Fault Factor Analysis in Complicated Electrical Engineering

Wide area adaptive backup protection is one of the research hotspots in complicated electric power system field. The researches in this paper are mainly serving wide area protection system. We will study a novel fault factor analysis in complicated electric power system, and this scheme can reduce the influence of relay protection’s wrong action device on fault detection. It has been proved by a large number of simulation experiments, even if there is the influence of random disturbance, the system failure in electric power system can be rapidly and effectively analysed by utilizing a fault factor analysis scheme. DOI: http://dx.doi.org/10.5755/j01.eee.19.10.2909


I. INTRODUCTION
Wide area adaptive backup protection is one of the research hotspots in the complicated electrical engineering field.The fixed value setting of traditional remote backup protection is acquired by off-line setting calculation.Due to the complicatedness of the system structure and the variety of the operation mode that can be considered, it is difficult to dedicate enough attention to both sensitivity and selectivity, which makes it hard to ensure the fixed value can effectively adapt to the running condition of current power grid to reach the best performance [1], [2].Because it cannot distinguish whether the malfunction is caused by internal fault or the power flow transfer, the remote backup protection makes wrong operation quite often and causes cascading trip that leads to larger range of accident.The available approach to solve those problems is using online adaptive setting algorithm to actively modify fixed value or using power flow transfer recognition algorithm to effectively lock the related protection [3]- [5].Online adaptive setting uses event trigger mode, chases the operation mode change of the power grid in real-time, and online adjusts the related fixed value of backup protection on the premise of identifying fault point to avoid mismatch protection and to improve sensitivity [6], [7].However, online adaptive setting scheme produces big error toward disturbance area (influence domain).Thus it cannot correctly reflect the actual running condition and cannot guarantee the reliability.Also, after online setting, it still needs time coordination of protection and fixed value coordination to guarantee the selectivity.Power flow transfer recognition algorithm correlates with emergence control and uses superposition principle and the grid structure before event to form power flow transfer factor and to estimate branch current [8], [9].It also compares with measured currents to determine whether the line produces power flow transfer.In practice, after removing the branch, the current of generator and load branch will change rapidly under the regulation of automatic regulating device.Together with the wide usage of the nonlinear element in the power grid, the calculation accuracy of power flow transfer factor needs to be further improved.
According to complicated electrical engineering, we have carried out a large number of basic researches.In [10], based on real-time measurement of phasor measurement units, we used mainly pattern classification technology and linear discrimination principle of pattern recognition theory to search for laws of electrical quantity marked changes.The simulation results indicate that respectively study on the phase voltage, positive sequence voltage, negative sequence voltage, phase current, positive sequence current, negative sequence current of single-phase grounding faults and the positive sequence voltage, positive sequence current of three-phase short circuit faults, the pattern classification technology and linear discrimination principle are able to quickly and accurately identify the fault components and fault sections.In [11], based on the classification criteria of multiple populations, according to different kinds of failures, we have provided an effective fault identification technique for electrical engineering.
The researches in this paper are mainly serving wide area protection system.We will study a novel fault factor analysis in complicated electrical engineering.This paper is organized as follows.In Section II, the theoretical foundation for factor analysis is introduced.In Section III, for general fault modes, the fault factor analysis in complicated electrical engineering is discussed carefully.Particularly, fully considering the influence of random disturbance, the fault factor analysis scheme is clarified in detail.Finally, the paper is concluded in Section IV.

II. THE THEORETICAL FOUNDATION FOR FACTOR ANALYSIS
Factor analysis is a kind of technology for dimension reduction and for data simplification.It can explore the fundamental structure of data by investigating the internal dependency relationship among multi-variable, and adopt a few abstract variables to represent their essential data structure.The common factors in factor analysis are common influencing factors that cannot be directly observed, but they are objective existing [12], [13].Each variable can be expressed as the sum of the linear function of common factors and special factor [14], [15], namely , where 1, 2, , This model can also be expressed in matrix form , where 11 12 1


, and satisfies:  cov( , ) 0 F   , that is, the common factors and special factors are uncorrelated, , that is, the common factors are uncorrelated and their variance is 1, , that is, the special factors are uncorrelated, but their variances are not always equal.
The ij a in this model is factor loading, it is the load of the -th i variable on the -th j factor.If the variable i X is considered as a point in m -dimensional space, then ij a is just its projection on the coordinate axis j F .In fact, A is the factor loading matrix.Assume that the original vector Then * R is the approximate correlation matrix of X , and the main diagonal element of * R is 2 i h .In fact, * R is a nonnegative definite matrix.Let * * ( ) , ., , In order to obtain where ij  is a Laplace coefficient.For * R is a symmetric matrix, then ij ji    .So: Obviously, 1 A is still a eigenvector corresponding to * 1  , and satisfies

III. FAULT FACTOR ANALYSIS IN COMPLICATED ELECTRICAL ENGINEERING
According to different kinds of short circuit faults, we have carried through large numbers of simulation experiments, and the results have demonstrated that the fault factor analysis scheme proposed in this paper is successful.
Let's take an unsymmetrical short circuit fault in IEEE 39-bus system as an example.Figure 1 presents the electric diagram of IEEE 39-bus system.In the system structure, Bus18 is the actual fault position.By BPA simulation and program calculation with MATLAB, the node negative sequence voltages have been obtained.Particularly, we have considered the influence of random disturbance.
Let's provide the critical calculated results.The component matrix is listed in Table I.

TABLE I .
THE COMPONENT MATRIX BASED ON FAULT FACTOR ANALYSIS IN IEEE 39-BUS SYSTEM.