Doaa Khalil Ibrahim

Traveling-Wave-Based Fault-Location Scheme for Multiend-Aged Underground Cable System

This paper presents a novel wavelet-based fault-location scheme for aged cable systems when synchronized digital fault recorded data are available at the two terminals of each cable. The proposed scheme estimates the fault location in multiend-aged cable systems using the theory of wavelet singularity detection as a powerful signal processing tool. The arrival of the first and second voltage traveling waves at both ends of the power cables can be identified reliably. The developed wavelet processing scheme is applied on the modal coordinates instead of the phase coordinates. The proposed scheme has the ability to eliminate the impact of the change in the propagation velocity of the traveling waves on the fault-location calculations. This will help solve the problem of cable changing parameters, especially the change of the relative permittivity of the cable with age. The method is valid even with faults that are very close to busbars. Characteristics of the proposed fault-location scheme are analyzed by extensive simulation studies using Alternative Transients Program/Electromagnetic Transients Program. The results indicate an accepted degree of accuracy for the suggested fault locator

Closure to “Optimal Protection Coordination for Meshed Distribution Systems With DG Using Dual Setting Directional Over-Current Relays”

In the presence of distributed generation (DG), it is important to assure a fast and reliable protection system for the distribution network to avoid unintentional DG disconnection during fault conditions. In this paper, dual setting directional over-current relays are proposed for protecting meshed distribution systems with DG. Dual setting relays are equipped with two inverse time-current characteristics whose settings will depend on the fault direction. The protection coordination problem for the dual setting directional relay is formulated as a nonlinear programming problem where the objective is to minimize the overall time of operation of relays during primary and backup operation. The proposed protection coordination scheme using dual setting relays is compared against the conventional approach, which relies on the conventional one setting directional relay. The proposed scheme is applied to the power distribution network of the IEEE 30-bus system equipped with synchronous and inverter-based DG. The results show that the proposed protection coordination scheme with dual setting relay can significantly reduce the overall relay operating time, making it an attractive option for distribution systems with DG.

A wavelet-based fault location technique for aged power cables

A novel wavelet-based travelling wave cable fault locator scheme is presented in this paper. Using the theory of wavelet singularity detection as a powerful signal processing tool, the initial arrival of the voltage travelling waves at both sides of the power cable and the second arrival of the travelling waves at the first side can be identified reliably without the need for detection the sign of these waves. The developed wavelet processing is applied on the modal coordinated instead of the phase coordinates. The proposed scheme has the ability to eliminate the effect of the change in the propagation velocity of the travelling waves. This will help solving the problem of cable changing parameters especially the changing of the relative permittivity of the cable over its age. Cable changing parameters causes a large error in all fault location techniques, which use the value of velocity of propagation in calculations. Characteristics of the proposed protection algorithm are analyzed by extensive simulation studies using ATP/EMTP. The obtained results indicate an accepted degree of accuracy for the suggested fault locator. In addition, the results prove that the proposed wavelet-based scheme solves the problem of aging cables with changing parameters over the age of the power cable.

Unsynchronized Fault-Location Scheme for Nonlinear HIF in Transmission Lines

The general aim of this paper is to develop an accurate fault-location scheme that can solve the problems affecting the accuracy of the existing conventional fault locators achieving easier maintenance and restoration time reduction as well as economical aims. This consequently helps to fit the new deregulation policies and competitive marketing. This investigation successfully applies zero-sequence current (3I 0) from the two terminals for earth high impedance fault (HIF) location, or negative-sequence currents from the two terminals of one faulted phase for line-to-line fault location. The HIF location is determined within only a maximum time of one cycle. The proposed scheme is insensitive to variations of different parameters, such as fault type, HIF behavior, wide-range transmission-line parameters variation, and fault inception angle. Staged fault testing results demonstrate that the proposed algorithm has feasible performance.

An accurate scheme for fault location in combined overhead line with underground power cable

This paper presents an accurate fault location scheme for transmission systems consisting of an overhead line in combination with an underground power cable. The algorithm requires phasor measurements data from one end of the transmission line and the synchronized measurements at the most far end of the power cable. Fault location is derived using distributed line model, modal transformation theory and discrete Fourier transform. The technique can be used on-line or off-line using the data stored in the digital transient recording apparatus. The proposed scheme has the ability to locate the fault whether it is in the overhead line or in the underground power cable. Extensive simulation studies carried out using MATLAB show that the proposed scheme provides a high accuracy in fault location under various system and fault conditions.

High Impedance Faults Detection in EHV Transmission Lines Using the Wavelet Transforms

High impedance faults (HIFs) are difficult to detect by overcurrent protection relays. This paper presents an ATP/EMTP fault simulations studies based algorithm for high impedance fault detection in extra high voltage transmission line. The scheme recognizes the distortion of the voltage waveforms caused by the arcs usually associated with HIF. The discrete wavelet transform (DWT) based analysis, yields three phase voltage in the high frequency range which are fed to a classifier for pattern recognition. The classifier is based on an algorithm that uses recursive method to sum the absolute values of the high frequency signal generated over one cycle and shifting one sample. A HIF model of distribution is modified for EHV transmission lines. Characteristics of the proposed fault detection scheme are analyzed by extensive simulation studies that clearly reveal that the proposed method can accurately detect HIFs in the EHV transmission lines.

An PMU double ended fault location scheme for aged power cables

This paper presents an adaptive fault location scheme for aged power cable using synchronized phasor measurements from both end of the cable line. The proposed fault location scheme is derived using the two-terminal synchronized measurements incorporated with distributed line model, modal transformation theory and discrete Fourier transform. The proposed scheme has the ability to solve the problem of cable changing parameters especially the change of the relative permittivity over its age and thus for the operating positive, negative, and zero-sequence capacitance changes. Extensive simulation studies are carried out using alternative transients program ATP/EMTP. The simulation studies show that the proposed scheme provides a high accuracy in fault location calculations under various system and fault conditions. The results show that the proposed method responds very well insensitive to fault type, fault resistance, fault inception angle and system configuration. The proposed scheme solves the problem of aged cables with change of its electric parameters. In addition to, it gives an accurate estimation of the fault resistance.

High impedance fault detection in mutually coupled double-ended transmission lines using high frequency disturbances

Coupling Capacitor Voltage Transformer (CCVT) secondary voltages, normally applied to conventional schemes, do not comprise appropriate information for schemes that operate on high frequency fault generated transients. However it is possible to capture the required travelling wave information contained in fault transients using a high frequency tap from a CCVT. This paper presents an ATP/EMTP fault simulations studies based algorithm for half cycle high impedance fault detection. The proposed scheme implemented on two different models of HIF in extra high voltage mutually coupled double- ended transmission lines. The scheme recognizes the distortion of the voltage waveforms caused by the arcs usually associated with HIFs. The high pass filter tap yields three phase voltage in the high frequency range which are fed to Clarkes transformation to decouple the traveling waves of the mutually coupled lines and produces ground mode and aerial modes voltage components to the classifier for pattern recognition. The classifier is based on an algorithm that uses recursive method to sum the absolute values of the high frequency signal generated over one cycle and shifting one sample. Characteristics of the proposed fault detection scheme are analyzed by extensive simulation studies that clearly reveal that the proposed method can accurately detect HIFs in the EHV transmission lines within only half a cycle from the instant of fault occurrence. The reliability of the proposed scheme does not affected by different fault conditions such as fault distance and fault inception angle.

Unsymmetrical High-impedance Earth Fault Central Relay for Transmission Networks

Abstract This article presents a central relay based on wavelet transform for high-impedance earth fault detection, zone identification, location, and classification in part of the Egyptian 500-kV transmission network. The scheme recognizes the distortion of the voltage and current waveforms caused by the arcs usually associated with high-impedance earth faults for unsymmetrical faults, whether single line to ground fault The proposed discrete wavelet transform based analysis yields three phase voltages in the high-frequency range and zero-sequence root mean square current in the low-frequency range that are fed to fault detection and location algorithms, respectively, while phase currents in the high-frequency range are fed to the classification algorithm. The fault detection algorithm is based on the recursive method to sum the absolute values of the high-frequency signal generated over one voltage cycle, while the zone identification and fault location algorithms use unsynchronized zero-sequence root mean square currents. On the other hand, the fault classification algorithm is based on the currents in the high-frequency range for one-side data of the faulted line at the local relay after the detection and location process. Characteristics of the proposed central relay are analyzed by extensive simulation studies that clearly reveal that the proposed relay can accurately determine the network faulted line and can calculate fault distance with an acceptable error that does not exceed 5%. All simulation studies are carried out using a high-impedance earth fault model of a distribution system that is modified for transmission systems. An available real high-impedance earth fault case study is used to check the performance of the fault classification algorithm to classify phase and earth faults.

High-impedance fault detection in EHV transmission lines

The automatic detection of high impedance faults (HIFs) on transmission systems has been one of the most persistent and difficult problems facing utilities as a major safety concern. The paper presents two approaches to HIF detection in extra high voltage transmission lines. Both schemes analyze the nature and dynamics of the arc phenomenon related to HIFs using voltage waveforms at the relaying point. The first scheme is based on discrete wavelet transform (DWT) analysis while the second analyzes the three phase voltages using high frequency tap of the coupling capacitor voltage transformers. To ensure development of reliable algorithms, an accurate modeling of HIF is utilized with its complex characteristics such as buildup, shoulder as well as nonlinearity and asymmetry. Results of computer simulation using ATP/EMTP on 345 kV transmission line system clearly reveal that each of the proposed methods can accurately detect HIFs in the EHV transmission lines as well as their ability to discriminate clearly between HIFs and various switching conditions.