Study of wavelet-based ultra high speed directional transmission line protection

A novel wavelet-based directional protection scheme is presented in this paper. Using the theory of wavelet singularity detection as a powerful signal-processing tool, the initial arrival of the traveling wave and its sign can be identified reliably. Characteristics of the proposed directional protection algorithm are analyzed and results of simulation studies are given. The wavelet-based directional protection scheme solves several problems existing in current protective relays and is suitable for use as an ultra high speed UHV/EHV transmission line protective relay.     

Modeling of a transmission network protection system using Petri nets

This paper proposes the modeling of a transmission network protection system using Petri nets (PNs). The protective system PN models include three parts: the colored bus-subnet model, the line protective relaying scheme model, and the communication link model. An example is given describing how the models work and the relationship among the models. Further application of the models is discussed and future work is presented.     

Ultra-high-speed directional protection of transmission lines using mathematical morphology

This paper presents a novel ultra-high-speed directional protection scheme developed using mathematical morphology (MM). The MM technique proposed is used to extract transient features from fault-generated voltage and current wave signals propagating along transmission lines during a post-fault period. Fault direction is determined by two composite relaying signals which are composed of the extracted transient features. A variety of fault scenarios has been simulated to evaluate the validity of the proposed scheme.     

高速网络数据流分类系统

针对高速网络数据分类系统遇到的性能瓶颈,本文提出了一种软硬件协同的设计思路。设计中,硬件上采用了64位PCI的高速硬件平台;软件上采用了零拷贝、循环缓冲和数据接收/传输块DMA技术。经过实际测试,系统能稳定地工作在千兆以太网的网络环境。     

超（特）高压输电线路高速行波差动保护

提出了一种行波电流差动保护的新算法,首先利用形态学交替混合滤波器去除行波信号中的噪声,并提取方向电流行波波头对应的时间,然后计算从方向电流行波起始时间开始数十微秒内方向电流行波波形的积分值,将输电线路两端的同向电流行波积分值的差值作为行波电流差动保护的动作依据。当被保护线路外部短路故障时上述差值很小,而被保护线路内部短路故障时该差值很大,从而明显地区分出内部和外部故障。该算法由于只利用了行波起始部分数十微秒内的信号,其动作时间主要决定于线路两端的通信时间,因此一般动作时间只有几毫秒。分析和仿真表明该算法动作速度快、可靠性高,可以作为超(特)高压输电线路的主保护。     

辐射型主动配电网的自适应方向保护方案

为了适应辐射型主动配电网对保护的要求,提出了一种基于方向闭锁原理的自适应保护方案。根据配电网的树状结构特征定义了参考方向整定规则,并配合闭锁方向规则,实现保护原理对于线路和母线等故障元件的自适应性。在配电网重构后,通过拓扑分析完成参考方向的自动配置,实现对于动态重构的适应性。针对主动配电网中包含较多可再生能源的特征,以及孤岛运行模式的需求,采用全阻抗继电器作为启动元件以提高保护的灵敏性。针对主动配电网中易于出现的弱电源问题,利用联跳提高弱馈侧保护的动作可靠性。以实际配电网作为算例验证了方案的有效性。所提保护方案能够为主动配电网提供一种简单、经济和可靠的主保护方案。     

超高速直流输电线路保护方向元件

为提高直流输电线路单端暂态量保护的可靠性与灵敏度,提出了一种基于故障行波能量的超高速直流输电线路故障方向元件,该元件基于不同故障方向时故障前行波与反行波能量之间大小的差异有效判别故障方向。利用由RTDS与现场控制保护装置的闭环测试系统,对该方向元件性能进行了测试。测试结果表明,该方向元件适用于不同电压等级输电工程,在直流输电工程不同运行方式下,均可以超高速正确判别故障方向,且不受故障位置、过渡电阻的影响,可以有效提高单端暂态量保护性能,并可构成纵联方向保护。     

High impedance fault protection in transmission lines using a WPT-based algorithm

This paper proposes a new algorithm for High Impedance Fault (HIF) protection, in high voltage transmission lines, with the aid of Wavelet Packet Transform (WPT). The new scheme uses the HIF-induced distortion of voltage and current waveforms to detect HIF and discrimination of the fault location, respectively. The algorithm is based on a recursive method, which adds up the absolute values of high frequency signal coefficients, generated over one last cycle. Application of the proposed algorithm to the pilot protection schemes is also discussed. The proposed method is evaluated by Electro Magnetic Transients Program (EMTP) simulation studies. Several simulations, which are performed using an appropriate HIF model, bring about results which assess the proposed technique accuracy in identifying HIF in overhead transmission lines. A comprehensive simulation study shows the efficiency of the proposed protection scheme from the viewpoints of dependability and security.     

A hybrid algorithm for high speed transmission line protection

A common method used in UHV transmission line protection is based on impedance measurement technique. The fault detection speed of impedance protection schemes cannot be improved without sacrificing the relay reach limit. Protection algorithms based on fault generated transient signals have shown promising results in improving the speed, but these methods have inherent reliability problems. This paper examines how the fault generated transient information can be used to achieve fast fault detection speeds in a distance protection scheme while maintaining a high reliability level.     

用于特高压输电线保护的能量方向元件

传统能量方向元件在特高压线路中不能正确判别故障方向,同时当线路出口发生故障时由于系统内阻很小而导致有功能量方向元件也不能做出正确的判断。提出了一种应用于特高压长距离输电线路的故障分量式能量方向元件,并且提出了相应的方向纵联保护原理,用贝瑞隆算法加以实现;从而使保护的可靠性大大提高;分析了保护判据及其动作特性。通过数字仿真证明了所提方向元件原理和保护判据的正确性和可靠性,该元件具有不受系统暂态过程、过渡电阻、串补电容等因素影响的特性,而且其灵敏度不受故障类型及故障位置等因素的影响,同时动作速度也较快,不大于20ms。     

用于含分布式电源配网保护的无电压方向元件研究

针对含有分布式电源的配网电流保护需要安装方向元件以确保动作的正确性,提出了一种只利用电流信息判断故障方向的方法.分析含有分布式电源的配网发生短路故障时的电流特征,得出无故障支路的电流故障分量模值较小,故障支路的电流故障分量模值最大,由此可以判断出故障的方向.运用PSS/E软件,对IEEE34节点系统对各种故障进行仿真,仿真分析表明,此方法能有效判断出故障的方向,且不受故障类型和故障位置的影响.     

用于含分布式电源配网保护的无电压方向元件研究

针对含有分布式电源的配网电流保护需要安装方向元件以确保动作的正确性,提出了一种只利用电流信息判断故障方向的方法.分析含有分布式电源的配网发生短路故障时的电流特征,得出无故障支路的电流故障分量模值较小,故障支路的电流故障分量模值最大,由此可以判断出故障的方向.运用PSS/E软件,对IEEE34节点系统对各种故障进行仿真,...     

Wavelet based transformer protection using high frequency power directional signals

This paper proposes a novel wavelet transform based relaying scheme for power transformer protection. The relay logic consists of two parts: disturbance detection based on first level high frequency details of the voltage signals only and fault discrimination using a power based directional signal derived from the first level high frequency details of both voltage and current signals. The logic is deterministic, computationally efficient, fast, secure and highly reliable. The operating time is 6 ms, about 1/3rd of power frequency cycle (20 ms). The scheme uses only the sign of the directional signals, rather than the difference in their magnitudes, hence it can work reliably in the presence of transformer tap variation, fault resistance and CT saturation. The validity of the proposed logic was exhaustively tested by simulating various types of internal and external faults, energization conditions and load variations on a 132 kV system modeled in ATP/EMTP with a 31.5 MVA, 132/33 kV, Y–Δ transformer. The proposed logic was able to correctly discriminate between internal faults, external faults and non-fault disturbances for all the 880 test cases.     

基于时频特性相似度的新能源场站T接型送出线路高速保护

新能源短路电流呈现幅值受限的非工频特征,导致差动保护的动作性能下降。在分析新能源电源与传统同步发电机故障特性的基础上,提出基于时频特性相似度的新能源场站T接型送出线路高速保护原理。该方法首先利用压缩感知压缩高频率采样信号,传输低频率压缩信号,降低保护通信量。然后利用小波变换提取故障电流的时频特征,利用主成分分析法(principal component analysis, PCA)剔除时频特征的冗余信息,得到时频特征矩阵。最后利用堪培拉距离衡量时频特征矩阵相似度,提出基于时频特性相似度的高速保护原理。所提保护理论上可以在故障5 ms内可靠识别区内外故障,具有较强的耐受故障电阻和系统噪声的能力,并且适用于新能源弱出力的场景。硬件在环实验结果和现场录波数据验证了所提保护的有效性。     

面向新型电力系统的输电网与分布式变速抽水蓄能联合规划

针对高比例新能源场景下分布式变速抽水蓄能的容量配置及其在电网中的位置接入问题,提出了输电网和分布式变速抽水蓄能的联合规划方案。首先,考虑了各类抽水蓄能的运行和库容约束、火电机组的出力和爬坡约束以及输电网的传输能力,以分布式新能源的经济消纳为优化目标,建立了分布式变速抽水蓄能和输电网间的联合规划模型。然后,通过凸松弛方法将该模型转化为混合整数线性规划模型,以两阶段优化方法求解得到了分布式变速抽水蓄能与输电网的联合规划方案。最后,采用两个标准测试系统对比验证了所提含分布式变速抽水蓄能的联合规划相较于定速抽水蓄能的规划方案,能更好地与其他灵活性资源相协调以消纳风光可再生能源,总体上可降低约20%的成本。     

基于极化电流行波方向继电器的行波方向比较式纵联保护技术及其在750kV线路上的应用

基于极化电流行波方向继电器的行波方向比较式纵联保护技术利用电流行波高频分量和电压行波低频分量的极性关系构成方向继电器,避免了电容式电压互感器(CVT)不能有效传变电压行波高频分量的问题。介绍了基于极化电流行波方向继电器的纵联保护技术及相应的保护装置在现场的应用情况。利用现场的故障录波数据,分析了电容式电压互感器和电流互感器对于电压、电流行波信号传变特性的影响,结果验证了该保护原理的正确性和保护装置的可靠性。     

ANN based directional relaying scheme for protection of Korba-Bhilai transmission line of Chhattisgarh state

As it is crucial to protect the transmission line from inevitable faults consequences, intelligent scheme must be employed for immediate fault detection and classification. The application of Artificial Neural Network (ANN) to detect the fault, identify it’s section, and classify the fault on transmission lines with improved zone reach setting is presented in this article. The fundamental voltage and current magnitudes obtained through Discrete Fourier Transform (DFT) are specified as the inputs to the ANN. The relay is placed at section-2 which is the prime section to be protected. The ANN was trained and tested using diverse fault datasets; obtained from the simulation of different fault scenarios like different types of fault at varying fault inception angles, fault locations and fault resistances in a 400 kV, 216 km power transmission network of CSEB between Korba-Bhilai of Chhattisgarh state using MATLAB. The simulation outcomes illustrated that the entire shunt faults including forward and reverse fault, it s section and phase can be accurately identified within a half cycle time. The advantage of this scheme is to provide a major protection up to 99.5% of total line length using single end data and furthermore backup protection to the forward and reverse line sections. This routine protection system is properly discriminatory, rapid, robust, enormously reliable and incredibly responsive to isolate targeted fault.     

模块化多电平换流器型高压直流输电系统控制保护体系框架

在介绍了MMC-HVDC系统拓扑结构的基础上,阐述了MMC-HVDC控制保护系统的设计原则和主要功能,指出采用冗余配置和分层设计的必要性.控制保护系统是MMC-HVDC系统的核心之一,在搭建了MMC-HVDC控制保护系统总体结构的基础上,提出建立4层结构的MMC-HVDC控制保护体系框架,即直流系统控制层、极控制保护层、阀组控制层、子模块控制保护单元,并进一步阐述了各控制层的控制功能及各层相互关系.     

Positional protection of transmission systems using GlobalPositioning System

This paper presents a new technique for the protection of power transmission systems by using the Global Positioning System (GPS) and fault generated transients. In the scheme, the relay contains a fault transient detection system together with a communication unit, which is connected to the power line through the high voltage coupling capacitors of the CVT. Relays are installed at each busbar in a transmission network. These detect the fault generated high frequency voltage transient signals and record the time instant corresponding to when the initial travelling wave generated by the fault arrives at that busbar. The communication unit is used to transmit and receive coded digital signals of the local information to and from the associated relay(s) in the system. At each substation, the relays determine the location of the fault by comparing the GPS time stamps measured locally with those received from the adjacent substations. Extensive simulation studies presented in the paper demonstrate the feasibility of the scheme     

表面肌电信号的高速数据采集系统的设计

表面肌电信号不仅非常微弱,常常淹没在大量的噪声中,而且极易受到干扰,因此前置放大电路的共模抑制能力成为能否有效拾取SEMG的关键。针对前置放大电路,本文提出了一种新的"浮地技术"。经实验证明,电路在低频的KCMR改善了30dB。此外,设计的基于CY68013与AD7862的USB2.0高速数据采集系统,工作在GPIF模式,有效地采集到了人体的表面肌电信号,为后续人体上肢动作模式辨识提供了信号源。