Investigation of the flashover of a FRP hot stick while in use for live line work at 500 kV
TL;DR: In this paper, the authors describe the live line work which was being done, the weather and the condition of the hot stick, and a series of tests were made to investigate factors which may have contributed to the flashover.
Abstract: In October 1997 Manitoba Hydro experienced the flashover of a FRP hot stick during live line work at 500 kV AC. The paper describes the live line work which was being done, the weather and the condition of the hot stick. A series of tests were made to investigate factors which may have contributed to the flashover. The adequacy of available tests for FRP hot sticks is discussed. The corrective measures which have been taken prior to resuming work of this type are described.
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TL;DR: In this article, a three-dimensional electric field calculation model of a fiber glass-reinforced plastic (FRP) hot stick during live-line work based on the finite element method is proposed to account for the geometry of the Manitoba site incidents at 500-kV.
Abstract: The three-dimensional FEM electric field calculation model of a fiber glass-reinforced plastic (FRP) hot stick during live-line work, which was elaborated in a previous study, could well explain some features of the flashovers that occurred during a series of cold fog tests at CIGELE. These tests have achieved the most reliable reproduction of four separate FRP hot stick flashover incidents in Canada at a voltage stress of 105 kV/m at -1.04°C, Relative Humidity (RH) of 109 % with visible fog and 2.8 μg/cm 2 Equivalent Salt Deposit Density (ESDD). However, at the incident site, the geometry is different from that of the laboratory tests. In this paper, a three-dimensional electric field calculation model of a FRP hot stick during live-line work based on the finite element method is proposed to account for the geometry of the Manitoba site incidents at 500-kV. Moreover, the influence of the tower, phase conductors and shield wires on the potential and electric field distribution around an FRP hot stick during live-line work is studied.
20 citations
TL;DR: In this article, the potential and electric field distribution along a fiberglass reinforced plastic (FRP) hot stick under dry condition and non-uniform wetting were determined using a commercial software, COMSOL MultiphysicsTM.
Abstract: In February and December 2012, SaskPower experienced two flashovers of "clean" Fiberglass-Reinforced Plastic (FRP) hot stick during cold weather live-line work under steady-state 230 kV ac system conditions. As for SaskPower, Manitoba Hydro had two separate live-line tool flashover events, in 1997 and 2002. Clean-fog tests and non-uniform wetting tests at Hydro-Quebec Research Institute (IREQ), and cold-fog tests at Kinectrics and UQAC were carried out to explain these flashovers. The laboratory tests demonstrated that inadvertent contamination of clean tools at a very light level () of Equivalent Salt Deposit Density (ESDD) likely reduced voltage withstand capability of FRP hot sticks, particularly under freezing conditions. The flashover mechanism was identified when surfaces become fully wetted by the environment or surrounding fog. However, the source of moisture in field flashovers well below 0°C, i.e. as low as -19°C, was not identified. This study is based on laboratory tests and on using available pollution flashover models to explain the results. In this paper, the main objective is to determine the potential and electric field distribution along a FRP hot stick under dry condition and non-uniform wetting. A commercial software, COMSOL MultiphysicsTM, based on the finite element method (FEM), was used for the three-dimensional modeling and simulations. The results obtained will be useful to improve knowledge on the determination of discharge initiation conditions based on electric field distributions along a FRP hot stick.
16 citations
Cites background or methods from "Investigation of the flashover of a..."
...Following the flashover, a series of tests was carried out on the accident and link sticks at Manitoba Hydro [4], including wet high-potential and watts-loss tests based on IEEE Std....
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...The line is conducted with triplex 1272 kcmil 54/1 ACSR Pheasant with subconductor diameter and spacing of 35 mm and 457 mm, respectively [4, 12]....
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...hydrophobicity) of the hot-stick surface [4]....
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...Therefore, the following corrective measures were introduced to improve FRP maintenance and testing procedures at Manitoba Hydro [4, 12] and the program resumed in 1998....
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...The accident sequence and its details are provided in [4]....
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24 Nov 2003
TL;DR: In this paper, a FRP hot stick was found to flash over during live line work at 550 kVac in 2002 and a second flashover occurred during live-line work at 650 kVAC in 2002, both occurred during work from the tower on "v" suspension insulators.
Abstract: In 1997 a FRP hot stick flashed over during live line work at 550 kVac. A rigorous maintenance program was instituted and all FRP hot sticks used in live line work must now withstand an annual dielectric test at 105 kVdc per 305 mm with the surface wet consistent with IEEE Std 978. More frequent electrical tests are made using a hand held tester and limits have been set for the hydrophobicity of the surface. In spite of these measures a second flashover a FRP hot stick occurred during live line work at 550 kVac in 2002. Both flashovers occurred during work from the tower on "v" suspension insulators, the first at a temperature near the freezing point and the second at a temperature well below freezing. In both cases the wind was blowing from the conductor to the worker. Our investigation is trying to establish an adequate explanation for these events as well as corrective measures. The work to date is summarized in this paper. Industry standards for limits of approach are based on the switching surge withstand of air gaps and should not be equated to the minimum safe leakage distance of FRP hot sticks.
16 citations
19 Sep 2004
TL;DR: In spite of improvements in the maintenance and testing of the hot sticks, a second flashover occurred during live line work at 550 kV AC in 2002 and a low level of surface pollution is believed to have been the cause of the more recent flashover as mentioned in this paper.
Abstract: In 1997 a FRP hot stick flashed over during live line work at 550 kV AC. In spite of improvements in the maintenance and testing of the hot sticks, a second flashover occurred during similar work in 2002. A low level of surface pollution is believed to have been the cause of the more recent flashover. Laboratory tests have shown that the leakage distance of the FRP hot stick needs to be substantially greater than the minimum air gap approach distance.
14 citations
Abstract: A coupled computational fluid dynamics (CFD) and heat-transfer model for an ice-covered fiberglass-reinforced plastic (FRP) hot stick, elaborated in a previous study, could well explain why the flow of partial-discharge current could be sufficient to raise the temperature of an iced pollution layer just below freezing, where the cold-fog flashover mechanism prevails. However, the ice-covered hot stick was modeled as a solid “ice rod” having an equivalent cross section of ice, meaning that the exposed ice surface is smaller in the model compared to reality. In addition, the simulations were performed for a relatively low wind speed of 1 m/s, while average wind speeds of 6.1–14.4 m/s were reported for the two Manitoba flashovers. Both of these problems are addressed in this paper to deal with the site incident conditions. The ice cover is considered as a thin layer having a thickness of 1 mm on the FRP hot stick. The effects of wind speeds of 0.1–15 m/s and wind direction as parallel and perpendicular to the ice-covered FRP hot stick are studied. This paper also presents experimental investigations on the most reliable reproduction of four separate FRP hot stick flashover incidents in Canada achieved at CIGELE laboratories.
13 citations
Cites background from "Investigation of the flashover of a..."
...For the 1997 flashover in Manitoba, the ambient temperature, relative humidity, average wind speed, and peak wind speed (gusts) recorded at the Winnipeg Airport, about 44 km WNW of the accident site at the time of the accident were 1 C, 57%, 14.4 m/s, and 21.1 m/s, respectively [7]....
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...For the 2002 flashover in Manitoba, the aforementioned values were C, 46%, 6.1 m/s, and 7.78 m/s, respectively, measured at the work site at ground level [4], [7]....
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...In addition, simulations were performed for a relatively low wind speed of 1 m/s in [9] while average wind speeds of 6.1–14.4 m/s were reported for the two flashovers that occurred in Manitoba....
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...• For the 2002 flashover in Manitoba, the average wind speed was 6.1 m/s. Based on Fig....
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...The findings of the paper could well justify the cold-fog flashover mechanism for two flashovers which occurred on FRP live-line tools at temperatures of C and C in Manitoba and Saskatchewan....
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References
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TL;DR: In this article, the electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination (C), ice (I), fog (F) and an ambient temperature that rises through 0 C (T{sub 0{degree}}).
Abstract: The electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination (C), ice (I), fog (F) and an ambient temperature that rises through 0 C (T{sub 0{degree}}). Failures at operating voltage on 115-kV, 230-kV and 500-kV systems occur with increasing probability under these conditions. A new CFT{sub 0{degree}} or cold-fog test method has been developed to reproduce the flashovers at all three voltage levels. Three options are identified for improving CFT{sub 0{degree}} performance: use of semi-conductive glazes, substitution of silicone for porcelain and use of silicone coatings on existing porcelain insulators.
69 citations
TL;DR: In this paper, the electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination, ice, fog and an ambient temperature that rises through 0/spl deg/C (T(0/spl dec deg/c), and failure occurs with increasing probability under those conditions.
Abstract: The electrical performance of outdoor insulation degrades severely during combinations of factors that include surface contamination, ice, fog and an ambient temperature that rises through 0/spl deg/C (T(0/spl deg/)). Failures at operating voltage on 115 kV, 230 kV and 500 kV power systems occur with increasing probability under those conditions. A new CFT(0/spl deg/) or "cold-fog" test method has been developed to reproduce the flashovers at all three voltage levels. Three options are identified for improving CFT(0/spl deg/) performance: use of semi-conductive glazes; substitution of silicone for porcelain; and use of silicone coatings on existing porcelain insulators.
59 citations
TL;DR: In this paper, the authors performed staged line-to-ground fault tests on the longest section of single-phase switched line in the world, the 528 km Dorsey-Forbes 500 kV line.
Abstract: Staged line-to-ground fault tests were performed on the longest section of single-phase switched line in the world, the 528 km Dorsey-Forbes 500 kV line. Fault location and line loading conditions were varied for the nine fault tests applied and measurements were made of the primary and secondary arc currents and the arc recovery voltage. Arc extinction occurred rapidly with no restrikes during all of the tests. Secondary arc extinction occurred less than 50 ms after the beginning of the open phase deadtime. The rennants of the direct current offset in the fault current had a significant effect in delaying the secondary arc extinction.
35 citations
TL;DR: The results of three years of experimental and theoretical research on transmission-line radio noise at Project EHV are presented in this article, where computer programs were developed to process the data on a statistical basis, and as output provide both histograms and regression analyses for four test configurations operated at the 500-and 700-kV levels.
Abstract: The results of three years of experimental and theoretical research on transmission-line radio noise at Project EHV are presented Computer programs were developed to process the data on a statistical basis, and as output provide both histograms and regression analyses for four test configurations operated at the 500-and 700-kV levels Fair weather radio-noise levels were found to be significantly affected by relative humidity, relative air density, and absolute value of wind velocity, and these relationships are discussed Wet-weather effects are presented and discussed Both fair-weather and wet-weather experimental results are incorporated in a theoretical analysis of transmission-line radio noise resulting in a procedure which enables the transmission-line designer to predict, in advance of construction, average fair-weather and wet-weather radio-noise profiles for EHV transmission lines
16 citations
TL;DR: In this article, a bundle of 4 subconductors 2-in (5.08 cm) in diameter was tested on the Project UHV single-phase test line.
Abstract: A bundle of 4 subconductors 2-in (5.08 cm) in diameter was tested on the Project UHV single-phase test line. Radio noise, corona loss, audible noise, electrostatic field effects were continuously measured in order to investigate the effects of weather variables. Translation of the results to a 1000-kV, 3-phase line shows that audible noise will be the main obstacle to the use of this bundle.
13 citations