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![Figure 1. Failed NCI by corona with visible tracking degradation [7]](profile/Lionel-Duvillaret/publication/235783428/figure/fig1/AS:299858788405248@1448503314031/Failed-NCI-by-corona-with-visible-tracking-degradation-7_Q320.jpg){kind=tracking}
Preliminary results based on experimental tests in laboratory and numerical investigation concerning the live-line detection of a conductive defect in HV composite insulator are depicted. The proposed method is based on E-field sensing using a non-invasive and compact pigtailed electro-optic (EO) single-ended probe. Measurements and numerical FEM m...
Citations
... Birlasekaran et al., [19] published papers stating that the Maxwell mesh creator generates a mesh based on predefined mesh operations. Several authors published the details about the mesh in [19][20][21][22][23][24]. A mesh operation establishes criteria for a designated set of objects, which the mesh maker uses to generate meshes that meet those criteria. ...
This research article examines the performance of insulators in high-voltage transmission systems, specifically focusing on their role in facilitating efficient power transfer along transmission lines. The study evaluates different types of insulators used in various geographical regions and assesses their withstand voltage characteristics. The research demonstrates that glass insulators outperform plastic and ceramic insulators in terms of electric field behavior. The study also investigates the behavior of AC-energized insulators in polluted and non-polluted conditions, providing insights for improving HVAC insulation design in polluted environments. The research recommends further experiments to examine insulator behavior under different applied voltage scenarios. Overall, the study emphasizes the importance of insulators in high-voltage transmission systems and provides valuable insights for developing advanced insulator technologies to enhance power transfer efficiency.
... Several standards have been established throughout the years to test the performances of these insulators when subjected to ageing (see, for example, [5]) However, the most critical aspect concerning the ageing of composite insulators is the live-line diagnosis of internal defects. Pre-existing defects, introduced, for example, during the manufacturing process between the rod and the sheath can promote partial discharge (PD) phenomena, leading to interface breakdown [6,7] with the consequent penetration of moisture and external pollutants. This can result in flashunders and the degradation of the rod, which eventually leads to its mechanical failure (e.g., brittle fracture of the FRP rod [8]). ...
... However, this technique is not very effective for those defects that cause small variations in temperature. Especially, thermography is not easily applicable in direct sunlight [7]. Another class of live-line diagnostics methods involves the measurement of the electric field profile near the insulator. ...
Composite insulators for high-voltage overhead lines have better performances and are lighter than traditional designs, especially in heavily polluted areas. However, since it is a relatively recent technology, reliable methods to perform live-line diagnostics are still under development, especially with regard to internal defects, which provide few external symptoms. Thermal cameras can be employed, but their use is not always straightforward as the sun radiation can hide the thermal footprint of internal degenerative effects. In this work, an optical E-field sensor has been used to diagnose the internal defects of a set of composite insulators (bandwidth 200 mHz–50 MHz, min. detectable E-field 100 V/m). Moreover, a modelling activity using finite elements has been carried out to identify the possible nature of the defects by comparing experimental E-field profiles with those simulated assuming a specific defect geometry. The results show that the sensor can detect the presence of an internal defect, since its presence distorts the E-field profile when compared to the profile of a sound insulator. Moreover, the measured E-field profiles are compatible with the corresponding simulated ones when a conductive defect is considered. However, it was observed that a defect whose conductivity is not at least two orders of magnitude greater than the conductivity of the surroundings remains undetected.
... Phase angle differences between the LC and applied voltage [6,7], LC harmonic components ratio [8,9], and leakage current amplitude [10][11][12] have been introduced in literature as main parameters for insulator condition diagnosis. Some practical methods and devices that have been presented in the literature are leakage current optical sampling [13], infrared thermal imaging [14], ultrasonic approach [15], acoustic fault detection technique [16], real-time fault detection in a microphone array [17]. ...
The leakage current characteristic monitoring of transmission line insulators is considered a worthy technique for insulator state prediction. In this paper, the harmonic analysis of leakage current signals has been performed to analyze the composite insulator condition. Experimental studies of asymmetrically aged, fully aged, and virgin insulators have been conducted. The effects of different aging types, pollution, and humidity on leakage current components, such as harmonics and the phase differences with the applied voltage, have been investigated. The analysis of the results shows that the effect of asymmetric aging on leakage current components is non‐linear, and this non‐linearity increases with the degree of pollution. Also, the type of insulator aging can be determined by the ratio of the third‐ and fifth‐order leakage current harmonics. For instance, the classification of insulators into virgin, asymmetrically aged, and fully aged can be determined by examining the corresponding value ranges of 0–0.5, 0.5–0.9, and > 0.9, respectively. Similarly, the phase difference values of < 15% and those > 15% indicate the clean and polluted operating conditions individually.
... And as the interface bonding fail, the homogeneous distribution of the electric field will be affected, hence speeding up the aging of the composite insulator core rod, as well as affecting the safe operation of the power transmission line. In addition to the above studies on interface defects affecting the in-service performance of composite insulators, investigators like Ramesh et al. [86], Wang et al. [87], and Volat et al. [88], also reported on the effect of internal defect/ partial discharge on the composite insulators applications. In their studies, corona discharge, dry band arcing, electrical treeing, and moisture ingress were deduced as the major causes of interfacial failure of glass fiber reinforced polymer insulator core rods [23,84,86,90]. ...
The adoption of composite insulators on high voltage power transmission lines remains the state of the art in electricity transmission/distribution, owing to their excellent electrical insulation, mechanical strength-to-weight ratio, anti-pollution flashover properties, ease of installation, and maintenance. However, long-term exposures of the composite insulators to mechanical and environmental stresses have been a major challenge to the power industries. Thus, the various fracture failure form of composite insulator core rods, such as interfacial bonding defects, brittle fractures, and decay-like fractures in association with these stresses was discussed in the review study. Furthermore, as the fracture failure of composite insulator rods affects the stable and safe operation of power lines, the authors, however, concluded the study with recommendations for better practice of power transmission lines using composite insulators. As such, the review will also give a reference for further research in this area.
... Electro-optic electric field (E-field) sensors are needed in many applications, such as antenna near-field characterization, 1 THz signal detection, 2 charged particle beam characterization in accelerators, 3 power grid monitoring, 4 and radio frequency (RF) ablation surgery. Electro-optic methods are among the best to measure Efields, which cause a change in the refractive index of an electro-optic crystal. ...
We present our results for using thin film lithium niobate devices for electric field sensing applications. Micro-ring modulator and Mach–Zehnder modulator-based electric field sensors are demonstrated. Micro-ring resonator sensors can be used for low frequency (up to several GHz) electric field sensing applications and achieve a high sensitivity of 80 mV/(m Hz 1/2 ) with a very compact size of 300 μm, as limited by the intensity and phase noise of the used distributed feedback laser. A measurement bandwidth of 2.5 GHz is measured for these sensors and is limited by the detector bandwidth. Alternatively, Mach–Zehnder modulators allow for perfect phase matching between the radio frequency signals and optical signals, and they can be used for electric field sensing up to several THz. A sensitivity of 2.2 V/(m Hz 1/2 ) was obtained using our Mach–Zehnder electric field sensor with an interaction length of 600 μm. The Mach–Zehnder sensor can sense electric fields with frequencies reaching 0.6 THz based on the calculated results.
... Some practical studies and prototyped devices have been presented in the literature, such as optical sampling of insulator LC [11], infrared thermal imaging [12], ultrasonic waves [13], acoustic fault diagnosis [14], and array signal processing techniques [15]. The main shortcoming of these techniques is the reliance on one indicator to identify the insulator condition. ...
... 2) Study Samples of Insulators: Experimental tests are conducted for various types of insulators. Fig. 4 shows the samples of the insulators that are tested under four pollution levels (light, medium, heavy, and very heavy), and three humidity levels (75%, 85%, and 95%) under three applied voltage levels (11,20, and 40 kV). All insulators are tested under clean condition at ambient humidity as well. ...
In this paper commonly-used overhead line insulators are experimentally studied to propose an intelligent diagnosis system (IDS) to correctly identify the insulator health condition in real-time. The proposed IDS is developed based on three diagnostic indicators, third to fifth harmonic ratio of the insulator’s leakage current (LC), cosine of the phase angle of the LC fundamental component, and the ratio of the maximum electric field stress to flashover electric field of the insulator. The proposed diagnostic approach can identify the normal, abnormal and critical conditions of an insulator based on the above-mentioned indicators. Leakage current and flashover voltage are experimentally measured for the studied insulators under various health conditions. Then, recorded data are analyzed to calculate the proposed indicators corresponding to each insulator state. Measured and calculated data are used to intelligently quantify threshold limits of each indicator based on visualization algorithm. In this algorithm, different classifiers are trained with experimental data. The decision tree, which provided the highest precision, is employed to determine reference boundaries of the three indicators for each health state of the insulator. Embedded sensors can measure and sample the LC and electric field stress of the insulator. Sampled data are transmitted to a central processing unit-based receiver via a radio communication channel to automate the identification of the insulator state in real-time.
... Detection of an insulator's state and prediction of flashover through analyzing the LC features were studied in [4][5][6][7][8][9][10]. Phase angle analysis of LC [4][5], ratio of LC harmonic components [6][7], frequency and peak of LC signal [8][9], and LC analysis of composite insulators [10][11] were the diagnostic indices for insulator's state monitoring found in the literature. ...
... The proposed decision tree (Fig. 6) is an outcome of the classification tree. 11 12 Therefore, the decision tree shown in Fig. 6b is implement in the ADD microprocessor for predicting the insulator's state based on the proposed classification of zones. The extracted decision tree is chosen for its 1) prediction accuracy, 2) interpretability and 3) ease of implementation. ...
An automatic detector device (ADD) has been designed and built for monitoring insulators state in overhead distribution lines. The prototyped device is suitable for measurement and analysis of the insulator leakage current (LC) on lines of distribution systems to diagnose insulator state. It operates based on two diagnostic indicators, third to fifth harmonic ratio (R3/5%) of the insulator's LC signal and cosine of phase angle difference (P.D%) between fundamental signals of the voltage and LC. Experimental data of the indicators in various conditions and various insulators are used to train a classifier for determining reference values of the indices for insulator state detection. The instrument has two physically separate parts: receiver and transmitter. They communicate via a radio communication channel which improves the effectiveness of incident management. The transmitter samples the LC signal of the target insulator using a ferrite core along with a series of active electronic filters.
... In the past, electrical defects in insulators were detected by the measurement of insulation resistance and the measurement of the electric field of the defective insulator with a normal one [8][9][10]. In order to locate mechanical defects, techniques such as ultrasonic wave method with ultrasonic probes, measurement of noise using contactless microphones and measurement of temperature by implementing infrared cameras were discussed in the literature [11][12][13][14]. ...
Insulators comprise only 5% of the capital cost of transmission lines; they are accountable for 70% of line interruptions and 50% of maintenance costs of transmission lines. Major transmission lines situated in different parts of the world were mostly all constructed 30 years ago. These lines have either completed or are approaching the active life at 30 years. It is not possible to replace all insulators at a time in any utility. From a standpoint of consistency, it is quite important to locate insulators that require replacement prior to the occurrence of failure. Recalling these issues, a replacement strategy was modeled on insulator samples, operated at 154 kV, mechanical and electrical rating (M+E) 25,000 lbs and within the 10–50 years (Y) age group, collected in bulk for laboratory evaluation, based on the probability of mechanical failure (P(F)) of insulators. For conducting these studies, tensile load test such as combined electrical and mechanical failing load test was performed on selected 30 new and aged porcelain insulator samples from bulk to access recent condition. It was observed that insulators under service for 50 years manifested a decrease of 89.3% in quality factor (K), as compared to insulators within 10 years of service. A micro-structural study was carried out by using an optical microscope (OM) and a scanning electron microscope (SEM) for the further confirmation of previous evaluations. P(F) was derived by implementing Weibull distribution on the experimental observations. It was observed that insulators with an age of 50 years depicted a 2.7% increase in P(F), as compared to insulators with an age of 10 years. This article discussed a strategy for accessing the recent condition of new, aged bulk samples and the criteria of the replacement of the insulator string based on P(F).
... Then when a THz wave is incident from a dielectric material to an ideal metal material, Z 2 in the first formula of (2) equals to 0 S/m. As the magnitude of the magnetic field cannot be infinite, E t equals to 0. Thus, (2) can be expressed as ...
After a long-term operation, defects may occur in the composite insulators and threat the safe operation of the power transmission. To secure the power transmission system, it would be beneficial to detect the defects in their initial stage. In this paper, the terahertz technique combined with a deconvolution method was proposed, and a terahertz time-domain spectroscopy system was built. To validate the method proposed, three types of defects, namely single air gap defect, inclusion defect, and double-layer air gap defect were artificially prepared and tested. According to the test results, it was found that, compared with the traditional terahertz method, the air gap size that could lead to pulse overlapping was reduced from 1.22 mm to 0.57 mm. After the deconvolution process, air gap defect as small as 0.173 mm could be distinguished due to the shape characteristics of unipolar pulse. It was also found that when the defect was damp, the obtained waveform near the defect became smooth. The results of the present study demonstrate that terahertz time-domain spectroscopy (THz-TDS), combined with the deconvolution method, can have high potential in the detection of defects in composite insulators.
... When the insulator has an electric fault or low level of insulation capacity, the axial and radial distributions along the insulator of the surrounding electric field produce distortion; the foregoing field condition is then detected and compared with that of the non-fault standard electric field. If no distinct difference is observed, then the insulator is judged normal; otherwise, it is deemed defective [4][5][6]. ...
More than 55% of porcelain insulators installed throughout Korea have exceeded their service life. Hence, utilities are extremely interested in determining the robustness of insulators in their systems. In this study, the identification of the peak ranges in the main natural modes by frequency response analysis, the principal component analysis (PCA) method by feature extraction in the time and frequency domains for the damage detection of porcelain insulators are investigated; among these, the PCA method, which utilizes frequency response data, is proposed for defect classification. The 67 porcelain insulators are secured as specimens from 154 kV transmission towers installed in various parts of Korea; their main materials are cristobalite and alumina. In these specimens, it is observed that the three types of damage, such as porcelain damage, cap damage, and internal damage, are those that are typically found in actual sites. Accordingly, the use of two eigenvectors (moments of real value and moments of imaginary value) considerably aids in the analysis of principal components. With the frequency response data, the material and damage types are found to be distinguishable. The classification accuracy is increased by including the third largest eigenvector (area of real value) in three-dimensional analysis. By employing frequency response data, the PCA method provides useful information for assessing the integrity of porcelain insulators; it may be used as basis for future machine learning applications.
