Transmission Line Sensor Research Articles

Contingency detection in modern power systems: A stochastic hybrid system method

This paper introduces a new stochastic hybrid system (SHS) framework for contingency detection in modern power systems (MPS). The framework uses stochastic hybrid system representations in state space models to expand and facilitate capability of contingency detection. In typical microgrids (MGs), buses may contain various synchronous generators, renewable generators, controllable loads, battery systems, regular loads, etc. For development of SHS models in power systems, this paper introduces the concept of dynamic and non-dynamic buses. By converting a physical power grid into a virtual linearized state space model and representing contingencies as random switching of system structures and parameters, this paper formulates the contingency detection problem as a joint estimation problem of discrete events and continuous states in stochastic hybrid systems. This method offers unique advantages, including using common measurement signals on voltage and current synchrophasors to detect different types and locations of contingencies, avoiding expensive local direct fault measurements and detecting certain contingencies that cannot be directly measured. The method employs a small and suitably-designed probing signal to sustain the ability of persistent contingency detection. Joint estimation algorithms are presented with their proven convergence and reliability properties. Examples that use an IEEE 5-Bus system demonstrate the main ideas and derivation steps. Simulation case studies on an IEEE 33-Bus system are used for detecting transmission line faults and sensor interruptions.

Modified Hilbert Resonator-Based Transmission Line Sensor for Moisture Level Estimation of Soil

Modified Hilbert Resonator-Based Transmission Line Sensor for Moisture Level Estimation of Soil

Ultra-broadband direct dielectric spectroscopy of liquids using a calibrated Microwave-Fluidic vertical Two-Wire sensor with Bi-Material 3D printed chamber

A novel ultra-broadband dielectric spectroscopy technique for liquids is introduced. A two-wire transmission line sensor is employed in which the liquid-under-test comprises fully the propagation medium ensuring high sensitivity and direct permittivity measurement. A vertical wire arrangement is exploited fed by a double-sided parallel stripline with a microstrip interface and no bandwidth-limiting impedance transformation. A seal-integrated flex-rigid 3D-printed liquid container is developed for robust assembly. A raw measured propagation constant correction is proposed through setup calibration using only one reference liquid, which can be air. Sensor operation and design aspects are discussed in detail and an exemplary sensing setup is developed for experimental validation. A set of liquids is characterized within a three-decade bandwidth up to 42 GHz and fitted into a relaxation model along with a comparison against industry-standard broadband open-coax sensor captured data. The conducted study and error analysis certified the performance of the proposed setup.

A water fraction measurement method of gas-water flow in a wide conductivity range

The water fraction of gas-water flow can be measured by a microwave-based approach, but the measurement is unstable if water conductivity is changed. To overcome this, the present study proposes an on-line water fraction measurement method taking advantages of a microwave transmission line sensor. An equivalent circuit and a two-port network are established to reveal that, in a high conductivity environment, the sensor’s S21 phase is linearly related to phase constant and can measure the water fraction. Considering an air-water stratified flow, we conduct experimental and numerical investigations on the variation of the phase against conductivity and water fraction. It is found that 3.31–8.52 S/m conductivity has no effect on the phase. Subsequently, experimental and numerical models are developed for predicting 0–100% water fraction. Both absolute errors are within 2.2% at 95% confidence probability. The simulation method is a low-cost alternative of traditional gas-water flow testing.

A Dual-Parameter Measurement Method for Oil–Water Flow Based on a Venturi Embedded With Microwave Transmission Line Sensor

Accurate and real-time measurement of water cut (WC) and flowrate of oil–water flow is a critical factor in achieving intelligent digital oil field. In this article, a dual-parameter (WC and water flowrate) measurement method for oil–water flow is proposed based on a Venturi embedded with microwave transmission line sensor (V&MS). Dynamic experiments of horizontal fine dispersed oil–water flow are conducted. A two-dimensional finite element simulation model for V&MS under the fine dispersed flow is developed to simulate microwave phase outputs at 0%–100% WC. The simulation results agree with the experiments, providing a low-cost alternative to expensive oil–water dispersed flow tests. Furthermore, it is found that the flow patterns for 0%–10% WC and 40%–100% WC are water-in-oil and oil-in-water flows, respectively, but the flow patterns for 10%–40% WC are dispersions of water-in-oil and oil-in-water flow, and 20% WC is the transition point of the dominant continuous phase. When the water phase is continuous, V&MS has a higher sensitivity to phase signals. Finally, a WC prediction model (40%–100%) is developed by combining a modified Bruggeman model with microwave transmission line theory. Then, a discharge coefficient model is developed and the water flowrate is obtained by combining the pressure drop and the predicted WC. The absolute average relative deviation (AARD) of the predicted WC and water flowrate is 1.49% and 1.54%, respectively. The results suggest that appropriate sensing technology integration can offer a powerful solution for accurate and real-time determination of dual-parameter in oil–water flow systems.

Novel Data Compression Algorithm for Transmission Line Condition Monitoring

For the problem of data accumulation caused by massive sensor data in transmission line condition monitoring system, this paper analyzes the type and amount of data in the transmission line sensor network, compares the compression algorithms of wireless sensor network data at home and abroad, and proposes an efficient lossless compression algorithm suitable for sensor data in transmission line linear heterogeneous networks. The algorithm combines the wavelet compression algorithm and the neighborhood index sequence algorithm. It displays a fast operation speed and requires a small amount of calculation. It is suitable for battery powered wireless sensor network nodes. By combining wavelet correlation analysis and neighborhood index sequence coding, the compression algorithm proposed in this paper can achieve a high compression rate, has strong robustness to packet loss, has high compression performance, and can help to reduce network load and the packet loss rate. Simulation results show that the proposed method achieves a high compression rate in the compression of the transmission line parameter dataset, is superior to the existing data compression algorithms, and is suitable for the compression and transmission of transmission line condition monitoring data.

A Transmission Line Sensor With Sensitivity Improved for Detection of Ionic Concentration in Microfluidic Channel

Microwave measurements of minute dielectric property variations have many advantages such as noninvasive test, rapid sensing capability, and being label-free. Several researches including concentration detection are promoted by measuring the minute dielectric property variations of samples. Highly sensitive and accurate device is required for measurement of electrolyte concentration in biological fluids, especially when measuring samples in nanoliter or less scale. In this paper, a miniaturized broadband coplanar waveguide (CPW) transmission-line (TL) sensor with enhanced sensitivity is proposed. The sensitive device is realized by introducing interdigital capacitance (IDC) at the central conduction band of the CPW TL. The sensor is fabricated using print circuit board (PCB) technology with a microfluidic channel designed on it. A calibration based on microwave network theory is used to obtain the characteristic impedance and propagation constant of the sensing part. And accordingly, variations in magnitude and phase of S-parameters are employed to express the changes in concentration of the sample. Furthermore, an extracted equation between S-parameters and electrolyte concentration of the sample is first proposed. Experiments show the proposed sensor can detect the minimum concentration of 0.05 g/l for the three electrolytes (NaCl, KCl, and GaCl2 in deionized (DI) water)). Compared with a corrugator coplanar transmission line and a split ring resonator senor, the proposed sensor has a much higher sensitivity. Moreover, the device is robust in front of cross sensitivity caused by external factors (such as temperature variations, moisture, etc.). Thus, the proposed sensor is well suited for low-cost, real-tine, and CMOS compatibles sensing technologies.

Research of Strain Sensor for Transmission Line Tower based on RFID

The change of foundation, line galloping and vibration will cause the change of the stress state of the tower. By monitoring the stress state of the tower, the accidents such as tower collapse and tower collapse can be forewarned in time. In view of the shortcomings of the existing tower stress monitoring device, such as inconvenient data collection and low measurement efficiency, this paper proposes a high-precision strain sensor chip and RFID technology-based strain sensor to monitor the tower strain. According to the characteristics of strain sensor collection unit and RFID technology, a low-power strain sensor for real-time monitoring of strain data of transmission towers was designed. It can be read and recorded by hand-held reader, which improves the collection efficiency of strain information of towers and reduces the manual operation. In view of the shortage of energy supply of transmission line sensors, the power consumption design extends the effective working time of the sensor.

Investigation of methanol contaminated local spirit using metamaterial based transmission line sensor

A metamaterial-based transmission line sensor was designed to determine the amount of methanol in methanol-contaminated local spirit samples both numerically and experimentally. The proposed sensor consists of a square split-ring resonator and a transmission line. The dielectric constants of four different types of branded local spirit samples were measured. Electric field distribution has been given when the sample holder was filled with branded local spirit. Then the results were compared to show that they have almost the same characteristics. After different percentages of methanol were added to the chosen branded local spirit samples their dielectric characteristics were observed. Numerical and experimental sensing studies were conducted in these methanol-branded local spirit mixtures. As the methanol content increases in the local spirit samples, the operating frequency shifts linearly. The proposed sensor has 150 MHz bandwith and is capable of determining the level of methanol content in the branded local spirit sample.

Non‐destructive detection of moisture content in Orchardgrass (Dactylis glomerate L.) silage in wrapped round bales using microstrip transmission line sensor and its transmitted microwaves

AbstractThis paper demonstrates a non‐destructive method for measuring the moisture content of silage in wrapped round bales (WRBs) via microwave signals using a microstrip transmission line (MSTL) sensor and vector network analyzer under outdoor conditions. We analyzed the relationships between the amplitude changes (Δα) and phase shifts (Δφ) of the microwave‐transmitted signals from the WRB surfaces without tearing their films. The press MSTL method was strongly suggested over the touch MSTL method for the non‐destructive measurement of WRB qualities. We also obtained strongly negative and significant correlations between the slopes of the linear regression lines (Δφ–Δα ratios) and moisture contents for frequencies in the range of 3.6–6.2 GHz. Thus, in this frequency zone, the press MSTL method can be effectively used to determine the moisture content of silage in WRBs.

Design of Transmission Line and Electromagnetic Field Sensors for DC Partial Discharge Analysis

In this paper, a testbed is designed and constructed for the investigation of DC PD pulses. The testbed is equipped with a 50 Ω transmission line (TL) that terminate to an oscilloscope for measuring the charge displacement current generated by PD pulses. Besides the oscilloscope measurements, two types of electromagnetic field sensors (D-dot and B-dot) were developed to capture the EM fields of the PD pulses propagating through the TL. The main goal of this paper is to investigate the DC PD pulses through the EM fields and the corresponding discharge current pulses that are considered as calibrating signals for the developed D-dot and B-dot sensors. The results of DC cavity discharge measured by the constructed testbed and the EM field sensors demonstrate close agreement with the reference PD pulses measured via oscilloscope.

Grease oil humidity sensor by using metamaterial

Interaction between water and lubrication grease oil is not desirable, but it is not inevitable. The operational life of the machine component is influenced by humid grease oil. Metameterial-based transmission line sensor application is proposed and its operation is validated both numerically and experimentally by inserting grease oil samples in the sample holder. The proposed sensor structure is able to determine the humidity ratio of grease oil samples. The proposed structure shifts resonance frequency to react to the grease oil’s dielectric constant. The frequency shift of grease oil samples is monitored as about 300 MHz’s. Linearity characteristic between resonant frequency and dielectric constant value is validated. The novelty of this article is that no such study has been conducted by employing non-destructive methods which provide long-term stability of the sensor structure.

Exceptional Points of Degeneracy Directly Induced by Space–Time Modulation of a Single Transmission Line

We demonstrate how exceptional points of degeneracy (EPDs) are induced in a single transmission line (TL) directly by applying periodic space-time modulation to the per-unit-length distributed capacitance. In such space-time modulated (STM)-TL, two eigenmodes coalesce into a single degenerate one, in their eigenvalues (wavenumbers) and eigenvectors (voltage-current states) when the system approaches the EPD condition. The EPD condition is achieved by tuning a parameter in the space-time modulation, such as spatial or temporal modulation frequency, or the modulation depth. We unequivocally demonstrate the occurrence of the EPD by showing that the bifurcation of the wavenumber around the EPD is described by the Puiseux fractional power series expansion. We show that the first order expansion is sufficient to approximate well the dispersion diagram, and how this "exceptional" sensitivity of an STM-TL to tiny changes of any TL or modulation parameter enables a possible application as a highly sensitive TL sensor when operating at an EPD.

Design of Hybrid Energy Harvesting Self-Powered Power Supply for Transmission Line Sensor

In order to realize the self-power supply of the wireless temperature sensor at the tension clamp of the high-voltage transmission line, the environmental energy is harvested and stored, and to power the transmission line sensor nodes. A hybrid environment energy harvesting system for the transmission line is designed, which harvests the solar energy and transmission line vibration energy in the environment and harvests the solar energy and the piezoelectric ceramic through the photovoltaic panel. The output voltage of the photovoltaic cell is low under weak light. A new type of energy harvesting circuit is designed for the low output voltage of the photovoltaic cell, which can efficiently harvest the light energy in the transmission line. However, the vibration frequency of the transmission line is low, the structure of piezoelectric vibration energy harvester is designed by finite element method, the natural frequency is close to the vibration frequency of the excitation source, and the energy utilization ratio is the largest. The two energy collectors are impedance matched respectively in order to increase the energy output power of the whole system. The system is controlled with supercapacitor by energy management mode, which provides stable electric energy for load and realizes the sustainable self-power supply of wireless temperature sensor.

Non‐destructive prediction of forage crop moisture contents using microwave transmitted signals with a microstrip transmission line sensor

AbstractThis paper describes a non‐destructive method for using microwave transmitted signals to measure the moisture content of silage wrapped with plastic films. To collect measurements by a vector network analyzer, each bag of silage was placed on a microstrip transmission line without destruction of the films. Both rye and corn were tested. Significant linear relationships between the amplitude change (ΔA) and phase shift (Δφ) were obtained except for with fully dried corn, and the corresponding R2 values between ΔA and Δφ were 0.8 or greater. The slopes, which represent the ratio of phase shift to amplitude change (Δφ–ΔA ratio), depended on the frequency and moisture content. R2 values between the Δφ–ΔA ratio and moisture content of rye and corn were greater than 0.8 at the frequency of 3.6 GHz or above except for with fully dried corn samples. At 3.6 GHz, significant linear relationships between the Δφ–ΔA ratio and moisture content were obtained for rye and corn. Furthermore, the slope and intercept of the linear regression line between the Δφ–ΔA ratio and moisture content of rye were not significantly different from those of corn. These results illustrate the potential of the non‐destructive moisture content measurement method with microwave transmitted signals for silage materials with high moisture contents.

Broadband Dielectric Spectroscopy of Cell Cultures

Broadband dielectric spectroscopy measurements of biological materials within RF/microwave range can reveal cellular information, which is of important value in biological and medical researches. Here, we present a platform that combines a miniaturized coplanar waveguide (CPW) transmission line (TL) sensor and a special CPW-fed interdigitated capacitor (IDC), which allows us to measure the complex permittivity of cell cultures from 300 kHz to 50 GHz. The CPW-TL and CPW-IDC sensors are integrated with an SU-8 microfluidic channel, enabling measurements of microliter or even nanoliter volumes of liquids and suspensions. Due to the accurate alignment of the SU-8 polymer and the reliable liftoff fabrication procedure, we are able to minimize the measurement errors caused by the sensors’ dimension tolerance. To ensure accurate complex permittivity extraction of the tested material, related calibrations and deembedding processes are explained. With the measurement of deionized water as a validation, the platform is used to measure the complex permittivity of both a yeast cell culture and a mammalian cell culture. We elaborate on the interesting findings and discuss future possibilities.

A Modeling Procedure of the Broadband Dielectric Spectroscopy for Ionic Liquids.

The dielectric spectroscopy (DS) measurement is an attractive noninvasive method to reveal the intrinsic information of biological materials and cell cultures. However, the presence of a double layer due to electrode polarization within the lower RF and microwave range significantly affects the accurate analysis of dielectric properties of ionic liquids. In this paper, we measure the broadband DS of five saline solutions with a microfluidic coplanar waveguide (CPW) transmission line sensor across the frequency range from 40 kHz to 110 GHz. Derived from a parallel-plate structure that is transformed from the quasi-TEM CPW sensor through a conformal mapping technique, a broadband spectroscopy modeling method is proposed, where a Cole-Cole function or a constant phase element formula is used depending on the ionic concentrations and the measurement window. Validation analysis on the five saline solutions demonstrates the capability of the modeling method in separating relaxation properties of the bulk sample from the double-layer effects.

Liquids Permittivity Measurement Using Two-Wire Transmission Line Sensor

A novel method for the measurement of complex permittivity of liquid dielectric materials in a wide frequency range is proposed. The technique utilizes an open-ended two-wire transmission line sensor that is submerged in a liquid-under-test to determine its complex permittivity from the measured differential reflection coefficient. The proposed approach has been theoretically analyzed to derive the appropriate sensor’s model and the required calibration procedure as well as experimentally validated by measurements of three liquids having frequency-dependent complex permittivity. Moreover, measurement accuracy analysis has been provided, including the method‘s uncertainty estimation and error sources’ discussion. Finally, the measured permittivity of each liquid has been compared against tabularized data. Good agreement has been obtained proving the validity and applicability of the proposed method.

Suppression of the skin effect in radio frequency transmission lines via gridded conductor fibers

Microwave propagation in transmission lines is fundamentally limited in bandwidth and reach by the skin and proximity effects. The resultant current crowding imparts a square-root frequency dependence on attenuation, and ultimately limits the spatial resolution of distributed transmission-line sensors and the data rate of communication systems. In this letter, we numerically analyze the microwave attenuation and impedance in μm-scale gridded fiber structures with currents arranged in a checkered pattern. The checkered lattice of currents significantly mitigates both the skin and proximity effects, and exhibits an unprecedented bandwidth (in excess of 1 GHz) of frequency-flat attenuation in a relatively small physical footprint (∼0.01 mm2).

Miniaturized Transmission-Line Sensor for Broadband Dielectric Characterization of Biological Liquids and Cell Suspensions

The nondestructive characterization of biological liquids and cell suspensions using electromagnetic waves in the microwave frequency range calls for accurate and sensitive measurement devices. Especially when reducing the sample volume, the sensitivity becomes a critical design parameter for broadband sensors. In this paper, a miniaturized transmission-line sensor based on a coplanar waveguide is used to characterize the permittivity of nanoliter volumes of biologically relevant liquids and cell suspensions. The sensor’s sensitivity is increased by means of electrically small discontinuities within the sensing section. The biological samples are guided across the sensor in a microfluidic channel, which is fabricated using microsystems technology. The sensor is used between 850 MHz and 40 GHz to detect the broadband permittivity of liquid samples such as aqueous salt and protein solutions. The experimentally detected contrast between living and dead Chinese hamster ovary cells in suspension is significant despite the small sample volume.