Phase Conductors Research Articles

Secured wired BPL voice transmission system

Designing a secured voice transmission system is not a trivial task. Wired media, thanks to their reliability and resistance to mechanical damage, seem an ideal solution. The BPL (Broadband over Power Line) cable is resistant to electricity stoppage and partial damage of phase conductors, ensuring continuity of transmission in case of an emergency. It seems an appropriate tool for delivering critical data, mostly clear and understandable voice messages. This paper describes such a system that was designed and evaluated in real-time operating conditions. It involved a two-way transmission of speech samples in American English and Polish. The efficiency of the designed solution was evaluated in the subjective study on a group of 15 people.

Determination of the Operating Temperature of the Gas-Insulated Transmission Line

Gas-insulated lines (GILs) have been increasingly used as high-current busducts for high-power transmission. Temperature is one of the most important factors affecting the performance and ampacity of GILs. In this paper, an analytical method was proposed to determine the temperature of a three-phase high-current busduct in the form of a single pole GIL. First, power losses in the phase conductors and enclosures were determined analytically with the skin, and proximity effects were taken into account. The determined power losses were used as heat sources in thermal analysis. Considering the natural convection and radiation heat transfer effects, the heat balance equations on the surface of the phase conductors and the screens were established, respectively. Subsequently, the temperature of the phase conductors and the enclosures were determined. The validation of the proposed method was carried out using the finite element method and laboratory measurements.

Lightning Performance and Economic Analysis of an Overhead 88 kV Power Delivery Network with Enhanced Protective Systems

Earthing and protective devices such as line surge arrestors (LSAs) play an important role in areas with high lightning occurrence for overhead HVAC lines’ performance. A lightning stroke of high magnitude can lead to back flash-overs, and the resultant power surge on the phase conductor can cause instigate the line breaker operating to extinguish the power surge. This operation of the protective devices leads to consumer interruptions on the network, a loss of production, and negatively affects the economy. Studies have shown that reducing an earthing system’s values, which itself is costly, may not be sufficient to prevent back flashover and the associated customer production cost loss. A code was developed to determine the possibility of back flashover and the cost of various earthing schemes utilizing the MATLAB software analysis tool. This paper determines the possibility of a back flashover for various combinations of lightning strokes and earthing profiles. Tower Footing Resistances as low as 9.8 Ω can cause back flashover, provided the lightning stroke exceeds 12 kA. Furthermore, the paper presents and discusses an innovative hybrid power line protection scheme, which estimates and considers the high cost associated with establishing an earthing system; it examines the impracticality of re-engineering an earthing scheme for implementation and results obtained by the inclusion of lightning surge arrester’s (LSA). The cost-saving resulting from dips is also established over 25 years for an 88 kV line, and the breakeven point is established. The results showed that the best scenario would be to reduce the tower footing resistance to 29.1 Ω and install 11 LSA per phase.

On the Influence of Dielectric-Coated Conductors on the Performance of Three-Phase Compact Distribution Lines Against Indirect Lightning Strikes

This article presents an investigation on the performance of a three-phase compact distribution line against nearby lightning strikes. It is shown that neglecting the insulating layer that surrounds the phase conductors as usually done in this type of study does not significantly change voltages induced from phase to ground, but can have some effect on voltages induced between phase and messenger, which are the ones that effectively stress the insulation. However, the observed differences are strongly minimized if the usual practice of grounding messenger and neutral in regular intervals of less than 200 m is considered. This is confirmed by a Monte-Carlo-type study that shows that the failure rate of the line is not affected by the inclusion of the insulating layer that surrounds the phase conductors in practical conditions.

Experimental, analytical and numerical analysis of voltage distribution along the cap-and-pin insulators

This paper deals with the experimental, analytical and numerical analysis of voltage distribution along the cap-and-pin insulators. Five different insulators strings are analyzed, consisting of two, three, four, five and six cap-and-pin U40BL glass disc insulators. Experimental measurements are performed in the high voltage laboratory at the Faculty of Electrical Engineering East Sarajevo. Measurement of the voltage distribution along the disc insulators is performed by using measuring sphere gap. Analytical calculations are performed by using mathematical model which considers parasite self-capacitances of disc insulators, as well as their parasite capacitances to the earth and to the phase conductor. Calculations of the parasite capacitances values are performed and optimum values which lead to the minimum difference between measured and calculated results are suggested. Numerical analyses of the non-linear voltage distribution are performed by using electrostatic field model in software Comsol Multyphisics. 2D axisymmetric models of the cap-and-pin insulators are developed. Despite the measuring configuration is not suitable for numerical analysis, relatively good agreement between the measured results and results calculated by using specialized software are achieved.

Circuit Model of Vertical Double-Circuit Transmission Tower and Line for Lightning Surge Analysis Considering TEM-mode Formation

The electromagnetic fields, which are produced by lightning currents flowing into a transmission tower and into overhead ground wires, spherically expand with time, and propagate as non-transverse electromagnetic (TEM) waves at least within the round trip time of the traveling wave along the tower. In this paper, a distributed-parameter line model of a vertical double-circuit transmission tower with an overhead line struck by lightning is composed considering the non-TEM characteristics. The surge impedances of the tower, ground wires, and phase conductors increase with time and reach their TEM-mode or steady state values with time constants determined from the configuration. In addition, the significant wave attenuation along the tower is included in the circuit model according to the propagation characteristic determined by the tower configuration. The virtual inductive grounding impedance or damping circuits for approximately representing the wave attenuation is no longer needed. The proposed model is applied to four types of transmission towers. Waveforms of voltages across insulator strings computed by the finite-difference time-domain method, which are regarded as the reference, are well reproduced by the proposed model. Computation efficiency is drastically improved by the proposed model comparing to the numerical electromagnetic field analysis.

ELECTROMAGNETIC INTERFERENCE (EMI) PRODUCED BY HIGH VOLTAGE TRANSMISSION LINES

Electromagnetic interference in high voltage transmission lines has been an interest topic due to its effect on human health, plants, electrical and telecommunication equipment. Extremely high voltages (EHV) in transmission lines are reasons of electrostatic effects, while short circuit currents and line loading currents are responsible for electromagnetic effects. The aim of this research is to analyze electromagnetic fields in high voltage transmission lines in theoretical study and calculating its level in overhead T. L and therefore estimated the EMI produced, by employing a mathematical model of 230 KV tower double circuit configurations of high voltage transmission lines. The calculation is based on computer aided analysis (CAA) by using fields and corona effects software (FACE). It's found that the overhead power lines of general frequency (50 Hz) generates a highly intense magnetic field, the electromagnetic fields depends on the distance from sources and the type of line configuration. They decrease as the distance increase from the tower and conductors and increase with a high current. The strength of an electric field is proportional to the voltage of the line and the magnetic field strength is proportional to the current in the high voltage transmission lines. Distribution line with a high current load may produce a magnetic field that is as high as those produced by some high voltage transmission lines. Some techniques of reduction of the effects of electromagnetic interference have suggested such as rearrangement conductors of transmission line, and distance from phase conductor and grounding system. The study recommended to keep safety distance operation in high voltage transmission lines with the necessity for engineer to take into account the effect of electromagnetic interference in the design stage of high voltage transmission power system, and to avoid any addition cost may be occur due to neglected effects of electromagnetic interference that produces by high voltage transmission lines

Thermal Distortion of Signal Propagation Modes Due to Dynamic Loading in Medium-Voltage Cables

Temperature variation from dynamic cable loading affects the propagation characteristics of transient signals. The distortion of modal signal components as a function of temperature in a three-phase medium-voltage cable is investigated. The temperature influence arises mainly through the complex insulation permittivity, which has a non-linear relationship with temperature. Near the maximum operating temperature of the cross-linked polyethylene insulation, the propagation velocity increases by 0.56% per degree centigrade but is an order of magnitude less sensitive at ambient temperature. The paper presents modeling results based on cable impedance and admittance matrices obtained from electromagnetic field simulation, taking into account the time-varying temperature distribution in the cable cross-section. The results are verified by applying Rayleigh–Schrödinger perturbation analysis. In the time domain, signal patterns shift when the modal propagation velocities change upon cable loading. Moreover, separation of degenerate modes is observed when the cable phase conductors carry an unbalanced current. The perspectives for exploiting the temperature dependency of signal propagation for pinpointing cable defects and for dynamic rating of underground power cables are discussed.

Optimized Protection of Pole-Mounted Distribution Transformers against Direct Lightning Strikes

Direct lightning strikes on overhead phase conductors result in high overvoltage stress on the medium voltage (MV) terminals of pole-mounted transformers, which may cause considerable damage. Therefore, introducing an efficient protection strategy would be a remedy for alleviating such undesirable damages. This paper investigates the optimized protection of MV transformers against direct lightning strikes on the phase conductors. To this end, first, the impacts of grounding densities (number of grounded intermediate poles between every two successive transformer poles) on the probability of overvoltage stress on transformer terminals are investigated. Then, the implications of guy wire, as a supporting device for ungrounded intermediate poles, on reducing the overvoltage stress on transformers, are studied. Finally, the role of a surge arrester in mitigating the overvoltage stress of non-surge-arrester-protected transformer poles is scrutinized. The investigations are conducted on a sample MV network with 82 wood poles comprising 17 pole-mounted transformers protected by spark gaps. To provide in-depth analysis, two different poles, namely creosote- and arsenic-impregnated poles, are considered under wet and dry weather conditions. A sensitivity analysis is performed on grounding distances and on a combination of guy wire and grounded intermediate poles while taking into account soil ionization. The results provide a clear picture for the system operator in deciding how many grounded intermediate poles might be required for a system to reach the desired probabilities of transformers experiencing overvoltage stress and how the surge arrester and guy wires contribute to mitigating undesirable overvoltage stress.

A complete state estimation algorithm for a three-phase four-wire low voltage distribution system with high penetration of solar PV

Low Voltage Distribution Grids (LVDGs) become highly unbalanced due to the advent of single-phase solar PV plants. As a result, the voltage and current levels of the neutral conductor show a significant increase. Therefore, monitoring of the entire state of the network is essential. However, the existing state estimation algorithms estimate voltage states of the phase conductors while ignoring the state of the neutral conductor. This paper presents a novel approach to estimate the complete state of the LVDGs. A novel state reduction method was introduced to model the three-phase four-wire feeder line using a 3×3 admittance matrix, which incorporates the neutral coupling effect on phase conductors. Next, the reduced admittance matrix together with the linear approximations of active and reactive power functions were combined to formulate the Low Voltage-Linear State Estimation (LV-LSE) algorithm. Finally, the performance of LV-LSE algorithm was analyzed for different measurement uncertainties, scales of line lengths of the network, and data-loss conditions. Results show that, for all the cases, LV-LSE algorithm together with the proposed reduction method can estimate voltage states with an average maximum voltage magnitude error of less than 4.32×10-3 pu and current states with an average maximum current magnitude error of less than 1.81×10-3 pu.

THE EFFECTIVENESS OF ACTIVE SHIELDING OF MAGNETIC FIELD WITH CIRCULAR SPACE-TIME CHARACTERISTIC AND WITH DIFFERENT SHIELDING COILS SPATIAL POSITIONS

Aim: The synthesis, computer modeling and field experimental research of two degree of freedom robust two circuit system of active shielding of magnetic field with circular space-time characteristic, generated by overhead power lines with «triangle» type of phase conductors arrangements and with different shielding coils spatial positions for reducing the magnetic flux density to the sanitary standards level and to reducing the sensitivity of the system to plant parameters uncertainty. Methodology: The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis of the Maxwell equations quasi-stationary approximation solutions. The game decision is based on the stochastic particles multiswarm optimization algorithms. The initial parameters for the synthesis by system of active shielding are the location of the overhead power lines with respect to the shielding space, geometry and number of shielding coils, operating currents, as well as the size of the shielding space and magnetic flux density normative value, which should be achieved as a result of shielding. The objective of the synthesis is to determine their number, configuration, spatial arrangement and shielding coils currents, the control systems parameters as well as the resulting of the magnetic flux density value at the shielding space. Results: Computer simulation and field experimental research results of two degree of freedom robust two circuit system of active shielding of magnetic field, generated by overhead power lines with «triangle» type of phase conductors arrangements and with different shielding coils spatial positions are given. The possibility of initial magnetic flux density level reducing and system sensitivity to the plant parameters uncertainty reducing is shown. Originality: For the first time the synthesis, theoretical and experimental research of two degree of freedom robust two -circuit t system of active shielding of magnetic field generated by single-circuit overhead power line with phase conductor’s triangular arrangements and with different shielding coils spatial positions carried out. Practical value: Practical recommendations from the point of view of the practical implementation on reasonable choice of the spatial arrangement of two shielding coils of robust two-circuit system of active shielding of the magnetic field with circular space-time characteristic generated by single-circuit overhead power line with phase conductor’s triangular arrangements are given.

The Effectiveness of Active Shielding of Magnetic Field with Circular Space-Time Characteristic and with Different Shielding Coils Spatial Positions

Aim: The synthesis, computer modeling and field experimental research of two degree of freedom robust two circuit system of active shielding of magnetic field with circular space-time characteristic, generated by overhead power lines with «triangle» type of phase conductors arrangements and with different shielding coils spatial positions for reducing the magnetic flux density to the sanitary standards level and to reducing the sensitivity of the system to plant parameters uncertainty. Methodology: The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis of the Maxwell equations quasi-stationary approximation solutions. The game decision is based on the stochastic particles multiswarm optimization algorithms. The initial parameters for the synthesis by system of active shielding are the location of the overhead power lines with respect to the shielding space, geometry and number of shielding coils, operating currents, as well as the size of the shielding space and magnetic flux density normative value, which should be achieved as a result of shielding. The objective of the synthesis is to determine their number, configuration, spatial arrangement and shielding coils currents, the control systems parameters as well as the resulting of the magnetic flux density value at the shielding space. Results: Computer simulation and field experimental research results of two degree of freedom robust two circuit system of active shielding of magnetic field, generated by overhead power lines with «triangle» type of phase conductors arrangements and with different shielding coils spatial positions are given. The possibility of initial magnetic flux density level reducing and system sensitivity to the plant parameters uncertainty reducing is shown. Originality: For the first time the synthesis, theoretical and experimental research of two degree of freedom robust two -circuit t system of active shielding of magnetic field generated by single-circuit overhead power line with phase conductor’s triangular arrangements and with different shielding coils spatial positions carried out. Practical value: Practical recommendations from the point of view of the practical implementation on reasonable choice of the spatial arrangement of two shielding coils of robust two-circuit system of active shielding of the magnetic field with circular space-time characteristic generated by single-circuit overhead power line with phase conductor’s triangular arrangements are given.

MITIGASI KEGAGALAN INSULATION UDARA DI ZONA RIGHT OF WAY (ROW) PADA KETINGGIAN POHON PARASERIANTHES-FALCATARIA

Abstract
 Total blackouts (on August 04, 2019) in the Special Capital Region of Jakarta have an impact to daily the economy and the cessation of MRT (Mass Rapid Transit) public transportation services, as well as public communication systems. The determination of the value of the voltage gradient for knowing of the black-out was used the method of analyses to the exposure of the electric fields under the Extra High Voltage (EHV) transmission lines 500 kV, at the span of the tower T.434 and T.435 in Malon hamlet, Gunung-Pati village, districts of Gunung-Pati, Semarang city - central Java. The analysis of the electric field exposured has been carried out in a simulation using a Matlab softwere by solving the simultaneous equations model that corresponding to the tower configuration system and how many conductors were used. The results of the simulation showed that there was a failure of air insulation between phase conductors and the trees of Sengon (Paraserianthes-Falcataria) at a value of voltage gradient of 32 448.10 kV / m, 66 861.13 kV / m, and 33 129.75 kV / m, each were for the lateral distance of 10 m, 12 m, and 14 m from the tower axis T.434 and T.435.
 Keywords: Mitigation, ROW, Paraserianthes-Falcataria, Transmission-lines

Analysis of Metal Oxide Varistor Arresters for Protection of Multiconductor Transmission Lines Using Unconditionally-Stable Crank–Nicolson FDTD

Surge arresters may represent an efficient choice for limiting lightning surge effects, significantly reducing the outage rate of power lines. The present work firstly presents an efficient numerical approach suitable for insulation coordination studies based on an implicit Crank–Nicolson finite difference time domain method; then, the IEEE recommended surge arrester model is reviewed and implemented by means of a local implicit scheme, based on a set of non-linear equations, that are recast in a suitable form for efficient solution. The model is proven to ensure robustness and second-order accuracy. The implementation of the arrester model in the implicit Crank–Nicolson scheme represents the added value brought by the present study. Indeed, its preserved stability for larger time steps allows reducing running time by more than 60 % compared to the well-known finite difference time domain method based on the explicit leap-frog scheme. The reduced computation time allows faster repeated solutions, which need to be looked for on assessing the lightning performance (randomly changing, parameters such as peak current, rise time, tail time, location of the vertical leader channel, phase conductor voltages, footing resistance, insulator strength, etc. would need to be changed thousands of times).

ACTIVE SHIELDING OF MAGNETIC FIELD WITH CIRCULAR SPACE-TIME CHARACTERISTIC

Aim. The synthesis of two degree of freedom robust two circuit system of active shielding of magnetic field with circular space-time characteristic, generated by overhead power lines with «triangle» type of phase conductors arrangements for reducing the magnetic flux density to the sanitary standards level and to reducing the sensitivity of the system to plant parameters uncertainty. Methodology. The synthesis is based on the multi-criteria game decision, in which the payoff vector is calculated on the basis of the Maxwell equations quasi-stationary approximation solutions. The game decision is based on the stochastic particles multiswarm optimization algorithms. The initial parameters for the synthesis by system of active shielding are the location of the overhead power lines with respect to the shielding space, geometry and number of shielding coils, operating currents, as well as the size of the shielding space and magnetic flux density normative value, which should be achieved as a result of shielding. The objective of the synthesis is to determine their number, configuration, spatial arrangementand and shielding coils currents, setting algorithm of the control systems as well as the resulting of the magnetic flux density value at the shielding space. Results. Computer simulation and field experimental research results of two degree of freedom robust two circuit system of active shielding of magnetic field, generated by overhead power lines with «triangle» type of phase conductors arrangements are given. The possibility of initial magnetic flux density level reducing and system sensitivity reducing to the plant parameters uncertainty is shown. Originality. For the first time the synthesis, theoretical and experimental research of two degree of freedom robust two -circuit t system of active shielding of magnetic field generated by single-circuit overhead power line with phase conductors triangular arrangements carried out. Practical value. Practical recommendations from the point of view of the practical implementation on reasonable choice of the spatial arrangement of two shielding coils of robust two -circuit system of active shielding of the magnetic field with circular space-time characteristic generated by single-circuit overhead power line with phase conductors triangular arrangements are given.

Closed-Form Expressions for the Estimation of the Minimum Backflashover Current of Overhead Transmission Lines

The minimum backflashover current, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BF</sub> , of typical overhead transmission lines is estimated through ATP-EMTP simulations considering the tower ground resistance and AC voltage phase angle as parameters. Several single- and double-circuit lines are investigated with operating voltage from 66 kV to 765 kV and Basic Insulation Level from 325 kV to 1950 kV. The backflashover rate, BFR, of the investigated lines is obtained using an expression that accurately considers lightning incidence to the line for prospective currents higher than I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BF</sub> ; the relevant CIGRE expression underestimates BFR. BFR can be easily estimated using solely the phase angle values corresponding to zero AC voltage of the phase conductors. Based on the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BF</sub> and BFR results, simple expressions are introduced for the calculation of an equivalent minimum backflashover current as a function of insulator length and tower ground resistance or impulse impedance. These expressions enable straightforward estimation of BFR without the need for time-consuming simulations or laborious analytical methods adopting simplifying assumptions.

Investigasi Kondisi Permukaan Isulator Tegangan Tinggi berbasis Machine Learning TensorFlow

The insulator plays an essential role in preventing the flow of current from the phase conductor to the earth through supporting towers so that the insulation is a significant part of the electrical energy transmission system. Generally, high-voltage insulators are widely used as external plug insulators, for that the performance of insulators is influenced by environmental conditions that indirectly affect the surface condition of the insulators. In this study, a diagnostic tool used in the testing surface of the insulator, which can classify mechanically whether the insulator is good or damaged. The classification method uses TensorFlow Machine learning. Machine Learning is used as a brain in the isolation classification process while TensorFlow functions to store training data and test data in the classification process. The results obtained from this study show the accuracy of classification data is 98%.

Impact of Asymmetry of Over-Head Power Line Parameters on Short-Circuit Currents

&lt;span lang="EN-GB"&gt;This paper analyses the impact of asymmetry of over-head power line parameters on short circuit currents when three-phase fault and phase-to-ground fault occur. The calculation results with consideration of an asymmetry of the power line parameters are confronted with the calculation in accordance with the Slovak standard STN EN 60909 which does not consider asymmetry of equipment parameters in the power system. The calculation of short-circuit conditions was carried out for two types of 400 kV power line towers on which is a considerably different arrangement of phase conductors.&lt;/span&gt;

Methodology and accuracy for non‐invasive detection of switching transient overvoltages from compensation coils connected to power transformers

Transient voltages from (dis)connecting compensation coils near high voltage transformers are studied. Non-invasive sensors are needed in order to exclude any influence by the measurement equipment on the overvoltage magnitude. This study describes results from open-air capacitive sensors as part of a differentiating/integrating measurement system. Its bandwidth (up to 10 MHz) allows to record large detail in the switching events. However, the coupling strengths and the cross-couplings inherent to the use of air capacitive sensors need to be determined. Calibration based on symmetric phase voltages during normal operation supplies part of the information. Three methods are compared to supplement this knowledge for establishing the complete coupling matrix between phase conductors and sensors. One method employs estimates from the system configuration, in particular, its symmetry. The other techniques extract information from fast transient events within the responses for both switching on and off. The decoupled waveforms from different methodologies align within their confidence bounds and predict the maximum overvoltage magnitudes within an accuracy of 5% when employing information from the fast transients. Based on measurements performed on two compensation coils, both tested three times, larger overvoltages occurred during energisation compared to de-energisation with maximum amplitude exceeding three per unit.

Magnetic Field Active Shielding of Overhead Power Lines with Triangular Phase Conductors Arrangements

Magnetic Field Active Shielding of Overhead Power Lines with Triangular Phase Conductors Arrangements