Influence of an inverter based DG on a double-ended fault location scheme

This paper describes the influence of Distributed Generation (DG) on a double ended fault location based on measuring the high frequency fault transients. The additional non-fundamental frequency current components from DG will influence the accuracy of an impedance based fault location technique based on non-fundamental frequencies. A double-ended impedance based fault location technique that utilizes the high frequency content (up to 5 kHz) is studied. The study showed that double-ended method is still able to locate a fault with a maximum error of 4% compared to the case without DG which showed a percentage error up to 2%

Determining the locations of faults in distribution systems

The conventional approach for estimating the locations of transmission line faults has been to measure the apparent impedance from a line terminal to the fault and to convert the reactive component of the impedance to line length. Several methods, that use voltages and currents measured at one or both line terminals, have been proposed in the past. Methods for locating faults on radial transmission lines and rural distribution feeders have also been suggested. These methods do not adequately address the problems associated with fault location on distribution systems that have single or multiphase laterals and/or tapped loads. A technique that estimates the location of a shunt fault on a radial distribution system that has several single and/or multiphase laterals has been developed. Load taps and non-homogeneity of the system are taken into account. The apparent location of a fault is first estimated by computing the impedance from the fundamental frequency voltage and current phasors, and converting the reactive component of the impedance to line length. The sequence voltages and currents at the fault are expressed as functions of the distance to the fault as well as the impedances of loads beyond the fault. The expression for the imaginary component of the fault impedance is equated to zero and the resulting equation is solved using an iterative approach. Multiple estimates may be obtained for a fault in a distribution system that has laterals. One of the estimates is identified as the most likely fault location by using information from fault indicators which are strategically placed on the laterals. The developed technique, which can handle single-phase-to-ground, two-phase-to-ground, phase-to-phase and balanced three-phase faults was tested to evaluate its suitability. Results from computer simulations of faults indicate that the proposed technique is more accurate than the reactive component method. Studies also demonstrate that the sensitivity of the proposed technique is comparable to that of the reactive component method. A prototype fault location system was also developed. The system was tested using simulated voltage and current waveforms. Results show a close agreement with those obtained from the non-real time tests

LIBRA: An inexpensive geodetic network densification system

A description is given of the Libra (Locations Interposed by Ranging Aircraft) system, by which geodesy and earth strain measurements can be performed rapidly and inexpensively to several hundred auxiliary points with respect to a few fundamental control points established by any other technique, such as radio interferometry or satellite ranging. This low-cost means of extending the accuracy of space age geodesy to local surveys provides speed and spatial resolution useful, for example, for earthquake hazards estimation. Libra may be combined with an existing system, Aries (Astronomical Radio Interferometric Earth Surveying) to provide a balanced system adequate to meet the geophysical needs, and applicable to conventional surveying. The basic hardware design was outlined and specifications were defined. Then need for network densification was described. The following activities required to implement the proposed Libra system are also described: hardware development, data reduction, tropospheric calibrations, schedule of development and estimated costs

Seismic imaging and petrology explain highly explosive eruptions of Merapi Volcano, Indonesia

Our seismic tomographic images characterize, for the first time, spatial and volumetric details of the subvertical magma plumbing system of Merapi Volcano. We present P-and S-wave arrival time data, which were collected in a dense seismic network, known as DOMERAPI, installed around the volcano for 18 months. The P-and S-wave arrival time data with similar path coverage reveal a high Vp/Vs structure extending from a depth of >= 20 km below mean sea level (MSL) up to the summit of the volcano. Combined with results of petrological studies, our seismic tomography data allow us to propose: (1) the existence of a shallow zone of intense fluid percolation, directly below the summit of the volcano; (2) a main, pre-eruptive magma reservoir at >= 10 to 20 km below MSL that is orders of magnitude larger than erupted magma volumes; (3) a deep magma reservoir at MOHO depth which supplies the main reservoir; and (4) an extensive, subvertical fluid-magma-transfer zone from the mantle to the surface. Such high-resolution spatial constraints on the volcano plumbing system as shown are an important advance in our ability to forecast and to mitigate the hazard potential of Merapi's future eruptions.We gratefully acknowledge the French Agence Nationale pour la Recherche for funding the DOMERAPI ANR project (ANR- 12-BS06-0012) and BMKG for providing data used in this stud

A comparison framework for distribution system outage and fault location methods

Finding the location of faults in distribution networks has been a long standing problem for utility operators, and an interesting subject for researchers as well. In recent years, significant research efforts have been devoted to the development of methods for identification of the faulted area to assist utility operators in expediting service restoration, and consequently reducing outage time and relevant costs. Considering today's wide variety of distribution systems, a solution preferred for a specific system might be impractical for another one. This paper provides a comparison framework which classifies and reviews a relatively large number of different fault location and outage area location methods to serve as a guide to power system engineers and researchers to choose the best option based on their existing system and requirements. It also supports investigations on the challenging and unsolved problems to realize the fields of future studies and improvements. For each class of methods, a short description of the main idea and methodology is presented. Then, all the methods are discussed in detail presenting the key points, advantages, limitations, and requirements

Depletion of groundwater resources under rapid urbanisation in Africa : recent and future trends in the Nairobi Aquifer System, Kenya

Open Access via the Springer Compact Agreement Acknowledgements: We acknowledge the Royal Geographical Society (with IBG) Environment and Sustainability Research Grant for supporting the fieldwork activities, and The World Bank/Aurecon AMEI Limited for supporting model scenarios simulations. We are also grateful to the Kenyan Water Resources Authority (WRA) and the University of Aberdeen for jointly supporting Samson Oiro’s PhD scholarship. We warmly thank WRA staff involved in data compilation and acquisition as well as the WRA offices (Nairobi and Kiambu Office) for providing the borehole completion reports and abstraction records. We thank three reviewers for their constructive comments which contributed to improve the final manuscript.Peer reviewedPublisher PD

Multiplexing electro-optic architectures for advanced aircraft integrated flight control systems

This report describes the results of a 10 month program sponsored by NASA. The objective of this program was to evaluate various optical sensor modulation technologies and to design an optimal Electro-Optic Architecture (EOA) for servicing remote clusters of sensors and actuators in advanced aircraft flight control systems. The EOA's supply optical power to remote sensors and actuators, process the modulated optical signals returned from the sensors, and produce conditioned electrical signals acceptable for use by a digital flight control computer or Vehicle Management System (VMS) computer. This study was part of a multi-year initiative under the Fiber Optic Control System Integration (FOCSI) program to design, develop, and test a totally integrated fiber optic flight/propulsion control system for application to advanced aircraft. Unlike earlier FOCSI studies, this program concentrated on the design of the EOA interface rather than the optical transducer technology itself

A FAULT LOCATION ALGORITHM FOR UNBALANCED DISTRIBUTION SYSTEM WITHOUT FAULT TYPE INFORMATION

Power system faults normally result in system damage, profit loss and consumer dissatisfaction. Consequently, there is a strong demand on precise and fast fault location estimation for power system to minimize the system restoration time. This paper examines a method to locate short-circuit faults on a distribution system with unbalanced loads without fault type information. Bus impedance matrix technique was harnessed in the fault location estimation algorithm. The system data including line impedances, source impedance and distribution system layout was assumed to be known factors, hence pre-fault bus impedance can be calculated and implemented into the algorithm. Corresponding methods to derive system matrix information were discussed. Case studies were performed to evaluate the accuracy of the fault location algorithm and illustrate the robust performance under measurements errors influences, load variation impacts and load compensation implementations. Traditional fault location methods involve current and voltage measurements mandatorily locating at each ends of faulted section to locate the fault. The method examined finds fault location for distribution system utilizing impedance matrix accompanied with sparse measurements in the power network. This method fully considers the unbalance of distribution system

Advanced flight control system study

The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed

Influence of an inverter based DG on a double-ended fault location scheme

This paper describes the influence of Distributed Generation (DG) on a double ended fault location based on measuring the high frequency fault transients. The additional non-fundamental frequency current components from DG will influence the accuracy of an impedance based fault location technique based on non-fundamental frequencies. A double-ended impedance based fault location technique that utilizes the high frequency content (up to 5 kHz) is studied. The study showed that double-ended method is still able to locate a fault with a maximum error of 4% compared to the case without DG which showed a percentage error up to 2%