Hybrid Sensing of Internal and Surface Partial Discharges in Air-Insulated Medium Voltage Switchgear

Partial discharge (PD) measurements have proved their reliability for health monitoring of insulation systems in power system components including synchronous generators, power transformers, switchgear and cables etc. Online condition monitoring and pro-active detection of PD faults have been highly demanded over the last two decades. This paper provides results from a research project to develop advanced non-intrusive sensing technologies that are cost effective, reliable and efficient for early detection of PD faults in medium voltage (MV) and high voltage (HV) air-insulated switchgear. Three sensors (high frequency E-field (D-dot) sensor, Rogowski coil and loop antenna) have been developed and tested under various PD faults and their performance were evaluated in comparison with high frequency current transformer (HFCT) which is being used commercially for PD testing and measurement. Among these three sensors, it is shown that D-dot sensor and Rogowski coil are more dependable when it comes to the PD measurements due to their high signal to noise ratio and hence high accuracy. These sensors can be customized according to a specific application and can be connected together with one data acquisition device while developing an online condition monitoring system.

Download Full-text

High-speed high-resolution laser diode-based photoacoustic microscopy for in vivo microvasculature imaging

Visual Computing for Industry Biomedicine and Art ◽

10.1186/s42492-020-00067-5 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Xiufeng Li ◽

Victor T C Tsang ◽

Lei Kang ◽

Yan Zhang ◽

Terence T W Wong

Keyword(s):

High Resolution ◽

High Speed ◽

High Performance ◽

Continuous Wave ◽

Signal To Noise Ratio ◽

Cost Effective ◽

High Signal ◽

Photoacoustic Microscopy ◽

Mouse Ear

AbstractLaser diodes (LDs) have been considered as cost-effective and compact excitation sources to overcome the requirement of costly and bulky pulsed laser sources that are commonly used in photoacoustic microscopy (PAM). However, the spatial resolution and/or imaging speed of previously reported LD-based PAM systems have not been optimized simultaneously. In this paper, we developed a high-speed and high-resolution LD-based PAM system using a continuous wave LD, operating at a pulsed mode, with a repetition rate of 30 kHz, as an excitation source. A hybrid scanning mechanism that synchronizes a one-dimensional galvanometer mirror and a two-dimensional motorized stage is applied to achieve a fast imaging capability without signal averaging due to the high signal-to-noise ratio. By optimizing the optical system, a high lateral resolution of 4.8 μm has been achieved. In vivo microvasculature imaging of a mouse ear has been demonstrated to show the high performance of our LD-based PAM system.

Download Full-text

Assessment of GRACE-FO Laser Ranging Interferometer measurements

10.5194/egusphere-egu21-1249 ◽

2021 ◽

Author(s):

Athina Peidou ◽

Felix Landerer ◽

David Wiese ◽

Matthias Ellmer ◽

Eugene Fahnestock ◽

...

Keyword(s):

High Frequency ◽

Signal To Noise Ratio ◽

Small Scale ◽

Laser Ranging ◽

High Signal ◽

Measurement Sensitivity ◽

One Year ◽

Mass Transfers ◽

Gravity Recovery ◽

System Errors

The performance of Gravity Recovery and Climate Experiment Follow&#8208;On (GRACE-FO) laser ranging interferometer (LRI) system is assessed in both space and frequency domains. With LRI&#8217;s measurement sensitivity being as small as 0.05 nm/s2 at GRACE-FO altitude we perform a thorough assessment on the ability of the instrument to detect real small-scale high-frequency gravity signals. Analysis of range acceleration measurements along the orbit for nearly one year of daily solutions suggests that LRI can detect signals induced by mass perturbation up to 26 mHz, i.e., ~145 km spatial resolution. Additionally, high frequency signals that are not adequately modeled by dealiasing models are clearly detected and their magnitude is shown to reach 2-3 nm/s2. The alternative K&#8208;band microwave ranging system (KBR) is also examined and results demonstrate the inability of KBR to retrieve signals above 15mHz (i.e., shorter than ~200 km) as the noise of the KBR range acceleration increases rapidly. Overall, the first stream of LRI measurements shows that the high signal to noise ratio allows for detection of mass transfers in finer scales, however the ability to fully exploit the high-quality signal measured by the LRI in Level 2 products is still constrained by noise of background models and other onboard instrumentation and measurement system errors.Copyright Acknowledgment: This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Science Program.

Download Full-text

53 Piscium, an SPB Star with Activity

International Astronomical Union Colloquium ◽

10.1017/s0252921100016110 ◽

2002 ◽

Vol 185 ◽

pp. 236-237

Author(s):

J.-M. Le Contel ◽

P. Mathias ◽

E. Chapellier ◽

J.-C. Valtier

Keyword(s):

High Resolution ◽

False Alarm ◽

High Frequency ◽

Signal To Noise Ratio ◽

High Signal ◽

Correlation Technique ◽

Signal To Noise ◽

Spectroscopic Observations ◽

Auto Correlation ◽

Frequency Variations

The star 53 Psc (HD 3379, B2.5IV) has been observed as variable by several authors (Sareyan et al., 1979) with frequencies around 10 c d–1 and has been classified as a β Cephei star. Conversely, other authors (e.g. Percy, 1971) found it to be constant.New high resolution, high signal-to-noise ratio, Spectroscopic observations have been performed at the Observatoire de Haute-Provence in 1996 over 11 nights. The spectral domain covers around 200 Å and is centered on Hδ. Radial velocities were deduced from an auto-correlation technique with a scatter around 0.4kms−1.No high frequency variations are observed. Three frequencies have been detected with a false alarm detection above the 1 % level. A fourth one may be present but its amplitude is below this 1 % level. Results are displayed in Table 1.

Download Full-text

Mapping Sensitive Vegetation Communities in Mining Eco-space using UAV-LiDAR

10.36227/techrxiv.16912138 ◽

2021 ◽

Author(s):

Bikram Banerjee ◽

Simit Raval

Keyword(s):

Longwall Mining ◽

Signal To Noise Ratio ◽

Cost Effective ◽

Data Retrieval ◽

Visual Assessment ◽

High Signal ◽

Fine Scale ◽

Complex Environments ◽

Mining Areas ◽

Efficient Data

Near earth sensing from unmanned aerial vehicles or UAVs has emerged as a potential approach for fine-scale environmental monitoring. These systems provide a cost-effective and repeatable means to acquire remotely sensed images in unprecedented spatial detail and high signal-to-noise ratio. It is becoming increasingly possible to obtain both physiochemical and structural insights of the environment using state-of-art light detection and ranging (LiDAR) sensors integrated onto UAVs. Monitoring of sensitive environments, such as swamp vegetation in longwall mining areas is important, yet challenging due to their inherent complexities. Current practices for monitoring these remote and difficult environments are primarily ground-based. This is partly due to an absent framework and challenges of using UAV-based sensor systems in monitoring such sensitive environments. This research addresses the related challenges in the development of a LiDAR system including a workflow for mapping and potentially monitoring highly heterogeneous and complex environments. This involves the amalgamation of several design components, which include hardware integration, calibration of sensors, mission planning, and designing of a processing chain to generate usable datasets. It also includes the creation of new methodologies and processing routines to establish a pipeline for efficient data retrieval and generation of usable products. The designed systems and methods were applied on a peat swamp environment to obtain accurate geo-spatialised LiDAR point cloud. Performance of the LiDAR data was tested against ground-based measurements on various aspects including visual assessment for generation LiDAR metrices maps, canopy height model, and fine-scale mapping.

Download Full-text

Orthogonal On-Rotor Sensing Vibrations for Condition Monitoring of Rotating Machines

10.37965/jdmd.v2i2.47 ◽

2021 ◽

Author(s):

Yuandong Xu ◽

◽

Xiaoli Tang ◽

Guojin Feng ◽

Dong Wang ◽

...

Keyword(s):

Fault Detection ◽

Condition Monitoring ◽

Signal To Noise Ratio ◽

Fault Detection And Diagnosis ◽

Vibration Measurement ◽

High Signal ◽

Rotating Machines ◽

Signal To Noise ◽

Mems Accelerometer ◽

Noise Ratio

Thanks to the fast development of Micro-Electro-Mechanical Systems (MEMS) technologies, MEMS accelerometers show great potentialities for machine condition monitoring. To overcome the problems of a poor signal to noise ratio, complicated modulation, and high costs of vibration measurement and computation using conventional Integrated Electronics Piezo-Electric (IEPE) accelerometers, a triaxial MEMS accelerometer based On-Rotor Sensing (ORS) technology was developed in this study. With wireless data transmission capability, the ORS unit can be mounted on a rotating rotor to obtain both rotational and transverse dynamics of the rotor with a high signal to noise ratio. The orthogonal outputs lead to a construction method of analytic signals in the time domain, which is versatile in fault detection and diagnosis of rotating machines. Two case studies based on an induction motor were carried out, which demonstrated that incipient bearing defect and half broken rotor bar can be effectively diagnosed by the proposed measurement and analysis methods. Comparatively, vibration signals from transitional on-casing accelerometers are less capable of detecting such faults. This demonstrates the superiority of the ORS vibrations in fault detection of rotating machines.

Download Full-text

Electrode_configuration_DNA_Sensitivity_Biomicrofluidics

10.1149/osf.io/9pebk ◽

2019 ◽

Author(s):

Sagnik Basuray

Keyword(s):

High Frequency ◽

Signal To Noise Ratio ◽

Microfluidic Channel ◽

Convective Transport ◽

Electrical Impedance Spectroscopy ◽

Detection Sensitivity ◽

High Signal ◽

Diffusion Dynamics ◽

Interdigitated Microelectrode ◽

Carbon Based

Electrical impedance spectroscopy (EIS) sensors through rapid and cost-effectiveoften suffer from poor sensitivity. EIS sensors modified with carbon-basedtransducers show a higher conductance, thereby increasing the sensitivity of the sensor towards biomolecules like DNA. However, the EIS spectra are compromised by the parasitic capacitance of the electric double layer (EDL). Here, a new shear-enhanced, flow-through nonporous, non-planar interdigitated microelectrode sensor has been fabricated that shifts the EDL capacitor to high frequencies. Enhanced convective transport in this sensor disrupts the diffusion dynamics of the EDL, shifting its EIS spectra to high frequency. Concomitantly, the DNA detection signal shifts to high frequency, making the sensor very sensitive, rapid with a high signal to noise ratio. The device consists of a microfluidic channel sandwiched between two sets of top and bottom interdigitated microelectrodes. One of the sets of microelectrodes is packed with carbon-based transducer material like carboxylated single-walled carbon nanotube (SWCNT). Multiple parametric studies of three different electrode configurations of the sensor along with different carbon-based transducer materials are undertaken to understand the fundamental physics and electrochemistry. Sensors packed with SWCNT show femtomolar detection sensitivity from all the different electrode configurations, for a short target-DNA. A 20-fold jump in the signal is noticed from the unique working electrode configuration in contrast to the other electrode configurations. This demonstrates the potential of the sensor for a significant increase in the sensitivity of the detection of DNA and other biomolecules.

Download Full-text

The Magnetic Fields in the Envelopes of Proto-Planetary Nebulae

Symposium - International Astronomical Union ◽

10.1017/s0074180900171700 ◽

1993 ◽

Vol 155 ◽

pp. 381-381 ◽

Cited By ~ 1

Author(s):

J.Y. Hu

Keyword(s):

Magnetic Field ◽

High Frequency ◽

Signal To Noise Ratio ◽

Planetary Nebulae ◽

Frequency Resolution ◽

High Signal ◽

Max Planck ◽

Molecular Line ◽

Protoplanetary Nebulae ◽

The Magnetic Field

It is possible that the magnetic field plays important role in the formation of planetary nebulae(Poscoli, 1992). In order to measure the strength of magnetic field in the envelope of protoplanetary nebulae(PPNe) we have used the Max-Planck-Institut fur Radioastronomie 100-m telescope at Effelsberg to obtain the high frequency resolution and high signal-to-noise ratio 1612 MHz spectra of PPNe, IRAS08005-2356, 18276-1431, and 20406+2953 in both circular polarization. The nature of PPN of these objects are confirmed by Slikhuis et al.(1991), Le Bertre(1987), and Hu et al.(1992) based on the extensive optical, infrared and radio molecular line observations.

Download Full-text