CN113742895B - 10kV distribution network composite cross arm lightning protection simulation method - Google Patents
10kV distribution network composite cross arm lightning protection simulation method Download PDFInfo
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Abstract
The invention relates to the technical field of lightning protection simulation of distribution networks, in particular to a 10kV distribution network composite cross arm lightning protection simulation method. A lightning current model, an induced lightning overvoltage model, a line and tower model, a composite cross arm flashover model, a distribution transformer model, a 10kV power supply model and a distribution line lightning arrester model are built in ATP-EMTP software; and connecting the models, adjusting the magnitude of lightning current amplitude in the lightning current model, calculating to obtain the magnitude of three-phase corresponding induced lightning voltage, observing whether flashover occurs in the corresponding composite cross arm flashover model, if flashover does not occur, increasing the magnitude of lightning current in the lightning current model until the composite cross arm flashover model just generates flashover, and recording the magnitude of the corresponding lightning current magnitude, wherein the magnitude of the lightning current is the lightning-resistant level threshold value of the corresponding composite cross arm.
Description
Technical Field
The invention relates to the technical field of lightning protection simulation of distribution networks, in particular to a 10kV distribution network composite cross arm lightning protection simulation method.
Background
The power distribution network is used as a network configuration for directly distributing electric energy to power users, the operation efficiency of the power distribution network directly influences the overall economic benefit of power grid operation, and therefore the safety and reliability of the power distribution network are increasingly emphasized. The distribution network is threatened by direct lightning strike and inductive lightning strike due to the fact that the insulation level of the line is generally low, and the 10kV line trip caused by inductive lightning strike accounts for more than 70% of the line lightning trip. The lightning induction overvoltage is a main factor for causing tripping of the power distribution network and disconnection of the overhead insulated line, and in order to meet the requirements of power supply reliability of different areas, the adoption of the composite insulating cross arm to improve the insulation level of the overhead insulated line is an effective measure for solving the problems of lightning tripping of the power distribution network and lightning disconnection of the insulated conductor.
At present, the cross arm of the distribution network is mostly made of iron materials, has good mechanical property and excellent fatigue resistance, does not influence the strength of the cross arm after being perforated, and has the advantages of low price and the like. However, as the 50% lightning impulse discharge voltage of the insulator adopted on the 10kV traditional iron cross arm is lower, the iron cross arm has low lightning protection level and high lightning trip-out rate. In addition, in the insulated circuit, lightning breakage is easy to occur. In addition, a large number of steel cross beams of the power transmission line of the power distribution network consume a large amount of steel, consume more ore energy, and the production process is accompanied with the problem of environmental pollution. By means of successful operation experience of the composite insulator, the power grid enterprises gradually turn the eyes to the composite cross arm, the advantages of high strength, low weight, corrosion resistance, excellent insulating performance and the like of the composite material are fully utilized, the composite cross arm for the distribution network has the characteristics of good insulating performance, high strength and light weight, and the application of the composite cross arm to the distribution network tower is beneficial to improving the lightning protection performance of the distribution network. Therefore, the composite cross arm has good application prospect.
At present, the research on the lightning protection performance of the composite insulating cross arm is less, and most of the research mainly relates to the lightning protection of common distribution network lines and the performance of a composite insulating cross arm body. In order to study the lightning protection performance of the distribution network composite insulating cross arm and calculate the lightning resistance level of the distribution network line, the invention provides a 10kV distribution network composite cross arm lightning protection simulation method based on ATP-EMTP simulation software, and can provide technical support for expanding the application range of the distribution network composite cross arm.
Disclosure of Invention
In order to solve the problems, the invention provides a 10kV distribution network composite cross arm lightning protection simulation method, which comprises the following steps:
a10 kV distribution network composite cross arm lightning protection simulation method comprises the following steps:
s1: a lightning current model, an induced lightning overvoltage model, a line and tower model, a composite cross arm flashover model, a distribution transformer model, a 10kV power supply model and a distribution line lightning arrester model are built in ATP-EMTP software;
s2: sequentially connecting a 10kV power supply model, a line and tower model, a distribution transformer model and a distribution line lightning arrester model; connecting the composite cross arm flashover model, the lightning current model and the induced lightning overvoltage model with the line and the tower model;
s3: and adjusting the magnitude of lightning current amplitude in the lightning current model, calculating to obtain the magnitude of three-phase corresponding induced lightning voltage, observing whether flashover occurs in the corresponding composite cross arm flashover model, if flashover does not occur, increasing the magnitude of lightning current in the lightning current model until the composite cross arm flashover model just occurs, and recording the magnitude of corresponding induced lightning current, wherein the magnitude of the induced lightning current is the lightning-resistant level threshold value of the corresponding composite cross arm.
Preferably, the step S3 further includes the steps of:
s31: setting the amplitude I of the initial lightning current 0 Calculating to obtain corresponding induced lightning voltage U X0 ，X＝A,B,C；
S32: if the lightning current I is when the lightning-resistant level threshold value of the composite cross arm of the corresponding phase is simulated 0 When no flashover occurs in the lower corresponding composite cross arm flashover model, increasing delta I each time when adjusting lightning current until the flashover occurs in the composite cross arm flashover model when the lightning current is increased to the lightning current I ', and recording the lightning current amplitude I' at the moment and the corresponding calculated induced lightning voltage U of the corresponding phase X '；
Conversely, if it is in the lightning current I 0 When the flashover occurs in the lower corresponding composite cross arm flashover model, reducing delta I each time when adjusting lightning current until flashover does not occur in the composite cross arm flashover model when reducing to lightning current I ', and recording the lightning current amplitude I' at the moment and the corresponding calculated induced lightning voltage U of the corresponding phase X '；
S33: each time delta I ' is reduced on the basis of lightning current I ', no flashover occurs in the composite cross arm flashover model until lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X If delta I ' < delta I, the lightning resistance level threshold of the composite cross arm is between I ' and I ';
on the contrary, the method comprises the steps of,each time delta I ' is increased on the basis of lightning current I ', the flashover of the composite cross arm flashover model occurs until the lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X If delta I ' < delta I, the lightning resistance level threshold of the composite cross arm is between I ' and I ';
s34: each time delta I ' is increased on the basis of the lightning current I ' obtained in the step S33 until the composite cross arm flashover model is flashover when the lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X "', and ΔI" < ΔI'; then the lightning resistance level threshold of the composite cross arm is known to be between I 'and I';
otherwise, the delta I ' is reduced each time on the basis of the lightning current I ' obtained in the step S33 until no flashover occurs in the composite cross arm flashover model when the lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X "', and delta I" < delta I ', the lightning resistance level threshold of the composite cross arm is known to be between I ' "and I";
s35: step S33 and step S34 are circulated, the amplitude of lightning current is adjusted until the corresponding lightning current amplitude I when the composite cross arm flashover model is just obtained, and the induced lightning voltage U of the corresponding phase is calculated X 。
Preferably, the method for establishing the 10kV power supply model in the step S1 is as follows:
adopting a three-phase alternating current voltage source with rated voltage of 10kV, selecting ACSOURCE in ATP-EMTP software, setting the voltage source as 3 phases by default as a single-phase grounded 50Hz voltage source after double-click opening, inputting voltage amplitude 10000 v2=14142V, and searching SPLITTER phase separation module in ATP-EMTP software to obtain three-phase voltages USA, USB and USC at power output nodes.
Preferably, the method for establishing the lightning current model in the step S1 is as follows:
by adopting a Heidler model in ATP-EMTP software, a lightning voltage waveform defaulting to 1.2/50 mu s after double-click opening needs to set parameters: the lightning Current mode is selected such that t_f=2.6e-6 s, tau (37% im) =5e-5 s, and the amplitude is set to-30000A. The lightning channel wave impedance is 300 omega and is modeled by a 300 omega resistive element.
Preferably, the method for establishing the induced lightning overvoltage model in the step S1 is as follows:
the induced lightning voltage for a line conductor without overhead lightning conductor can be calculated as follows:
X＝A,B,C；
U X the induced lightning voltage value of the X phase is V; h dX The height of the X-phase lead from the ground is m; s is S X The horizontal distance between the lightning stroke point and the X-phase lead is m; i is the lightning current amplitude, A; k' is a coefficient;
the FORTRAN element in the TACS module is found in the ATP-EMTP, the element type is set to 88, namely an Inside mode, numbers or expressions are input in a text box of the FORTRAN expression, and then the output node OUT is named; the X-phase requires the provision of 3 FORTRAN elements, hd_ X, S _x and uil_x, respectively.
Preferably, the method for establishing the line and tower model in the step S1 is as follows:
selecting an LCC line Model in ATP-EMTP software, opening the Model page, selecting an overhead line, checking 3 phases, and checking a skin effect; selecting JMARti in the model type, and checking Use default fitting for automatic adaptation; setting the earth resistivity as 100 omega m in standard data, and setting the line length as 50m, namely the tower span;
the electric pole adopts a multi-wave impedance model, and the wave impedance of the electric pole tower is as follows:
h is the average height of the electric pole, m; r is the equivalent radius of the electric pole, m;wherein a is the maximum width of the electric pole of the section to be calculated, and b is the minimum width of the electric pole of the section to be calculated.
Preferably, the method for establishing the composite cross arm flashover model in the step S1 is as follows:
in the ATP-EMTP software, a model formed by TACS and a MODELS module is used for simulating the composite cross arm, the MODELS module is programmed, when the leading development length L is more than or equal to the insulation distance d of the composite cross arm, flashover occurs, and a model switch is closed;
preferably, the procedure for programming the MODELS is:
firstly, setting model parameters k and E0 and the length d of a cross arm, wherein k represents a pilot speed development coefficient, and E0 represents the minimum field strength of pilot development;
the model automatically measures the voltage of the nodes at two ends of the composite cross arm, and the voltages are input into UP and UN;
parameter initialization FLASH=0, the switches at two ends of the cross arm are disconnected, voltage U=UP-UN at two ends of the composite cross arm is calculated, field intensity E is calculated, whether E is larger than the minimum field intensity E0 of leading development is judged, and if the E is larger than E0, the leading initial development condition is met;
and then calculating the pilot development length L by a rectangular integration method, judging whether L is greater than or equal to the length d of the cross arm, if L is greater than or equal to d, indicating that the pilot development is finished, the cross arm is flashover, outputting FLASH=1, and closing the switch.
Preferably, the method for establishing the distribution transformer model in the step S1 is as follows:
the distribution transformer is modeled according to the inlet capacitance when calculating lightning impulse, and the formula for calculating the inlet capacitance is as follows:
wherein S is TN The transformer is of three-phase capacity, MVA; K. n is the fitting coefficient, respectively.
Preferably, the method for establishing the distribution line lightning arrester model in the step S1 is as follows: the input parameters of the MOV module in the ATP-EMTP software can simulate the volt-ampere characteristic of the lightning arrester, the input reference voltage is 34000V which is 2 times of rated voltage in the MOV module, then the data points of the volt-ampere characteristic curve of the lightning arrester are input, and the MOV module automatically generates a corresponding lightning arrester model.
The beneficial effects of the invention are as follows: the invention provides a 10kV distribution network composite cross arm lightning protection simulation method, and provides a 10kV line lightning protection model with complete structure and accurate calculation, which comprises the following steps of; the lightning current model, the induction lightning overvoltage model, the line and tower model, the composite cross arm flashover model, the distribution transformer model, the 10kV power supply model and the distribution line lightning arrester model which are connected with each other can simulate the condition that the composite cross arm suffers lightning overvoltage in the distribution line, so that convenience is provided for calculating the lightning resistance level of the composite cross arm and researching the lightning protection performance of the composite cross arm. When the lightning-resistant level is a lightning strike line, the maximum current amplitude value (kA) of which the insulation is not as high as possible or the minimum lightning current amplitude value (kA) capable of causing the insulation flashover is insulated. The invention adopts the pilot development method criterion which is an advanced insulation flashover criterion, and can more accurately simulate the flashover process of the composite cross arm.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Like elements or portions are generally identified by like reference numerals throughout the several figures. In the drawings, elements or portions thereof are not necessarily drawn to scale.
FIG. 1 is a model diagram constructed in accordance with the present invention;
FIG. 2 is a programming flow diagram of a composite cross arm flashover model;
FIG. 3 is a flow chart of the lightning protection level of the composite cross arm of the present invention;
FIG. 4 is a three-phase voltage waveform diagram of the composite cross arm at a lightning current amplitude of 40.0 kA;
FIG. 5 is a three-phase voltage waveform of the composite cross arm at a lightning current amplitude of 39.9kA.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be understood that the terms "comprises" and "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in the present specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
As shown in FIG. 1, the lightning protection simulation method for the composite cross arm of the 10kV distribution network comprises the following steps:
s1: a lightning current model, an induced lightning overvoltage model, a line and tower model, a composite cross arm flashover model, a distribution transformer model, a 10kV power supply model and a distribution line lightning arrester model are built in ATP-EMTP software;
as shown in fig. 1, the method for establishing the 10kV power supply model is as follows:
adopting a three-phase alternating current voltage source with rated voltage of 10kV, selecting ACSOURCE in ATP-EMTP software, setting the voltage source as 3 phases by default as a single-phase grounded 50Hz voltage source after double-click opening, inputting voltage amplitude 10000 v2=14142V, and searching a SPLITTER phase splitting module in ATP-EMTP software to obtain three-phase voltages USA, USB and USC at a power output node for calculating the following induced lightning overvoltage.
The method for establishing the lightning current model comprises the following steps:
by adopting a Heidler model in ATP-EMTP software, a lightning voltage waveform defaulting to 1.2/50 mu s after double-click opening needs to set parameters: the lightning Current mode is selected, let Tf=2.6E-6 s, tau (37%im) =5E-5 s, and the amplitude is set to-30000A, so that the negative polarity lightning Current waveform with the amplitude of 30kA of 2.6/50 mu s can be approximately simulated. The lightning channel wave impedance is 300 omega and is modeled by a 300 omega resistive element. The name of the output node of the Heidler model is set as I_LEI, and the output node is used for the next calculation of the induced lightning overvoltage.
The method for establishing the induction lightning overvoltage model comprises the following steps: the induced lightning voltage for a line conductor without overhead lightning conductor can be calculated as follows:
X＝A,B,C；
U X the induced lightning voltage value of the X phase is V; h dX The height of the X-phase lead from the ground is m; s is S X The horizontal distance between the lightning stroke point and the X-phase lead is m; i is the lightning current amplitude, A; k' is a coefficient, taking 25.
The FORTRAN element in the TACS module is found in the ATP-EMTP, the element type is set to 88, namely an Inside mode, numbers or expressions are input in a text box of the FORTRAN expression, and then the output node OUT is named; the X phase requires the provision of 3 FORTRAN elements, hd_ X, S _x and uil_x, respectively, where x=a, B, C, respectively, representing A, B, C three phases.
Taking phase B as an example, the heights Hd_B (i.e. H) of the phase B from the lightning point are input respectively dB ) And a horizontal distance S_B (i.e. S B ) Then inputting the expression of phase B induced lightning overvoltage in uil_b:
25*I_LEI*log(Hd_B/S_B+sqrt((Hd_B/S_B)**2+1))
both Hd_B and S_B are connected to UIL_B by a dashed line (reference), indicating that they are in logical precedence relationship rather than circuit connection relationship. Finally, the UIL_B just calculated and the power supply voltage USB which is obtained previously are added together through a summation element, and the final B-phase induction lightning overvoltage UILS_B is obtained. Uils_b and USB are input to the summing element and uils_b is output from the summing element.
And finally, selecting a voltage source through a TACSSOUR element in the TACS module, and inputting UILS_B into the Name of a TACS node to be connected to one end of a B-phase composite cross arm of a No. 0 pole tower in a line model, thereby realizing the condition that the composite cross arm suffers induced lightning overvoltage. A. C is the same.
The method for establishing the line and tower model comprises the following steps:
the JMARti frequency characteristic overhead line model is adopted, and the model is a line model commonly adopted in lightning protection calculation at present. The soil resistivity is 100 omega m, the total length of the line is 10km, and the tower span is 50m. In order to improve the accuracy of the investigation and reduce the influence of the reflected wave, a relatively long line having the same characteristics as the line under investigation is connected at the line end as an elimination effect of the reflected wave.
Selecting an LCC line Model in ATP-EMTP software, opening the Model page, selecting an overhead line, checking 3 phases, and checking a skin effect; selecting JMARti in the model type, and checking Use default fitting for automatic adaptation; the ground resistivity is set to be 100 Ω×m in standard data, and the line length is set to be 50m, namely the tower span.
After the Model page is set, clicking the Data page, and inputting the inner diameter (cm), the outer diameter (cm), the direct current resistance (omega/km), the inter-phase horizontal distance (m) and the ground clearance (m) of each phase of conducting wire of the overhead line.
After the setting is finished, the Run ATP button is clicked, and after the running is completed, the circuit model is set.
The electric pole adopts a multi-wave impedance model, and the grounding resistance is 20Ω. The wave speed was taken as 300 m/mu s. The impedance of the small bus and the connecting line wave (connected to the distribution transformer) is uniformly selected to be 150 omega with the larger value and 20m in length according to conservation. A standard 15m reinforced concrete pole is adopted, a single-circuit wiring structure is adopted, the diameter of the pole tip is 0.19m, the root diameter is 0.39m, and the underground burial depth is 2.3m.
The tower wave impedance is:
h is the average height of the electric pole, m; r is the equivalent radius of the electric pole, m;wherein a is the maximum width of the electric pole of the section to be calculated, and b is the minimum width of the electric pole of the section to be calculated.
After the wave impedance of the cement tower (206 Ω in this case) is calculated, a linezt—1 wave impedance element is selected from ATP, and the value and length of the wave impedance are input, with the length being the height of the cement tower. The ground resistance is typically 10 to 30Ω, which is related to the soil properties, here 20Ω.
The composite cross arm flashover model and flashover criteria have great influence on the accuracy of the calculation result of the lightning resistance level of the power transmission line, and the establishment of an accurate insulation flashover model is vital.
The pilot development method is based on the long air gap discharge physical process, and whether the flashover occurs or not is judged through the pilot development length. When the leading development length L is more than or equal to the composite cross arm insulation distance d, flashover occurs, and the model switch is closed. The recommended lead development speed formula in 1991 CIGRE report was adopted:
wherein: e (E) 0 Representing the lowest field strength, negative polarity E of the leading development 0 Taking 670kV/m; k represents the leading speed development coefficient, and the negative polarity k is 1×10 -6 m 2 v -2 s -1 。
The method for establishing the composite cross arm flashover model comprises the following steps:
in the ATP-EMTP software, a model formed by TACS and MODELS modules is used for simulating the composite cross arm, the MODELS is programmed, when the leading development length L is greater than or equal to the insulation distance d of the composite cross arm, flashover occurs, and a model switch is closed. As shown in fig. 2, the procedure for programming the MODELS is:
firstly, setting model parameters k and E0 and the length d of a cross arm, wherein k represents a pilot speed development coefficient, and E0 represents the minimum field strength of pilot development;
the model automatically measures the voltage of the nodes at two ends of the composite cross arm, and the voltages are input into UP and UN;
parameter initialization FLASH=0, the switches at two ends of the cross arm are disconnected, voltage U=UP-UN at two ends of the composite cross arm is calculated, field intensity E is calculated, whether E is larger than the minimum field intensity E0 of leading development is judged, and if the E is larger than E0, the leading initial development condition is met;
and then calculating the pilot development length L by a rectangular integration method, judging whether L is greater than or equal to the length d of the cross arm, if L is greater than or equal to d, indicating that the pilot development is finished, the cross arm is flashover, outputting FLASH=1, and closing the switch.
The method for establishing the distribution transformer model comprises the following steps:
the capacity of the distribution transformer is 500kVA, referring to electric power system overvoltage calculation, the distribution transformer is modeled according to the inlet capacitance when calculating lightning impulse, and the formula for calculating the inlet capacitance is as follows:
wherein S is TN The transformer is of three-phase capacity, MVA; K. n is the fitting coefficient, respectively. Depending on the system voltage rating, k=350, n=3 are considered temporarily for the power distribution system, respectively.
| Voltage class/kV | K | n |
| 10/35 | 350 | 3 |
| 110/220 | 540 | 3 |
| 500 or more | 940 | 4 |
The method for establishing the distribution line lightning arrester model comprises the following steps: the vast majority of lightning arresters adopted in the current 10kV power distribution network are nominal discharge current 5kA series products, and typical nominal discharge current is 5kA, YH5WS5-17/50W, and rated voltage of the lightning arresters is 17kV. The input parameters of the MOV module in the ATP-EMTP software can simulate the volt-ampere characteristic of the lightning arrester, the input reference voltage is 34000V which is 2 times of rated voltage in the MOV module, then data points (voltage and current) of the volt-ampere characteristic curve of the lightning arrester are input, and the MOV module automatically generates a corresponding lightning arrester model.
S2: sequentially connecting a 10kV power supply model, a line and tower model, a distribution transformer model and a distribution line lightning arrester model; and connecting the composite cross arm flashover model, the lightning current model and the induced lightning overvoltage model with the line and the tower model.
S3: as shown in fig. 3, the magnitude of lightning current amplitude in the lightning current model is adjusted, the magnitude of corresponding induced lightning voltage of three phases is calculated, whether flashover occurs in the corresponding composite cross arm flashover model is observed, if flashover does not occur, the magnitude of lightning current in the lightning current model is increased until the composite cross arm flashover model just occurs, the magnitude of corresponding induced lightning current magnitude is recorded, and then the magnitude of the induced lightning current is the lightning-resistant level threshold value of the corresponding composite cross arm. Step S3 further comprises the steps of:
s31: setting the amplitude I of the initial lightning current 0 Calculating to obtain corresponding induced lightning voltage U X0 ，X＝A,B,C；
S32: simulating the lightning-proof level threshold of the composite cross arm of the corresponding phase if the lightning-proof level threshold is the lightning discharge current I 0 When no flashover occurs in the lower corresponding composite cross arm flashover model, increasing delta I each time when adjusting lightning current until the flashover occurs in the composite cross arm flashover model when the lightning current is increased to the lightning current I ', and recording the lightning current I' at the moment and the corresponding calculated induced lightning voltage U of the corresponding phase X '；
Conversely, if it is in the lightning current I 0 When the flashover occurs in the lower corresponding composite cross arm flashover model, reducing delta I each time when adjusting lightning current until flashover does not occur in the composite cross arm flashover model when reducing to lightning current I ', and recording the lightning current I' at the moment and the corresponding calculated induced lightning voltage U of the corresponding phase X '；
S33: each time delta I ' is reduced on the basis of lightning current I ', no flashover occurs in the composite cross arm flashover model until lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X If delta I ' < delta I, the lightning resistance level threshold of the composite cross arm is between I ' and I ';
otherwise, delta I ' is increased each time on the basis of lightning current I ', and the flashover of the composite cross arm flashover model occurs until the lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X If delta I ' < delta I, the lightning resistance level threshold of the composite cross arm is between I ' and I ';
s34: each time delta I ' is increased on the basis of the lightning current I ' obtained in the step S33 until the composite cross arm flashover model is flashover when the lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X "', and ΔI" < ΔI'; then the lightning resistance level threshold of the composite cross arm is known to be between I 'and I';
otherwise, the delta I ' is reduced each time on the basis of the lightning current I ' obtained in the step S33 until the lightning current I ' is adjustedNo flashover occurs and the induced lightning voltage U of the corresponding phase is calculated X "', and delta I" < delta I ', the lightning resistance level threshold of the composite cross arm is known to be between I ' "and I";
s35: step S33 and step S34 are circulated, the amplitude of lightning current is adjusted until the lightning current I corresponding to the moment that the composite cross arm flashover model is just obtained, and the induced lightning voltage U of the corresponding phase is calculated X 。
Aiming at the defect of lightning protection performance research of a compound cross arm of a distribution network, the technical problem to be solved by the model is to provide a 10kV line lightning protection simulation method with complete structure and accurate calculation, which can simulate the condition that the compound cross arm suffers lightning overvoltage in a distribution line, thereby providing convenience for calculating the lightning resistance level of the compound cross arm and researching the lightning protection performance of the compound cross arm. The pilot development method criterion is an advanced insulation flashover criterion, and can simulate the flashover process of the composite cross arm more accurately.
Fig. 1 is a 10kV line composite cross arm inductive lightning model, in which 3 towers are arranged in total, the left side of the line is a 10kV power supply, and the right side is a distribution transformer model. The line length is about 10km. Setting the lightning current amplitude to 39kA, setting the horizontal distance between the lightning strike and the phase B of the line to 30m, running simulation to obtain a three-phase induction lightning overvoltage waveform of the composite cross arm, finding that no flashover occurs, taking 1kA as an interval, increasing the lightning current amplitude to 40kA, and when the lightning current amplitude is increased to 40kA, the voltage waveform is shown in figure 4, and as can be seen from figure 4, the voltage of the phase B is 0 at 24us, the flashover happens just, and A, C two phases do not occur. When the lightning current amplitude of 0.1kA is increased to 39.9kA, as shown in FIG. 5, the three-phase induction lightning overvoltage waveform of the composite cross arm is obtained, and when the lightning current amplitude of 0.1kA is increased to 39.9kA, the lightning current of the composite cross arm is judged to be 39.9kA. If the accuracy is still required to be improved, the downward test can be continued, and the description is omitted in this embodiment.
The present invention is not limited to the specific embodiments described above, but is to be construed as being limited to the preferred embodiments of the present invention, and any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention are intended to be included in the scope of the present invention.
Claims (9)
1. A10 kV distribution network composite cross arm lightning protection simulation method is characterized by comprising the following steps of: the method comprises the following steps:
s1: a lightning current model, an induced lightning overvoltage model, a line and tower model, a composite cross arm flashover model, a distribution transformer model, a 10kV power supply model and a distribution line lightning arrester model are built in ATP-EMTP software;
s2: sequentially connecting a 10kV power supply model, a line and tower model, a distribution transformer model and a distribution line lightning arrester model; connecting the composite cross arm flashover model, the lightning current model and the induced lightning overvoltage model with the line and the tower model;
s3: adjusting the magnitude of lightning current amplitude in the lightning current model, calculating to obtain the magnitude of three-phase corresponding induced lightning voltage, observing whether flashover occurs in the corresponding composite cross arm flashover model, if flashover does not occur, increasing the magnitude of lightning current in the lightning current model until the composite cross arm flashover model just occurs, and recording the magnitude of the corresponding induced lightning current, wherein the magnitude of the induced lightning current is the lightning-resistant level threshold value of the corresponding composite cross arm; the step S3 further includes the steps of:
s31: setting the amplitude I of the initial lightning current 0 Calculating to obtain corresponding induced lightning voltage U X0 ，X＝A,B,C；
S32: if the lightning current I is when the lightning-resistant level threshold value of the composite cross arm of the corresponding phase is simulated 0 When no flashover occurs in the lower corresponding composite cross arm flashover model, delta I is increased each time when lightning current is regulated until flashover occurs in the composite cross arm flashover model when the lightning current is increased to the lightning current I ', and then the lightning current amplitude I' and the corresponding calculated induced lightning voltage U of the corresponding phase are recorded X '；
On the contrary, if it isLightning current I 0 When the flashover occurs in the lower corresponding composite cross arm flashover model, delta I is reduced each time when lightning current is regulated until flashover does not occur in the composite cross arm flashover model when lightning current I 'is reduced, and then the lightning current amplitude I' at the moment and the corresponding calculated induced lightning voltage U of the corresponding phase are recorded X '；
S33: each time delta I ' is reduced on the basis of lightning current I ', no flashover occurs in the composite cross arm flashover model until lightning current I ' is regulated, and induced lightning voltage U of a corresponding phase is calculated X ", and DeltaI'<Δi, then the lightning level threshold of the composite cross arm is known to be between I "and I';
otherwise, delta I ' is increased each time on the basis of lightning current I ', and the flashover of the composite cross arm flashover model occurs until lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X ", and DeltaI'<Δi, then the lightning level threshold of the composite cross arm is known to be between I' and I ";
s34: each time delta I ' is added on the basis of the lightning current I ' obtained in the step S33 until the composite cross arm flashover model is flashover when the lightning current I ' is regulated, and the induced lightning voltage U of the corresponding phase is calculated X "', and DeltaI'<Δi'; then the lightning resistance level threshold of the composite cross arm is known to be between I 'and I';
conversely, the delta I ' is reduced each time on the basis of the lightning current I ' obtained in the step S33 until no flashover occurs in the composite cross arm flashover model when the lightning current I ' is adjusted, and the induced lightning voltage U of the corresponding phase is calculated X "', and DeltaI'<Δi ', the lightning tolerance level threshold of the composite cross arm is known to be between I' "and I";
s35: step S33 and step S34 are circulated, the amplitude of lightning current is adjusted until the corresponding lightning current amplitude I when the composite cross arm flashover model is just obtained, and the induced lightning voltage U of the corresponding phase is calculated X 。
2. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the 10kV power supply model in the step S1 comprises the following steps:
adopting a three-phase alternating current voltage source with rated voltage of 10kV, selecting ACSOURCE in ATP-EMTP software, setting the voltage source as 3 phases by default as a single-phase grounded 50Hz voltage source after double-click opening, and inputting voltage amplitudeAnd searching the SPLITTER phase separation module in ATP-EMTP software to obtain three-phase voltages USA, USB and USC at the power output node.
3. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the lightning current model in the step S1 is as follows:
by adopting a Heidler model in ATP-EMTP software, a lightning voltage waveform defaulting to 1.2/50 mu s after double-click opening needs to set parameters: the lightning Current mode is selected, let Tf=2.6E-6 s, tau (37%im) =5E-5 s, the amplitude is set to-30000A; the lightning channel wave impedance is 300 omega and is modeled by a 300 omega resistive element.
4. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the induced lightning overvoltage model in the step S1 is as follows:
the induced lightning voltage for a line conductor without overhead lightning conductor can be calculated as follows:
U X the induced lightning voltage value of the X phase is V; h dX The height of the X-phase lead from the ground is m; s is S X The horizontal distance between the lightning stroke point and the X-phase lead is m; i is the lightning current amplitude, A; k' is a coefficient;
the FORTRAN element in the TACS module is found in the ATP-EMTP, the element type is set to 88, namely an Inside mode, numbers or expressions are input in a text box of the FORTRAN expression, and then the output node OUT is named; the X-phase requires the provision of 3 FORTRAN elements, hd_ X, S _x and uil_x, respectively.
5. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the line and tower model in the step S1 is as follows:
selecting an LCC line Model in ATP-EMTP software, opening the Model page, selecting an overhead line, checking 3 phases, and checking a skin effect; selecting JMARti in the model type, and checking Use default fitting for automatic adaptation; setting the earth resistivity as 100 omega m in standard data, and setting the line length as 50m, namely the tower span;
the electric pole adopts a multi-wave impedance model, and the wave impedance of the electric pole tower is as follows:
h is the average height of the electric pole, m; r is the equivalent radius of the electric pole, m;wherein a is the maximum width of the electric pole of the section to be calculated, and b is the minimum width of the electric pole of the section to be calculated.
6. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the composite cross arm flashover model in the step S1 comprises the following steps:
in the ATP-EMTP software, a model formed by the TACS and the MODELS module is used for simulating the composite cross arm, the MODELS module is programmed, when the leading development length L is more than or equal to the insulation distance d of the composite cross arm, flashover occurs, and a model switch is closed.
7. The 10kV distribution network composite cross arm lightning protection simulation method is characterized by comprising the following steps of: the procedure for programming MODELS is as follows:
firstly, setting model parameters k and E0 and the length d of a cross arm, wherein k represents a pilot speed development coefficient, and E0 represents the minimum field strength of pilot development;
the model automatically measures the voltage of the nodes at two ends of the composite cross arm, and the voltages are input into UP and UN;
parameter initialization FLASH=0, the switches at two ends of the cross arm are disconnected, voltage U=UP-UN at two ends of the composite cross arm is calculated, field intensity E is calculated, whether E is larger than the minimum field intensity E0 of leading development is judged, and if the E is larger than E0, the leading initial development condition is met;
and then calculating the pilot development length L by a rectangular integration method, judging whether L is greater than or equal to the length d of the cross arm, if L is greater than or equal to d, indicating that the pilot development is finished, the cross arm is flashover, outputting FLASH=1, and closing the switch.
8. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the distribution transformer model in the step S1 is as follows:
the distribution transformer is modeled according to the inlet capacitance when calculating lightning impulse, and the formula for calculating the inlet capacitance is as follows:
wherein S is TN The transformer is of three-phase capacity, MVA; K. n is the fitting coefficient, respectively.
9. The 10kV distribution network composite cross arm lightning protection simulation method according to claim 1 is characterized by comprising the following steps: the method for establishing the distribution line lightning arrester model in the step S1 comprises the following steps: the input parameters of the MOV module in the ATP-EMTP software can simulate the volt-ampere characteristic of the lightning arrester, the input reference voltage is 34000V which is 2 times of rated voltage in the MOV module, then the data points of the volt-ampere characteristic curve of the lightning arrester are input, and the MOV module automatically generates a corresponding lightning arrester model.
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