Bird droppings flashover protection range calculation method based on grading ring path scanning

Abstract

The invention relates to a bird droppings flashover protection range calculation method based on grading ring path scanning. The method comprises the following steps: (1) building an ultrahigh-voltage power transmission line I-type suspension composite insulator string bird droppings flashover test platform; (2) bird droppings simulants with different lengths are hung below the cross arm, and a continuous boost test is carried out on the high-voltage end of the insulator; (3) calculating the average breakdown electric field intensity of the residual gap between the bird droppings simulant and the grading ring, and solving the maximum and minimum bird droppings flashover shortest residual air gap length according to the test standard deviation; (4) scanning along the contour track of the grading ring, drawing a bird droppings protection range, hanging a bird droppings simulant on a cross arm at the boundary of the protection range with 10-15% margin, and observing whether gap breakdown occurs so as to verify the effectiveness of the protection range; and finally, selecting an area without a breakdown phenomenon as a bird droppings protection range. The accuracy and scientificity of bird droppings flashover protection in the field of power transmission line operation and maintenance can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission line maintenance, and in particular to a method for calculating a guano flashover protection range based on voltage-equalizing ring path scanning. Background Art

[0002] Composite insulators are widely used in ultra-high voltage transmission lines. In transmission lines, grading rings are usually installed on composite insulators to improve the voltage distribution of the shed skirt on the high-voltage side of the insulator. In recent years, due to the introduction of environmental protection policies and the enhancement of people's environmental awareness, the number of birds along ultra-high voltage transmission lines has continued to increase, and transmission towers have become an ideal place for birds to nest and live. However, when nesting materials, bird droppings, etc. fall, it is very easy to cause the air gap between the high-voltage end of the transmission line and the grounding end of the tower to be insufficient to form a discharge channel, causing the line gap to break down and trip.

[0003] According to statistics from relevant departments of a western province, accidents caused by bird damage account for a very high proportion of local line failures, and the number of tripping caused by bird droppings has been increasing year by year, accounting for a considerable proportion of bird damage failures, which seriously threatens the safe operation of the regional power grid. Therefore, bird prevention work on ultra-high voltage transmission lines needs to be further optimized and improved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for calculating the guano flashover protection range based on voltage grading ring path scanning to improve the accuracy and scientificity of guano flashover protection in the field of power transmission line operation and maintenance.

[0005] In order to solve the above problems, the present invention provides a method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning, comprising the following steps:

[0006] ⑴Build a guano flashover test platform for type I suspension composite insulator strings on ultra-high voltage transmission lines;

[0007] (2) Hang bird droppings simulants of different lengths under the crossarm and conduct a continuous voltage increase test on the high-voltage end of the insulator;

[0008] ⑶ According to the recorded test results, summarize the breakdown field strength E of a single test t , calculate the average breakdown electric field strength E of the residual gap between the guano simulant and the grading ring avt , and the maximum and minimum guano flashover shortest remaining air gap length d is obtained from the test standard deviation σ max d min ;

[0009] (4) According to the shortest remaining air gap length for breakdown, scan along the contour trajectory of the pressure equalizing ring, draw the guano protection range, and hang guano simulant on the crossarm at the boundary of the protection range with a margin of 10% to 15%, and observe whether gap breakdown occurs to verify the effectiveness of the protection range; finally, select the area without breakdown as the guano protection range.

[0010] The different lengths of the guano simulant suspended in step (2) are determined by the following method: first, a guano simulation solution is prepared using kaolin, xanthan gum, and NaCl solids in a mass ratio of 5:3:3; then, the viscosity and conductivity of the solution are adjusted; and then, a cotton rope is placed in the guano simulation solution and fully soaked, and the soaked cotton rope is hung under the crossarm.

[0011] The continuous voltage boost test in step (2) refers to using a high voltage power supply to pressurize the high voltage side of the insulator, gradually increasing the voltage until the guano simulant is broken down or the operating phase voltage reaches 210 kV and the voltage withstand test is terminated for 1 minute.

[0012] The average breakdown electric field strength of the remaining gap in step (3) is determined by the following formula:

[0013] E t =U / d,

[0014] Where: E t is the breakdown field strength of a single test, kV / cm; U is the flashover voltage, kV; d is the shortest remaining air gap between the guano simulant and the grading ring, cm; E avt is the average breakdown electric field strength, kV / cm; N is the number of tests.

[0015] In step (3), the test standard deviation σ is calculated as follows:

[0016]

[0017] In the step (3), max =U N / [(1+σ)E avt ],d min =U N / [(1-σ)E avt ]; U N is the operating phase voltage, which is 210kV.

[0018] The track scanning in step (4) is performed as follows: using the shortest remaining air gap length d max d min Rotate along the surface structure path of the equalizing ring to obtain two guano protection ranges.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The present invention builds an experimental calculation simulation platform for type I suspension composite insulator strings of ultra-high voltage transmission lines, calculates the average breakdown field strength of guano flashovers occurring under actual operating conditions of type I insulator strings, and provides a theoretical basis for guano protection of type I insulator strings.

[0021] 2. The calculation method provided by the present invention fully considers the actual size structure of the type I insulator string of the transmission line, and in the simulation process, calculates the electric field of the three-dimensional space around the insulator and the shortest residual air gap between the end of the guano simulation and the high-voltage end, and proposes the guano flashover protection range of the type I insulator string of the transmission line tower.

[0022] 3. The present invention provides a basis for the arrangement of bird protection measures for transmission lines by calculating the guano flashover protection range, which can improve the accuracy and scientificity of guano flashover protection in the field of transmission line operation and maintenance, and has the characteristics of low operating difficulty and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0024] Figure 1 It is a flow chart of the present invention.

[0025] Figure 2 This is a diagram of the test arrangement in an embodiment of the present invention.

[0026] Figure 3 It is a flow chart of the scanning profile of the pressure equalizing ring in an embodiment of the present invention.

[0027] Figure 4 This is a flow chart of the scanning profile of the voltage-equalizing shielding ring in an embodiment of the present invention.

[0028] Figure 5 This is a top view of the guano protection range with a pressure equalizing ring and a pressure equalizing shielding ring installed in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention is based on a guano flashover test platform, takes into account the typical situation that guano short-circuits a crossarm and causes air gap breakdown, adopts a method of hanging cotton ropes of different lengths fully soaked in guano simulation solution on the crossarm to perform a guano flashover test, and calculates the breakdown electric field strength of the shortest remaining air gap between the guano simulant and the grading ring, thereby calculating the shortest breakdown distance of guano flashover when the average breakdown field strength obtained in the test is 1.1 times the voltage level of the phase voltage. Further, through this process, the scope of guano flashover protection of the type I suspension composite insulator string of the transmission line can be determined.

[0030] like Figure 1As shown, a method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning includes the following steps:

[0031] ⑴ Build a guano flashover test platform for Type I suspension composite insulator strings on ultra-high voltage transmission lines.

[0032] ⑵ Hang guano simulants of different lengths under the crossarm, with the intersection of the insulator centerline and the crossarm as the coordinate origin o, the straight line passing through the coordinate origin and parallel to the crossarm as the x-axis, the coordinate origin and the crossarm interface as the basis, the straight line passing through the coordinate origin and perpendicular to the x-axis as the y-axis, and the straight line passing through the origin and perpendicular to the xoy plane as the z-axis. Hang guano simulants of different lengths vertically at a distance of x=30cm from the coordinate origin, and the gap distance between the guano simulant and the equalizing ring on the same side is d. Then carry out a continuous voltage boost test on the high-voltage end of the insulator. The continuous voltage boost test refers to using a high-voltage power supply to pressurize the high-voltage side of the insulator, gradually increasing the voltage until the guano simulant is broken down or the operating phase voltage reaches 210kV and the voltage withstand test ends for 1 minute.

[0033] Wherein: the hanging of guano simulants of different lengths is determined by the following method: firstly, kaolin, xanthan gum and NaCl solid are used to prepare a guano simulation solution in a mass ratio of 5:3:3 (mass unit: g); then the viscosity and conductivity of the solution are adjusted; then, the cotton rope is placed in the guano simulation solution and fully soaked, and the soaked cotton rope is hung under the crossarm.

[0034] ⑶ According to the recorded test results, summarize the breakdown field strength E of a single test t , calculate the average breakdown electric field strength E of the residual gap between the guano simulant and the grading ring avt , and the maximum and minimum guano flashover shortest remaining air gap length d is obtained from the test standard deviation σ max ,d min .

[0035] The average breakdown electric field strength of the residual gap is determined by the following formula:

[0036] E t =U / d,

[0037] Where: E t is the breakdown field strength of a single test, kV / cm; U is the flashover voltage, kV; d is the shortest remaining air gap between the guano simulant and the grading ring, cm; E avt is the average breakdown electric field strength, kV / cm; N is the number of tests.

[0038] The test standard deviation σ is calculated as follows:

[0039]

[0040] d max =U N / [(1+σ)E avt ],d min =U N / [(1-σ)E avt ]; U N is the operating phase voltage, which is 210kV.

[0041] (4) According to the shortest remaining air gap length during breakdown, scan along the contour trajectory of the pressure equalizing ring. The trajectory scanning is performed in the following way: Use the shortest remaining air gap length d max ,d min Rotate along the surface structure path of the equalizing ring to obtain two guano protection ranges. Then draw the guano protection range, and hang guano simulants on the crossarms at the boundary of the protection range with a margin of 10% to 15%, and observe whether there is a gap breakdown to verify the effectiveness of the protection range; finally, select the area without breakdown as the guano protection range.

[0042] Example

[0043] The parameters of the type I insulator string and grading ring of the cathead tower of the 330kV ultra-high voltage transmission line in Zhangye, Gansu Province were selected. According to the actual shape and size of the type I insulator string and cathead tower, a guano flashover test platform was built. Figure 2 As shown. Among them: the experimental transformer outputs high voltage; the current limiting resistor limits the current to protect it; the voltage dividing capacitor is mainly used for voltage division; the weight plays a balancing and fixing role, and is used for the horizontal adjustment of the cross arm and insulator; the ultraviolet imager is used to observe the number of electric field photons; the camera is used to record the experimental process.

[0044] A simulated guano solution with a viscosity of 4000mpa·s and a conductivity of 18ms / cm was prepared with 20g kaolin, 13.2g xanthan gum, and 12.8g NaCl. The cotton rope was placed in the simulated guano solution and fully soaked before being hung 30cm away from the axis of the insulator, above the grading ring. The lengths of the simulated guano cotton ropes were selected to be 269.1, 277, and 284.9cm, respectively, and the shortest remaining air gaps from the grading ring were 56.9, 49, and 41.2cm, respectively. Each length was tested at least 6 times, and data with obvious errors were removed. Finally, the breakdown field strength E was obtained. t The average breakdown field strength is 3.14-3.59 kV / cm. avt is 3.38 kV / cm, and the test deviation σ is 14.31%, and then d min With d max 54.4cm and 72.4cm, and the anti-guano range of the pressure equalizing ring is drawn, such as Figure 3 Shown is a flow chart for scanning the bird droppings protection range.

[0045] In the present invention, a voltage-equalizing shielding ring can be installed at the same time as the voltage-equalizing ring, which plays a role in strengthening the shielding of electric field interference. The protection range test of the voltage-equalizing shielding ring is the same as that of the voltage-equalizing ring, and d min With d max Also 54.4cm and 72.4cm. When the pressure-equalizing shielding ring is installed, the bird droppings protection range scanning flow chart is as follows Figure 4 shown.

[0046] In such Figure 5 The figure shows the projection of the protection range with the added pressure equalizing ring and the pressure equalizing shielding ring. Hang the bird droppings simulant on the cross arm above the protection range boundary for observation. If there is no residual air gap breakdown, the protection range can be considered effective. Since the bird droppings protection range figure is an axisymmetric figure, it only needs to be verified on 1 / 4 of the figure (where positions 1-4 are d min The critical point on the protection range of the guano is d, position 5-8 max The critical point on the guano protection range is required, and positions 9-12 are the critical points for retaining the margin guano protection range). The results show that positions 1-4 will cause guano flashover, no flashover occurs at position 5, and 200-210kV flashover occurs at positions 6-8. Considering the influence of temperature and humidity, on-site wind deviation and electric field force, 11% margin protection is taken. There is no breakdown phenomenon at positions 9-12 at the boundary of the margin anti-guano range. Therefore, it can be considered that this range can basically protect against guano flashover.

Claims

1. A method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning, comprising the following steps: ⑴Build a guano flashover test platform for type I suspension composite insulator strings on ultra-high voltage transmission lines; (2) Hang bird droppings simulants of different lengths under the crossarm and conduct a continuous voltage increase test on the high-voltage end of the insulator; ⑶ According to the recorded test results, summarize the breakdown field strength E of a single test t , calculate the average breakdown electric field strength E of the residual gap between the guano simulant and the grading ring avt , and the maximum and minimum guano flashover shortest remaining air gap length d is obtained from the test standard deviation σ max ,d min ; (4) According to the shortest remaining air gap length for breakdown, scan along the contour trajectory of the pressure equalizing ring, draw the guano protection range, and hang guano simulant on the crossarm at the boundary of the protection range with a margin of 10% to 15%, and observe whether gap breakdown occurs to verify the effectiveness of the protection range; finally, select the area without breakdown as the guano protection range.

2. A method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning according to claim 1, characterized in that: The different lengths of the guano simulant suspended in step (2) are determined by the following method: first, a guano simulation solution is prepared using kaolin, xanthan gum, and NaCl solids in a mass ratio of 5:3:3; then, the viscosity and conductivity of the solution are adjusted; and then, a cotton rope is placed in the guano simulation solution and fully soaked, and the soaked cotton rope is hung under the crossarm.

3. A method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning according to claim 1, characterized in that: The continuous voltage boost test in step (2) refers to using a high voltage power supply to pressurize the high voltage side of the insulator, gradually increasing the voltage until the guano simulant is broken down or the operating phase voltage reaches 210 kV and the voltage withstand test is terminated for 1 minute.

4. A method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning according to claim 1, characterized in that: The average breakdown electric field strength of the remaining gap in step (3) is determined by the following formula: Where: E t is the breakdown field strength of a single test, kV / cm; U is the flashover voltage, kV; d is the shortest remaining air gap between the guano simulant and the grading ring, cm; E avt is the average breakdown electric field strength, kV / cm; N is the number of tests.

5. The method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning according to claim 1, characterized in that: In step (3), the test standard deviation σ is calculated as follows:

6. A method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning according to claim 1, characterized in that: In the step (3), max =U N / [(1+σ)E avt ],d min =U N / [(1-σ)E avt ]; U N is the operating phase voltage, which is 210kV.

7. The method for calculating the guano flashover protection range based on voltage-equalizing ring path scanning according to claim 1, characterized in that: The track scanning in step (4) is performed as follows: using the shortest remaining air gap length d max ,d min Rotate along the surface structure path of the equalizing ring to obtain two guano protection ranges.

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