差动保护运行动作特性的相量分析

差动保护的穿越制动特性依赖于制动电流的选取,每种制动方式有其自身的制动特性.不同方式之间如何比较,是需要有一种公用的方法,在同等条件下进行分析才行.提出用"运行动作特性"分析方法,直接以两侧电流的相量关系来表述动作特性,这样各种制动方式就可以有共同的基础.     

差动保护运行动作特性的相量分析

差动保护的穿越制动特性依赖于制动电流的选取 ,每种制动方式有其自身的制动特性。不同方式之间如何比较 ,是需要有一种公用的方法 ,在同等条件下进行分析才行。提出用“运行动作特性”分析方法 ,直接以两侧电流的相量关系来表述动作特性 ,这样各种制动方式就可以有共同的基础。     

相量分析方法在差动保护调试中的运用

差动保护是变压器的主要保护,差动保护在变压器投运后,需带负荷校验极性并保证接线正确。通过带负荷时作出各侧电流的相量图,具体分析差动接线不正确的原因,并提出相应的解决办法。     

A novel short-window algorithm of phasor computation for EHV line protection

A novel phasor computation algorithm is presented in this paper. The real and imaginary part filters of this algorithm have identical magnitude frequency characteristic (IMFC) at all the frequencies and orthogonal phase frequency characteristic (PFC) at fundamental frequency. Considering the conditions of the same magnitude frequency characteristic (MFC) and the orthogonal PFC, the two-sample algorithm is derived. Once two-sample orthogonal filters with IMFC are obtained, the algorithm design is just to select proper shapes and lengths of windows, which determine the filtering performance and response-time, respectively. This method could be applied to design filter in any window-length, especially in short-window. Therefore, this class of phasor algorithms is suitable for EHV transmission line protection where a short-window is crucial for fast response and better operation performance. The proposed algorithm has been applied to a series of EHV relay devices by China Xuchang Relay Group.     

Transmission system wide-area back-up protection using current phasor measurements

Zone-3 of distance relays might maloperate during stresses frequently encountered in power systems, such as power swing, load encroachment, and voltage instability. This paper proposes a new protection algorithm for discrimination between short-circuit faults and other stresses in the transmission networks. The proposed method compares the sum of currents at the predetermined buses before and after the disturbance occurrence using synchronized current phasor measurements. The faulted area and line are identified as well. The optimal placement of phasor measurement units (PMUs) is tackled using a mathematical model. One of the main advantages of the proposed algorithm is decreasing the number of required PMUs in comparison with those of existing wide-area back-up protection schemes. In virtue of its computational speed, the proposed method can be exploited as a practical back-up protection cooperating with conventional protection schemes. The extensive simulation studies carried out on the IEEE 57-bus test system verify applicability of the proposed algorithm as a reliable back-up protection scheme for lines.     

New family of digital filters for phasor computation [power systemrelay protection]

A new family of digital filters is presented in this paper. They have been specially designed with the aim of reducing the leakage of the conventional Fourier filter. That reduction is achieved by changing its rectangular window by a new family of windows with smaller sidelobes. Considered as frequency responses of lowpass filters, the window spectra are translated to the fundamental frequency to form the bandpass filters. For durations greater than two cycles, the phasor estimates obtained with the new filters improve those of the conventional filter on a wide frequency band. Therefore, they are recommended for fault location and phasor measurement. However, its direct use on the protection function is discarded, because their duration needs to be of at least two cycles. To convince readers that this is a new useful technique, a theoretical explanation of the improved performance is also provided. Additionally, simulation results confirm the new filters improve the accuracy of the conventional algorithm by a factor of ten, and further improvement of the same order can be achieved by elongating the window     

一种适用于同步相量测量的新算法

在异步采样的情况下,离散傅里叶变换(DFT)由于频谱泄漏及栅栏效应,计算结果不够精确,不能满足同步相量测量精度的要求.对现有的同步采样及误差消除方法进行了分析,提出了一种新的相量测量算法.通过线性插值计算,得到采样序列两相邻过零点进行频率跟踪,由所测频率对采样序列进行同步修正得到满足同步采样的新序列,采用DFT进行相量估计.仿真结果表明:该算法具有高精度、计算量小等特点,能够满足同步相量测量对精度及实时性的要求.     

A new frequency tracking and phasor estimation algorithm forgenerator protection

Digital generator protection is a complex and difficult problem. Analog and solid state methods have been successfully applied to generator protection in the past and implementation of these functions in a digital device is a continuing trend. This paper explores a new method to implement frequency tracking and phasor estimation in a numerical relay. A new algorithm is presented which utilizes a variable window discrete Fourier transform (DFT) for frequency tracking. Use of the DFT to compute the phasor estimates at a frequency other than the assumed frequency is outlined first. Next, a new technique for tracking the frequency is outlined. The paper concludes with testing of the new algorithm     

一种适用于同步相量测量的新算法

在异步采样的情况下,离散傅里叶变换(DFT)由于频谱泄漏及栅栏效应,计算结果不够精确,不能满足同步相量测量精度的要求。对现有的同步采样及误差消除方法进行了分析,提出了一种新的相量测量算法。通过线性插值计算,得到采样序列两相邻过零点进行频率跟踪,由所测频率对采样序列进行同步修正得到满足同步采样的新序列,采用DFT进行相量估计。仿真结果表明:该算法具有高精度、计算量小等特点,能够满足同步相量测量对精度及实时性的要求。     

Accurate phasor measurement for transmission line protection in the presence of shunt capacitor banks

This paper proposes a phasor measurement algorithm for transmission systems compensated with shunt capacitor banks. Since the shunt capacitor banks tend to lower the resonant frequencies, the dominant component, which has the lowest resonant frequency, is insufficiently attenuated by a low-pass filter and has an adverse influence on the phasor measurement of the fundamental component in a fault current signal. This paper theoretically investigates the dominant frequency in the presence of shunt capacitor banks and presents a phasor measurement algorithm immune to the dominant component and DC-offset. The performance of the algorithm is evaluated for a-phase to ground (a–g) faults on a 154-kV transmission system compensated with shunt capacitor banks. The evaluation results indicate that the algorithm can measure the phasor reliably and satisfactorily, although the fault current signal is distorted with the dominant component and DC-offset. The paper concludes by describing the hardware implementation of the algorithm on a prototype unit based on a digital signal processor.     

差动保护的暂态可靠性

差动保护的暂态可靠性取决于电流互感器的精度和差动继电器的动作特性.文中分析了P类电流互感器的暂态误差,提出了加倍P类TA的准确极限系数以限制其暂态误差.另一方面通过提高比率制动系数,对差动电流进行波形鉴别和采取快速测量可使差动继电器能避开暂态不平衡电流,只要求TA能在故障后2ms内保持线性变换.所提出的快速测量方法不需要另外增加快速动作的故障检测元件捕捉故障起始的时刻.     

差动保护的暂态可靠性

差动保护的暂态可靠性取决于电流互感器的精度和差动继电器的动作特性。文中分析了P类电流互感器的暂态误差 ,提出了加倍P类TA的准确极限系数以限制其暂态误差。另一方面通过提高比率制动系数 ,对差动电流进行波形鉴别和采取快速测量可使差动继电器能避开暂态不平衡电流 ,只要求TA能在故障后 2ms内保持线性变换。所提出的快速测量方法不需要另外增加快速动作的故障检测元件捕捉故障起始的时刻。     

基于同步相量的多端电流差动保护

随着新能源的蓬勃发展,多端输电线路的应用场景逐渐增多,多端电流差动保护应用成为最佳选择.本文提出一种基于同步相量的多端电流差动保护方法,使多端输电线路的差动保护应用具备可行性.基于IEC 61850-90-5协议,通过网络报文方式传输可路由的电气量信息,实现纵联通信数据定义的标准化.在分析同步相量特性的基础上,提出一种不依赖通道收发时延一致性的差动保护同步方法,并进一步提出基于光纤和5G无线通信的通道拓展方式,在保证差动保护可靠性的前提下,有效提高多端电流差动保护对通道的适应性,提升多端输电线路系统的供电可靠性.     

Exponentially decaying DC offset removal for phasor measurement using second‐order differential

This letter proposes an exponentially decaying DC offset removal scheme for phasor measurement in power systems. Considering the features of the parameters of the transmission lines (i.e., the reactance X is much larger than the resistance R of a transmission line), the second‐order differential of a faulted current signal can be utilized to suppress the DC offset to a great degree. Then the full‐cycle Fourier algorithm (FFA) is employed to calculate the phasors of the periodic components correctly. Simulation studies demonstrate that the proposed scheme can remove the DC offset to a great degree, leading to higher accuracy and faster convergence in phasor calculation than FFA. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Voltage-stability protection and control using a wide-area network of phasor measurements

This paper presents a concept for local monitoring of the onset of voltage collapse, protective, and emergency control in the presence of voltage-sensitive loads. The onset of voltage collapse point is calculated based on the load characteristics and simulated voltage and current phasors measurements, which are provided by a network of phasor-measurement units. If the stability margin is small and the reactive-power reserves are nearly exhausted, then controls to steer the power system away from the critical point will be activated.     

SIEMENS 7UT51型数字式差动保护继电器中差动保护的整定计算

介绍SIEMENS 7UT51型数字式差动保护继电器中的差动保护部分的特性,详细分析该保护的整定计算原则,并将其应用在扬二厂的厂用电系统整定计算中.     

电力线路行波差动保护与电流差动保护的比较研究

线路电流差动保护的基础是线路的RL集中参数模型和电荷连续性。行波差动保护的基础是线路的分布参数模型和行波传输不变性。针对两类差动保护在电力线路上的应用进行了详细的理论和仿真对比研究。指出二者的根本区别在于行波差动保护考虑了线路的分布参数特性和空间传播特性,而电流差动保护把线路看成节点,完全忽略了分布参数特性和空间传播特性,差动电流是行波差动电流的退化形式。对于特高压长距离输电线路,行波差动保护相比于电流差动保护有明显的性能优势。对于高压和超高压输电线路,行波差动保护和电流差动保护性能无显著差别,电流差动保护可以胜任该类线路。     

SIEMENS 7UT51型数字式差动保护继电器中差动保护的整定计算

介绍SIEMENS 7UT5 1型数字式差动保护继电器中的差动保护部分的特性 ,详细分析该保护的整定计算原则 ,并将其应用在扬二厂的厂用电系统整定计算中     

神经网络差动保护技术

通过对BP神经网络输入充分数量的典型样本来判决差动保护的动作信号，并探索了神经网络在电力系统继电保护应用中存在的问题和可能的解决方法。     

电容器差压保护与零压保护解析

在电力系统现场实际工作中,电容器差压保护和零压保护很容易被混淆。从三个方面具体分析了电容器差压保护和零压保护的区别。讨论了其在一次接线、二次接线外观上以及在调试试验方法上的区别,指出了其在反措上应注意的问题。