CN112036005A - Method and device for calculating lightning induction voltage - Google Patents
Method and device for calculating lightning induction voltage Download PDFInfo
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Abstract
The invention discloses a method for calculating lightning induction voltage, which is suitable for a power distribution network system configured with an overhead ground wire, and comprises the following steps: establishing a lightning channel model on the overhead ground wire to calculate the induced voltage at a conductor port of the overhead ground wire; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth; and calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port of the overhead ground wire, and establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software so as to calculate the lightning induction voltage of the overhead ground wire. The invention also discloses a corresponding device, and by implementing the method, the influence of the lossy ground on the space electromagnetic coupling can be effectively considered, the lightning induced overvoltage of the overhead ground wire caused by the induced lightning can be more accurately calculated, and the method can be used for power distribution network construction and operation reference.
Description
Technical Field
The invention relates to the technical field of lightning induced overvoltage of a power system, in particular to a method and a device for calculating lightning induced voltage.
Background
With the steady development of our society, the urban construction has higher and higher requirements on the reliability of power supply. Lightning is one of the most prominent external factors responsible for distribution line failure. The distribution lines have more branches, large distribution density and low insulation level, so the lightning induced overvoltage sensing degree is high. According to statistics, the distribution network fault rate caused by lightning induction accounts for more than 70% of the total lightning stroke fault rate.
For a long time, the work of lightning protection of the line focuses on the protection of directly striking a high-voltage power transmission line by lightning, and relatively few researches on induced overvoltage of the power distribution line caused by induced lightning are carried out. Therefore, the research on the influence of the induction lightning on the fault of the distribution line needs to be enhanced, so that the effective protection on the transmission line can be realized, and the safety performance of a transmission system is improved. In the prior art, the EMTP (electromagnetic transient program) software can accurately consider the structural characteristics of a line and realize the calculation of the lightning induced overvoltage. However, in the process of implementing the invention, the inventor finds that the prior art has at least the following problems: the influence of the ground on the space electromagnetic coupling is not considered in the existing method, so that the calculated lightning induced overvoltage has a large error, and the calculation result is not accurate enough.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a device for calculating lightning induction voltage, which can effectively consider the influence of a lossy ground on space electromagnetic coupling, can calculate the lightning induction overvoltage of an overhead ground wire caused by induced lightning more accurately, and can be used for power distribution network construction and operation reference.
In order to achieve the above object, an embodiment of the present invention provides a method for calculating a lightning induction voltage, which is applicable to a power distribution network system configured with an overhead ground wire, and includes:
establishing a lightning channel model on the overhead ground wire;
calculating the induced voltage at the wire port of the overhead ground wire according to the lightning channel model; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth;
calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port;
and according to the equivalent voltage source of the wire port, establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software so as to calculate the lightning induction voltage of the overhead ground wire.
As an improvement of the above scheme, the calculating, according to the lightning channel model, an induced voltage at a conductor port of the overhead ground wire specifically includes:
analyzing the electric field distribution on the overhead ground wire according to the lightning channel model;
and calculating the line voltage drop on the overhead ground wire according to the electric field distribution on the overhead ground wire so as to calculate and obtain the induced voltage at the wire port of the overhead ground wire.
As an improvement of the above scheme, the lightning channel model on the overhead ground wire is represented by lightning current, specifically:
I(z',t)＝u(t-z'/vf)p(z')I(0,t-z'/v)；
wherein I (z', t) is lightning current in the lightning channel model; u (t-z'/v)f) Is a step function, p (z') is the current attenuation coefficient as a function of height; i (0, t-z'/v) is the propagation magnitude of the lightning current; v. offIs the speed of the upstream front; v is the propagation velocity of the current wave; z' is a height value.
As an improvement of the above scheme, the induced voltage at the wire port of the overhead ground wire is specifically expressed in the frequency domain as:
UindA(xA,ω)＝U0(xA,ω)-g0(jω)·Ug(xA,ω)；
wherein，UindA(xAω) is the conductor port x of the overhead earth wireAInduced voltage of (U)0(xAω) is a lossless component,
Ug(xAand, ω) is a lossy component,
g0(j ω) is a green's function that accounts for earth effects; x is the number ofAAnd xBRespectively the coordinates of the two ends of the conductor of the overhead earth wire, Ex(xAY, h, ω) and Ez(xB,y,0, ω) are the horizontal and vertical electric field components, By0For the horizontal magnetic field component, h is the height of the overhead ground wire.
As an improvement of the above scheme, the calculating an equivalent voltage source of the wire port according to the induced voltage of the wire port of the overhead ground wire specifically includes:
according to the wire port x of the overhead ground wireAInduced voltage, line drop and from another wire port xBAnd calculating the voltage source of the wire port by the following calculation formula according to the reflected voltage transmitted after the time delay tau:
UrA(t)＝UindA(xA,t)+UB(t-τ)+Z'·iB(t-τ)；
wherein, UrA(t) is the conductor port x of the overhead earth wireAA voltage source of (a); u shapeindA(xAAnd t) is the wire port x of the overhead earth wireAThe expression mode of the induced voltage in time frequency; u shapeB(t- τ) is said another wire port xBReflected voltage transmitted after time delay tau; z'. iB(t- τ) is the line pressure drop; z' is the characteristic impedance of the overhead line, iB(t- τ) is the wire port xBThe line current of (1);
converting a voltage source of a wire port of the overhead ground wire into an equivalent voltage source of the wire port:
wherein j is the number of phases.
The embodiment of the invention also provides a device for calculating the lightning induced voltage, which is suitable for a power distribution network system configured with an overhead ground wire, and comprises the following components:
the lightning channel model establishing module is used for establishing a lightning channel model on the overhead ground wire;
the port induced voltage calculation module is used for calculating the induced voltage at the wire port of the overhead ground wire according to the lightning channel model; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth;
the equivalent voltage source calculation module is used for calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port;
and the lightning induction voltage model establishing module is used for establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software according to the equivalent voltage source of the wire port so as to calculate the lightning induction voltage of the overhead ground wire.
As an improvement of the above scheme, the port induced voltage calculation module specifically includes:
the electric field distribution analysis unit is used for analyzing the electric field distribution on the overhead ground wire according to the lightning channel model;
and the port induced voltage calculation unit is used for calculating the line voltage drop on the overhead ground wire according to the electric field distribution on the overhead ground wire so as to calculate and obtain the induced voltage at the wire port of the overhead ground wire.
As an improvement of the above scheme, the lightning channel model on the overhead ground wire is represented by lightning current, specifically:
I(z',t)＝u(t-z'/vf)p(z')I(0,t-z'/v)；
wherein I (z', t) is lightning current in the lightning channel model; u (t-z'/v)f) Is a step function of the number of steps,p (z') is the current attenuation coefficient as a function of altitude; i (0, t-z'/v) is the propagation magnitude of the lightning current; v. offIs the speed of the upstream front; v is the propagation velocity of the current wave; z' is a height value.
As an improvement of the above scheme, the induced voltage at the wire port of the overhead ground wire is specifically expressed in the frequency domain as:
UindA(xA,ω)＝U0(xA,ω)-g0(jω)·Ug(xA,ω)；
wherein, UindA(xAω) is the conductor port x of the overhead earth wireAInduced voltage of (U)0(xAω) is a lossless component,
Ug(xAand, ω) is a lossy component,
g0(j ω) is a green's function that accounts for earth effects; x is the number ofAAnd xBRespectively the coordinates of the two ends of the conductor of the overhead earth wire, Ex(xAY, h, ω) and Ez(xBY,0, ω) are the horizontal and vertical electric field components, By0For the horizontal magnetic field component, h is the height of the overhead ground wire.
As an improvement of the above scheme, the equivalent voltage source calculation module is specifically configured to:
according to the wire port x of the overhead ground wireAInduced voltage, line drop and from another wire port xBAnd calculating the voltage source of the wire port by the following calculation formula according to the reflected voltage transmitted after the time delay tau:
UrA(t)＝UindA(xA,t)+UB(t-τ)+Z'·iB(t-τ)；
wherein, UrA(t) is the conductor port x of the overhead earth wireAA voltage source of (a); u shapeindA(xAAnd t) is the wire port x of the overhead earth wireAInduced electricity ofAn expression mode of pressing on time frequency; u shapeB(t- τ) is said another wire port xBReflected voltage transmitted after time delay tau; z'. iB(t- τ) is the line pressure drop; z' is the characteristic impedance of the overhead line, iB(t- τ) is the wire port xBThe line current of (1);
converting a voltage source of a wire port of the overhead ground wire into an equivalent voltage source of the wire port:
wherein j is the number of phases.
Compared with the prior art, the method and the device for calculating the lightning induced voltage disclosed by the invention have the advantages that the induced voltage at the wire port of the overhead ground wire is calculated and obtained by establishing the lightning channel model on the overhead ground wire; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth; and calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port of the overhead ground wire, and further establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software so as to calculate the lightning induction voltage of the overhead ground wire. The Bergeron model in EMTP is used for modeling a three-phase overhead line and an overhead ground wire line system, and the induced voltage of a lead port of the overhead ground wire can be calculated more accurately by establishing a lightning channel model and processing the induction effect of the damaged ground. The method adopts EMTP modeling to perform modeling simulation on lightning induced overvoltage of the overhead line with the overhead ground wire, is used for analyzing lightning induced overcurrent of the overhead ground wire, can test the lightning resistance level of the overhead line, verifies the reduction effect of the distribution line overhead ground wire on the lightning induced voltage, realizes the calculation modeling of the induced voltage of a complex network, and provides the construction and operation reference of the distribution network.
Drawings
Fig. 1 is a schematic step diagram of a method for calculating a lightning induction voltage according to an embodiment of the present invention;
fig. 2 is a schematic configuration diagram of an overhead ground wire according to a first embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a lightning induced voltage calculation apparatus according to a second embodiment of the present invention;
fig. 4 is a schematic structural diagram of another lightning induction voltage calculation apparatus according to a third embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic step diagram of a method for calculating a lightning induction voltage according to an embodiment of the present invention. The embodiment of the invention provides a method for calculating a lightning induction voltage, which is suitable for a power distribution network system configured with an overhead ground wire, and is implemented through steps S1 to S4:
s1, establishing a lightning channel model on the overhead ground wire;
s2, calculating the induced voltage at the lead port of the overhead ground wire according to the lightning channel model; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth;
s3, calculating an equivalent voltage source of the wire port according to the induced voltage of the wire port of the overhead ground wire;
and S4, establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software according to the equivalent voltage source of the wire port so as to calculate the lightning induction voltage of the overhead ground wire.
In the embodiment of the invention, a thunder channel model is established, the inductive effect of the lossy ground is processed, the inductive voltage of the wire port of the overhead ground wire can be accurately calculated, and then EMTP modeling is adopted to perform modeling simulation on the lightning induced overvoltage of the overhead ground wire. Under the condition of considering the influence of the lossy earth, the lightning overvoltage of the overhead line caused by the inductive lightning can be calculated more accurately, the protection effect of the overhead ground wire can be simulated, the lightning protection performance of the distribution line is improved by verifying the overhead ground wire, and the operation reliability of the distribution network is improved.
Specifically, in order to more clearly understand a specific calculation process of the lightning induction voltage of the power distribution network configured with the overhead ground wire in practical application, a detailed description is given below of a method for calculating the lightning induction voltage according to a first embodiment of the present invention.
Fig. 2 is a schematic configuration diagram of an overhead ground wire according to a first embodiment of the present invention. When the lightning strike is near the distribution line, the lightning current induces a high overvoltage on the conductor due to electromagnetic coupling, which may cause insulator flashover. In long distance lightning, the strike-back current is not affected by the ground structure. The electric field generated by the lightning channel is considered to be an independent external incident field. Although lightning is a random event, a predefined current in the lightning strike path is typically employed when evaluating induced transients in the ground structure. In engineering applications, the distribution of current in the lightning channel in space and time is determined based on the actually observed lightning strike-back characteristics (such as the channel bottom current and the speed of the ascending leader). When the induced voltage on the overhead line is analyzed, the physical characteristics of lightning strike-back can be faded, and the electromagnetic field of a near field or a far field is calculated quickly and effectively.
Assuming here that the lightning path is perpendicular to the ground and has no branches, the lightning path can be simulated using a transmission line model (TL model). The model is characterized by assuming that the waveform of the lightning current is linear and propagates upward at a fixed speed without attenuation. The soil medium is homogeneous and has a single dielectric constant and conductivity. In the model, the spatial distribution and the time variation of lightning current I (z', t) in the lightning channel are described by an analytical formula:
I(z',t)＝u(t-z'/vf)p(z')I(0,t-z'/v)；
wherein I (z', t) is lightning current in the lightning channel model; u (t-z'/v)f) Is a step function, p (z') is the current attenuation coefficient as a function of height; i (0, t-z'/v) is the propagation magnitude of the lightning current; v. offIs the speed of the upstream front; v is the propagation velocity of the current wave; z' is a height value on a spatial coordinate system.
It should be noted that the lightning channel model on the overhead ground wire is represented by lightning current, and the specific construction method of the lightning channel model may also be a construction method of a lightning channel model in the prior art, which is not limited herein.
And further, calculating the induced voltage at the wire port of the overhead ground wire according to the lightning channel model. In the embodiment of the present invention, step S2 specifically includes steps S21 and S22:
s21, analyzing the electric field distribution on the overhead ground wire according to the lightning channel model;
and S22, calculating the line voltage drop on the overhead ground wire according to the electric field distribution on the overhead ground wire so as to calculate and obtain the induced voltage at the lead port of the overhead ground wire.
Specifically, according to maxwell's equation, the incident electric field on the lead of the overhead ground wire is the sum of the channel radiation field and the ground reflection field, and the total field induced by the line is equal to the incident electric field plus the scattered field responded by the line. The induced voltage u (x, t) on the overhead conductor is thus the scattered voltage us(x, t) and incident Voltage uiSum of (x, t):
u(x,t)＝us(x,t)+ui(x,t)
wherein the content of the first and second substances,
is the incident vertical electric field and the electric field,
is a scattering vertical electric field; h is the height of the overhead ground wire, where x represents the horizontal displacement on the spatial coordinate system, z represents the height value on the spatial coordinate system, and t is time.
Two transmission line equations are introduced by integrating maxwell's equations along the path and expressed in terms of the scattering voltage. The two transmission line equations are:
wherein Z 'is the characteristic impedance of the overhead ground wire and Y' is the admittance of the overhead ground wire;
is the incident horizontal electric field.
Substituting the induced voltage u (x, t) on the overhead ground wire into the two transmission line equations, and further solving to obtain a conductor port x of the overhead ground wireAThe induced voltage at (c). The wire port xAThe induced voltage at (a) is specifically represented in the frequency domain as:
UindA(xA,ω)＝U0(xA,ω)-g0(jω)·Ug(xA,ω)；
wherein, UindA(xAω) is the conductor port x of the overhead earth wireAInduced voltage of (U)0(xAω) is a lossless component,
Ug(xAand, ω) is a lossy component,
g0(j ω) is a consideration of the earth shadowA green function of sound; x is the number ofAAnd xBRespectively the coordinates of the two ends of the conductor of the overhead earth wire, Ex(xAY, h, ω) and Ez(xBY,0, ω) are the horizontal and vertical electric field components, By0Is the horizontal magnetic field component, h is the height of the overhead ground wire; y is the horizontal displacement on the space coordinate system; ω is a frequency domain parameter.
According to the same calculation method, another conductor port x of the overhead ground wire can be calculatedBInduced voltage U ofindB(xB,ω)。
It should be noted that the induced voltage at one end of the line forms a delayed reflected voltage at the other end. I.e. at the conductor port x of the overhead earth wireAThere will be another wire port xBReflected voltage U transmitted after time delay tauB(t- τ); conductor port x in overhead ground wireBThere will be another wire port xAReflected voltage U transmitted after time delay tauA(t-τ)。
Where, the delay τ is L/c, L represents the conductor length of the overhead ground wire, and c represents the speed of light.
Further, a power supply U at one end of the liner(t) inducing a voltage U from the local terminalindAnd (x, omega), the line voltage drop and the reflected voltage transmitted after the delay tau (tau is L/c) at the other end. Therefore, the calculating an equivalent voltage source of the wire port according to the induced voltage of the wire port of the overhead ground wire specifically includes:
according to the wire port x of the overhead ground wireAInduced voltage U ofindA(xAω), line drop and x from another wire portBReflected voltage U transmitted after time delay tauB(t- τ) calculating the wire port x by the following calculation formulaAVoltage source (c):
UrA(t)＝UindA(xA,t)+UB(t-τ)+Z'·iB(t-τ)；
wherein, UrA(t) is the conductor port x of the overhead earth wireAA voltage source of (a); z'. iB(t-τ) Is the line pressure drop; z' is the characteristic impedance of the overhead line, iB(t- τ) is the wire port xBThe line current of (1). U shapeindA(xAAnd t) is the wire port x of the overhead earth wireAThe expression mode of the induced voltage in time frequency.
According to the same calculation mode, the wire port x can be obtained by calculationBVoltage source (c):
UrB(t)＝Uind(-xB,t)+UA(t-τ)+Z'·iA(t-τ)。
further, considering the lossy effect of propagation above the lossy ground on the electric field, the incident field generated by the back shock can be replaced by two equivalent sources. Converting a voltage source of a wire port of the overhead ground wire into an equivalent voltage source of the wire port to obtain:
where j is the number of phases, and the inter-phase distances of the wires are ignored here.
And according to the equivalent voltage source of the wire port, establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software, and calculating the overall lightning induction voltage of the overhead ground wire. It should be noted that, the process of inputting the EMPT software for modeling according to the equivalent voltage source of the wire port may adopt a modeling method in the prior art, and is not limited herein.
Voltage source U at two ends of overhead linerAAnd UrBThe calculation of (a) is realized by writing the MODELS language in the EMTP. The developed model can handle multiple phase circuits. Since zero sequence systems are the most common, usually two phases are sufficient. Thus, a phase conductor may be combined to be considered one conductor, while a ground or neutral conductor may be the other conductor, or splitIs a multi-phase conductor. The circuit may be connected to any component in the ATP, may connect a load, and allows multiple line segments to be connected.
Compared with the traditional ATP/EMTP inductive lightning calculation model and an inductive lightning calculation simplified formula, the lightning induced overvoltage model provided by the embodiment of the invention considers the influence of electromagnetic coupling on adjacent lines, applies the deformed Bergeron model, develops a new application scene, is applied to the influence of electromagnetic coupling of a three-phase line and an overhead ground wire, adds the influence of a lossy ground on the induced voltage of a wire port on the overhead wire, and considers the influence of an electric field of a lightning channel on the whole section of line. An ATP model unit may contain a large number of overhead lines, each line may be composed of a plurality of units, the length of the line may be 1-3km, which depends on the ground resistivity, and the longer line needs to take into account the loss of the line. The invention can realize the modeling simulation of a more complex circuit network, has more accurate result and is a good compromise between the accuracy and the complexity based on measurable parameters. The establishment of the model is beneficial to realizing the full-coverage modeling analysis of the power distribution network, the specific application range of the overhead ground wire is planned, the technical standard and design are formulated, and a new simulation means is provided for the lightning protection work.
The embodiment of the invention provides a method for calculating lightning induction voltage, which comprises the steps of establishing a lightning channel model on an overhead ground wire to calculate and obtain the induction voltage at a lead port of the overhead ground wire; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth; and calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port of the overhead ground wire, and further establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software so as to calculate the lightning induction voltage of the overhead ground wire. The Bergeron model in EMTP is used for modeling a three-phase overhead line and an overhead ground wire line system, and the induced voltage of a lead port of the overhead ground wire can be calculated more accurately by establishing a lightning channel model and processing the induction effect of the damaged ground. The method adopts EMTP modeling to perform modeling simulation on lightning induced overvoltage of the overhead line with the overhead ground wire, is used for analyzing lightning induced overcurrent of the overhead ground wire, can test the lightning resistance level of the overhead line, verifies the reduction effect of the distribution line overhead ground wire on the lightning induced voltage, realizes the calculation modeling of the induced voltage of a complex network, and provides the construction and operation reference of the distribution network.
Fig. 3 is a schematic structural diagram of a lightning induced voltage calculation apparatus according to a second embodiment of the present invention. The embodiment of the present invention provides a lightning induction voltage calculation apparatus 20, which is suitable for a power distribution network system configured with an overhead ground wire, and includes:
a lightning channel model establishing module 21, configured to establish a lightning channel model on the overhead ground wire;
a port induced voltage calculation module 22, configured to calculate an induced voltage at a conductor port of the overhead ground wire according to the lightning channel model; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth;
the equivalent voltage source calculating module 23 is configured to calculate an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port;
and the lightning induction voltage model establishing module 24 is used for establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software according to the equivalent voltage source of the wire port so as to calculate the lightning induction voltage of the overhead ground wire.
In the embodiment of the invention, a thunder channel model is established, the inductive effect of the lossy ground is processed, the inductive voltage of the wire port of the overhead ground wire can be accurately calculated, and then EMTP modeling is adopted to perform modeling simulation on the lightning induced overvoltage of the overhead ground wire. Under the condition of considering the influence of the lossy earth, the lightning overvoltage of the overhead line caused by the inductive lightning can be calculated more accurately, the protection effect of the overhead ground wire can be simulated, the lightning protection performance of the distribution line is improved by verifying the overhead ground wire, and the operation reliability of the distribution network is improved.
As a preferred embodiment, the lightning channel model on the overhead ground wire is represented by lightning current, specifically:
I(z',t)＝u(t-z'/vf)p(z')I(0,t-z'/v)；
wherein I (z', t) is lightning current in the lightning channel model; u (t-z'/v)f) Is a step function, p (z') is the current attenuation coefficient as a function of height; i (0, t-z'/v) is the propagation magnitude of the lightning current; v. offIs the speed of the upstream front; v is the propagation velocity of the current wave; z' is a height value.
As a preferred embodiment, the port induced voltage calculation module 22 specifically includes:
an electric field distribution analyzing unit 221, configured to analyze electric field distribution on the overhead ground wire according to the lightning channel model;
the port induced voltage calculating unit 222 is configured to calculate a line voltage drop on the overhead ground wire according to the electric field distribution on the overhead ground wire, so as to calculate an induced voltage at a conductor port of the overhead ground wire.
Specifically, the induced voltage at the wire port of the overhead ground wire is specifically represented in the frequency domain as:
UindA(xA,ω)＝U0(xA,ω)-g0(jω)·Ug(xA,ω)；
wherein, UindA(xAω) is the conductor port x of the overhead earth wireAInduced voltage of (U)0(xAω) is a lossless component,
Ug(xAand, ω) is a lossy component,
g0(j ω) is a green's function that accounts for earth effects; x is the number ofAAnd xBRespectively the coordinates of the two ends of the conductor of the overhead earth wire, Ex(xA,y, h, ω) and Ez(xB,y,0, ω) are the horizontal and vertical electric field components, By0For the horizontal magnetic field component, h is the height of the overhead ground wire.
As a preferred embodiment, the equivalent voltage source calculation module is specifically configured to:
according to the wire port x of the overhead ground wireAInduced voltage U ofindA(xAω), line drop and x from another wire portBReflected voltage U transmitted after time delay tauB(t- τ) calculating a voltage source for the wire port by the following calculation:
UrA(t)＝UindA(xA,t)+UB(t-τ)+Z'·iB(t-τ)；
wherein, UrA(t) is the conductor port x of the overhead earth wireAA voltage source of (a); u shapeindA(xAAnd t) is the wire port x of the overhead earth wireAThe expression mode of the induced voltage in time frequency; u shapeB(t- τ) is said another wire port xBReflected voltage transmitted after time delay tau; z'. iB(t- τ) is the line pressure drop; z' is the characteristic impedance of the overhead line, iB(t- τ) is the wire port xBThe line current of (1);
converting a voltage source of a wire port of the overhead ground wire into an equivalent voltage source of the wire port:
wherein j is the number of phases.
It should be noted that the computing apparatus for the lightning induced voltage according to the embodiment of the present invention is used for executing all the process steps of the computing method for the lightning induced voltage according to the embodiment, and the working principles and the beneficial effects of the two are in one-to-one correspondence, so that details are not repeated.
The second embodiment of the invention provides a device for calculating lightning induced voltage, which is used for calculating the induced voltage at a wire port of an overhead ground wire by establishing a lightning channel model on the overhead ground wire; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth; and calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port of the overhead ground wire, and further establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software so as to calculate the lightning induction voltage of the overhead ground wire. The Bergeron model in EMTP is used for modeling a three-phase overhead line and an overhead ground wire line system, and the induced voltage of a lead port of the overhead ground wire can be calculated more accurately by establishing a lightning channel model and processing the induction effect of the damaged ground. The method adopts EMTP modeling to perform modeling simulation on lightning induced overvoltage of the overhead line with the overhead ground wire, is used for analyzing lightning induced overcurrent of the overhead ground wire, can test the lightning resistance level of the overhead line, verifies the reduction effect of the distribution line overhead ground wire on the lightning induced voltage, realizes the calculation modeling of the induced voltage of a complex network, and provides the construction and operation reference of the distribution network.
Fig. 4 is a schematic structural diagram of another lightning induced voltage calculation apparatus according to a third embodiment of the present invention. The device 30 for calculating the lightning induced voltage provided by the embodiment of the invention comprises a processor 31, a memory 32 and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the method for calculating the lightning induced voltage according to the first embodiment when executing the computer program.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (10)
1. A method for calculating induced voltage of a lightning is suitable for a power distribution network system configured with an overhead ground wire, and is characterized by comprising the following steps of:
establishing a lightning channel model on the overhead ground wire;
calculating the induced voltage at the wire port of the overhead ground wire according to the lightning channel model; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth;
calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port;
and according to the equivalent voltage source of the wire port, establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software so as to calculate the lightning induction voltage of the overhead ground wire.
2. The method for calculating the lightning induced voltage according to claim 1, wherein the calculating the induced voltage at the conductor port of the overhead ground wire according to the lightning channel model specifically comprises:
analyzing the electric field distribution on the overhead ground wire according to the lightning channel model;
and calculating the line voltage drop on the overhead ground wire according to the electric field distribution on the overhead ground wire so as to calculate and obtain the induced voltage at the wire port of the overhead ground wire.
3. The method for calculating the lightning induced voltage according to claim 2, wherein the lightning path model on the overhead ground wire is represented by lightning current, specifically as follows:
I(z',t)＝u(t-z'/vf)p(z')I(0,t-z'/v)；
wherein I (z', t) is lightning current in the lightning channel model; u (t-z'/v)f) Is a step function, p (z') is the current attenuation coefficient as a function of height; i (0, t-z'/v) is the propagation magnitude of the lightning current; v. offIs the speed of the upstream front; v is the currentThe propagation velocity of the wave; z' is a height value.
4. The method of calculating lightning induced voltage according to claim 2, characterised in that the induced voltage at the conductor port of the overhead earth wire is specified in the frequency domain as:
UindA(xA,ω)＝U0(xA,ω)-g0(jω)·Ug(xA,ω)；
wherein, UindA(xAω) is the conductor port x of the overhead earth wireAInduced voltage of (U)0(xAω) is a lossless component,
Ug(xAand, ω) is a lossy component,
g0(j ω) is a green's function that accounts for earth effects; x is the number ofAAnd xBRespectively the coordinates of the two ends of the conductor of the overhead earth wire, Ex(xAY, h, ω) and Ez(xBY,0, ω) are the horizontal and vertical electric field components, By0For the horizontal magnetic field component, h is the height of the overhead ground wire.
5. The method for calculating the lightning induced voltage according to claim 4, wherein calculating the equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port specifically comprises:
according to the wire port x of the overhead ground wireAInduced voltage, line drop and from another wire port xBAnd calculating the voltage source of the wire port by the following calculation formula according to the reflected voltage transmitted after the time delay tau:
UrA(t)＝UindA(xA,t)+UB(t-τ)+Z'·iB(t-τ)；
wherein, UrA(t) isConductor port x of the overhead ground wireAA voltage source of (a); u shapeindA(xAAnd t) is the wire port x of the overhead earth wireAThe expression mode of the induced voltage in time frequency; u shapeB(t- τ) is said another wire port xBReflected voltage transmitted after time delay tau; z'. iB(t- τ) is the line pressure drop; z' is the characteristic impedance of the overhead line, iB(t- τ) is the wire port xBThe line current of (1);
converting a voltage source of a wire port of the overhead ground wire into an equivalent voltage source of the wire port:
wherein j is the number of phases.
6. A lightning induced voltage calculation device suitable for a power distribution network system configured with an overhead ground wire, comprising:
the lightning channel model establishing module is used for establishing a lightning channel model on the overhead ground wire;
the port induced voltage calculation module is used for calculating the induced voltage at the wire port of the overhead ground wire according to the lightning channel model; the induced voltage at the wire port comprises a lossy component influenced by a lossy earth;
the equivalent voltage source calculation module is used for calculating an equivalent voltage source of the wire port of the overhead ground wire according to the induced voltage of the wire port;
and the lightning induction voltage model establishing module is used for establishing a lightning induction voltage model of the overhead ground wire by adopting EMPT software according to the equivalent voltage source of the wire port so as to calculate the lightning induction voltage of the overhead ground wire.
7. The lightning induced voltage calculation apparatus of claim 6, wherein the port induced voltage calculation module specifically comprises:
the electric field distribution analysis unit is used for analyzing the electric field distribution on the overhead ground wire according to the lightning channel model;
and the port induced voltage calculation unit is used for calculating the line voltage drop on the overhead ground wire according to the electric field distribution on the overhead ground wire so as to calculate and obtain the induced voltage at the wire port of the overhead ground wire.
8. The apparatus for calculating the lightning induction voltage according to claim 7, wherein the lightning channel model on the overhead ground wire is represented by lightning current, specifically:
I(z',t)＝u(t-z'/vf)p(z')I(0,t-z'/v)；
wherein I (z', t) is lightning current in the lightning channel model; u (t-z'/v)f) Is a step function, p (z') is the current attenuation coefficient as a function of height; i (0, t-z'/v) is the propagation magnitude of the lightning current; v. offIs the speed of the upstream front; v is the propagation velocity of the current wave; z' is a height value.
9. The apparatus for calculating a lightning induced voltage according to claim 7, wherein the induced voltage at the wire port of the overhead ground wire is specified in the frequency domain as:
UindA(xA,ω)＝U0(xA,ω)-g0(jω)·Ug(xA,ω)；
wherein, UindA(xA,Omega) is the wire port x of the overhead ground wireAInduced voltage of (U)0(xAω) is a lossless component,
Ug(xAand, ω) is a lossy component,
g0(j ω) is a green's function that accounts for earth effects; x is the number ofAAnd xBAre respectively provided withIs the coordinate of the two ends of the conductor of the overhead earth wire, Ex(xAY, h, ω) and Ez(xBY,0, ω) are the horizontal and vertical electric field components, By0For the horizontal magnetic field component, h is the height of the overhead ground wire.
10. The lightning induced voltage calculation apparatus of claim 9, wherein the equivalent voltage source calculation module is specifically configured to:
according to the wire port x of the overhead ground wireAInduced voltage, line drop and from another wire port xBAnd calculating the voltage source of the wire port by the following calculation formula according to the reflected voltage transmitted after the time delay tau:
UrA(t)＝UindA(xA,t)+UB(t-τ)+Z'·iB(t-τ)；
wherein, UrA(t) is the conductor port x of the overhead earth wireAA voltage source of (a); u shapeindA(xAAnd t) is the wire port x of the overhead earth wireAThe expression mode of the induced voltage in time frequency; u shapeB(t- τ) is said another wire port xBReflected voltage transmitted after time delay tau; z'. iB(t- τ) is the line pressure drop; z' is the characteristic impedance of the overhead line, iB(t- τ) is the wire port xBThe line current of (1);
converting a voltage source of a wire port of the overhead ground wire into an equivalent voltage source of the wire port:
wherein j is the number of phases.
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