Calculation method for sensing overvoltage of power distributing line based on PSCAD (power systems computer aided design)/EMTDC (electromagnetic transients including DC)

A technology of induced overvoltage and calculation method, applied in the electrical field, can solve problems such as complex numerical calculation methods, and achieve the effects of simple application, convenient lightning protection measures, and simple application

Inactive Publication Date: 2013-11-20
CHINA UNIV OF PETROLEUM (EAST CHINA)
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Problems solved by technology

Overcome the shortcomings of inaccurate empirical formulas and complex numerical...
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Abstract

The invention relates to a calculation method for sensing overvoltage of a power distributing line based on PSCAD (power systems computer aided design)/EMTDC (electromagnetic transients including DC). The method mainly comprises the following steps of establishing a PSCAD/EMTDC circuit model of a power line sensing in a thunderbolt, designing a sensing overvoltage calculation self-definition element, and enclosing the PSCAD/EMTDC circuit model of the power line sensing in the thunderbolt and the sensing overvoltage self-definition element into a model in the PSCAD/EMTDC of the power line sensing in the thunderbolt. By adopting the calculation method, the model is established to more simply and conveniently calculate the sensing overvoltage of the power distributing line, and the analysis is carried out on the sensing overvoltage. According to the calculation method, the defects of an inaccurate experience formula and a complicate figure calculation method are overcome, and the efficiency of analyzing the sensing overvoltage is improved.

Application Domain

Technology Topic

Power systems computer aided designEngineering +3

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  • Calculation method for sensing overvoltage of power distributing line based on PSCAD (power systems computer aided design)/EMTDC (electromagnetic transients including DC)
  • Calculation method for sensing overvoltage of power distributing line based on PSCAD (power systems computer aided design)/EMTDC (electromagnetic transients including DC)
  • Calculation method for sensing overvoltage of power distributing line based on PSCAD (power systems computer aided design)/EMTDC (electromagnetic transients including DC)

Examples

  • Experimental program(1)

Example Embodiment

[0018] The present invention will be further described in detail below in conjunction with the drawings.
[0019] The PSCAD/EMTDC-based calculation method of induced overvoltage on distribution lines mainly includes the following steps:
[0020] (1) Calculate the horizontal, vertical and transverse magnetic field components of the electric field generated by lightning strikes. The calculation method includes the following steps:
[0021] 1) The lightning channel is equivalent to the vertical channel connecting the cloud and the ground, the lightning channel is divided into continuous dipoles, the electromagnetic field generated by each dipole is calculated separately, and the electromagnetic field of each dipole can be vectorized Obtain the total electromagnetic field generated by the lightning channel current. Use the electric field calculation model derived by Master and Uman to calculate the horizontal, vertical and transverse magnetic field components of the electric field generated by the main lightning discharge;
[0022]
[0023] + ∫ - H H [ 3 r ( z - z ′ ) cR 4 i ( z ′ , t - R / c ) + r ( z - z ′ ) c 2 R 3 ∂ i ( z ′ , t - R / c ) ∂ t ] dz ′ }
[0024]
[0025] + ∫ - H H [ 2 ( z - z ′ ) 2 - r 2 cR 4 i ( z ′ , t - R / c ) - r 2 c 2 R 3 ∂ i ( z ′ , t - R / c ) ∂ t ] dz ′ }
[0026]
[0027] among them, with They are the horizontal component, vertical component and transverse magnetic field intensity component of the electric field; ε 0 And μ 0 Are the vacuum dielectric constant and magnetic permeability; c is the speed of light; r, And z are the radial coordinate, azimuth angle and axial coordinate of the space point respectively; R is the distance from the current dipole to the point to be sought; H is the height of the lightning channel.
[0028] 2) When considering the influence of soil resistivity, the horizontal component of the electric field is calculated according to the Cooray-Rubinstein formula based on the dipole method:
[0029]
[0030] This formula is the frequency domain calculation formula, where, Is the horizontal component of electric field considering the influence of soil resistivity; ε rg Is the relative permittivity of the soil; σ is the electrical conductivity of the earth, which has a reciprocal relationship with the soil resistivity. Use vector matching technology to decompose the complex frequency domain expression of the above formula into the sum of multiple rational fractions, and derive the approximate time domain expression through the pull inverse transform:
[0031] x k , n = x k , n - 1 e ( a k / τ G ) Δt + ( e ( a k / τ G ) Δt - 1 ) X [ τ G ( H n - H n - 1 ) / ( a k 2 Δt ) + H n - 1 / a k ] - ( H n - H n - 1 ) / a k , k = 1 . . . N RA E r , n σ = E r , n - η H n - η X k = 1 N RA r k x k , n
[0032] Where N RA Is the number of rational fractions after decomposition; τ G =ε 0 ε rg /σ; a k ,r k They are the poles and residues of the rational fraction.
[0033] (2) Establish the PSCAD/EMTDC circuit model of the line under lightning induction: derive the equivalent calculation circuit of the line under lightning induction according to the electromagnetic field-line coupling model, and establish the equivalent calculation circuit of the line under lightning induction in PSCAD/EMTDC according to the equivalent calculation circuit Value circuit model;
[0034] The line coupling model describes the relationship between the induced voltage and current of the line and the lightning electromagnetic field. The induced overvoltage of the line can be calculated by solving the field-line coupling model. The Agrawal field-line coupling model is used to derive the equivalent circuit. The Agrawal model of the multi-conductor line is:
[0035] ∂ ∂ x [ v i s ( x , t ) ] + [ L ij ′ ] ∂ ∂ t [ i i ( x , t ) ] = [ E x e ( x , h i , t ) ]
[0036] ∂ ∂ x [ i i ( x , t ) ] + [ C ij ′ ] ∂ ∂ t [ v i s ( x , t ) ] = 0
[0037] among them They are the inductance and capacitance matrix per unit length of the wire; Is the scattering voltage vector in kV; [i i (x,t)] is the line current vector, the unit is kA; Is the vector of the horizontal component of the incident electric field, in kV/m. The voltage in the above formula is the scattered voltage, and the total voltage (kV) on the wire is calculated as follows:
[0038] [ v i ( x , t ) ] = [ v i s ( x , t ) ] - ∫ 0 h i [ E z i ( x , z , t ) ] dz
[0039] among them, Is the vertical component of the incident electric field, in kV/m. Correct And [i i (x,t)] performs phase-mode transformation to obtain the Agrawal wave equation on the modulus,
[0040] ∂ ∂ x [ v i m ( x , t ) ] + [ L m ] ∂ ∂ t [ i i m ( x , t ) ] = T V - 1 [ E x e ( x , h i , t ) ]
[0041] ∂ ∂ x [ i i m ( x , t ) ] + [ C m ] ∂ ∂ t [ v i m ( x , t ) ] = 0
[0042] In the formula, [L m ], [C m ] Is the inductance and capacitance matrix on the modulus, T V , T I Is the scattering voltage and current transformation matrix, known Desirable T V = T I =T, the matrix T is calculated according to the Jacobian method, at this time, [C m ]=μ 0 ε 0 [L m ] -1 , The modulus wave velocity is Modulus characteristic impedance matrix Use the characteristic line method to analyze the Agrawal model and derive the equivalent calculation circuit of induced overvoltage as attached figure 2 Shown. In the figure, the power supply value is calculated as follows:
[0043] [ i L p ( t ) ] = [ i i ( x 2 , t - T D ) ] - Y [ v i s ( x 2 , t - T D ) ]
[0044] [ i R p ( t ) ] = [ i i ( x 1 , t - T D ) ] + Y [ v i s ( x 1 , t - T D ) ]
[0045] [ i L i ( t ) ] = Y ∫ x 1 x 2 [ E x e ( x , t - x - x 1 v ) ] dx
[0046] [ i R i ( t ) ] = Y ∫ x 1 x 2 [ E x e ( x , t - x 2 - x v ) ] dx
[0047] [ v L e ( t ) ] = [ h i E z i ( x 1 , z , t ) ]
[0048] [ v R e ( t ) ] = = [ h i E z i ( x 2 , z , t ) ]
[0049] Where x 1 , X 2 (X 1 2 ) Is the abscissa of both ends of the line, Y=T[Z Ci ] -1 T -1 , T D =l/c, l is the line length, the resistance value in the figure is calculated according to the matrix Y. The voltage in the above formula is the scattering voltage, and L and R represent the left end of the circuit and the right end of the circuit, respectively. Characterize the influence of the line wave process, Characterize the influence of the horizontal component of the electric field on the line, Characterize the influence of the vertical component of the electric field on the circuit, and obtain a complete circuit diagram of the equivalent calculation of induced overvoltage.
[0050] according to figure 2 As shown in the circuit diagram, the equivalent circuit is established in PSCAD/EMTDC, and each section of the circuit excited by the lightning electromagnetic field can be equivalent to the equivalent circuit.
[0051] (3) Design the custom component for induced overvoltage calculation. The design of the custom component for induced overvoltage includes a parameter input box and a mathematical calculation model. The parameter input box transmits the parameters required for calculation of the line structure, return model and ground to the mathematical calculation model. , Mathematical calculation models include line electrical parameter calculation, electromagnetic field calculation, phase mode transformation and equivalent circuit parameter calculation, etc. The electromagnetic field calculation is calculated according to the mathematical model in step (1), and the line structure, return model and earth can be adjusted through the parameter box. parameter;
[0052] The design of the induced overvoltage custom component is implemented using FORTRAN language programming, including two parts, one is the design of the mathematical calculation model Script, and the other is the design of the input field of the parameter input box. Through the parameter input box, you can input the lightning return strike model parameters, Lightning current parameters, line structure parameters and earth parameters, etc. The mathematical calculation model performs electromagnetic field calculation, line electrical parameter calculation, phase-to-mode conversion calculation and equivalent circuit element parameter calculation according to the parameters input in the parameter input box.
[0053] Such as image 3 As shown, the program flow of the mathematical calculation model Script is: After the custom induced overvoltage component model starts to run, enter the parameter information from the input box, and the program automatically judges the simulation time in PSCAD/EMTDC. If the simulation time is 0, then calculate T, Y and R are also saved, and the horizontal and vertical components of the electric field at different times on the line under lightning induction are calculated and saved. If the simulation time is not 0, read the line scattering voltage and current at the last simulation time in PSCAD/EMTDC, read the horizontal and vertical components of the electric field at different times in the line in the data file, and calculate the corresponding time The power supply value and voltage source value of the induced overvoltage equivalent calculation circuit are output to the equivalent circuit built by PSCAD/EMTDC.
[0054] (4) Establish a model of the line under lightning induction in PSCAD/EMTDC. Each section of the line is simulated by an induction overvoltage module. The induction overvoltage module is composed of the PSCAD/EMTDC circuit model of the line under lightning induction and a package of custom components for induced overvoltage. .
[0055] (5) Establish the overall simulation model of induced overvoltage, call the induced overvoltage module of the line under lightning induction, and call the existing models of the tower, insulator, arrester and other components in PSCAD, and combine the induced overvoltage module with the tower, insulator, and arrester Related equipment models are connected according to the actual situation, that is, an induced overvoltage module is called between adjacent tower models, the overall model is simulated, and the lightning induced overvoltage is calculated.
[0056] (6) Change the line structure, establish a new overall simulation model of induced overvoltage, change the connection relationship between the induced overvoltage module of the line under lightning induction and the tower, insulator, arrester and other related equipment models, and re-run the calculation of the new lightning induced overvoltage .
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