Estimation of conductivity and permittivity of water trees in PE from space charge distribution measurements

Toyoda, T.; Mukai, Shigeo; Ohki, Yoshimichi; Li, Y.; Maéno, Takashi

doi:10.1109/94.910433

Cited by 42 publications

(15 citation statements)

References 9 publications

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“…The first degradation is a water tree. In high and medium voltage power cables, water trees may grow when they are used under the coexistence of electric field and water [5,6]. Since cables with no water-shielding layers are still being used widely, detection of water trees is of prime importance.…”

Section: Methodsmentioning

confidence: 99%

Improvement in sensitivity of broadband impedance spectroscopy for locating degradation in cable insulation by ascending the measurement frequency

Yamada

Hirai

Ohki

2012

2012 IEEE International Conference on Condition Monitoring and Diagnosis

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In order to develop a truly reliable method for locating a degraded portion in a cable, we are developing a method based on the frequency domain reflectometry and inverse fast Fourier transform (IFFT). The locating ability of this method was examined for three types of degradation given to three kinds of cables, each with a length ranging from 24.4 to 29.0 m. Namely, a vented water tree was simulated in a coaxial cable insulated with cross-linked polyethylene (XLPE) by making a tiny hole filled with a NaCl solution, and γ-ray-induced aging was given for a length of 80 cm of an XLPE-insulated triplex cable, while the mutual distance between the two conductors was expanded for 10cm in a cord insulated with polyvinyl chloride. Analyses by IFFT using the data obtained from 1 MHz to 100 or 110 MHz can locate all three types of degradation, but the resolution is poor. If the highest measurement frequency is ascended to 200 to 400 MHz, the resolution becomes better. Moreover, the spectrum indicating the degraded portion shows quite a good reproducibility unless the cable is moved. This means that this method can be a very sensitive degradation locating tool usable for real cable systems.

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Section: Methodsmentioning

confidence: 99%

Improvement in sensitivity of broadband impedance spectroscopy for locating degradation in cable insulation by ascending the measurement frequency

Yamada

Hirai

Ohki

2012

2012 IEEE International Conference on Condition Monitoring and Diagnosis

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“…They are decided by the relative permittivity and electrical conductivity of WT. Based on [14] [20] [22]we know that the maximum electrical conductivity of WT is 10 10 times the conductivity of XLPE and the largest relative permittivity of WT is 3 times the permittivity of XLPE.…”

Section: Water Treementioning

confidence: 99%

Impacts of Water-Tree Fault on Ferroresonance in Underground Cables

Sun¹,

Makram²,

Xu³

2017

JPEE

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Nowadays, more and more electrical power is being distributed to customers by underground cables rather than overhead transmission lines due to their advantage of providing better protection in inclement weather. They also have significantly reduced electromagnetic field emission because of their copper shielding. But underground cables have larger capacitance than transmission lines per unit. Thus, ferroresonance is more likely to occur in distribution systems using underground cables. Moreover, soil humidity at a depth of one meter remains 100 percent for most of the year, a factor that risks the occurrence of water tree (WT) in cables. Consequently, both ferroresonance and WT are prone to occur in underground cable systems. The objective of this paper is to determine the relationship between ferroresonance and water tree. A test system was designed to simulate and analyze ferroresonance in a cable system caused by single-phase switch and water tree. Eight scenarios of water tree were compared in the simulation. There sponses of ferroresonance are presented in this paper and two common patterns are observed from the simulation results.

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“…In this case, a short circuit is made after the application of the DC step voltage. The DC current vs. time characteristic was then measured [6,7].…”

Section: Electrical Diagnostic Testsmentioning

confidence: 99%

A systematic approach to nuclear microscopy of water trees for a large number of field‐aged HV cable samples

Ahmed

Al-Ohali

Garwan

et al. 2005

Int Trans Elec Energy Syst

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SUMMARYIn order to perform micro-PIXE measurements on water trees in underground HV cables when a large number of cable samples are involved, a sequence of tests has been devised to minimize time and effort for sample preparation, water tree detection and analysis. These tests include electrical diagnostic tests to predict the possible presence of water trees, optical microscopy on cable insulation to detect water trees in the samples screened by the electrical tests, scanning electron microscopy for detailed surface topography of water trees, and nuclear microscopy for elemental composition and distribution maps of water trees. Correlations among the results of the four types of measurements are discussed to evaluate the usefulness of the methodology.

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Estimation of conductivity and permittivity of water trees in PE from space charge distribution measurements

Cited by 42 publications

References 9 publications

Improvement in sensitivity of broadband impedance spectroscopy for locating degradation in cable insulation by ascending the measurement frequency

Improvement in sensitivity of broadband impedance spectroscopy for locating degradation in cable insulation by ascending the measurement frequency

Impacts of Water-Tree Fault on Ferroresonance in Underground Cables

A systematic approach to nuclear microscopy of water trees for a large number of field‐aged HV cable samples

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