A new decoupling method for asymmetry‐parameter quadruple‐circuit lines on same tower

Abstract

Quadruple‐circuit lines with different self‐impedances have been applied in power system with the development of power industry. However, the different self‐impedances in quadruple‐circuit lines will cause problems in fault analysis and related relay protection in the lines. The impedance matrix of these lines is different from that of symmetrical lines, and existing methods cannot completely eliminate all mutual impedance. A new method is proposed to decouple these asymmetrical quadruple‐circuits lines in this paper. The phase‐to‐phase mutual impedance is eliminated first, and then the line‐to‐line mutual impedance is eliminated according to the circulating current method. The mathematical deduction is formulated to ensure the complete decoupling of the impedance matrix. The fault conditions can be used to obtain the relationship between the independent sequence networks, which can be used to calculate the fault current. Power Systems Computer Aided Design (PSCAD) simulations indicate that the decoupling method is suitable for fault analysis of the quadruple‐circuit lines with different self‐impedances. The related fault analysis method is quite accurate and easy to be applied. The fault analysis accuracy is not affected by the fault resistance, fault type, fault location, or length of lines. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

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

“…Eventually, the composite sequence network of the C-a fault can be drawn as shown in Fig. 7 and the unknown variables can be obtained according to (5), (6), (12), (14), and (16).…”

“…The researches involving faults in mixed-voltage multi-circuit line systems [10][11][12][13][14] mostly target single-circuit faults or cross-line faults in the same voltage level [10,11], whereas only a few of them focus on the cross-voltage faults [12][13][14]. In addition, the sixsequence or the twelve-sequence component method cannot be used directly for cross-voltage faults owing to asymmetrical line parameters.…”

“…The authors of [12][13][14] significantly contribute to research studies that deal with cross-voltage faults. On the basis of a unified zero sequence network of two different voltage level systems, a method for a unified composite sequence network has been put forward in [12].…”

“…On the basis of the sixsequence component method, Lu et al [13] propose a new solution that can accurately calculate the cross-voltage fault current of the mixed-voltage quadruple-circuit transmission lines on the same tower under a condition that these two different voltage-level systems do not have a strong electrical contact. A new method is proposed to decouple the asymmetrical quadruple-circuit lines in [14]. The phase-to-phase mutual impedance is eliminated first, and then the line-to-line mutual impedance is eliminated according to the circulating current method.…”

Analysis of the Influence of the Insulation Parameters of Medium Voltage Electrical Networks and of the Petersen Coil on the Single-Phase-to-Ground Fault Current

“…For the correct adjustment of the protective relays, it is important that the analytical determination of the single-phase-to-ground fault current is made with the best possible accuracy. In the analysis of the protective relay settings, it must be taken into account that in the case of medium voltage networks with a resonant ground system, the current intensity values when the fault is single phase are low, which is the reason why unbalanced three-phase loads can significantly influence the value of these currents [5,6,[12][13][14][15][16][17][18][19]. Ensuring the resonance regime of medium voltage networks with a resonant ground system requires the need to make coils with controllable parameters [20][21][22] which can be changed depending on the characteristics of the medium voltage network.…”