183 research outputs found
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
Multiple bottlenecks sorting criterion at initial sequence in solving permutation flow shop scheduling problem
This paper proposes a heuristic that introduces the
application of bottleneck-based concept at the beginning of an initial sequence
determination with the objective of makespan minimization. Earlier studies
found that the scheduling activity become complicated when dealing with
machine, m greater than 2, known as non-deterministic polynomial-time
hardness (NP-hard). To date, the Nawaz-Enscore-Ham (NEH) algorithm is
still recognized as the best heuristic in solving makespan problem in
scheduling environment. Thus, this study treated the NEH heuristic as the
highest ranking and most suitable heuristic for evaluation purpose since it is
the best performing heuristic in makespan minimization. This study used the
bottleneck-based approach to identify the critical processing machine which
led to high completion time. In this study, an experiment involving machines
(m =4) and n-job (n = 6, 10, 15, 20) was simulated in Microsoft Excel Simple
Programming to solve the permutation flowshop scheduling problem. The
overall computational results demonstrated that the bottleneck machine M4
performed the best in minimizing the makespan for all data set of problems
Discrimination of PD Signal using Wavelet Transform for Insulation Diagnosis of GIS under HVDC
์ค์ ๊ธฐ ์ฐ์
์์ ๋ถ๋ถ๋ฐฉ์ ์ ๊ฒ์ถ ๋ฐ ๋ถ์ ๊ธฐ์ ์ ์ ๋ ฅ์ค๋น์ ์ํ์ง๋จ ๋ฐ ์์ฐ๊ด๋ฆฌ๋ฅผ ์ํ ๊ฐ์ฅ ํจ๊ณผ์ ์ธ ๋ฐฉ๋ฒ์ผ๋ก ๊ฐ์ฃผ๋์ด ์๋ค. ๊ทธ๋ฌ๋ ๊ฒ์ถ์ ๊ฐ๋ ๋ฐ ์ ํ๋๋ ํ์ฅ ๋
ธ์ด์ฆ์ ์ํฅ์ ๋ฐ์ ์ํ๋ ํ๊ฐ, ๊ฒฐํจ ํ๋ณ ๋๋ ์์น ์ถ์ ์ ์ค๋ฅ๋ฅผ ์ ๋ฐํ๋ค. ๊ต๋ฅ์ ์์์ ๋ถ๋ถ๋ฐฉ์ ์ ํธ์ ๋
ธ์ด์ฆ ์ ๊ฑฐ๋ ํ๋ฐํ ์ฐ๊ตฌ๋์์ง๋ง, ์ต๊ทผ ์ด์๊ฐ ๋๊ณ ์๋ HVDC์์ ๊ด๋ จ ์ฐ๊ตฌ๋ ๋ฏธํกํ ์ค์ ์ด๋ค. HVDC ๊ธฐ์ ์ด ๊ธ์ํ ๋ฐ์ ๋๋ฉด์ ๊ด๋ จ ์ ๋ ฅ์ค๋น ์ง๋จ์ ์ํ์ฌ, HVDC์์ ๋ถ๋ถ๋ฐฉ์ ์ ํธ์ ๋
ธ์ด์ฆ๋ฅผ ์ ๊ฑฐํ ํ์๊ฐ ์๋ค. ์ด๋ค ๋ฐฐ๊ฒฝ์ผ๋ก ๋ณธ ๋
ผ๋ฌธ์์๋ HVDC ๊ฐ์ค์ ์ฐ๊ตฌ์กฐ์์ ์ ์ฐ์ง๋จ์ ๊ฐ๋ ๋ฐ ์ ํ๋๋ฅผ ํฅ์ํ ๋ชฉ์ ์ผ๋ก ์จ์ด๋ธ๋ฆฟ ๋ณํ์ ์ด์ฉํ์ฌ ๋ถ๋ถ๋ฐฉ์ ์ ํธ๋ฅผ ์๋ณํ์๋ค.
์ง๋ฅ์์ ๋ถ๋ถ๋ฐฉ์ ์ ํธ๋ฅผ ๋ฐ์ํ๊ธฐ ์ํ์ฌ ์คํ๊ณ๋ฅผ ๊ตฌ์ถํ์๋ค. HVDC๋ ๋ชฐ๋๋ณ์๊ธฐ, ๊ณ ์ ๋ค์ด์ค๋ ๋ฐ ์ปคํจ์ํฐ๋ก ๊ตฌ์ฑ๋ ์ ๋ฅํ๋ก๋ก ๋ฐ์์์ผฐ๋ค. ๊ฐ์ค์ ์ฐ๊ตฌ์กฐ์์ ๋ฐ์ํ๋ ์ ์ฐ๊ฒฐํจ์ ๋ชจ์ํ๊ธฐ ์ํ์ฌ ๋์ฒด๋์ถ, ์ธํจ๋์ถ, ์์ ์
์ ๋ฐ ์ ์ฐ๋ฌผ ํฌ๋ 4์ข
์ ์ ๊ทน๊ณ๋ฅผ ์ ์ํ์๋ค. ์ ๊ทน๊ณ๋ SF6 ๊ฐ์ค๋ฅผ 0.5MPa๋ก ์ถฉ์งํ์์ผ๋ฉฐ, ์ฐจํํจ์ ์ฌ์ฉํ์ฌ ์ธ๋ถ ๋
ธ์ด์ฆ์ ์ํฅ์ ์ต์ํํ์๋ค.
4์ข
์ ๋ชจ์๊ฒฐํจ์์ ๋ถ๋ถ๋ฐฉ์ ๋จ์ผํ์ค๋ฅผ ๊ฒ์ถํ์ฌ HVDC์์ ๋ถ๋ถ๋ฐฉ์ ์ ๋ถ์ํ๊ธฐ ์ํ ์จ์ด๋ธ๋ฆฟ ๋ณํ ๊ธฐ์ ์ ์ต์ ํํ์๋ค. ์๊ด๊ณ์ ๋ฐ ๋์ ์๊ฐ์ํ ๋ฒ์ ์ด์ฉํ์ฌ ๋ถ๋ถ๋ฐฉ์ ํ์ค์ ๋ค์ํ ๋ชจ์จ์ด๋ธ๋ฆฟ์ ์ ์ฌ์ฑ์ ๋น๊ตํ์๋ค. ๊ฒฐ๊ณผ๋ก๋ถํฐ ๋์ ์๊ฐ์ํ ๋ฒ์ ์ํด ์ ์ ๋ ๋ชจ์จ์ด๋ธ๋ฆฟ bior2.6์ด HVDC์์ ๋ถ๋ถ๋ฐฉ์ ์ ํธ ๋ถ์์ ๊ฐ์ฅ ์ ํฉํ์๋ค. ์ต์ ์ ๋ฌธํฑํจ์ ๋ฐ ๋ฌธํฑ๊ฐ์ ์ ์ ํ๊ธฐ ์ํ์ฌ ๊ฐ์ ์ง์ ํ์ค ๋ฐ ๊ฐ์ ์ง๋ ํ์ค๋ฅผ ๋ชจ์ํ์์ผ๋ฉฐ, ์ ํธ-์ก์๋น, ์๊ด๊ณ์, ํฌ๊ธฐ ๋ณํ๋ฅผ ๋น๊ตํ ๊ฒฐ๊ณผ, ์ค๊ฐ ๋ฌธํฑํจ์-์๋ ๋ฌธํฑ๊ฐ์ด ์ต์ ์ ์กฐํฉ์ผ๋ก ์ ์ ๋์๋ค.
์ค์ ๋ถ๋ถ๋ฐฉ์ ๋ถ์ ๋ฐ ํ๊ฐ ์ ๋จ์ผ ํ์ค๊ฐ ์๋ ํ์ค ์ํ์ค๊ฐ ์ฌ์ฉ๋๊ธฐ ๋๋ฌธ์, ์ต์ ํ๋ ์จ์ด๋ธ๋ฆฟ ๋ณํ ๊ธฐ์ ์ ์ด์ฉํ์ฌ ๋ชจ์๊ฒฐํจ์ผ๋ก๋ถํฐ ๊ฒ์ถ๋ ๋ถ๋ถ๋ฐฉ์ ์ ํธ๋ฅผ ์๋ณํ์์ผ๋ฉฐ, ๊ทธ ํจ๊ณผ๋ฅผ ๊ณ ์ญ ํต๊ณผ ํํฐ์ ๋น๊ตํ์๋ค. ๊ฒฐ๊ณผ๋ก๋ถํฐ, ๋ถ๋ถ๋ฐฉ์ ์ ํธ ์๋ณ ์ ๊ณ ์ญํต๊ณผํํฐ์ ๋นํด ์จ์ด๋ธ๋ฆฌ ๊ธฐ์ ์ด ์ก์ ๊ฐ์์ ์๊ด๊ณ์๊ฐ ๋๊ฒ, ํฌ๊ธฐ ๋ณํ๊ฐ ๋ฎ๊ฒ ๋ํ๋ฌ๋ค. ๋ฟ๋ง ์๋๋ผ ์จ์ด๋ธ๋ฆฟ ๋ฐฉ๋ฒ์ ๋ฐฐ๊ฒฝ ์ก์, ์งํญ ๋ณ์กฐ ์ ํ ์ฅํด, ๋น์ ํ ์ก์ ๋ฐ ์ค์์นญ ์ํ์ค๋ก ๊ฐ์ญ๋ ๋ถ๋ถ๋ฐฉ์ ์ ํธ๋ฅผ ์๋ณํ๋ ๋ฐ ํจ๊ณผ์ ์ด์๋ค.
๋ณธ ๋
ผ๋ฌธ์์ ์ ์ํ ์จ์ด๋ธ๋ฆฟ ๋ณํ ๊ธฐ์ ์ ํ์ฅ์ ๋
ธ์ด์ฆ๋ก๋ถํฐ ๋ถ๋ถ๋ฐฉ์ ์ ํธ๋ฅผ ์ฑ๊ณต์ ์ผ๋ก ์๋ณํ์๋ค. ํฅํ HVDC์์ ๊ฐ์ค์ ์ฐ๊ตฌ์กฐ์ ๋ถ๋ถ๋ฐฉ์ ๊ฒ์ถ ๋ฐ ๋ถ์์ ์ ์ฉ๋ ๊ฒ์ผ๋ก ์์๋๋ฉฐ, ๋ถ๋ถ๋ฐฉ์ ๊ฒ์ถ, ์ํ๋ ํ๊ฐ, ๊ฒฐํจ ํ๋ณ ๋ฐ ์์น ์ธก์ ์ ์ ํ๋๊ฐ ํฅ์๋ ์ ์์ ๊ฒ์ผ๋ก ๊ธฐ๋๋๋ค.Contents โ
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Lists of Figures and Tables โ
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Abstract โ
ต
Chapter 1 Introduction 1
1.1 Research Background 1
1.2 Dissertation Outline 5
Chapter 2 Partial Discharge Review 7
2.1 Mechanism and Recurrence 7
2.2 Detection and Measurement 12
2.3 Analysis Methods 23
Chapter 3 Experiment and Optimization 45
3.1 Experimental Setup 45
3.2 Optimization of Wavelet Transform 49
Chapter 4 Discrimination of PD Sequences 66
4.1 DEP-type Pulse Sequence 70
4.2 DOP-type Pulse Sequence 79
Chapter 5 Conclusions 89Docto
Lightning generated electric field over land and sea at Northern Region of Peninsular Malaysia: Measuring Setup
Lightning is the transfer of significant charge between two charged object, it can appear between cloud-to-cloud, cloud-to-air and cloud-to-ground. All lightning activities are correlated with charge movement and therefore, it can be studied using measurement of electrostatic field (slow field changes), radiation field (fast field changes) and magnetic field affiliated with charge movement. The measuring equipment was a parallel flat plate and vertical whip antenna with an analog filter buffer circuit, connected to a digital high speed oscilloscope. In principle, both antenna have a similar measuring operation, with the exclusion of the antennas dimension, mode of transient recoder and the association of circuitry characteristic (decay time constant). This measurement setup are commonly used to perform electric field characterization related to various lightning events such as as preliminary breakdown, stepped leader, return stroke, subsequent return stroke, dart leader, dart-stepped leader, narrow bipolar pulses and cloud activity between strokes, such as regular pulse trains, K and M changes and chaotic pulse trains. The measurement systems are located very close to the sea, with respect in obtaining a perspicuous explaination of lightning propagation effects on sea instead on land. Noise-distorted effects in data captured usually introduce in a noisy environment or when the lightning strike far from the measurement station, thus the data gathered from the measurement need to be filter using MATLAB computer simulation before conducting further analysis. A promising wavelet 1-D technique, then, were used in signal denoising process rather using conventional filtration. In this works, the state of art in measuring vertical component of electric field focalized sea area during the thunderstorm days been demonstrate and explained
Removal of Interferences from Partial Discharge Pulses using Wavelet Transform
ย It is essential to detect partial discharge (PD) as a symptom of insulation breakdown in high voltage (HV) applications. However accuracy of such measurement is often degraded due to the existence of noise in the signal. Wavelet Transform (WT) seems to be more suitable than traditional Fourier Transform in analyzing signals with interesting transient information such as partial discharge (PD) signals. In this paper a WT method with soft thresholding is used for signal denoising. PD signals and corona obtained from actual measurements with different voltage magnitudes are processed. Processed signals show the better result.
Condition Monitoring of Power Cables
A National Grid funded research project at Southampton has investigated possible methodologies for data acquisition, transmission and processing that will facilitate on-line continuous monitoring of partial discharges in high voltage polymeric cable systems. A method that only uses passive components at the measuring points has been developed and is outlined in this paper. More recent work, funded through the EPSRC Supergen V, UK Energy Infrastructure (AMPerES) grant in collaboration with UK electricity network operators has concentrated on the development of partial discharge data processing techniques that ultimately may allow continuous assessment of transmission asset health to be reliably determined
A prototype system for detecting the radio-frequency pulse associated with cosmic ray air showers
The development of a system to detect the radio-frequency (RF) pulse
associated with extensive air showers of cosmic rays is described. This work
was performed at the CASA/MIA array in Utah, with the intention of designing
equipment that can be used in conjunction with the Auger Giant Array. A small
subset of data (less than 40 out of a total of 600 hours of running time),
taken under low-noise conditions, permitted upper limits to be placed on the
rate for pulses accompanying showers of energies around eV.Comment: 53 pages, LaTeX, 19 figures, published in Nuclear Instruments and
Methods. Revised version; some references update
De-noising of GIS UHF Partial Discharge Monitoring based on Wavelet Method
AbstractPartial Discharge (PD) happened in GIS may induce the failure of the apparatus and endanger the safety of the grid. Detection of PD with UHF sensor can find the defect earlier. In this a paper, a de-noising method based on the wavelet method is introduced to improve the accuracy of PD detection. The general wavelet de-nosing procedures are described in the paper, after that, the proposed algorithm is demonstrated by a field test
Numerical signal processing methods for partial discharge detection in more electrical aircraft
In forecoming โmore electrical aircraftsโ, aircrafts will become more compact and lighter. Hydraulic, pneumatic or mechanical systems will be replaced by electrical ones thus leading to an increased demand of electric power. The network voltage is expected to increase far above Paschenโs minimum, thus increasing the risk of partial discharges. Furthermore the use of inverter drives will be generalized and PD detection on square voltage powered equipments will become a mandatory challenge. The purpose of this study is to propose a method to denoise partial discharge signals embedded in the electromagnetic noise induced by switchings. This denoising is performed using the wavelet decomposition
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