Quadruple-circuit Transmission Lines Research Articles

Experimental and Analytical Studies on Lightning Surge Response of the Quadruple-Circuit Transmission Line

The compact design of a 500 kV quadruple-circuit transmission line can effectively reduce the line corridor area, but the height of the tower also increases, increasing the probability of suffering a lightning strike. The 500 kV quadruple-circuit transmission lines carry more energy, and because of this, lightning strikes that cause power line trips are more likely to result in large-scale power outages. Therefore, it is necessary to make an accurate assessment of the lightning performance of 500 kV quadruple-circuit transmission lines. First, simulated lightning-striking experiments were carried out on a scaled 500 kV quadruple-circuit transmission line in the laboratory, where transient voltages and currents were measured. Second, a numerical model was established with the Finite-Difference Time Domain (FDTD) method, which was then verified with the experimental results. Third, lightning surge responses of a 500 kV quadruple-circuit transmission line under near-real facility conditions are estimated with the verified FDTD model. In the simulations, influencing factors, such as the rise time of injecting current, the velocity of return-stroke current and the terrains, were taken into consideration, but not in previous lightning surge analysis with the Electromagnetic Transients Program (EMTP). Results show that insulator voltages on the same tower cross-arm are nearly identical, although the length of the cross-arm is large enough. Furthermore, it is found that the rise time and the lightning current velocity have great effects on the lightning surge response, and the terrains are less impactful but not negligible. Therefore, these factors should be considered carefully where higher accuracy lightning protection design is necessary.

Adaptability of phase selectors based on phase‐to‐phase superimposed currents when confronting cross‐voltage faults in mixed‐voltage quadruple‐circuit line system

For the mixed-voltage quadruple-circuit transmission lines on the same tower, its special construction form makes the cross-voltage faults, i.e. multi-circuit faults that occur between different voltage level systems, easy to occur. Although the phase selector based on phase-to-phase superimposed currents (PTPSC) shows excellent performance in the single transmission line, it cannot guarantee to identify faulted phases when confronting cross-voltage faults. In this study, the adaptability of phase selectors based on PTPSC is analysed and a new method of phase selection is put forward. First, the PTPSC measured by the relay can be obtained on the basis of cross-voltage short-circuit calculation. Then, the influencing factors and possible selection results are comprehensively analysed, and the corresponding measure has been proposed. Finally, a fault model of mixed-voltage quadruple-circuit transmission lines is constructed in PSCAD and simulation results agree well with the theoretical analysis, verifying the validity of this method.

Cross‐voltage short‐circuit calculation for mixed‐voltage quadruple‐circuit lines on the same tower

Cross-voltage faults, i.e. multi-circuit faults that occur between different voltage level systems, in mixed-voltage quadruple-circuit transmission lines occur at times. The short-circuit calculations, which are the basis of the relay protection settings, for different faults are required. This study proposes a new method based on the theory of multiple fault analysis. First, the cross-voltage fault is regarded as a double multiple fault of the system. By retaining the fault nodes and the ground node, while eliminating all the intermediate nodes, the equivalent impedance of each sequence is obtained. Next, the fault reference phase is selected and the two-port network of each sequence that belongs to the reference phase is formed. Further, the port voltages of each sequence are transferred to a special phase using phase-shifting transformers. Then, a unified composite sequence network is formed according to the boundary conditions of the special phase. Finally, a set of equations are listed based on the composite sequence network in order to determine the fault currents and voltages. The simulation results in PSCAD agree well with the results calculated using the above algorithm, verifying the accuracy of this method.

Backflashover rate of quadruple-circuit transmission lines due to first and subsequent return strokes

The backflashover rate (BFR) of typical 220/110kV quadruple-circuit transmission lines due to direct negative first and subsequent return strokes and the effects of common lightning protection measures are quantified. The method based on ATP-EMTP and IEEE electro-geometric model (EGM) is adopted. The results show that the peak current distribution of the first and subsequent stroke has great influence on the BFR. The subsequent strokes propagate along the first stroke channel may lead more multi-circuit trip-out than the first stroke. The influence of tower foot resistance on single and double circuit BFR due to the first stroke is more serious than that due to subsequent strokes. The protection measures of unbalanced insulation, insulation strengthen and coupling ground wire are effective for BFR due to first and subsequent strokes.

Improving the lightning protection effect of multi-circuit tower by installing coupling ground wire

Erecting coupling ground wire is a type of effective lightning protection measure to reduce trip-out rate of back flashovers. Nowadays coupling ground wires has been applied on some multi-circuits transmission lines in China. However, various setting positions of coupling ground wire have different impacts on the lightning protection effects, especially the multi-circuit lines. Taking the typical 500/220kV and 220kV quadruple circuit transmission lines for example, the paper presents and analyzes the effects of setting coupling ground wire on the center of cross-arm at different heights. The shunt coefficients of tower, ground wires and coupling ground wire, and the coupling coefficients are also compared and discussed in situations that the coupling ground wire is mounted in different positions.

Lightning Performance and its Prevention for Quadruple-circuit Transmission Line with 220kV/110kV Voltage in a Tower

According to the physical process of discharge development of insulator that is struck by lightning, the lightning flashover model for quadruple-circuit transmission line with dual voltage 220kV/110kV in same tower is established basing on EMTP. The actual evaluation index of lightning protection performance is adopted with the consideration of influence of system voltage. The characteristics of multi-circuit trip-out simultaneously for mixed-voltage lines in same tower is studied, and the distinctions of lightning protection performance caused by differentiated configuration mode of lightning protection measures including phase sequence arrangement, coupling ground wire and so on. The results indicate that the lightning withstand level fluctuates approximately with the phase angle in the form of non-standard sinusoidal wave. The lightning withstand level emerges as optimum performance under the completely reversed phase sequence. The effect of coupling ground wire on top of tower is superior to that on bottom. DOI: http://dx.doi.org/10.11591/telkomnika.v11i10.3413

Design and Full-Scale Test for Steel Tubular Tower of UHV and EHV Quadruple-Circuit Transmission Line on the same Tower

State Grid Corporation of China has carried out research on key technology of UHV&EHV AC and DC multi-circuit transmission lines, the research on material and structure of transmission tower is the important part. The SSZT2 tower, on which 1000 kV AC double-circuit and 500 kV AC double-circuit are arranged, is the largest power transmission capacity all over the world. Q420 high-strength tubular steel, the plug-in boards and forging flanges are used in SSZT2 tower,and the forging flange with strength classification is applied for the first time. Through the monographic study on the tower structures, wind vibration coefficient, and biaxial bending of steel tube etc. The success of full-scale test verified the reliability in design and manufacture of multi-circuit steel tubular tower for UHV and EHV. Research results of this paper can be applied in UHV transmission line projects.

Assessment of the lightning performance of quadruple-circuit transmission lines with steel and wooden crossarms

Abstract With recent interest in the use of 275 kV and 132 kV multicircuit transmission lines in Malaysia, a computer program has been developed to evaluate the lightning performance of such lines. The program is basically an extension and improvement of an earlier program developed by Sargent and Darveniza for evaluation of double-circuit outage rates and uses the Monte Carlo and dynamic travelling wave techniques. Improvements incorporated include the use of the electrogeometric model to determine the stroke termination point, dynamic representation of the footing resistance, arc quenching by wooden members and determination of the transition from impulse flashover to power arc formation for every flashover path. The program developed is used to study the lightning performance of a steel-tower, quadruple-circuit, 132 kV line with wooden crossarms, now in operation in Malaysia.

Comparative studies of lightning performance of a quadruple-circuit dual voltage 275/132 kV transmission line design with wooden crossarms

This paper describes a transmission line lightning performance analysis program QCORTL which is able to predict single and multi-circuit flashover and outage types and rates of a quadruple circuit transmission line. It employs the Monte Carlo statistical technique to select lightning and system parameters and the dynamic travelling wave technique to calculate overvoltages on transmission line towers. The program has also incorporated nonlinear corona effects, the dynamic response of soil and the modelling of wooden-crossarms for arc-quenching in its calculations. The assessment of a Malaysian quadruple circuit dual voltage 275/132 kV transmission line using this program is demonstrated to illustrate the detailed nature of the analysis that is suitable for insulation design of transmission lines. >