Optical, electrical and electromechanical measurement methodologies of field, charge and polarization in dielectrics

Zahn, M.

doi:10.1109/94.729687

Cited by 40 publications

(12 citation statements)

References 42 publications

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“…In the following, we will discuss briefly how such an optical phase retardation distribution is pro duced when light is passing through a dielectric material. 3.1 .1…”

Section: Fundamentalsmentioning

confidence: 98%

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Takada¹

1999

IEEE Trans. Dielect. Electr. Insul.

197

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Much progress had been made during the last two decades in acoustic and optical methods for measuring charge distributions in dielectrics. A review on this topic is given, which mainly covers the past research activities associated with that at our laboratory. For acoustic methods, we will discuss and compare the pulsed electroacoustic (PEA) and pressure wave propagation (pwP) methods and present some of the results that enabled us to gain physical insights into the charge dynamics within solid plate samples and coaxial cables. For optical methods, we will discuss the Pockels effect technique that is used for the dynamic measurement of surface charge distributions, and the Kerr effect technique that is developed for measuring electric field distributions within liquid dielectrics. 1 INTRODUCTION T HE Poynting vector represents a flow of electric power equivalent to EXH [W 1m2], where E [V 1m] represents electric field inten sity and H [Aim] the magnetic field intensity. To facilitate the transmission of large amounts of electric energy, which has its equivalent in a large Poynting vector, researchers must strive to increase either the magnetic field jj or the electric field E. An increase of H can be ac complished by using superconducting transmission lines, while that of if can be achieved by increasing the transmission voltage. However, at present, the development of a practical, usable superconducting trans mission system has not been fully realized. Therefore, we have to con tinue our efforts in obtaining high E through a HV transmission system.. To this end, much research on the properties of dielectric and insulating materials will have to be conducted. This is one of the goals of the present workThe advancement of excellent electric insulating materials, in which electric power flows in the form of a Poynting vector, has made a sig nificant contribution to the development of electric power engineer ing, electronics engineering and electronic communication systems in present everyday life, Many researches have been conducted on de voltage-current characteristics by electric conductivity (r; [S/m]) mea surement, and on ac voltage�current characteristics by permittivity (c [F/m]) measurement in the past years. However, that research con sidered only the case where the current flowing through the materials had reached the steady state and the electric field across thematerial was uniform and independent of time.During the last 20 years, because electric power apparatus has be· come more compact, and electronic devices have become much smaller, the insulating materials used are highly stressed to > 1 MV I cm, which is near the breakdown strength of the insulating materials. Under such high electric field application, electric charges may be injected fromelec trodes or be dissociated from impurities that occur in the material. These electric charges accumulated in the insulating material distort the orig· inal internal electric field distribution. The process may cause the insu lating material to degrade and som...

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“…In the following, we will discuss briefly how such an optical phase retardation distribution is pro duced when light is passing through a dielectric material. 3.1 .1…”

Section: Fundamentalsmentioning

confidence: 98%

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Takada¹

1999

IEEE Trans. Dielect. Electr. Insul.

197

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“…In this case the sensors have different wavelengths [37], or spatial periods which affects the sensitivity to material properties further away from the plane of the electrodes. This design has been used extensively for determining permittivity profiles normal to the surface of the electrodes [19,31,[38][39][40]. Care should be used in estimating material properties far away from the sensor.…”

Section: Introduction To Dielectrometrymentioning

confidence: 99%

Dielectrometry Measurements of Moisture Diffusion and Temperature Dynamics in Oil Impregnated Paper Insulated Electric Power Cables

Thomas

Zahn

2008

Conference Record of the 2008 IEEE International Symposium on Electrical Insulation

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Paper insulated lead covered (PILC) cables have played an important role in underground power distribution for a hundred years. Replacing aged PILC before failure is critical to managing power distribution. Three prominent failure mechanisms accelerate cable aging: temperature stresses, moisture ingress, and partial discharge. The research focuses on the effect of temperature and moisture on the effective (complex) permittivity of the cable insulation. Measurements are performed using cylindrical dielectrometry sensors designed to be wrapped around the cable. The lead sheath of the cable is removed so that the sensors can be placed directly in contact with the insulation. From the measurements, the electrical properties of the material as a function of temperature and transient moisture diffusion are found.A theoretical treatment of the interdigital dielectrometry sensors with a cylindrical geometry is presented. Two classes of the geometry are studied. The φ periodic sensor geometry has electrodes aligned with the cylindrical axis and periodic around the circumference. The z periodic sensor geometry has the electrodes forming rings around the cylinder that are periodic along the cylindrical axis. The material is modeled by concentric rings of homogeneous materials. The electric field solution consists of an infinite summation of Fourier series terms. In finding the field solution and as a consequence of it, the potential, electric field lines, and the impedance between the driving and sensing electrodes are found. A generalized solution to the planar dielectrometry sensor topology is also presented. This solution allows for an arbitrary placement and excitation of electrodes, providing the analytical tools for a new generation of sensors.Dielectrometry sensors for use in φ and z periodic geometries are designed and manufactured on a 4 mil PTFE substrate. An experimental setup is designed and built to provide a temperature and humidity controlled environment for measurements. Special clamping mechanisms are used to secure the sensor to the sample. Custom built hardware is used to excite the sensor at frequencies ranging from 0.005 Hz to 10,000 Hz (over six decades), measure and record the response, and deliver it to a computer for storage and analysis.Steady state measurements are performed at temperatures ranging from room temperature to 100• C. Plastics, woods, and the PILC cable samples are measured. Using the theoretical model, the effective permittivity is estimated from the measurements. An Arrhenius temperature dependence is observed for several materials including the PILC cables. We characterize the temperature dependence of these materials by a master curve and activation energy. Together they give a complete description of the effective permittivity's frequency and temperature dependence.Transient measurements of moisture diffusion are made at constant temperatures for several 4 materials. For some experiments the boundary conditions limit the diffusion of moisture to one direction. When the z...

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“…8,9 The phase shift u is distinct and the Kerr electro-optic method is proved to have suitable performance in the measurement of the electrical field and space charge distributions under HV for the liquid dielectrics with high Kerr constant such as propylene carbonate (Kerr constant B $ 3 Â 10 À12 ). 10,11 However, the phase shift of low Kerr constant transformer oil (B $ 3 Â 10 À15 ) is small and difficult to detect.…”

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confidence: 99%

Electric field and space charge distribution measurement in transformer oil struck by impulsive high voltage

Sima

Guo

Yang

et al. 2015

Applied Physics Letters

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Transformer oil is widely used in power systems because of its excellent insulation properties. The accurate measurement of electric field and space charge distribution in transformer oil under high voltage impulse has important theoretical and practical significance, but still remains challenging to date because of its low Kerr constant. In this study, the continuous electric field and space charge distribution over time between parallel-plate electrodes in high-voltage pulsed transformer oil based on the Kerr effect is directly measured using a linear array photoelectrical detector. Experimental results demonstrate the applicability and reliability of this method. This study provides a feasible approach to further study the space charge effects and breakdown mechanisms in transformer oil.

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Optical, electrical and electromechanical measurement methodologies of field, charge and polarization in dielectrics

Cited by 40 publications

References 42 publications

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Acoustic and optical methods for measuring electric charge distributions in dielectrics

Dielectrometry Measurements of Moisture Diffusion and Temperature Dynamics in Oil Impregnated Paper Insulated Electric Power Cables

Electric field and space charge distribution measurement in transformer oil struck by impulsive high voltage

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