CN107846013A - GIS shells circulation and transient state ground potential rise modeling and analysis method based on PEEC methods - Google Patents

Abstract

The invention discloses a method for modeling and analyzing GIS shell circulation and transient ground potential rise based on the PEEC method. Based on the mechanism of the circulation and transient ground potential rise in the GIS system, the PEEC method is used to establish the GIS The model of the busbar and the shell, and then construct the equivalent model, and carry out the simulation to obtain the relationship curve between the amplitude of the GIS interphase circulation and the ground network circulation and the grounding point, and determine the influencing factors of the shell circulation and TGPR according to the relationship curve. The invention is beneficial to power grid protection and control regulation.

Description

Modeling and Analysis of GIS Shell Circulation and Transient Earth Potential Rise Based on PEEC Method method

technical field

The invention relates to a method for modeling and analyzing GIS shell circulation and transient ground potential rise based on the PEEC method.

Background technique

In recent years, Gas Insulated Switchgear (GIS) has become an indispensable part of the power system due to its remarkable advantages such as compact structure, small size, small footprint, reliable operation, light maintenance tasks and less environmental pollution. . However, the distance between the components of the GIS system is relatively close, and the electromagnetic coupling between the components is strong. When the disconnector, circuit breaker, etc. are opened and closed, there will be a fast transient process in the GIS. The transient wave generated in GIS has the characteristics of short delay and high frequency. The rise time of these transient waves is nanoseconds, and the frequency can reach hundreds of megahertz. Through electromagnetic induction, it appears as a bus sleeve The overvoltage with extremely high amplitude and frequency on the tube produces a steep transient circulating current on the metal casing of the GIS, and contains extremely high frequency harmonic components.

In addition, because the transient circulating current generated in GIS has high-frequency and ultra-high-frequency components, and the layout of GIS cannot be consistent with the distance from the ground current injection point, it will cause the TGPR (Transient Grounding Potential Rise) effect of GIS, which may Electromagnetic interference will be generated to the monitoring and measuring equipment on the secondary side, causing system malfunction and becoming a huge hidden danger to the normal and stable operation of the power system.

Contents of the invention

In order to solve the above-mentioned problems, the present invention proposes a method for modeling and analyzing GIS shell circulation and transient ground potential rise based on the PEEC method. The present invention adopts the PEEC method to establish the model of the GIS busbar and shell, and analyzes according to the constructed model, which can Effective suppression of shell circulation and effective suppression of TGPR.

In order to achieve the above object, the present invention adopts the following technical solutions:

A modeling and analysis method for GIS shell circulation and transient ground potential rise based on PEEC method. Based on the mechanism of circulation and transient ground potential rise in the GIS system, the PEEC method is used to establish the GIS busbar and shell Model, and then build the equivalent model, conduct simulation, get the relationship curve between the amplitude of the GIS interphase circulation and ground network circulation and the grounding point, and determine the influencing factors of the shell circulation and TGPR according to the relationship curve.

Furthermore, the waveform of the fast transient overvoltage in the GIS system is determined by the formation time of the arc, that is, the time required for the contact gap to completely breakdown and conduct from the beginning of charge dissociation. The smaller the time value, the faster the transient overvoltage The waveform of the overvoltage is steeper.

Further, the main causes of TGPR in the GIS system include: First, the SF ₆ medium in the GIS has a high electric strength compared to air, but once it is broken down, its electric strength will drop instantly and the voltage will rise sharply , it is very easy to cause high-frequency oscillation in the entire system, causing a rise in transient ground potential; second, the voltage on the bus is relatively high, and the ground clearance is short, resulting in the breakdown of the air gap, thereby causing the potential to rise; It is when the circuit breaker or isolating switch is operated, the gas between the two contacts is broken down due to arc reignition; the fourth is the transient ground potential rise caused by the discharge of the external concentrated capacitor used for reactive power compensation or voltage adjustment; finally One is that the high-frequency current wave generates multiple reflections at the fracture of the shell, thereby causing a very high voltage.

Furthermore, when using the PEEC method to establish the model of the GIS busbar and shell, the research object is divided into small enough micro-elements, the self-mutual inductance and self-mutual capacitance of each micro-element are calculated, and a specific structure is constructed according to the actual structure of the object. The circuit model is used to calculate the equivalent circuit using the circuit analysis method, so as to realize the analysis of the electromagnetic coupling relationship of the research object.

Further, the PEEC model will be regarded as a multi-port circuit model and connected with the traditional circuit model, so as to achieve the goal of extending the scope of application of the PEEC model from microcircuits to multi-conductor large-scale electromagnetic systems.

Further, when constructing the PEEC model of the GIS busbar, when the busbar passes through the AC signal, there will be a skin effect in the busbar, and the charge will be concentrated on the outer surface of the busbar. The hollow conductive rod is used instead of the solid wire to calculate the skin depth , when carrying out the PEEC method equivalent to the busbar, select the rectangular cell whose height is smaller than the skin depth as the unit cell. In these cells, the charge density is considered to be uniform, and the self-inductance value of the unit cell is calculated. In the cell division of the busbar, the spatial positions of different cells are spatially parallel to calculate the mutual inductance value, and the inductance value of the GIS busbar is obtained by adding the self-inductance value and the mutual inductance value.

Further, when constructing the PEEC model of the GIS shell, the shell is divided into cuboid cells, and the self-inductance values of the cuboid cells are calculated sequentially, and the spatial positions of different cells are regarded as spatially parallel to calculate the mutual inductance value, and the self-inductance value Add the mutual inductance value to get the inductance value of the GIS shell.

Further, the grounding body model is constructed. According to the grounding network, multiple grounding bodies are connected into a network, and the coupling between the grounding bodies is ignored to form a Π-type equivalent circuit of the grounding body.

Further, multiple grounding points are taken at the same interval on the GIS metal shell, and the relationship between the induced current value and the grounding position of each phase ground section is calculated, and the relationship between the ground network circulation value and the grounding position presents a U-shaped curve. Take the minimum in the middle ground position.

Further, reducing the distance between phases, increasing the radius of the housing or/and increasing the number of grounding points can effectively suppress the circulation of the housing.

Further, at least one point of the shell of the GIS bus is grounded, and the grounding wire is connected to the ground grid, so as to reduce the transient potential on the shell.

Furthermore, adjusting the position of the grounding point, reducing the value of grounding inductance, increasing the number of grounding points or/and installing lightning arresters can effectively suppress TGPR.

Furthermore, the installation of grounding devices at the GIS bushing has a restraining effect on the grounding point and the TGPR of each point.

Compared with prior art, the beneficial effect of the present invention is:

1. The process of constructing the model in the present invention is simple, and the constructed model can reflect the real situation of the power system, which plays an important role in establishing a safe and smart grid;

2. The present invention adopts the PEEC method to establish the model of the GIS bus bar and the shell, and performs simulation and analysis on the basis of this, and obtains measures to effectively suppress the circulation of the shell and effectively suppress TGPR, and provides support for power grid protection and control adjustment.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application.

Fig. 1 is the schematic diagram of unit PEEC model of the present invention;

Fig. 2 is the schematic diagram of GIS busbar division among the present invention;

Fig. 3 is a schematic diagram of CIMC GIS shell division in the present invention;

Fig. 4 is the schematic diagram of the equivalent circuit of grounding body of the present invention;

Fig. 5 is the equivalent circuit schematic diagram of GIS shell circulation of the present invention;

Fig. 6 is a schematic diagram of the relationship between the grounding position and the circulating current value of the present invention;

Fig. 7 is a schematic diagram of the relationship between the grounding position and the interphase circulation of the present invention;

Fig. 8 is a schematic diagram of the relationship between phase distance and circulation in the present invention;

Fig. 9 is a schematic diagram of the relationship between the shell radius and the circulation of the present invention;

Fig. 10 is a schematic diagram of the relationship between grounding distance and circulating current in the present invention.

Detailed ways:

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.

In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom" etc. indicate The orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only a relative term determined for the convenience of describing the structural relationship of the various components or elements of the present invention, and does not specifically refer to any component or element in the present invention, and cannot be understood as a reference to the present invention. Invention Limitations.

In the present invention, terms such as "fixed", "connected" and "connected" should be understood in a broad sense, which means that they can be fixedly connected, integrally connected or detachably connected; they can be directly connected or can be connected through the middle The medium is indirectly connected. For relevant researchers or technical personnel in the field, the specific meanings of the above terms in the present invention can be determined according to specific situations, and should not be construed as limitations on the present invention.

As introduced in the background technology, in the prior art, the components of the GIS system are relatively close to each other, and the electromagnetic coupling between the components is strong. fast transient process. The transient wave generated in GIS has the characteristics of short delay and high frequency. The rise time of these transient waves is nanoseconds, and the frequency can reach hundreds of megahertz. Through electromagnetic induction, it appears as a bus sleeve The overvoltage with extremely high amplitude and frequency on the tube produces a steep transient circulating current on the metal casing of the GIS, and contains extremely high frequency harmonic components. In addition, because the transient circulating current generated in GIS has high-frequency and ultra-high-frequency components, and the layout of GIS cannot be consistent with the distance from the ground current injection point, it will cause the TGPR (Transient Grounding Potential Rise) effect of GIS. Electromagnetic interference may be generated to the monitoring and measuring equipment on the secondary side, causing system malfunction and becoming a huge hidden danger to the normal and stable operation of the power system. In order to solve the above technical problems, this application proposes a GIS shell based on the PEEC method Circulating currents and transient earth potential rise modeling and analysis methods.

Mechanism of fast transient process

The generation mechanism of VFTO

The generation of VFTO (Very fast transient overvoltage) is mainly due to the rapid transient overvoltage caused by the arc restrike breakdown generated by various high-voltage switchgears such as GIS internal disconnectors and circuit breakers. The operation of arc extinguishing equipment is the most important cause of VFTO. The rise time of the VFTO transient wave generated by the isolation switch operation is very short, about 5-20ns, and the voltage rise rate can reach 40MV/S. The amplitude is in the range of 2.0-2.5pu. The waveform and various indicators of VFTO are related to the parameter configuration of each component of the circuit. The most important is determined by the formation time of the arc, that is, the time required for the contact gap to completely break down and conduct from the beginning of charge dissociation. The smaller the value, the steeper the waveform of VFTO.

Fast transient overvoltage in GIS can be divided into internal transient overvoltage and external transient overvoltage. The normal operation of various equipment is affected. External transient overvoltage is the main cause of transient ground potential rise. The high-frequency transient overvoltage on it will radiate outward in the form of high-frequency electromagnetic waves, which will affect the normal operation of power system relay protection equipment and monitoring equipment. make a large impact.

Mechanism of shell circulation

In the GIS system, various high-voltage switchgears are hermetically placed in metal casings, and there are electromagnetic couplings between the busbar and the metal casing, and between the metal casing and the grounding grid. When the VFTO generated by the operation of the isolating switch and circuit breaker will generate a circulating current on the metal casing of the GIS.

Taking the most widely used three-phase split structure in the existing GIS system as an example, under the three-phase symmetrical operation, there is basically no circulating current on the metal casing. And there will be a high value of circulation between the shell and the grounding grid, because when the system is in normal operation, the grounding part of the shell adopts a segmented insulation method, which has a very good suppression effect on the circulation between the shell and the ground. However, when a serious fault occurs in the system, the voltage between the shell and the ground will increase sharply, the insulation gap will be broken down, the resistance to the ground will decrease rapidly, and a large value of circulating current between the shell and the ground will be formed.

Mechanism of TGPR production

In the ultra-fast transient process, because the grounding wire of the GIS system is long and the impedance is high, when the ultra-fast transient current with a high frequency propagates on it, the potential of the grounded shell will rise rapidly in a short time. High, there is a transient voltage with a high amplitude on the GIS shell, and the amplitude can reach up to 100kV. The main reasons for TGPR are as follows: First, the SF6 medium in the GIS has a high electric strength compared to air, but once it is broken down, its electric strength will drop instantly, and the voltage will rise sharply, which is very easy to break down. The high-frequency oscillation is caused in the whole system, which causes the transient ground potential to rise; the second is that the voltage on the bus is high and the ground clearance is short, which leads to the breakdown of the air gap, which causes the potential to rise; When the circuit breaker or isolating switch is in operation, the gas between the two contacts is broken down by arc reignition; the fourth is the transient ground potential rise caused by the discharge of the external concentrated capacitor used for reactive power compensation or voltage adjustment; the last one is The high-frequency current wave is reflected multiple times at the fracture of the shell, resulting in a very high voltage.

Basic theory of PEEC method

The PEEC model is an equivalent circuit model derived from Maxwell's equations. To use this method, the research object must first be divided into small enough microelements, and then the self, mutual inductance and self, mutual inductance and self, Mutual capacitance, and then construct a specific circuit model according to the actual structure of the object, and finally use the circuit analysis method to calculate the equivalent circuit, thus realizing the analysis of the electromagnetic coupling relationship of the research object. Since the PEEC model is derived from Maxwell's equations, after considering the propagation delay of electromagnetic waves, the model can fully describe the specific state of the object under the coexistence of electric and magnetic fields. In recent years, some scholars have begun to apply the PEEC method to the electromagnetic transient analysis of multi-conductor systems, and regard the PEEC model as a multi-port circuit model in order to connect with the traditional circuit model, thus realizing the PEEC model. The scope of application extends from microcircuits to the goal of multi-conductor large-scale electromagnetic systems. Based on the research results of predecessors such as Coulomb, Ampere and Faraday, Maxwell obtained the basic equations of time-varying electromagnetic fields. Among them, there are three independent equations in Maxwell's electromagnetic field equations, which are:

is the magnetic field strength, is the conduction current density, is the electric flux density, is the electric field strength, is the magnetic flux density, ρ _f is the charge density.

Take the divergence on both sides of (3-1) and (3-2), and substitute (3-3) into (3-1) to get

In the above five equations, The four vectors are the basic electromagnetic field quantities, ρ _f is the basic field source. In the time-varying electromagnetic field, there are the following relations:

Among them: μ is the magnetic permeability, ε is the electrical conductivity.

Introduce magnetic vector potential

Applying the PEEC method to establish a model needs to consider the effect of externally applied voltage, and the integral of the electric field can be written as:

In different cells, the current density mainly comes from four parts: conduction current, conduction source component magnetization current, displacement source component magnetization current and polarization current. Integrating the full current in the volume unit Vi gives the following:

In the formula, is the conduction current density, is the magnetizing current density of the conduction source, is the magnetization current density of the displacement source, is the polarization current density, R _ci and R _cmi are the resistance generated by the conduction current and the magnetization current of the conduction source respectively, C _dmi and C _pi are the capacitance and the polarization current generated by the magnetization current of the displacement source, respectively generated capacitance.

The PEEC model of the cell, in addition to considering the current equivalent, also needs to consider the influence of the surface charge on the potential of each node. The potential Ψ of each unit of the cell and the electric quantity Q can be related by the capacitance coefficient matrix C and the potential coefficient matrix P, as shown in the following formula:

The potential at r1 can be expressed as:

Divide the jth building block unit into Nj small units, and the charge density on the small unit is constant, the above formula can be expressed as:

In the formula: Si and Sj are respectively the area of the i-th and j-th cells and the total area of the N component units, and the defined potential coefficient matrix pij is as follows:

Combining the above equations, the full-current PEEC model of the cell after considering the surface charge can be obtained as shown in Figure 1.

1 PEEC model of GIS bus bar and enclosure

When the busbar passes through the AC signal, there will be a skin effect in the busbar, and the charge will be concentrated in the "skin" position of the busbar. Usually, a hollow conductive rod can be used instead of a solid wire.

The formula for calculating skin depth is:

Among them: r is the electrical conductivity of the conductive rod, μ is the magnetic permeability.

When carrying out the PEEC method equivalent to the busbar, select the rectangular cell whose height is smaller than the skin depth as the unit cell, and in these cells, the charge density can be approximately considered to be uniform. In cell division, the cell length is taken as 1m. The cell division of the busbar is shown in Figure 2.

For a cuboid cell, the calculation formula of its partial self-inductance can be approximated as:

Where: u is the cell aspect ratio.

In the cell division of the busbar, the spatial positions of different cells are spatially parallel, and the calculation formula for their partial mutual inductance is:

Among them: l is the length of the cell, h is the distance between two parallel cells.

Then the partial inductance of the GIS bus is:

Among them, K is the number of cells divided by the bus, that is, the partial inductance is the sum of the partial self-inductance and partial mutual inductance calculated above. When the cell space distance is not very small, the value of K can get a result with high precision without being too large.

For the GIS shell, since the induced electrical signal of the shell is also an AC signal, the shell can be treated similarly to the busbar, and the shell can be divided into cuboid cells, as shown in Figure 3.

The calculation of some parameters of the shell is similar to that of the busbar, and will not be repeated here.

switch part model

Using the isolating switch model proposed by Siemens, it is regarded as a model of time-varying resistance, and the resistance can be expressed by an exponential function:

Wherein, τ=1ms is the time constant; r ₀ =0.5Ω is the static resistance value, and R ₀ =10 ¹² Ω is the resistance before the switch gap breaks down. The two sides of the fracture are represented by capacitance to ground, and the value is tens of pF.

For the transformer, the model of the entrance capacitance is adopted, and the calculation formula of the entrance capacitance is:

Among them, for several components such as insulators, voltage transformers, and lightning arresters, the capacitance to ground of concentrated parameters is used to represent, and the bushing can be represented by wave impedance and capacitance to ground.

ground body model

The grounding grid is connected into a network by multiple grounding bodies. The references show that the coupling between the grounding bodies can be ignored, so the Π-type equivalent circuit of the grounding bodies is composed, as shown in Figure 4.

The parameters of the grounding body can be expressed by the resistance R, conductance G, inductance L and capacitance C per unit length, and the calculation formula is:

Among them, ρ _D is the resistivity of the grounding body, ρ is the resistivity of the soil, h is the buried depth, r is the radius of the grounding body, and l is the length of the grounding body.

In order to study the circulation characteristics, the PEEC method is used to establish an equivalent model as shown in Fig. 5.

Assuming that the soil resistivity is 20Ω·m, the inductance between the busbar grounding is equivalent to L _s = 1μH, and the method of combining horizontal grounding body segments and vertical grounding body segments is selected to simulate the grounding device.

Circulation analysis

Take 5 grounding points at the same interval on the GIS metal shell, and calculate the relationship between the induced current value of each phase grounding segment and the grounding position. The specific relationship is shown in Figure 6.

It can be seen from the figure that the relationship between the ground network circulation value and the grounding position presents a U-shaped curve, and the minimum value is obtained at the middle grounding position. The minimum value of phase B in the figure appears at grounding point 4. The reason for this situation may be that the number of grounding points is slightly less.

In order to study the circulation characteristics between phases, two phases are selected for analysis, and the size of the circulation between the two phases changes approximately in a U shape with the grounding position, that is, the change trend of the circulation between the GIS shells and the current between the grounding points is the same .

Take the interphase distance between the two phases as 1m, 2m, 3m, 4m, 5m respectively. Calculate the maximum circulation value under each phase spacing of GIS.

It can be seen from Figure 8 that with the increase of the interphase distance, the magnitude of the induced current between the phases of the GIS shell will increase, and it will tend to be stable after the interphase distance reaches a certain value.

Take the shell radius as 0.2m, 0.3m, 0.4m, 0.5m, 0.6m, 0.7m respectively, and calculate the circulation current at the grounding end of the GIS shell under different circumstances.

It can be seen from Figure 9 that as the shell radius increases, the interphase circulation decreases.

According to the above model, respectively calculate the size of the GIS shell grounding end circulation when the distance between the grounding points is 20m, 40m, 60m, and 80m.

From the analysis in Figure 10, it can be seen that when the grounding distance is increased, the phase-to-phase current will increase to a certain extent. It can be seen that increasing the number of grounding points and shortening the distance between grounding points can reduce the induced current between phases.

In order to ensure the safety of GIS operation, at least one point of the shell of the busbar is grounded. The ground wire is connected to the ground grid, and this ground wire can reduce the transient potential on the housing.

On the GIS busbar shell, 6 points are selected from near to far from the bushing, and node 1 is the connection point between the bushing and the overhead line. The ground wire can reduce the transient potential on the case. The influence of factors such as the position, quantity and inductance value of the grounding wire of the GIS shell and the number of grounding points of the GIS shell on the TGPR is analyzed through simulation calculations.

When the grounding point is at nodes 1 and 6 (node 1 is the connection between the bushing and GIS), the calculated TGPR amplitude of each point is compared with the TGPR amplitude of the grounding point at nodes 2 and 6 as follows:

Table 1 Comparison of TGPR values at different grounding points

It can be seen from Table 1 that the closer the grounding wire is to the GIS bushing, the TGPR amplitude of each node will be significantly reduced. It can be seen that if the grounding device is installed at the GIS bushing, it will have a good suppression effect on the grounding point and the TGPR of each point.

Change the inductance of the ground wire to 0.2μH/m, and the calculated TGPR amplitude of each point is compared with the original situation as follows. It can be seen that the TGPR amplitude decreases significantly with the decrease of ground wire inductance. Therefore, the height of the bus barrel can be reduced to reduce the length of the grounding lead, thereby reducing the inductance of the grounding wire, thereby achieving the effect of reducing the TGPR value.

Table 2 Influence of ground wire inductance value on TGPR

In order to study the relationship between the circulation value and the number of grounding points, the TGPR amplitudes were calculated when the grounding point positions were 1 and 6 and when the grounding point positions were 1, 3, and 5, and compared in a table.

Table 3 Impact of the number of grounding points on TGPR

It can be seen from Table 3 that the more grounding points of the shell, the lower the TGPR value of each point.

Metal oxide surge arresters have good steep wave response characteristics and can suppress TGPR similar to VFTO. Metal oxide arresters are mainly used to suppress TGPR at both ends of insulating flanges.

Table 4 Effect of metal oxide surge arresters on TGPR

It can be seen that the installation of metal oxide arresters can effectively reduce the amplitude of TGPR.

The present invention introduces the generation mechanism of the circulation in the GIS system and the transient state to the ground potential rise, adopts the PEEC method to establish the model of the GIS busbar and the shell, and the analysis results show that: the amplitude of the GIS interphase circulation and the ground network circulation and There is a U-shaped curve between the grounding points, and the larger value of the circulation appears at the connection point between the bushing and the busbar; considering the circulation between phases, reducing the distance between phases, increasing the radius of the shell, and increasing the number of grounding points can effectively suppress the circulation of the shell; Adjusting the position of the grounding point, reducing the value of grounding inductance, increasing the number of grounding points, and installing lightning arresters can effectively suppress TGPR.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (10)

1. A method for modeling and analyzing GIS shell circulation and transient ground potential rise based on the PEEC method, characterized in that: on the basis of the mechanism of circulation and transient ground potential rise in the GIS system, the PEEC method is adopted Establish the model of the GIS busbar and the shell, and then construct the equivalent model, and carry out simulation to obtain the relationship curve between the amplitude of the GIS interphase circulation and the ground network circulation and the grounding point, and determine the influencing factors of the shell circulation and TGPR according to the relationship curve. 2. A kind of GIS shell circulation and transient ground potential rise modeling and analysis method based on PEEC method as claimed in claim 1, it is characterized in that: the waveform of the fast transient overvoltage in the GIS system is determined by the formation time of the electric arc , that is, the time required for the contact gap to completely breakdown and conduct from the beginning of charge dissociation, the smaller the value of this time, the steeper the waveform of the fast transient overvoltage. 3. A kind of GIS enclosure circulation and transient ground potential rise modeling and analysis method based on PEEC method as claimed in claim 1, it is characterized in that: reduce phase-to-phase distance, increase enclosure radius or/and increase the number of grounding points can effectively Suppresses shell circulation. 4. A kind of PEEC-based GIS shell circulation and transient ground potential rise modeling and analysis method as claimed in claim 1, characterized in that: adjust the grounding point position, reduce the grounding inductance value, increase the number of grounding points or/and increase Installing arresters can effectively suppress TGPR. 5. A kind of GIS shell circulation and transient ground potential rise modeling and analysis method based on PEEC method as claimed in claim 1, it is characterized in that: when adopting PEEC method to set up the model of GIS busbar and shell, will be divided by research object Form small enough micro-elements, calculate the self-inductance, mutual inductance and self-intercapacitance of each micro-element, build a specific circuit model according to the actual structure of the object, and use the method of circuit analysis to calculate the equivalent circuit, so as to realize the electromagnetic analysis of the research object. Analysis of Coupling Relationships. 6. A kind of GIS shell circulation and transient earth potential rise modeling and analysis method based on PEEC method as claimed in claim 1, it is characterized in that: the model that PEEC method is constructed will be regarded as a multi-port circuit model, and traditional The circuit model is connected to achieve the goal of extending the scope of application of the PEEC model from microcircuits to multi-conductor large-scale electromagnetic systems. 7. A kind of GIS shell circulation and transient earth potential rise modeling and analysis method based on PEEC method as claimed in claim 1, it is characterized in that: when constructing the PEEC model of GIS shell, the shell is divided into rectangular parallelepiped cell, successively Calculate the self-inductance value of the cuboid cell, regard the spatial positions of different cells as parallel in space to calculate the mutual inductance value, add the self-inductance value and the mutual inductance value to obtain the inductance value of the GIS shell. 8. A kind of GIS shell circulation and transient ground potential rise modeling and analysis method based on PEEC method as claimed in claim 1, it is characterized in that: when constructing the PEEC model of GIS busbar, when busbar passes AC signal, in There will be a skin effect in the busbar, and the charge is concentrated on the outer surface of the busbar. The hollow conductive rod is used instead of the solid wire, and then the skin depth is calculated. When the PEEC method is equivalent to the busbar, the rectangular element whose height is smaller than the skin depth is selected. In these cells, the charge density is considered to be uniform, and the self-inductance value of the unit cell is calculated. In the cell division of the bus, the spatial positions of different cells are spatially parallel, so as to calculate Mutual inductance value, add the self-inductance value and mutual inductance value to get the inductance value of the GIS bus. 9. A kind of PEEC-based GIS enclosure circulation and transient ground potential rise modeling and analysis method as claimed in claim 1, characterized in that: build a grounding body model, and connect a plurality of grounding bodies into a network according to the grounding grid , ignoring the coupling between the ground bodies, a Π-type equivalent circuit of the ground bodies is formed. 10. A method for modeling and analyzing GIS shell circulation and transient ground potential rise based on the PEEC method as claimed in claim 1, characterized in that: installing a grounding device at the GIS bushing can inhibit the grounding point and the TGPR of each point effect.