【作者】 张旭；

【导师】 杨奇逊； 徐振宇；

【作者基本信息】 华北电力大学(北京) ， 电力系统及其自动化， 2016， 博士

【摘要】 当今世界,化石能源的大量开发使用,带来资源紧张、环境污染、气候变化三大挑战。为此,推动能源革命、促进节能减排、应对气候变化对实现经济、社会、环境协调发展具有重大而深远的影响。构建全球能源互联网是优化全球资源配置,推动清洁能源利用的重要平台。现代高压电网作为全球能源互联网的重要组成,保障其安全、稳定运行,对保障国家能源安全,推动全球能源进步有着至关重要的意义。特高压、超高压输电是现代高压电网的关键技术。采用串联补偿或同塔多回有利于进一步提高特高压、超高压电网的输送能力,充分利用输电走廊,节省输电线路投资,对充分发挥特高压、超高压电网在能源互联网发展中的作用具有重要意义。为提高现代高压电网输电的安全性和稳定性,本文针对在串联补偿和同塔多回输电继电保护中存在的关键问题进行了分析。论文所做的研究工作主要包括以下几个方面：(1)提出了一种同塔四回分别完全换位线路容性潜供电流的补偿方法。首先对四回线路的对地电容、相间电容、线间电容各自的平均值通过变换矩阵转换为序分量；然后将补偿方案的电抗转化为序分量下的表达式,并将序分量下的电抗表达成与正序电容、相间电容、线间互容对应的形式；最后根据需要的补偿度,计算补偿电抗的大小。同时,对于检修状态下需要的中性点电抗也设计了优化方案。仿真验证表明,本补偿方案可以有效降低同塔四回线路单相接地故障和四回线路间同名相以及非同名相跨线复杂故障中的潜供电流和恢复电压。(2)提出了一种基于最佳等效零序互感补偿系数和单端单回线电气量的同塔四回线路距离保护新算法。首先,通过推导各回线路零序电流和零序阻抗的关系,得出用故障回路零序电流计算非故障回路零序电流的方法。然后,综合考虑保护侧系统各种运行方式下的距离保护I段等效零序互感补偿系数,选取距离保护I段需要的最佳等效零序互感补偿系数。从而实现了基于最佳等效零序互感补偿系数和单端单回线电气量计算同塔四回单相接地故障距离的方法。本算法还考虑了系统存在停运检修线路时等效零序互感补偿系数的修正方法。仿真验证表明本算法可以有效降低四回线路零序互感的影响,优于传统距离保护算法。(3)推导了一种适用于单回串联补偿线路的距离保护时域积分算法。根据故障电流的大小,串补电容可以归纳为三种工作状态：a)串补电容未被金属氧化物电阻(MOV)和放电间隙(GAP)旁路；b)串补电容被MOV旁路而GAP未导通；c)串补电容和MOV被GAP旁路。根据串补电容的状态特点与等值回路列写故障回路时域方程。时域方程中未知数为故障回路等效电阻、故障回路电感、串补电容和串补电容起始电压；已知参数为保护测量点电压和电流的瞬时值。时域方程在对时间进行积分后求解。传统的距离保护算法,如果假定了串补电容在故障期间的某种状态,而串补电容并未按照假定的状态动作,就会出现测距的不准确。新算法将串补电容设置成未知数,无论串补电容处于何种工作状态,都通过列写方程组求解,无需事先确定串补电容的工作状态。仿真验证表明,在单相接地故障和相间故障中,新算法在串补电容处于MOV/GAP未导通、MOV连续导通或GAP放电期间时,可以准确计算出故障距离。(4)推导了一种适用于平行双回串联补偿线路的距离保护时域积分算法。平行双回线路还需要考虑两回线路间零序互感的影响。因此,故障回路时域方程的未知数为故障回路等效电阻、故障回路电感、两回线路间零序互感、串补电容、串补电容起始电压,已知数为保护测量点电压和电流的瞬时值。故障回路时域方程对时间积分并求解。仿真验证表明,新算法在串补电容处于MOV/GAP未导通、MOV连续导通或GAP放电期间时,可以准确计算出故障距离,不受两回零序互感的影响。(5)提出了一种适用于特高压平行双回线路高阻故障的距离保护算法。本算法首先对故障相的电压、电流以及相邻一回线路的零序电流进行傅里叶变换,然后利用故障点故障电压和故障电流同相位的特点,通过列写关于正负序电流增量和故障点电压实部与虚部比值的方程,求解故障距离。特高压系统阻抗角角度很高,本算法在特高压线路中有较好的仿真效果。仿真验证表明,该算法耐过渡电阻能力高,不受两回线路互感和负荷的影响,而且也适用于平行双回线路的一回检修或者一端系统分裂运行的情况。综上所述,本文以现代高压电网的建设为背景,针对串联补偿和同塔多回输电继电保护中存在的五个关键问题进行深入研究,具有较高的工程应用价值和科研意义。更多还原

【Abstract】 The resources shortage, environmental pollution and climate change are the great challenges in the world wide, because of the overuse of a large number of fossil energy. Therefore, it is important to promote the energy revolution, the energy saving, and emission reduction to achieve the coordinated development of the economy, society and the environment. The Global Energy Interconnection is an important platform to optimize the allocation of global resources and promote the use of clean energy. The modern high voltage power grid is the important composition of the Global Energy Interconnection. To ensure the stable and safe operation is of the vital significance to ensure the national energy security and promote the progress of global energy. The Ultra High Voltage and the Extra High Voltage transmission are the key technology of the modern high voltage power grid. By using of series compensation and multiple circuits on the same tower is conductive to further increase the transmission capacity of Ultra High Voltage and Extra High Voltage power grid and make full use of the transmission corridor and save investment. In this paper, the key problems existing in the relay protection of the series compensation and multiple circuits on the same tower are analyzed. The research work mainly includes the following aspects:(1) A compensation method to reduce the secondary arc current for separately and completely transposed four-circuit transmission lines on the same tower is proposed. Firstly, the average values of the line to ground capacitances, inter-phase capacitance, and zero sequence mutual capacitance are converted to sequence value through the transformation matrix. Secondly, the inductance compensation scheme is converted to the sequence component. The sequence component of the inductance can be converted to the same form as the positive capacitance, inter-phase capacitance and zero sequence mutual capacitance. Finally, the compensation reactance is calculated according to the requirement of the compensation degree. The neutral point reactance is also optimized about various maintenance conditions. The simulation results show that this compensation scheme can decrease the value of secondary arc current and recovery voltage in the single-phase to ground fault and the cross country fault with same or different phases in the four-circuit transmission lines.(2) A distance protection algorithm for single-phase to ground fault in the four-circuit transmission lines on the same tower based on optimal equivalent zero sequence mutual inductance compensation coefficient and single circuit electrical data in one end is proposed. Firstly, by using the relationship between the zero sequence current and zero sequence impedance, the health circuit zero sequence current can be calculated by the fault circuit zero sequence current. Secondly, the optimal compensation coefficient of zone-I distance protection is selected based on the calculated zero sequence mutual inductance compensation coefficient under different operation modes in the protection side. The optimization method of zero sequence mutual inductance compensation coefficient for maintenance state is also proposed. The simulation results show that the proposed algorithm is not affected by the zero sequence mutual inductance in the four-circuit transmission lines and it is superior to the traditional distance protection algorithm.(3) A distance protection time domain integral algorithm is proposed for a single-circuit series compensated line. According to the fault current, the series compensation capacitors have three types of operation condition. a) Metal Oxide Varistor (MOV) and air gap (GAP) do not bypass the series compensation capacitor. b) the MOV bypasses the series compensation capacitor and the GAP does not conduct. c) the GAP conducts and bypasses the MOV and series compensation capacitor. The time domain equation of fault circuit based on the condition of series compensation capacitor and the equivalent circuit is utilized in this algorithm. The unknown parameters of the equation include fault circuit equivalent resistance, fault circuit inductance, series compensation capacitor and initial voltage of the series compensation capacitor. The known parameters include instantaneous voltage and current measured by the relay protection. In the traditional distance protection algorithm, if the state of the series compensation capacitor is assumed during the fault, while series compensation capacitor is different from the assumption of state action, the relay protection maybe mal-operation. In the proposed algorithm, the series compensation capacitor is set as an unknown parameter to solve the equation without the necessary to determine the state of the series compensated capacitor in advance. Simulation shows that in the single-phase to ground fault and phase-to-phase fault, the proposed algorithm can accurately calculate the fault distance in these cases: the MOV/GAP conduct; MOV conducts; GAP conducts.(4) A distance protection integral algorithm for double-circuit series compensated lines is proposed. Due to the influence of zero sequence mutual inductance existing in the parallel double-circuit transmission lines, the unknown parameters of the time domain equations for the fault circuit include fault circuit equivalent resistance, fault circuit inductance, zero sequence mutual inductance, series compensation capacitor and initial voltage of the series compensation capacitor. The known parameters are instantaneous values of voltage and current measured by the relay protection. The time domain equation for the fault circuit is solved after the integration of time. Simulation shows that the proposed algorithm, which is not affected by the zero sequence mutual inductance, can accurately calculate the fault distance in these cases:the MOV/GAP conduct; MOV conducts; GAP conducts.(5) A distance protection algorithm is proposed for Ultra High Voltage double-circuit transmission lines with high fault resistance. Firstly, the Fourier transform is used for the fault phase voltage and current and adjacent circuit zero sequence current. Secondly, with the principle that the voltage and current at the fault point have the same phase the fault distance can be calculated through the equation about the ratio of the real and imaginary part of the increment of positive and negative sequence current and the voltage at fault point. The angle of Ultra High Voltage system impedance is very high. The simulation results of the algorithm are very well in Ultra High Voltage transmission lines. The simulation shows that the proposed algorithm is better than the traditional algorithm with high resistance fault. It is not affected by the zero sequence mutual inductance and load current. The algorithm also presents good performance when one of the two circuits is in maintenance state or two lines are in split operation.This paper is mainly to solve the five key problems existing in the construction of the modern high voltage power grid. Therefore, this paper has high engineering application value and research significance更多还原