scholarly journals Comparison of Low and High Frequency Partial Discharge Measurements on Stator Windings

2019 ◽  
pp. 134-138
Author(s):  
Greg C Stone ◽  
Howard Sedding
Keyword(s):  
High Frequency ◽  
Partial Discharge ◽  
Low Frequency ◽  
International Standards ◽  
Very High Frequency ◽  
Stator Windings ◽  
Advantages And Disadvantages ◽  
On Line ◽  
Winding Insulation

Partial discharge (PD) testing has been used for over 60 years primarily as a method to assess condition of the stator winding insulation in motors and generators rated 6 kV and above. More recently it has also been used by some machine manufacturers as a means of assuring the quality of the insulation on single winding elements (coils and bars). Although both on-line and off-line tests mainly use a high voltage capacitor to detect the PD, the PD measuring systems in use work either in the low frequency (LF) regime (less than about 1 MHz) or in the very high frequency (VHF) (30-300 MHz) range. By reference to several international standards, published work as well as some experiments described in this contribution, the advantages and disadvantages of the two approaches are compared. Based on this work, it is now clear that off-line PD tests should be done in the LF range. For on-line tests, either method may be used, but use of the VHF method has become more widespread with machine end users, since the owners themselves can perform and interpret the results with a relatively low risk of false indications.

Application of On-Line Ultrasonic and UHF Partial Discharge Detection in 1000kV GIS

2014 ◽  
Vol 644-650 ◽  
pp. 3480-3484 ◽  
Author(s):  
Fuan Chen ◽  
Hui Zeng Tang ◽  
Hong Gang Li
Keyword(s):  
High Voltage ◽  
High Frequency ◽  
Detection Method ◽  
Ultrasonic Method ◽  
Partial Discharge ◽  
Joint Detection ◽  
Frequency Method ◽  
Advantages And Disadvantages ◽  
On Line ◽  
Discharge Detection

This paper introduces the detecting principle、range of application and interferencerejection of Ultrasonic And UHF Partial Discharge Detection In GIS(Gas Insulated Switchgear).In view of the advantages and disadvantages of ultrasonic and UHF detection,this paper proposesa quick joint detection method, which uses UHF (Ultra High Frequency) method to online detectthe suspected discharge range in real time, adopts ultrasonic method to determine the specificdischarge points, finally through a concrete instance in a 1000KV UHV(Ultra High Voltage)Substation verified the feasibility of the joint detection method.

Dynamics of the processes in metal machining

1998 ◽  
Vol 2 ◽  
pp. 115-122
Author(s):  
Donatas Švitra ◽  
Jolanta Janutėnienė
Keyword(s):  
High Frequency ◽  
Machine Tools ◽  
Metal Cutting ◽  
Cutting Tool ◽  
Low Frequency ◽  
Metal Cutting Machine ◽  
Cutting Machine ◽  
Metal Machining

In the practice of processing of metals by cutting it is necessary to overcome the vibration of the cutting tool, the processed detail and units of the machine tool. These vibrations in many cases are an obstacle to increase the productivity and quality of treatment of details on metal-cutting machine tools. Vibration at cutting of metals is a very diverse phenomenon due to both it’s nature and the form of oscillatory motion. The most general classification of vibrations at cutting is a division them into forced vibration and autovibrations. The most difficult to remove and poorly investigated are the autovibrations, i.e. vibrations arising at the absence of external periodic forces. The autovibrations, stipulated by the process of cutting on metalcutting machine are of two types: the low-frequency autovibrations and high-frequency autovibrations. When the low-frequency autovibration there appear, the cutting process ought to be terminated and the cause of the vibrations eliminated. Otherwise, there is a danger of a break of both machine and tool. In the case of high-frequency vibration the machine operates apparently quiently, but the processed surface feature small-sized roughness. The frequency of autovibrations can reach 5000 Hz and more.

scholarly journals Peranan Lingkungan Sosial terhadap Pembentukan Karakter Peduli Lingkungan Mahasiswa Pendidikan Geografi di Universitas Samudra Langsa

2018 ◽  
Vol 10 (2) ◽  
pp. 235
Author(s):  
Fitria Mustika ◽  
Tengku Muhammad Sahudra
Keyword(s):  
Family Environment ◽  
High Frequency ◽  
Low Frequency ◽  
Measurement Scale ◽  
Education Student ◽  
Achievement Level ◽  
Very High Frequency ◽  
Environmental Care ◽  
The Family

This study aims to determine the role of the family, community, and tertiary environment towards the formation of caring character in the geography education student environment. The output of this study was a four-indexed indexed education journal and a UNIMED google scolar. Samples from the study population were 20 respondents with 30 items about questionnaires. The time of the study starts from May 2018 to October 2018. The measurement scale in this study is the scale of the briquette. Data collection by means of library studies, interviews, questionnaires, and documentation. This research was conducted by distributing questionnaire questionnaires and interviews. Based on the results of questionnaire data processing, the family environment has a very high frequency in the formation of character of the student's environmental care with an achievement level of a total score of 91%. Furthermore, the role of the campus environment also has a high frequency in the formation of the character of the student's environmental care with a total score of 89%. Whereas the family environment has a low frequency in the formation of character of student environmental care with a total score of 57%. It can be concluded that the family environment has the most role in forming the character of the student's environmental care.

scholarly journals On-line Partial Discharge Measurement of Hydrogenerator Stator Windings using Acoustic Emission Detection Techniques

2004 ◽  
Vol 124 (2) ◽  
pp. 274-280 ◽  
Author(s):  
Tadamitsu Kaneko ◽  
Akito Takemura ◽  
Osamu Takenouchi ◽  
Youl-Moon Sung ◽  
Masahisa Otsubo ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Partial Discharge ◽  
Discharge Measurement ◽  
Detection Techniques ◽  
Stator Windings ◽  
On Line ◽  
Emission Detection

Mind–body interactive qigong improves physical and mental aspects of quality of life in inpatients with stroke: A randomized control study

2019 ◽  
Vol 18 (8) ◽  
pp. 658-666 ◽  
Author(s):  
Ching-Hsiang Chen ◽  
Kuo-Sheng Hung ◽  
Yu-Chu Chung ◽  
Mei-Ling Yeh
Keyword(s):  
Quality Of Life ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
High Frequency ◽  
Standard Care ◽  
Low Frequency ◽  
Control Group ◽  
Subacute Stroke ◽  
Interactive Exercise

Background: Stroke, a medical condition that causes physical disability and mental health problems, impacts negatively on quality of life. Post-stroke rehabilitation is critical to restoring quality of life in these patients. Objectives: This study was designed to evaluate the effect of a mind–body interactive qigong intervention on the physical and mental aspects of quality of life, considering bio-physiological and mental covariates in subacute stroke inpatients. Methods: A randomized controlled trial with repeated measures design was used. A total of 68 participants were recruited from the medical and rehabilitation wards at a teaching hospital in northern Taiwan and then randomly assigned either to the Chan-Chuang qigong group, which received standard care plus a 10-day mind–body interactive exercise program, or to the control group, which received standard care only. Data were collected using the National Institutes of Health Stroke Scale, Hospital Anxiety and Depression Scale, Short Form-12, stroke-related neurologic deficit, muscular strength, heart rate variability and fatigue at three time points: pre-intervention, halfway through the intervention (day 5) and on the final day of the intervention (day 10). Results: The results of the mixed-effect model analysis showed that the qigong group had a significantly higher quality of life score at day 10 ( p<0.05) than the control group. Among the covariates, neurologic deficit ( p=0.04), muscle strength ( p=0.04), low frequency to high frequency ratio ( p=0.02) and anxiety ( p=0.04) were significantly associated with changes in quality of life. Conversely, heart rate, heart rate variability (standard deviation of normal-to-normal intervals, low frequency and high frequency), fatigue and depression were not significantly associated with change in quality of life ( p >0.05). Conclusions: This study supports the potential benefits of a 10-day mind–body interactive exercise (Chan-Chuang qigong) program for subacute stroke inpatients and provides information that may be useful in planning adjunctive rehabilitative care for stroke inpatients.

scholarly journals Effect of Closed-Loop Vibration Stimulation on Heart Rhythm during Naps

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4136 ◽  
Author(s):  
Sang Ho Choi ◽  
Heenam Yoon ◽  
Hyung Won Jin ◽  
Hyun Bin Kwon ◽  
Seong Min Oh ◽  
...  
Keyword(s):  
High Frequency ◽  
Closed Loop ◽  
Low Frequency ◽  
Heart Rhythm ◽  
Quality Of Sleep ◽  
Stimulation Condition ◽  
Term Basis ◽  
Stimulation System

Sleep plays a primary function for health and sustains physical and cognitive performance. Although various stimulation systems for enhancing sleep have been developed, they are difficult to use on a long-term basis. This paper proposes a novel stimulation system and confirms its feasibility for sleep. Specifically, in this study, a closed-loop vibration stimulation system that detects the heart rate (HR) and applies −n% stimulus beats per minute (BPM) computed on the basis of the previous 5 min of HR data was developed. Ten subjects participated in the evaluation experiment, in which they took a nap for approximately 90 min. The experiment comprised one baseline and three stimulation conditions. HR variability analysis showed that the normalized low frequency (LF) and LF/high frequency (HF) parameters significantly decreased compared to the baseline condition, while the normalized HF parameter significantly increased under the −3% stimulation condition. In addition, the HR density around the stimulus BPM significantly increased under the −3% stimulation condition. The results confirm that the proposed stimulation system could influence heart rhythm and stabilize the autonomic nervous system. This study thus provides a new stimulation approach to enhance the quality of sleep and has the potential for enhancing health levels through sleep manipulation.

scholarly journals Pansharpening with a Gradient Domain GIF Based on NSST

Electronics ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 229
Author(s):  
Jiao Jiao ◽  
Lingda Wu
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Fusion Rule ◽  
Objective Evaluation ◽  
Data Sets ◽  
Multi Scale ◽  
Guided Image Filter ◽  
Gradient Domain ◽  
Spatial Quality

In order to improve the fusion quality of multispectral (MS) and panchromatic (PAN) images, a pansharpening method with a gradient domain guided image filter (GIF) that is based on non-subsampled shearlet transform (NSST) is proposed. First, multi-scale decomposition of MS and PAN images is performed by NSST. Second, different fusion rules are designed for high- and low-frequency coefficients. A fusion rule that is based on morphological filter-based intensity modulation (MFIM) technology is proposed for the low-frequency coefficients, and the edge refinement is carried out based on a gradient domain GIF to obtain the fused low-frequency coefficients. For the high-frequency coefficients, a fusion rule based on an improved pulse coupled neural network (PCNN) is adopted. The gradient domain GIF optimizes the firing map of the PCNN model, and then the fusion decision map is calculated to guide the fusion of the high-frequency coefficients. Finally, the fused high- and low-frequency coefficients are reconstructed with inverse NSST to obtain the fusion image. The proposed method was tested using the WorldView-2 and QuickBird data sets; the subjective visual effects and objective evaluation demonstrate that the proposed method is superior to the state-of-the-art pansharpening methods, and it can efficiently improve the spatial quality and spectral maintenance.

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