Rural water systems; economic feasibility; carbon footprint, small diameter water distribution pipelines.

Impact of hybrid FACTS devices on the stability of the Kenyan power system

<p>Flexible alternating current transmission system (FACTS) devices are deployed for improving power system’s stability either singly or as a combination. This research investigates hybrid FACTS devices and studies their impact on voltage, small-signal and transient stability simultaneously under various system disturbances. The simulations were done using five FACTS devices-static var compensator (SVC), static synchronous compensator (STATCOM), static synchronous series compensators (SSSC), thyristor controlled series compensator (TCSC) and unified power flow controller (UPFC) in MATLAB’s power system analysis toolbox (PSAT). These five devices were grouped into ten pairs and tested on Kenya’s transmission network under specific contingencies: the loss of a major generating machine and/or transmission line. The UPFC-STATCOM pair performed the best in all the three aspects under study. The settling times were 3 seconds and 3.05 seconds respectively for voltage and rotor angle improvement on the loss of a major generator at normal operation. The same pair gave settling times of 2.11 seconds and 3.12 seconds for voltage and rotor angle stability improvement respectively on the loss of a major transmission line at 140% system loading. From the study, two novel techniques were developed: A performance-based ranking system and classification for FACTS devices.</p>

Replacement Strategy of Insulators Established by Probability of Failure

Insulators comprise only 5% of the capital cost of transmission lines; they are accountable for 70% of line interruptions and 50% of maintenance costs of transmission lines. Major transmission lines situated in different parts of the world were mostly all constructed 30 years ago. These lines have either completed or are approaching the active life at 30 years. It is not possible to replace all insulators at a time in any utility. From a standpoint of consistency, it is quite important to locate insulators that require replacement prior to the occurrence of failure. Recalling these issues, a replacement strategy was modeled on insulator samples, operated at 154 kV, mechanical and electrical rating (M+E) 25,000 lbs and within the 10–50 years (Y) age group, collected in bulk for laboratory evaluation, based on the probability of mechanical failure (P(F)) of insulators. For conducting these studies, tensile load test such as combined electrical and mechanical failing load test was performed on selected 30 new and aged porcelain insulator samples from bulk to access recent condition. It was observed that insulators under service for 50 years manifested a decrease of 89.3% in quality factor (K), as compared to insulators within 10 years of service. A micro-structural study was carried out by using an optical microscope (OM) and a scanning electron microscope (SEM) for the further confirmation of previous evaluations. P(F) was derived by implementing Weibull distribution on the experimental observations. It was observed that insulators with an age of 50 years depicted a 2.7% increase in P(F), as compared to insulators with an age of 10 years. This article discussed a strategy for accessing the recent condition of new, aged bulk samples and the criteria of the replacement of the insulator string based on P(F).

Double Marginalization and the Paths of Natural Gas Gathering Pipelines

Efficient natural gas recovery requires the development of an extensive pipeline network of gathering lines, connecting individual gas wells with processing stations and major transmission lines. Networks of gathering lines are likely to face the economic problem of double marginalization, whereby it is more expensive to run a pipe of a given length through a geographic area that is owned by multiple parties than it would be if the area were owned by a single party, ceteris paribus. Due to the economics of double marginalization, gathering lines may be placed so as to avoid paths with multiple property owners. I formalize this using a simple game theoretic model, and explore this theory empirically in Bradford County, Pennsylvania, a jurisdiction that has recently experienced a dramatic increase in natural gas production due to recent innovations in drilling. In Bradford, I observe the locations of recently drilled gas wells and, importantly, gathering lines for a single cross-section of the county taken in 2012. I combine these data with data on tax parcel boundaries in order to investigate whether the paths taken by gathering lines are influenced by parcel ownership patterns in ways consistent with the economic theory of double marginalization.

Strategic conservation for lesser prairie-chickens among landscapes of varying anthropogenic influence

For millennia grasslands have provided a myriad of ecosystem services and have been coupled with human resource use. The loss of 46% of grasslands worldwide necessitates the need for conservation that is spatially, temporally, and socioeconomically strategic. In the Southern Great Plains of the United States, conversion of native grasslands to cropland, woody encroachment, and establishment of vertical anthropogenic features have made large intact grasslands rare for lesser prairie-chickens (Tympanuchus pallidicinctus). However, it remains unclear how the spatial distribution of grasslands and anthropogenic features constrain populations and influence conservation. We estimated the distribution of lesser prairie-chickens using data from individuals marked with GPS transmitters in Kansas and Colorado, USA, and empirically derived relationships with anthropogenic structure densities and grassland composition. Our model suggested decreased probability of use in 2-km radius (12.6 km2) landscapes that had greater than two vertical features, two oil wells, 8 km of county roads, and 0.15 km of major roads or transmission lines. Predicted probability of use was greatest in 5-km radius landscapes that were 77% grassland. Based on our model predictions, ~10% of the current expected lesser prairie-chicken distribution was available as habitat. We used our estimated species distribution to provide spatially explicit prescriptions for CRP enrollment and tree removal in locations most likely to benefit lesser prairie-chickens. Spatially incentivized CRP sign up has the potential to provide 4189 km2 of additional habitat and strategic application of tree removal has the potential to restore 1154 km2. Tree removal and CRP enrollment are conservation tools that can align with landowner goals and are much more likely to be effective on privately owned working lands.

Persistence of greater sage‐grouse in agricultural landscapes

ABSTRACTLocal extirpations influence species’ range contractions and are often precursors of range‐wide extinction. Understanding extinction dynamics is important for devising effective management strategies to protect threatened and endangered species. The greater sage‐grouse (Centrocercus urophasianus) is an example of a species undergoing range contraction, and has been extirpated from nearly half its historically occupied habitat. We used species distribution modeling to quantify environmental variables constraining a threatened sage‐grouse population inhabiting an agricultural landscape in Washington, USA. Fields planted to perennial vegetation as part of the Conservation Reserve Program (CRP) were important in providing year‐round habitat for sage‐grouse but only when intermixed with native sagebrush‐steppe vegetation. Without the CRP, we estimate 66% of sage‐grouse habitat in the study area would become unsuitable. Conversely, if CRP allotments were concentrated near occupied native sagebrush‐steppe, we estimate the area of sage‐grouse habitat could be increased by up to 63%. In addition to the area of native sagebrush‐steppe and CRP lands, we also found that climate variability, the patch configuration of sagebrush‐steppe, and proximity to major roads and transmission lines constrain the distribution of occupied habitat within the study area. Our study demonstrates how conservation programs such as CRP may be used as a management tool to reduce the risk of extirpation in agricultural areas, and to facilitate species range shifts in response to climatic changes in the sagebrush biome. © 2017 The Wildlife Society.

Safeguarding the Supergrid

Imagine a blazingly hot day in central China, when all the air conditioners in every megacity are running at full blast. Through the remote mountains of Shanxi province, the major transmission lines that carry ultrahigh-voltage electricity to the cities are operating at close to maximum capacity.

A PMU-augmented stability power limit assessment for reliable arming of special protection systems

This paper studies the application of phasor measurement unit (PMU) data for security-enhanced arming of special protection systems. A PMU-based hybrid method is proposed to assess transient stability limits of a multi-machine system in advance of network contingencies. The method is based on the single machine equivalent (SIME) technique, which combines time-domain algorithms with the direct method of equal-area criterion, to determine stability power limits on major transmission lines. In addition, based on the real-time network condition obtained by synchrophasor measurements, a strategy is proposed to effectively determine whether an arming signal should be issued for the next probable contingency. The effectiveness of the PMU-based automatic arming method is evaluated and discussed through simulation studies conducted in the real-time digital simulator (RTDS) and MATLAB software environment.

Research of Modeling Method of Transmission Line Information Based on IEC61850

Currently the IEC 61850 standard for the transmission line has not been established a complete data model, restricting the development of smart grid. This paper is based on the study of the IEC 61850 standard, and information on major transmission lines were analyzed in detail, in accordance with the standard information of transmission line model based on IEC 61850 was established.

Transmission lines: equivalent circuits, electromagnetic theory, and photons

This rigorous treatment of transmission lines presents all the essential concepts in a clear and straightforward manner. Key principles are demonstrated by numerous practical worked examples and illustrations, and complex mathematics is avoided throughout. Early chapters cover pulse propagation, sinusoidal waves and coupled lines, all set within the context of a simple lossless equivalent circuit. Later chapters then develop this basic model by demonstrating the derivation of circuit parameters, and the use of Maxwell's equations to extend this theory to major transmission lines. Finally, a discussion of photonic concepts and properties provides valuable insights into the fundamental physics underpinning transmission lines. Covering DC to optical frequencies, this accessible text is an invaluable resource for students, researchers and professionals in electrical, RF and microwave engineering.

Hungary-Ukraine Energy Cooperation and Its Contribution to the Security of Supply in the European Union

The European Union (EU) is expected to be increasingly dependent upon non-EU primary energy resources as domestic resources are depleted. Ukraine is the largest country in the world by the volume of gas transit: Annually through the Ukrainian gas pipeline the transit gas deliveries amount to 140 billion m3 including 120 billion m3 to countries of Central and Western Europe. Ukraine also has an underutilized 750 kV transmission line that reaches into the heart of the neighbouring EU member Hungary. This high-level natural gas transportation infrastructure and the existence of major electricity transmission lines results in Eastern Hungary being a key location for a 2,400MW Combined Cycle Gas Turbine (CCGT) plant. A large CCGT power plant usinig the best available technology in this region would not only benefit from existing infrastructure but also provide electricity for the Central and Eastern European (CEE) region, and may supply the impetus for major regional development initiatives.(1)

A FREE MODEL BASED CONTROLLER DESIGN FOR POWER SYSTEM STABILIZATION

This paper presents an intelligent modeling approach, named as free model approach, for a closed-loop system identification using input and output data and its application to design a power system stabilizer (PSS). The free model concept is introduced as an alternative intelligent system technique to design a controller for an unknown system with input and output data only, and without the detailed knowledge of mathematical model for the system. In the free model, the data used has incremental forms using backward difference operators. The parameters of the free model can be obtained by the simultaneous perturbation stochastic approximation (SPSA) method. The feasibility of the proposed method is demonstrated in a one-machine infinite-bus power system. The linear quadratic regulator method is applied to the free model to design a PSS for the system, and compared with the conventional PSS in different loading conditions and system failures such as the outage of a major transmission line or a three phase to ground fault which causes the change of the system structure.

A PMU based special protection scheme: a case study of Taiwan power system

This paper proposes a special protection scheme to prevent power system blackout due to a sequence of relay trip events based on phasor measurement units (PMUs). In a control center, we use PMU's to monitor the generators and the major EHV transmission lines of a power system, and apply an instability prediction algorithm for initiating a special protection schemes (SPS) to avoid a sequence of relay trip events whenever necessary. When a fault happens, we group the generators swinging coherently and reduce the system to One-Machine-Infinite-Bus (OMIB) system. The remedial control actions consist of load shedding and generation tripping. The strategy for determining the amount of remedial control actions is a proposed relay setting limited equal-area criterion for OMIB. A case study of Taiwan power system assumed to be equipped with proposed special protection scheme is conducted. Encouraging results are obtained.

An intelligent based LQR controller design to power system stabilization

This paper presents an intelligent model, named as free model, approach for a closed-loop system identification using input and output data and its application to design a power system stabilizer (PSS). The free model concept is introduced as an alternative intelligent system technique to design a controller for such dynamic system, which is complex, difficult to know, or unknown, with input and output data only, and it does not require the detail knowledge of mathematical model for the system. In the free model, the data used has incremental forms using backward difference operators. A linear transformation is introduced to convert the free model into a linear model so that a conventional linear controller design method can be applied. Also, it is shown that the free model is controllable, observable, and robust to disturbance. In this paper, the feasibility of the proposed method is demonstrated in a three-machine nine-bus power system. The linear quadratic regulator (LQR) method is applied to the free model to design a PSS for the system, and compared with the conventional PSS and LQR controller based on the ARMA-model. The free-model based (FMB) PSS is robust in different loading conditions and system failures such as the outage of a major transmission line or a three phase to ground fault which causes the change of the system structure.

Intelligent system identifies and locates transmission faults

When faults occur on major transmission lines, the bulk power system is immediately exposed to potentially costly outages. During peak loading conditions, when line availability is most critical, a lengthy outage can be detrimental to system operations. In an age of open access and retail wheeling, power exchanges are bound by contract, and any unnecessary delay of energy restoration compromises a utility's competitive position. It is necessary for protection and operation personnel to locate the fault as accurately and as expeditiously as possible. Within large utility systems, major transmission lines are located in remote or inaccessible areas, which makes fault finding difficult. The combination of using a two-ended algorithm along with the advent of improved communication technology, mathematical techniques, and PC applications made possible the development of an automatic fault location system. IFL is a PC/Windows-based operator's tool that uses two-ended loop fault analysis to identify fault types and location. The system is innovative in its integration of mature, low cost, and reliable instrumentation, combined with advanced applied mathematics to achieve a mission-critical system for electric system maintenance and operation.