在电力系统实际运行中,及时准确地判别出输电线路故障类型(瞬时性故障和永久性故障)对电力系统的安全可靠运行十分重要.现有非雷击故障诊断方法存在诸多弊端,因此文章提出一种基于线路两端故障录波数据并根据不同时间段数据间的广义相关系数诊断故障类型的方法,提出了故障特征谱的概念,根据故障特征谱中不同曲线的变化规律判断故障状态的发展过程.仿真和现场数据的分析可以看出,对于永久性故障,故障后数据与故障前数据的相关性较低;对于瞬时性故障,故障后的数据与故障前的数据相关性较高,而故障前数据与故障存在时的数据相关性较低,初步验证了文章所提出方法的准确性和有效性.

In this paper, the influence of transformer winding deformation on the equivalent electrical parameters is studied, and the proximity effect and skin effect caused by AC current in the wire are simulated. It is verified that the current distribution will be affected by the proximity effect and skin effect. This effect will lead to the change of the AC resistance of split conductor. An equivalent area method for the quantitative calculation of the high frequency resistance of windings is presented. It contributes to the analysis and diagnosis of transformer winding faults, especially the diagnosis of transformer winding deformation.

Line icing is a common secondary disaster that seriously affects operation safety and stability of HV overhead transmission lines.Therefore,the paper presents a icing detection method of HV overhead transmission lines.With signal source of voltage and current at both sides of transmission lines,data set of reference voltage and current that reflect charac-teristics of icing parameters are adaptively and dynamically generated.The generalized correlation coefficient of the detec-ted data and reference data set is adopted as judgment criteria to diagnose icing area and extent in accordance to what the co-efficient is.It is proved by lots of simulation analysis that the method is of accuracy and reliability.

In allusion to the problem of low recognition veracity of existing fault diagnosis method for power transmission lines,this paper proposes a kind of new method for fault diagnosis based on fault recording data at both ends of lines,which uses generalized related function as a tool to dig out correlation of recording data at different time periods before and after the fault,and distinguish fault type according to size and change law of generalized correlation factor. If the correlation fac-tor between pre-fault data and post-fault data is great,the fault is diagnosed as instantaneous fault while if the factor is small,the fault is diagnosed as permanent fault. Simulation analysis initially illustrates veracity and reliability of this meth-od. Example of diagnosis on wind dancing fault of Haiwan Ⅰ line further proves effectiveness of this method.

Voltage transformer (VT) in generator circuit is an important instrument for generator monitoring and controlling.Its insulation defect detection is closely associated with safe and reliable operation of generators.A novel detection method for insulation defects in generator circuit VT is proposed in this paper.Frequency characterization of lightning impulse reflection is provided using HV level output equipment.Correlation of VT insulation response to the same and different voltage amplitudes,resulting from lightning impulse,is analyzed.Discriminant function is adopted for insulation situation analysis and fault diagnosis from test data.With this method,better anti-jamming capability and stability of generator circuit VT is achieved.

In this paper a decoupling method is proposed according to the block of each phase winding. According to the relation, the current signals in each set of parameters can be corresponding to a single set of voltage signals. Simulation analysis of transformer model is carried out. The simulation results show that there is a difference between the voltage and current in different winding states. It has laid a foundation for the diagnosis of transformer winding deformation and other insulation defects.

As the terminal equipment in power system, power transformer is directly related to the safety and stability of power grid. The faults of transformer may bring great harms to the entire power grid and result in huge loss. The insulation defect of transformer winding is the main cause of the transformer fault. Therefore, the study of transformer winding insulation defect detection method has important engineering significance. This paper studies the wave process of transformer winding with Duhamel integral in this paper, and calculates the high frequency zero state response under the condition that the transformer winding has good insulation when the standard lightning wave invades the transformer. With the application of analytical continuation Fourier series, this paper also analyzes and calculates the measurable end current of transformer winding with insulation defects under the invasion of standard lightning wave. The above currents are compared and analyzed. The work of this paper is helpful to the fault diagnosis of transformer winding insulation defects.

This paper puts forward a method of calculating the high-frequency zero sequence impedance, and deduces the earth high frequency analytic calculation formula for the zero sequence impedance. In order to verify the validity of analytical formulas, this paper combined with a large field trial data. Analytic calculation formula in this paper, with simple forms and convenient application, will contribute to the analysis and calculation of lightning and transient characteristics of overhead transmission lines.

This paper summarize the existing method that can explain the lightning shield failing and put forward a new method to analyze the development of the leader and the upward leader. By using time-varying electromagnetic field analytical method. Solve the dynamic potential at the streamer zone in the bottom of leader. Give a simulation analysis for the dynamic potential and find the trend grow in exponential form. Deduce the electric field and the magnetic field from the dynamic potential in time-varying electromagnetic field.

Based on the large number of experimental data analysis and processing, a new inter-turn short circuit transformer diagnostic methods is proposed. In this paper, take the grounding current of transformer core as the signal source. Using wavelet multi-resolution technology the signal wavelet multiscale decomposition, we can get high frequency components of the signal. Achieve short-circuit fault diagnosis between transformer winding turns by comparing the number of the high-frequency component contained in different signals in the decomposition of the same scale.

High voltage overhead transmission line is an important part of the power system to ensure the safe operation of the entire power system, which is of great significance. Power line fault not only has adverse effects to the social economy, and it may also affect the stability of the power system. Transmission line faults including permanent fault and transient fault are identified quickly and accurately, which has important practical engineering significance. This paper presents a method which can be used to identify the permanent fault and transient fault of double-circuit transmission line on the same tower, fault transient voltages and currents extracted from both ends of transmission lines are as a signal source which is decomposed into a series of harmonics in order to establish a criterion function, and then the transient and permanent fault can be identified based on the changes of criterion function value.

In this article, in order to provide a reference for determining the location of fiber optic temperature probe in saving distribution transformers,we analyze the internal transformer by the basic heat transfer theory and simulate via ANSYS simulation software, determining the location of the highest temperature separately of the high and low voltage winding and iron core. The simulation results will be as a reference value for the experimental results. Therefore, it is very significant for analyzing the hottest point distribution of distribution transformers and improving thermal design of dry type transformers and temperature monitoring that the numerical simulation of dry-type distribution transformers of temperature field.

The methodology of detecting the power cable insulation defect based on DC voltage withstand test is put forward in this chapter. The discriminate function related to transient voltage and current harmonic is constructed by transient voltage and current which are regarded as signal sources during the voltage adjusting process. Then, the minimum value of discriminate function is utilized to diagnose the existence and seriousness of insulation defects for the cable. In addition, this methodology can be used to test the existence of insulation damage for cable that has undergone DC voltage withstand test. ? 2014 Springer Science+Business Media New York.

Power transformer is the important equipment in power system, once the occurrence of faults may bring serious harm to power grid, and even cause great losses. This paper proposes a transformer winding insulation defect detection method. The method only uses the impulse voltage test. It can obtain the diagnosis signal source which contains a lot of harmonic. This paper can judge the insulation defects in the location according to compare the extreme value distribution of every winding voltage and currents correlation coefficient .and can determine the coordinate values. The method does not need large or complex additional equipment, can realize the detection and diagnosis of transformer winding insulation defect location. It is image, intuitive, convenient and practical. This paper studies the insulation defects and the severity of transformer winding, puts forward the method for changing winding current and voltage detection winding insulation defects. And it uses a large number of experiments to verify the insulated and reliability of transformer winding according to different position, different types of insulation defects.

There are many factors that can lead to partial discharge in the internal of switchgear. High-frequency current will be generated on the inner wall of switchgear when the electromagnetic wave generated by partial discharge reaches the enclosure of switchgear. In the same way, more complex current signal will be produced on the outer wall of the switchgear because of the electromagnetic radiation outside the enclosure. These two currents will flow to earth through the switchgear ground wire. We can determine whether the switchgear exist partial discharge and the severity of the partial discharge by comparing the current flowing through the outer wall and the total current flowing through the ground line.

Insulator is an essential part of overhead line. In recent years, the news about the insulator flashover is increasing. The main reason of insulator flashover is insulator surface contamination. Insulator flashover is a serious threat to the safe and stable of transmission lines operation. With the development of China's comprehensive national strength, power companies and power users demand on grids stability is highly increased. Currently usual methods of insulator monitoring are ESDD (equivalent salt deposit density), experiment and on-line detecting of leakage current [. But they can't fully meet our requirements. Now this paper will present a new method, which is made correlation analysis by harmonic analysis based on two ends of the existing lines to the data acquisition apparatus of voltage and current signals. Without additional hardware devices online monitoring of insulator surface contamination can be achieved.

The AC withstand voltage test is the most common method of GIS (Gas Insulated Switchgear) on-site withstand voltage tests. The AC withstand voltage test exists in a voltage step-up process, and the voltage waveform contains harmonic components. This chapter presents a new method to diagnose the insulation defects by applying the transient voltage and current generated in the voltage step-up process. This method takes the transient voltage and current as information sources and decomposes the transient voltage and current into a series of harmonic components which are taken as the sample data set. We put the sample data into the reference database and get the numerical values of correlation coefficient. When the value reaches its maximum, the sample data set has the highest similarity to one specific reference data set. According to the known insulation fault information of this specific reference data set, we can get more insulation fault information of this GIS than the AC withstand voltage test. This method can availably get the detailed local fault information of GIS and also detect whether the GIS has the insulation damage after the GIS pass through the AC withstand voltage test or not.

In power transformation and distribution system, unplanned blackouts caused by high voltage circuit breaker faults accounted for more than 60% of the total accidents [, most of the circuit breaker faults are caused by mechanical faults. Base on circuit breaker electrical characteristics, this paper present a method of circuit breaker mechanical faults on-line monitoring. Switching on-off of circuit breakers contacts can be equivalent to a time-varying capacitance, based on equivalent circuit model, the relationship between reactive component and time can be concluded. Processing circuit breakers contacts electric signals with orthogonal decomposition and least squares curve fitting method to highlight the main characteristics of the mechanical faults. These processed data collected from different running state can create a database, taking this database as diagnostic basis to diagnose whether mechanical faults occur to circuit breaker.

Based on the method of symmetrical components of D, 11 and Y, o distribution transformer coupling two different effects of different magnetic circuit coupled to the three-phase system with a system-generated analysis and comparison. Analysis of the difference between the two groups of different connections on the transformer structure. Described in the single-phase short circuit fault clearing, 3n harmonic current suppression and affordability aspects of single-phase unbalanced load, D, ll coupling transformers are significantly better than Y,0 coupling transformer. This has necessarily important for the study of energy loss reduction.

This chapter presents a new methodology of diagnosis on insulation defects of GIS based on lightning impulse test. This methodology turns part of the lightning impulse voltage and current decomposed into a series of harmonics and constructs a discriminant function which can diagnose insulation defects of GIS. According to the extreme value of the discriminant function, the diagnosis on insulation defects of GIS can be achieved. Whether the GIS passing lightning impulse withstand voltage test has insulation damage or not can be detected, which is quite instructive for insulation supervision of GIS. ? 2014 Springer Science+Business Media New York.