Time domain analysis of switching transient fields in high voltage substations

Switching operations of circuit breakers and disconnect switches generate transient currents propagating along the substation busbars. At the moment of switching, the busbars temporarily acts as antennae radiating transient electromagnetic fields within the substations. The radiated fields may interfere and disrupt normal operations of electronic equipment used within the substation for measurement, control and communication purposes. Hence there is the need to fully characterise the substation electromagnetic environment as early as the design stage of substation planning and operation to ensure safe operations of the electronic equipment. This paper deals with the computation of transient electromagnetic fields due to switching within a high voltage air-insulated substation (AIS) using the finite difference time domain (FDTD) metho

Nondestructive testing of insensitive electroexplosive devices by transient techniques

Nondestructive testing of insensitive electroexplosive devices by transient technique

Three-D multilateration: A precision geodetic measurement system

A technique of satellite geodesy for determining the relative three dimensional coordinates of ground stations within one centimeter over baselines of 20 to 10,000 kilometers is discussed. The system is referred to as 3-D Multilateration and has applications in earthquake hazard assessment, precision surveying, plate tectonics, and orbital mechanics. The accuracy is obtained by using pulsed lasers to obtain simultaneous slant ranges between several ground stations and a moving retroreflector with known trajectory for aiming the lasers

The analysis and modeling of fine pitch laminate interconnect in response to large energy fault transients

In embedded applications, the miniaturization of circuitry and functionality provides many benefits to both the producer and consumer. However, the benefits gained from miniaturization is not without penalty, as the environmental influences may be great enough to introduce system failures in new or different modes and effects;Of particular interest within this research is the effect of fault transients in reduced geometries of printed circuit card interconnect, commonly referred to as fine pitch laminate interconnect. Whereas larger geometries of conductor trace width and spacing may have been immune to circuit failure at a given fault input, the reduction of the trace geometry may introduce failures as the insulating effect of the dielectric is compromised to the point where arcing occurs;To address this concern, a circuit card was designed with fine pitch laminate features in microstrip, embedded microstrip, and stripline constructions. Various trace widths and separations were tested for structural integrity (presence of arcing or fusing) at voltage extremes defined in avionics standard. The specific trace widths in the test were 4 mils, 6 mils, 8 mils, and 12 mils, with the trace separation in each case equal to the trace widths. The results of the tests and methods to artificially improve the integrity of the interconnect are documented, providing a clear region of reliable operation to the designers and the engineering community;Finally, the construction of the interconnect and the results from the test were combined to create an empirical model for circuit analysis. Created for the Saber simulator, but readily adaptable to Spice, this model will describe high-speed operation of a propagating signal before breakdown, and uses data from the experiment to calculate threshold values for the arcing breakdown. The values for the breakdown voltages are correlated to the experimental data using statistical methods of weighted linear regression and hypothesis testing

Modeling and simulation of time domain reflectometry signals on a real network for use in fault classification and location

Today, the classification and location of faults in electrical networks remains a topic of great interest. Faults are a major issue, mainly due to the time spent to detect, locate, and repair the cause of the fault. To reduce time and associated costs, automatic fault classification and location is gaining great interest. State-of-the-art techniques to classify and locate faults are mainly based on line-impedance measurements or the detection of the traveling wave produced by the event caused by the fault itself. In contrast, this paper describes the methodology for creating a database and a model for a complex distribution network. Both objectives are covered under the paradigm of the time-domain pulse reflectometry (TDR) principle. By using this technique, large distances can be monitored on a line with a single device. Thus, in this way a database is shared and created from the results of simulations of a real and complex distribution network modeled in the PSCADTM software, which have been validated with measurements from an experimental test setup. Experimental validations have shown that the combination of the TDR technique with the modeling of a real network (including the real injector and the network coupling filter from the prototype) provides high-quality signals that are very similar and reliable to the real ones. In this sense, it is intended firstly that this model and its corresponding data will serve as a basis for further processing by any of the existing state-of-the-art techniques. And secondly, to become a valid alternative to the already well-known Test Feeders but adapted to work groups not used to the electrical world but to the environment of pure data processing

Synchrophasor Assisted Efficient Fault Location Techniques In An Active Distribution Network

Reliability of an electrical system can be improved by an efficient fault location identification for the fast repair and remedial actions. This scenario changes when there are large penetrations of distributed generation (DG) which makes the distribution system an active distribution system. An efficient use of synchrophasors in the distribution network is studied with bidirectional power flow, harmonics and low angle difference consideration which are not prevalent in a transmission network. A synchrophasor estimation algorithm for the P class PMU is developed and applied to identify efficient fault location. A fault location technique using two ended synchronized measurement is derived from the principle of transmission line settings to work in a distribution network which is independent of line parameters. The distribution systems have less line length, harmonics and different sized line conductors, which affects the sensitivity of the synchronized measurements, Total Vector Error (TVE) and threshold for angular separation between different points in the network. A new signal processing method based on Discrete Fourier Transform (DFT) is utilized to work in a distribution network as specified in IEEE C37.118 (2011) standard for synchrophasor. A specific P and M classes of synchrophasor measurements are defined in the standard. A tradeoff between fast acting P class and detailed measurement M class is sought to work specifically in the distribution system settings which is subjected to large amount of penetrations from the renewable energy

The initiation of electric arcs and the possible impact in industrial environments

Advancing knowledge and understanding of electrical arc flash and arc blast hazards through experimentation, modelling and analysis is the main goal of the present thesis. To achieve this, initially, significant work has been carried out to analyse existing data on arc flash hazards and mitigation engineering practices in industrial premises. Then, experimental investigations on the electrical arc characteristics have been conducted which together with the development of an analytical model for quantification of arc's energy components have formed the core of the research project.;Electrical characteristics of the initial stage of the arc have been obtained experimentally using different test systems developed in the course of this study. Two different arc initiation mechanisms have been examined: self-breakdown spark gap (SBSG) and wire-guided spark gap (WGSG) discharge initiation. Data post-processing techniques have been developed to obtain arc voltage and current waveforms for calculating the electrical arc energy available in the discharge.;An analytical model has been developed based on the hydrodynamic approach, to further analyse the energy dissipated and to obtain the energy components associated with thermal, acoustic-kinetic and light emission processes. This analysis of the energy components provides data for safety considerations which are currently not taken into account by the existing standards. Furthermore, analysis and evaluation of the suitability of black-box models for predicting the arc characteristics during its initiation taking into account electric circuit parameters have been performed.;Initial conditions for analysis of the ratio of the arc current over voltage have been obtained from experimental waveforms to investigate the arc-electrical circuit interaction. This can be considered as a first step towards establishment of a complete accurate link between the microscale and macroscale manifestation of the arc flash and arc blast phenomena. It is envisaged that further understanding of the complex energy conversion processes taking place in the post-arc-initiation process can provide additional tools for quantifying arc energy components and improving arc flash and arc blast safety.Advancing knowledge and understanding of electrical arc flash and arc blast hazards through experimentation, modelling and analysis is the main goal of the present thesis. To achieve this, initially, significant work has been carried out to analyse existing data on arc flash hazards and mitigation engineering practices in industrial premises. Then, experimental investigations on the electrical arc characteristics have been conducted which together with the development of an analytical model for quantification of arc's energy components have formed the core of the research project.;Electrical characteristics of the initial stage of the arc have been obtained experimentally using different test systems developed in the course of this study. Two different arc initiation mechanisms have been examined: self-breakdown spark gap (SBSG) and wire-guided spark gap (WGSG) discharge initiation. Data post-processing techniques have been developed to obtain arc voltage and current waveforms for calculating the electrical arc energy available in the discharge.;An analytical model has been developed based on the hydrodynamic approach, to further analyse the energy dissipated and to obtain the energy components associated with thermal, acoustic-kinetic and light emission processes. This analysis of the energy components provides data for safety considerations which are currently not taken into account by the existing standards. Furthermore, analysis and evaluation of the suitability of black-box models for predicting the arc characteristics during its initiation taking into account electric circuit parameters have been performed.;Initial conditions for analysis of the ratio of the arc current over voltage have been obtained from experimental waveforms to investigate the arc-electrical circuit interaction. This can be considered as a first step towards establishment of a complete accurate link between the microscale and macroscale manifestation of the arc flash and arc blast phenomena. It is envisaged that further understanding of the complex energy conversion processes taking place in the post-arc-initiation process can provide additional tools for quantifying arc energy components and improving arc flash and arc blast safety

Acoustic Emission Technology for High Power Microwave Radar Tubes

Microwave tubes used in high-power radar and communications systems are expensive and have an operating life of a few thousand hours. When one fails, it is generally impossible to determine the sequence of events that contributed to its failure. Previous investigators have designed microprocessor-based systems with as many as 11 sensors to monitor tube performance, provide tube protection, and record a comprehensive tube failure history. These systems are limited by the small amount of time available during the tube’s interpulse period for data buffering and fault analysis. They work well if the microwave tube is operated with 200 or fewer pulses per second. However, many tubes are operated at up to 1000 pulses per second. In this effort, an alternative nondestructive testing technique using acoustic emission (AE) was used for in-situ monitoring of normal and abnormal performance of radar tubes, including a magnetron, a klystron, and a traveling wave tube amplifier. This technique captures changes in radio frequency (RF) output pulses due to irregular operation and it is a real-time instantaneous in-situ indicator of the performance of microwave radar tubes. It also offers the possibility of developing built-in prognostic capabilities within the radar system to provide advanced warning of a system malfunction. Understanding the sequence of events leading to a tube failure allows for better maintenance, extends the operating life of the system, and results in significant cost avoidance