【作者】 马静；

【导师】 王增平；

【作者基本信息】 华北电力大学（河北） ， 电力系统及其自动化， 2008， 博士

【摘要】 近年来,随着超高压大容量电力变压器不断投入运行,现场对变压器主保护的可靠性、快速性和灵敏性提出了更高的要求,完善变压器差动保护和提出新型主保护原理势在必行。论文主要针对目前变压器主保护中尚未很好解决的一些关键问题展开工作,提出了相应的解决措施。论文研究的主要内容和成果有:(1)首次提出了基于数学形态学提取暂态量的励磁涌流识别新方法,该方法分别从奇异点信息和能量谱特征的角度出发设计了两种方案。仿真和动模实验结果均表明:该方法能够正确区分变压器励磁涌流和内部故障电流,计算量小;不受对称性涌流和非周期分量的影响;在性能上明显优于二次谐波制动原理和波形比较原理。(2)首次提出了利用网格分形技术鉴别励磁涌流的新方法,该方法分别从时域和频域出发设计了两种方案:时域法动作速度快,而频域法灵敏度高,两者相结合,不仅能有效地区分励磁涌流和故障电流,而且在性能上超越了二次谐波制动原理和波形比较原理。此外,新原理还采用了标准化的方法,使其在定值的选取上更具有通用性。(3)首次提出了基于网格分形和自适应广义形态滤波技术识别TA饱和的新方法。该方法实现了在TA严重饱和情况下,对差动保护区内和区外故障的准确识别;解决了在“小时差”情况下,传统的“时差法”无法判别的难题。该方法特征明显,易于实现,动模实验数据验证了它的有效性和可行性。(4)首次提出了基于广义瞬时功率的新型变压器保护原理。利用正常情况下变压器的模型和回路方程,得到了仅含漏电感和绕组电阻的二端网络,从分析输入端口的广义瞬时功率出发,彻底摆脱了变压器铁损和铜损带来的不利影响,进一步揭示了变压器出现励磁涌流状态与发生内部故障状态在本质上的不同。该原理计算量小,不受Y/Δ接线方式的影响,无须知道变压器的漏感参数,仿真和动模实验结果证明了该原理的正确性和可行性。(5)提出了基于等效瞬时漏电感的新型变压器保护原理。在变压器回路方程的基础上,利用电压、电流的差分形式计算变压器等效瞬时漏电感,并通过各漏感之间的差异构成判据。该判据不受励磁涌流的影响,而且避开了变压器难以取得的内部参数,实施简单,物理意义明确,动模实验验证了该原理的正确性和有效性。更多还原

【Abstract】 Recently, with the EHV large capacity transformers putting into operation continuously, reliability, rapidity and sensibility are in highly demand. It is imperative to consummate transformer differential protection and bring forward novel transformer main protection. Based on deep analysis and research, novel principles and algorithms are provided to solve some key problems still existing in power transformer main protection. The major contributions of this dissertation are as follows.(1) A new algorithm to distinguish between the magnetizing inrush and internal faults is creatively put forward. Based on the characteristics of singularity and energy spectrum, two criteria are proposed. Simulation and dynamic testing results validate this algorithm is able to accurately discriminate between magnetizing inrush current and internal fault. Moreover, it needs a few calculations and has stability during both symmetrical inrush currents and DC components. Compared with the second harmonic restraint principle and the waveform comparison principle, the proposed algorithm has better performance.(2) A novel algorithm based on the grille fractal for the discrimination between inrush current and fault current is originally proposed. Meanwhile, two schemes to identify inrush current in the time and frequency domains are respectively developed in detail. The experimental results indicate that the scheme in the time domain is able to clear internal faults with faster operating speed and the scheme in the frequency domain is more sensible when an internal low level turn-turn fault occurs. Based on the combination of these two schemes, the proposed technique is reliable during discrimination between internal faults and magnetizing inrush currents. Compared with the second harmonic restraint scheme and the waveform comparison scheme, the proposed schemes have better performance. Besides, the normalization of the grille curve makes the threshold has little relation with the parameter of the transformer, which has more universal meaning in the determination of the threshold.(3) A novel approach using grille fractal and generalized morphological filter with self-adaptive method to avoid mal-operation of transformer differential protection is proposed. With this novel approach, the differential protection will operate accurately in the event of inner-zone fault under TA saturation. Unlike the traditional time difference (TD) detection criterion, this approach does not need to discern the TD between fault occurrence instant and differential current emergence instant. Dynamic testing results validate its simplicity, availability and feasibility.(4) A novel principle of transformer protection using generalized instantaneous power is presented. By eliminating the mutual flux leakage in the transformer loop equation, a two-terminal network only containing the winding resistance and the leakage inductance is generated. According to the average of the generalized instantaneous power flowing into the two-terminal network, magnetizing inrush and internal fault can be essentially distinguished. Furthermore, this technique is suitable for the Y/Δconnected transformers. Simulation and dynamic testing results verify this scheme is independent of leakage inductance, iron loss and copper loss.(5) A new principle focusing on the equivalent instantaneous leakage inductance (EILI) is presented. The EILI concept along with its calculation method and criterion to extract features of the inrush current and the internal fault is developed in detail. The proposed scheme, which is verified by the experimental results, is independent of core characteristics and transformer parameters. Besides, its easy implementation in real time is another advantage because of its simplicity.更多还原