Risk assessment method suitable for short circuit between ground wires under icing condition

Abstract

The invention belongs to the technical field of risk assessment of ice-coated ground wires, and particularly relates to a risk assessment method suitable for short circuit between ground wires under an ice-coated condition. The risk assessment method comprises the following steps: S1, establishing a risk assessment model of the short circuit between the grounding wire and the ground wire; s2, determining a calculation formula of the risk value of the short circuit between the ground wires; s3, calculating a probability L value of occurrence of a short-circuit fault between the grounding wire and the ground wire of the evaluation object; s4, evaluating the occurrence frequency E of the short-circuit fault between the ground wire and the ground wire by an evaluator according to the actual condition of an evaluation object; s5, calculating the consequence influence C value of the short-circuit fault between the grounding wire and the grounding wire of the evaluation object; s6, calculating the risk value R of the short circuit between the conductor and the ground wire of the evaluation object by combining the L, E and C values calculated in the steps S3-S6 with the step S2; and S7, according to the risk value R of the short circuit between the ground wires, grading the risk of the short circuit between the ground wires of the evaluation object. The evaluation method provided by the invention is simple to implement and operate, and can evaluate a certain grade of a certain specific line.

Description

Technical Field

[0001] The invention belongs to the technical field of risk assessment of ice-covered ground wires, and in particular relates to a risk assessment method for short circuits between ground wires under ice-covered conditions. Background Art

[0002] In recent years, extreme rain, snow and freezing weather have occurred frequently, and icing failures of overhead transmission lines have increased significantly. Short-circuit failures caused by the close distance between the conductor and the ground wire due to icing reasons such as the thickness of the ice on the ground wire being much greater than the thickness of the ice on the conductor, uneven icing or ice shedding and jumping have become one of the common types of icing failures of overhead transmission lines, which have had a significant impact on the safe operation of the power grid.

[0003] At present, there are many methods for assessing the risk of icing of overhead transmission lines, but the assessment method system is complex and difficult for operation and maintenance management personnel to operate. It is not possible to carry out large-scale assessment work effectively and quickly, and the pertinence is not strong. There is a lack of risk assessment methods for short-circuit faults between conductors and ground wires caused by icing, and the operation and maintenance management department cannot carry out targeted prevention and control work. Therefore, by carrying out the risk assessment of short-circuit between conductors and ground wires under the condition of icing on overhead transmission lines in operation, a scientific decision-making reference can be provided for the anti-icing disaster reduction work of the power grid, which is also of great significance to the safe operation of the power grid. Summary of the invention

[0004] In view of this, the present invention discloses a risk assessment method for short circuit between conductors and ground wires under ice-covered conditions.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: A risk assessment method for short circuit between conductors and ground wires under ice-covered conditions, the risk assessment method comprising the following steps: S1. LEC risk assessment method and AHP analytic hierarchy process are combined to establish a risk assessment model for short circuit between conductors and ground wires in the case of icing on overhead lines in operation. S2. Determine the calculation formula for the risk value of short circuit between the conductors and the ground wires; S3. Through analysis and investigation, the factors affecting the probability of short-circuit faults between conductors and ground wires under five types of icing conditions are determined, and each factor is graded and assigned a value. The weight coefficient is determined by using the AHP hierarchical analysis method to quantify the probability of short-circuit faults between conductors and ground wires. According to the actual situation of the evaluation object and the classification and value table of factors affecting the probability of short-circuit faults between conductors and ground wires, the probability of short-circuit faults between conductors and ground wires is quantified. i The value is taken, and the probability L of the occurrence of the short-circuit fault between the conductors of the assessment object is calculated by the short-circuit risk value calculation formula between the conductors and the ground wires; S4. By evaluating the number of times the short-circuit fault occurs between the conductors and the ground, the frequency of the short-circuit fault between the conductors and the ground is quantified. The evaluator determines the frequency E of the short-circuit fault between the conductors and the ground according to the actual situation of the evaluation object. S5, by classifying and assigning values ​​to the voltage level, number of loops and importance of the line, quantifying the factors affecting the consequences of the short-circuit fault between the conductors and the ground wires, and referring to the classification and value table of the factors affecting the consequences of the short-circuit fault between the conductors and the ground wires according to the actual situation of the evaluation object, the y value in step S2 is calculated. i Take the value and calculate the impact C value of the consequence of the short circuit fault between the conductor and the ground wire of the assessment object; S6, calculating the short circuit risk value R between the ground wires of the assessment object by combining the L, E and C values ​​calculated in steps S3-S6 with step S2; S7. Classify the risk level of short circuit between the ground wires of the assessment object according to the risk value R of short circuit between the ground wires.

[0006] Furthermore, the calculation formula for the short circuit risk value between the conductors and the ground wires is: Where R is the risk value, L is the probability of short-circuit fault between the conductor and the ground wire; E is the frequency of short-circuit fault between the conductor and the ground wire; C is the consequence of short-circuit fault between the conductor and the ground wire; m i is the weight of each probability influencing factor of the short circuit fault between the conductor and the ground wire; n i is the value of each probability influencing factor of the short circuit fault between the conductor and the ground wire; x i is the weight of each consequence influencing factor of the short circuit fault between the conductor and the ground wire; i The values ​​of the factors affecting the consequences of a short circuit fault between the conductor and the ground wire.

[0007] Further, in step S3, factors influencing the probability of short-circuit faults between ground conductors under five types of icing conditions include designed icing thickness, micro-topography and micro-meteorology, historically observed maximum icing thickness, span, and ultimate static clearance distance of ground conductors.

[0008] Furthermore, in step S3, the calculation formula of the maximum static clearance distance of the ground conductor is as follows: In the formula: f is the static clearance distance of the ground wire; S v1 , S v2 It is the vertical distance between the ground wires at the tower heads on both sides of the assessment station; S H1 , S H2 is the level between the ground wires at the tower heads on both sides of the assessment station; λ1 is the length of the conductor suspension string; λ2 is the length of the ground wire suspension string; l is the assessment station spacing; h is the height difference of the conductor hanging points of the assessment station; f1 is the sag of the conductor of the assessment station when there is no ice; f2 is the sag of the ground wire of the assessment station when it is covered with ice.

[0009] Further, in step S7, the method for determining the risk level of short circuit between conductors and ground wires includes: When the risk value R<25, the risk level is low risk; when the risk value is 25≤R<40, the risk level is medium risk; when the risk value is 40≤R≤100, the risk level is high risk.

[0010] The beneficial effects of the present invention are: The present invention provides a risk assessment method for short circuit between conductors under ice conditions. The assessment method is simple to implement and can be used to assess a certain level of a specific line. The following technical points are mainly adopted: (1) Determine the probability influencing factors of the occurrence of short circuit between conductors and ground wires and perform graded quantification. (2) Determine the consequence influencing factors of the occurrence of short circuit between conductors and ground wires and perform graded quantification. (3) Use the AHP hierarchical analysis method to determine the weights of the probability influencing factors and the consequence influencing factors.

[0011] The evaluator of the present invention can complete the evaluation by consulting the basic design conditions of the line and the line operation data in combination with the classification and value table in the attached figure. The operation is simple. The technology is used for the short-circuit risk assessment of the ground wire of the operating overhead transmission line, which can effectively reduce the manpower and time investment in the evaluation work. Through this technology, the risk of short circuit between the ground wires in the case of ice on the operating overhead line can be graded, thereby providing a scientific decision-making basis for the prevention and control of short circuit faults between the ground wires in the case of ice on the operating overhead line. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The present invention is a flow chart of the risk assessment of short circuit between ground wires.

[0013] Figure 2 It is a classification and value table of factors affecting the probability of short-circuit faults between conductors and ground wires.

[0014] Figure 3 It is a frequency classification and value table of short-circuit faults between conductors and ground wires.

[0015] Figure 4 It is a classification and value table of factors affecting the consequences of a short circuit fault between conductors and ground wires.

[0016] Figure 5 It is a risk level table of short circuit between conductors and ground wires of overhead transmission lines. DETAILED DESCRIPTION

[0017] In order to better understand the present invention, the content of the present invention is further clearly described below in conjunction with the embodiments and the accompanying drawings, but the protection content of the present invention is not limited to the following embodiments. In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0018] like Figure 1-5 As shown, the purpose of this embodiment is to provide a risk assessment method for short circuit between conductors and ground wires in ice-covered conditions, and the risk assessment method comprises the following steps: S1. LEC risk assessment method and AHP analytic hierarchy process are combined to establish a risk assessment model for short circuit between conductors and ground wires in the case of icing on overhead lines in operation. S2. Determine the calculation formula for the short circuit risk value between the conductors and the ground wires. The calculation formula for the short circuit risk value between the conductors and the ground wires is: Where R is the risk value, L is the probability of short-circuit fault between the conductor and the ground wire; E is the frequency of short-circuit fault between the conductor and the ground wire; C is the consequence of short-circuit fault between the conductor and the ground wire; m i is the weight of each probability influencing factor of the short circuit fault between the conductor and the ground wire; n i is the value of each probability influencing factor of the short circuit fault between the conductor and the ground wire; x i is the weight of each consequence influencing factor of the short circuit fault between the conductor and the ground wire; i The values ​​of the factors affecting the consequences of a short circuit fault between the conductor and the ground wire.

[0019] S3. Through analysis and investigation, the factors affecting the probability of short-circuit faults between conductors and ground wires under five types of icing conditions are determined, and each influencing factor is graded and assigned a value. The AHP hierarchical analysis method is used to determine the weight coefficient, so as to quantify the probability of short-circuit faults between conductors and ground wires. Figure 2 According to the actual situation of the evaluation object Figure 2 For n in step S2 i Get the value and pass Figure 2 Calculate the probability L of a short circuit fault between the conductor and the ground wire of the evaluation object.

[0020] S4. By evaluating the number of short-circuit faults between the conductors and the ground wires on the line, the frequency of short-circuit faults between the conductors and the ground wires can be quantified. Figure 3 , the assessor shall refer to the actual situation of the assessed object. Figure 3 Take the value of the frequency E of the short-circuit fault between the conductor and the ground wire; S5. By assigning values ​​to the voltage level, number of loops and importance of the line, the factors affecting the consequences of the short circuit between the conductors and the ground are quantified. Figure 4According to the actual situation of the evaluation object, refer to the classification and value table of the consequences of the short-circuit fault between the conductor and the ground wire, and calculate the value of y in step S2. i Take the value and calculate the C value of the consequence of the short circuit fault between the conductor and the ground wire of the assessment object.

[0021] S6. Calculate the short circuit risk value R between the ground wires of the assessment object by combining the L, E and C values ​​calculated in steps S3-S6 with step S2.

[0022] S7. Classify the risk level of short circuit between ground wires of the assessment object according to the risk value R of short circuit between ground wires, such as Figure 5 .

[0023] The present invention is applicable to the risk assessment of short circuit between conductors and ground wires when 35 kV and above overhead transmission lines in operation are covered with ice.

[0024] In step S3, factors influencing the probability of short-circuit faults between ground conductors under five types of icing conditions include designed icing thickness, micro-topography and micro-meteorology, historically observed maximum icing thickness, span, and ultimate static clearance distance of ground conductors.

[0025] In step S3, the calculation formula of the maximum static clearance distance of the ground conductor is as follows: In the formula: f is the static clearance distance of the ground wire; S v1 , S v2 It is the vertical distance between the ground wires at the tower heads on both sides of the assessment station; S H1 , S H2 is the level between the ground wires at the tower heads on both sides of the assessment station; λ1 is the length of the conductor suspension string; λ2 is the length of the ground wire suspension string; l is the assessment station spacing; h is the height difference of the conductor hanging points of the assessment station; f1 is the sag of the conductor of the assessment station when there is no ice; f2 is the sag of the ground wire of the assessment station when it is covered with ice.

[0026] In step S7, the method for determining the risk level of short circuit between ground wires includes: When the risk value R<25, the risk level is low risk; when the risk value is 25≤R<40, the risk level is medium risk; when the risk value is 40≤R≤100, the risk level is high risk.

[0027] The specific implementation steps in this embodiment are: (1) By consulting the basic design conditions and line operation data of the assessment line, determine the design ice thickness of the assessment unit of the assessment line, whether it is micro-topography or micro-meteorology, the maximum ice thickness observed in history, the span, the number of short-circuit faults between the conductors and the ground wires, the line voltage level, the number of loops and importance, etc.

[0028] (2) Compare the designed ice thickness of the line with the ice thickness in the ice area map, and refer to Figure 2 Determine the design ice thickness coefficient value n1. The ice zone map should be selected with the corresponding return period of each voltage level line. The 220kV and below lines are 30-year ice zone maps, the 500kV lines are 50-year ice zone maps, and the UHV lines are 100-year ice zone maps.

[0029] (3) By judging whether the assessment route is located in the micro-topography and micro-meteorological zone, refer to Figure 2 Determine the value of micro-topography and micro-meteorological coefficient n2.

[0030] (4) The ratio of the maximum ice thickness observed in history to the designed ice thickness of the line is calculated by referring to Figure 2 Determine the value of the historical maximum observed ice thickness coefficient n3. The historical maximum observed ice thickness should be the equivalent ice thickness.

[0031] (5) By calculating the difference between the evaluation span and the reference span of the evaluation line, △l, refer to Figure 2 Determine the value of the span coefficient n4. The span difference △l = the assessment span - the reference span. The reference span values ​​for each voltage level are as follows: 250 meters for 35kV; 290 meters for 110kV; 320 meters for 220kV; 420 meters for 500kV; and 530 meters for UHV.

[0032] (6) By calculating the ratio k of the maximum static clearance distance of the ground wire of the assessment line and the allowable operating overvoltage clearance value, refer to Table 1 to determine the value of the maximum static clearance distance coefficient of the ground wire n5. The maximum static clearance distance of the ground wire is defined as the minimum distance between the ground wire when the conductor is not covered with ice and the ground wire is covered with ice at the maximum. The allowable operating overvoltage clearance value is the clearance value corresponding to the voltage level and altitude of the assessment line.

[0033] (7) The calculation formula for the maximum static clearance distance of the ground wire is as follows: In the formula: f is the static clearance distance of the ground wire; S v1 , S v2 It is the vertical distance between the ground wires at the tower heads on both sides of the assessment station; S H1 , S H2 is the level between the ground wires at the tower heads on both sides of the assessment station; λ1 is the length of the suspended conductor string; λ2 is the length of the suspended ground wire string; l is the assessment station spacing; h is the height difference of the wire hanging points of the assessment station; f1 is the sag of the assessment station conductor when there is no ice; f2 is the sag of the assessment station ground wire when it is covered with ice.

[0034] (8) After determining n1, n2, n3, n4, and n5, use the formula to calculate the risk value of short circuit between conductors and ground wires. Calculate the probability L of a short circuit fault between the conductors and the ground wires of the evaluation line.

[0035] (9) Investigate and evaluate the number of short-circuit faults between the conductor and the ground wire on the line or other nearby lines, and refer to Figure 3 Determine the frequency E value of short circuit fault between the conductor and the ground wire of the evaluation line.

[0036] (10) By evaluating the voltage level of the line Figure 4 Confirm that the voltage level coefficient value is y1.

[0037] (11) By evaluating the number of circuits in the circuit Figure 4 Confirm that the loop number coefficient value is y2.

[0038] (12) By judging whether the assessed line is an important transmission line or an important transmission line section, refer to Figure 4 Confirm that the importance coefficient is y3.

[0039] (13) After determining y1, y2, and y3, use the formula Calculate the impact C value of the consequence of a short circuit fault between the conductor and the ground wire of the evaluation line.

[0040] (14) The L, E and C values ​​calculated in steps (8), (9) and (13) are used to calculate the short-circuit risk value R between the conductors of the assessment line using the short-circuit risk value calculation formula between the conductors and the ground wires.

[0041] (15) After calculating the short-circuit risk value R between the conductors and the ground wires of the assessment line, refer to Figure 5 Determine the risk level of short circuit between the conductors and ground wires of the assessment line.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Other modifications or equivalent substitutions made to the technical solution of the present invention by ordinary technicians in the field should be included in the scope of the claims of the present invention as long as they do not depart from the spirit and scope of the technical solution of the present invention.

Claims

1. A risk assessment method for short circuit between conductors and ground wires in ice-covered conditions, characterized in that: The risk assessment method comprises the following steps: S1. LEC risk assessment method and AHP analytic hierarchy process are combined to establish a risk assessment model for short circuit between conductors and ground wires in the case of icing on overhead lines in operation. S2. Determine the calculation formula for the risk value of short circuit between the conductors and the ground wires; S3. Through analysis and investigation, the factors affecting the probability of short-circuit faults between conductors and ground wires under five types of icing conditions are determined, and each factor is graded and assigned a value. The weight coefficient is determined by using the AHP hierarchical analysis method to quantify the probability of short-circuit faults between conductors and ground wires. According to the actual situation of the evaluation object and the classification and value table of factors affecting the probability of short-circuit faults between conductors and ground wires, the probability of short-circuit faults between conductors and ground wires is quantified. i The value is taken, and the probability L value of the occurrence of the short-circuit fault between the conductors of the assessment object is calculated by the short-circuit risk value calculation formula between the conductors; S4. By evaluating the number of times the short-circuit fault occurs between the conductors and the ground, the frequency of the short-circuit fault between the conductors and the ground is quantified. The evaluator determines the frequency E of the short-circuit fault between the conductors and the ground according to the actual situation of the evaluation object. S5, by classifying and assigning values ​​to the voltage level, number of loops and importance of the line, quantifying the factors affecting the consequences of the short-circuit fault between the conductors and the ground wires, and referring to the classification and value table of the factors affecting the consequences of the short-circuit fault between the conductors and the ground wires according to the actual situation of the evaluation object, the y value in step S2 is calculated. i Take the value and calculate the impact C value of the consequence of the short circuit fault between the conductor and the ground wire of the assessment object; S6, calculating the short circuit risk value R between the ground wires of the assessment object by combining the L, E and C values ​​calculated in steps S3-S6 with step S2; S7. Classify the risk of short circuit between the ground wires of the assessment object according to the risk value R of short circuit between the ground wires.

2. A risk assessment method for short circuit between conductors and ground wires in ice-covered conditions according to claim 1, characterized in that: The calculation formula of the short circuit risk value between the conductor and the ground wire is: Where R is the risk value, L is the probability of short-circuit fault between the conductor and the ground wire; E is the frequency of short-circuit fault between the conductor and the ground wire; C is the consequence of short-circuit fault between the conductor and the ground wire; m i is the weight of each probability influencing factor of the short circuit fault between the conductor and the ground wire; n i is the value of each probability influencing factor of the short circuit fault between the conductor and the ground wire; x i is the weight of each consequence influencing factor of the short circuit fault between the conductor and the ground wire; i The values ​​of the factors affecting the consequences of a short circuit fault between the conductor and the ground wire.

3. A risk assessment method for short circuit between conductors and ground wires in ice-covered conditions according to claim 2, characterized in that: In step S3, factors influencing the probability of short-circuit faults between ground conductors under five types of icing conditions include designed icing thickness, micro-topography and micro-meteorology, historically observed maximum icing thickness, span, and ultimate static clearance distance of ground conductors.

4. A risk assessment method for short circuit between conductors and ground wires in ice-covered conditions according to claim 3, characterized in that: In step S3, the calculation formula of the maximum static clearance distance of the ground conductor is as follows: In the formula: f is the static clearance distance of the ground wire; S v1 , S v2 It is the vertical distance between the ground wires at the tower heads on both sides of the assessment station; S H1 , S H2 is the level between the ground wires at the tower heads on both sides of the assessment station; λ1 is the length of the conductor suspension string; λ2 is the length of the ground wire suspension string; l is the assessment station spacing; h is the height difference of the conductor hanging points of the assessment station; f1 is the sag of the conductor of the assessment station when there is no ice; f2 is the sag of the ground wire of the assessment station when it is covered with ice.

5. A risk assessment method for short circuit between conductors and ground wires in ice-covered conditions according to claim 4, characterized in that: In step S7, the method for determining the risk level of short circuit between ground wires includes: When the risk value R<25, the risk level is low risk; when the risk value is 25≤R<40, the risk level is medium risk; when the risk value is 40≤R≤100, the risk level is high risk.

Images