On the use of continuous-wavelet transform for fault location in distribution power systems

A high impedance arcing fault due to a leaning tree in medium voltage (MV) networks is modeled and experimentally verified. The fault is represented in two parts; an arc model and a high resistance. The arc is generated by a leaning tree towards the network conductor and the tree resistance limits the fault current. The arcing element is dynamically simulated using thermal equations. The arc model parameters and resistance values are determined using the experimental results. The fault behavior is simulated by the ATP/EMTP program, in which the arc model is realized using the universal arc representation. The experimental results have validated the system transient model. Discrete wavelet transform is used to extract the fault features and therefore localize the fault events. It is found that arc reignitions enhance fault detection when discrete wavelet transform is utilized

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Modeling and experimental verification of high impedance arcing fault in medium voltage networks

This paper reviews the major contributions to the high impedance fault (HIF) detection field throughout a 48-year period, from 1960 up to 2008, from classic approaches to heuristic alg ...

Approaches in High Impedance Fault Detection - A Chronological Review

A method and system for determining a location of a phase-to-earth fault in a three-phase electric line of an electric network, the system being configured to monitor current and voltage quantities of the three-phase electric line at a measuring point and calculate a distance (d) between the measuring point and a point of fault (F) using an equation relating the current and voltage quantities to the distance, wherein the system is further configured to calculate load-compensated zero and negative sequence currents, calculate a load-compensated phase voltage of the faulted phase by using the compensated zero sequence current; and use the compensated negative sequence current and the compensated phase voltage for calculating the distance (d) between the measuring point and a point of fault (F).

System and method for determining location of phase-to-earth fault

The increased requirements on supervision, control, and performance in modern power systems make power quality monitoring a common practise for utilities. Large databases are created and automatic processing of the data is required for fast and effective use of the available information. Aim of the work presented in this thesis is the development of tools for automatic analysis of monitoring data and in particular measurements of voltage events. The main objective of the analysis is the identification of the event origin (event classification). It is shown that event classification can be achieved by considering the voltage magnitude of the three phases. In the group of events that cause a temporary decrease in voltage magnitude (voltage dips) three classes are found: fault-induced events, transformer saturation events and induction motor starting events. Measurements and simulations are used for the analysis of these events. Emphasis is given on fault-induced events that present different stages of magnitude (multistage dips) and transformer saturation dips. Different aspects regarding voltage magnitude estimation are studied using Kalman filtering. Two segmentation algorithms are proposed to divide voltage waveforms into several possible events. Kalman filtering is also used for voltage dip detection. An expert system is developed for automatic event classification and analysis. The expert system uses the voltage waveforms and distinguishes the different types of voltage dips as well as interruptions. A method for classification is used based on the proposed segmentation algorithms. The expert system is tested using over 900 measured voltage recordings. The results show that the expert system enables fast and accurate analysis of power quality measurements. One more method for automatic event classification is proposed. The method uses discrete rms voltage measurements. Discrete rms voltage measurements form a memory saving option that power quality monitors offer instead of saving the actual voltage waveforms. It is shown that classification is possible even with rms measurements using the segmentation-based approach. Power system transients are also studied. Measurements and simulations are used for analysis of these events. Aspects related to the frequency contents of these events are discussed. Overall, this thesis shows that automatic processing of power quality monitoring can be achieved by following a number of well-defined steps. Automatic classification can be applied to large databases and simplify the processing and analysis of monitoring data.

Automating Power Quality Analysis

The characteristics of the earth faults and related disturbances, recorded in medium voltage overhead distribution networks during the years 1998-1999 are described. Altogether 316 real cases were analysed. The use of subharmonic oscillation and harmonic distortion was investigated, as a means of anticipating faults. Arcing faults made up at least half of all the disturbances, and were especially predominant in the unearthed network. Fault resistances reached their minimum values near the beginning of the disturbances. The maximum currents that allowed for autoextinction in the unearthed network were comparatively small.

Earth faults and related disturbances in distribution networks

This paper presents an analysis and comparison of earth fault characteristics in the medium voltage distribution networks (20 kV) with high impedance earthing. The results presented are based on the evaluation of 341 real case data recordings, obtained from substations of distribution networks with an unearthed or a compensated neutral. The networks were mainly of overhead construction, with a smaller share of underground cables.

Characteristics of earth faults in power systems with a compensated or an unearthed neutral

Comparison of Wavelet and Differential Equation Algorithms in Earth Fault Distance Computation

This paper describes the characteristics of the earth faults and related disturbances, recorded in medium voltage overhead distribution networks during the years 1998-1999. Altogether 316 real cases were analyzed. The use of subharmonic oscillation and harmonic distortion was investigated, as a means of anticipating of faults. Arcing faults made up at least half of all the disturbances, and were especially predominant in the unearthed network. Fault resistances reached their minimum values near the beginning of the disturbances. The maximum currents that allowed for autoextinction in the unearthed network were comparatively small.

Tapio Hakola

Papers

Earth faults and related disturbances in distribution networks

Characteristics of earth faults in power systems with a compensated or an unearthed neutral

Comparison of Wavelet and Differential Equation Algorithms in Earth Fault Distance Computation

Earth faults and related disturbances in distribution networks