Since high-voltage transmission lines extend tens or even hundreds of kilometers vertically and horizontally, they are in different environments. Therefore, the high-voltage transmission line is greatly affected by the geographical environment and climate, and the annual power outage accidents in the power grid are mainly caused by line accidents. The inspection of traditional transmission lines mainly relies on periodic inspections by operation and maintenance personnel. Although hidden dangers of equipment can be found, due to its own limitations and lack of detection of special environments and climates, changes in external forces in line corridors cannot be grasped in time during the vacuum period of the inspection cycle, which is very easy Before the next patrol, a line accident occurred due to lack of monitoring. Therefore, the application of UHV transmission line online monitoring system was born.
Due to the improvement of domestic people's living standards, the continuous advancement of science and technology, and the continuous improvement of control, the high-voltage power grid overvoltage online monitoring technology has taken the lead in the field of electrical systems, and the high-voltage power grid overvoltage online monitoring system has been widely used. In the field of power system design, the high-voltage power grid overvoltage on-line monitoring system has become a beautiful landscape at present, because it has many design resources, rich development experience, and most importantly, low cost, which is basically within the tolerance of buyers. Therefore, The design of over-voltage online monitoring system for high-voltage power grid has gradually become the focus of attention of countries all over the world. With the continuous innovation in the field of high-voltage power grid overvoltage online monitoring systems, the number is increasing, and it has gradually become the focus of research. Therefore, the new generation of us must seriously study the composition of high-voltage power grid overvoltage online monitoring systems.
This thesis debugs and corrects the overvoltage on-line monitoring system of the high-voltage power grid that has been designed, and analyzes the characteristics of the overvoltage waveform according to the operation results of the system hanging on the grid for more than one year. Based on the characteristic analysis and preliminary classification and summary of the overvoltage waveform, eight characteristic parameters such as overvoltage half peak time are proposed to characterize the internal and external overvoltage, and the support vector machine algorithm is used to realize the internal overvoltage and automatic discrimination of external overvoltage. The operation results show that the developed overvoltage online monitoring device operates stably and reliably, can record various overvoltage waveforms in the power grid well, meets the requirements of overvoltage online monitoring of high voltage power grid, and achieves the expected design goal.
Key words: high voltage power grid; overvoltage; fault protection; on-line monitoring; voltage sensor
Abstract
High-voltage transmission lines, which span tens or even hundreds of kilometers, are in different environments. Therefore, high-voltage transmission lines are greatly affected by the geographical environment and climate. Every year, power grid outage accidents are mainly caused by line accidents. Traditional transmission line inspection mainly relies on periodic inspection by operation and maintenance personnel. Although hidden dangers of equipment can be found, due to its own limitations, it lacks the detection of special environment and climate. In the vacuum period of inspection cycle, external force changes of line corridors cannot be timely grasped, which is easy to cause line accidents before the next inspection due to lack of monitoring. Therefore, the online monitoring system of UHV transmission line is applied.
Due to the improvement of the living standard of the domestic people, the continuous progress of science and technology, and the continuous improvement of control, so as to promote the high voltage grid overvoltage online monitoring technology in the field of electrical systems occupy the dominant position, but also make the high voltage grid overvoltage online monitoring system is widely used. In the field of power system design, the high voltage network overvoltage online monitoring system has become a beautiful landscape at present, because of its design resources, rich development experience, the most important is the low cost, basically within the buyer's range, so the high voltage network overvoltage online monitoring system design has gradually become the focus of the world. With the continuous innovation in the field of high voltage grid overvoltage online monitoring system, the number is increasing, and it has gradually become the focus of research. Therefore, the new generation of us should seriously study the composition of high voltage grid overvoltage online monitoring system.
This paper debugged and corrected the designed online monitoring system of high voltage grid, and analyzed the characteristics of the overvoltage waveform according to the operating results of the system for more than one year. Based on the characteristic analysis and preliminary classification of the overvoltage waveform, eight characteristic parameters such as the half peak time of overvoltage are proposed to characterize the internal and external overvoltage, and the automatic identification of the internal and external overvoltage is realized by using the support vector machine algorithm. The operation results show that the developed online overvoltage monitoring device runs stably and reliably, can well record a variety of overvoltage waveforms in the power grid, meets the requirements of online overvoltage monitoring in the high voltage grid, and achieves the expected design objectives.
Key words: High-voltage power network; Overvoltage; Fault protection; On-line monitoring; Voltage sensor
Table of contents
summary ................................................... ..................................... 1
Chapter 1 Introduction ................................... .......................... 1
1.1 Subject background and research status...................................... . 1
1.2 Research status at home and abroad................................... ........ 2
1.3 Significance of the subject research................................... .......... 4
1.4 Research content and chapter arrangement of the topic................... 5
Chapter 2 Basic Principles of Overvoltage On-Line Monitoring System ................... 6
2.2.1 Atmospheric overvoltage................................................... .......... 6
2.2.2 Internal overvoltage................................................... .......... 7
2.3 System Composition ................................................ .................. 9
2.4 The overall structure and working principle of the device... 9
Chapter 3 Analysis of Arc Light Grounding Overvoltage Protection Measures ... 11
3.1.1 High frequency arc extinguishing theory................................... ....11
3.1.2 Power frequency arc extinguishing theory................................... ....11
3.1.3 Dielectric Strength Restoration Theory.................................... 13
3.2 Model analysis of arc-to-ground fault..................................... 13
3.2.1 Analysis of neutral point ground fault through arc suppression coil... 13
3.2.2 Fault Analysis of Neutral Point Via Small Resistance System... 14
3.3 Reactive power compensation analysis of the system................................... .15
3.3.1 Selection of Reactive Power Compensation Equipment .................................. 15
Chapter 4 Research on Voltage Sensor at the End Screen of Transformer Bushing ... 18
4.1 Overview................................................... ................................ 18
4.2 Working principle of voltage sensor.................................... 18
4.2.1 Capacitive bushing................................................... .......... 18
4.2.2 Voltage sensor structure..................................... 19
4.3.1 Classification of Capacitors................................................... ... 20
4.3.3 Determination of Rated Working Voltage.................................................. 21
4.4 Design of protection unit................................... ...... twenty two
4.4.1 Varistors................................................... ........... twenty two
4.4.2 Gas discharge tube................................................... ....... twenty two
4.4.3 Relay protection unit.................................................... 23
4.5 Sensor error analysis................................................... ..... twenty three
Chapter 5 Simulation Analysis ................................... ................ 25
Chapter 6 Conclusion ................................................... ................... 27
Chapter 1 Introduction
1.1 Subject background and research status
With the implementation of the national "West-to-East Power Transmission" strategy, ultra-high voltage transmission lines will inevitably pass through high-altitude mountainous areas in western my country. Lightning activities are frequent in these areas, and the overvoltage of the power grid caused by lightning strikes will become an important factor affecting the safe operation of the system. The influence of overvoltage on the safe operation of power grid has been paid more and more attention. Operating experience shows that most of the various accidents in the power grid are caused by overvoltage in the system. Although a large number of fault recording devices are installed in the power system, due to the high amplitude, large steepness and short duration of the overvoltage, the voltage signal of the fault recorder is usually taken from the voltage transformer. Due to the limited conditions, it is impossible to accurately capture the occurrence process of overvoltage in the power system, which makes it very difficult to accurately analyze and judge the cause of overvoltage.
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