本文選題：電力變壓器 + 差動保護�。� 參考：《青島科技大學》2016年碩士論文

【摘要】：隨著社會科學技術(shù)的飛快進步,人類文明的不斷發(fā)展,電力工業(yè)也步入以特高壓、高智能化為特點的新階段,用戶對供電系統(tǒng)的可靠性、穩(wěn)定性、安全性等方面的要求越來越高。大型電力變壓器作為為電力系統(tǒng)不可缺少、無法替代的重要電氣設(shè)備,如果發(fā)生故障后不能得到迅速正確地處理,將會給整個系統(tǒng)帶來嚴重的危害,因此電力變壓器的繼電保護工作十分重要。本文針對電力變壓器的差動保護與后備保護,展開了深入研究。首先,對電力變壓器差動保護原理與各種后備保護原理進行深入學習,并在SIMULINK平臺上分別搭建了具有雙側(cè)電源的雙繞組變壓器系統(tǒng)仿真模型與具有多路出線的三繞組變壓器系統(tǒng)仿真模型。通過分析仿真結(jié)果,驗證兩個模型能夠正確的模擬仿真變壓器空載合閘產(chǎn)生勵磁涌流,以及變壓器主保護區(qū)內(nèi)外發(fā)生的各種電氣量故障,為研究提供了仿真平臺。針對傳統(tǒng)差動保護涌流制動方法的局限性,在深入學習小波變換的基礎(chǔ)上,本文選擇用db4小波函數(shù)對勵磁涌流與故障電流進行5層小波分解處理,觀察分析各種情況下的勵磁涌流與各種故障下的故障電流的小波變換特點。通過分析二者各層系數(shù)變化情況,本文提出一種基于小波系數(shù)分布為判據(jù)的勵磁涌流識別新方法。該方法通過對小波變換后所得二尺度上的小波系數(shù)進行提取,計算其方差的變化情況,并設(shè)定合理的判據(jù),來對勵磁涌流與故障電流進行區(qū)分。通過仿真結(jié)果驗證,本方法能夠快速準確地區(qū)分勵磁涌流與故障電流,并與傳統(tǒng)方法比較,克服了傳統(tǒng)方法的不足,具有很大的優(yōu)勢,有效地防止差動保護誤動,具有應用前景。另一方面,針對變壓器后備保護中過電流保護靈敏度不足以及各側(cè)保護配合復雜等問題,提出以故障正序分量相位差為判據(jù)的變壓器后備保護。利用數(shù)字化保護對線路信息采集量的冗余,提取故障分量,將變壓器各側(cè)線路與該側(cè)各出線線路上的電流故障分量的正序分量進行相位的分析比較。通過所搭建的變壓器模型的仿真驗證,說明運用該方法能夠正確地判斷故障所在位置,解決變壓器后備保護配合復雜,靈敏度低等問題,保證后備保護能夠在故障出現(xiàn)且主保護拒動時,及時正確切除故障,保證變壓器安全穩(wěn)定運行。
[Abstract]:With the rapid progress of social science and technology and the continuous development of human civilization, the electric power industry has entered a new stage characterized by ultra-high voltage and high intelligence.Safety and other aspects of the requirements are higher and higher.As an indispensable and irreplaceable important electrical equipment for power system, large power transformer will bring serious harm to the whole system if it can not be dealt with quickly and correctly after failure.So the relay protection of power transformer is very important.In this paper, the differential protection and backup protection of power transformer are studied.First of all, the principle of power transformer differential protection and various backup protection principles are studied in depth.The simulation model of double-winding transformer system with double-side power supply and three-winding transformer system with multi-output line are built on SIMULINK platform.By analyzing the simulation results, it is verified that the two models can correctly simulate the excitation inrush current caused by the no-load switch of transformer and the various electrical faults occurring inside and outside the main protection area of the transformer, which provides a simulation platform for the research.In view of the limitation of traditional differential protection inrush current braking method, on the basis of deeply studying wavelet transform, this paper chooses to use db4 wavelet function to decompose excitation inrush current and fault current by wavelet decomposition.The characteristics of wavelet transform of excitation inrush current and fault current under various conditions are observed and analyzed.A new method of inrush current identification based on wavelet coefficient distribution is proposed by analyzing the variation of the coefficients of the two layers.By extracting the wavelet coefficients from the two scales obtained by wavelet transform, the variance of the coefficients is calculated, and reasonable criteria are set to distinguish the inrush current from the fault current.The simulation results show that this method can distinguish inrush current from fault current quickly and accurately, and compared with the traditional method, it overcomes the shortcomings of the traditional method, has great advantages, and effectively prevents the maloperation of differential protection.It has the prospect of application.On the other hand, in view of the insufficient sensitivity of over-current protection and the complex coordination of side protection in transformer backup protection, a transformer backup protection based on the phase difference of positive sequence component of fault is proposed.In this paper, the redundancy of line information collection is used to extract the fault component, and the phase analysis and comparison of the positive sequence component of the current fault component on each side of the transformer line and the output line of the transformer are carried out.Through the simulation and verification of the transformer model, it is proved that the method can correctly judge the location of the fault and solve the problems of complex coordination and low sensitivity of the transformer backup protection.When the fault occurs and the main protection fails, the backup protection can remove the fault correctly in time and ensure the safe and stable operation of the transformer.
【學位授予單位】：青島科技大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TM41

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