Lightning protection checking and evaluating method for power transmission line

Abstract

The invention relates to a lightning protection checking and evaluating method for a power transmission line. The method comprises the steps of collecting power grid operation information; according to the collected power grid operation information, the back strike-out rate and the shielding failure trip-out rate of each tower are calculated respectively; calculating results of the towers are weighted and summed according to spans, and the lightning trip-out rate of the line is obtained; dividing lightning stroke risk grades according to the obtained lightning stroke trip-out rate of the line; and formulating a lightning protection treatment scheme according to the divided lightning stroke risk levels. The lightning stroke trip-out rate is calculated through the counterattack and shielding failure evaluation method, the lightning stroke risk level can be scientifically divided, the lightning protection treatment plan is reasonably formulated according to the lightning protection performance checking evaluation result, and the lightning protection capability of the power transmission line is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of power grid operation evaluation, and in particular to a method for evaluating the lightning protection of a power transmission line. Background Art

[0002] In recent years, the company's power grid has continued to develop rapidly, and the demands of all sectors of society for the quality of power supply from the power grid have been increasing. However, the risks of power grids caused by lightning failures continue to increase and become more prominent. Lightning damage has become one of the main reasons for the tripping of transmission lines.

[0004] In daily operation and maintenance, there is a lack of systematic verification and assessment of the lightning protection level of the line, the weak points of lightning protection of power grid transmission lines are not clear, and the depth of lightning protection assessment is not enough. It is necessary to carry out lightning protection verification and assessment, taking into account the differences in characteristics such as lightning activity in the line corridor, topography, and line structure, calculate the lightning resistance performance of the tower, evaluate the lightning damage risk of the tower, and formulate a lightning protection management plan. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a method for checking and evaluating lightning protection of power transmission lines. Through the counter-strike and shielding evaluation methods, the lightning tripping rate is calculated, the lightning risk level can be scientifically divided, and a lightning protection management plan can be reasonably formulated based on the lightning protection performance verification and evaluation results to improve the lightning protection capability of transmission lines.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] A method for verifying and evaluating lightning protection of a power transmission line comprises the following steps:

[0008] Step 1: Collect power grid operation information;

[0009] Step 2: According to the power grid operation information collected in step 1, the back-strike tripping rate and the shielding failure tripping rate of each tower are calculated respectively;

[0010] Step 3, weighted sum of the calculation results of each tower in step 2 according to the span to obtain the lightning trip rate of the line;

[0011] Step 4: classify the lightning risk level according to the lightning trip rate of the line obtained in step 3;

[0012] Step 5: Develop a lightning protection plan based on the lightning risk levels classified in step 4.

[0013] Moreover, the grid operation information in step 1 includes ground lightning density, equivalent gap length of insulator string, average operating voltage of insulator string, system rated line voltage, number of ground wires, terrain, positive polarity 50% impulse discharge voltage of insulator string, height of cross arm to ground, tower height, average height of ground wire, protection angle of ground wire to side conductor, height of ground wire suspension point, conductor wave impedance, positive polarity 50% impulse discharge voltage of insulator string, equivalent gap length of insulator string and average operating voltage of insulator string.

[0014] Moreover, the counter-attack tripping rate in step 2 is calculated by the annual number of lightning strikes per 100 km of the line, the arcing rate, the pole striking rate and the counter-attack lightning resistance level.

[0015] Moreover, the number of lightning strikes is calculated by ground-to-ground lightning density; the arcing rate is calculated by the equivalent gap length of the insulator string, the average operating voltage of the insulator string and the rated line voltage of the system; the pole striking rate is calculated by the number of ground wires and the terrain; and the counter-strike lightning resistance level is calculated by the positive polarity 50% impulse discharge voltage of the insulator string, the height of the crossarm to the ground, the pole tower height and the average height of the ground wire.

[0016] Moreover, the shielding failure trip rate in step 2 is calculated by the annual number of lightning strikes per 100 km of the line, the shielding failure rate, the shielding failure lightning resistance level and the arcing rate.

[0017] Moreover, the annual number of lightning strikes per 100 km of the line is calculated by the ground lightning density, the shielding rate is calculated by the ground wire side conductor protection angle and the ground wire suspension point height, the shielding lightning resistance level is calculated by the conductor wave impedance and the positive polarity 50% impulse discharge voltage of the insulator string, and the arc establishment rate is calculated by the equivalent gap length of the insulator string, the average operating voltage of the insulator string and the system rated line voltage.

[0018] Moreover, the specific implementation method of step 4 is: compare the calculated value of the lightning trip rate with the reference value of the operating procedure control, and classify 0 to 0.5 times as Level I, 0.5 to 1 times as Level II, 1 to 1.5 times as Level III, and more than 1.5 times as Level IV.

[0019] Moreover, the specific implementation method of step 5 is: installing line lightning arresters on towers with lightning risk level IV; and the following towers with lightning risk level III may choose to install line lightning arresters.

[0020] The advantages and positive effects of the present invention are:

[0021] The present invention collects power grid operation information; according to the collected power grid operation information, calculates each pole tower to obtain the counter-attack trip rate and the shielding failure trip rate; weights and sums the calculation results of each pole tower according to the span to obtain the lightning trip rate of the line; divides the lightning risk level according to the obtained lightning trip rate of the line; and formulates a lightning protection and governance plan according to the divided lightning risk level. The present invention calculates the lightning trip rate through the counter-attack and shielding failure evaluation methods, can scientifically divide the lightning risk level, reasonably formulate a lightning protection and governance plan based on the lightning protection performance verification and evaluation results, and improve the lightning protection capability of the transmission line. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] A method for checking and evaluating lightning protection of transmission lines, such as Figure 1 As shown, the following steps are included:

[0025] Step 1: Collect grid operation information.

[0026] The grid operation information includes ground flash density, equivalent gap length of insulator string, average operating voltage of insulator string, system rated line voltage, number of ground wires, terrain, 50% positive polarity impulse discharge voltage of insulator string, height of crossarm to ground, tower height, average height of ground wire, protection angle of ground wire to side conductor, height of ground wire suspension point, conductor wave impedance, 50% positive polarity impulse discharge voltage of insulator string, equivalent gap length of insulator string and average operating voltage of insulator string.

[0027] Step 2: According to the power grid operation information collected in step 1, the back-strike tripping rate and the shielding failure tripping rate of each tower are calculated respectively.

[0028] The strike-back tripping rate is calculated based on the annual number of lightning strikes per 100 km of the line, the arcing rate, the pole striking rate and the strike-back lightning resistance level.

[0029] The number of lightning strikes is calculated by the ground-to-ground lightning density; the arcing rate is calculated by the equivalent gap length of the insulator string, the average operating voltage of the insulator string and the rated line voltage of the system; the pole strike rate is calculated by the number of ground wires and the terrain; the counter-strike lightning resistance level is calculated by the positive polarity 50% impulse discharge voltage of the insulator string, the height of the crossarm to the ground, the pole tower height and the average height of the ground wire.

[0030] The shielding failure tripping rate is calculated based on the annual number of lightning strikes per 100 km of the line, the shielding failure rate, the shielding failure lightning resistance level and the arcing rate.

[0031] The annual number of lightning strikes per 100 km of the line is calculated by the ground lightning density, the shielding rate is calculated by the ground wire protection angle of the side conductor and the height of the ground wire suspension point, the shielding lightning resistance level is calculated by the conductor wave impedance and the positive polarity 50% impulse discharge voltage of the insulator string, and the arc establishment rate is calculated by the equivalent gap length of the insulator string, the average operating voltage of the insulator string and the system rated line voltage.

[0032] Step 3: weighted sum the calculation results of each tower in step 2 according to the span to obtain the lightning tripping rate of the line.

[0033] Step 4: classify the lightning risk level according to the lightning trip rate of the line obtained in step 3.

[0034] The lightning risk level is divided into two levels: the calculated value of the lightning tripping rate is compared with the reference value of the operating procedure control. A value below 1 times is low risk, and a value above 1 times is high risk.

[0035] Furthermore, as shown in Table 1, 0 to 0.5 times is classified as Class I, 0.5 to 1 times is classified as Class II, 1 to 1.5 times is classified as Class III, and more than 1.5 times is classified as Class IV.

[0036] Table 1 Classification of lightning risk levels

[0037]

[0038] A lightning protection plan is formulated based on the lightning risk level. The towers and methods for installing line lightning arresters are as follows:

[0039] a) Towers with lightning risk level IV should be equipped with line arresters;

[0040] b) The following towers with lightning risk level III can be installed with line arresters:

[0041] 1) Towers with k>1.2 and a span of more than 600m on one side;

[0042] 2) Tension corner tower with k>1.2;

[0043] 3) Towers with k<0.8 and where resistance reduction is difficult or uneconomical.

[0044] Wherein, k = shielding failure tripping rate / backlash tripping rate.

[0045] Step 5: Develop a lightning protection plan based on the lightning risk levels classified in step 4.

[0046] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. A method for checking and evaluating lightning protection of power transmission lines, characterized in that: The following steps are involved: Step 1: Collect power grid operation information; Step 2: According to the power grid operation information collected in step 1, the back-strike tripping rate and the shielding failure tripping rate of each tower are calculated respectively; Step 3, weighted sum of the calculation results of each tower in step 2 according to the span to obtain the lightning trip rate of the line; Step 4: classify the lightning risk level according to the lightning trip rate of the line obtained in step 3; Step 5: Develop a lightning protection plan based on the lightning risk levels classified in step 4.

2. A method for checking and evaluating lightning protection of power transmission lines according to claim 1, characterized in that: The grid operation information in step 1 includes ground lightning density, equivalent gap length of insulator string, average operating voltage of insulator string, system rated line voltage, number of ground wires, terrain, 50% positive polarity impulse discharge voltage of insulator string, height of cross arm to ground, tower height, average height of ground wire, protection angle of ground wire to side conductor, height of ground wire suspension point, conductor wave impedance, 50% positive polarity impulse discharge voltage of insulator string, equivalent gap length of insulator string and average operating voltage of insulator string.

3. A method for checking and evaluating lightning protection of power transmission lines according to claim 1, characterized in that: The counter-strike trip rate in step 2 is calculated by the annual number of lightning strikes per 100 km of the line, the arcing rate, the pole striking rate and the counter-strike lightning resistance level.

4. A method for checking and evaluating lightning protection of power transmission lines according to claim 3, characterized in that: The number of lightning strikes is calculated by ground-to-ground lightning density; the arcing rate is calculated by the equivalent gap length of the insulator string, the average operating voltage of the insulator string and the rated line voltage of the system; the pole striking rate is calculated by the number of ground wires and the terrain; and the counter-strike lightning resistance level is calculated by the positive polarity 50% impulse discharge voltage of the insulator string, the height of the crossarm to the ground, the pole tower height and the average height of the ground wire.

5. A method for checking and evaluating lightning protection of power transmission lines according to claim 1, characterized in that: In step 2, the shielding failure trip rate is calculated by the annual number of lightning strikes per 100 km of the line, the shielding failure rate, the shielding failure lightning resistance level and the arcing rate.

6. A method for checking and evaluating lightning protection of power transmission lines according to claim 5, characterized in that: The annual number of lightning strikes per 100 km of the line is calculated by the ground lightning density, the shielding rate is calculated by the ground wire side conductor protection angle and the ground wire suspension point height, the shielding lightning resistance level is calculated by the conductor wave impedance and the positive polarity 50% impulse discharge voltage of the insulator string, and the arc establishment rate is calculated by the equivalent gap length of the insulator string, the average operating voltage of the insulator string and the system rated line voltage.

7. A method for checking and evaluating lightning protection of power transmission lines according to claim 1, characterized in that: The specific implementation method of step 4 is: compare the calculated value of the lightning trip rate with the reference value of the operating procedure control, and classify 0 to 0.5 times as Level I, 0.5 to 1 times as Level II, 1 to 1.5 times as Level III, and more than 1.5 times as Level IV.

8. A method for checking and evaluating lightning protection of power transmission lines according to claim 1, characterized in that: The specific implementation method of step 5 is: installing line lightning arresters on towers with lightning risk level IV; and the following towers with lightning risk level III may choose to install line lightning arresters.

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