CN106056851A - Heavy rain early warning method for power grid facilities - Google Patents

Abstract

The invention relates to a rainstorm early warning method for power grid facilities, which includes the following steps in turn: analysis of disaster-causing factors and carrier vulnerability, urban waterlogging assessment, setting of disaster-causing critical rainfall, and early warning of power grid disasters; The early warning methods of carrier vulnerability analysis, urban waterlogging assessment, disaster critical rainfall setting, and power grid disaster early warning can solve the difficulty of early warning of urban waterlogging in the whole process of heavy rain, and solve the whole process of heavy rain according to the early warning technology Among them, the range of urban waterlogging, the depth of waterlogging, the simulation and determination of early warning critical values, etc., can effectively predict waterlogging disasters and reduce property and economic losses caused by waterlogging.

Description

Rainstorm early warning method for power grid facilities

technical field

The invention relates to a rainstorm early warning method for power grid facilities.

Background technique

Urban waterlogging disaster is a common type of urban disaster, which has brought huge damage to cities, especially in coastal cities, often caused by typhoons, heavy rains, and sea tides, resulting in casualties and large property losses. With the continuous economic growth, the urbanization process is accelerating, the scale of the city is expanding and the frequency of extreme weather is increasing, and the planning of urban drainage systems is not even in the urbanization process. The rapid urbanization process and the low-speed drainage pipe network transformation The contradiction between speed and directness is becoming increasingly acute. The original urban drainage standard caused by the blind urbanization process is too low; the urban hardening area increases and the permeability becomes poor; urban planning cannot keep up with urbanization; The disappearance of drainage facilities in the old urban area is difficult. The existing mathematical calculation model and GIS spatial analysis application module are used to simulate the formation process of waterlogging and disaster assessment. The operation is time-consuming, and the powerful spatial analysis function of GIS cannot be fully utilized, which is especially uncomfortable. for real-time simulation of waterlogging disasters. Usually, the urban waterlogging model divides the urban surface into subcatchment areas, but the division of small and medium-scale urban watershed areas is different from the division of large-scale watershed watershed areas, and it is difficult to accurately divide the boundaries between urban watershed areas. The literary catchment area division theory is based on the independence of each catchment area, which is somewhat different from the actual situation. Moreover, this is a black-box model. In the calculation process of urban waterlogging, only the input of rainfall and the output of inward waterlogging results cannot represent the loss and transportation process of water flow. It is difficult to consider various factors that affect waterlogging, such as topography, surface and landform factors. , land use factors, etc., the calculation data accuracy requirements are high, and the data acquisition is difficult, so the actual application of this model is relatively difficult.

Contents of the invention

The technical problem to be solved by the present invention is to provide a rainstorm early warning method for power grid facilities, and solve the problems of long time-consuming and difficult data acquisition in existing urban waterlogging models.

In order to solve the above-mentioned technical problems, the present invention is achieved through the following technical solutions: a method for early warning of rainstorms in power grid facilities, which includes the following steps in turn:

a) Disaster-causing factors and carrier vulnerability analysis: extract different grades of critical rainfall intensity, critical rainfall, critical effective rainfall, submerged range and submerged water depth through rainfall, and analyze the carrier through submerged range and submerged water depth Vulnerability, the critical rainfall intensity is the rainfall per unit time, the critical rainfall is the rainfall within a period of time, and the critical effective rainfall reflects the current rainfall intensity and cumulative rainfall that cause the slope or loose material to generate or possibly cause displacement The equivalent rainfall of action, the critical effective rainfall Re=Ri+Rd+Ir×t, where: Re is the effective rainfall; Ri is the indirect effective rainfall in the previous period, which is the accumulated rainfall before the day; Rd is the direct effective rainfall Rainfall is the cumulative amount of rainfall on the day; Ir is the rainfall intensity; t is the duration of precipitation with the rain intensity of Ir, and the carrier includes substations, power distribution rooms, cable lines and equipment, power distribution terminal equipment, capacitors on poles, Station buildings, distribution transformers, switch cabinets, ring network cabinets, pole-mounted switchgear;

b) Urban waterlogging assessment: analyze the urban waterlogging risk according to the rainfall extracted in step a), and the urban waterlogging risk includes the rainfall process, runoff process, surface confluence process and pipe network confluence process;

c) Disaster-causing critical rainfall setting: Calculate the critical rainfall affected by the rainstorm power grid by statistical induction, and judge whether it exceeds the critical rainfall. When the critical rainfall exceeds the critical rainfall, enter step d). When the critical rainfall does not exceed When critical rainfall, then return to step a);

d) Early warning of power grid disasters: through the early warning processing of the areas exceeding the critical rainfall in step c), and the determination of the early warning level of urban waterlogging points.

Preferably, the rainfall process in step b) is expressed by rainstorm intensity, and the rainstorm intensity includes the following steps:

A rainstorm data sampling: select rainfall events from the existing rainfall data, and the rainfall duration of rainfall events is divided into 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes , the rainfall return periods of rainfall events are calculated according to 0.25 years, 0.33 years, 0.5 years, 1 year, 2 years, 3 years, 5 years and 10 years;

B frequency analysis: According to the rainstorm data selected in step A, the frequency distribution curve of the rainstorm intensity is counted;

C Determine the rainstorm intensity parameters: estimate the rainstorm intensity parameters through the frequency-intensity-duration relationship obtained in steps A and B, and the estimation methods include least square method, simplex method, iterative method and genetic algorithm.

Preferably, the runoff process in step b) is calculated by the runoff coefficient method. The runoff coefficient method divides the urban area into several different surface types and assigns a coefficient to each surface type. Then the coefficient is multiplied by the rainfall to obtain Obtained flow.

Preferably, the surface confluence process in step b) is how the rainwater runoff moves on the surface after it is generated, and finally enters the drainage pipe network through the gully. The surface confluence process includes a hydraulic model and a hydrological model. The hydraulic model is established in On the basis of microscopic physical laws, the temporal and spatial changes of water flow are solved according to the continuity equation and motion equation of water flow. The water flow movement in the catchment area of the gully is a slope flow process. a deterministic relationship.

Preferably, the one-dimensional Saint-Venant equations controlling overland flow motion are:

Among them: x is the flow direction, A is the area perpendicular to the x-axis, Q is the flow through section A, y is the water depth of section A, vx is the average flow velocity of the section, S0 is the ground slope, Sf is the resistance slope, and g is gravity Acceleration, q1 is infiltration or rainfall, resistance slope:

or or

Among them: f is the Weisbach resistance coefficient; n is the Manning roughness coefficient; Kn is the conversion factor, which is 1 when the international system of units is used, and 1.486 when the imperial unit is used; C is the Chezy coefficient; R is the hydraulic radius.

Preferably, the hydrological model represents the confluence time distribution in different areas of the watershed through a time-area diagram, and the unit impulse response is

Among them: (t-τ) is the confluence time, dA is the unit area in the watershed.

Preferably, the rainwater runoff path in the surface confluence process in step b) is composed of a central grid and eight adjacent neighborhood grids, and through the triangular faces of different slopes formed by the neighborhood grid and the central grid, select The aspect of the triangular surface with the largest downhill slope from the central grid is used as the water flow direction of the central grid.

Preferably, the confluence time of rainwater from the central grid to the neighboring grid

Among them: nm is the Manning roughness coefficient of the surface of the grid area, g is the spacing of the DEM grid, I is the net rain, Δh is the elevation difference between two adjacent grids connected by the water flow point, k is the coefficient, when the water flow k=1 when the direction is along the DEM grid direction, and k=2 when the water flow direction is along the diagonal direction.

Preferably, the pipeline water flow in the pipe network confluence process in step b) is

Q _t+Δt =C ₀ I _t+Δt +C ₁ I _t +C ₂ Q _t ;

Among them: I is the upstream inflow of the river section, Q is the upstream and downstream outflow of the river section, and S is the water storage capacity in the river section;

In the above formula: L _g is the length of the pipeline, L is the characteristic river length, Q ₀ is the steady flow corresponding to a certain water depth H, S ₀ is the bottom slope, B is the width of the water surface, C is the wave velocity, C=ηv,η is the wave velocity coefficient, and v is the average velocity of the section.

Preferably, in the step b), the rainwater flow rate in the flow process comprises the following steps:

Step 1: Input the pipeline number of the root pipeline, and search the upstream node connected to it in the database;

Step 2: Find the upstream pipeline connected to it according to the upstream node, if there is, go to step 3, if not, go to step 4;

Step 3: Use the upstream pipeline number as an input to transform and step 1;

Step 4: Set the pipeline in step 1 as an edge pipeline, and its upstream pipe point is an edge pipe point;

Step 5: Calculate the outlet flow of the edge pipeline in step 4 Q ₂ =C ₁ I ₁ +C ₂ I ₂ +C ₃ Q ₁ ; and the deformed pipeline has no upstream pipeline, so the outlet flow of the edge pipeline at this time is Q ₂ =C ₁ H ₁ +C ₂ H ₂ +C ₃ Q ₂ , and save the calculation results;

Step 6: Calculate the outflow of the secondary edge pipeline Q ₂ =C ₁ (Q _L1 +H ₁ )+C ₂ (Q _L2 +H ₂ )+C ₃ Q ₁ based on the outflow of the edge pipeline calculated in step 5, and calculate Save the calculation results;

Step 7: Repeat step 6 until the outflow of the root pipeline is calculated.

In summary, the advantages of the present invention are: through the analysis of disaster-causing factors and the vulnerability of bearing bodies, the evaluation of urban waterlogging, the setting of disaster-causing critical rainfall, and the early warning method of power grid disaster early warning, it can solve the problem of urban waterlogging in the whole process of heavy rain. According to the early warning technology, solve the problems of urban waterlogging range, waterlogging depth, early warning critical value simulation and determination, etc. in the whole process of heavy rain, effectively predict waterlogging disasters and reduce property and economic losses caused by waterlogging.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing:

Fig. 1 is the structural representation of Chicago rainstorm process line of the present invention;

Fig. 2 is a structural schematic diagram of a non-full flow circular tube of the present invention.

detailed description

The rainstorm warning method for power grid facilities includes the following steps in sequence:

a) Disaster-causing factors and carrier vulnerability analysis: extract different grades of critical rainfall intensity, critical rainfall, critical effective rainfall, submerged range and submerged water depth through rainfall, and analyze the carrier through submerged range and submerged water depth Vulnerability, the critical rainfall intensity is the rainfall per unit time, the critical rainfall is the rainfall within a period of time, and the critical effective rainfall reflects the current rainfall intensity and cumulative rainfall that cause the slope or loose material to generate or possibly cause displacement The equivalent rainfall of action, the critical effective rainfall Re=Ri+Rd+Ir×t, where: Re is the effective rainfall; Ri is the indirect effective rainfall in the previous period, which is the accumulated rainfall before the day; Rd is the direct effective rainfall Rainfall is the cumulative amount of rainfall on the day; Ir is the rainfall intensity; t is the duration of precipitation with the rain intensity of Ir, and the carrier includes substations, power distribution rooms, cable lines and equipment, power distribution terminal equipment, capacitors on poles, Station buildings, distribution transformers, switch cabinets, ring network cabinets, pole-mounted switchgear;

b) Urban waterlogging assessment: analyze the urban waterlogging risk according to the rainfall extracted in step a), and the urban waterlogging risk includes the rainfall process, runoff process, surface confluence process and pipe network confluence process;

c) Disaster-causing critical rainfall setting: Calculate the critical rainfall affected by the rainstorm power grid by statistical induction, and judge whether it exceeds the critical rainfall. When the critical rainfall exceeds the critical rainfall, enter step d). When the critical rainfall does not exceed When critical rainfall, then return to step a);

d) Early warning of power grid disasters: through the early warning processing of the areas exceeding the critical rainfall in step c), and the determination of the early warning level of urban waterlogging points.

Preferably, the rainfall process in step b) is expressed by rainstorm intensity, and the rainstorm intensity includes the following steps:

A rainstorm data sampling: select rainfall events from the existing rainfall data, and the rainfall duration of rainfall events is divided into 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes , the rainfall return periods of rainfall events are calculated according to 0.25 years, 0.33 years, 0.5 years, 1 year, 2 years, 3 years, 5 years and 10 years;

B frequency analysis: According to the rainstorm data selected in step A, the frequency distribution curve of the rainstorm intensity is counted;

C Determine the rainstorm intensity parameters: estimate the rainstorm intensity parameters through the frequency-intensity-duration relationship obtained in steps A and B, and the estimation methods include least square method, simplex method, iterative method and genetic algorithm.

When the research area has no rainfall data or insufficient data, the average rainfall intensity is used to represent a rainfall, and the rainfall intensity is constant. In the actual rainfall process, the rainfall intensity is small at the beginning and gradually increases with time. become larger, then smaller until the rain stops, and the corresponding calculation is carried out through the Chicago rainstorm process line shown in Figure 1. In Figure 1, t1 is the time of the peak of the rain, and the rainfall intensity is the largest; t2 is the time when the rain stops; tb represents the peak Before the period, ta represents the period after the peak, the rain peak coefficient γ = t1 = t2, use the rainstorm with the same average intensity as the uniform rain pattern to generate the rainfall hydrograph, and use i(t) to represent the change of rainfall intensity with time, then the duration is The average intensity of rainfall for td is:

After the rain peak is introduced, tb is used to represent the time difference between the pre-peak time and the rain peak time, and ta is used to represent the time difference between the post-peak time and the rain peak time, then the instantaneous rainfall intensity in the pre-peak period is:

The instantaneous rainfall intensity during the post-peak period is:

The piecewise function form of the instantaneous rainstorm intensity of the Chicago rainstorm hydrograph is

When the calculation accuracy of the model is not high, the uniform rain pattern can be used to represent the time distribution of rainfall intensity; if the calculation accuracy is high, the Chicago rainstorm process line is used, and the rain peak coefficient takes the empirical value of 0.4.

The runoff process in step b) is calculated by the runoff coefficient method. The runoff coefficient method divides the urban area into several different surface types and assigns a coefficient to each surface type. Then the coefficient is multiplied by the rainfall to obtain the yield Flow rate, select different runoff coefficients according to different ground types, such as the runoff coefficients of various roofs, concrete or asphalt pavements are 0.85-0.95; The runoff coefficient of graded gravel pavement is 0.40~0.50; the runoff coefficient of dry masonry or gravel pavement is 0.35~0.40; the runoff coefficient of non-paved soil pavement is 0.25~0.35; the runoff coefficient of park or green space is 0.10～0.20.

The surface confluence process in step b) is how the rainwater runoff moves on the surface after it is generated, and finally enters the drainage pipe network through the gully. The surface confluence process includes a hydraulic model and a hydrological model. The hydraulic model is based on microscopic physical laws Based on the continuity equation and motion equation of water flow, the temporal and spatial changes of water flow are solved. The water flow movement in the catchment area of the gully is a slope flow process. relation.

The one-dimensional Saint-Venant equations governing the movement of overland flow are:

Among them: x is the flow direction, A is the area perpendicular to the x-axis, Q is the flow through section A, y is the water depth of section A, vx is the average flow velocity of the section, S0 is the ground slope, Sf is the resistance slope, and g is gravity Acceleration, q1 is infiltration or rainfall, resistance slope:

or or

Among them: f is the Weisbach resistance coefficient; n is the Manning roughness coefficient; Kn is the conversion factor, which is 1 when the international system of units is used, and 1.486 when the imperial unit is used; C is the Chezy coefficient; R is the hydraulic radius.

The hydrological model shows the time distribution of confluence in different areas of the watershed through a time-area diagram, and the unit impulse response is

Among them: (t-τ) is the confluence time, dA is the unit area in the watershed.

Preferably, the rainwater runoff path in the surface confluence process in step b) is composed of a central grid and eight adjacent neighborhood grids, and through the triangular faces of different slopes formed by the neighborhood grid and the central grid, select The aspect of the triangular surface with the largest downhill slope from the central grid is used as the water flow direction of the central grid.

Confluence time of rainwater from the central grid to the neighboring grid

Among them: nm is the Manning roughness coefficient of the surface of the grid area, g is the spacing of the DEM grid, I is the net rain, Δh is the elevation difference between two adjacent grids connected by the water flow point, k is the coefficient, when the water flow k=1 when the direction is along the DEM grid direction, and k=2 when the water flow direction is along the diagonal direction.

The pipeline water flow in the process of pipe network confluence in step b) is

Q _t+Δt =C ₀ I _t+Δt +C ₁ I _t +C ₂ Q _t ;

Among them: I is the upstream inflow of the river section, Q is the upstream and downstream outflow of the river section, and S is the water storage capacity in the river section;

In the above formula: L _g is the length of the pipeline, L is the characteristic river length, Q ₀ is the steady flow corresponding to a certain water depth H, S ₀ is the bottom slope, B is the width of the water surface, C is the wave velocity, C=ηv,η is the wave velocity coefficient, and v is the average velocity of the section.

When the confluence pipe of the pipe network is a non-full flow circular pipe, as shown in Figure 2,

where n is the Manning roughness coefficient, D is the pipe diameter, is the central angle, and we get:

where α and β are The function. According to the research of Cen Guoping and others, α and β can be constants: α=0.15, β=0.75, then:

Then calculate C ₀ , C ₁ and C ₂ , and the flow rate Q _t+Δt after a certain period of time Δt in the pipeline can be calculated from formula 4-2. Combined with the characteristics of the cross-section of the pipeline, the water depth h corresponding to the calculation flow can be obtained from the Manning formula, namely:

First find out through Q Then by Calculate the water depth h of this section. Seek from Q Using Newton's iterative method, let but

Assume Using Newton's iterative formula, we get

Finally got:

Calculating the rainwater flow rate in the flow process in step b) includes the following steps:

Step 1: Input the pipeline number of the root pipeline, and search the upstream node connected to it in the database;

Step 2: Find the upstream pipeline connected to it according to the upstream node, if there is, go to step 3, if not, go to step 4;

Step 3: Use the upstream pipeline number as an input to transform and step 1;

Step 4: Set the pipeline in step 1 as an edge pipeline, and its upstream pipe point is an edge pipe point;

Step 5: Calculate the outlet flow of the edge pipeline in step 4 Q ₂ =C ₁ I ₁ +C ₂ I ₂ +C ₃ Q ₁ ; and the deformed pipeline has no upstream pipeline, so the outlet flow of the edge pipeline at this time is Q ₂ =C ₁ H ₁ +C ₂ H ₂ +C ₃ Q ₂ , and save the calculation results;

Step 6: Calculate the outflow of the secondary edge pipeline Q ₂ =C ₁ (Q _L1 +H ₁ )+C ₂ (Q _L2 +H ₂ )+C ₃ Q ₁ based on the outflow of the edge pipeline calculated in step 5, and calculate Save the calculation results;

Step 7: Repeat step 6 until the outflow of the root pipeline is calculated.

Except above-mentioned preferred embodiment, the present invention also has other embodiments, and those skilled in the art can make various changes and deformations according to the present invention, as long as they do not depart from the spirit of the present invention, all should belong to the scope defined in the appended claims of the present invention scope.

Claims (10)

1. The grid facility rainstorm early warning method is characterized in that: comprises the following steps successively: a) Disaster-causing factors and carrier vulnerability analysis: extract different grades of critical rainfall intensity, critical rainfall, critical effective rainfall, submerged range and submerged water depth through rainfall, and analyze the carrier through submerged range and submerged water depth Vulnerability, the critical rainfall intensity is the rainfall per unit time, the critical rainfall is the rainfall within a period of time, and the critical effective rainfall reflects the current rainfall intensity and cumulative rainfall that cause the slope or loose material to generate or possibly cause displacement The equivalent rainfall of action, the critical effective rainfall Re=Ri+Rd+Ir×t, where: Re is the effective rainfall; Ri is the indirect effective rainfall in the previous period, which is the accumulated rainfall before the day; Rd is the direct effective rainfall Rainfall is the cumulative amount of rainfall on the day; Ir is the rainfall intensity; t is the duration of precipitation with the rain intensity of Ir, and the carrier includes substations, power distribution rooms, cable lines and equipment, power distribution terminal equipment, capacitors on poles, Station buildings, distribution transformers, switch cabinets, ring network cabinets, pole-mounted switchgear; b) Urban waterlogging assessment: analyze the urban waterlogging risk according to the rainfall extracted in step a), and the urban waterlogging risk includes the rainfall process, runoff process, surface confluence process and pipe network confluence process; c) Disaster-causing critical rainfall setting: Calculate the critical rainfall affected by the rainstorm power grid by statistical induction, and judge whether it exceeds the critical rainfall. When the critical rainfall exceeds the critical rainfall, enter step d). When the critical rainfall does not exceed When critical rainfall, then return to step a); d) Early warning of power grid disasters: through the early warning processing of the areas exceeding the critical rainfall in step c), and the determination of the early warning level of urban waterlogging points. 2. The grid facility rainstorm early warning method according to claim 1, is characterized in that: the rainfall process in the step b) is expressed by the rainstorm intensity, and the rainstorm intensity comprises the following steps: A rainstorm data sampling: select rainfall events from the existing rainfall data, and the rainfall duration of rainfall events is divided into 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes, 120 minutes , the rainfall return periods of rainfall events are calculated according to 0.25 years, 0.33 years, 0.5 years, 1 year, 2 years, 3 years, 5 years and 10 years; B frequency analysis: According to the rainstorm data selected in step A, the frequency distribution curve of the rainstorm intensity is counted; C Determine the rainstorm intensity parameters: estimate the rainstorm intensity parameters through the frequency-intensity-duration relationship obtained in steps A and B, and the estimation methods include least square method, simplex method, iterative method and genetic algorithm. 3. the grid facility rainstorm early warning method according to claim 1, is characterized in that: the runoff process in step b) is calculated by the runoff coefficient method, and the runoff coefficient method is divided into several different surface types by the urban area and for each A surface type is assigned a coefficient, which is then multiplied by rainfall to obtain the yield. 4. The power grid facility rainstorm warning method according to claim 1, characterized in that: the surface confluence process in step b) is how to move on the surface after the rainwater runoff produces, and finally enter the process of the drainage pipe network through the storm water outlet, the surface The confluence process includes a hydraulic model and a hydrological model. The hydraulic model is established on the basis of microscopic physical laws, and the temporal and spatial changes of water flow are solved according to the continuity equation and motion equation of water flow. The hydrological model is to establish a certain deterministic relationship between the rainfall input and the outlet flow process of the basin. 5. The grid facility rainstorm early warning method according to claim 4, is characterized in that: the one-dimensional Saint-Venant equations for controlling slope flow motion are: Among them: x is the flow direction, A is the area perpendicular to the x-axis, Q is the flow through section A, y is the water depth of section A, vx is the average flow velocity of the section, S0 is the ground slope, Sf is the resistance slope, and g is gravity Acceleration, q1 is infiltration or rainfall, resistance slope: or or Among them: f is the Weisbach resistance coefficient; n is the Manning roughness coefficient; Kn is the conversion factor, which is 1 when the international system of units is used, and 1.486 when the imperial unit is used; C is the Chezy coefficient; R is the hydraulic radius. 6. The power grid facility rainstorm early warning method according to claim 4, is characterized in that: the hydrology model represents the confluence time distribution in different areas of the watershed by a time area diagram, and the unit impulse response is Among them: (t-τ) is the confluence time, dA is the unit area in the watershed. 7. The power grid facility rainstorm early warning method according to claim 4, is characterized in that: the rainwater runoff path in the surface confluence process in the step b) is made up of central grid and eight adjacent neighborhood grids, through adjacent For the triangular surfaces with different slopes formed by the domain grid and the central grid, the direction of the triangular surface with the largest downward slope from the central grid is selected as the water flow direction of the central grid. 8. The rainstorm warning method for power grid facilities according to claim 7, characterized in that: the time for rainwater to flow from the central grid to the neighboring grid Among them: nm is the Manning roughness coefficient of the surface of the grid area, g is the spacing of the DEM grid, I is the net rain, Δh is the elevation difference between two adjacent grids connected by the water flow point, k is the coefficient, when the water flow k=1 when the direction is along the DEM grid direction, and k=2 when the water flow direction is along the diagonal direction. 9. the power grid facility rainstorm early warning method according to claim 1, is characterized in that: the pipeline water flow in the pipeline network confluence process in the step b) is Q _t+Δt =C ₀ I _t+Δt +C ₁ I _t +C ₂ Q _t ; Among them: I is the upstream inflow of the river section, Q is the upstream and downstream outflow of the river section, and S is the water storage capacity in the river section; In the above formula: L _g is the length of the pipeline, L is the characteristic river length, Q ₀ is the steady flow corresponding to a certain water depth H, S ₀ is the bottom slope, B is the width of the water surface, C is the wave velocity, C=ηv,η is the wave velocity coefficient, and v is the average velocity of the section. 10. The power grid facility rainstorm early warning method according to claim 9, is characterized in that: the rainwater flow rate in the calculation flow process in the step b) comprises the following steps: Step 1: Input the pipeline number of the root pipeline, and search the upstream node connected to it in the database; Step 2: Find the upstream pipeline connected to it according to the upstream node, if there is, go to step 3, if not, go to step 4; Step 3: Use the upstream pipeline number as an input to transform and step 1; Step 4: Set the pipeline in step 1 as an edge pipeline, and its upstream pipe point is an edge pipe point; Step 5: Calculate the outlet flow of the edge pipeline in step 4 Q ₂ =C ₁ I ₁ +C ₂ I ₂ +C ₃ Q ₁ ; and the deformed pipeline has no upstream pipeline, so the outlet flow of the edge pipeline at this time is Q ₂ =C ₁ H ₁ +C ₂ H ₂ +C ₃ Q ₂ , and save the calculation results; Step 6: Calculate the outflow of the secondary edge pipeline Q ₂ =C ₁ (Q _L1 +H ₁ )+C ₂ (Q _L2 +H ₂ )+C ₃ Q ₁ based on the outflow of the edge pipeline calculated in step 5, and calculate Save the calculation results; Step 7: Repeat step 6 until the outflow of the root pipeline is calculated.