A New Transient Impedance-Based Algorithm for Earth Fault Detection in Medium Voltage Networks

This paper presents a new earth-fault detection algorithm for unearthed （isolated） and compensated neutral medium voltage （MV） networks. The proposed algorithm is based on capacitance calculation from transient impedance and dominant transient frequency. The Discrete Fourier Transform （DFT） method is used to determine the dominant transient frequency. The values of voltage and current earth modes are calculated in the period of the dominant transient frequency, then the transient impedance can be determined, from which we can calculate the earth capacitance. The calculated capacitance gives an indication about if the feeder is faulted or not. The algorithm is less dependent on the fault resistance and the faulted feeder parameters; it mainly depends on the background network. The network is simulated by ATP/EMTP program. Several different fault conditions are covered in the simulation process, different fault inception angles, fault locations and fault resistances.

Single-phase earth fault current distribution between optical fiber composite overhead ground wire and ordinary ground wire in transmission system

It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method.Influences of some factors,such as single-phase earth fault location and ground resistance of poles,on short-circuit current distribution were discussed.Results show that:1) results of the loop method conform to those of double sided elimination method;2) the fault location hardly influences macro-distribution of short-circuit current.However,current near fault location is evidently influenced;and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.

A Novel Transient Current-Based Differential Algorithm for Earth Fault Detection in Medium Voltage Distribution Networks

This paper presents a novel transient current differential algorithm for earth fault detection in unearthed （isolated） and compensated neutral medium voltage （MV） networks. The proposed algorithm uses the transient residual currents, which are very sensitive for earth faults detection. The transient values of residual currents are calculated for each feeder in the network and used as an earth fault indicator. The flow of residual currents is investigated. It is found that the residual current for the faulted feeder is equal to the summation of all residual currents for all other healthy feedersl Based on this investigation, a differential technique is proposed. A percentage restrain performance is proposed to ensure the selectivity and security of the algorithm. The transient algorithm is very sensitive for earth fault incidence. To apply the proposed algorithm, the residual currents can be measured easily by one sensor for each feeder with no need to voltage measurement. The proposed algorithm is less dependent on the fault resistance and the faulted feeder parameters. The network is simulated by ATP/EMTP program. Different fault conditions are covered in the simulation process： different fault inception angles, fault locations and fault resistances.

Fault Feeder Identification in Non-effectively Grounded Distribution Network with Secondary Earth Fault

Secondary earth faults occur frequently in power distribution networks under harsh weather conditions.Owing to its characteristics,a secondary earth fault is typically hidden within the transient of the first fault.Therefore,most researchers tend to focus on a feeder with single fault while disregarding secondary faults.This paper presents a fault feeder identification method that considers secondary earth faults in a non-effectively grounded distribution network.First,the wavelet singular entropy method is used to detect a secondary fault event.This method can identify the moment at which a secondary fault occurs.The zero-sequence current data can be categorized into two fault stages.The first and second fault stages correspond to the first and secondary faults,respectively.Subsequently,a similarity matrix containing the time-frequency transient information of the zero-sequence current at the two fault stages is defined to identify the fault feeders.Finally,to confirm the effectiveness and reliability of the proposed method,we conduct simulation experiments and an adaptability analysis based on an electromagnetic transient program.

Method of Fault Area ＆ Section Location for Non-solidly Earthed Distribution System

中国中压配电网以架空线为主，多为小电流系统，单相接地故障占到电网故障总数的80％以上，但中国配网自动化系统基本上没有小电流接地故障定位功能，使配网自动化系统在提高可靠性的作用上大打折扣。给出一种小电流接地故障区段定位新方法，在线路上配置广域相量测量固定测点，获取小电流电网单相接地故障特征信息。基于测点相邻矩阵区段起始测点标识向量和故障路径标识向量概念，提出确定故障区间边界节点算法。物理模拟实验和挂网测试表明：该故障分区分段定位方法能够在线求解小电流接地故障段边界节点，缩小线路维护巡视范围。确定故障区间边界节点算法还可用于确定故障区相关负荷开关，为线路维护和馈线自动化提供依据。

Correlation Studies of Rare Earth Elements in Syntectonic Intrusions of Strike-Slip Stage along Southern Segment of Tan-Lu Fault Zone

Intrusions in the Zhangbaling uplift zone and the eastern margin of the Dabie orogenic belt belong to the syntectonic intrusions developed during the strike-slip stage in the southern segment of the Tan-Lu fault zone. However, characteristics of rare earth elements show that intrusions in the Zhangbaling uplift zone have the characteristics of mantle source type and those in the eastern margin of Dabie belt are the typical crust source type. Therefore, Au-deposits related to the intrusions in the Zhangbaling uplift zone are developed better than those in the eastern margin of the Dabieshan. The research results of the rare earth elements coincide with the studies of geophysics, tectonic setting and stable isotope. It is further indicated that the rare earth elements offer effective approach to tracing the material sources of magmatic rocks.

Transient Fault Locating Method Based on Line Voltage and Zero-mode Current in Non-solidly Earthed Network

为解决配电网小电流接地故障时故障点定位困难的问题，提出一种基于线电压和零模电流暂态分量的故障定位新方法。该方法借助馈线自动化（feeder automation，FA）系统实现，不需要额外增加设备。馈线终端检测线电压和零模电流信号，利用暂态线电压的希尔伯特变换与暂态零模电流的乘积计算故障方向参数，FA主站根据故障点前后方向参数极性相反的特征确定故障点所在的线路区段。介绍基于线电压的小电流接地故障检测和接地故障相确定的算法。数字仿真与试验结果表明该方法是正确可行的。

An evidence for earthquake ocurence time related with geologic structure──Relations between local mean lunar times of earthquake ocurence and their fault trends

The relation between the local mean lunar time τ of earthquake occurrence and their fault trends is studied in this paper. The local mean lunar times τ of 53 earthquakes in 24 groups are calculated. Because the tidal generation force arisen by the moon is a cyclic function of about 12 hours 25 minutes in the main, the two tidal generation forces anywhere in the earth arising by the moon are equal in general when the moon lies to the two sites of 180° interval of local mean lunar time. Based on this phenomenon the values Δ τ of τ 1- τ 2 or τ 1-τ 2±180° of two earthquakes occurring repetitiously in the same place are also calculated. The calculated results show that if the fault trends of the two earthquakes in the same place is near, the Δ τ is usually smaller and if the fault trends of the two ones is not near, the Δ τ is usually larger and the distribution of the local mean lunar time τ of earthquakes in different places is dispersive even if fault trends of these earthquakes are near, and the τ does not concentrate on the lower and upper transit of the moon. The above phenomena clear up that the triggering earthquake of earth solid tide arisen by the moon is relative with the fault trends of earthquakes and we ought to think over the difference of environmental conditions of earthquake preparation of each seismogenic zone and can not make statistics to earthquakes in different places when we study the relation between the solid earth tide arisen by the moon and earthquakes.

Google Earth在野外初步断裂调查中的应用

主要介绍了卫星影像技术及Google Earth的特点,通过工程实例说明了Google Earth作为卫星影像在野外断裂调查中发挥的作用,总结了Google Earth卫星影像的优劣。

基于Google Earth的浑河断裂带遥感影像解译分析

遥感解译分析是断裂调查和活动性研究的重要工作内容,通过清晰、完整的断裂线性影像判读并结合实际验证调查能够获得断裂构造展布、结构、规模和活动特征等多方面的参数。浑河断裂带发育于沈阳、抚顺及其以东的辽东山地,其Google Earth卫星数据分辨率可以达到1~2.5m至亚米级,客观上提供了进行浑河断裂带遥感解译分析的条件。分析表明,浑河断裂带可以划分为沈阳段、抚顺段、章党—南杂木段和南杂木—英额门东段等4个不同的断裂段,除沈阳段以外,其它各段均表现出清晰的断裂线性特征,对于微地貌形态具有比较明确的反映。抚顺段和南杂木—英额门东段均控制了浑河河谷的发育,但不同的是,抚顺段北支较之南支规模更大、活动性更强,章党—南杂木段和南杂木—英额门东段影像可辨识度较高,微地貌变化稳定、连续,可能具有较新的第四纪活动性。

Characteristics and factors that influenced damage to dams in the M_s 8.0 Wenchuan earthquake

Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study include： severely damaged dams were densely distributed along the seismologic fault; small dams, especially small earth-rock dams, had the most serious damage that was caused by a variety of factors; the most serious damage was caused by seismic waves; damage was aggregated by aftershocks; and the extent of the damage patterns increased with the seismic intensity. Damage patterns varied in different intensity zones and cracking was the most common type of damage. Most of the dams had a good base with relatively high bearing capacity, and the walls of the earth-rock dams were mostly of clay soil. This type of base and body material mitigated some of the damage to dams. Reservoir maintenance and other factors also have a significant impact on the seismic safety of the dam. Finally, some recommendations to reduce seismic damage to dams are proposed.

Process of source dynamics of the Jingtai earthquake (M=6. 2 )

In this paper, the process of source dynamics of the Jingtai earthquake (M= 6. 2) is studied on the basis of both earth resistivity changes before the event and the spatial directivity of single-observatory magnitude measurements of the seismic network of China. The following conclusions are obtained: the NW-SE directional tension stress (or the one about in the direction) inside the source region was enhanced during the short period from three to five months before the event, and done still further about in twenty odd days before the event, so that it finally leads the fault in about the EW strike to produce dislocation in NWW-SEE direction. Finally, this dislocation pattern caused the strong ground vibration to be received at the seismic observatories which were located in the NWW and SEE directions of the epicenter, while the weak vibration to be received at the ones in NE and south directions of the epicenter. At last, understandings on the imminent earthquake prediction through earth resistivity method are set forth.

Design and Testing of Three Earthing Systems for Micro-Grid Protection during the Islanding Mode

This paper presents and tests three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types when the MG transferred to the islanding mode. The main contribution of this work is including the models of all micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included with the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the islanding mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current pro-tection relays. With using TN earthing system, touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited values during islanding mode. For the two others earthing systems (TT and IT), fault currents are small and nearly equal to the over load currents which make over current protection relay can not differentiate between fault currents and overload currents. All models of micro sources, earthing systems, inverters and control schemes are built using Matlab?/Simulink? environment.

Comparison the Performances of Three Earthing Systems for Micro-Grid Protection during the Grid Connected Mode

This paper presents, tests and compares three earthing systems (TT, TN and IT) for Micro-Grid (MG) protection against various fault types during the connected mode. The main contribution of this work is including the models of all the micro sources which interfaced to the MG by power electronic inverters. Inverters in turns are provided with current limiters and this also included in the inverter models to exactly simulate the real situation in the MG during fault times. Results proved that the most suitable earthing system for MG protection during the connecting mode is the TN earthing system. That system leads to a suitable amount of fault current sufficient to activate over current protection relays. With using TN system, Touch voltages at the faulted bus and all other consumer’s buses are less than the safety limited value if current limiter is included with the transformer of the main grid which connects MG. For the two others earthing systems (TT and IT), fault current is small and nearly equal to the over load current which make over current protection relay can not differentiate between fault current and overload current. All models of micro sources, earthing systems, inverters, main grid and control schemes are built using Matlab?/Simulink? environment.

Research on Fault-feeder Selection Dvice

The compensation current of the arc-suppressing coil makes the phase and amplitude of zero-sequence measurement current of the earthed fault feeder to vary. It is very hard to detect the fault feeder by using existing detectors based on single method. In this paper, integrative feeder selection strategy—zero sequence current increment method and the direction of transient current— is put forward. Based on the integrative feeder selection strategy, the design of fault-feeder selection device for one-phase-to ground fault on resonance grounding system is presented. For the purpose of testing and validating the operating principle of the device, the experiment of single-phase-to-ground fault has been carried out on the simulation of 1.2 kV power network. The results from many repeat experiments show that stability of the fault selection device is satisfactory.

Google Earth在电力通信光缆管理中的应用

介绍利用GOOGLE提供的免费的全球卫星图像软件Google Earth来绘制地区电力光缆路径的方法,用此方法可以获得及时更新的路径资料,便于了解光缆地理环境,并实现光缆故障定位。

Line Faults in Gd_5Si_2Ge_2-Type Phase

Gd5Si2Ge2.2 alloy was synthesized by arcmelting and its phase components, microstructure, and especially the line features were investigated by X- ray diffraction （XRD）, scanning-electron microscope （SEM）, energy-dispersive spectroscopy （EDS）, and transmission-electron microscope （TEM）. Gd5Si2Ge2.2 consists of Gd5Si2Ge2-type and GdGe-type phases and presents eutectic characteristics. There are many regular line features on the Gd5Si2Ge2-type phase according to SEM. EDS shows that the line feature is not the Gd5 （Si,Ge）3-type phase because Gd content decreases at the line features. Two types of line features are found in the fine microstructure of Gd5Si2Ge2-type phase by TEM. Selected area diffraction （SAD） confirms that both line features are not the secondary phase or twins. There is no changes observed in the microstructure of Gd5Si2Ge2 2 from room temperature to 1400 ℃ with in situ high temperature optical microscope, therefore, it is deduced that the line features observed by SEM are formed during the solidification.

Stress-Deformed State of Geological Environment and Prognosis of Antropogenic-Tectonic Earthquakes

The highest priorities of any civilized country are in providing interests of social safety.The anthropogenic influence on geological environment is becoming greater because of the human activities increase. That’s why anthropogenic-tectonic earthquake problem has become important recently.It appeared as a hypothesis in the 30 s and became much clearer in 60 s.The anthropogenic-tectonic earthquake epiceneters are located not far from the surface and,as a rule。

郯庐断裂转换段新沂地裂缝成生机理及构造意义

新沂地区处于郯庐断裂带转换段的关键部位,自20世纪70年代以来在新沂地区共发现地裂缝灾害点28处。这些地裂缝以群发的形式发育在南马陵山以西、沂河—骆马湖以东的区域内,地裂灾害影响区面积达100 km^(2)。新沂地裂缝与地层结构、地震活动、地下水开采等因素有着千丝万缕的联系,对其研究形成了多种观点。利用实地调查与勘探手段,新近查明了新沂地裂缝的基本特征,它们具有走向一致性、纵向尖灭性、局部群发性等特点,且与邻近断裂(郯庐断裂带次级断裂F3)具有高度一致性,属于区域构造控制型地裂缝。以新沂地区地质构造为原型,构建了逆断层作用下地裂缝成生物理试验模型。试验结果表明,随着逆断层断距加大而依次呈剪裂段、离层段、弯裂段等发展过程。结合新沂地区“地堑地垒地堑”组合结构,新沂地裂缝的成因机制可概括为“跷跷板”构造模型,在构造应力、自重应力、地下水波动等作用下,下沉段受挤压,上升段因抬升而弯裂,从而形成地裂缝。研究新沂地区地裂缝,对揭示郯庐断裂带“北中南”段构造变化和“深浅表”部结构联系具有重要的指示意义。

牵引供电系统接地短路故障智能辨识方案

随着多种类型电力机车的投入运行,线路行车密度增大、机车功率提升,导致负荷与故障的电气量特征接近,给故障辨识带来极大的困难。传统接地短路故障辨识方案主要依靠人工提取电气量特征并进行建模,难以适应复杂且多变的牵引网运行工况。为此,基于深度学习理论,提出一种智能牵引供电系统接地短路故障辨识方法,实现对牵引网负荷与接地短路故障的准确识别。