【作者】 王清亮；

【导师】 侯媛彬；

【作者基本信息】 西安科技大学 ， 安全技术及工程， 2010， 博士

【摘要】 国内外中压配电网的中性点广泛采用经消弧线圈接地的补偿运行方式,我国在煤矿井下等含有爆炸性气体物质的生产企业中,其高压供电网也常采用补偿运行方式。此种运行方式在发生单相接地故障时,由于故障电流微弱,电弧不稳定等原因,形成了故障选线保护装置面临着消弧与选线正确性之间的技术矛盾,因此,对补偿接地电网的故障选线问题进行研究是进一步提高供配电安全性,尤其对丰富和加强“爆炸性气体环境电气安全理论”的基础研究,具有重要的理论价值和现实意义。与利用故障稳态信息相比,采用单相接地故障产生的暂态量信息去解决选线保护难题,具有可靠性大、灵敏性高的优点。目前的研究多侧重于采用相关数学分析工具对暂态量信息的提取和利用,而缺乏从故障机理和暂态特性的本质上进行系统研究,使得暂态量选线方法还存在故障模型不精确以及暂态特性受故障发生条件影响较大的缺陷,从而导致选线效果不够理想。针对现有暂态量选线方法存在基础性研究缺失的问题,论文建立了单相接地故障电磁暂态模型,利用高阶电路动态方程研究故障信号的暂态特性及故障本质。通过对故障模网图和暂态等值电路的研究,从根本上揭示了补偿接地电网发生单相接地的故障机理和具有普遍意义的暂态特性规律,建立了故障时刻、接地点过渡电阻以及线路长度等故障条件与故障零模电流之间的函数关系,解决了接地故障模型不精确,对故障量理解运用片面性的难题。针对单相接地故障边界条件的复杂性和不确定性以及故障条件间的强耦合关系,论文定义了三个普适特征量:频带能比因子、阻抗因子和能谱熵。利用暂态普适特征量对故障信息进行数据挖掘,定量度量故障暂态的不确定性和复杂度;分析了故障暂态信号频谱分布的特性规律,定义能谱熵测度及饱和熵来统计信号能量的复杂程度;提出基于多尺度能谱熵测度的故障模式分类方法,将单相接地故障的模式分为强故障、小角故障和弱故障三类。针对暂态量选线保护方法受故障条件影响较大的问题,提出了基于故障模式识别的自适应选线保护方法。给出了主频带定义,利用故障后暂态零模电流的能量分布自动确定线路的主频带,减少了暂态容性电流频率分布不确定性对选线的影响。分别提出了多频带波形相关性的强故障选线方法、基于衰减直流分量能量的小角故障选线方法和基于能谱熵原理的弱故障选线方法。依据故障模式自动选择不同判据的研究思路,充分利用了故障暂态信号中的各种低频、工频和高频信息,可实现无死区的故障选线保护。针对绝大多数单相接地故障伴随有电弧,而电弧具有高度非线性时变特性和建模困难的问题,分析了电弧的故障机理以及在时域、频域的外在特性,借助非线性电路理论中的器件造型方法建立了电弧故障的黑箱模型;采用福特斯库相模变换技术,研究了配电网中各次谐波的性质;通过对补偿接地电网间歇性电弧、谐波源及消弧线圈不同补偿度的分析与仿真,验证了基于故障模式识别的暂态量选线保护方法可以适用于补偿接地电网的各种故障情况,具有良好的可靠性能。分别利用电磁暂态仿真软件EMTP的仿真数据、1:1的10kV高压物理模拟系统的试验数据以及现场故障录波数据三种方式验证了论文所提方法的正确性和可靠性。更多还原

【Abstract】 In order to ensure power supply reliability and security, many countries including china adopt the compensated neutral point of arc-suppression coil in medium voltage distribution network especially in enterprise high voltage power network with flammable and explosive environments, called compensated earthed network. The technology contradiction between arc-suppression and fault-line detection has become a difficult problem due to weak fault current, unstable fault arc and complex boundary conditions in this mode. So, the protection of fault-line detection hasn’t been settled satisfactorily and become one of key for long time in compensated earthed network. Thus, it is necessary to investigate the basic theory and key techniques for enhancing integrated electrical safety in the environment of explosive gas.The protection method of fault line detection using transient signals produced has better sensitivity and reliability than that using steady fault signals. Considerable work has been done to study how to use transient signals to detect fault-line. However, these studies mainlytake a rather simplified fault model and emphasize the advanced mathematical tools, which result in the lacking of depth analysis to the fault mechanism and transient characteristics.In view of the fundamental study lack in fault line detection by transient information, the electromagnetic-transient model is set up for single-phase-to-ground fault, and then the transient characteristics and fault essence are analyzed using the high-order circuit dynamic equations. The fault mechanism and universal regulars are fundamentally revealed with the phase-mold transformation technology and fault component principle. The functions on transient characteristics and fault conditions (fault time, transition resistance, line parameters and length) are analyzed to improve fault model accuracy.For the problem of the complexity existing in boundary condition uncertainty and strong-coupling fault conditions for single-phase-to-ground fault, three universal applicable parameters, including energy ratio factor, impedance factor and energy entropy, are defined. The degree of uncertainty and complexity of fault transient are quantitatively measured by means of mining abundant fault data with defined parameters. The spectrum energy distributions are analyzed and described according to energy entropy measure and saturation entropy. The results indicate that there are some laws based on multi-scale energy statistic, and they can be used to cluster fault model. At last, the single-phase-to-ground fault is divided three classes: strong fault, small angle fault and weak fault.Aiming at overcoming the influences of the fault conditions on fault-line detection based on the transient components, the paper presents a new adaptive method conforming to the different fault model. The characteristic band is defined and adaptively taken out for each line based on the spectrum energy distribution. And then, the adaptive faulty line detection method is proposed. When the strong fault occurs, the multi-frequency bands correlation analysis is adopted to detect fault-line; when the small angle fault occurs, the low-frequency band energy comparison is selected to detect fault-line; when the weak fault occurs, the wavelet energy entropy principle is chosen to diagnosis fault-line. All information of the transient zero-model currents including low frequencies, fundamental frequencies and high frequencies are utilizedin proposed method and the reliability can be effectively guaranteed for protection of fault-line detection in compensated earthed network.The short-circuit arc in medium voltage distribution caused by single-phase-to--ground fault burn in free air, called as air arc at low current in long gap with complex characters. The nature of this type of arc characters is difficult and extremely nonlinear. In the paper the form mechanism and the process of the arc waveforms are explored with the arc theory and the physical doctrine. Dynamic volt-ampere characteristic of arc in time-frequency are explained according to the energy balance principle. The black-box model for arc is further constructed according to the device-molding method of nonlinear circuit theory. Electromagneticsimulation and theory analysis have proved the proposed protection algorithm is not influenced by unstable arc, harmonic component and compensated degree.Vast simulations are carried out by the EMTP software. The security and reliability of the proposed method of detection fault line can be further proved by the test results from 10kV high voltage physical experimental system and the field measured waveforms.更多还原