CN115688661B - Modeling method for full circuit parameters of spiral tube type damping bus for VFTO (very fast transient overvoltage) suppression - Google Patents
Modeling method for full circuit parameters of spiral tube type damping bus for VFTO (very fast transient overvoltage) suppression Download PDFInfo
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Abstract
The invention provides a modeling method of a spiral tubular damping bus full circuit parameter for VFTO suppression, which comprises the following steps: establishing a damping bus full-circuit parameter equivalent circuit with each coil including stray parameters and gap breakdown impedance based on an inductance and resistance equivalent circuit of the spiral tube type damping bus; and calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit. On the basis of the existing inductance and resistance equivalent model, the influence of stray parameters is considered, the real situation of the damping bus can be well equivalent, and further theoretical basis is provided for well restraining VFTO and optimizing the design of the spiral tubular damping bus.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a modeling method of full circuit parameters of a spiral tubular damping bus for VFTO suppression.
Background
With the improvement of the voltage level of a power supply and distribution system and the increase of the capacity of a Gas Insulated Substation (GIS) in China, the insulation problem of the transformer substation is more prominent due to Very Fast Transient Overvoltage (VFTO) generated by switching operation, the damage caused by the very fast transient overvoltage is more serious, and the effective inhibition of the VFTO is the first problem to be solved for ensuring the safe and stable operation of the GIS.
The method for suppressing the VFTO of the GIS has the advantages that the effect of suppressing the VFTO of the installed spiral tube type damping bus is good, engineering application conditions are easy to meet, the influence on the normal work of the GIS cannot be generated, and the method is the VFTO suppressing method with an engineering application prospect. The spiral tube type damping bus equivalent circuit can be utilized to carry out analysis and research on the suppression effect, but the existing damping bus is only roughly equivalent to an inductance-resistance equivalent circuit, the VFTO propagates and contains a part of power frequency components and abundant non-power frequency components, when the VFTO is conducted and coupled to the damping bus, the damping bus can generate a series of stray capacitance, stray inductance and gap breakdown impedance (called as the stray parameter of the damping bus in a closed mode), and the stray parameter has certain high-frequency response and can have certain influence on the suppression effect. How to seek a better equivalent model of the spiral tube type damping bus is a topic worthy of research.
Disclosure of Invention
The invention provides a modeling method of full circuit parameters of a spiral tubular damping bus for VFTO suppression, aiming at the technical problems in the prior art, and the modeling method considers the influence of stray parameters on the basis of the existing inductance and resistance equivalent model, can well equivalent the real situation of the damping bus, and further provides a theoretical basis for better suppressing VFTO and optimizing the design of the spiral tubular damping bus.
According to a first aspect of the invention, a modeling method for full circuit parameters of a spiral tubular damping bus for VFTO suppression is provided, and the modeling method comprises the following steps:
s1, establishing a damping bus full-circuit parameter equivalent circuit containing stray parameters and gap breakdown impedance for each turn of coil based on an inductance-parallel resistance equivalent circuit of a spiral tubular damping bus;
and S2, calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit.
On the basis of the technical scheme, the invention can be improved as follows.
Optionally, in step S1, the constructed damping bus full circuit parameter equivalent circuit includes:
multiple single-turn coil equivalent circuit modules connected in series, stray capacitance between damping bus and conventional bus
And stray inductance between the damping bus and the conventional bus
Each single-turn coil equivalent circuit module is connected in series with a stray capacitance between the damping bus and the shell
The back is grounded;
each single-turn coil equivalent circuit module comprises a first branch circuit, a second branch circuit and a third branch circuit which are connected in parallel; the first branch circuit comprises a single-turn coil parallel resistor R e The second branch circuit comprises a single-turn coil equivalent inductance L e ；
In the first/last coil equivalent circuit module, the third branch comprises a first branch and a second branch connected in seriesGap breakdown resistance R v Stray capacitance between connector and first/last turn coil
And stray inductance between the connector and the first/last turns
；
In the equivalent circuit module of the other turns, the third branch comprises a gap breakdown resistance R connected in series v Stray capacitance between adjacent turns of coil
And stray inductance between adjacent turns
。
Optionally, in step S2, the process of calculating the equivalent inductance and the stray inductance of the damping bus includes:
judging whether the current passing through the spiral tube type damping bus is high-frequency current: if the current is not high-frequency current, inductance calculation under power frequency is carried out; if the current is high-frequency current, calculating the equivalent inductance of the damping bus by using a field calculation method and combining a skin effect; and (4) calculating the external magnetic flux of the damping bus by using a field calculation method to obtain the stray inductance.
Optionally, the process of calculating the equivalent inductance and the stray inductance of the damping bus includes:
assuming that the relation between the current i and the magnetic flux B in the damping bus and the inductance L is as follows (1):
when the current i flowing through the spiral tube type damping bus is judged to be low-frequency current, the current i is
Will be
Substituting equation (1), the obtained equation (2) is used for calculating the equivalent inductance L of the damping bus:
when the current i flowing through the spiral tube type damping bus is judged to be high-frequency current, the skin depth of the current in the damping bus is assumed to be shown in an equation (3):
in the formula (3), δ sd Skin depth in m; f is the excitation frequency in Hz; mu is magnetic conductivity, and the unit is H/m; sigma is the conductivity, and the unit is S/m;
an effective sectional area s through which the current i flows, that is, a sectional area within a skin depth, is represented by formula (4):
in the formula (4), r is the outer diameter of the section of the damping bus, and a is the ratio of the inner diameter to the outer diameter of the section of the damping bus;
substituting equation (4) into inductance calculation equation (1) to obtain equation (5), and calculating damping bus inductance L using equation (5):
optionally, in step S2, a maxwell capacitance matrix is used, and the stray capacitance of the damping bus is calculated according to a relationship between turn-to-turn charges and potentials.
Optionally, the process of calculating the stray capacitance of the damping bus specifically includes:
suppose n conductors each have a charge of Q 1 、Q 2 、…Q n Formula (6) can be obtained by the potential superposition theorem:
wherein, V 1 、V 2 、…V n The potentials corresponding to the n conductors are obtained, and C is a Maxwell capacitance matrix;
the total charge of one of the conductors is given by equation (6):
then for a system with n conductors, the maxwell capacitance matrix C can be expressed as:
in the formula (8), i is one of n conductors, C mni The capacitance is mutual capacitance, namely stray capacitance generated after charges of an n conductor and an i conductor are accumulated;
the stray capacitance between the damping bus and the shell can be obtained by solving the electric charge quantity Q and the electric potential V corresponding to the damping bus, each turn of coil, the conventional bus and the connector through field calculation and solving the Maxwell capacitance matrix C
Stray capacitance between adjacent turns of coil
Stray capacitance between connector and first/last turn coil
Stray capacitance between damping bus and conventional bus
。
Optionally, in step S2, the damping bus gap breakdown condition is obtained by using damping bus coupling calculation and a gap breakdown criterion.
Optionally, the process of calculating the gap breakdown impedance of the damping bus specifically includes:
judging whether the turn-to-turn gap is completely broken down according to the formula (9):
wherein, the first and the second end of the pipe are connected with each other,
is the density of the gas in the inter-turn gap,Eis the distribution of the turn-to-turn gap electric field;
when E is d >When 0, judging that the turn-to-turn gap is completely broken down, and then calculating according to the formula (10) to obtain breakdown impedance R of the turn-to-turn gap of the damping bus v ：
Wherein R is a Is a static arcing resistor; r 0 The high-resistance state is the high-resistance state when the gap of the isolating switch is insulated;
is a time constant; t is t 0 Turn-to-turn gas breakdown and stable combustion phase time.
According to a second aspect of the present invention, there is provided a modeling system for full circuit parameters of a spiral-tube type damping bus for VFTO suppression, comprising:
the model building module is used for building a damping bus full circuit parameter equivalent circuit with each turn of coil containing stray parameters and gap breakdown impedance based on an inductance parallel resistance equivalent circuit of the spiral tube type damping bus;
and the parameter calculation module is used for calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit.
The invention provides a modeling method of full circuit parameters of a spiral tubular damping bus for VFTO suppression, which is characterized in that on the basis of establishment of a damping bus equivalent circuit, the damping bus equivalent circuit containing stray parameters is established according to the structural characteristics and the action mechanism of the spiral tubular damping bus; on the basis of an equivalent circuit containing stray parameters, spiral tube type damping bus inductance, stray capacitance, stray inductance and damping bus turn-to-turn gap impedance parameters are calculated to obtain spiral tube type damping bus full circuit parameters. The full circuit parameters of the spiral tubular damping bus for VFTO suppression can be equivalent to the spiral tubular damping bus under the basis of more completely mastering a damping bus suppression mechanism, the suppression effect of the damping bus on VFTO can be effectively analyzed, and a certain theoretical basis is further provided for better designing a damping bus structure.
Drawings
FIG. 1 is a schematic structural diagram of a spiral tube type damping bus;
FIG. 2 is a flow chart of a modeling method of full circuit parameters of a spiral tube type damping bus for VFTO suppression provided by the invention;
FIG. 3 is an equivalent circuit diagram of the full circuit parameters of the spiral tubular damping bus for VFTO suppression provided by the invention;
FIG. 4 is a flow chart of an inductance calculation for a damping bus in one embodiment;
FIG. 5 is a schematic diagram of a modeling system composition structure of full circuit parameters of a spiral tube type damping bus for VFTO suppression provided by the invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
Fig. 1 is a schematic diagram of a hardware structure of a spiral tube type damping bus bar. As shown in fig. 1, the spiral tube type damping bus is formed by spirally digging hollow grooves in a bus tube, so that the obtained spiral coil forms a spiral tube, and the hollowed grooves play a role in inter-turn discharge gaps of the coil. The turn-to-turn damping resistors of the spiral tube are connected in parallel, and the epoxy support piece arranged in the spiral tube provides structural support for the turn-to-turn damping resistors. The spiral pipe type damping bus is integrally arranged in SF6 gas and is of a distributed structure. SF6 gas is used as an insulating medium between the damping bus and the shell, and the shell is grounded.
Based on the spiral tube type damping bus structure shown in fig. 1, as shown in fig. 2, the invention provides a flow chart of a modeling method of full circuit parameters of a spiral tube type damping bus for VFTO suppression. As shown in fig. 2, the method includes:
s1, establishing a damping bus full-circuit parameter equivalent circuit containing stray parameters and gap breakdown impedance for each turn of coil based on an inductance-parallel resistance equivalent circuit of a spiral tubular damping bus;
and S2, calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit.
It can be understood that the damping bus structure is a multi-turn spiral coil and a multi-stage parallel resistor, each part of the damping bus generates stray parameters due to electrostatic induction and electromagnetic induction, and inter-turn gap breakdown generates impedance. Based on the defects in the background art, in order to more completely and effectively analyze the suppression effect of the damping bus on the VFTO, further to better master the suppression mechanism of the damping bus, obtain the optimal suppression effect and reduce the design cost, the embodiment of the invention provides a spiral tube type damping bus broadband transient model modeling method for VFTO suppression.
In a possible embodiment mode, as shown in fig. 3, in step S1, the constructed damping bus full-circuit parameter equivalent circuit includes:
multiple single-turn coil equivalent circuit modules connected in series, stray capacitance between damping bus and conventional bus
And stray inductance between damping bus and conventional bus
Each single-turn coil equivalent circuit module is connected in series with the stray capacitance between the damping bus and the shell
The back is grounded;
each single-turn coil equivalent circuit module comprises a first branch circuit, a second branch circuit and a third branch circuit which are connected in parallel; the first branch circuit comprises a single-turn coil parallel resistor R e The second branch circuit comprises a single-turn coil equivalent inductance L e ；
In the first/last coil equivalent circuit module, the third branch comprises a gap breakdown resistance R connected in series v Stray capacitance between connector and first/last coil
And stray inductance between the connector and the first/last turn coil
；
In the equivalent circuit module of the other coils, the third branch comprises a gap breakdown resistance R connected in series v Stray capacitance between adjacent turns of coil
And stray inductance between adjacent turns
。
It will be appreciated that at high frequencies, the helical tubular damping bus bar is unique in its structureThe structure can generate strong high-frequency response, SF6 gas in turn-to-turn gaps can be broken down, and various stray parameters and breakdown impedance are generated, so that on the basis of the existing centralized parameter equivalent circuit of inductance and resistance, a damping bus circuit is expanded into a full circuit parameter equivalent circuit which considers the stray parameters and the gap breakdown impedance parameters among the turns, among all the turns, between a connector part and a first and a last turn, and between a conventional bus and a damping bus and a shell, and can be equivalent to a spiral tubular damping bus more truly and completely. Note that the gap breakdown resistance R shown in FIG. 3 v The value is determined by the gap breakdown of the damping bus bar under VFTO conditions and is therefore represented temporarily by the dashed line.
In a possible embodiment, in step S2, as shown in the flowchart of fig. 4, the process of calculating the equivalent inductance and the stray inductance of the damping bus includes:
judging whether the current passing through the spiral tube type damping bus is a high-frequency current: if the current is not high-frequency current, inductance calculation under power frequency is carried out; if the current is high-frequency current, calculating the equivalent inductance of the damping bus by combining a field calculation method and a skin effect; and (4) calculating the external magnetic flux of the damping bus by using a field calculation method to obtain the stray inductance.
It can be understood that, considering the current skin effect, the current under different frequency conditions is distributed differently on the spiral tube type damping bus, the effective cross section of the damping bus passing the current is correspondingly different, and the coupling condition of the flux linkage when the damping bus passes the current is the key of the inductance calculation of the damping bus. Therefore, the damping bus inductance calculation flow shown in fig. 4 mainly focuses on the flux linkage coupling condition of the damping bus when the frequency and the current flow through the damping bus, wherein the flux linkage coupling condition is reflected by the damping bus flux density obtained by field calculation under different frequencies.
More specifically, in one possible embodiment, the process of calculating the equivalent inductance of the damping bus and the stray inductance is as follows:
the essence of the inductance calculation is the magnetic flux calculation, so the relation between the current i and the magnetic flux B in the damping bus and the inductance L is assumed as formula (1):
under the condition of low frequency, the distribution nonuniformity of the current on the cross section of the conductor is generally ignored, and when the current i flowing through the spiral tube type damping bus is judged to be the low-frequency current, the current i has the characteristics of
Will be
Substituting equation (1), the obtained equation (2) is used for calculating the equivalent inductance L of the damping bus:
under high frequency, the current is completely concentrated in the extremely thin surface layer of the conductor, and the concentrated thickness is the skin depth. When the current i flowing through the spiral tube type damping bus is judged to be high-frequency current, the skin depth of the current in the damping bus is assumed to be shown in an equation (3):
in the formula (3), δ sd Skin depth in m; f is the excitation frequency in Hz; mu is magnetic conductivity, and the unit is H/m; sigma is the conductivity, and the unit is S/m;
due to the skin effect, the inductance calculation formula cannot be directly calculated, and can be approximately calculated from the skin depth, and at this time, the effective sectional area s through which the current i flows, that is, the sectional area in the skin depth, is as shown in formula (4):
in the formula (4), r is the outer diameter of the section of the damping bus, and a is the ratio of the inner diameter to the outer diameter of the section of the damping bus.
Substituting the formula (4) into the inductance calculation formula (1) to obtain a formula (5), and calculating the damping bus equivalent inductance value L by adopting the formula (5):
calculating equivalent inductance L of each turn of coil of damping bus e And meanwhile, the internal magnetic flux of the coil of the current turn is substituted into the equation for calculation. It will be appreciated that stray inductance between the connectors and the first/last turn coils
Stray inductance between adjacent turns of coil
And stray inductance between damping bus and conventional bus
The calculation method is basically the same as the calculation method of the equivalent inductance Le of the spiral tube type damping bus body by the reflection of an external magnetic chain generated when current flows through the damping bus. The difference is mainly the difference in the magnetic flux B substituted into the above equations (2) and (5). For example, calculating stray inductance between connectors and first/last turn coils
In the process, external magnetic flux between the connector and the first/last coil is required to be substituted into an equation for calculation; calculating stray inductance between adjacent turns
In the process, external magnetic flux between adjacent turns of coils is required to be substituted into an equation for calculation; calculating stray inductance between damping bus and conventional bus
In the process, external magnetic communication between the damping bus and the conventional bus is requiredAnd substituting into an equation for calculation.
In a possible embodiment mode, in step S2, the stray capacitance of the damping bus is calculated by using a maxwell capacitance matrix and through a relationship between turn-to-turn charges and potentials.
It can be understood that the spiral tube type damping bus, the conventional bus, the connector portion, and each turn of coil will generate stray capacitance after charge accumulation, and the distribution of the stray capacitances can refer to the equivalent circuit diagram shown in fig. 3. Starting from a stray capacitance generation mechanism, calculation of stray capacitance can be converted into calculation of conductor charge accumulation, a Maxwell capacitance matrix represents the relation between the charge of a certain conductor and the voltage of all conductors, and the stray capacitance generated after charge accumulation can be obtained by converting the Maxwell capacitance matrix into a mutual capacitance matrix.
In a possible embodiment, the process of calculating the stray capacitance of the damping bus specifically includes:
respectively considering the spiral tube type damping bus, the conventional bus, the connector part and each turn of coil as independent conductors, wherein the total number of the conductors is n;
suppose n conductors each have a charge of Q 1 、Q 2 、…Q n Formula (6) can be obtained by the potential superposition theorem:
wherein, V 1 、V 2 、…V n The corresponding electric potential of the n conductors, C is a Maxwell capacitance matrix, and the Maxwell capacitance matrix C describes the relation between the electric charge of the ith conductor in the n conductors and the voltage of all conductors in the system;
the total charge of one of the conductors (e.g., the first conductor) is derived from equation (6):
then for a spiral tube type damping bus bar system with n conductors, the maxwell capacitance matrix C can be expressed as:
in the formula (8), i is one of n conductors, C mni The capacitance is mutual capacitance, namely stray capacitance generated after charges of an n conductor and an i conductor are accumulated.
When the stray capacitance of the damping bus is solved, the relation between the Maxwell capacitance matrix and the mutual capacitance matrix is used for solving, the electric charge quantity Q and the electric potential V corresponding to the damping bus, each turn of coil, the connector and the conventional bus are solved through field calculation, and the stray capacitance between the damping bus and the shell can be obtained through calculation by solving the Maxwell capacitance matrix C
Stray capacitance between adjacent turns of coil
Stray capacitance between connector and first/last turn coil
Stray capacitance between damping bus and conventional bus
。
In a possible embodiment, in step S2, the damping bus gap breakdown condition is obtained by using the damping bus coupling calculation and the gap breakdown criterion.
It can be understood that when a high-frequency and high-amplitude value VFTO is transmitted on the damping bus, the temperature of the damping bus rises, a coil turn-to-turn gap SF6 gas medium breaks down, and the generated turn-to-turn breakdown impedance affects the impedance characteristic of the damping bus. The invention obtains the gas between each coil gap of the damping bus under the condition of considering temperature rise and gas medium flowBulk density
And E, obtaining the breakdown condition of the damping bus clearance by combining the electric field distribution E with an insulation breakdown criterion. Namely, the breakdown condition of the coil gap of each turn of the spiral tube type damping bus can be obtained by analyzing the section distribution condition of the critical breakdown field intensity criterion of the damping bus gap.
In a possible embodiment, the process of calculating the gap breakdown impedance of the damping bus specifically includes:
firstly, the breakdown condition of the gap of the damping bus needs to be judged. And (3) taking the formula (9) as a gap breakdown criterion, and judging whether the turn-to-turn gap is completely broken down or not according to the formula (9):
wherein the content of the first and second substances,
is the density of the gas in the inter-turn gap,Eis the inter-turn gap electric field distribution.
To define the breakdown condition, this patent considers damping E in the bus bar gap d >The region of 0 exceeds half the gap, i.e. the entire gap is considered to be completely broken down. And then, calculating the spark gap resistance shown in the following formula (10) by utilizing a spark gap breakdown theory to obtain the breakdown impedance parameter of the turn-to-turn gap of the damping bus.
Specifically, when E d >When 0, judging that the turn-to-turn gap is completely broken down, and then calculating according to the formula (10) to obtain breakdown impedance R of the turn-to-turn gap of the damping bus v ：
Wherein R is a Is a static arcing resistor; r is 0 The state is a high-resistance state when the gap of the isolating switch is insulated; τ is a time constant; t is t 0 Is gas impact between turnsWear and stable combustion phase time.
The modeling method of the full circuit parameters of the spiral tubular damping bus for VFTO suppression, which is established by the invention, can well equate the real situation of the spiral tubular damping bus, thereby providing a certain theoretical basis for better suppressing VFTO.
Fig. 5 is a structural diagram of a modeling system for full circuit parameters of a spiral tube type damping bus for VFTO suppression according to an embodiment of the present invention, and as shown in fig. 5, the modeling system for full circuit parameters of the spiral tube type damping bus for VFTO suppression includes a model building module and a parameter calculating module, where:
the model building module is used for building a damping bus full-circuit parameter equivalent circuit containing stray parameters and gap breakdown impedance of each turn of coil based on an inductance parallel resistance equivalent circuit of the spiral tube type damping bus;
and the parameter calculation module is used for calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit.
It can be understood that the modeling system of the full circuit parameters of the spiral tube type damping bus for VFTO suppression provided by the present invention corresponds to the modeling method of the full circuit parameters of the spiral tube type damping bus for VFTO suppression provided by the foregoing embodiments, and the relevant technical features of the modeling system of the full circuit parameters of the spiral tube type damping bus for VFTO suppression may refer to the relevant technical features of the modeling method of the full circuit parameters of the spiral tube type damping bus for VFTO suppression, and are not described herein again.
According to the modeling method and system for the full circuit parameters of the spiral tubular damping bus for VFTO suppression, provided by the embodiment of the invention, on the basis of the establishment of the damping bus equivalent circuit, the damping bus equivalent circuit containing stray parameters is established according to the structural characteristics and the action mechanism of the spiral tubular damping bus; on the basis of an equivalent circuit containing stray parameters, spiral tube type damping bus inductance, stray capacitance, stray inductance and damping bus turn-to-turn gap impedance parameters are calculated to obtain spiral tube type damping bus full circuit parameters. Full circuit parameters of the spiral tubular damping bus for VFTO suppression can be equivalent to the spiral tubular damping bus under the basis of more completely mastering a damping bus suppression mechanism, so that the suppression effect of the damping bus on VFTO can be effectively analyzed, and a certain theoretical basis is provided for better designing a damping bus structure.
It should be noted that, in the foregoing embodiments, the description of each embodiment has an emphasis, and reference may be made to the related description of other embodiments for a part that is not described in detail in a certain embodiment.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (5)
1. A modeling method for full circuit parameters of a spiral tube type damping bus for VFTO suppression is characterized by comprising the following steps:
s1, establishing a damping bus full-circuit parameter equivalent circuit containing stray parameters and gap breakdown impedance for each turn of coil based on an inductance-parallel resistance equivalent circuit of a spiral tubular damping bus; the constructed damping bus full circuit parameter equivalent circuit comprises:
stray capacitance C between multiple single-turn coil equivalent circuit modules, damping bus and conventional bus connected in series σ2 And stray inductance L between the damping bus and the conventional bus σ2 Each single-turn coil equivalent circuit module is connected in series with a stray capacitor C between the damping bus and the shell σe0 Then grounding;
each single-turn coil equivalent circuit module comprises a first branch circuit, a second branch circuit and a third branch circuit which are connected in parallel; the first branch comprises a sheetTurn coil parallel resistance R e The second branch circuit comprises a single-turn coil equivalent inductance L e ；
In the first/last coil equivalent circuit module, the third branch comprises a gap breakdown resistance R connected in series v Stray capacitance C between connector and first/last coil σ12 And stray inductance L between the connector and the first/last turn coil σ12 ；
In the equivalent circuit module of the other turns, the third branch comprises a gap breakdown resistance R connected in series v And stray capacitance C between adjacent coils σ11 And stray inductance L between adjacent turns σ11 ；
S2, calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit;
specifically, the process of calculating the equivalent inductance and the stray inductance of the damping bus includes:
judging whether the current passing through the spiral tube type damping bus is a high-frequency current: if the current is not high-frequency current, inductance calculation under power frequency is carried out; if the current is high-frequency current, calculating the equivalent inductance of the damping bus by combining a field calculation method and a skin effect; the external magnetic flux of the damping bus is calculated by using a field calculation method to obtain stray inductance;
calculating to obtain the stray capacitance of the damping bus by using a Maxwell capacitance matrix and the relation between turn-to-turn charge and potential;
and obtaining the gap breakdown condition of the damping bus by using the coupling calculation of the damping bus and a gap breakdown criterion.
2. The modeling method of full circuit parameters of the spiral tube type damping bus for VFTO suppression according to claim 1, wherein the process of calculating the equivalent inductance and the stray inductance of the damping bus comprises the following steps:
assuming that the relation between the current i, the magnetic flux B and the inductance L in the damping bus is as follows (1):
when the current i flowing through the spiral tube type damping bus is judged to be low-frequency current, the current i is
Will>
Substituting equation (1), the obtained equation (2) is used for calculating the equivalent inductance L of the damping bus:
when the current i flowing through the spiral tube type damping bus is judged to be high-frequency current, the skin depth of the current in the damping bus is assumed to be shown in an equation (3):
in the formula (3), δ sd Skin depth in m; f is the excitation frequency in Hz; mu is magnetic conductivity, and the unit is H/m; σ is the conductivity, with the unit of S/m;
an effective sectional area s through which the current i flows, that is, a sectional area within a skin depth, is represented by formula (4):
in the formula (4), r is the outer diameter of the section of the damping bus, and a is the ratio of the inner diameter to the outer diameter of the section of the damping bus;
substituting equation (4) into inductance calculation equation (1) to obtain equation (5), and calculating the damping bus inductance L by using equation (5):
3. the method for modeling the full circuit parameters of the spiral tube type damping bus for VFTO suppression as claimed in claim 1, wherein the process of calculating the stray capacitance of the damping bus specifically comprises:
suppose that n conductors each have a charge of Q 1 、Q 2 、…Q n Formula (6) can be obtained by the potential superposition theorem:
wherein, V 1 、V 2 、…V n The potentials corresponding to the n conductors are obtained, and C is a Maxwell capacitance matrix;
the total charge of one of the conductors is obtained from equation (6):
then for a system with n conductors, its maxwell capacitance matrix C can be expressed as:
in the formula (8), i is one of n conductors, C mni The capacitance is mutual capacitance, namely stray capacitance generated after charges of an n conductor and an i conductor are accumulated;
the electric charge quantity Q and the electric potential V corresponding to the damping bus, each turn of coil, the conventional bus and the connector are solved through field calculation, and the Maxwell capacitance matrix C is solved to calculate the stray capacitance C between the damping bus and the shell σe0 And stray capacitance C between adjacent coils σ11 Stray capacitance C between connector and first/last coil σ12 Stray capacitance C between damping bus and conventional bus σ2 。
4. The method for modeling the full circuit parameters of the spiral tube type damping bus for VFTO suppression as claimed in claim 1, wherein the process of calculating the gap breakdown impedance of the damping bus specifically comprises:
judging whether the turn-to-turn gap is completely broken down according to the formula (9):
wherein the content of the first and second substances,ρis the density of the gas in the inter-turn gap,Ethe distribution of the inter-turn gap electric field is adopted;
when E is d >When 0, judging that the turn-to-turn gap is completely broken down, and then calculating according to the formula (10) to obtain breakdown impedance R of the turn-to-turn gap of the damping bus v ：
Wherein R is a Is a static arcing resistor; r 0 The state is a high-resistance state when the gap of the isolating switch is insulated; τ is a time constant; t is t 0 Turn-to-turn gas breakdown and stable combustion phase time.
5. A modeling system for full circuit parameters of a spiral tube type damping bus for VFTO suppression is characterized by comprising the following components:
the model building module is used for building a damping bus full circuit parameter equivalent circuit with each turn of coil containing stray parameters and gap breakdown impedance based on an inductance parallel resistance equivalent circuit of the spiral tube type damping bus; the constructed damping bus full circuit parameter equivalent circuit comprises:
stray capacitance C between multiple single-turn coil equivalent circuit modules, damping bus and conventional bus connected in series σ2 And stray inductance L between the damping bus and the conventional bus σ2 Each single-turn coil equivalent circuit module is connected in series with a stray capacitor C between the damping bus and the shell σe0 Then grounding;
each single-turn coil equivalent circuit module comprises a first branch circuit, a second branch circuit and a third branch circuit which are connected in parallel; the first branch comprisesSingle-turn coil parallel resistor R e The second branch circuit comprises a single-turn coil equivalent inductance L e ；
In the first/last coil equivalent circuit module, the third branch comprises a gap breakdown resistance R connected in series v Stray capacitance C between connector and first/last turn coil σ12 And stray inductance L between the connector and the first/last turn coil σ12 ；
In the equivalent circuit module of the other turns, the third branch comprises a gap breakdown resistance R connected in series v Stray capacitance C between adjacent turns σ11 And stray inductance L between adjacent turns σ11 ；
The parameter calculation module is used for calculating the equivalent inductance, the stray capacitance, the stray inductance and the gap breakdown impedance of the damping bus based on the full circuit parameter equivalent circuit;
specifically, the process of calculating the equivalent inductance and the stray inductance of the damping bus includes:
judging whether the current passing through the spiral tube type damping bus is a high-frequency current: if the current is not high-frequency current, inductance calculation under power frequency is carried out; if the current is high-frequency current, calculating the equivalent inductance of the damping bus by using a field calculation method and combining a skin effect; calculating the external magnetic flux of the damping bus by using a field calculation method to obtain stray inductance;
calculating to obtain the stray capacitance of the damping bus by using a Maxwell capacitance matrix and the relation between turn-to-turn charge and potential;
and obtaining the gap breakdown condition of the damping bus by using the coupling calculation of the damping bus and a gap breakdown criterion.
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