Phase Conductors Research Articles

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

EVALUATION OF INFLUENCE OF CORONA ON LIGHTNING SURGE

Lightning overvoltages are caused either by direct strokes to the phase conductor [back flashover] or as a result of strokes to earth very closed to the line which produce. Induced lightning surges. This paper focuses on the simulation of the effect of corona model on different conductors used in transmission line design when subjected to the lightning surge, Kudyan non-linear model corona used for this purpose. Mothematical model of Lightning Surge and analytical representation of current wave shape are evaluated.

Metodología para Determinar la Distribución de Corrientes de Desbalance en Líneas Aéreas de Transmisión de Energía Eléctrica

Las líneas aéreas de transmisión de energía eléctrica presentan un régimen de operación constante y deben soportar esfuerzos mecánicos debido a posibles descargas atmosféricas, en este sentido es importante realizar una adecuada selección de sus conductores de fase y de guarda. Para soportar los esfuerzos mecánicos los conductores de guarda tienen un componente de acero que presenta características eléctricas variables en función de la corriente circulante por el mismo, por otra parte, esta corriente puede determinarse si se conocen los parámetros eléctricos del cable de guarda.En este contexto, el presente documento detalla dos métodos para determinar la distribución de la corriente entre la tierra y el cable de guarda en condiciones de desbalance, con el cual es posible seleccionar los parámetros eléctricos para la modelación adecuada de una línea de transmisión.Los resultados de estos métodos, aplicados en cuatro casos de estudio, se verifican en su respectiva simulación en el software Alternative Transients Program (ATP).

Method for the diagnosis of high-voltage dielectric elements during operation based on dynamic registration of electromagnetic radiation

Complex remote monitoring and the developed non-contact diagnostic device (NDD) allow monitoring the technical condition and revealing the residual life of high-voltage dielectric elements. It is based on non-contact remote periodic measurement of a set of diagnostic parameters (characteristics of electrical discharges emitted by insulators during operation) necessary for a reliable assessment of the operating state of high-voltage dielectric equipment at the moment of operation and determination of its residual life. NDDs are installed on each phase conductor and used to measure diagnostic parameters, followed by computer processing of the accumulated information signals. An analysis of the set of necessary diagnostic parameters makes it possible to form a conclusion on the degree of performance of dielectric elements. The paper considers a method for detecting defective high-voltage insulators using the developed non-contact diagnostic devices by the radio frequency method and assessing the difference in time of arrival of a partial discharge signal.

Analysis of lightning surge influence on ukrainian electric network power lines

The article discusses the impact of lightning surges on overhead lines. The possible effects of lightning in different elements of the overhead lines. Proposed solutions to the problems that arise as a result of a lightning strike to the overhead line. Provided that the source of the lightning overvoltage is the natural electricity of the thunderstorm clouds, which in the form of lightning to hit targets on the ground. It is shown that the wave surge occurring in the current-carrying parts when lightning strikes, distributed, penetrating into the windings of transformers, machines, affecting the insulation lines and equipment. The time of exposure to atmospheric overvoltage is very small (from a few to hundreds millionths of a second), but the magnitude of these overvoltages in the absence of special measures of protection may reach millions of volts. It is proved that the main danger for the line is a direct lightning strike to the phase conductor, with subsequent overlap of insulation from over-voltages that occur at the same time. After the end of the lightning current pulse in the overlap remains the leading channel with the gas, which had not deansoffice, which under the action of operating voltage may continue to leak current of industrial frequency. In the process of elimination of the fault line caused by lightning, consumed the life of the switches; transformers and other network equipment are subjected elektrodynamik and thermal action of short circuit currents. A significant part of the circuit is followed by the development of the accident that requires a trip line for a long time with the disruption of the normal supply. The probability of a storm off of a line depends on many factors: the intensity of storm activity in the areas along the highway line, the nominal voltage of the network, its design, material of supports etc. Shown that the effectiveness of lightning protection is determined separately for the estimated cases of damage of the line. The proposed actions, determining the effectiveness of lightning protection is calculated separately for cases of damage and which is capable of preventing direct lightning strikes to the protected objects and to organize the flow of lightning currents at a safe way. Define a single space lines, which require additional protection measures.

The influence of organic binders and their decomposition products on the microstructure and thermoelectric properties of conductive materials based on si3n4 with transitional metal carbides additives

The object of research is the formation of the functional zone of a multicomponent ceramic composite based on refractory anoxic compounds. One of the most problematic points is the determination of influence of the type of binder on the formation of the functional zone of the device.During the study, the industrial powders of silicon nitride β – Si3N4 of the Baku Powder Metallurgy Plant (Azerbaijan) and hafnium and zirconium carbides of the Donetsk Chemical Reagents Plant (Ukraine) were used. The homogenization and grinding of the charge was carried out in a planetary mill of the Fritsch type (drum and Si3N4 balls) for 40 min. in ethyl alcohol. The concentration of the inclusion phase conductor in the composite thermoelectrodes was 5–40 %. The carboxymethyl cellulose compound in combination with a plasticizer, glycerol or rubber, was used as a binder for this method. Samples were made in the form of plates 100×7×6 mm. The investigated samples of nitro silicon composite materials were obtained by hot pressing of the prepared ceramic tapes using the induction method of heating the mold.It has been found that in case of the rubber-containing samples with a resistive HfC additive, the weight loss increases in proportion to the HfC concentration up to the additive concentration of 27 %, while the further HfC concentration increase causes the decline of weight loss. When using cellulose gum as a binder, the weight loss decreases by about 1.3–1.6 times; the regularities of weight loss changes depending on the HfC concentration remain the same. It has been shown that the modulus of thermal electromotive force was higher in case of fine composites than in case of coarse ones for all concentrations. The maximum thermal emf value reached 120 μV/deg in the subthreshold zone of the additive concentration. In the suprathreshold zone the maximum thermal emf value reached 60 μV/deg for the fine-grained composite and 30 μV/deg for the coarse-grained one. It has been proved that composites without a binder differ not by the typical course of dependency between the additive concentration and the resistivity, while the thermal emf of these composites equals zero with accuracy up to experimental error.

Anti‐icing measures in the Italian power system

Despite the good operating results of passive anti-icing devices installed by the Italian transmission system operator (TSO) on high-voltage overhead lines (OHLs), the increasing number and consequences of wet snow events have prompted consideration of other anti-icing measures. In particular, attention focuses on the thermal approach, which is intended to achieve – before, or in the early stage of wet snow events – the anti-icing current in OHL phase conductors where snow sleeve formation is foreseen. The authors carried out a specific anti-icing study with reference to a 132 kV critical path in an area of the Apennines, with simulation results illustrated in this study. Anti-icing measures investigated were (i) load shifting actions and (ii) insertion of shunt reactors used as ballast loads. The results show that shunt reactors are the most effective anti-icing measure. The main disadvantage of this innovative solution is the degradation of voltage regulation in the area. However, this downside can be limited by combining the insertion of reactors with control of autotransformers under load tap changers. Similar results are obtained from analyses of other critical areas. As a result of these findings, the Italian TSO is now undertaking the installation of the first ballast reactors.

Utilization of Underbuilt Shield Wires to Improve the Lightning Performance of Overhead Distribution Lines Hit by Direct Strokes

The improvement of the lightning performance of overhead distribution lines, hit by direct strokes, is investigated considering the use of additional shield wires beneath the phase conductors. The frequency-domain theory of multiconductor transmission lines with periodical grounding is adopted permitting a rigorous evaluation of the phase and shield wire currents and of the overvoltages across insulators. These can be minimized by careful positioning of the underbuilt shield wires. A sensitivity analysis on the overvoltages is conducted by varying either the position of the underbuilt shield wires and the grounding impedance.

Investigation of an Insulator Flashunder in an 150 kV OTL of the Power System of Crete

Overhead Transmission Lines (OTLs) are used in Power Systems to carry High Voltage between substations, usually over long distances. Faults in OTLs are bound to happen and thus locating and coping with them is an important aspect of OTL’s operation and maintenance. These faults may be of temporary or permanent nature, with certain types of faults progressing over time from the first category to the second. Local weather may also have a direct effect on the occurrence of faults resulting to puzzling events. A special category, often complex in nature, is insulator faults. Insulators are used in OTLs to support phase conductors while not allowing current to flow through the tower’s body to the ground. Traditional ceramic insulators used materials such as porcelain and glass as insulation, but in the last decades composite insulators with two insulating parts (a glass core/rod and a rubber housing), have also known great use mainly due to their low weight and their capability to withstand pollution. However, they are subjected to certain faults unique to them, such as flashunders. Flashunder is a term commonly used lately to describe faults that are related to the rod/housing interface of composite insulators. Such faults are rather difficult to locate as the electrical discharge does not create an easily visible trace (as in the case of flashovers) or a permanent mechanical fault (as in the case of brittle fractures). Such a fault occurred for the first time in the Transmission System of Crete in 2019 and this paper follows and discusses the incident and the experience gained.

Quality Evaluation of Voice Transmission Using BPL Communication System in MV Mine Cable Network

This article presents results of a quality evaluation study, considering voice transmission in a 6 kV medium voltage cable network using the BPL (Broadband over Power Line) communication system. The tests are carried out under real mining conditions for the selected power cable without voltage, earthed at both sides. Such a method of monitoring work conditions is of great importance, especially during a disaster. Power cables are potentially resistant to mechanical damage and, thus, ensure continuity of transmission, also, in cases of electricity stoppage and partial damage (interruption) of the phase conductors. The voice transmission quality is tested for a relatively low bitrate of 8 kbps–48 kbps using both induction and mixed induction-capacitive coupling with the power cable. Such a solution should provide both reliable and high-quality services, considering clear and understandable voice messages to people. The quality evaluation is carried out on a group of 15 people aged between 25–35 years old. The tested signal samples consist of voice messages in British English, German, and Polish. On the basis of the investigated results, respective conclusions are formulated.

Distributed temperature sensing in OPGW with multiple optical fibres

The ampacity of a material is defined as its maximum electrical current capacity. In an overhead transmission line, it is related to the maximum sag that does not compromise its safe operation. As the sag depends on the conductor's temperature, with this parameter it is possible to estimate its ampacity, increasing the efficiency of the electrical system via real-time energy dispatch management. With the Brillouin backscattering phenomena, the distributed temperature measurement in the fibre inside the optical ground wire (OPGW) or optical phase conductor is possible. However, it is common for overhead power transmission lines to be composed by more than one optical fibre. A calibration algorithm was developed to enable the application of a distributed temperature sensing equipment to monitor the temperature of an OPGW with more than two different fibres. The 230 kV Ibipora-Londrina Transmission Line was used as a case study, being approximately 20 km long and composed of three different fibres spliced in series along with its extension. Through comparison with calibrated sensors, the technique and algorithm were validated. It was possible to characterize the system and perform the temperature monitoring with a spatial resolution of 1 m and amplitude error of less than 6°C.

Electrical Model of Phase-to-Woodpole Bird Electrocution

The electrocution of large birds such as eagles and vultures when making simultaneous contact between a phase conductor and the top of a pole on medium voltage woodpole distribution lines is addressed. System (phase-to-phase) voltages of 11 kV, 22 kV and 33 kV are covered. This phenomenon has been investigated by measurement of the resistance of poles used in the field, as well as measurement of the impedance of recently deceased birds. This has previously been used to compile a simple electrical model for 22 kV systems. This paper compiles a detailed model that is used to estimate the risk posed to large birds by this mode of electrocution for all three voltage levels. The results show that only a few scenarios exist whereby a bird may be at risk, which ties in with field experience. Details of how the wood and bird resistance was measured are also included, as are details of calculations performed.

Evaluation of a Direct Lightning Strike to the 24 kV Distribution Lines in Thailand

This paper evaluates the effect of a lightning strike directly on the 24 kV distribution lines in Thailand, where such strikes are one of the main causes of power outages. The voltage across the insulator, and the arrester energy absorbed due to the lightning, need to be analyzed for different grounding distances of the overhead ground wire, ground resistance, lightning impact positions, and lightning current waveforms. Analysis and simulations are conducted using the Alternative Transients Program/Electromagnetic Transients Program (ATP/EMTP) to find the energy absorbed by the arrester and the voltages across the insulator. The results indicate that when surge arresters are not installed, the voltage across the insulator at the end of the line is approximately 1.4 times that in the middle of the line. In addition, the ground resistance and grounding distance of the overhead ground wire affect the voltage across the insulator if the overhead ground wire is struck. When surge arresters are installed, a shorter grounding distance of the overhead ground wire and a lower ground resistance are not always desirable; this is because they reduce the back-flashover rate and the voltage across the insulator if lightning strikes the overhead ground wire. However, lightning strikes to the phase conductor result in high arrester energy and the possibility that the arrester will fail. Furthermore, the tail time of the lightning waveform is a significant variable when considering the energy absorbed by the arrester, whereas the front time is important for the voltage across the insulator. In case lightning strikes directly on the connected point between the overhead lines and the underground cables, the distribution line system is protected only by the lightning arrester at the connection point. The overvoltage at the connection point is lower than the basic impulse level at 24 kV of 125 kV, but the overvoltage at the end of the cable is still more than 125 kV in case the cable is longer than 400 m. When the distribution line system is protected by the lightning arrester at both the connection point and the end of the cable, it results in overvoltage throughout the cable is lower than the critical flashover of insulation. This method is the best way to reduce the failure rate of underground cables and equipment that are connected to the distribution line system.

Asymmetrical Modes of Outdoor Lighting Lines

Asymmetrical modes of the outdoor lighting network can be caused by disconnecting of a part of the luminaires in order to electrical energy savings at night; also – by asymmetry of voltage in power points. The possible alternative symmetric modes of energy saving to replace the incomplete-phase operation of the line have been analyzed. Calculations of various symmetric and asymmetric modes of the lighting line were carried out without taking into account and taking into account high harmonics up to the 39th one. Calculations have been performed with the programs of MathCad software. As light sources, in the calculations the widely used luminaries with high-pressure sodium arc lamps connected through electromagnetic start-up equipment were considered. Such luminaries are sources of high harmonics, and they distort the sinusoidal voltage. The values of currents, power, power loss, voltage drop in all areas of the lighting line, the voltage at the terminals of the lamps for each phase (operating parameters) are determined. The diagrams of the voltage distribution at the points of the lighting line are plotted for the considered modes of operation. The annual electric power consumption of the lighting line has been calculated for different variants of operation, and the obtained results have been compared. When refusing to disconnection of part of the luminaires at night and using a smooth transition to a lower voltage (symmetrical) at a power point or using two-stage ballast devices, uneven illumination appears less when the level of electricity consumption is comparable. The presence of voltage asymmetry at the power point, as well as the disconnection of one phase, leads to an increase in currents, power losses and voltage. The current in the zero working conductor can exceed the currents in the phase conductors (when calculated taking into account the higher harmonics). Accounting for higher harmonics allows one to determine the operating parameters more accurately, on the basis of which the electricity power consumption can be estimated.

The Spatial Distribution of Electric Field as a Unifying Idea in Transmission Line Design

It is shown that the most important electrical design criteria for long (i.e., stability limited) high voltage overhead transmission lines operating at a given voltage are all related to the spatial electric field distribution between phase conductors. Hence, when designing a long transmission line, a change in one design parameter necessarily causes changes in the others. It is shown how an understanding of these relationships can lead to insight into the design and to the tradeoffs that must be made in designing these transmission lines. More specifically, a more spatially uniform electric field implies an increased power capacity for long transmission lines but also reduces the critical flashover voltage and increases the capacitance per unit length.

Nonintrusive Energy Meter for Nontechnical Losses Identification

We present in this paper a method and apparatus for nonintrusive measurement of active energy in low-voltage ac installations. In the proposed method, the active power is calculated from the voltage and current waveforms, and the phase shift between them. No voltage amplitude measurement is required since the nominal voltage of the ac installation is considered as the actual voltage. This approach bypasses the main disadvantage of capacitive ac voltage probing: low accuracy in amplitude measurements due to variations on the sensor coupling capacitance. The energy meter that implements the technique is composed of a commercial nonintrusive current sensor (clamp-on current transformer) and a contactless capacitive voltage sensor—designed to measure the voltage phase and waveform. The voltage sensor includes a shield to isolate it from external electric fields, making the energy meter suitable for applications in polyphase systems. The developed energy meter does not require on-site calibration, galvanic contact to the phase conductors, neither electrical circuit opening, allowing for quick, safe, and easy installation on overhead service drop line. Due to these characteristics, it can be used by electricity distribution companies in the preinspection of consumer units suspected of fraud. Experimental results proved that the developed energy meter is insensitive to the characteristics of cables (width and insulation), external electrical fields, as well as to the voltage sensor capacitance variations. The error of the active energy measurement under real condition in a two-phase installation was 1%.

Analysis of discharge energy on surge arrester configurations in 132 kV double circuit transmission lines

Surge arrester has been proven to be the most effective application to provide optimum lightning protection for the transmission line. Thus, many works on optimizing lightning protection for transmission line have been conducted since the past. However, works on minimizing double circuit outages and surge arrester physical properties during transient overvoltages are less likely to be found. Therefore, in this work, several surge arrester configurations installed on a 132 kV double circuit transmission line were modelled using EMTP-RV to investigate their capability to withstand current and energy discharged by lightning strokes during back flashover phenomena. These configurations were then compared to determine the most effective protection design based on the actual tripping pattern recorded by the lightning detection system (LDS) in Malaysia. The selection was made by considering arresters’ discharge energy due to variation in tower footing resistance, current magnitude, power frequency voltage, lightning tail time and front time, number of towers and span length. It was found that double circuit transmission line tripping can be completely eliminated by installing surge arresters at each phase conductor of one circuit. The selected arresters configuration provides sufficient lightning protection to the transmission line and complies with the discharge energy capability requirement specified by the utility company in Malaysia, of 5.1 kJ/kV for maximum continuous operating voltage (MCOV).

Review on fiber-optic sensing in health monitoring of power grids

Fiber-optic sensing technology is best adapted to health monitoring and evaluation of power grids because of its immunity of electromagnetic interference, capabilities of multiplexing and distributed sensing, and tolerance to harsh environments. We review key fiber-optic sensing technologies, including fiber Bragg gratings, fiber-optic interferometers, optical time domain reflectometries, and their applications in three main parts of power grids, transformers, power towers, and overhead transmission lines, during the past 20 years. In particular, optical fiber composite overhead ground wire and optical phase conductor applied in power grids are the areas of great potential to go further. The perspectives of an intelligent fault diagnosis subsystem for power grids based on a fiber-optic sensing network are discussed, and related on-going work is described. The review shall be of benefit to both engineers and researchers in power grids and fiber-optic sensing.

Experimental measurements for evaluation of the network throughput of the RC4 channel in the in-home PLC network

Abstract For the expansion of in-home PLC networks, it is necessary to have a detailed knowledge of the PLC transmission channel properties. This contribution shortly discusses theoretical characteristics of the RC4 reference channel. A main part is focused on the network throughput and on the interphase PLC signal liaising presented in the RC4 reference channel for higher frequencies than 10 MHz. For evaluation of considered transmission parameters, experimental measurements related to various noise sources and to interactions between different phase conductors are realized in the real in-home PLC network.

Investigation of Var Compensation Schemes in Unbalanced Distribution Systems

Distributed rooftop photovoltaic (PV) generators prospered distributed generation (DG) in recent years. Certain randomness of rooftop PV connection may lead to significant PV power imbalance across three phases, especially in low‐voltage distribution systems. Due to interphase line coupling, traditional Var compensation methods which typically have competent voltage regulation performance may become less effective in such PV imbalance scenarios. In this paper, the limitation of traditional Var compensation methods in voltage regulation with unbalanced PV power integration is demonstrated and comprehensively analyzed. After describing the voltage regulation challenge, based on the voltage sensitivity analysis, it is revealed that PV power unbalanced level together with equivalent mutual impedance among phase conductors has a significant impact on the effectiveness of traditional Var compensation methods on voltage regulation. On this basis, to improve the performance of voltage regulation methods, some suggestions are proposed for both current system operation and future distribution system planning. Numerical studies demonstrate the effectiveness of the proposed suggestions. Future rooftop PV integration in LV systems can benefit from this research.