Power System Transmission Line Research Articles

Power Quality Enhancement Using the Interline Power Flow Controller

<p>Interline Power Flow Controller (IPFC) is one of the latest generation Flexible AC Transmission system (FACTS). It is able to control simultaneously the power flow of multiple transmission lines. This paper presents a study of the impact the IPFC on profile of voltage, real and reactive power flow in transmission line in power system. The obtained results are interesting.</p>

Stress and deformation characteristics of transmission tower foundations in permafrost regions along the Qinghai–Tibet Power Transmission Line

A transmission tower foundation embedded in frozen soil is subject to both the wind-induced uplift and frost heave forces. The frost heave results in an upward force acting on the foundation, while additional stress induced by the structure load may compress the underlying soils. The freezing- and thawing-induced deformations tend to cause further structural loads and lead to instability problems within the structure. To evaluate the engineering risk and ensure the safety of the Qinghai–Tibet Power Transmission Line (QTPTL) system, stress sensors were installed at the bases of two test tower foundations to investigate the stress state of the tower foundations. Using data on air and ground temperatures, and the deformation of tower foundations, we analyzed the stress variation, and the causes were discussed here. The results showed that the stresses at the bases of tower foundations had a close relationship with air and ground temperatures. The cooling of the underlying soils led to the occurrence of frost heave, which pushed the foundations upward and caused a significant stress bulb under the bases of tower foundations. Seasonal variations in the contact stress depended on the seasonal freezing and thawing of foundation soil. The contact stress increased with the cooling of the underlying soils and decreased with the warming of the underlying soils. The results also showed that the contact stress was free of the wind influence, i.e., the wind-induced uplift force was minor for the contact stress. To fully understand the influences of freezing and thawing on the stress state of tower foundations, a thermal–elasto-plastic finite element model for the tower foundation–soil system was established, and the stresses and deformations of a tower foundation subject to frost heave and thaw settlement were simulated. The results showed that the frost heave force induced by soil freezing potentially threatens the safety and normal operation of the QTPTL. Thaw settlement may lead to harmful deformation of tower foundations if global warming is considered in the numerical model. The remedial measure with thermosyphons only can reduce the settlement of the foundation and will increase the frost jacking risk of the foundation.

Identification and Classification of Power System Faults using Ratio Analysis of Principal Component Distances

Power system reliability operation has been one of the most vital topics under research. The power system network, mostly the long transmission lines is often subjected to different types of faults leading to maloperation of power flow. The idea of a reliable protection system is to most accurately and efficiently identifying the fault, classifying and the locating of fault. This paper represents the application of dynamic phasors in the form of Principal Component Analysis (PCA) to identify fault in a three phase one end fed 150 km long radial power system transmission line. In the proposed work, (1/4) cycle pre-fault and (1/2) cycle post fault line voltages have been extracted from Electromagnetic Transient Programming (EMTP) simulation. The proposed algorithm is trained using only one set of receiving end data carrying out fault only at the midpoint of the line to generate fault signatures using PCA. The eigenvectors and the score matrix thus obtained corresponding to the three phases using the above analysis have been utilized to construct the component distances, which have been analyzed using ratio analysis to extract the similar features of any particular fault individually.

Design of PSS and SCRC Controllers to Damp out Low-Frequency Oscillations in Power System

The paper describes a method to damp out low-frequency oscillations by design and tuning of both power system stabilizer (PSS) and controllable series capacitive reactance compensator (SCRC) controllers in power system. The PSS is generally used to mitigate the low-frequency oscillation by injecting supplementary signal to automatic voltage regulator (AVR) and the SCRC is used to enhance the transfer capacity for the transmission line in power system. Especially, the design of the external controller of the SCRC can provide effective damping for the low-frequency oscillation. In the paper, the effect of the design of both controllers on the system stability is analyzed. Also, the parameter tuning method is introduced and the performances of the proposed method are carried out by time-domain simulation with single-machine connected to infinite bus.

Optimal Measurement Allocation Algorithms for Parametric Model Identification of Power Systems

In this paper, we present an optimization algorithm that selects the optimal sets of points for placing phasor measurement units (PMUs) on the transmission lines of a multimachine power system for the purpose of identifying the best model fit for its wide-area swing dynamics. Alternatively, the method can also be viewed as a way to select the optimal set of points at which phasor values should be computed using measurements available from PMUs such that these computed values, also referred to here as pseudo-measurements, can generate the best estimate of the swing model, especially when the measurements are noisy. We pose the identification problem as an equivalent parameter estimation problem for the admittance of each tie-line and the inertia of each machine using phasor measurements of voltage magnitude, phase angle and frequency, corrupted with high-frequency measurement noise. We then formulate the Cramer-Rao bounds (CRBs) for the estimates of these unknown parameters, and show that the bounds are functions of the PMU locations and of the contribution of each measurement variable in the combined output. We finally state the condition for finding the optimal PMU location that guarantees the tightest CRB, and, therefore, the most accurate swing model for the system.

Use of transmission line having SPFC for alleviation of line over load of transmission line of an interconnected power system

This paper describes a method for alleviation of line over load in a line by regulation power flow in another line having Series Power Flow Controller (SPFC). For this purpose, the sensitivity relations between the line flow of the line with SPFC and the over loaded line are determined. These sensitivity relations are used to determine the required amount of change in power flow at the line with SPFC to reduced power flow of the over loaded line. IEEE 30 system is used to verify the applicability of the proposed method.

Investigation of Signal on Transmission Lines in Power System

Single of phasor measurement unit (PMU) in smart grid is analyzed. On the power transmission links, single of voltage and current are measured by kinds of PMUs, messages of PMUs are concentrated to PDC (Phasor data concentrator) and super PDC in power systems. Signal quality is important to power transmission, power utilization and power control for stability a power system. Harmonics, inter-harmonics, decaying DC (direct current) offset, and additive white Gaussian noise are analyzed. Odd-number harmonics and inter-harmonics affect the quality of power signals. Decaying DC offsert components influence current signal of power transmission line whose model is modeled by EMTP (Electromagnetic transient program) worldwide. Noise is generally a negligible factor on power transmission lines, since signal-to-noise (SNR) is always below 40 dB.

Implementation requirements for automated fault data analytics in power systems

Summary This paper addresses implementation requirements for a fully automated substation data integration and fault analysis for power system transmission lines. The approach is based on measurements from substation intelligent electronic device recordings. The proposed architecture provides a transparent approach to substation data management, analytics functions, as well as the visualization of the integrated data and analytics results. When combined with an efficient communication and data collection scheme, the solution bridges the gap between traditionally separated non-operational and operational data. The fault analytics results, traditionally obtained through off-line manual process, can now be used in an automated way to support on-line decisions when operating or restoring the power system. The solution is open for further expansions and interfacing to third-party systems. The paper illustrates implementation examples and provides initial in-house and field test results. Copyright © 2014 John Wiley & Sons, Ltd.

Circuit parameter calculation based on characteristic parameters and pseudo-impedance of damped oscillation signal

This paper mainly studied the circuit parameter calculation theory and the methods based on damped oscillations in transient signals. The methods can be used for the location and origin of faults by calculating the circuit parameters of transient fault signals' path when the fault occurs in the power system transmission lines. It is important in theoretical and practical engineering to locate faults in powerlines by calculating circuit parameters based on damped oscillations which are the main component of the transient signals. In R-L and R-C circuits, relations of the characteristic parameters in damped oscillation voltage and current in time domain, with the circuit parameters as well as the component parameters are deduced. And the impedance characteristic of the circuit under damped oscillation is analyzed, which is defined as a pseudo-impedance based on the definition that impedance is steady and sinusoidal. Relations between the pseudo-impedance and circuit parameters are also found. Relations between component parameter and pseudo-impedance in series or parallel are also analyzed. So methods for circuit parameter calculation are proposed separately based on the characteristic parameters and pseudo-impedance, each of which is a kind of characteristic of the damped oscillation signal. Specific calculation methods are also proposed combining with the state-of-the-art signal analysis for damped oscillation signal. Analyses in this paper may lay an important foundation for practical engineering application. The proposed theory and methods are verified based on simulation of fault signals produced by MATLAB. The equivalent circuit of an actual distribution system is simulated by using PSCAD/EMTDC. Actual fault signals reappear in the simulation. Location of single-line-to-ground fault using damped oscillation signal proposed in the paper is proved feasible.

A Criticality Assessment Method for Power Transmission Lines in Power System

Analytic Hierarchy Process (AHP) is presented in this paper to measure the relative criticality for transmission lines, considering the changes of power system’s status about transmission lines overload, central buses voltage over-limit and transient stability. At first hierarchy structure is modeled, and then indexes of criteria Layer including transmission line overload index, central buses voltage over-limit index and transient stability index were presented. The simulation results show that, the AHP assessment method can give a full consideration to transmission lines’ function, which of huge significance for identifying critical lines and increasing the security of power system.

전력계통의 정전복구시 고조파 공진억제를 위한 완충부하투입량 예측에 관한 연구

During the restoration process of primary restorative transmission system, some over voltages may happen due to nonlinear interaction between unloaded transformers and transmission systems. These over voltages caused by harmonic resonance can be suppressed by inserting damping loads before energizing transformers. But it is very difficult to predict the occurrence possibility of harmonic resonance and complex simulation must be repeated to estimate the sufficient damping loads. This paper presents a damping loads prediction system to prevent harmonic resonance. Detailed analysis of the relationship between harmonic resonance and the amount of damping loads is discussed. The prediction system is developed using a curve fitting and a neural network based on this relationship. A curve fitting used a Gaussian function based on non-linear least square method and multi-layer back-propagation neural network is applied. The system is applied to primary restorative transmission lines in korean power system and the result showed satisfactory performance.

Failure Risk Assessment of the Power System Transmission Line Based on an Improved Entropy Method

This paper presents an improved entropy method to assess the post-fault power system. The proposed method defines four indicators to assess the seriousness of the post-fault power system according to the specified severity function from the aspects of static stability and transient stability, and to weight the severity indicators through an improved entropy method. The risk assessment function for system failure is then established by combining the severity function with line fault probability model from statistical analysis of historical in power system. This proposed method has been tested with IEEE - 9 nodes system. Simulation results show that the proposed improved entropy method is able to make full use of various information, effectively avoids the problem of over weighting of any indicators, and improves the reliability and accuracy of the failure risk assessment of the power system.

WAVELET-BASED TRANSMISSION LINE FAULT DETECTION AND CLASSIFICATION

An appropriate method of fault detection and classification of power system transmission line using discrete wavelet transform is proposed in this paper. The detection is carried out by the analysis of the detail coefficients energy of phase currents. Discrete Wavelet Transform (DWT) analysis of the transient disturbance caused as a result of occurrence faults is performed. The work represented in this paper is focused on classification of simple power system faults using the maximum detail coefficient, energy of the signal and the ratio of energy change of each type of simple simulated fault are characteristic in nature and used for distinguishing fault types.

Fault Diagnosis of Transmission Lines with Rogowski Coils as Current Sensors

This paper presents implementation of algorithms developed for fault classification and location detection on transmission lines with data from current & voltage sensors. Rogowski coil as current sensor is gaining importance due to its linearity and wide band width. A lumped parameter model of Rogowski coil is developed and integrated with a power system model in SIMULINK to simulate all types of faults at different locations, fault inception angles and fault resistances. A fault classification scheme based on the evaluation of angles of fault currents and voltages is extended to secondary values obtained from Rogowski coil. Further after estimation of phasors, fault location is detected. The test results show that the proposed algorithm on primary values is equally applicable on secondary values thus offering a fast and reliable technique for fault diagnosis of transmission lines in power systems.

The Application of New Automatic Weather Station in Power System

Aiming at special demanding of weather monitoring in power system, an application project was designed basing on new type distributed and smart automatic weather station (AWS) Defects such as fixed hardware configuration and centralized data acquisition are overcome in new AWS. With distributed data acquisition node, AWS can extend and add new sensors for disaster forecasting of lightning, strong gale, icing of transmission line and insulators contamination flashover in power system and it is also convenient for evaluation of wind energy, solar energy and for power load forecasting. Using protective power supply to each node, AWS has high performance of lightning protection, which will not let system breakdown for any node crash. Three-stage automatic self-checking for node state is included, which can make failure diagnosis efficient. Data quality checking node is created in new AWS. It can provide data self-checking function and improve reliability of data from unattended AWS. Finally, application models of monitoring data are introduced. New type AWS is fit for system with many sensors or large amount of data flow. And this project can supply accurate, adequate and real-time data for weather disaster prevention and other applications in power system. DOI: http://dx.doi.org/10.11591/telkomnika.v11i2.1990

A design study on high power RF system for the TARLA facility of TAC

The Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) is a superconducting electron linac based IR FEL and Bremsstrahlung facility and it is under construction in Ankara as the first facility of the Turkish Accelerator Center (TAC) Project. TARLA will compose of two optical cavity systems to produce oscillator FEL in infrared region (2–250μm) and also Bremsstrahlung radiation to be used in basic and applied sciences.In this study, main parameters of TARLA's high power RF and power transmission line systems are defined and a 20kW RF solid state power amplifier is optimized.

A fault location method based on genetic algorithm for high‐voltage direct current transmission line

SUMMARYA fault location method based on genetic algorithm for high‐voltage direct current (HVDC) transmission line is proposed in this article. This method adopts the Bergeron model of transmission line, in which the voltage at any point of the line can be calculated by the voltage and current data sampled at both terminals of the line, and the fault position can be identified using the distributed characteristics of voltage along the line. Unlike the traditional fault location methods based on the Bergeron model, which depend on accurate line parameters and highly synchronized samples at two terminals of the line, the proposed method takes line parameters and asynchronous time at two terminals of the line together with the unknown fault location as the variables in model building to obtain the fault location. As an optimization problem, the model is solved by genetic algorithm. The significant advantage of the method is that it can reduce the influence of line parameter deviation and asynchronous samples at two terminals to the fault location result. The purpose of proposing this method is to avoid the situation without location result for the traveling wave fault location method when a grounding fault occurred with high resistance and to improve the accuracy of fault location result under harsh environment condition. The simulation model of a typical 500 kV HVDC transmission line in the Chinese power system was built by PSCAD, and MATLAB was used to verify the algorithm. Actual fault recording data obtained from the south grid of China were used to test the effectiveness of this method. Simulation results show that the proposed method is valid and is capable of eliminating the influence of line parameters deviation and asynchronous data on the accuracy of fault location results for the HVDC transmission line. Copyright © 2012 John Wiley & Sons, Ltd.

Advanced distance protection technique based on multiple classified ANFIS considering different loading conditions for long transmission lines in EPS

The advanced application of artificial intelligent techniques (AIT) was introduced recently in protection of transmission lines in electric power systems (EPS). Adaptive neuro-fuzzy inference system (ANFIS) is a promising tool among these AIT. In this proposed research, the application of ANFIS for distance relay protection for long transmission line, under different loading conditions, in electrical power systems (EPS) will be introduced and discussed. Based on multiple classified ANFIS and considering different loading conditions for long transmission lines in EPS, the suggested and proposed technique deals with fault detection, classification, and location in long transmission lines. All these tasks will be addressed in details in this article. It considers, firstly, detecting the fault occurrence in very short time and isolate the faulty section of the long transmission lines. Secondly to classify the fault type and deduce which of the three phases are exposed to the fault. Finally, locating the fault will be achieved easily even if the procedure here is completely different from short and medium transmission lines. The input training data of the ANFIS detection units are firstly derived from the fundamental values of the voltage and current measurements [using digital signal processing via discrete Fourier transform (DFT)]. These measurements were simulated considering different loading conditions.

Distance Protection Application Based on Wavelet Transform and Traveling Wave Ranging

This paper describes the wavelet transform theory, and traveling wave theory. When the power system transmission line fault occurs, the fault signal generated by sampling and analysis, and use a method of one-end fault distance measurement in transmission line. Finally the article gives the ranging devices’ hardware and software design.

A method of revealing points of minimum voltage for determining dangerous sections of electric power systems

A method of revealing points of minimum voltage on sections of the transmission lines of an electric power system is considered, which enables an automated analysis to be carried out of the mode of operation of the electric power system in order to reveal the sections of the electrical transmission with a limited possibility of transmitting the power flow. To use the method, information is required on the voltage vectors at the junctions of the electric power system, which can be obtained from a calculation of the mode of operation of the power system or by telemetry in real time. The results obtained are in complete agreement with the results of traditional methods of analyzing a power system. The method can be employed both in the design and operation of emergency automation systems and to confirm the decisions taken by experts of dispatcher services. The use of the method enables the operating reliability of the power system to be increased, and also reduces the number of outages and excessive and false operations of the emergency automatic systems.