The UHVDC Transmission Line Lightning Disturbance Identification Based on the Morphology

2014 ◽  
Vol 1008-1009 ◽  
pp. 603-609
Author(s):  
Rui Rui Cao ◽  
Ju Rui Yang
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Low Frequency ◽  
Transient State ◽  
Spectral Energy ◽  
Complex Signal ◽  
Main Criterion ◽  
Lightning Stroke ◽  
Multi Scale ◽  
Overhead Transmission Lines

Research and identify overhead transmission lines’ transient characteristic which was caused by lightning stroke is significant to develop the protection and improving its reliability based on transient state. A complex signal can be resolved into several parts which have respective physical meanings by mathematical morphology’s multi-scale decomposition and this can reveal the local features of waves. Therefore, the transient current of ±800 kV UHVDC transmission lines, caused by the non-fault lightning stroke, fault lightning stroke and other line short circuit, can be decomposed by the multi-scale morphology decomposition to extract the spectral energy from the high and the low frequency bands, and the ratio of those two spectrum energy forms main criterion to realize the identification between lightening disturbance and the fault states. According to the ratio of the maximum of the current’s amplitudes of decomposition waveform of the first head of current’s second scale and sixth scale, to further distinguish the lightning stroke fault from the line short circuit. Extensive simulations show that the approach is correct and effective.

scholarly journals An Optimized Coordination Strategy between Line Main Protection and Hybrid DC Breakers for VSC-Based DC Grids Using Overhead Transmission Lines

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1462 ◽  
Author(s):  
Zheng ◽  
Jia ◽  
Gong ◽  
Zhang ◽  
Pei
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Short Circuit ◽  
Power Grids ◽  
Fault Line ◽  
Long Distance ◽  
Coordination Strategy ◽  
Overhead Transmission Lines ◽  
Depth Analysis ◽  
Dc Breaker

Compared with alternating current (AC) power grids, the voltage-sourced converter (VSC)-based direct current (DC) grid is a system characterized by “low damping”, as a result, once there is a short-circuit fault on the DC transmission line, the fault current will rise more sharply and the influence range will be much wider within the same time scale. Moreover the phenomenon that a local fault causes a whole power grid outage is more likely to occur. Overhead transmission lines (OHLs) have been regarded as the mainstream form of power transmission in future high-voltage, large-capacity and long-distance VSC-based DC grids. However, the application of overhead transmission lines will inevitably lead to a great increase in the probability of DC line failure. Therefore, research on how to isolate the DC fault line quickly is of great significance. Based on the technology route for fault line isolation using DC breakers, on the basis of in-depth analysis of traditional coordination strategy, an optimized coordination strategy between line main protection and a hybrid DC breaker for VSC-based DC grids using overhead transmission lines is proposed in this paper, which takes the start-up output signal of line main protection as the pre-operation instruction of the corresponding hybrid DC breaker. As a result, the risks of blockage of the modular multilevel converter (MMC) closer to the fault position and of damage to power electronic devices in main equipment can be reduced effectively. Finally, the proposed coordination strategy was verified and analyzed through simulation.

Grounding Connections

2018 ◽  
pp. 84-123
Keyword(s):  
Transmission Lines ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Power Sources ◽  
Grounding Resistance ◽  
Overhead Transmission Lines ◽  
Ground Fault ◽  
Multiple Power

This chapter sheds light on the following: TT system (earthed neutral), automatic disconnection for TT system, TN system (exposed conductive parts connected to the neutral), TN-C system, TN-S system- TN-C-S system, IT system (isolated or impedance-earthed neutral), IT system (impedance-earthed neutral), grounding transformer connection and design, grounding of industrial and commercial generators, Zigzag grounding transformer earthed systems (solid grounding, resistance grounding, reactance grounding, resonant grounding (ground-fault neutralizer), location of system grounding points selection and grounding locations specified by the NEC and multiple power sources. The chapter contains also the different methods used in determining the levels of short circuit current. It contains also details about the grounding through resistances for transformers and generators and reactances for overhead transmission lines.

scholarly journals Short circuit fire risk assessment in investigating and examining fires caused by emergency modes in overhead transmission lines

2022 ◽  
Vol 6 (4) ◽  
pp. 363-368
Author(s):  
Yu. S. Kozlova
Keyword(s):  
Transmission Lines ◽  
Fire Hazard ◽  
Short Circuit ◽  
Electric Power System ◽  
Ignition Source ◽  
Electrical Network ◽  
Fuel Load ◽  
Overhead Transmission Lines ◽  
Protection Devices ◽  
Short Circuits

Emergency modes (short circuits) in electric power system and equipment are the main technical cause of fires. However, it is not always possible to prove the involvement of a particular operating mode in a fire. The fire hazard can be due to three components: a fuel load, an oxidizer and an ignition source. Since overhead transmission lines are used in an open space, they are oxidized. The presence of a fuel load is confirmed by a fire. The source of ignition should be identified. The aim of the study is to develop an algorithm for assessing the fire hazard for short circuits in overhead transmission lines with 1000 V. The study was conducted using scientific analysis, physical experiment and simulation. The ignition source is due to the appearance of an energy source with parameters sufficient to ignite a fuel load. The probability of ignition in overhead line wires depends on the probability of occurrence of the short circuit itself  ( Qi (v1) ) , the probability of failure of protection devices  ( Qi (v2) ), and the probability that the electric current value in the event of a fault is in the range of fire hazard values (Qi(z)). The values of the first two components are determined on the basis of statistical data, taking into account the theory of reliability. The third component is based on the experiment results. The experimental studies made it possible to establish the ranges of fire hazard values for uninsulated aluminum wires of various cross-sections, thereby providing the possibility of calculating ( Qi (z). Using the data obtained and information about the nature of changes in short-circuit currents and performance characteristics of protection devices, depending on the line length, an algorithm for assessing the fire hazard for a short circuit was developed. The results make it possible to assess the fire hazard for short circuits in various sections of the electrical network, made by overhead transmission lines, and to establish the involvement of sparks generated by short circuits in a fire

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