Earth Wire Research Articles

Interaction of Structural Elements in the Overhead Transmission Power Line

The analysis of the changes of tensile forces in conductors and earth wires is performed during their breakage and impact on the towers of overhead power line with a voltage of 330 kV. Based on the results, a mathematical model of a unified cable-stayed rod system consisting of steel towers, conductors and earth wires and insulating elements has been compiled. The system of equations of the model is solved iteratively using the MS Excel spreadsheet processor for various breakage cases. The dependences of tensile forces in conductors and earth wires during their breakage are presented, as well as the forces which correspond to an acting regime on towers in a linear circuit, taking into account the supporting effect of neighboring towers.

Non-contact voltage measurement of residential cables based on internal parameter conversion and centering probe assistance

Existing non-contact voltage measurement technology cannot be applied to residential cables containing neutral wire and earth wire in addition to live wire. A non-contact voltage measurement method of residential cables is introduced in this article. First, an equivalent circuit model of the residential cable measurement based on capacitive coupling is established. In order to solve the problem of uncertain coupling capacitance, which leading to the inability to accurately obtain the voltage amplitude, a calibration method based on internal parameter conversion and centering probe assistance is proposed. This method calibrates the cable voltage through different transfer relationships and sensor outputs, and no known reference excitation is required during calibration. Subsequently, the impact of internal parameters on measurement accuracy are analyzed and selection principles are provided. Through finite element simulation, the influence of metal spring for centering on voltage measurement is analyzed, and the measurement error of non-ideal cables (with eccentricity or ovality) is quantified. A prototype probe and internal parameter conversion circuit have been developed, and parasitic capacitance compensation have been completed. The measurement accuracy of 50 Hz voltage in a certain range (100–300 V) was tested in the laboratory, the maximum relative error of amplitude is −0.89%, and the relative error of phase is 0.68%. Four specifications of residential cables testing were completed, with a maximum relative error of −1.35%. Long- term testing was conducted on the actual field (output voltage of the distribution box), the test results showed that the output was linear, and the relative error were kept around 0.65% after primary calibration.

Study on the Lightning Protection Performance for a 110 kV Non-Shield-Wired Overhead Line with Anti-Thunder and Anti-Icing Composite Insulators

Due to micro landforms and climate, the 110 kV transmission lines crossing the mountain areas are exposed to severe icing conditions for both their high voltage (HV) conductors and shield wires during the winter. Ice accumulation on the shield wire causes excessive sag, which leads to a reduced clearance between earth and HV wires, and could eventually result in tripping of the line due to phase-to-ground flashover. Due to the lack of effective de-icing techniques for the shield wires, removing them completely from the existing overhead line (OHL) structure becomes a reasonable solution to prevent icing accidents. Nevertheless, the risk of exposure to lightning strikes increased significantly after the shield wires were removed. In order to cope with this, the anti-thunder and anti-icing composite insulator (AACI) is installed on the OHLs. In this article, the 110 kV transmission line without shield wire is considered. The shielding failure after installation of the AACIs is studied using the lightning strike simulation models established in the ATP software. The lightning stroke flashover tests are carried out to examine the shielding failures on various designs for the AACIs. Assuming the tower’s earth resistance is 30 Ω, the LWL of back flashover and direct flashover are 630.88 kA and 261.33 kA, respectively, after the installation of AACIs on an unearthed OHL. Due to the unique mechanism of the AACI, the operational voltage level and the height of the pylon have a neglectable influence on its lightning withstand level (LWL). When the length of the parallel protective gap increases from 450 mm to 550 mm, the lightning trip-out rate decreases from 0.104 times/100 km·a to 0.014 times/100 km·a, and the drop rate reaches 86.5%. Therefore, increasing the gap distance for the AACI to provide additional clearance is proven to be an effective method to reduce the shielding failure rates for non-shield-wired OHLs.

고속철도 신호기계실의 접지전류 개선 효과에 관한 연구

Through construction of high-speed railways and railway electrification projects in Korea, individual(or independent) grounding methods were replaced with common grounding methods. Common grounding methods can eliminate potential difference between equipments connected with common grounding wires, but the wires are used as return current paths such as rails. A track circuit cable consists of signal wires and shielding conductors, and connects track circuit devices installed along tracks, transmitters and receivers located in a signal machine room. Shielding conductors at one end of the track circuit cable are connected to the common earth wire, and the conductor at the other end are connected to a grounding terminal of the signal machine room. It was confirmed through measurements that impulse surge current invades to the signal machine room through shield conductors of a track circuit cable connected to grounding wires. Also, it was confirmed that steel frame grounding was used as a path for another impulse surge current to enter the room. Therefore, in this paper, the ground current status of the signal room is analyzed, the improvements of grounding facilities in the signal room are listed, and the improvement effects of the ground current are presented.

Line Arrester Application on a 110 kV High Alpine Overhead Line to reduce Lightning-Caused Outages

This contribution discusses a project, which aims to increase the reliability in an existing 110 kV overhead transmission network by taking measures addressing lightning and grounding issues. Due to the fault statistic in the past, a single overhead line was identified as a main reason for the lightning-caused outages in the area. In this work a number of possibilities for the reduction of lightning-caused outages are discussed and the measures taken in the network are described. All considerations took the special geographical situation of 2300 meter above sea level, the grounding resistance of up to 1200 Ohm and the local lightning activity of more than 6 lightning strikes per km² and year into account (4 to 5 times higher than in other Austrian regions). An analytical process was carried out to evaluate relevant parameters and to develop a concept of practical measures. Within these evaluations, the footing resistance, the effectiveness of the shielding angle of the shielding wires and the line arrester locations were analyzed. A multiplicity of numerical calculations were performed to assess the application of surge arresters regarding the insulation coordination for the system. To improve the line performance and to decrease the line outage rate, a number of practical measures were applied to the 110 kV line. In the past, the double three phase systems of the 110 kV overhead line was constructional converted into one active single three phase system with two additional earth wires. According to the numerical results, 18 surge arresters have been installed in a line section of 9 towers, located in a high alpine part and in an area of high lightning activity. Three years of field experiences have shown that the theoretical investigations and the practical measures led to a significant decrease of lightning caused outages. In the year 2007 a new project was started to evaluate a reconstruction of the line into the original double three phase system. New numerical calculation routines were made to apply line arresters at this important 110 kV system in an Austrian extreme mountain region. Based on this results, a new application of line arresters and the constructional change of the system is planned.

Improving the polarisation and depolarisation current measuring method to avoid ground wire interference

The ground wire is significantly interfered by the current above 1 μA in the industrial field during the traditional polarisation and depolarisation current (PDC) measurement. This paper explains a method to test PDC from high-voltage wire using a principle of equipotential picoammeter, which is completely isolated from the ground wire and connected in series with the high voltage wire. In this method, a device is designed with a multi-range automatic switching function. The device can automatically switch the test range current from 1 pA to 10 mA with a resolution of 1 pA. To demonstrate the device and effectiveness of this new method, the traditional and the proposed new device are used to test the PDC of cable samples in the laboratory as well as in an industrial environment. It is worth noting that there is almost no interference on the Earth wire in the laboratory environment but massive interference in the industrial environment using a traditional method of PDC measurement from ground or Earth wire. The new method of high-voltage testing can efficiently eliminate the interference and accurately measure PDC in a strong industrial interference environment. Furthermore, the wiring of this new method and device is relatively simple, which is convenient for industrial applications.

Online monitoring and early warning technology for the status of earth wire for overhead line

Overhead lines for wind power transmission in the southern region have the characteristics of large tower-line elevation, across thick ice areas, harsh natural environments, and difficult maintenance. Unpredictable line breakage accidents often occur, affecting the stability of the social power supply. This paper designs and introduces a technology based on intelligent perception technique for online monitoring of the earth wire, which can realize long-term real-time online monitoring of the state of the earth wire of overhead lines and solve the problem of line monitoring from wind power transmission and fault inspection and troubleshooting. Now the test and monitoring work of an overhead transmission line has been completed during the ice period, and the test results show that the technology has good monitoring performance.

Analysis of transmission line tower subjected to wind loading

Heavy electrical transmission lines are carried by transmission line towers at a suitable and safe height above the ground. These towers must bear its own weight and distress created by transmission line wires. Despite that it should also survive against all-natural factors such as fierce winds, earthquakes, and snow loads. For a safe and cost-effective design, transmission line towers must fulfil both all structural and electrical standards. This manuscript discusses the numerous types of transmission towers and their configurations as per the Indian Standard IS 802:2015. Further this paper contains the details of the design and simulation of 500 kV double circuit conductors, which is one of the commonly adopted transmission towers. For the said purpose STAAD Pro. V8i Select Series, computation tool has been adopted which is based on the finite element computations. During computational analysis wind load, structural dead load, and seismic load according to IS:1893:2002 (part 1) has been considered. The clearance from the ground (h1), the lowermost conductor wire's maximum sag (h2), conductor wires' vertical spacing (h3), and the distance between the earth wire and the highest conductor wire in terms of vertical distance (h3), all are added up to get the final height of transmission tower which is 43.5 m. The earth wire is also known as the ground wire, is always sited at the very topmost of the steel tower. It features an 8.32 m square base with a width of 8.32 m. The three major phases of the fragility analysis procedure for transmission towers under wind loading are as follows: Nonlinear dynamic analysis, regression analysis, and creation of Wind loadings and uncertainty models. After that, the random variables and probability distributions corresponding to them are examined. Finally, based on the commonly adopted transmission towers a hypothetical case study has been conducted for a real-world functioning tower which is subjected to wind loading along with other critical loadings. The obtained result shows that if we are considering a larger number of uncertain characteristics, then it causes the fragility curve to become more disperse, and further it is observed that the angle of attack for the wind load has a substantial effect on the fragility curve.

Building Techniques of Multi-Subconductor Transmission Lines.(Dept.E)

A great number of transmission lines in which each phase consists of multi-subconductors are now present in many practical systems. This paper introduces three different bundling techniques which can be used effectively to obtain the parameters of such lines in terms of phase quantities. Examples are given to illustrate the application of these techniques. A method for eliminating the earth wire (s) while preserving its effect, based on the well known matrix reduction, is also introduced. A general comparison between the bundling methods is given and it is shown that, one of these methods require more computation time than the others though it may be easier in programming.

AT급전방식 통합접지시스템의 주파수별 접지임피던스 특성 분석

This paper, when lightning current flows into the AT electric railway power feeding system, the ground impedance characteristics according to the length of the buried earth wire and the earth resistivity are analyzed and presented. Due to the increase in accidents caused by lightning and surges in the electric railway operation section, the need to review the grounding impedance of the electric railway integrated earthing system is increasing. The grounding system currently applied to the electric railway operation section has been considered in terms of preventing electric shock to the human body and protecting facilities in the event of a ground fault or short circuit in a commercial power supply of 60[Hz] band. Recently, electronicization of signal and communication facilities installed around railway tracks, high-quality power supply is required. Therefore, the need for technical analysis on ground impedance and transients in high-frequency bands is increasing. The ground impedance is an important factor that distinguishes the characteristics of the AT electric railway integrated earthing system.

Classification of high-voltage power line structures in low density ALS data acquired over broad non-urban areas.

Airborne laser scanning (ALS) has gained importance over recent decades for multiple uses related to the cartography of landscapes. Processing ALS data over large areas for forest resource estimation and ecological assessments requires efficient algorithms to filter out some points from the raw data and remove human-made structures that would otherwise be mistaken for natural objects. In this paper, we describe an algorithm developed for the segmentation and cleaning of electrical network facilities in low density (2.5 to 13 points/m2) ALS point clouds. The algorithm was designed to identify transmission towers, conductor wires and earth wires from high-voltage power lines in natural landscapes. The method is based on two priors i.e. (1) the availability of a map of the high-voltage power lines across the area of interest and (2) knowledge of the type of transmission towers that hold the conductors along a given power line. It was tested on a network totalling 200 km of wires supported by 415 transmission towers with diverse topographies and topologies with an accuracy of 98.6%. This work will help further the automated detection capacity of power line structures, which had previously been limited to high density point clouds in small, urbanised areas. The method is open-source and available online.

177 Use of diatomaceous earth and copper oxide wire particles to control gastrointestinal nematodes in lambs

Abstract Anthelmintic resistance urges alternatives to control gastrointestinal nematodes (GIN). Copper oxide wire particles (COWP) are more efficacious when used with dewormers and little is known on efficacy of diatomaceous earth (DE) to control GIN. The objective was to examine the effects of DE and COWP on GIN control. Katahdin lambs (n = 32; ~150 d of age; 25.0 ± 1.8 kg) were randomly assigned to receive: 1) 2% dietary DE, 2) 1g COWP, 3) both 2% DE and 1g COWP, and 4) neither DE or COWP. Feces and blood were collected on d 0, 7, 14, 21 and 28 to determine fecal egg counts (FEC) and blood packed cell volume (PCV). Feces were cultured to determine GIN genera. FEC were log transformed; data were analyzed as a 2 x 2 factorial using proc mixed with day as repeated (SAS). There was a mixed GIN population including 58% Haemonchus contortus and 30% Trichostrongylus spp. FEC tended to be lower by d 28 in DE (175 eggs/g) than no DE (753 eggs/g) fed lambs (P = 0.09), but in general, were relatively low and no other differences among treatments detected. PCV tended to be higher in COWP than no COWP lambs by d 28 (P = 0.10), and no other differences detected. In conclusion, during a low GIN challenge, there may have been a small effect of DE on FEC but no advantage was observed in combination treatment.

Three Phase Transformer: Connection and Configuration

3- phase distribution transformers generally have a Delta (Triangular) connected primary winding and a Star (Wye) connected secondary winding. The secondary Star configuration allows for a 3-phase and Neutral, Dy1 supply providing line and phase voltages and currents. Commonly the Neutral and Earth connections which provide a 5-wire (3-phases + Neutral + Earth) TN-S (separate Neutral and Earth) supply to homes and buildings are connected together at the star point of the three secondary winding, thus the Neutral and Earth are effectively bonded together and remain at the same zero or Earth potential. However, with a TN-C (combined Neutral and Earth) 4- wire (3-phases + Neutral) supply the Neutral wire also acts as the Earth wire, but the neutral wire is still bonded along with a separate Earth electrode to the star point of the secondary winding to provide the required phase voltages and currents. TT and IT configurations have different Neutral and Earthing arrangements. Being a Delta connected Primary winding and therefore a balanced load for the supplying network, there is no Neutral or Earth connection to the three primary winding, (Earthing is done at the generator source) but it is possible that the physical metal casing of the transformer has been bonded to the secondaries Earthing bar for safety.

Stability analysis of glass fibre polyamide composite transmission tower

The cross-sectional degradation of steel transmission tower members due to corrosion has been one of the major issues in the transmission line system. The degradation of appearance of the material has also been seen because of corrosion. Therefore, there is a need for a less corrosive and high strength alternate material for transmission towers. It seems in recent years that alternate materials have been needed to replace steel which have low maintenance cost and good resistance to corrosion. The advantages of composite transmission towers are fire resistant, high stiffness, durability, high strength, moderate ductility, rigidity, easy to assemble and economical. The present study has made an effort to evaluate the performance of composite transmission tower. The glass fibre polyamide composite material has been used as a structural material. First, a finite element tower model of 132 KV has been set up in Structural Analysis and Design Software as glass fibre polyamide structural material as per transmission tower design guidelines (Code for Transmission tower design, IS 802.1.1.1995, Bureau of Indian Standards). Second, all the active loads like wind load on the body, wind load on conducting wires and ground wires, weight of conducting wires, weight of structure, weight of ground wires, weight of insulator and weight of line man with tools are calculated manually as per transmission tower design guidelines and applied in the finite element tower model. The stress distribution of the composite tower model has been simulated in Structural Analysis and Design Software and the results have been analysed. The broken wire condition (if one conductor is broken or earth wire is broken) has been innovatively considered in the present study. Results obtained in this article show that maximum induced stress on transmission tower member is less than the deign strength of glass fibre polyamide composite material. The glass fibre polyamide composite material has been found to be capable to withstand the maximum stresses induced due to different loading conditions considered in the study.

Modelling and experimental validation of EM wave propagation due to PDs in XLPE cables

Monitoring of electromagnetic (EM) waves due to partial discharge (PD) is a promising tool for condition monitoring of cables. This study presents the development of a modelling scheme for simulation of EM wave propagation due to PDs occurring at cavities in the cross-linked polyethylene (XLPE) insulation. Simulation models for generation and propagation of PD pulses through the cable geometry are developed. A finite element method (FEM)-based model is developed to simulate the PD current along cylindrical voids in the cable insulation. The initial fields due to the PD currents in the voids are simulated by an FEM model. The propagated EM fields inside and outside the cable surface due to PD's occurring inside the voids are analysed by a finite-difference time-domain model. The analysis of propagated EM fields due to a Gaussian-shaped PD pulse identifies the dominant components of propagated electric and magnetic fields along the cable geometry. Furthermore, the propagated EM fields at the cable sheath due to different void dimensions are simulated and experimental validation of the propagated magnetic field is conducted with measurement by an high-frequency current transformer sensor installed around an earth wire from the sheath of an 11 kV XLPE cable.

A two-wheel load balance control strategy for an HVTL inspection robot based on second-order sliding-mode

PurposeOverhead high-voltage transmission line (HVTL) inspection robots are used to inspect the transmission lines and/or maintain the infrastructures of a power transmission grid. One of the most serious problems is that the load on the front wheel is much larger than that on the back one when the robot travels along a sloping earth wire. Thus, ongoing operation of the inspection robot mainly depends on the front wheel motor’s ability. This paper aims to extend continuous operation time of the HVTL inspection robots.Design/methodology/approachBy introducing a traction force model, the authors have established a dynamic model of the robot with slip. The total load is evenly distributed to both wheels. According to the traction force model, the desired wheel slip is calculated to achieve the goal of load balance. A wheel slip controller was designed based on second-order sliding-mode control methodology.FindingsThis controller accomplishes the control objective, such that the actual wheel slip tracks the desired wheel slip. A simulation and experiment verify the feasibility of the load balance control system. These results indicate that the loads on both wheels are generally equal.Originality/valueBy balancing the loads on both wheels, the inspection robot can travel along the earth wire longer, improving its efficiency.

Effect of indirect lightning strike to 66kV transmission line in Java-Bali system

Based on Java-Bali grid disturbance data, the 66kV transmission lines that is close to or intersect with 150kV or 500kV transmission line is often experienced earth fault due to insulator flashover. The insulator flashover can be caused by indirect lightning strike since lightning strikes tend to strike higher structure. Therefore, this paper will determine the effect of indirect lightning strike on 150kV or 500kV transmission line to 66kV transmission line by modeling and simulation using application of transient analysis. Variation of lightning peak current magnitude and gap between 66kV transmission line and transmission line with higher voltage is performed during simulation. The range of peak current magnitude follows the data from lightning detection systems, while the value of gap follows the data from actual condition. It is found that higher current peak and closer gap will cause higher transient overvoltage on insulator of 66kV transmission line thus insulator flashover may occur more frequent. Addition of earth wire on 66kV transmission line and gap between each transmission by organizing the sag of conductor can be performed to minimize the insulator flashover.

Covered conductor burn-down prevention for distribution line in Indonesia

Covered conductor (CC) is used to resolve temporary line to ground fault in the distribution line. However, some cases of CC burn down were found in Indonesia. These phenomena were triggered by lightning strikes that cause transient overvoltage with a magnitude greater than basic insulation level (BIL) of insulator. Consequently, short circuit current will flow through the pinhole on CC. Burn down phenomena will create high impedance fault that is unable to be detected by protection relay, thus the conductor will remain energized and harmful to the surroundings. Therefore, this paper presents study about CC burn down prevention. The study was performed using transient simulation to find the effect of earth wire utilization against the transient overvoltage due to lightning strike. In addition, finite element simulation and laboratory testing were also performed to analyze the effect of power arc device on burn down prevention. The results show that the lightning strike with negative polarity will not cause transient overvoltage with a magnitude greater than the insulator BIL. However, if the lighting strikes have positive polarity then the insulator BIL will be potentially exceeded. Furthermore, the utilization of power arc device will prevent the CC burn down.

Earth wires currents calculation by tableau analysis

The paper presents a new method to compute a phase-to-earth fault current distribution in overhead transmission line. The method is based on the tableau analysis of an unbalanced, multi-wire model of a transmission line. It allows for the calculation of current distribution in overhead earth wires along the transmission line. Additionally, it may be used to calculate currents in a tower’s earthing system as well as voltages over every tower of the transmission line. The method can be used for analysis of any type of transmission line (single circuit, double circuit and multi-circuit lines) with any number of earth wires. The calculation results may be used for complex designs of transmission line earthing systems, earth wire thermal rating selection, and the evaluation of shock hazards.

Demonstrating Earth connections and fuses working together

Earth wires and fuses work together in UK mains circuits to keep users safe from electric shocks and are taught in many school contexts. The subject can be quite abstract and difficult for pupils to grasp, and a simple but visually clear and direct demonstration is described which would be easy for most physics departments to build and which can make the concepts much more immediately understandable.