Power Cable Lines Research Articles

Improvement of the Method of Calculation of Steady-State Modes of Urban Electric Networks Taking into Account Consumer Energy Sources

The method of calculation of the steady-state mode of the open city distribution electric network with small generation sources is offered. It is shown that the city electric network consists of passive and active physical elements. Passive elements include power transformers and linear regulators, overhead and cable power lines, current-limiting reactors, etc. Active elements of networks are power sources (transformer inputs of low voltage of feeding substations and distributed small generation sources) and loads, mathematical models of which can be various. Power sources in urban distribution networks of 10 kV and below are classified by type and power and can be of two kinds, viz. power feeding centers of the network and small generation sources. Consumer loads are modeled by current sources connected to network nodes. The parameters of the current sources are usually graphs of the change of the module of the actual current value and the power factor in time. The values of these parameters in single-line substitution schemes of 6–10 kV distribution networks with isolated neutral are assumed to be average for three phases. The power centers are transformer inputs of low voltage power substations of the main electric networks of 35 kV and above, equipped with digital devices of the account of the electric power connected to the automated system of control and accounting of power resources. The developed technique allows receiving the refined balanced calculation model of the steady mode of the open city network for the set time of the daily schedule. It includes the sequential distribution of the specified power of each network power supply between its loads, followed by clarification of flows and power losses in the sections, as well as voltages and actual loads in the nodes of the scheme by the overlay method.

Minimization of active capacity losses in cable power lines of 0.4 kV using optimally distributed compensating devices at petrochemical and oil refining enterprises

We propose a solution for optimization problem of minimizing active power losses for radial power supply scheme by optimal distribution of a given amount of reactive power between the compensating devices. We considered a single-line power supply scheme for a group of pumps of technological installation at a chemical plant. A mathematical model of the optimization problem is compiled by the criterion of active losses minimum in power lines depending on the reactive power flow. We obtained the distribution of optimal values of reactive power between the compensating devices of asynchronous motors for the specified tg φ. Quantitative and cost estimations are given for reducing the active power losses in power transmission lines when using capacitor plants, the reactive power of which is optimally distributed. We investigated the influence of starting currents on a circuit when asynchronous motor and capacitor installation are simultaneously turned on. We established the absence of an additional dynamic load on the supply lines.

The Evaluation of Impact of Cable Power Lines on the Environment

The thermal impact of cable power lines and structural materials of cables on the environment has been considered. A quantitative evaluation of the thermal impact of electrical cables with cross-linked polyethylene insulation on the environment was carried out using the Elcut program. Analysis of the temperature field near the loaded cable line of 10 kV demonstrated high values of soil temperature that negatively affects its redox potential and living organisms. To evaluate the environmental impact of electrical cable materials, an approach has been developed that takes into account not only the toxicity of the materials but also their volumetric content in the cable. Cable lines with cables with traditional paper-oil insulation cause more damage to the environment than cable lines with cables, insulated with crosslinked polyethylene. The environment, in turn, also has an impact on the electrical cables: the values of long-term permissible load currents depend on the ambient temperature (when laying cables in the open air, in an earthen trench or in cable rooms). The impact of solar radiation on the thermal conditions of the electric cable is estimated. A comparative analysis of the complex environmental impact of electric cables with traditional insulation and insulation of crosslinked polyethylene demonstrated that unarmored cable with crosslinked polyethylene insulation at a voltage of 10 kV (regardless of the type of its shell) causes less damage to the environment than the same traditional cable throughout the considered temperature range on their surfaces.

Advanced Patient Health Monitoring System using Power Line Communication Technology

Open source automation system is rapidly developing towards more reliable communication systems. In recent years for its convenient installation and low cost the power line increasingly become a popular transmission medium in creating industrial/ resident work. PLC is a technology uses power lines as physical media for data transmission. PLC offers a no new wires solution because the infrastructure has already been established. PLC modems are used for transmitting data at a rapid speed through a power line in a house, an office, a building, and a factory, etc. Due to this additional telemetry features, cost of the devices are more and all hospital or clinic cannot afford to buy them. Hence in our work, temperature, blood pressure and heart beat monitoring equipment based on power line communication is developed. This is cost effective equipment which uses existing power cables as communication medium. Power Line Modem (PLM) is used for transmitting and receiving the signals over power line cable. Signalsare modulated and demodulated using direct-sequence spread spectrum (DSSS) technology. When compared with other communication technologies like local area network (LAN), ZigBee, Bluetooth, the establishment cost for healthcare monitor using Power Line Communication (PLC) was low.

An Alternate Method for Prediction and Analysis of Notch Characteristics in Indoor Power Lines Under Varied Channel Conditions

One of the challenges faced by indoor power line communication systems is the frequency-selective channels that are time varying and dependent on a large number of variabilities. A probable solution is to extract as much determinism as possible through prediction and statistical analysis of the frequency-selective notches. However, such deterministic tools are available only for simple open- and short-circuit branches and not for complex loads and topologies. This paper proposes an alternate method to predict and analyze notches using a minimum of four parameters without evaluating the transfer function. Termed as the load frequency mapping, the method is applicable for any frequency-dependent time-invariant loads and topologies and also capable of performing statistical analysis of random channels. A high decrease in prediction error (99.46–93.63%) is found for all the channels analyzed. Statistical analysis of 26 power line cables using random loads shows that some cables and loads offer more variations in frequency selectivity than others. For capacitive loads, the variation is more for the low-frequency notches and for those modeled as parallel resonant circuits at the frequencies near the resonance. Maximum variation is found for cables with high characteristic impedance with loads having high resonant frequencies and low quality factor and least for inductive loads. The power line therefore has considerable amount of determinism, and this can be incorporated to complement for fading channels or analysis of variability optimized for dual purpose of power delivery and data transfer.

Motion posture control for power cable maintenance robot in typical operation conditions

Purpose In the extreme power environment of flexible transmission line, wind load, high voltage and strong electromagnetic interference, the motion performance of the robot manipulator is strongly affected by the extreme environment. Therefore, this study aims to improve the manipulator motion control performance of power cable maintenance robot and effectively reduce the influence of specific operation environment on the robot manipulator motion posture. Design/methodology/approach The mathematical model under three typical operation conditions, namely, flexible line, wind load and strong electromagnetic field have been established, correspondingly the mapping relationship between different environment parameters and robot operation conditions are also given. Based on the nonlinear approximation feature of neural network, a back propagation (BP) neural network is adopted to solve the posture control problems. The power cable line sag, robot tile angle caused by wind load and spatial field strength are the input signals of the BP network in the robot motion posture control method. Findings Through the training and learning of the BP network, the output control variables are used to compensate the actual robot operation posture. The simulation experiment verifies the effectiveness of the proposed algorithm, and compared with the conventional proportional integral differential (PID) control, the method has high real-time performance and sound stability. Finally, field operation experiments further validate the engineering feasibility of the control method, and at the same time, the proposed control method has the remarkable characteristics of sound universality, adaptability and easy expansion. Originality/value A multi-layer control architecture which is suitable for smart grid platform maintenance is proposed and a robot system platform for network operation and maintenance management is constructed. The human–machine–environment coordination and integration mode and intelligent power system management platform can be realized which greatly improves the intelligence of power system management. Mathematical models of the robot under three typical operation conditions of flexible wire wind load and strong electromagnetic field are established and the mapping relationship between different environmental parameters and the robot operation conditions is given. Through the non-linear approximation characteristics of BP network, the control variables of the robot joints can be obtained and the influence of extreme environment on the robot posture can be compensated. The simulation results of MATLAB show that the control algorithm can effectively restrain the influence of uncertain factors such as flexible environment, wind load and strong electromagnetic field on the robot posture. It satisfied the design requirements of fast response, high tracking accuracy and good stability of the control system. Field operation tests further verify the engineering practicability of the algorithm.

3D Modeling and Volume Estimation of Riverbed Layers Based on Sub Bottom Profiler Measurement Data

The river is one of the transportation routes for human beings, as well as the pipelines for oil and gas distribution, or as power cable lines and communications networks. In order to not disturb the pipe or cable due to the activity of the ship through the river, it is necessary to study the sediment from the river. This study aims to determine the type of sediment, the thickness of the sediment, the depth of sediment, and volume of the sediment itself. It can be done with acoustic measurements.The measurement of the acoustic survey in this activity uses a sub bottom profiler Strata Box HD type Chirp. By using this tool, it can obtain sediment layer up to a certain depth. The result of the measurement will be interpreted to obtain the travel time of the acoustic wave as it reflected on the sediment layer. The travel time than processed and corrected with the tidal measurement data which made over 14 days to obtain the actual depth value from the result with the sub bottom profiler. The depth data then were quality tested based on reference IHO SP-44 2008 at order 1a.This activity produces a 3D model of river layer, depth profile and sediment layer volume estimation. The result of the quality tested obtained corrected depth data has met the established standards of order 1a IHO SP-44 2008. Using a 95% confidence level, the test results in the first layer is 0.271 m with an error tolerance at 0.510 m. For the second layer has a data quality test results 0.491 m with a tolerance at 0.521 m. The result of depth profile is a long section and cross section. The long section indicates that in the deflection of the river area there is a steep decline compared to the area before and after the river deflection. In addition, the river deflection area has a thinner sedimentary layer. The volume estimation of sediment layers obtained in the area of the activity is 4932752.739 m3.

Mathematical model of XLPE insulated cable power line with underground installation

Mathematical model of XLPE insulated cable power line with underground installation

Deterioration of xlpe insulation in high voltage cable systems and testing of quality by applying pulses of high voltage

The wide spreading of energy distribution power cable lines made by means of applying cables with insulation made of cross-linked polyethylene usually is associated with a significant number of advantages in terms of better technical performance that such cables have in comparison with traditional cables with paper-impregnated insulation. Nevertheless, the necessity to ensure a sufficient level of production quality, as well as the requirements for increasing the operating time of power cable lines, make it urgent to develop insulation quality control methods, including control methods which imply applying of testing impulses that simulate overvoltages that occur in power systems due to lightning strikes. The other aspect of this problem is the necessity of the elaboration of physical models for the description of deterioration of XLPE insulation of power cables under the impact of various external factors. For recent years the problem of testing XLPE insulation by high voltage pulses, similarly to the problem of elaboration of physical models for the description of deterioration of XLPE insulation, have been considered by many authors. This paper gives a brief review of some main recent research that have been focused on the problem of endurance and aging of XLPE insulation due to overvoltage caused by various reasons. The main scope was focused on the problem of testing the endurance of XLPE insulation to the voltage pulses that imitate overvoltage due to lightning strikes. Some of the theories of aging of dielectric materials under the impact of impulse and alternating electrical fields and the influence of these factors on lifetime of dielectric materials have also been discussed.

Comparing frequency‐dependent and distributed parameter with lumped losses power cable line models for cable insulation coordination against overvoltages

Simulations of transients are an obliged step for the insulation coordination of cable lines. Although a frequency-dependent power cable line model better takes into account real conditions since resistive and inductive parameters vary with frequency, a distributed parameter with lumped losses power cable models can be useful to simplify and give higher flexibility to the insulation coordination study. In such a case, a dilemma rises up when a frequency shall be selected for the determination of the cable parameters. In this study, a comparative analysis between the two models has been performed considering a typical configuration layout, i.e. an overvoltage coming from an overhead line and stressing the cable line terminated on a transformer. The overvoltages stressing both cable insulation wall and cable thermoplastic jacket are evaluated using the same system configuration with both frequency-dependent and distributed parameter with lumped losses power cable line models, in the latter case sweeping different frequency values for the determination of the cable parameters. A frequency range that minimise the differences between the overvoltage estimation using the two models is suggested.

Analysis of causes of failures in 10 kV electrical power distribution networks (on the example of the Southern electrical networks of the city of Irkutsk)

Disconnection of power consumers from power grids is quite a common event, with a wide range of consequences. Power supply interruptions can be caused by both casual events, and planned shutdowns. Disruptions in systems of power supply of consumers lead to a variety of adverse events (under-delivery of products, large-scale product rejection, failure of production equipment, etc.), which inflicts a significant economic damage. The retrospective analysis of the failure rate of electrical networks of the Right Bank and Left Bank districts of Irkutsk over 2013–2017 has been carried out. The analysis was based on the data from dispatching logs of observations on events of failures caused by emergency damage to the Southern electrical networks. It is established that the greatest number of failures occurs for such reasons as damage at substations, damage to consumer electrical networks, wire breakage in air and cable power lines as well as damage of switching equipment. Failures related to wind load, damage at packaged transformer substations, insulators and surge arresters are also analysed. The percentage rate of failures of electrical power networks caused by specific reasons from the total number of failures is presented. Besides, the analysis is performed of the duration of interruptions of power supply owing to damage of individual elements of power network equipment as well as the amount of electric energy undelivered for these reasons, and financial losses caused by these failures due to under-delivery of electric energy, with the average wholesale electricity prices taken into account.

Improving the reliability of combined overhead and cable power lines by organizing smart autoreclosing

The application of combined overhead and cable power lines (OCPLs) of 110 kV voltage rate and higher call for new features for power system protection and automation devices. One of the most urgent is the problem of autoreclosing (AR) of OCPL. One or another solution to this problem significantly affects the reliability and efficiency of the OCPL operating. In many countries, both non-selective AR and selective AR are used. A method of selective AR of OCPL based on traveling waves is proposed, which increases the reliability of OCPL protection and automation. The method uses a special procedure of traveling wave pattern classification for faulted section identification.

Modelling of Deterioration of Electrical Insulation of Low Voltage Power Lines Seaports

The paper deals with the problem of analysis of time between failures (wear) of electrical insulation in conditions of lack and inaccuracy of data on the state of the object. The study of the specifics of the aging of such a system element of the sea port power supply as the isolation of power cable lines shows its importance in influencing the reliability of the port power supply. Marine intra port electrical network has its own specifics - firstly, it is a low-voltage network and high-ampere, in which the role of partial charges is minimal, secondly, in marine low-voltage power lines there are areas of increased sensitivity to the environment associated with the output of the power line (cable) from trenches to current collectors and contact columns with stripping insulation, which begins to contact with the environment, thirdly, in connection with the above, the humidity plays a destructive role, acting together with increased temperature. In the process of building a model of operating time before insulation deterioration, factors that are measurable with the help of devices are taken into account, and they also significantly characterize the long-term effect on insulation deterioration and lead to a state of failure. This article develops a mathematical model based on inaccurate data with estimated limits of inaccuracy. To solve the problem, computer simulation using the membership functions of fuzzy sets is proposed. Using the developed software in Mathcad obtained the numerical results of time to failure.

Increasing the efficiency of Non-Destructive methods of the diagnosis power cable lines UP to 35 KV

Increasing the efficiency of Non-Destructive methods of the diagnosis power cable lines UP to 35 KV

Test results of resonant single wire system transmitting power to the infrastructure objects of the JSC “RZD”

The paper provides test results of pilot sample of resonant single wire transmission system to a distance of 2000 m at a higher frequency. Cable power lines used as the power line based on coaxial cable. Operating principle of resonant single-wire transmission system is based on the use of two resonance transformers with frequency of 5–15 kHz, wire line voltage between the line is 1–10 kV when operating in a resonant mode. Resonant power transformers consist of a resonant circuit and step-up/step-down winding. Resonance system for high efficiency energy transfer system when adjusting all parameters at certain voltage, frequency and load. With the set of equipment, which operates at a frequency of 7–9 kHz and at a voltage of 980 V, power line can transmit electricity on a single transmission line up to 3000 watts. The article describes the possibility of applying a resonant sin-gle-wire power transmission system at a frequency of about 7 kHz for the transmission of electric power up to 3 kW from a stationary power supply system (three-phase voltage is 380 V AC, 50 Hz) for single-phase load, and earthed on the individual earthing inverter. Efficiency of resonant single-wire electric power transmission system increases with increasing load capacity. It can reach 88–91 % directly at the maximum load with efficient conversion equipment. Measurements of electromagnetic fields from unscreened power lines were carried out. The results of the measurements show that the maximum value of the alternating electric field in the frequency range of 2–400 kHz is 100–150 V/m, well below the maximum permissible level. The advantage of the resonance system compared to a single-phase system is in operating at the frequency of 7 kHz.

Enhanced analytical model of power transmission line icing

Accidents in power transmission lines under icing conditions, in particular, those of cables, cause a great economic damage in Russia. Because of the lack of the possibility to forecast and evaluate reliably the consequences of weather conditions contributing to icing of transmisison line cables, power grid services often have to go to the place of a potential accident relying on guesswork. This leads to considerable losses of time and material resources, while the average recovery time of a damaged high voltage power transmission line is 5–10 days.For the effective prediction and timely prevention of negative consequences of icing of on power line cables, an analytical model that describes the growth of ice on the surface of the electrical cable has been developed. The model is based on a widely applicable analytical model of [1], supplemented with dependence of the growth of ice sleeve on the angle between the wind direction and the cable, and on the electric field strength of the cable.The results obtained using the new analytical model and the [1], model have been compared and show that as the angle between the wind direction and the cable decreases, the intensity of the ice growth decreases significantly. At the same time, the strength of the electric field of the cable affects negligibly the trajectory of water droplets.A conclusion is drawn about insignificance of electrical field strength of the electric cable as a factor of growth of ice deposits. It is stated that the ice thickness value obtained using the developed model can be increased under specific weather conditions and design parameters of transmission lines. The obtained model can be improved by using other physical effects that affect icing of electric cables. Further, the model can be introduced in operation of energy companies to monitor the condition of power transmission lines and to carry out anti-icing activities.

Long Range Guided Wave Propagation Experimental Analysis in Overhead Power Line Cables under Different Axial Load Levels.

Over the past hundred years, overhead power line cables have been widely installed around the world. These cables are commonly exposed to adverse environmental conditions that can affect their structural integrity and over time, could lead to the complete failure of the structure. This research presents the use of guided waves for the inspection of the structural integrity of the overhead power line cables. The proposed system relies on permanently installing on power line cables a multiple transducers collar as well as a pulse receiver. The system is installed on the cable and performs automated regular inspections. One of the key features of this technique is its ability to inspect a long section of the cable from a single inspection point. To achieve this objective, the wave propagation features have been studied in a wide range of frequencies in 50m long cables, where different collar configurations were used. In addition, power line cables, when installed, are subjected to different axial loads depending on the type of cable and the distance between pylons. The effects of the axial load on the wave propagation have been studied. To assess the defect detection capabilities of the system over a wide range of distances without damaging the cable samples, a metallic clamp is used to introduce a cross-section change on the cables, simulating the effect of a fault on the cables (i.e. corrosion). The experimental results show the highly attenuative effect of the axial load on the wave propagation for most of the frequency spectrum. However, it was found that at low frequencies the system performance allowed the inspection of long distances. This was further proven with the experimental results for the clamp detection study.

Optimal power flow control in the system with offshore wind power plants connected to the MTDC network

The construction of offshore wind power plants usually requires transmission of the large amount of energy over the large distances with cable power lines. The most effective solution for the connection of large number of remote offshore wind power plants to the rest of the system is with MTDC transmission network. In this paper, the methodology for optimal control of power converters for minimizing power losses in the system is presented. The main task of the proposed methodology is to determine, based on the forecasted production of wind power plants, the performance characteristics of the power converters that would enable their optimal decentralized work in the presence of intermittent production from wind power plants. The determination of the power converter characteristics is conducted during day-ahead power system operation planning, based on which the power converters, during a real time control, maintains optimal operation of the system locally, without communication with each another. The proposed methodology is tested on the example of MTDC network with 5 buses connected to the IEEE 14-bus test system.

Influence of Oil-Filled Transformers Overload Capacity on the Throughput Capacity of the Electrical Network

During the operation of the electric power system, there is often a need to overload its individual elements (generators, power transformers, overhead and cable power lines, switching electric devices) for a period lasting from several dozens of minutes to a day. The overloads can be caused by intentional disconnection of parallel elements of the system because of scheduled preventive repairs, post-accident disconnections, as well as an unexpected increase in electricity consumption due to the impact of various factors. The overload capacity of the system elements makes it possible to increase operational reliability of power supply to consumers without additional expenditures while maintaining, in most cases, the almost normal service life of electrical equipment. Oil-filled transformers have the greatest potential overload capacity power, which makes it possible to consider them as a significant source of increasing the capacity of the transmission and distribution networks of the electric power system. Excessive over-current of power oil-filled transformers significantly reduces reliability and reduces their normal service life. This is due to the accelerated process of wear of the insulation material of the transfer windings as a result of overheating of the transformer oil, that causes structural changes and, as a consequence, to mechanical damage to the insulation of the windings; the latter can cause an electrical puncture. On the other hand, underestimation of the permissible overload of transformers might result in economic losses due to under-produced products when the functioning of the part of the transformers connected in parallel are ceased for scheduled preventive maintenance or as a result of forced emergency shutdowns. Therefore, there is a need to assess the potential of reasonable increase in the throughput capacity of the electrical network and, accordingly, the reliability of the power supply system, taking into account the requirements for the permissible loads of transformers when the electrical network and various operating modes are being designed.

Electromagnetic Situation Near Gas-Insulated and Cable Power Lines

Gas-insulated and XLPE cable power lines can be used as high-power outputs from power plants and deep inputs of power to big cities. When laying power cables in a populated area, it is important to ensure a low level of electromagnetic field. The magnetic-flux density for specific designs of gas-insulated and XLPE cable lines is calculated for different shield-grounding methods and arrangements of cables. The calculated results are analyzed.