Electric Field Measurement Method Research Articles

A Novel Transient Electric Field Measurement for Low Kerr Constant Liquid Dielectrics Based on Concave Spherical Mirror Conjugate Structure

This article proposes a Kerr effect electric field measurement method based on a concave spherical mirror conjugate structure (CSM CS) for a transient electric field in low Kerr constant liquid dielectrics. The accuracy of transient electric field measurement can be greatly improved in a limited space by multiple small-angle reflections. To verify the effect of the proposed structure, the electric field distribution is measured in propylene carbonate (PC) with a high Kerr constant at a switching overvoltage. The measurement results show that the electric field error of a PC under an extremely low electric field is only about 2%. The novel structure improves the electric field measurement accuracy of a liquid with a high Kerr constant. Then, the whole device is applied to the transformer oil, and the accuracy of the measured electric field is also greatly improved. At the same electrode size, the sensitivity of measuring the electric field with the proposed structure is three times that without it. The analysis results show that the introduction of the proposed structure has little effect on the electric field measurement. The proposal and application of the proposed CSM CS further expand the electric field measurement range based on the Kerr effect and improves the electric field measurement accuracy.

Research on Electric Field Detection of Degraded Insulators Based on a Sensitive Detection Method under Complex Operating Conditions

Insulators are the basis of the stable operation of transmission lines, and it is particularly important to regularly detect the insulation performance of insulators. After several years of research, contactless space electric field detection technology for degraded insulators, based on an unmanned aerial vehicles (UAV) platform, has developed rapidly. However, the existing technology is only limited to the typical vertical/horizontal state research category and cannot apply to complex operating conditions such as attitude disturbance and path tilt. This paper builds a simulation model of insulators at a voltage level of 220 kV by COMSOL finite element software and analyzes the space electric field distribution characteristics of degraded insulators and the influence of different surface conditions, attitude disturbance, path tilt, etc., on the space electric field distribution of insulators. To reduce the error of UAV detection under complex operating conditions of insulators, a method for detecting the electric field of degraded insulators based on sensitive insulators is proposed and verified by experiments. According to the research results, surface conditions of insulators have little influence on their space electric field, while the attitude disturbance and path tilt of UAVs have a great influence on the electric field of insulators. Sensitive insulators at a level of voltage below 220 kV are generally located at the low-voltage end. The principles of sensitive insulators are combined with the space electric field measurement method to measure the space electric field distribution, thus effectively judging whether there are degraded insulators in the string. The method specified in the paper greatly improves the accuracy and detection efficiency of the contactless electric field detection of insulators, which is of great significance for the promotion of the electric field detection method of insulators in practical applications.

Detection of Escherichia Coli Bacteria by Using Image Processing Techniques

Recently, image processing has proven itself as a fast and reliable technique in research in medicine and biology. Bacterial colony separation is an important and time-consuming process in studies in the field of microbiology. Bacteria counting is usually carried out by the naked eye or even by Coulter counter machines, which are based on the rather expensive electric field measurement method. In this study, image-based enumeration of Escherichia Coli over the colony morphology in the petri dish was investigated. In the experimental study, 4 different bacteria from the Enterobacteriaceae family were planted on petri dishes containing Eosin-methylene blue agar (Merck, Darmstadt, Germany). Escherichia Coli colony characteristics were determined by digitizing planted bacterial petri images. For the study, counting was done with the interface developed in MATLAB R2013a. After the classification criteria were determined, the method was tested on new petri dishes and successful results were obtained.

Multi-Frequency Electric Field Measurement Method for Optical Under-Sampling System

This paper introduces an under-sampling E-field measurement system involving three femtosecond pulse lasers, which can be used to measure a multi-frequency electric field (E-field) in a wide frequency range. Optical under-sampling technology utilizes femtosecond laser pulses to sample the electrical signals and convert the high-frequency signal down to the first pulse repetition frequency (RPF) intervals for measurement, i.e., tens to hundreds of MHz. However, previous work rarely studied the measurement of multi-frequency signals. Therefore, in this work, we use three RPFs and propose the Remainder Matching (RM) method of three RPFs to eliminate false-alarm-triggered frequencies. Moreover, to solve the challenging problem of grouping the down-conversion components of each measured frequency, we suggest the Eigenvalue Matching of Remainder’s Difference (EMRD) method to obtain the correct group accurately. Hence, this work combines the RM and EMRD methods to improve the system’s measurement accuracy. To evaluate the suggested measurement technique, detailed theoretical analysis and simulation are performed to demonstrate the universality of our method that can effectively guide the design of E-field measuring systems using optical under-sampling technology. The proposed scheme manages an error rate less than 0.1% without any measurement error of the down-converted components when six frequencies exist simultaneously and is less than 5% when the measured frequency deviation is ±25kHz. Finally, the proposed system is challenged on noise perturbations, with the results demonstrating that the suggested combined RM and RDEM scheme attains an appealing performance.

Experimental research on the decay charateristics of GIS busbar residual voltage/charge

GIS is the significant equipment in UHV network. However, after the UHV GIS busbar switch is opened, there will be a higher residual voltage on the GIS busbar, which causes the basin insulator flashover during the commissioning of the substation, which seriously affects the insulation and safety performance of the power system. It is very necessary to study the residual voltage on the GIS busbar. Therefore, we established a set of the GIS busbar residual voltage measurement system. Based on electric field measurement method, the GIS busbar residual voltage is measured in sulfur hexafluoride gas. The decay characteristics of the GIS busbar residual voltage under different polarity, different amplitude voltage and different temperature are studied. Research shows that the GIS busbar residual decays exponentially, and the decay of residual voltage is closely related to amplitude, temperature; at 26 °C and 0.4 MPa SF6 gas, the decay time of the GIS busbar residual voltage is as long as 22 hours after applying +450kV DC voltage, and the decay time constant is about 104 s order of magnitude.

AC/DC hybrid electric field measurement method based on Pockels effect and electric field modulation.

The electromagnetic environment under transmission lines is a concern for high-voltage transmission. For transmission corridors in which alternating-current (AC) and direct-current (DC) transmission lines are on the same tower, the electromagnetic environment at ground level is complex because of the AC/DC hybrid electric field. Generally, different instruments are used for measuring AC and DC electric fields, making it difficult to measure such fields simultaneously. Thus, we propose a method for AC/DC hybrid electric field measurement based on the Pockels effect and electric field modulation. The principle of the measurement is discussed in detail. An experimental platform is set up to verify the feasibility and effectiveness of the proposed method and to calibrate the sensor. It shows that the sensor realizes simultaneous measurement of AC and DC electric field intensities as well as judgment of the polarity of the DC electric field. The measurable range is 1.05-150 kV/m (peak-to-peak value) for the AC electric field and 1.23-150 kV/m for the DC electric field with a maximum measurement error of less than 5%. The sensor has good repeatability, linearity, and low hysteresis, which can be used in power grids for AC/DC hybrid electric field measurements.

A NOVEL METHOD FOR MEASUREMENT OF ELECTRIC FIELD IN EMULATED HUMAN BODY TISSUE USING WIRE MESH SENSOR

Wire mesh sensor has been successfully fabricated and used for measurement of the electric field in emulated human body tissue. Measurement of electric field in human body tissue needs to be done, because the electric field is very useful for the treatment especially cancer treatment and also important for health. In this study, we propose a novel electric field measurement method by using wire mesh sensor (wms), that is all channels on the wire act as receivers, and each cross point of the wire are interconnected. While in existing wire mesh sensors, there are two perpendicular channels of transmitter and receiver, and each channel is unrelated, there is a distance between the two channels. At present, wire mesh sensors 3 × 3 and 8 × 8 were used to measure the value of electric field at each wire intersection point. The wire mesh sensor consists of copper wire in a cylindrical body model with diameter 14 [cm]. The emulated human body tissue were inserted in the wire mesh sensor. Furthermore, linear back propagation technique and bilinear interpolation used for image reconstruction of the electric field distribution. The result showed that the wire mesh sensor 8 × 8 has better resolution than wire mesh sensor 3 × 3. The characterisation of wire mesh sensor 8 × 8 for measurement of electric field in emulated human body tissue is obtained lower than measurement in the air with a ratio of 82%. Meanwhile, the wire mesh sensor 3 × 3 could be achieved at 61.8%. This study can be a new science in measuring electric field so that electric field-based treatment planning system can be more optimal.

An electric field measurement method based on electro-optical modulation for corona discharge in air.

To study corona discharge in air, it is important to measure the electric field in the discharge space, which is directly related to the corona discharge process. In this paper, we present a method for measuring the electric field with electro-optical modulation. This method uses space laser modulation based on Bi4Ge3O12 (BGO) crystals, and we suggest using the dual optical path difference method to improve the measurement performance. The measurement error is analyzed from theory, including the measurement error of a highly inhomogeneous electric field and the error due to theoretical approximation. In system calibration, the system noise and the dual optical path difference method were analyzed. The dynamic linear range is determined, and measurement effectiveness in the severely nonuniform electric field is verified by comparison with a finite element numerical simulation. We measured the electric field in Trichel pulses under negative dc voltage and found electric field pulses. These measurement results show that the characteristics of Trichel pulses are directly related to the electric field. Therefore, this method can provide strong support for the study of corona discharges.

Electric field measurements in a near atmospheric pressure nanosecond pulse discharge with picosecond electric field induced second harmonic generation

We present an optical electric field measurement method for use in high pressure plasma discharges. The method is based upon the field induced second harmonic generation technique and can be used for localized electric field measurements with sub-nanosecond resolution in any gaseous species. When an external electric field is present, a dipole is induced in the typically centrosymmetric medium, allowing for second harmonic generation with signal intensities which scale by the square of the electric field. Calibrations have been carried out in 100 Torr room air, and a minimum sensitivity of 450 V/cm is demonstrated. Measurements were performed with nanosecond or faster temporal resolution in a 100 Torr room air environment both with and without a plasma present. It was shown that with no plasma present, the field follows the applied voltage to gap ratio, as measured using the back current shunt method. When the electric field is strong enough to exceed the breakdown threshold, the measured field was shown to exceed the anticipated voltage to gap ratio which is taken as an indication of the ionization wave front as it sweeps through the plasma volume.

An Electroscope System Based on Electric Field Measurement Method for UHV Transmission Lines

The paper describes an electric field measurement method based electroscope system to check the electrification state of ultra-high voltage transmission lines, which is composed of three parts: 1) Measuring terminal; 2) Central sever; 3) GPRS and Internet network. The measuring terminal was used to measure the electric field and the location of the measuring points, then the measured data was sent to the central sever by GPRS and Internet network, and requested for an electricity state confirmation.When the sever received a request from a terminal, the electric fields and locations of the measuring points were obtained first, then according to the location of the measuring points, the server searches the corresponding objective transmission lines in the database and read their parameters. According to the parameters of the measuring points and transmission lines, a calculation would be carried out to confirm the electrification state of the transmission lines. For the confirmation calculation, equations for the electric field inverse problem of the transmission lines were set up first, then global regularization and damped Gauss Newton (DGN) method were used to solve the inverse problem.A 500kV double loops transmission line was taken as an example to verify the validity of this method. The electric field and location of 11 measuring points were measured by the measuring terminal firstly, and then sent to the central sever. Electrification state was confirmed by the central sever.

Inverse application of charge simulation method in detecting faulty ceramic insulators and processing influence from tower

Suspension insulators are widely used in power systems to provide electrical insulation and mechanical support for high-voltage (HV) transmission lines. To detect and replace the faulty insulators on power transmission lines is of great importance for the safe operation of the power system. A nontouch electric-field measurement method to detect faulty ceramic insulators is presented, which involves measuring the electric-field of measuring points in the vicinity of insulator strings and calculating the potential distribution along HV outdoor insulator strings. It also suggests a way to process the influence from the tower. The salient feature of this method is the significantly smaller number of measuring points and the greater distance between measuring points and insulator strings. Ceramic suspension insulators of 110-kV voltage ratings have been modeled under clean and dry surface conditions. Good agreement is obtained between the present calculations and the actual value, which demonstrates the practical viability of the technique

Experience with the detection of faulty composite insulators on high-voltage power lines by the electric field measurement method

Hydro-Quebec's experience with polymer insulators began in 1977. A sixteen km section of a 735 kV transmission line near Quebec City was then re-insulated with 282 composite insulators of three different makes in equal proportions. The objective was to study them under real service conditions in order to evaluate their performance and to assess the relative merits of each make. This experimentation was later extended to some other lines and/or voltage levels and has continued up to now. During all these years, various methods of testing composite insulators in-service have been experimented with and early in the 1990s, the first device developed at IREQ for the in-situ testing of porcelain insulators by the electric field method was modified and adapted for use on composite suspension insulators. This paper presents a few cases of insulators having a particularly dangerous type of failure mode and found on the lines by the use of the electric field method. Some background information on the detection of defects by this method is also given and some of the experiments done in the laboratory on composite insulators to define the limits of the method are described.

Study on Kerr electro-optic field measurement method for nonuniform three-dimensional electric field

The Kerr electro-optic method is a non-intrusive electric field measurement method. It can be widely applied to gas, liquid and solid materials, which are transparent to light and are electrically birefringent. But this method is not adequately developed for practical measurements because, so far, it can only measure up to two-dimensional electric fields. The measurement techniques using the Kerr effect for a nonuniform three-dimensional electric field are described by considering the effect of the electric field at each point along the laser beam and the effect of the observing (laser beam) direction on the apparent electric field.

Three-Dimensional Electric Field Vector Measurements in Nitrobenzene Using Kerr Effect

We have been investigating a nonuniform electric field measurement method in dielectric liquids using the Kerr electrooptic effect. Three-dimensional electric field vectors were measured as the first step in determining the three-dimensional nonuniform electric field distributions. The electric field vector to be measured was produced in a pair of inclined parallel-plane electrodes. Negative high-voltage pulses were applied to the electrode system. Nitrobenzene with large Kerr constant was used in the experiments. A He-Ne laser beam passed through nitrobenzene between the electrodes along two different orthogonal directions. The magnitude and the direction of the electric field vector were calculated from the light intensity measured by a photodiode. Maximum errors of measured electric field strength and direction were 9.3% and 4.3°, respectively.