Flashover process and frequency analysis of the leakage current on insulator model under non-uniform pollution conditions (original) (raw)
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2010 10th IEEE International Conference on Solid Dielectrics, 2010
In this report, we have examined the impact of pollution severity on the dielectric performance of an insulating plane model which reproduces the 1512 L outdoor insulator. This insulator is largely used by the Algerian company of Gas and Electric power (SONELGAZ). These investigations were carried out using different conductivities composed of distilled water and NaCl for the insulator surface contamination. The aim of this study is to control the pollution severity in order to predict the imminent moment of insulator flashover. In order to monitor performance of the outdoor insulator, the continuous wavelet transform (CWT) is proposed as a new technique by using the scalogram analysis. The CWT is applied only on voltage waveforms during electric discharges occurrence on the polluted insulator surface. This technique examines the fractal nature of the applied voltage waveform which is distorted by electric discharges. These discharges cause important voltage drops. Obtained results with this method establish clearly the pollution severity deposited on the insulating surface and show the critical situation by which the insulator flashover can occur for low applied voltage levels. The red color appearing in the scalogram shows that electric discharges occur on the polluted surface. This color reaches low scales indicating that the frequency occurrence of electric discharges increases when the pollution level is critical.
2010 Annual Report Conference on Electrical Insulation and Dielectic Phenomena, 2010
In this paper, experiments are conducted in nonuniform contaminated conditions under 50 Hz applied voltage on a plane insulator model. This insulator simulates the 1512 L outdoor insulator which is largely used by the Algerian Company of Gas and Electric Power (SONELGAZ). The insulating model surface is contaminated with a conducting solution composed of distilled water and NaCl. The mixed solution has a conductivity of 1.2 mS/cm. The insulator surface is polluted by spraying the salt solution on the insulating region near the high voltage electrode.
The Severity of Polluted Insulator Surface Based on the Leakage Current Harmonic Measurements
Atlantis Highlights in Engineering, 2021
One of the important components in the high voltage overhead lines placed on the transmission tower is an insulator. Insulators that are installed outdoor will be exposed to the environment directly. Due to environmental conditions and pollutants attached to the surface, leakage currents can flow on the surface of the insulator. Large leakage currents can damage the surface of the insulator and cause losses in the form of heat and even cause flashover. This paper provides an alternative way to prevent early flashover by detecting the severity of the insulator surface based on harmonic measurements of leakage currents. Insulator performance mainly depends on the conductivity of the surface layer being polluted or by generating pollutants via the equivalent salt deposit density (ESDD). The leakage currents were evaluated at different ESDD levels as deposits of very light, light, moderate, and heavy NaCl salt pollution on a 20 kV outdoor polymer insulators. From the experiments, it can be concluded that: i. The leakage current that occurs when the surface of the insulator is very lightly polluted has an unsymmetrical waveform that is distorted and leads to a positive with a large THD; ii. The magnitude of the leakage current with the surface of the insulator is polluted, which leads to greater weight, but the harmonic distortion and THD are getting smaller with the waveform of the leakage current signal leading to a sinusoidal waveform.
IET Science, Measurement & Technology, 2011
This study refers to the laboratory tests that have been conducted under 50 Hz applied voltage on a polluted plane model simulating the 1512 l outdoor insulator largely used by the Algerian Company of Gas and Electric Power (SONELGAZ). They were carried out in order to identify the pollution level of the insulator surface, first by measuring the leakage current (LC) waveforms (i), and then by measuring the voltage waveforms (ii). (i) The evaporation of the electrolytic solution has especially been taken into account when electric discharges appeared on the contaminated insulator surface by performing a spectral analysis of LC waveforms. This has been done with the Welch periodogram in order to understand the contribution of LC frequency harmonics in drying the wetted layer depending on the pollution level of the insulator surface. (ii) As for the continuous wavelet transform, it has been used for analysing locally the voltage waveform, to understand the effects of different pollution levels on voltage drops, and ultimately to establish a visual diagnostic tool for monitoring the pollution level and for preventing the breakdown flashover.
Melecon 2010 - 2010 15th IEEE Mediterranean Electrotechnical Conference, 2010
This work is devoted to study the dielectric performances of a plane model wetted and contaminated by salt solutions having different conductivities. This insulator model simulates the 1512 L outdoor insulator which is greatly used by the Algerian Company of Gas and Electric Power (SONELGAZ). In this paper, we present signal processing results obtained through leakage current waveforms in order to predict the insulator flashover. These investigations were achieved after calculations operated on the leakage current energy by using the Welch frequency spectrum analysis. This frequency representation is performed on leakage current waveforms during the electric discharges activity appearing on the polluted plane surface. Reported results showed that the occurrence of electric discharges induced a progressive evaporation of the electrolytic solution and that this evaporation became stronger with the increase of pollution level.
Estimation of the Insulator Pollution Level Based on Frequency Characteristics of Leakage Current
CIGRE, 2015
One of the major problems in electric power transmission and distribution systems is the flashover caused by polluted insulators. This type of flashover is known as temporary fault that can turn into a permanent fault, causing sustained interruption [1]. Cost of power interruptions is highly significant for consumers and utility companies. For example, U.S. electric power interruptions, cost $135 billion per year [2]. Polluted insulators also contribute to the leakage current in a transmission line system. The dissipation of power due to leakage current is significant. The leakage current increases with pollution conductivity, and result in rapid extension of partial arcs [3, 4]. It is important to evaluate the contamination level of energized insulators to prevent unexpected pollution flashover and improve the reliability of the system. When the pollution level of in-service insulators are identified, the appropriate decision can be made about period of washing the insulators. In this study, a leakage current waveform characteristics is used in order to predict the severity of the contamination on the surface of insulators. The phase angle difference, total harmonic distortion (THD), and rate of rise of THD are the leakage current characteristics used for monitoring the pollution level. The values of the phase angle difference () between applied voltage and the fundamental frequency of the leakage current are computed while the pollution conductivity increases. When the pollution conductivity is low, the leakage current is capacitive. On the other hand, the leakage current becomes resistive when the pollution conductivity is high enough. The total harmonic distortion (THD) of leakage current is used for detection of contamination severity. The high frequency components of the leakage current increase with pollution conductivity and affect the THD level. Furthermore, the harmonic level variation of the leakage current over time results in THD variation. The rate of rise of THD (RRTHD) is introduced as an effective parameter to find the pollution level. These details provide a good correlation between the state of pollution and the leakage current. Therefore, phase angle difference (), THD, and RRTHD are used as the characteristic parameters of leakage current in order to find the contamination level.
2000
In this report, we have examined the influence of a discontinuous pollution layer width on the behavior of a laboratory plan model on which we reproduce the surface state of the 1512L insulator greatly used in algerian desert areas. The investigations were carried out by analyzing the leakage current magnitude, the phase angle current-voltage, the flashover process and leakage current frequency characteristics. Because the recorded leakage current waveforms include too many distortions, we have elaborated a numerical tool treating the leakage current signal allowing to determine its frequency spectra using the Discreet Fourier Transformed. The phase angle is determined from voltage and current phase spectra or also from the angles of their fundamentals.
Flashover on polluted insulator is a major problem for the safe operation of transmission lines and the design of external insulation. It initiates when the current flows through the conductive pollution layer on the surface of an insulator and create dry bands are created. The performance of insulators under polluted conditions is an important factor in the design and dimensioning of insulators in power transmission lines. Therefore, many researchers have studied the modeling of polluted insulators and predicting the flashover voltage, e.g.
Flashover of discontinuous pollution layer on HV insulators
IEEE Transactions on Dielectrics and Electrical Insulation, 1999
This paper deals with discontinuous pollution layers deposited on the insulator surface. TWO zones are known to form: a clean (dry) zone and a polluted (wetted) zone. The influence of the length and position of the dry zone on the leakage current and the arc length are investigated. These were made on a plane experimental model under ac voltage. Two configurations were studied: pollution deposited near the HV electrode, and pollution deposited near the ground electrode. This study was made using pollution layers with different conductivities. Based on the experimental results, a theoretical model allowing us to calculaie the gap impedance, the transferred (gap) voltage and the leakage current was established. This model enables to predict the pollution severity based on the sample's equivalent impedance.
IEEE Access, 2021
This work aimed to study the influence of contamination profiles and humidity on flashover electrical characteristics of polluted insulators. Firstly, the flashover tests on cap and pin glass insulators under four pollution levels represented by salinity were conducted. Eight artificial contamination profiles based on the solid layer method have been modeled for the selected insulators. The numerical analysis has been used to determine the insulator electrical characteristics such as potential, electric field, and power dissipation under proposed contamination profiles using finite element methods (FEM). Next, the power dissipation has been simulated with consideration of thermal stress propagation in locations with high power. Finally, flashover voltage gradient tests have been conducted under various humidity and contamination profiles. The values of the flashover voltage gradient due to pollution were determined as the percentage of the value of the flashover voltage gradient in the clean condition which was identified as the reference point. The numerical model indicated that the initiation of arc generally occurs at area in which the electric field and power dissipation is maximum. It was also observed from experimental results that the flashover voltage gradient under different contamination profiles has different values depends on the location and dimension of the pollution region. INDEX TERMS Polluted insulators, contamination profiles, flashover voltage gradient, numerical model, finite element method (FEM), power dissipation.