Influence Estimation of the On-Load Tap-Changing Transformeron the Currents in Schemes of Ice Melting on Overhead Transmission Lines

2020 ◽  
Vol 63 (5) ◽  
pp. 86-90
Author(s):  
Alexander Zasypkin (jr.) ◽  
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Linear Interpolation ◽  
Ice Melting ◽  
Imped Ance ◽  
Technical Data ◽  
Melting Current ◽  
Transformer Ratio ◽  
Current Calculation ◽  
Dc Current

The influence of regulated under load transformer's (on-load tap-changing transformer) ratio and imped-ance on the short circuits’ currents and currents in the schemes of ice melting with AC and DC current is ana-lyzed. Accounting for changes in the transformer ratio is not difficult as it is provided in the technical data for all branches (tap positions). The transformer resistances used in the calculations, which are reduced to the un-regulated side of the transformer, are proportional to the short-circuit (SC) voltages. SC voltages are known, according to GOST, only for three tap positions - main (middle) and two extreme (top and bottom) positions, and for other tap positions are determined approximately according to different methods. It is shown on the typical example, that the error of the melting current calculation is significantly less than the error of the ap-proximated transformer's resistance calculation by the method of linear interpolation of resistances, the error of which for different types of on-load tap-changing transformers does not exceed 3 %.

scholarly journals A Novel Overcurrent Suppression Strategy during Reclosing Process of MMC-HVDC

2019 ◽  
Vol 9 (9) ◽  
pp. 1737 ◽  
Author(s):  
Bin Jiang ◽  
Yanfeng Gong
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Current Method ◽  
Short Circuit Current ◽  
Simulation Software ◽  
Fault Current ◽  
Overhead Lines ◽  
Hvdc System ◽  
Electromagnetic Transient Simulation ◽  
Current Calculation

A modular multilevel converter based high-voltage DC (MMC-HVDC) system has been the most promising topology for HVDC. A reclosing scheme is usually configured because temporary faults often occur on transmission lines especially when overhead lines are used, which often brings about an overcurrent problem. In this paper, a new fault current limiter (FCL) based on reclosing current limiting resistance (RCLR) is proposed to solve the overcurrent problem during the reclosing process. Firstly, a mesh current method (MCM) based short-circuit current calculation method is newly proposed to solve the fault current calculation of a loop MMC-HVDC grid. Then the method to calculate the RCLR is proposed based on the arm current to limit the arm currents to a specified value during the reclosing process. Finally, a three-terminal loop MMC-HVDC test grid is constructed in the widely used electromagnetic transient simulation software PSCAD/EMTDC and the simulations prove the effectiveness of the proposed strategy.

scholarly journals Thermodynamic model of critical ice-melting current on iced transmission lines

2019 ◽  
Vol 23 (5 Part B) ◽  
pp. 3187-3198
Author(s):  
Yong-Can Zhu ◽  
Xin-Bo Huang ◽  
Long Zhao ◽  
Yi Tian ◽  
Jing-Yu Mu ◽  
...  
Keyword(s):  
Transmission Lines ◽  
Heat Conductivity ◽  
Liquid Water Content ◽  
Attack Angle ◽  
Ice Storm ◽  
Ice Melting ◽  
Joule Effect ◽  
Current Increase ◽  
Simulation And Experiment ◽  
Melting Current

The thermal de-icing by Joule effect is a mostly valid way to prevent transmission-lines from the severe ice storm. A model was put forward to simulate the critical ice-melting current on iced conductor. Based on this model, the value of critical ice-melting current was calculated with various parameters, some of which were ignored in the earlier literatures, such as ice-layer heat conductivity, wind attack angle, and icing section shape. The results of the experiment and simulation show that the critical ice-melting current increase with wind speed, wind attack angle, and ice-layer heat conductivity, but decrease rapidly with ambient temperature and liquid water content. Moreover, the maximum difference between the results of simulation and experiment is about 9%, thus this model can be employed to estimate the engineering parameters in practical thermal de-icing projects.

Mathematical Model of Ice Melting on Transmission Lines

2006 ◽  
Vol 6 (2) ◽  
pp. 273-286 ◽  
Author(s):  
S. Yu. Sadov ◽  
P. N. Shivakumar ◽  
D. Firsov ◽  
S. H. Lui ◽  
R. Thulasiram
Keyword(s):  
Mathematical Model ◽  
Transmission Lines ◽  
Ice Melting

scholarly journals Theory and Design of a Flexible Two-Stage Wideband Wilkinson Power Divider

Electronics ◽  
2021 ◽  
Vol 10 (17) ◽  
pp. 2168
Author(s):  
Antra Saxena ◽  
Mohammad Hashmi ◽  
Deepayan Banerjee ◽  
Muhammad Akmal Chaudhary
Keyword(s):  
Transfer Function ◽  
Transmission Lines ◽  
Short Circuit ◽  
Wide Band ◽  
Power Divider ◽  
Design Parameters ◽  
Two Stage ◽  
Quarter Wave ◽  
Band Pass ◽  
Wilkinson Power Divider

This article presents the design scheme of a wideband Wilkinson Power Divider (WPD) with two-stage architecture utilizing quarter-wave transmission lines and short-circuit stubs. The bandwidth of the proposed WPD is flexible and can be controlled using the design parameters. The proposed design achieves excellent isolation between output ports in addition good in-band performance. The analysis of the proposed circuit results in a simplified transfer function which is then equated with a standard band-pass transfer function to determine the parameters of transmission lines, stub’s impedances, and the value of the isolation resistors. Furthermore, it is also demonstrated that a simple alteration in the proposed circuit enables the design of a wideband DC isolated WPD that maintains a good in-band and isolation performance. A number of case studies have been included to highlight the flexibility of the proposed design. Two distinct prototypes are developed on different boards to demonstrate the wideband performance of the proposed design. An excellent agreement between the experimental and measured results for both the designs over a wide band including very good isolation between ports validate the proposed design.

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