Electrical Distance Research Articles

Electrical principles of verification of the topological structure of a low‐voltage distribution network based on voltage from an Advanced Metering Infrastructure

Topology verification supports effective management, loss reduction, and energy conservation strategies in low-voltage distribution networks across China. Of particular interest is the users-transformer connectivity relationship. Existing research shows that voltage profile similarity based on voltage data from the Advanced Metering Infrastructure (AMI) can determine the users-transformer connectivity relationship in a neighbourhood. This article analyses the electrical principles of the users-transformer connectivity relationship based on the similarity of voltage profiles and voltage data from the AMI and derives appropriate formulas that express those relationships. The results demonstrate that voltage profile similarity is not only related to electrical distance but also related to user load profiles. The validity of the derived formulas is validated in two scenarios: a correct relationship between a user and a transformer and a partial misjudgement between a user and a transformer. This article presents a theoretical foundation for analysing the connectivity relationship in low-voltage distribution networks using voltage data from AMI.

Quantitative Severity Assessment and Sensitivity Analysis Under Uncertainty for Harmonic Resonance Amplification in Power Systems

Harmonic resonances exist inherently in power systems with varying affected areas and amplification levels. This paper presents a quantitative harmonic resonance assessment technique with sensitivity analysis under uncertainty to reveal the affected areas of a harmonic resonance and corresponding amplification severities at different buses. Resonance amplification conditions at the harmonic source bus (localized resonance) and non-harmonic-source bus (non-localized resonance) are distinguished, respectively, and then a novel index to quantify the harmonic propagation areas and corresponding amplification severities are established based on harmonic electrical distances. Apart from local sensitivity analysis (SA), a global SA method is further used to perform the SA of system uncertain parameters, and three types of sensitivity parameters are distinguished and defined. In addition, comparative analysis of the proposed method with existing harmonic resonance analysis methods shows that the proposed method can not only provide more information for harmonic resonance analysis and control but is also easy and practical.

Identification of Critical Elements in Interconnected Power Networks

Modern power systems are structurally complex, consisting of elements such as buses, transformers and transmission lines, which are interconnected and liable to failures that could result in total system blackout. Early detection and quick identification of the elements that are critical to the security and reliability of such interconnected power networks is essential for smart grid applications. This paper proposes a Coupling Strength Matrix (CSM) method, which is based on Network Structural Characteristics Theory and the Relative Electrical Distance (RED) between nodes in the network. Two indices, Bus Coupling Strength (BCS) and Line Coupling Strength (LCS), are proposed in identifying the critical transmission lines and weak nodes within a power network. The proposed method is demonstrated on the standard IEEE 30-bus system and 32-bus Nigerian network. The results obtained compare well with that obtained using conventional closeness centrality-based method. This new approach could be useful in quick identification of weak nodes and critical lines that could result in voltage collapse or island formation during critical outages, with less computational burden.

Real-Time Modeling of Forward-Looking Synthetic Aperture Ground Penetrating Radar Scattering From Rough Terrain

Ground penetrating radar (GPR) is a viable tool for fast and high fidelity detection of concealed explosive threats. The radar effectiveness is limited by scattering from rough terrain which considerably obscures the buried target response. To calculate the rough ground scattering, a 3-D full-wave algorithm such as finite-difference frequency-domain (FDFD) method is required but is often prohibitive for multiple frames when the GPR antennas are distant from the target region. This paper presents a real-time 3-D modeling of a moving platform forward-looking GPR scattering from rough terrain located at great electrical distances from the GPR antenna. For a synthetic aperture, the computational domain of the focal region is reduced to a very small subset of the entire observed volume, and the surface clutter is computed via a mere multiplication of a precomputed impulse response matrix of the rough ground with the matrix characterizing the GPR transmitting signal. For a vehicle-mounted GPR detection system, this results in a significant reduction of complexity and saving of computation resources. The effectiveness of the algorithm is evaluated through an implementation of 3-D Monte Carlo simulation for various rough surface parameters. Our developed model compares well with the direct FDFD results, and can be used for lossy and frequency-dispersive soils.

Empirical modeling coupled with pore blocking for predicting cake formation of electric field effects on oily waste water cross-flow microfiltration

Cake formation is the most important phenomenon to reduce cross-membrane flux in cross-flow microfiltration although pore blocking and concentration polarization (CP) phenomena affect it. Electric field may be used to enhance process efficiency and decreased fouling phenomena in the process. An empirical model is developed here taking into consideration the cake formation effects on permeate flux reduction in the presence of AC electric field. A semi-empirical model is also developed in the presence and absence of electric field at two cases; with and without considering membrane structure in the modeling. It is the first time that electric field effects on microfiltration performance are modeled macroscopically and used with pore blocking phenomenon simultaneously. The predicted permeate fluxes by the models are compared against experimental permeate fluxes in absence and presence of electric field. Comparison of the model based predictions against experimental results indicate semi-empirical model precision with a maximum error of 8.9% for the case without and 3.6% for the case with pore blocking consideration and a maximum error for empirical model of 11.9%. Effects of different electric potentials and distances between the electrodes on CP layer thickness and oil concentration on membrane surface are also studied. The predicted results showed that the CP layer thickness is decreased by 60.9% through applying an electric potential of 500 V and also decreased by 65.2% through decreasing the distance between the electrodes from 2.3 to 1.3 mm at 200 V. The oil concentration on the membrane surface is also decreased by 72.3% as a result of applying the electric field while it is decreased by 19.2% when the electrodes distance is decreased from 2.3 to 1.3 mm at 200 V.

A network science-based k-means++ clustering method for power systems network equivalence

Network equivalence is a technique useful for many areas including power systems. In many power system analyses, generation shift factor (GSF)-based bus clustering methods have been widely used to reduce the complexity of the equivalencing problem. GSF captures power flow on a line when power is injected at a node using bus to bus electrical distance. A more appropriate measure is the one which captures what may be called the electrical line distance with respect to a bus termed as relative bus to line distance. With increase in power transactions across different regions, the use of relative bus to line distance becomes appropriate for many analyses. Inspired by the recent trends in network science on the study of network dynamics based on the topological characteristics of a network, in this paper, we present a bus clustering method based on average electrical distance (AED). AED is independent of changes in location of slack bus and is based on the concept of electrical distance introduced in the context of molecular chemistry and pursued later for applications in social and complex networks. AED represents the AED from a bus to buses of the transmission line of interest. We first propose an AED-based method to group the buses into clusters for power systems network equivalence using k-means clustering algorithm integrated with silhouette analysis. One limitation of this method is that despite its speed, sometimes it may yield clusters of inferior quality compared to the optimal solution. To overcome this limitation, we next present our improved clustering method which incorporates a seeding technique that initializes centroids probabilistically. We also incorporate a technique in our method to find the number of clusters, k, to be given as input to our clustering algorithm. The resulting algorithm called AED-based k-means++ clustering method yields a clustering that is O(logk) competitive. Our network equivalence technique is next described. Finally, the efficacy of our new equivalencing technique is demonstrated by evaluating its performance on the IEEE 300-bus system and comparing that to the performance of our AED-based method (Sharma et al. in Power network equivalents: a network science-based k-means clustering method integrated with silhouette analysis. In: Complex networks and their application VI, Lyon, France. p. 78–89, 2017) and the existing GSF-based method.

Voltage instability prediction based on reactive power reserve of generating units and zone selection

In this study, a voltage instability prediction algorithm is proposed based on Thevenin impedance matching theorem. This algorithm consists of three important parts: an adaptive network zoning algorithm, the Thevenin-based voltage instability risk predictor (VIRP) and a third-order extrapolation technique. The zoning algorithm, based on the concept of electrical distance, is proposed to divide the main network into several zones after the occurrence of any large event. Each zone consists of some load buses and generating units have the most influences on their voltage stability. The proposed VIRP is defined similarly to the Thevenin indicator multiplied with a contribution factor. This factor is calculated for each zone, based on the lack of the reactive power reserve in its generating units, to increase the predictor value, especially in the proximity of the instability. So, VIRP could reduce the instability detection time with respect to the Thevenin indicator. The further reduction in the instability detection time is obtained by the well known cubic spline extrapolation technique. This function is applied to the values of VIRP to predict the instant of the instability. The proposed algorithm is tested on the modified New England 39-bus test system supplied with the voltage-source converter-high-voltage dc link.

Analysis of Energy Management of Garnesa Electric Car Based Numerical Simulation Modeling

Designing an electric car to compete with ESCC should be guided by Vehicle Construction and Stability. One of the areas to consider when designing at the research and development stage is the Mechanical Mechanical System (Rotational Mechanical System). These systems include, wheels, transmissions (gear connections), electric motor rotors and shafts. The purpose of this study was to determine the effect of vehicle energy management on driver driving strategies during the ESCC competition. This is based on Wheel Mechanical System modeling, Dynamic System Analysis and Free Body Diagram. The method used is based on Numerical Simulation. The data parameters used are based on independent variables and control variables. The independent variable of this study is the angular velocity (V?), linear velocity (v) of the vehicle, friction coefficient value (B), shaft stiffness (K), wheel diameter, gear diameter, wheel mass and moment inertia of the wheel. Control variables is technical regulation of ESCC Urban Concept. This Numerical Simulation Test is to determine the required electrical power, travel time and distance of the vehicle. The results showed that the energy needed by GARNESA electric car with an average speed selection of 9.42 m /s based on a maximum speed of 10.15 m /s and a minimum speed of 8.70 m /s requires the amount of power 248.15 Watt. Travel time is 180 seconds in one lap. The distance obtained is 1357 m. Driving strategy based on average speed of 9.42 m /s consumes less power and the distance obtained will be more far.

A calculation method of electrical distance considering operation mode

An electrical distance calculation method considering operation mode is proposed. Based on line impedance, Phase-angle difference between buses is taken into account to characterize strength of electrical connections. Derivation of electrical distance considering operation mode is introduced. Comparing with traditional impedance electrical distance calculation method, rationality of this method was verified. Electrical distance of IEEE 39 example system is calculated. To explain effect of operating mode on the electrical distance, electrical zone division of power system under different operation modes are compared.

Modelling and design of PID controller for voltage control of AC hybrid micro-grid

<span>The growing demand for power that needs to be remotely transported creates a fast and effective solution of Distributed Energy Resources (DERs) integration. Distributed Energy Resources (DERs) can lessen the electrical and physical distance between load loss and generator, transmission and distribution, and the level of carbon emissions. Such challenges can be overcome by using microgrids, which combine various types of DERs without interrupting the grid operation, allowing the power system to detect and control the errors more efficiently, allowing the shedding load and automatic switching through control algorithms so that blackouts and power restoration times are shortened, enabling either a relevant grid or islanded mode operation, and improving system reliability and flexibility via DERs. This work includes modelling of hybrid AC micro-grid as well as presenting an efficient control technique for micro-grid. In the present work the performance of hybrid AC microgrid system is analyzed in the islanded mode. Photovoltaic system and fuel cell stack are used for the development of microgrid. It also includes microgrid control objectives and the most common problems encountered and their solutions. The employed control technique is able to control the output voltage at a desired and standard value. The control strategies of the hybrid AC microgrid are simulated in MATLAB/SIMULINK.</span>

Study on characteristics of wind power transmission system with series compensation

Renewable energy develops very fast in China, and China has become the largest and fastest growing country of wind and PV power in the world. However, the distribution of the wind/solar energy and load center is disharmonious, with the major wind fields and the solar fields being distributed in the area which is short of load, and making large-scaled, long-distance wind and PV power transmission is imperative. The problem of the stability of the large-scale wind and PV power grid integrated system into the high impedance weak grid is becoming more and more important. In order to shorten the electrical distance for wind power integration, the use of series compensation technology is an economically viable approach. In this study, the characteristics of the wind power transmission system with series compensation are introduced. On the basis of the analysis, the characteristics of the wind power transmission under the series compensation are analysed. Finally, after the wind power base integration, the different impedance characteristics/the order of the impact are studied.

Optical Stark and Zeeman Spectroscopy of Thorium Fluoride (ThF) and Thorium Chloride (ThCl).

Experimentally and theoretically determined magnetic and electric dipole moments, bond distances, and vibrational spacings are used for a comparative study of the bonding in ThF and ThCl. Numerous bands in the visible electronic spectra between 16 400 and 18 800 cm-1 of supersonically cooled molecular beam samples have been detected using medium-resolution (Δν ≈ 0.1 cm-1) 2D spectroscopy. High-resolution (Δν < 20 MHz) field-free, Stark, and Zeeman spectroscopy of the detected [18.6]Ω = 3/2 - X2Δ3/2 band of ThF near 538.4 nm and the [18.2]Ω = 3/2 - X2Δ3/2 band of ThCl near 551.0 nm have been recorded and analyzed. Stark shifts and splitting were analyzed to produce | μ⃗el| values of 1.453(7) D and 0.588(9) D for the X2Δ3/2 and [18.6]Ω = 3/2 states of ThF, respectively, and 2.022(35) D and 3.020(55) D for the X2Δ3/2 and [18.2]Ω = 3/2 states of ThCl. Zeeman splittings and shifts were analyzed to produce ge values of 1.038(4) and 1.079(4) for the X2Δ3/2 and [18.6]Ω = 3/2 states of ThF and 1.130(4) and 1.638(4) for the X2Δ3/2and [18.2]Ω = 3/2 states of ThCl. Analysis of ge values demonstrates that the X2Δ3/2 and [18.6]Ω = 3/2 states of ThF and the X2Δ3/2 state of ThCl are predominately 2Δ3/2 spin-orbit components, whereas the [18.2]Ω = 3/2 state of ThCl is an admixture of 2Δ3/2 and 2Π3/2 spin-orbit components. A molecular orbital description of the ground states is used to rationalize the observed | μ⃗el|values for the ThX (X = F, Cl, O, and S) series and garner insight into the bonding mechanism. The dipole moments in the ground state of ThF and ThCl have been calculated using relativistic coupled-cluster methods. It is demonstrated that the systematic inclusion of electron-correlation contributions plays an essential role in obtaining accurate predictions for the dipole-moment values in ThF and ThCl.

Identifying the Key Transmission Lines Considering the Power Flow Impact Force

A method is proposed for identifying the key transmission lines of a power grid. First, based on the theory of equal phase angle line and electrical distance, the phase angle partition areas are defined to partition the transmission lines. A generalized entropy index of the power flow growth rate is defined to evaluate the distribution of the degree of imbalance of the power flow impact after a transmission line outage. Second, based on the Katz–Bonacich Center theory, an index for evaluating the importance of the location of transmission lines is defined. Finally, the cloud model is used to transform the evaluation data information. The comprehensive evaluation results are presented in the form of cloud maps. The correctness of this method is verified by simulation.

CDF-Based Capacity Estimation Method for Stationary Regenerative Solution in Parallel-Fed DC Urban Subway Transit

The energy consumption of DC urban subway transit (UST) has attracted an increasing amount of attention, and various studies have focused on improving the energy use of USTs by increasing the energy efficiency or reducing the energy consumption. However, the amount of regenerative energy that can be re-utilized and the capacity of the regenerative device for re-utilization have not been extensively discussed. To simply compute the specification of the sustainability improvement facilities for a parallel-fed UST system, this paper proposes current distribution factor (CDF) based analysis that reflects the mobility and power variation of the vehicle loads in UST system. The CDF set are derived based on the electrical distance between the vehicle load and each substation, and the powerflow method with the CDF set provides an intuitive solution to analyze supplied or regenerative power flow in the parallel-fed DC UST system. Based on the actual UST line data, the convergence characteristic of the proposed algorithm was verified and the capacity of the regenerative device was calculated for peak and non-peak headway conditions.

Minimizing Load Shedding in Electricity Networks using the Primary, Secondary Control and the Phase Electrical Distance between Generator and Loads

This paper proposes a method for determining location and calculating the minimum amount of power load needed to shed in order to recover the frequency back to the allowable range. Based on the consideration of the primary control of the turbine governor and the reserve power of the generators for secondary control, the minimum amount of load shedding was calculated in order to recover the frequency of the power system. Computation and analysis of the phase electrical distance between the outage generator and the loads to prioritize distribution of the amount power load shedding at load bus positions. The nearer the load bus from the outage generator is, the higher the amount of load shedding will shed and vice versa. With this technique, a large amount of load shedding could be avoided, hence, saved from economic losses, and customer service interruption. The case study simulation has been verified through using PowerWorld sofware systems. The effectiveness of the proposed method tested on the IEEE 37 bus 9 generators power system standard has demonstrated the effectiveness of this method.

New Method for Zero Potential Non-stop Operation of Distribution Network Based on Injection Current

In the case of live working in the distribution network, a live method of live working that satisfies the requirements for personal safety and power supply reliability needs to be studied, because of the serious safety accidents caused by misuse and weak safety awareness. Based on the zero potential characteristics of the operating point, a new method based on injection current for zero-potential uninterrupted operation in distribution network is proposed. The Floyd algorithm is used to calculate the shortest electrical distance from the live working point to the substation, and the capacitance value of the ground is measured by the resonant grounding system, and the current value injected further to the neutral point is calculated. By regulating the zero-sequence voltage, the neutral point voltage is equal to the difference between the operating phase line voltage drop and the operating phase power supply voltage, ensuring that the operating point voltage is zero. Finally, based on the PSCAD simulation software, the system model is established. The simulation verifies the feasibility of the proposed method by comparing the voltage curves of the working phase.

Exogenous Cost Allocation in Peer-to-Peer Electricity Markets

The deployment of distributed energy resources, combined with a more proactive demand side management, is inducing a new paradigm in power system operation and electricity markets. Within a consumer-centric market framework, peer-to-peer (P2P) approaches have gained substantial interest. P2P markets rely on multibilateral negotiation among all agents to match supply and demand. These markets can yield a complete mapping of exchanges onto the grid; hence, allowing to rethink the sharing of costs related to the use of common infrastructure and services. We propose here to attribute such costs through exogenous network charges in several alternative ways, i.e., uniformly, based on the electrical distance between agents and by zones. This variety covers the main grid physical and regulatory configurations. Since attribution mechanisms are defined in an exogenous manner to affect each P2P trade, they eventually shift the market issue to cover the grid exploitation costs. It can even be used to release the stress on the grid when necessary. The interest of our approach is illustrated on a test case using the IEEE 39 bus test system, underlying the impact of attribution mechanisms on trades and grid usage.

Interaction influence of harmonics in MIDC transmission systems

Owing to the particular distribution of energy and load, the high-voltage direct current transmission system has been greatly developed in China. A number of areas have formed the multi-infeed direct current (MIDC) transmission systems. In MIDC transmission systems, the electrical distance between the inverter stations is close and the coupling effect is strong, therefore, the interaction influence of harmonics is complex. In order to analyse this complex interaction influence, this study first introduces the influence factors multi-infeed influence factors of power (MIIF-Pd) and multi-infeed total harmonic voltage distortion (MITHDu), which are used to describe the interaction influence degree of harmonics between inverter stations. Then based on the Shanghai power grid, a simulation model of the MIDC transmission systems was built in PSCAD/EMTDC, and the interaction influence degree of harmonics in MIDC transmission systems was studied in the case of large disturbance and small disturbance exists in the inverter stations. The results show that the interaction influence of harmonics between inverter stations is related to the electrical distance, the style of disturbance, transmission power and so on. Meanwhile, the disturbance on a commutation bus mainly leads to the increase of the harmonic distortion rate in this inverter station, and has less influence on the other stations.

Research of effects exerted by industrial frequency electromagnetic fields on city areas located near power lines

This paper presents the results of full scale research of electromagnetic fields of power transmission lines of various voltage classes at various distances from residential buildings along the full height from ground surface. The empirical correlation graphs of electric and magnetic field intensities versus distances from electric power lines at 1, 1.8, 3 m heights have been developed for the voltage classes of 110; 220; 500 kV, including empirical correlation graphs of electric and magnetic fields intensity versus height from ground at the sanitary protection zone lines and in uptown areas. A nomographic chart has been proposed, which is necessary to improve the electromagnetic safety of construction sites near power lines.

Analysis on the fault characteristics of three-phase short-circuit for half-wavelength AC transmission lines

Half-wavelength AC transmission (HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the three-phase fault characteristics for longer transmission lines are also studied.