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

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

An improved method for fault location on transmission lines using the maximum likelihood estimate of the arrival times of reflected travelling waves is presented. The method is compared with previously proposed correlation based methods using results determined by ATP. The effectiveness of the new method for small fault angles and close in faults has been detailed. >

Maximum likelihood estimation of fault location on transmission lines using travelling waves

Energy management systems for the operation of distributed energy resources, distribution storage devices, and responsive loads will be embedded in distribution management systems (DMSs) as advanced functions that rely on accurate input data and fast communication signals. For a proper DMS design, the impact of the state estimation uncertainties and of the communication system delays should be evaluated. The paper presents an integrated software package for the cyber-physical simulation of DMS taking into account the accuracy of state estimation and measurements. The effectiveness of a wireless Wi-Max communication system has been tested on the rural Italian representative network produced by the research project ATLANTIDE. Results proved the need of cosimulation packages in modern distribution systems.

DMS Cyber-Physical Simulation for Assessing the Impact of State Estimation and Communication Media in Smart Grid Operation

Narrowband power-line communication (PLC) over distribution networks is gaining the attention of researchers, as a communication medium in future power grids. This paper investigates the application of narrowband PLC in smart distribution grids, starting from a historical overview on the accomplished technological progress and continuing with a comparison of the advantages and drawbacks of PLC technology to other smart-grid communication solutions. The analysis shows that narrowband PLC applications are best suitable for medium-voltage (MV) networks, due to the vast and complex geographical extent. The channel and topological characteristics of MV distribution networks are examined for different operational states and configurations, since they are important for the optimal design and implementation of the PLC infrastructure. The analysis is also extended to an existing overhead MV distribution network with distributed-generation units. The obtained results and the proposed methodology are useful and comprehensive tools for the efficient implementation of PLC technology in future smart grids.

Application of Narrowband Power-Line Communication in Medium-Voltage Smart Distribution Grids

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 availability of digital fault recorders at a reasonable cost allows the use of many of these devices at major substations. Thus, many cable lines have data available at both ends. The proposed scheme estimates the fault location in multi-end aged cable system using the theory of wavelet singularity detection as a powerful signal processing tool, the arrival of the first and second voltage travelling waves at both sides of the power cables can be identified reliably. 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 that causes a large error in all fault location techniques, which use the value of propagation velocity in calculations. The method is valid even with very close faults to busbars. Characteristics of the proposed protection algorithm are analysed by extensive simulation studies using ATP/EMTP. The obtained results indicate an accepted degree of accuracy for the proposed fault locator scheme.

Travelling wave-based fault location scheme for multi-end aged underground cable system

This paper describes a new method of locating the section where an electrical fault occurs on a power transmission line using Composite Fiber-Optic Overhead Ground Wires (OPGWs). This fault location (FL) method locates the fault section by measuring the current induced in the ground wire (GW), i.e., OPGW in this system. The OPGW currents are measured at many towers which divide the power line into sections. Data is transmitted to a central monitoring station as an optical signal through the optical fibers included within OPGW. Prior to the development of this new FL system, a simulation of power line faults using Electro-Magnetic Transients Program (EMTP) was conducted. As a result, the following two points were clarified; 1) Since OPGW current changes with line condition, it is quite difficult to define a fixed threshold level to locate fault sections accurately. 2) The distribution pattern of OPGW current along the power line has clear features around the fault point, so it is possible for electric power engineers to find the fault section by relative comparison. Therefore, the FL algorithm to be developed should have the capability of finding out the fault section with a human-like method of recognition. Fuzzy Theory, an attempt to include this kind of humanlike way of thinking into computers, was investigated and a new FL method applying this theory was developed. Fig. 1 shows the OPGW current distribution pattern of a typical grounding fault calculated by EMTP as an example.

K. Urasawa

Papers

New fault location system for power transmission lines using composite fiber-optic overhead ground wire (OPGW)