Double-circuit Line Research Articles

Secondary Arc and Critical Time of Fault Clearance in Overhead Lines

This research presents a methodology for the creation of a novel computational algorithm, which allowed the automation of the simulation activities associated to the determination of critical times of fault clearance in the Peruvian National Interconnected System. For its development, interesting iterative stability analyzes were carried out and Ward reductions were introduced to the network model of the Peruvian electrical system. The above, in order to obtain adequate processing times, in such a way that this algorithm was applicable to the analysis of planning and operation of the power system. The secondary arc model has been developed using MODELS in ATP, which brings together the strengths of the main existing models and implements a pseudorandom variation of the secondary arc length, in order to provide accurate results for the determination of extinction times of Secondary arch in studies of monopolar reclosures. The approach of the developed model also proposes a methodology in which the extinction times are obtained as the result of a statistical simulation. The comparison of the proposed model with cases of studies of the double circuit line 500 kV with satisfactory results was carried out.

Accurate Location of Evolving Faults on Transmission Lines Using Sparse Wide Area Measurements

Abstract In electric power systems, not all fault conditions remain unchanged during faults. An evolving fault has one characteristic initially and changes to a different condition subsequently. Locating evolving faults is challenging due to the change in fault type shortly after the fault initiation. This paper presents a new approach for estimating the locations of evolving faults on transmission lines. By using sparse wide area voltage measurements, this method is able to accurately locate evolving faults without requiring measurements from either end of the faulted line. There is no need to detect whether a fault is an evolving fault or not. Fault type information is not a necessity either, and the change of fault phases does not affect the estimation accuracy. In addition, the algorithm is applicable to both single-circuit and double-circuit lines, and the transmission lines can be either transposed or untransposed. Distributed parameter line model is adopted to fully consider the shunt capacitances of the transmission lines. Electromagnetic Transient Program (EMTP) is employed to simulate transmission system, and quite accurate results have been achieved.

New fault detection and localisation technique for double‐circuit three‐terminal transmission line

This study proposes a new technique which detects fault on the line, identifies faulty circuit/line-section and estimates location of fault (fault localisation) on the double-circuit three-terminal transmission line. The fault detection and faulty circuit/line-section identification has been carried out by estimating the superimposed components of current at remote end with reference to all the three terminals. Subsequently, the estimation of fault distance is performed by utilising phase angle of voltage and current at the fault point. The performance of the proposed technique has been evaluated by simulating 400 kV double-circuit three-terminal transmission line network using PSCAD/EMTDC software package. The results indicate that the presented technique is able to detect as well as recognise the faulty circuit/line-section correctly even in case of occurrence of a high resistance ground fault near the tap point. At the same time, it is also capable of estimating the precise value of fault location as the percentage error remains within ±1.3%, even under wide variation in system and fault parameters. The proposed technique is also valid for cross-country faults and its accuracy remains consistent even with considerable errors in the measurement of current transformers and capacitive voltage transformers.

Frequency-Dependent Multiconductor Transmission Line Model With Collocated Voltage and Current Propagation

This paper reviews the classical multiconductor transmission line (MTL) equations and proposes additional constraints on these equations. A fundamental physical constraint is that the voltage and current waves must be collocated and travel together with the same propagation function. Based on this condition, the Revised Multiconductor Transmission Line (RMTL) equations are proposed. As opposed to the classical MTL equations that require complex frequency-dependent transformation matrices for their diagonalization, the RMTL equations can be diagonalized very accurately using a single real constant transformation matrix. A new Frequency-Dependent Line Model (FDLM) is proposed based on the RMTL equations. FDLM is compared with the two most accepted frequency-dependent line models in the Electromagnetic Transients Program (EMTP): The JMARTI model (fdLine) that uses a constant transformation matrix as an approximation, and the phase-coordinates Universal Line Model (ULM) that fits the frequency dependence of the transformation matrices. These time-domain models are compared with a reference frequency-domain solution for a double-circuit vertical line.

Single-ended travelling wave-based protection scheme for double-circuit transmission lines

In this paper, a new single-ended travelling wave-based protection scheme for double-circuit lines is proposed. It is developed to operate in parallel with traditional phasor-based protective relays and is able to accelerate the tripping time in most fault scenarios. The proposed method considers the propagation of travelling waves in a loop formed by the faulted and healthy line circuits. Disturbances within a given protected zone can be reliably detected according to the amplitude, polarity and time difference between the arrival instants of travelling waves that reach the monitored terminal. Also, the accumulative cross-differential current deviation is used to confirm internal faults, distinguishing them from other non-fault events. From the analysis of massive digital fault simulations and actual field records, it is attested that the proposed protection is feasible and effective.

A case study of mutual current effect on circulating current protection system

Mutual impedance generated by the double circuit lines become such a challenge to be solved. Mutual induction arises when transmission line is a parallel line on a common right of way. In this study, a system model to observed mutual current effect on circulating current protection (CCP) system are explained. The system model is validated using actual recorded fault current waveform. In one and half breaker substation, the mutual current in maintenance line may cause CCP to pick up.

Расчет емкостного тока, стекающего с воздушной линии электропередач, находящейся под наведенным напряжением при удалении на различные расстояния влияющей воздушной линии

Accidents that happen in carrying out maintenance and repair of overhead power lines account for the largest share in the statistics of injuries occurring in the electric power industry. Electric shock received by a person as he or she touches a conductor energized with induced voltage is one of injury causing factors. To assess the danger of being injured by induced voltage when the power line taken out for repair is grounded at one place, a numerical analysis was carried out for the influencing line and the line energized by the induced voltage belonging to different voltage classes with the disconnected line situated at different distances from the influencing one, and for the minimal distance between the lines when the influencing and disconnected lines are suspended to a common two-circuit support. It has been found from an analysis of the obtained values that the capacitive currents in the grounded wires decrease with increasing the distance between the influencing overhead power line and the line energized with induced voltage. The total current through the support used as the grounding conductor is higher than the current in any phase and is close to the algebraic sum of phase currents. Therefore, with the supports spaced to a significant distance from each other, it is inefficient to make grounding at the repair team working place. In this case, a more reliable result in terms of ensuring safe working conditions is obtained by individually grounding each phase.An analysis of the calculation results obtained for double-circuit overhead power lines has shown that, in order to ensure safe working conditions on the line energized with induced voltage, for double-circuit supports it is more efficient to ground all phases to the support, because the total current through the grounding conductor in the case of grounding at the work execution place is smaller than the largest current flowing from one phase. In view of the fact that the labor safety rules in operating electrical installations allow the grounding to be imposed at one place in carrying out work on overhead power lines energized with induced voltage, it is worthwhile to include calculations of capacitive current for such case in the Methodical Guidelines for assessing the safety of work carried out under induced voltage to reduce injuries to the personnel servicing overhead power lines.

Single-ended method to accurately calculate UHV AC transmission line frequency parameters

The power frequency parameter of transmission line is the basic parameter of line over-voltage calculation. It is necessary to get the parameters of 1000kV AC double-circuit line on the same tower in order to guide the operation of the project. In this paper, a method of accurately calculating UHV transmission line parameters is proposed. The length of the line is known, the voltage and current at the head of the line are measured, and the zero sequence, positive sequence total impedance and total capacitive reactance are obtained. Based on the distribution parameters Calculation formula, the line unit capacitance, resistance and inductance parameters can be obtained. The method of this paper is compared with the simulation of transmission line parameters in ATP simulation. And Through the actual measurement of the frequency parameters of Yu-heng 1000kV transmission line, it is verified that this method is suitable for the calculation of distribution parameters of UHV transmission lines.

Improvement of electric field distribution by integrating composite insulators in a 400 kV AC double circuit line in Algeria

Because of their advantages over glass and porcelain insulators, composite insulators are being used now in power transmission lines for different voltage rating levels. Recently, the 400 kV level is introduced by Societe Nationale de l'Electricite et du Gaz, SONELGAZ (Algerian Company of Electric Power and Gas) where glass insulators are installed. For better electrical performances, we propose in this paper to integrate composite insulators in a three phase 400 kV AC double circuit line situated in the northwest of Algeria. A comparison is done between the already existing glass insulators and the proposed composite insulator in terms of electric field distribution. The electric field is studied along the leakage paths of the insulators under different surface conditions (dry and clean, uniformly and non uniformly polluted, and in presence of water droplets). Three composite insulators with different shed configurations are proposed. From these three configurations, we selected the insulator presenting lower electric field magnitude in critical areas mainly on the triple point junction (air — HV end — housing material interface). On the double circuit line, we focused our study on the phase insulator that presents the highest electrical stress. Impact of hardware fittings, tower, phases and conductors on the electric field distribution has been analyzed. Effects of bundled conductors have been also studied. Simulations were carried out by employing 2D Finite Element Method (FEM) using COMSOL Multiphysics® 4.3 software. Results show that electric field is lower in the case of composite insulators. Furthermore, we found that the calculation model can be simplified by not considering all circuit phases. Note that appropriate corona rings are considered on both HV and ground ends for glass and composite insulators and their geometrical parameters (corona ring diameter, corona ring tube diameter and corona ring height) are kept constant throughout the whole study.

Electric and magnetic field of different transpositions of overhead power line

AbstractIn Lithuanian and Polish electric power supply systems, the power transmission lines of 400 kV voltage represent one of the most potential sources of electric and magnetic fields generation. The 400 kV double-circuit overhead power transmission line and its surrounding environment were herby described and simulated through Finite Element Method usingCOMSOL Multiphysicsoftware package. This study includes magnetic and electric field calculations. The study shows that the values of magnetic field strength and electric field strength present in the vicinity of a 400 kV overhead power transmission line tend to exceed limit values established in the Normative. Measurements are suggested to be taken for the purpose of finding maximum values of magnetic and electric field strength. To reduce these values, it is recommended to increase the height of supports, and restrict human personal and economic activities.

Directional relaying in presence of STATCOM during single pole tripping

Static synchronous compensator (STATCOM), a shunt type flexible AC transmission system device, is used to control the voltage at different locations within a power system by absorbing/injecting reactive power. The dynamic control action associated with the operation of STATCOM in both capacitive and inductive modes is the reason for varying system condition and failure of different relaying schemes. Directional relaying is affected by the reactive current contributed by STATCOM in wide range of inductive to capacitive mode of operation. Further, single pole tripping (SPT) condition during STATCOM operation leads to mal-function of the directional element due to phase change in sequence components of voltage and current. In this study, directional relaying is addressed for different types of faults in the presence of STATCOM connected at different locations during single phase auto reclosing period. Proposed directional relaying technique is based on the phase angle between positive sequence fault and pre-fault apparent powers. Performance of the proposed scheme has been investigated for different types of faults for single and double circuit lines during SPT using simulated data of different power networks using PSCAD/EMTDC software. A comparative study is also carried out to verify the performance of the proposed scheme for different STATCOM operating conditions.

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.

Magnetic and capacitive couplings influence on power losses in double circuit high voltage overhead transmission line

PurposeThe paper aims to discuss problems of power and energy losses in a double-circuit overhead transmission line. It was observed from energy meters’ readings, that in such a line, active power losses can be measured as “negative”. The “negative” active power losses appear when the active power injected to the circuit is lower than the active power received at the circuit end. The purpose of this paper is to explain this phenomenon.Design/methodology/approachTheoretical considerations based on mathematical model of the transmission line of π-type confirming that effect are presented. Power losses related to series impedance of the line and to shunt admittance are calculated. The theoretical considerations are confirmed by measurements done on the real transmission line.FindingsThe calculations allow to indicate components of the active power losses, i.e. related to electromagnetic coupling among wires of a given circuit, related to electromagnetic coupling between circuits and related to shunt capacitance asymmetry. The authors indicate the influence of the line/wires geometry on the active power losses in a double-circuit overhead transmission line.Originality/valueExplanation of the effect of “negative” active power losses’ measurement in a double-circuit overhead transmission line is provided in this paper.

Research on Safety Protection for Live Working on 1000kV AC Transmission Line with AC and DC Multi-circuit Transmission Lines

In recent years, in order to save line corridors and reduce the scope of demolition, some new transmission modes for high voltage AC and DC power transmission line are proposed. According to the characteristics of the parallel transmission line, this paper studies the distribution characteristics of the electric field intensity of multi circuit parallel transmission lines and the single circuit transmission line. Comparing and analysing the simulation results of the electric field strength, the safety measures for live working of 1000kV AC transmission line with multi circuit parallel transmission lines is put forward. That is the electric field protective equipment and measures used in the live line work of the 1000kV UHV AC single circuit line can meet the requirements of the live operation of the 1000kV UHV AC double circuit line.

Evaluation of the correctness of operation of adaptive under-impedance criterion for HV single and double-circuit overhead power line with increased capacity

Evaluation of the correctness of operation of adaptive under-impedance criterion for HV single and double-circuit overhead power line with increased capacity

Six-sequence Component Based Single Ended Fault Location Method of Transmission Line

Six-sequence component based single ended fault location method of transmission line went forward on the basis of line distributed parameter model. The same and reverse direction component can be obtained through the decoupling of the same tower, Based on the reverse current and voltage boundary conditions of different faults, the fault location algorithm of double circuit lines can be obtained. (Single line three phase fault and the cross line fault with the same name are excluded) The principle of the algorithm is not affected by transition resistance, system impedance and distributed capacitance. Besides, the algorithm only uses the current, hence it won’t be affected by the transmission characteristics of the voltage transformer. The precision of ranging is not affected by the characteristics of the current transformer is also theoretically proved. There is no pseudo root for the ranging equation and it has unique solution. The simulation results show that the proposed algorithm has high accuracy and can meet the ranging requirements of high voltage and ultrahigh voltage transmission lines.

Phase- and sequence-domain static models equivalent to long double-circuit transmission lines

The application of equivalent rather than nominal models of transmission lines in various areas of power system studies ensures the accuracy of results when the line length and hence distributed-parameter effect is significant. In this research, the static modeling of long double-circuit lines is comprehensively addressed. Equivalent models are analytically derived for them in different possible operating configurations, incorporating both mutual induction and capacitive coupling between the circuits. This is achieved by finding the solution to the differential equations characterizing the phase voltages and currents of the line circuits. Hence, the equivalent models are first derived in the phase domain, and then the equations are transformed into the sequence domain to obtain equivalent models of sequence networks. The accuracy of the models derived is validated via simulation studies in PSCAD/EMTDC.

Research on Total Electric Field for DC Lines Converted from Double-Circuit AC Lines

With rapid growth of power demand, transmission capacity is also in urgent need of upgrading. In some cases, converting existing AC transmission lines to DC lines can Improve the transmission capacity and reduce the construction investment. In this paper, the upstream finite element method was expanded to calculate the total electric field of same tower multi-circuit DC lines converted from double-circuit AC lines, and the validity of the algorithm was confirmed by experiments. Taking a DC line converted from a typical same tower 500 kV double-circuit AC transmission line as an example, the surface electric field and the ground total electric field in different pole conductor arrangement schemes were calculated and analyzed, and the critical height of pole conductors for DC lines in residential and non-residential area were determined. Then, the corridor width of DC and AC lines at critical height in residential and non-residential areas before and after AC-DC line transformation were compared. The results indicate that for DC lines converted from common 500 kV double-circuit AC lines, the ground total electric field can meet the requirements of corresponding standard with appropriate pole conductor arrangement schemes.

Optimization of electric and magnetic field emissions produced by independent parallel overhead power lines

This paper presents a method for determining optimal arrangements of parallel independent overhead power lines aimed to decrease electric and magnetic field emissions. The Genetic Algorithm (GA) is used to find the optimal placement of conductors. The Monte Carlo approach implemented in GA allows consideration of uncertain phase shifts between independent overhead power lines. The results and practical aspects of the proposed methodology are illustrated on two different configurations of both independent 400 kV singlecircuit and double-circuit overhead power lines.

Application of Local Environmental Data to the Lightning Performance Assessment of the IECo Transmission-Line Network

The paper reports on a second part of the lightning performance study that was conducted on overhead double-circuit lines 170 kV operated by Israel Electric Corporation (IECo). The first part of this study was published this year in TPWRD vol. 31 No. 2 ( [1] ) which introduces the local environmental data including a long-term lightning incidence records, tower footing resistance, and route terrain characteristics. The goal of the present paper is to demonstrate application of the data-inputs from [1] to analysis of the relationship between the line failure rate and its design and environmental parameters. The findings imply that the prevalent lightning failure mechanism in IECo Grid is direct-strike related. The acquired results prove a conclusion on that the ineffective shielding design in combination with local stroke current statistics, route topography, and long spans may seriously compromise line reliability, even with temperate local lightning activity. Disregarding the route terrain specificity may falsify the shielding flashover failure rate assessment and devaluate the line protection design.