Transmission lines are designed to transfer electric power from source locations to distribution networks. However, their lengths are exposed to various faults. Protective relay and fault recorder systems, based on fundamental power frequency signals, are installed to isolate and the faulty line and provide the fault position. However, the error is high especially in transmission lines. This thesis investigates the problem of fault localization using traveling wave current signals obtained at a single-end of a transmission line and/or at multi-ends of a transmission network. A review of various signal processing techniques is presented. The wavelet transform is found to be more accurate than conventional signal processing techniques for extracting the traveling wave signals from field measurements.

In this thesis, an optimization method has been developed to select the best wavelet candidate from several mother wavelets. The optimum mother wavelet was selected and used to analyze the fault signal at different details' levels. The best details' level, which carries the fault features, was selected according to its energy content. From the line and network data, the traveling wave speed is calculated for each line using the optimum mother wavelet at different detail levels. Accurate determination fault location depends on the proper details wavelet level as well as the propagation speed. A high frequency current transformer model has been verified experimentally using impulse current signals at the high voltage laboratory, Helsinki University of Technology.

Single-end method has been studied for several transmission line configurations, including lines equipped with/without overhead ground wires, counterpoises, or overhead ground wires and counterpoises. The time difference between the aerial and ground mode has also been investigated for these line configurations.

Multi-ended method, using recordings sparsely located in the transmission network, has been proposed to overcome the weakness of the single-end method. The method is based on extracting the fault transient signals from at least two monitored buses and using the double-end method assisted by the shortest path algorithm is used to find the minimum travel time of these signals to the nearest bus.

Validation of the fault location is performed using the ATP/EMTP transient simulations. The method is verified using field data from five traveling wave recorders installed at pre-selected buses of the Finnish 400-kV transmission network.

The algorithm will allow utilities to accurately locate line faults the knowledge of transient current signals, network topology, and the shortest-path algorithm. The thesis, which genuinely provides an economic approach to fault location of transmission systems consistent with today's needs, provides a good foundation for further developments.

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Power transmission line fault location based on current traveling waves

Induction motors constitute the largest proportion of motors in industry. This type of motor experiences different types of failures, such as broken bars, eccentricity, and inter-turn failure. Stator winding faults account for approximately 36% of these failures. As such, condition monitoring is used to protect motors from sudden breakdowns. This paper proposes the use of neural networks as an efficient diagnostic tool for estimating the percentage of stator winding shorted turns in three-phase induction motors. A MATLAB-based model was developed and simulated under different fault-load combination cases for different sizes of motors. The motor’s developed electromechanical torque was selected as a fault indicator. For the design and training of the neural network, the mean, variance, max, min, and F120 time based on statistical and frequency-related features were found to be very distinct for correlating the captured electromechanical torque with its corresponding percentage of shorted turns. In the training phase of the neural network, five different motors were used and are referred to as seen motors. On the other hand, for testing the efficiency of the developed diagnostic tool, the electromechanical torque under different fault-load combination cases, previously never seen from the first five motors and those of two new motors (referred to as unseen), was used. Testing results revealed accuracy in the range of 88–99%.

https://www.mdpi.com/1996-1073/11/3/653/pdf

An efficient stator inter-Turn fault diagnosis tool for induction motors

Unsynchronized fault-location technique for two- and three-terminal transmission lines

Faulty feeder detection of single phase-earth fault based on fuzzy measure fusion criterion for distribution networks

Since feeders have complicated laterals connected with unbalanced loads, the location of a ground fault is a challenge in radial distribution networks. Furthermore, lower short-circuit current due to the high value of fault resistance, which is common in the distribution network, will make it even more challenging to identify the fault location. Taking advantage of increasing number of intelligent electronic devices installed in the modern distribution network, the monitoring, and automation of distribution systems can be improved by smart feeder meters. On the basis of the voltage information from the downstream sub-laterals, a novel fault location method involving distributed voltage measurement is proposed in this study. The first step in the proposed method is to identify the fault lateral in the main lateral. In a zero-sequence components network, the position of nodes in the main lateral is iterated to judge if the calculated voltage at the end matches the measured one by a smart feeder meter. The second step is to identify the fault section accurately by combining the voltage information from main lateral or other sub-laterals. Finally, a precise fault location can be attained via an iteration search in the fault section. Two distribution test systems simulated in power systems computer-aided design/electro-magnetic transient design and control with 34-node and 134-node have been employed to evaluate the effectiveness of the proposed algorithm under various ground fault scenarios. The simulation results show that the proposed method is robust since it offered a good performance for ground faults identification with low and high values of impedance occurring at different locations. Furthermore, it is also suitable for the system with distributed generations and dynamic loads.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-gtd.2017.1166

Ground fault location in radial distribution networks involving distributed voltage measurement

Induction motors play a vital role in industrial applications. Early detection of abnormalities in the motor would help to avoid costly breakdowns. Realizing a versatile modeling of motor winding faults is essential for developing and evaluating protection functions. Accordingly, this article presents an accurate mathematical model for stator winding faults in induction motors for both transient and steady-state analysis. This model is based on the d-q-axis theory and is valid for phase-to-ground, phase-to-phase, and turn-to-turn faults. These turn-to-turn shorts arise as one of the most prevalent and potentially destructive electrical faults in induction motors. For investigating the performance of the proposed modeling, an experimental setup is structured with a 0.5-HP, 2-pole, 380/220-V squirrel-cage induction motor. The motor stator winding was rewound for enabling a turn-to-turn fault application. The digital signal processing board (DS1003) is employed for data acquisition and recording pur...

Modeling and Experimental Investigation of Stator Winding Faults in Induction Motors

This study integrates earth fault location computation with fault management-control schemes for distribution networks. To realise this target, a panel substation is located at the lateral outlet. The faulted section is identified precisely via a fault-location algorithm. Then, isolating the faulted section is accomplished through control signals between the lateral-panel substation and the faulted section isolators. The service restoration is achieved by a direct communication between the lateral-panel substation and the feeder primary substation. The proposed fault-location algorithm is based on the pure fault circuit with the initial condition of the earth fault using the measurements at each lateral panel. For phase-to-ground fault, the initial condition is the series connection for the sequence networks from the fault point. For phase-to-phase-to-ground fault, the initial condition is that the summation of the sequence currents at the fault point is equal to zero. The proposed fault-location algorithm is, therefore, suitable for equipping distribution systems with distributed generation. Moreover, it is applicable for earthed or unearthed networks with all possibilities of transformer connection and load taps. For investigation purposes, simulation tests are performed using the IEEE 33-bus automated feeder example. The simulation test results corroborated the efficacy of the proposed fault management system.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-gtd.2015.1143

Abdel Maksoud I. Taalab

Papers

Modeling and Experimental Investigation of Stator Winding Faults in Induction Motors

Incorporating earth fault location in management-control scheme for distribution networks

Impact of high resistance arcing fault characteristics on behavior of DWT-based detection in MV networks