Combined Transmission Line Research Articles

A new and accurate fault location algorithm for combined transmission lines using Adaptive Network-Based Fuzzy Inference System

This paper presents a new and accurate algorithm for locating faults in a combined overhead transmission line with underground power cable using Adaptive Network-Based Fuzzy Inference System (ANFIS). The proposed method uses 10 ANFIS networks and consists of 3 stages, including fault type classification, faulty section detection and exact fault location. In the first part, an ANFIS is used to determine the fault type, applying four inputs, i.e., fundamental component of three phase currents and zero sequence current. Another ANFIS network is used to detect the faulty section, whether the fault is on the overhead line or on the underground cable. Other eight ANFIS networks are utilized to pinpoint the faults (two for each fault type). Four inputs, i.e., the dc component of the current, fundamental frequency of the voltage and current and the angle between them, are used to train the neuro-fuzzy inference systems in order to accurately locate the faults on each part of the combined line. The proposed method is evaluated under different fault conditions such as different fault locations, different fault inception angles and different fault resistances. Simulation results confirm that the proposed method can be used as an efficient means for accurate fault location on the combined transmission lines.

A Simple Method for Evaluating Ground-Fault Current Transfer at the Transition Station of a Combined Overhead-Cable Line

When a substation is fed by a combined overhead-cable transmission line, a significant part of the ground fault current flows through cable sheaths and is discharged into the soil at the transition station where cables are connected to the overhead line. Such a phenomenon, known as ldquofault application transfer,rdquo may result in high ground potentials at the transition station which may cause shocks and equipment damage. The scope of this paper is to present new analytic formulas which can be used for the direct calculation of the fault current transferred at the transition station and its ground potential rise as well as the substation earth current. The proposed formulas allow evaluating the influence of the main factors to the fault application transfer phenomenon and can be employed, at the preliminary design stage, to easily assess the most appropriate safety conditions to avoid dangerous effects.

Negative permeability around 630 nm in nanofabricated vertical meander metamaterials

AbstractWe demonstrate a new design of a 3‐dimensional meander structure that exhibits negative permeability with a broad bandwidth between 550 nm and 665 nm. The structural design allows for full coupling of the magnetic field component at all angles of incidence. We compare our structure with other metamaterial structures with respect to the series capacitance contributions of the different metamaterials. The investigation of optical metamaterials is carried out combining transmission line analysis with numerical simulations of Maxwell's equations. The analysis is demonstrated for typical split ring structures and the novel 3D meander metamaterial structures. Comparing the resulting scattering parameter spectra as well as the retrieved effective material parameters, we find that transmission line description remains valid for metamaterials at optical frequencies. We find in addition that the longitudinal capacitance is the decisive parameter to achieve negative permeability with a broad bandwidth at optical frequencies. For experimental verification we manufactured split‐ring resonator structures and meander metamaterial structures with linewidths down to 30 nm, element sizes down to 100 nm, and periods between 200 nm and 350 nm. For meander metamaterial structures a permeability value of –1 was achieved within a bandwidth of 50 nm centered at 630 nm. The largest absolute value of –4.5 was achieved at 650 nm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Pulsed Power Supply Based on Power Semiconductor Switches and Transmission Line Transformer

Transmission line transformers (TLT's) as pulse transformers have received increasingly more attention due to their excellent frequency response characteristics over conventional wound transformers. This transformer basically consists of equal lengths of transmission line (normally coaxial cables are used) connected in parallel at the input side of the transformer, and in series at the output side so that the output voltage can be boosted in proportion. Because the reactance of the outer conductor increases with the rise of the frequency of the input voltage, the output voltage of each transmission line can be isolated mutually when the frequency is high enough. Then, the output voltage will be amplified through the voltage superposition. To minimize the substantial loss of voltage gain and obtain a low pulse droop rate, one stage transformer is entwined together as a unit, the number of stages of the transformer can increase easily by piling units one by one. This spiral construction makes the transmission line transformers much more compact. On the other hand, with the development of modern semiconductor technology, high voltage, fast rise time power semiconductor devices have been produced, the collector emitter breakdown voltage of one IGBT is to 1.7 kV and the rise time is 100 ns. This paper describes a kind of compact pulse power supply constructed by combining transmission line transformer and modern power semiconductor devices-IGBTs. High voltage IGBTs (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CES</sub> =1.7 kV) have been used as charge switches, short pulses can be obtained at the input port of the transformer, then the output pulse amplitude is 10 kV through a 10-stage transmission line transformer. Finally, the output voltage pulse waveforms are given in the paper.

Wavelet and neuro-fuzzy based fault location for combined transmission systems

This paper describes the fault location algorithm using neuro-fuzzy systems in combined transmission lines with underground power cables. The neuro-fuzzy system consists of two parts to perform different tasks. One is to discriminate the fault section between overhead and underground using the detailed coefficients obtained by wavelet transform. The other system calculates fault location. The algorithm for fault location again is divided into two parts: one to calculate the fault location on the overhead lines, the other one for the underground cable section. This system shows excellent results for discrimination of fault section and calculation of fault location.

Characterization of self-heating effects in semiconductor resistors during transmission line pulses

The purpose of this work is the experimental extraction of the local average temperature occurring in silicon resistors when a transmission line pulse is applied. The local temperature is determined by combining transmission line pulses of different amplitude and at different ambient temperatures with three-dimensional electro-thermal simulation. The obtained calibration curves can be applied to convert the phase shift information as obtained by interferometric techniques (e.g. in Transient Interferometric Mapping) into absolute temperature readings.

Fault Location Using Wavelet Transform in Combined Transmission Systems

This paper describes a fault location algorithm in actual combined transmission systems of overhead line with underground power cables. The algorithm to calculate the fault location is developed based on discrete wavelet transform(DWT) and travelling wave theory. The proposed algorithm is using the transient signal data from one end of the transmission line instead of the signals from both ends. In addition, the method to discriminate fault point between overhead line and underground power cable section is also proposed. Various simulations are performed to verify the accuracy and effectiveness of the proposed algorithm using EMTP/ATP and Matlab. The simulation results proved that the proposed method has the excellent ability to discriminate the fault section and to locate the fault in the combined transmission lines

Non-uniform triggering of gg-nMOSt investigated by combined emission microscopy and transmission line pulsing

The triggering of grounded-gate nMOS transistors and field-oxide devices, essential for optimized protection design, is addressed by transmission line pulser (TLP)-pulsed emission microscopy. Current non-uniformity and instability effects in snapback operation under DC and TLP conditions are demonstrated. The comprehensive correlation of emission and electrical behavior allows an improved interpretation of device operation. Technological influences on the trigger uniformity are discussed.

Characterizing ultrasonic transducers using radiation efficiency and reception noise figure

Transducer performance is considered separately for transmission and reception operations. The transmission operation is traditionally characterized by its traditional transfer function. Using a Thevenin source, the transfer function may be scaled to become the absolute radiation efficiency. Transmission lines are accurately modeled, and a matched impedance design is recommended. The reception operation also is characterized by its traditional transfer function. However, reception sensitivity is defined as the signal-to-noise ratio achieved by the combined transducer, transmission line, and preamplifier. The thermal noise arises from the media and other noise sources contributed by the transducer, transmission line, and preamplifier. An absolute sensitivity measure is defined as the acoustic noise figure, which is the sum of individual transducer and preamplifier noise figures. The transducer noise figure is independent of the receiver load impedance and depends critically on dissipative loss. Preamplifier noise figure performance requires noise matching to the transducer. High performance design methods are presented that incorporate transmission lines, which include loss. Modeled examples are used to demonstrate performance.

DC power limitation of the heterojunction bipolar transistor with dot geometry: Effect of base potential distribution on thermal runaway

The d.c. power limitation of a conventional HBT with dot geometry was studied theoretically using combined electro-thermal and transmission line models. In most cases, the thermal runaway occurs at a power level lower than that set by the intrinsic electronic property of the device. The dependence of the d.c. thermal runaway threshold power density, P max, on the emitter dot radius and emitter ballast resistance was calculated. Increasing emitter dot radius lowers P max. Although ballast resistance increases P max, the effect reduces as the emitter dot radius increases. This is caused by the non-uniform potential distribution in the base layer. When thermal runaway is considered, the nonuniform base-emitter potential offsets the improvement of the power handling capability by the physical ballast resistance. Conventional HBTs with a large radius (greater than 4 μm) exhibit a small P max caused by thermal effect. This threshold power density can be increased drastically by using the thermal shunt technique.

Microstrip‐slot and coplanar waveguide‐slot lines with very high dielectric constant substrates for application in high‐speed optoelectronics

AbstractThis article shows that the microstrip‐slot line and the novel coplanar waveguide‐slot line printed on substrates with very high dielectric constant (εr = 38 and ε = 80) are ideal for the construction of the microwave circuitry within packages of optoelectronics components. These combined transmission lines allow the realization of impedance levels not achieved with conventional structures on such substrates, due to small, unfeasible transversal dimensions. The spectral domain approach is used in the analysis of the transmission lines. The adequacy of the analysis is confirmed experimentally. © 1994 John Wiley &amp; Sons, Inc.

Performance study of the reactively loaded power amplifier by transmission line modeling (TLM) with exponential switching resistance (ESR)

AbstractA model combining transmission line modeling (TLM) and exponential switching resistance (ESR) of active devices is introduced in the equivalent circuit to simulate the real performance of the reactively loaded power amplifier. Using the TLM, the distributed circuit parameters can be controlled by the time step size, and the collector efficiency can be more accurately evaluated by introducing the ESR into the equivalent circuit. The TLM together with the ESR element provides a simple algorithm to be implemented, and is favorable for optimization of high‐efficiency performance in the rf range. © 1993 John Wiley &amp; sons, Inc.

Study of combined transmission line for high power wave generated by a gyrotron in the millimetre wavelength range

Abstract A powerful millimetre-wave line transmitting energy from a gyrotron to a tokamak is studied. The line is open and combines mirrors and sections of an irregular oversized circular waveguide. The construction of the transmission line units is improved to provide selectivity for the operating TE01 mode. Particularly, the open quasioptical elbow operating at the long-wave region of the millimetre range and rotating the line by an angle of 90° is experimentally investigated. The operating TE01 mode insertion losses are 0.2-0.3 dB with a 4% bandwidth.