本文選題：電力變壓器 + 鐵心　； 參考：《華北電力大學》2017年碩士論文

【摘要】：大型電力變壓器鐵心磁路內的剩磁問題是普遍存在的,隨著電力系統(tǒng)的大力發(fā)展,電力變壓器的容量越來越大,電壓等級越來越高,大型電力變壓器鐵心內的剩磁問題也越來越嚴重,尤其是發(fā)電站的升壓變壓器、用于直流輸電的換流變壓器、變電站的主變,其鐵心剩磁的問題表現(xiàn)的最為嚴重。剩磁問題具體表現(xiàn)為增大變壓器的空載有功損耗;增大變壓器鐵心的震動;增大變壓器噪音水平,形成噪音污染;當電力變壓器鐵心剩磁非常嚴重時,對變壓器的現(xiàn)場空載合閘試驗非常不利,造成變壓器空載合閘勵磁涌流過大,出現(xiàn)繼電器保護動作跳閘現(xiàn)象;跳閘產生的操作沖擊過電壓會高于變壓器的額定電壓,這可能造成變壓器的絕緣損傷;勵磁涌流過大會使得鐵心磁通高度飽和,鐵心出現(xiàn)局部過熱現(xiàn)象,對鐵心造成損傷;溫度過高會使絕緣老化加快,變壓器油裂解,從而影響變壓器的運行壽命,嚴重影響了電力系統(tǒng)的安全穩(wěn)定運行。因此判斷變壓器鐵心內是否有剩磁、如何消除鐵心剩磁已成為人們日益關注的重點問題。通過分析大型電力變壓器的工作原理、結構特點,發(fā)現(xiàn)大型變壓器均為油浸式,其鐵心磁路本身是封閉回路,并且鐵心和繞組完全被變壓器油箱密封屏蔽起來,因此采用常規(guī)的磁場測量方法不能實現(xiàn)對變壓器鐵心內的磁場測量。本文中采用的測量鐵心磁場的方法是利用繞組本身作為測量線圈,根據(jù)鐵心的勵磁曲線的特性(飽和磁通和剩余磁通等特性),通過測量變壓器繞組首尾兩端電壓,并對電壓曲線進行積分計算來準確測量出鐵心內的磁通變化量,準確計算出鐵心的最大飽和磁通量、飽和剩磁量和鐵心的初始剩余磁通量;并根據(jù)以上的鐵心磁通測量方法研究出新型退磁的方法:利用直流電源對鐵心施加與其剩余磁通量反方向的且等值的磁通量。通過對不同類型的電力變壓器進行退磁,驗證了利用此方法去除鐵心剩磁是十分有效的。
[Abstract]:The problem of remanence in the core magnetic circuit of large power transformer is widespread. With the development of power system, the capacity of power transformer becomes larger and larger, and the voltage grade becomes higher and higher. The problem of remanence in the core of large power transformer is more and more serious, especially in the booster transformer of power station, the converter transformer used for DC transmission, the main transformer of substation, the problem of core remanence is the most serious. The problem of remanent magnetism is to increase the no-load active power loss of the transformer; to increase the vibration of the transformer core; to increase the noise level of the transformer; to form noise pollution; when the remanence of the core of the power transformer is very serious, It is very unfavorable to the field no-load closing test of the transformer, which causes the inrush current of the transformer's no-load closing excitation to be too large, the phenomenon of relay protection action tripping occurs, and the operation impulse overvoltage produced by the tripping is higher than the rated voltage of the transformer. This may cause insulation damage to transformers; excessive excitation inrush current causes high saturation of magnetic flux in the core, local overheating of the iron core, and damage to the iron core; excessive temperature will speed up insulation aging and the transformer oil will break up. Therefore, the operation life of transformer is affected, and the safe and stable operation of power system is seriously affected. Therefore, how to determine whether there is remanence in the core of transformer and how to eliminate the remanence of the core has become an increasingly important issue that people pay more and more attention to. By analyzing the working principle and structural characteristics of large power transformers, it is found that the large transformers are oil-immersed, the core magnetic circuit itself is a closed loop, and the core and winding are completely sealed off by the oil tank of the transformer. Therefore, the conventional magnetic field measurement method can not be used to measure the magnetic field in the transformer core. In this paper, the method of measuring the core magnetic field is to use the winding itself as the measuring coil. According to the characteristics of the excitation curve of the core (saturation flux and remanent flux, etc.), the voltage between the two ends of the transformer winding is measured. The integral calculation of the voltage curve is carried out to accurately measure the flux variation in the core and calculate the maximum saturated magnetic flux, saturated remanent magnetic flux and initial residual flux of the core accurately. A new method of demagnetization is developed according to the above methods of core flux measurement: the DC power source is used to apply the equivalent magnetic flux in the opposite direction to the iron core in the direction of its remanent magnetic flux. Through demagnetization of different types of power transformers, it is proved that this method is very effective in removing core remanence.
【學位授予單位】：華北電力大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM41

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