In-Situ Monitoring of Leakage Current on Composite and Glass Insulators of the Cahora Bassa HVDC Transmission Line

Roman, M.; Zyl, Robert Van; Parus, Nishanth; Mahatho, Nishal

doi:10.23919/saiee.2019.8643145

Cited by 8 publications

(8 citation statements)

References 17 publications

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“…Notice that the leakage currents measured here are well above those reported by Meyer et al [12] and Roman et al [14]. This is because these insulators are polluted not only by NaCl, which is soluble and susceptible to humidity, but also by non-soluble iron oxides, such as Fe 2 O 3 , which are conductive even without humidity.…”

Section: Field Resultssupporting

confidence: 79%

“…Although the humidity rises to almost 90%, no increase in leakage current was observed, confirming that in dry conditions, no LC occurs. Roman et al [14] concluded in their work that the LC increases from 0.01 mA to 0.08 mA when the humidity rises to up to 90% and the temperature drops to about 5 °C. By inputting these weather conditions in Equation ( 1), we find a dew point of 3 °C, which is below the local temperature; therefore, no humidity would accumulate on the insulator surface.…”

Section: Field Resultsmentioning

confidence: 97%

“…More recently, Roman et al [14], when correlating the LC with temperature, rain, and humidity, concluded that LC increases when the humidity rises to 90% and the temperature drops to about 5 • C.…”

Section: On Measuring Leakage Currents On Insulatorsmentioning

confidence: 99%

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Optical Sensor for Monitoring Leakage Current and Weather Conditions in a 500-kV Transmission Line

Werneck

Pinto

Bellini

et al. 2022

Sensors

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The leakage current (LC) caused by the surface contamination of insulators, together with environmental variables, is one of the most basic online monitoring parameters for insulator status. However, the impact of weather conditions such as temperature, air humidity, and dew point on the LC has not been deeply studied until now. In this paper, based on meteorological data obtained online and LC obtained with an optical fiber sensor, installed in 500-kV insulator strings of a transmission line, the impact of weather conditions was studied. Results indicate that the LCs follow a specific pattern, according to weather conditions. The system has been continuously monitoring LC, humidity, temperature, and dew point uninterrupted for three years, sending the acquired data to a web page; therefore, it has been demonstrated to be robust, reliable, and repetitive. The sensor features the broadband response and acquisition capabilities of partial discharge pulses in high-voltage insulators, allowing the detection of high-frequency pulses. When comparing the LC measured in this work with those from other works, our measurements are substantially higher; this is due to the type of pollution found in this specific situation, which includes iron oxide powder, producing a conductive layer over the insulator surface that, unlike sea salt, does not depend on humidity to conduct an LC. One of the conclusions reached in this work is that partial discharge surges are caused when the local temperature reaches the dew point and not simply from the presence of high humidity, as stated in many works dealing with LCs. The monitored LC can be used as an indicative parameter of a possible flashover, enabling the proper planning of insulator predictive maintenance, either by jet-washing the surface or even changing the insulators when they are damaged.

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Section: Field Resultssupporting

confidence: 79%

Section: Field Resultsmentioning

confidence: 97%

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Optical Sensor for Monitoring Leakage Current and Weather Conditions in a 500-kV Transmission Line

Werneck

Pinto

Bellini

et al. 2022

Sensors

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“…Consequently, the increase in the temperature caused a decrease in the humidity, as well as in the leakage current. This result was therefore in line with [7][8][9]12]. Finally, Fig.…”

Section: Correlation On the Environmental Parameterssupporting

confidence: 87%

The Evaluation of Daily Comparative Leakage Currents on Porcelain and Silicone Rubber Insulators Under Natural Environmental Conditions

2021

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In this research, the leakage current (LC) and applied voltage waveforms on samples of installed outdoor porcelain and silicone rubber (SIR) insulators were measured by using a storage digital oscilloscope concurrent with humidity, temperature, and illuminance measurements. Essentially, the measurements were conducted daily, every three hours, for thirty days, and the data were analyzed using exponential regressions, box plots, and correlation coefficients. The porcelain and SIR insulator leakage currents varied from 23.7 A to 28.8 A and 8.4 A to 10.35 A for median values, respectively, while for outlier excluded values, they varied from 20.3 A to 40.0 A and 5.1 A to 17.1 A, respectively. Both leakage currents slightly increased as the exposure duration of the insulator rose, while the ratio decreased very slightly. Additionally, the leakage currents decreased moderately and slightly as the temperature and illuminance increased, respectively. However, the parabolic leakage currents increased as the humidity rose, especially at high humidity. Therefore, the porcelain insulator was more susceptible than the daily SIR, while the SIR insulator was more highly influenced by aging of the exposure duration. The rainy condition contributed to the highest leakage currents on both insulators, whereas the drizzle condition contributed to the highest leakage current on the SIR insulator. The total harmonic distortion (THD) and phase angle of the porcelain insulator leakage currents experienced differences of 5.8% and 7.8 degrees in the minimum and maximum humidity, respectively, but both quantities were less for the SIR insulator. INDEX TERMS humidity, leakage current, porcelain, silicone rubber I. INTRODUCTION High voltage outdoor insulators have an important role in electrical power transmission and distribution systems, including operational reliability, safety, and efficiency [1]. However, their functions are mostly influenced by environmental conditions [2-3]. Common insulator materials include glass and porcelain, which are ceramic materials that have been used for hundreds of years. Moreover, composite and cast cycloaliphatic epoxy resin (epoxy resin, ER), as a polymeric category, has been used in the last few decades [3-4]. These insulators have sheds for reducing the electric field stress and tolerating the accumulation of pollution [5]. Currently, research conducted on insulator leakage currents based on daily time functions is limited. Vosloo et al. [6] illustrated the average peak leakage currents on some insulators, and Roman et al. [7] monitored the insitu dc leakage current magnitudes, namely, rain, humidity, and temperature, on composite and glass insulators. According to Castillo-Sierra et al. [8], the ceramic insulator leakage currents were measured using a clamp meter, as were the temperature and humidity, followed by a regression analysis. Further research by Vosloo and Holtzhausen [9] showed that the peak leakage current of porcelain insulators, including precipitation, relative humidity (RH), ul...

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“…When applying a 19 kV voltage in lab tests, an average leakage current of about 6.5 µA was obtained, before the premature aging process of the silicone composite insulator tested [36], which is similar to that obtained for insulator 7 in table 4. Roman et al measured the leakage current in in-situ silicon composite insulators in a high-voltage direct current (HVDC) transmission line (400-500 kV) and obtained long-term values ranging from 10 to 60 µA [37]. The leakage current variability obtained in these studies may be associated with different test conditions, e.g., different applied voltages.…”

Section: Discussionmentioning

confidence: 99%

Novel technique for estimating pollution-associated leakage current in high-voltage insulators based on adaptive filtering in long-term recording

Bueno-Barrachina

Peñuelas

Ye-Lin

et al. 2021

Meas. Sci. Technol.

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Moist polluting substances on high-voltage insulator surfaces can cause power-line failures by triggering electric arcs. There are at present no effective methods of measuring insulator pollution levels during normal operations. In this work, we attempt to estimate insulator pollution leakage current (PLC) as an indirect method of measuring deposits in a 30 month period of simultaneously recording leakage current and related environmental variables in substation insulators. We analyzed the relationship between raw leakage current and environmental variables. We canceled out the influence of relative humidity on leakage current by adaptive filtering and then obtained the PLC by filtering out the anomalous peaks in the recording. The proposed method considerably reduces the correlation between leakage current and relative humidity (0.826 vs 0.019). The resulting signal was only slightly correlated with other environmental variables (<0.03), suggesting that the relationships between leakage current and temperature, wind direction and speed are mainly attributable to their influence on relative humidity. The PLC presents a quasi-annual smooth fluctuation over time with a magnitude similar to those obtained in laboratory tests. This novel technique could be used to monitor insulator PLC in real time and thus improve power supply continuity and reduce maintenance costs.

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In-Situ Monitoring of Leakage Current on Composite and Glass Insulators of the Cahora Bassa HVDC Transmission Line

Cited by 8 publications

References 17 publications

Optical Sensor for Monitoring Leakage Current and Weather Conditions in a 500-kV Transmission Line

Optical Sensor for Monitoring Leakage Current and Weather Conditions in a 500-kV Transmission Line

The Evaluation of Daily Comparative Leakage Currents on Porcelain and Silicone Rubber Insulators Under Natural Environmental Conditions

Novel technique for estimating pollution-associated leakage current in high-voltage insulators based on adaptive filtering in long-term recording

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