Secondary Arc Research Articles

Investigation of Arcing Time Prediction for Secondary Arc Based on Statistical Theory and Multivariable Regression Algorithms

Research on the secondary arc has long been important in the development of ultrahigh-voltage (UHV) transmission technology. Predicting the arcing time of secondary arc is important for single-phase automatic reclosing of the circuit breaker to protect the power system. In response to this problem, this study uses a multifactor variance model to select factors that significantly influence the arcing time and verifies its validity through residual analysis. The results show that the parameters of the circuit, such as wind direction, recovery voltage, secondary current, and arc length, significantly influence the arcing time. The density-based clustering algorithm (DBSCAN) is then used to remove outliers form the data, and the influence of each factor on the arcing time is analyzed through scatterplots. Finally, linear multivariate regression and nonlinear Gaussian process regression are used to fit the results. The results show that the linear regression has a good imitative effect. The proposed method is accurate and provides novel means of predicting the arcing time.

Influence of the Secondary Arc on the Operation of Single Phase Autoreclosure of the 400 kV interconnection between Hungary and Croatia


 
 Sažetak: Faults on EHV lines are generally single-phase-to-ground ones and not permanent in the majority of cases. Thus single phase auto reclosure (SPAR), at which the faulty phases are tripped for a short time, eliminates the predominant part of the faults [1,2]. The secondary arc, which follows the high power arc after tripping the faulty phases at both side of the line may endanger the successfulness of reclosing if the duration of the switched off interval (dead time) is not long enough to ensure the extinction of the arc. The secondary arcing times recorded on different EHV lines or measured in laboratory tests show significant spread, consequently, to select a dead time according to the longest experimental secondary arc extinction time is not feasible. During commissioning of the double circuit 420 kV interconnection between Hungary and Croatia several staged faults were initiated to analyze the arc extinction performance. Initially the line was in operation by connecting the two circuits in parallel along the 1/3rd of the full length. In this configuration the longest secondary arc extinction time was 4 seconds and the secondary arc has not extinguished in 27s in one of the tests, so the line had to be tripped out to clear the staged fault. Later on, the length of the Croatian section of the line has been significantly shortened after putting a new substation into service. The increased performance of SPAR of the new arrangement has been proved with field tests. A realistic representation of the secondary arcs is essential in determining the auto-reclosure performance of EHV transmission lines. As shown in the paper, the random variation of the arc parameters influences significantly the arc extinction time. The results of the field tests confirmed the importance of the distributed nature of the transmission line and the nonlinear characteristic of the arc resistance in the intermittent region of arcing, where temporary extinctions and sudden re-ignitions in the arc channel produce transient wave processes along the line.

Single-Pole Autoreclosure in uncompensated EHV AC mixed overhead-cable lines: A parametric time-domain analysis

The successful application of the Single-Pole Autoreclosure (SPAR) to Extra-High Voltage (EHV) overhead lines (OHLs), as well as to the overhead portion of EHV mixed cable-overhead lines (MLs), significantly improves system stability. SPAR success requires that the secondary arc self-extinguishes during the dead time: according to the literature, self-extinction times increase with the increase of both secondary arc current and recovery voltage. Steady-state analyses of EHV MLs not equipped with inductive shunt compensation showed larger secondary arc currents and smaller recovery voltages compared to OHLs. Since steady-state analyses cannot give indications on arc self-extinction times, transient studies are required to assess which of the above effects has a prevailing influence, i.e., whether SPAR in uncompensated MLs results hindered or facilitated. This paper presents a time-domain study of the SPAR cycle in an uncompensated 400 kV-50 Hz ML, making use of detailed ATP-EMTP line and fault arc models. A parametric study has been carried out, evaluating secondary arc current, extinction time and recovery voltage for different single-phase fault locations along the overhead section of the line. Transient simulation results point out to extinction times being shorter in MLs than in OHLs of the same total length.

Designing a Reactor for Use in High Voltage Power Systems and Performing Experimental and Simulation Analysis

Today, magnetically controlled shunt reactors are widely used in solving power quality problems. These reactors are designed to reduce system reactive power, control high super/special high voltage grid voltage, suppress power frequency, regulate overvoltage, eliminate generator excitation, dynamically compensate transmission line power charge, suppress secondary arc current, suppress system resonance. By using suitably designed silica plate core reactors at the input of the frequency converters in the electrical distribution system, the level of harmonic currents drawn from the electrical power distribution system can be reduced to certain rates. The core material, the air-gapped nature of the reactor core, and the sizing of the reactor have a great influence on the harmonic level of the current and its ability to reduce losses in the reactor. In this study, three reactors with different core materials and different air gap gaps are designed for a certain voltage value. Parametric analysis of the reactors designed to see the changes in inductance values depending on the load level has been made both theoretically and experimentally and using the Finite Element Method. As a result of the analysis, the inductance stability, losses and compliance of the reactors with the standards are presented. The reactor's magnetic circuit is modeled with ANSYS@Maxwell, realizing a solution based on this method. The magnetic circuit is simulated to see the behavior of the reactor. In addition, real-time verification of the designed alternating current reactor has been made. Optimum design was obtained by using different core materials and different core air-gaped tested experimentally. The effect of the air gap distance in the core on the magnetic field and inductance value was also obtained.

Extinction Accelerating Device of Secondary Arc Design Based on Wind Load

The rapid extinction of secondary arc on the transmission line is essential to the stable operation of power system. Recently, there are a few specific designs of secondary arc prevention device applied into operation condition. In this article, a low-voltage secondary arc model was carried out and the wind load was found to have a significant influence on the extinction characteristics of secondary arc. For further analysis, a dynamic model was established and found that the wind load perpendicular to the electrode direction could significantly accelerate the arc extinction. Consequently, a device for accelerating secondary arc extinction close to the insulator was designed. Wind directions and velocities were chosen as variables in the measurement for verification. The device could ensure that the upper electrode on the insulator string is in the direction perpendicular to the wind direction at any time, and it could promote the extinction of secondary arc. The proposal of the device could provide some practical reference for the protection of secondary arc on the transmission lines.

How weak twining lianas adapt to competition with host tree trunks: Case of Merremia boisiana.

Fierce competition exists between most stem‐twining lianas and the trunks of host trees. However, Merremia boisiana, a vigorous invasive twining liana, never strangles the host tree. Here, we investigated how M. boisiana stems adjust their twining growth to avoid intense competition with host trees, and how hydraulic conductivity is maintained for rapid asexual reproduction. We evaluated the effects of competition on twining M. boisiana stems (Em) and host tree trunks (Eh), compared differences in secondary growth between twining and creeping M. boisiana stems, calculated the total number of vessels (Nt), vessel density (Vmm−2), average vessel diameter (VDave), and percentage of vessels wider than 300 μm in diameter (P300) in the secondary xylem, and traced how these parameters change with increasing cross‐sectional area of stem (SA). The results showed that twining M. boisiana stems were competitively weaker, and mean Em (14.3%) was 21 times greater than that of Eh (0.7%). Secondary growth along the normal direction of the contact surface was significantly inhibited in stems twining on host trees. The lateral secondary growth of these stems was active, forming secondary vascular rings and/or arcs with abundant large vessels. Secondary growth in the central vascular cylinder was also significantly limited in extremely flat twining stems. Nt was positively and linearly correlated with SA. Vmm−2 and VDave fluctuated greatly in younger stems and tended to be stable in older stems. Nt and Vmm−2 did not significantly differ between twining and creeping stems, while VDave and P300 were both higher in twining stems compared to creeping stems of the same size. In conclusion, well‐developed lateral anomalous secondary growth prevents twining M. boisiana stems from fiercely competing with their host trees, while stable vessel density and wider, newly formed, vessels ensured sufficient hydraulic conductivity for the rapid asexual reproduction of twining M. boisiana stems.

A deep long Short-Term memory based scheme for Auto-Reclosing of power transmission lines

The operating speed of adaptive single-phase auto-reclosure (ASPAR) is of great importance to maintain power systems stability in high-voltage power transmission lines (PTLs). This paper proposes a two-step protection scheme using the long short-term memory (LSTM) network to enhance the ASPAR performance. The discrimination between transient and permanent faults is made by an LSTM with high accuracy in the first step. If transient faults are detected in the second step, another LSTM is applied to predict the secondary arc extinction time (SAET). To this end, the second LSTM accurately foresees the voltage waveform of the faulty phase a half-power cycle earlier, and predicts the SAET in order to get a successful reclosing. The results obtained from extensive simulations using EMTP-RV and MATLAB software environments indicate that the presented protection scheme outperforms other ones in terms of fault type classification, achieving an F-measure value of 98.90%. Moreover, the results verify that the LSTM can accurately estimate the voltage waveform and the SAET, that ensures a successful reclosing of the faulty phase.

Is the Ibero-Armorican Arc primary or secondary? An analysis of the contraction required to form it by rotation around a vertical axis

Various models have been proposed to explain the formation of the Ibero-Armorican Arc (IAA) as either primary or secondary (rotational). Models for secondary arc formation require significant rotation around a vertical axis at the end of the Variscan orogeny. Estimates for the amount of north–south (present coordinates) contraction (horizontal shortening) required for these rotations range from 54 at the core to 91% at the SE tip of the arc, near to the present day Mediterranean coast. These estimates are compared with coeval deformational structures developed in three areas of the orogen: (1) in the autochthonous hinterland in the southern branch of the arc; (2) in the Cantabrian Zone foreland fold–thrust belt in the core of the arc; and (3) in the SE continuation of the southern branch of the IAA in the present day Iberian Chain. From this analysis it follows that the contraction associated with late Variscan deformation is much less than that needed to explain the formation of the IAA from a formerly linear orogen via rotation around a vertical axis. We therefore propose that the geometry of the arc should be re-evaluated. We discuss the palaeomagnetic data purported to support the secondary origin, as well as the role of late Variscan regional strike-slip faults in modifying the geometry of the Iberian and Armorican massifs. Our analysis suggests that the IAA formed mainly from a primary non-rotational margin-controlled curvature, slightly modified by c. 5–20% of superposed contraction during late Carboniferous and/or Alpine times.

Experimental Study on the Extinction Characteristics of Secondary Arc Under Different Secondary Arc Currents Near Outdoor Insulator

On the transmission lines, the secondary arc is the arc that remains at the fault point after the short-circuit current is interrupted, which may pose a threat to the stable operation of the power system. In this article, the extinction characteristics of secondary arc near an outdoor insulator under different secondary arc currents are studied experimentally. The secondary arc has different extinction characteristics under different secondary arc currents of 10, 30, and 50 A. The arcing time, length, morphology, diameter, and breakdown voltage of secondary arc are discussed. Experimental results show that, with the increase in the secondary arc current, the arcing time also increases. The development of the secondary arc has stage characteristics. The length of the secondary arc increases steadily in the first stage and fluctuates greatly in the second stage. In addition, during the single discharge in the second stage, the morphology of the secondary arc will change significantly. The breakdown voltage of the upper electrode in the negative polarity is higher than that in the positive polarity, and it is found that this polarity effect is related to the motion of the secondary arc in space. The research results could provide some reference for investigating the physical characteristics and suppression measures of secondary arc.

Neutral Reactor Structures for Improved Single Phase Auto Reclosing in Multi-Circuit Multi-Voltage Transmission Lines

In this paper, novel neutral reactor structures are proposed to mitigate the secondary arc current (SAC) in non-conventional Multi-circuit Multi-voltage Transmission lines (MCMVTLs). The parameters of the reactors in the structure are optimized using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The optimization algorithm, coded in Python, regulates the multiple runs of an Electromagnetic Transients (EMT) simulation program to minimize the secondary arc current. The optimization trials are run in parallel on a 64 core computer to minimize the solution time. A detailed arc model was tested on the EMT program (PSCAD). Using this model and optimized parameters in the proposed neutral reactor schemes, the SAC is indeed extinguished in acceptable times. The SAC and TRV for neutral reactors with optimized parameters are up-to 68 and 77%, respectively, lower than the ones with parameters calculated by the conventional approach which ignores inter-circuit coupling. Meanwhile, the extinction times are up-to 46% faster. As a result, single-phase auto-reclosing in MCMVTLs is viable.

Unscented-Kalman-filter-based single-phase adaptive reclosing of shunt-compensated extra-high-voltage transmission lines

This paper proposes a novel two-stage adaptive reclosing mechanism for shunt-compensated extra-high-voltage transmission lines. In the first stage, secondary arc extinction peak-based criterion (SAEPC) is established to monitor the precise instant of secondary arc extinction. The approach depends on the magnitude of the faulty phase voltage and the estimated weighted lower-order harmonics. The harmonics root mean square factor (HRF) is presented in the second stage for fault classification, i.e., temporary or permanent. The proposed scheme not only identifies the quenching instant regardless of fault location, compensation level, and arc extinction speed but also determines the nature of the fault. Simulation studies demonstrate the effectiveness and reliability of the proposed scheme and its ability to mitigate the limitations of existing single-criterion harmonics-based reclosing techniques.

전기화재 원인분석을 위한 실험실 데이터를 활용한 1차, 2차 단락흔 및 열흔 판별용 CNN 알고리즘 설계

In this paper, a new CNN algorithm is proposed to determine the direct cause of electric fires. We create 10,000-15,000 three types of data that can occur at a fire scene in our laboratory, and then train and verify it through the proposed CNN algorithm. As a result of the experiment and analysis, the classification accuracy of the primary and secondary arc beads was 86.2%, the accuracy of arc beads and molten marks was 93.6%. And also, the classification accuracy of the primary and secondary arc beads and molten marks was 92.4%. The results of this study are meaningful in that fire forensics can provide accurate identification results in a shorter time through artificial intelligence algorithms compared to the existing methods of identification through visual classification and physicochemical material analysis methods. In particular, the classification between primary and secondary arc beads is known to be a very difficult problem. However, the results of this study provided more than 86% classification ability.

Analysis of transient recovery voltage and secondary arc current in transposed extra-high voltage lines in a two-phase auto-reclosing

Extra-high voltage (EHV) lines of 500–750 kV, providing transmission of electricity over long distances and at the same time performing the functions of intersystem communication at the level of the national power system, play an important role not only in normal modes, but also in emergency modes, ensuring the dynamic stability of the power system as a whole. In these lines, the overwhelming proportion of power cuts are caused by single-phase short circuits (90%), a significant part of which, being unstable arc faults, are successfully eliminated in the single-phase auto-reclosing cycle. Also, about 5%–10% of failures can be constituted by two-phase short circuits, which can be eliminated in a two-phase auto-reclosing cycle (TPhAR). The purpose of this paper is to study two-phase auto-reclosing in transposed EHV lines equipped with four-radial shunt reactors (ShR). The paper analyzes the efficiency of using a two-phase auto-reclosing to eliminate two-phase short-circuits in the lines connecting the power systems of Kyrgyzstan and Tajikistan. An algorithm is proposed for calculating the transient recovering voltages (TRV) and secondary arc currents (SAC) in the real transposed line Datka–Khujand–Dushanbe. The obtained results of TRV and SAC, which are within the permissible limits for the Dushanbe–Khujand line section, make it possible to have a dead time of TPhAR of no more than 0.6 s, in order to maintain the dynamic stability of the power system. For lines with a length of about 500 km (Datka–Khujand), equipped with three reactors, a successful TPhAR is impossible due to the appearance of resonant TRV in the circuit. The paper proposes the use of banks of capacitors connected in series in the phases of the ShR for the implementation of a successful TPhAR with the duration of the required pause of about 0.6 s.

Effect of extended grading capacitor on the interrupting performance of multi-break circuit breaker during out-of-step faults

The extended grading capacitor (EGC) installed in parallel to multi-break circuit breaker (CB) chamber is a promising technique to suppress secondary arc. The effect of EGC on the interrupting performance of CB during is investigated in this paper. As CBs are subject to various operating burdens in practice, this paper is mainly devoted to the out-of-step fault. Considering the most severe condition, an equivalent circuit model for UHV line is established; the voltages on power source side and line side are derived based on Laplace transform and travelling wave theory, respectively; the expressions of transient recovery voltage (TRV) across CB contact are obtained, and hence the rate of rise of recovery voltage (RRRV). Since the CBs of two power source sides are often cleared asynchronous with a very small-time deviation, the characteristics of TRV waveform for them are separately computed and analysed. Furthermore, a series of sensitivity analysis have been performed. The influences of phase angle, parallel line, shunt reactor as well as reclosure on the interrupting performance are discussed. The results suggest that performance of CB during out-of-step fault is jointly determined by phase angle, parallel line, and especially the reclosure strategy. The EGC can smooth the TRV significantly especially during the first few microseconds of out-of-step fault, the breaking capability would be enhanced.

Multicomponent Plasma Expansion Model for Arc Discharges on Large-Area Solar Arrays

For decades it has been known that spacecraft charging-induced electrostatic arc discharge on solar arrays can cause cell degradation and damaging secondary arcs. While discharging on large-area solar arrays is the concern, there is no space data on primary arc current magnitudes on large arrays. Laboratory testing is normally performed on coupons with just a few solar cells. External capacitors and circuitry based on theoretical models are used to simulate the arc current profile from the charge stored on the rest of the array. Previously, the current profiles for large arrays were generated assuming that the arc plasma expanded at a constant velocity and instantaneously discharged cells at the plasma perimeter. Arc-current profiles using this perimeter model failed to agree with laboratory tests on large arrays. An improved model needs to account for the range of expansion velocities in a multicomponent plasma, and that the cell neutralization at the perimeter is not instantaneous but is limited by the arc-plasma thermal electron current density. A new, multifluid model of arc-plasma expansion addresses both concerns. The model assumes as input primary arc ion generation rates. Ion expansion velocities are calculated self-consistently from electric potentials in the expanding plasma.

Study on the Influence of Injected Lightning Current on the Space-Time Evolution of Secondary Arc

The timely extinction of secondary arc is of great significance to the single-phase reclosing of transmission lines. However, very little research has been carried on the space-time evolution of secondary arc under lightning strikes. In this article, considering the electromagnetic force, thermal buoyant force, wind load and air resistance in the motion of secondary arc, a chain arc model was established, which was combined with the double exponential function injected lightning current model. The motion of secondary arc and the change of arc extinction time with or without injected lightning current were observed. The results show that lightning could accelerate the motion of secondary arc and shorten the extinction time of secondary arc. Then, by adjusting the different parameters of injected lightning current function, lightning start time, and lightning duration, the impact of various factors on the motion process of secondary arc and extinction time was obtained. Different wind loads and secondary currents were selected to observe the impact of the same injected lightning current with different secondary current and arc movement environment. The results show that a higher injected lightning current level and a lower secondary current could both make the impact of the injected lightning current more obvious. The lightning duration and lightning start time would not have a significant impact on the extinction of secondary arc. Lightning can reduce the difference between secondary arcs under different winds, and further promote the extinction of secondary arcs. The abovementioned research work can provide some reference for the protection of secondary arc in thunderstorm field.

Graphical Method for Calculating Secondary Arc Currents of an Arc in High-Voltage Lines

Graphical Method for Calculating Secondary Arc Currents of an Arc in High-Voltage Lines

Optimizing multi-circuit transmission lines for single-phase auto-reclosing

In this paper, novel multi-circuit transmission line (MCTL) designs with low secondary arc current (SAC) values are proposed. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) was used to generate the optimized tower structures. The aim is to select the MCTL configuration that satisfies multiple objectives such as increased capacity, reduced cost, right-of-way (ROW), and tower height, while satisfying several constraints such as SAC limit, ampacity, electric field, etc. The objective function is formulated as a mathematical function of design variables such as sub-conductor position, phase arrangement, etc., and several constraints. Two-port theory is used to calculate the SAC resulting from different faults along the line, which is significantly faster compared with time-domain Electromagnetic Transient (EMT) simulations. Comparisons of MCTLs with and without SAC constraints are presented, clearly showing the importance of taking into account SAC limits during the optimization process. As a result, MCTL structures with SAC reductions of up-to 64% were obtained, indicating that the MCTL are able to successfully handle Single Phase Auto-Reclosing (SPAR).

Графический метод расчёта вторичных токов дуги в линиях сверхвысокого напряжения

The article discusses the issues of calculating secondary arc currents in the implementation of single-phase auto-reclosing for the elimination of unstable single-phase damages in ultra-high voltage lines of 500, 750 kV. The dependences of the extinguishing time of the feeding arc and the dead time of the single-phase auto-reclosing recommended in the literature on the amplitude of the forced component of the secondary arc current are given. A graphical method is proposed for calculating the secondary arc currents in ultra-high voltage lines in the dead time mode of the single-phase auto-reclosing. The adequacy of the simulation of the recharge arc is confirmed by comparing the calculated and experimental data as applied to the 750 kV line with a length of 525 km. Examples of using the graphical method for calculating the secondary currents of the recharge arc in 500 kV lines of various lengths are given. The features of the implementation of single-phase auto-reclosing in the line with a length of 300 and 1000 km and, in particular, the influence of zero-power reactors included in the neutral of shunt reactors are noted. An example of the implementation of single-phase auto-reclosing using automatic phase shunting in a 500 km line is also considered.

Influence of extended grading capacitor for suppressing secondary arc on the transient recovery voltage of multi‐break circuit breaker

Influence of extended grading capacitor for suppressing secondary arc on the transient recovery voltage of multi‐break circuit breaker