kV Overhead Research Articles

ВИЗНАЧЕННЯ СКЛАДОВИХ ВТРАТ АКТИВНОЇ ПОТУЖНОСТІ В ДАЛЬНІЙ ЕЛЕКТРОПЕРЕДАЧІ ЗМІННОГО СТРУМУ

The components of active power losses in long-distance AC power transmission are investigated. It is shown that in the modes of low and medium loads the main share of losses are corona losses. The imperfection of the current method of determining the corona power losses, which are climatic in nature, determines the method of separating these losses from the total after calculating the load power losses. A four-component formula for determining the load losses of active power is obtained. It is shown that to clarify the calculation model it is necessary to take into account the actual temperature of the wire, taking into account changes in weather conditions along the route of the line. The results of calculation of components of active power losses in the 750 kV overhead transmission line "Zakhidnoukrainska-Vinnytska" during the day of September 13, 2021 are given. References 9, figures 4, tables 3.

Experience of Designing 110 kV Overhead Lines in the Arctic Zone of the Russian Federation (Pevek – Bilibino, Chukotka Autonomous Okrug)

Experience of Designing 110 kV Overhead Lines in the Arctic Zone of the Russian Federation (Pevek – Bilibino, Chukotka Autonomous Okrug)

STUDY OF THE ELECTROMAGNETIC IMPACT OF THE OVERHEAD TRANSMISSION LINES OF 330 KV ON ECOLOGICAL SYSTEMS

The analysis of factors and approaches to the conditioning of the electromagnetic impact of 330 kV overhead transmission lines on ecological systems has been carried out. The analysis performed enabled to reveal that the world experience, recording the introduction of the transmission lines of the carrying capacity and reduced environmental impact, including the compact and controlled self-compensating lines, is expedient to take into consideration in the process of the object design, as compared with the transmission line of the conventional construction, operated in Ukraine. The technique of electromagnetic field of the 330 kV overhead transmission lines calculation is improved for the ecological systems and to clarify the width of the sanitary protection zone. Unlike other technique, the given one takes into account the line clearance and the sag of, also this technique is universal as it enables to calculate and analyze the variation of the electromagnetic field of the overhead transmission lines of different construction not only on the line route, but also at a distance from it.

Accounting for wire saggingоn span of 220 kV OHL whendetermining current, induced in ground wire by phase current magnetic fields

Overhead ground-wire cable (GW) is more prone to ice formation compared to 220 kV overhead lines. Ice-melting methods for GW using special power source have certain engineering constraints and required is connection of overhead line. Preventive heating of GW to above-zero temperature is an equivalent method to ice-melting. Preventive heating shall be provided by induction from electromagnetic field (EMF) of 220 kV overhead lines while in service. Induction methods of 220 kV OHL GW heating have been summarized and briefly described. Mathematical models of GW inductive heating do not consider the influence of wire and GW saggingon EMF parameters and equivalent circuit ground wire-earth. Therefore, sufficient mathematical model is required to use induction method of GW heating at 220 kV OHL segment. We propose induction heating for GW of double-circuit 220 kV OHL inclosed circuit ground wire-additional conductor top reventice formation. Mathematical model have been developed to calculate current, induced in circuit ground wire-additional conductor by magnetic fields of 220 kV OHL current while in service. Influence of wire and GW saggingon EMF parameters and equivalent circuit ground wire-additional conductor has been estimated. Due to mathematical model we could estimate induced current to prevent ice formation on GW of double-circuit 220 kV OHL while in service. Closed circuit ground wire-additional conductor is recommended for practical use, with capacitor loop included into circuit, its capacitance to be determined based on voltage resonance conditions.

Compilation of a Local Electrical Insulation Pollution Map in the Sheikh-Najar Industrial Region of Syria

A method for improving the performance reliability of electrical installations under the conditions of polluting the insulation of the 66 and 230 kV overhead lines (OHL) and outdoor switchgears (OSG) in the Sheikh-Najar industrial region near Aleppo, the economic capital of Syria, is considered. According to the relevant regulatory documents, the most efficient approach to selecting the insulation levels is the one based on compiling regional and local insulation pollution maps (IPMs) in the territory where the grid facilities are located. An electronic local IPM in the Sheikh-Najar industrial region was compiled using the characteristics of industrial pollution sources. The article presents the climatic characteristics of the Aleppo city area, the electrical circuit diagram and insulation characteristics of the existing 66 and 230 kV OHLs and OSGs, the characteristics of industrial pollution sources (in terms of produced goods types and amounts), estimated pollution degrees (PD) at various distances from the enterprise boundaries with a circular wind rose, and those adjusted for the real wind rose in the city of Aleppo, and the local IPM of the Sheikh-Najar region drawn using the AutoCAD software. It has been established that there are zones with insulation pollution degrees 2, 3 and 4 in the Sheikh-Najar industrial region territory. Based on the study results, recommendations have been elaborated for increasing the specific effective creepage distance of the OHL and OSG insulation by adding linear insulators to the strings, for choosing the optimal types of substation electrical equipment, and for taking preventive measures. To refine the boundaries of local IPM zones, it is recommended to study the features characterizing the pollution of electrical installations insulation caused by both industrial and natural factors, as well as to generalize the experience gained from the operation of electrical installations in the Sheikh-Najar industrial region.

Quantitative analysis of the operational reliability of overhead power lines

The relevance of ensuring the efficiency of equipment, devices and installations (facilities) of electric power systems increases every year, becoming the most important problem of maintaining energy security. The decrease in work efficiency is due to a number of factors, but, above of all, due to an increase in the relative number of objects whose service life exceeds the standard value. An illustration of the methodology for quantifying, comparing and ranking the monthly average values of the operational reliability indicators of 110 kV and higher overhead power lines is given in order to identify and restore the wear of the least reliable lines.

An Easy-to-Implement Macro-Model for Evaluation of Lightning Induced Voltages on Overhead Lines and Its Interface With PSCAD

Accurate evaluating the lightning induced voltages of distributed networks has been the subject for several decades. The technique on the interface between the field-to-line coupling model and power system simulators are of particular interest. In this article, a solution of the Agrawal's field-to-line coupling model is derived and an easy-to-implement macro-model is developed. Combining with the “Frequency Dependent (Phase) Model” component included in PSCAD, the proposed macro-model can be directly integrated into PSCAD to evaluate the lightning induced voltages on the overhead lines. The validity and efficiency of the proposed method is demonstrated by several examples. Finally, a 1-km 35 kV overhead line above an imperfectly conducting ground is studied, and the influences of the metal-oxide arrester to the lightning induced voltages are discussed.

APPROACHES OF PROBING SIGNAL TYPE DETERMINATION OF MEANS LOCAL PROBING FOR DISTRIBUTED POWER GRIDS TECHNICAL CONDITION DIAGNOSTIC

The paper presents the modes of ice detection on a 110 kV overhead line. Methods of detecting damage during ice of power transmission wires are analyzed. Proposals for improving the approaches to determining the damage caused by ice on the wires of overhead power lines have been developed. The article focuses on the method of location probing, which consists in applying a pulse signal to the line and determining the total time spent on its propagation along the wire in the forward and reverse directions after reflection from the end of the line or from high-frequency barrier. In the locational method of detecting ice, information about the appearance of ice is carried by pulses reflected from any inhomogeneity of the wave resistance of the line on it. All negative factors, including ice, change the wave resistance of a long line, creating inhomogeneities in overhead power lines and increases the travel time of the reflected pulse of a given section of the line in the presence of ice. They can be determined by active probing. The problem is that these inhomogeneities can be small in amplitude and active sounding is unable to detect the reflected signal from the homogeneity as the power of noise and interference can be greater, and most importantly they can be on branched power lines. The paper shows that increasing the duration of the probing pulse with the use of different types of modulation allows to increase the energy of the probing signal, to provide the required spectrum width and, accordingly, the resolution of the device at a distance. The article proposes a method of taking into account the “blind zone”, in which it is not possible to determine the reflected signals from the place of heterogeneity of overhead power lines. At the time of emission of the probing signal, the input of the receiver is closed and therefore reflected from the homogeneity of the signals do not arrive at the receiver. In FMICW radar, the measurement process to determine the range is to measure the difference between the current frequency of the emitted signal and the frequency of the reflected signal in the ion probe. It is proposed to introduce an algorithm and a method of ionosonde operation for the development of a device for diagnosing the technical condition of electrical distribution networks.

Cause Analysis and Preventive Measures of Common Faults on 10kV Overhead Line

Cause Analysis and Preventive Measures of Common Faults on 10kV Overhead Line

Study about numerical relay 7SA612, the basic protection of 220 kV overhead transmission line

In this work we analyzed the numerical relay 7SA612, which represents the basic protection of 220 kV overhead transmission lines starting from the Mintia electric station. The main function of 7SA612 relay is the distance protection; in addition, this relay offers a multitude of protection functions. We used the computer-controlled Omicron CMC 356 set for testing the 7SA612 relay at its mounting location. Test Universe, the software of CMC 356, allowed the simulation of all possible overhead transmission lines faults, in order to test the protection functions of 7SA612 relay. 7SA612 relay clears fast and selectively the faults on the analyzed 220 kV overhead transmission line. The tests showed that 7SA612 relay incorporates all the necessary functions for the protection of 220 kV overhead transmission lines, both in the case of single-phase and poly-phase faults.

Climate Impacts on Quality of 6 kV Overhead Lines Operating at Mining Companies

Technological innovation in the mining industry involves the extensive use of new high-power, energy-intensive, and high-performance mining machinery that should be reliable in its operation. The key mining company equipment includes mining excavators, drilling rigs, crushing and screening units, and mine drainage facilities. Providing the fault-free power supply and the efficient operation of the electrical infrastructure of a mining company is a priority, and it depends on the quality of the power supply system and its elements.Power supply system failures reduce the operational efficiency of mining machinery, processing sections, and the mining company as a whole, which results in reduced power consumption, uneven loading schedule, failures to meet the output plans, and increased prime costs for the products.The analysis of the electrical infrastructure power supply system at a mining company shall help us assess the quality of operations and their efficiency and develop actions to reduce the idle times of electrical equipment, provide uninterrupted power supply and plan the activities of the mining company in the wholesale electrical power market more accurately.

Учет прогрессирующего обрушения при проектировании опор воздушных линий электропередачи

There has been carried out an analysis of regulations on the account of progressive collapse in the design of linear structures in relation to steel structures of supports of overhead power lines with a voltage of 330-750 kV. Methods are considered and examples are given for calculating a two-chain anchor-angular free-standing support for 330 kV overhead lines and an intermediate steel portal support on guy ropes for 750 kV overhead power transmission lines for emergency loads and impacts. The calculations for the conditions of the average operating mode are substantiated. Proposals have been developed to protect power transmission line supports from progressive collapse.

Analysis of lightning transient performance of 132 kV transmission line connected to Miramar wind farm: A case study

Lightning strikes are one of the main causes of power system trip-outs. When the overhead transmission line (TL) connected to a wind farm is struck by lightning, large currents propagate to the substation, resulting in severe problems. To enhance the performance of wind farm substations, the transient behavior during lightning must be analyzed. The main contribution of this paper is to study the lightning behavior of wind farm substations whose design is different from other conventional substations. The lightning surge overvoltages caused by back flashover and shielding-failure of the 132 kV overhead TL connected to the 33/132 kV air-insulated substation (AIS) of Miramar wind farm are calculated. This wind farm has been built in Argentina to achieve grid connection and power transmission with a total capacity of 98.7 MW. The work investigates the fast-front lightning transient overvoltages in the AIS caused by lightning flashes striking the 132 kV overhead TL. The distributed parameter model of the TL, including towers, phase-conductors, the shielding-wire, insulators, and the span, is investigated using Digsilent Power Factory software. In addition, the AIS apparatus, including surge arresters (SAs), two 60 MVA transformers, and circuit breakers, are also considered in the model. The strike is applied first at the shielding-wire, and the impact on the transient overvoltages at the TL and the substation during the back flashover phenomenon are analyzed. On the other hand, the shielding-failure is studied and the transient overvoltages at the TL and the substation are analyzed. The impact on the transient overvoltages at the TL and the substation is investigated, taking into account the SA protection operation, and its dissipated energy during lightning flashes is calculated. The study results are important for the lightning protection systems design of wind farm substations connected to overhead TLs.

High impedance fault detection in 11 kV overhead line with discrete wavelet transform and independent component analysis

This paper proposes an analysis of high-impedance fault detection algorithms for medium voltage distribution lines based on the discrete wavelet transform (DWT) technique and a more advanced technique named independent component analysis (ICA) independently. Three-phase distribution line model and two diodes high impedance fault model, which represents the unsymmetrical fault current of electric arc, simulated using MATLAB/Simulink. High impedance fault (HIF) detection algorithm initially analyzes the sampled current waveforms through DWT and the resultant third level high-frequency components “d3” coefficients are analyzed through one cycle moving window approach. The proposed algorithm successfully detects any HIF in the distribution current even if there is a slight or no difference in the amplitude of the HIF and the waveform of the phase current. On the other hand, the ICA more developed algorithm than DWT successfully separated the noise signals from the obtained current waveforms and HIF noise signals can be differentiated with non-HIF noise signals. Because of this reason ICA is chosen in this research. The detected HIF current can be from 50 ma and up.

Features of Forecasting Reliability of 6—10 kV Overhead Electric Lines According to Statistics of Their Failures and Reconditionings

This work is aimed at forecasting justification of the failure time of the 6—10 kV overhead electric lines (OEL) during the normalized period in its operation based on comparison with the statistics of failures and reconditionings on the previous intervals with the use of the OEL availability function, statistical availability coefficient, normalized forecasting interval and the accepted values of the availability coefficient on the forecasting interval. To achieve the goal set the OEL is described as an object of a multiple action, its failure and reconditioning flows are accepted as the simplest Poisson, and for the theoretical analysis of the variation character in the availability coefficient, the probability theory methods along with a mass service were used. The most significant result is justification of the use for the forecasting of the OEL failure time of a new convenient exponential expression of its availability function on the normalized period of time being forecasted. Unlike the accepted in the theory of reliability the availability function with two parameters T and Tr.av (average times of work and reconditionings), the proposed expression uses one parameter of distribution (virtual non-failure operating time). The significance of the results obtained consists in that controlling the dynamics of the variation in the statistical coefficient of availability of the OEL on the previous time intervals makes it possible to forecast its failure time during the forthcoming normalized periods of operation.

Selection of parameters of overhead lines models when calculating transient processes during earth faults in 6–10 kV networks

Single phase-to-ground faults are the most common type of faults in 6–10 kV overhead distribution networks. Arc intermittent single phase-to-ground fault (PSP) are the most dangerous for the network and the damaged element. They are followed by intense transient processes and, as a result, dangerous overvoltage rate and significant transient current surges at the point of insulation damage. PSP transients also have a significant effect on the selectivity and operation stability of protection devices against this type of damage. Therefore, the development of the methods and means to improve the operation efficiency of 6–10 kV overhead networks in case of PSP and technical improvement of protection devices in many cases is due to the need to calculate the transient processes that occur during insulation breakdowns of the network phase to earth. For the systems under consideration, the reliability of transient processes calculations in case of PSP is determined mainly by the accuracy of estimation of the parameters of 6–10 kV overhead lines, first of all, of inductance, which generally depends on the frequency of the transient current components. In the scientific papers devoted to the study of transient processes in case of PSP in medium voltage electrical networks, including 6–10 kV overhead networks, constant (frequency independent) values of inductance are used as a rule in the equivalent circuits and in the models of transmission lines. An urgent task is to estimate errors caused by the application of this approach to determine the parameters of 6–10 kV overhead lines during the calculations and modeling of transient processes during PSP, and cases of its application. Advanced methods of modeling of electric power systems and their elements have been applied with the use of COMSOL Multiphysics and PSCAD software to obtain the frequency dependences of the inductances of a 6–10 kV three-phase overhead line and study of their influence on the calculation accuracy of transient currents and voltages in case of PSP. The parameters of 6–10 kV overhead line models developed in the indicated software packages at a frequency of 50 Hz are set in accordance with the reference data. The authors obtain the errors estimation to determine the parameters of transient currents and voltages during PSP in 6–10 kV overhead networks when using transmission line models. The frequency dependences of inductance, which are up to 40–50 % in amplitude are not considered. The results show that application of frequency-independent models is permissible only in the cases when parameters of the calculated equivalent circuit of the network and position of PSP point remain practically constant, when solving problems that require high accuracy to determine the parameters of transient currents and voltages, for example, to determine remotely the location of a ground fault, it is necessary to use frequency-dependent models of 6–10 kV overhead lines. Introduction of the developed recommendations to determine 6–10 kV three-phase overhead lines parameters allow us to increase the reliability of calculations and to avoid raw errors when solving the problems which are related to the study of transient processes in case of earth faults in the networks of the given voltage class.

БЕЗПЕЧНЕ ВИМКНЕННЯ ЕЛЕГАЗОВИХ ВИМИКАЧІВ У ПОВІТРЯНИХ ЛІНІЯХ ЕЛЕКТРОПЕРЕСИЛАННЯ

The paper analyses the transient currents during the energisation of a 750 kV overhead transmission line (OTL). The safety of OTL state after symmetrical and asymmetrical closing of the circuit breakers and technical feasibility of SF6 circuit breakers opening with time delay after their closing is substantiated. The necessity of transient processes simulation for analysing the characteristics of periodic and direct components of currents is shown. A method for determining of SF6 circuit breaker opening time delay for a set of the states that may arise after the energisation of OTL is developed. References 13, tables 2, figures 5.

Melting and breaking characteristics of strands of high‐strength and high‐corrosion‐resistant OPGW due to DC arc discharge simulating high‐energy lightning strike

AbstractMetal strands of composite fiber‐optic ground wire (OPGW) are sometimes melted and broken by high‐energy lightning strikes. Direct current (DC) arc tests simulating the lightning strikes have thus been performed to obtain the melting and breaking characteristics of OPGW strands. J‐Power Transmission Network Co., Ltd. has developed high strength and high‐corrosion‐resistant OPGW for long‐span 500 kV overhead transmission lines crossing straits. This paper describes the melting and breaking characteristics of the OPGW strands due to DC arc discharge simulating high‐energy lightning strike. In this research, the tests were performed using two kinds of arc, one was the arc supposing summer lightning whose polarity was negative with a relatively short duration, and the other was the arc supposing winter lightning whose polarity was positive with a relatively long duration. Furthermore, the calculations regarding the melting and breaking of OPGW strands were carried out, and the calculation results showed a tendency similar to the test results.

Design Consideration of the Shielding Wire in 10 kV Overhead Distribution Lines Against Lightning-Induced Overvoltage

This paper presents a systematic investigation into the performance of a shielding wire on 10 kV overhead lines (OHLs) against indirect lightning, from the design point of view. The design parameters addressed include the grounding interval, grounding resistance, and position of the shielding wire. As a system outage is usually caused by insulator flashover at OHL poles under indirect lightning, the induced voltages there are investigated with the code developed from the Agrawal model. In the evaluation, the location of a lightning return stroke relative to a grounded or ungrounded pole is considered. It is found that the lightning channel positioned in the front of an ungrounded pole could completely wipe out the effect of the shielding wire. This occurs if the wave from the grounding point arrives later than the time to the peak of the voltage directly arising from the lightning return stroke. It is suggested providing the wire grounding at every pole even if the grounding resistance at some poles is much higher than the design value. Grounding spacing does not affect the induced voltages at the pole generally if the pole has been grounded. One critical parameter is identified, i.e., the distance between the shielding and outer phase wires. Minimizing the distance can effectively reduce the lightning-induced voltages.

Model for 400 kV Transmission Line Power Loss Assessment Using the PMU Measurements

This paper presents an advanced model for monitoring losses on a 400 kV over-head transmission line (OHL) that can be used for measured data verification and loss assessment. Technical losses are unavoidable physical effects of energy transmission and can be reduced to acceptable levels, with a major share of technical losses on transmission lines being Joule losses. However, at 400 kV voltage levels, the influence of the electrical corona discharge effect and current leakage can have significant impact on power loss. This is especially visible in poor weather conditions, such as the appearance of fog, rain and snow. Therefore, loss monitoring is incorporated into exiting business process to provide transmission system operators (TSO) with the measure of losses and the accurate characterization of measured data. This paper presents an advanced model for loss characterization and assessment that uses phasor measurement unit (PMU) measurements and combines them with end-customer measurements. PMU measurements from the algorithm of differential protection are used to detect differential currents and angles, and this paper proposes further usage of these data for determining the corona losses. The collected data are further processed and used to calculate the amount of corona losses and provide accurate loss assessment and estimation. In each step of the model, cross verification of the measured and calculated data is performed in order to finally provide more accurate loss assessment which is incorporated into the current data acquisition and monitoring systems.