GIL grounding device and design method thereof

Abstract

The invention discloses a GIL grounding device and a design method thereof. The method comprises the following steps: obtaining structure parameters and operation parameters of a gas insulated transmission line; calculating electrical parameter values of the gas insulated transmission line, wherein the electrical parameter values comprise capacitance, inductance and alternating-current resistance values of the gas insulated transmission line; according to experience and engineering practice, the number and positions of grounding points are selected, the grounding resistance value of each grounding point is determined, and a grounding system arrangement scheme is obtained; building an equivalent circuit of the gas insulated transmission line; performing electromagnetic transient simulation on the equivalent circuit, and determining the shell potential of each point on the shell of the gas insulated transmission line when the transmission line has a short-circuit fault; and verifying whether the maximum shell potential is lower than the critical value of the contact voltage, and if the shell potential is higher than the critical value of the contact voltage, performing design optimization of the grounding device. The condition that the potential of the shell is too high due to failure of a single means can be avoided, the reliability of a grounding system is improved, and a guarantee is provided for safe and stable operation of a gas insulated transmission line.

Description

Technical Field

[0001] The present invention belongs to the technical field of grounding design, and more specifically, relates to a grounding device of a GIL and a design method thereof. Background Art

[0002] With the development of power systems, more and more gas insulated transmission lines (GIL) are used in the field of power transmission and transformation. When the GIL equipment is operating normally or a short circuit occurs, the GIL shell will generate a significant induced potential, threatening the safe operation of the GIL and the safety of the staff; designing a suitable GIL grounding system can effectively suppress the increase in the GIL shell potential.

[0003] At present, the main method used in engineering is to increase the number of grounding points to ensure that the GIL shell potential is reduced to below the safe value. However, the single method of increasing the number of grounding points will inevitably increase the amount of GIL engineering, and when there is a terrain that is not easy to use as a grounding point in the line, the grounding arrangement method of conventional gas-insulated transmission lines is difficult to implement, which may lead to the problem of excessively high shell potential. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a grounding system design method for suppressing the potential increase of the casing of a gas-insulated transmission line.

[0005] The present invention adopts the following technical solution.

[0006] A first aspect of the present invention provides a method for designing a grounding device of a GIL, comprising the following steps:

[0007] Step 1, obtaining structural parameters and operating parameters of a gas-insulated transmission line;

[0008] Step 2, calculating electrical parameter values ​​of the gas-insulated transmission line according to the structural parameters and the operating parameters, including capacitance, inductance and AC resistance values ​​of the gas-insulated transmission line;

[0009] Step 3: According to experience and engineering practice, select the number and location of grounding points, determine the grounding resistance value of each grounding point, and obtain the grounding system layout plan;

[0010] Step 4, constructing an equivalent circuit of the gas-insulated transmission line according to the capacitance, inductance and AC resistance values ​​of the gas-insulated transmission line calculated in step 2 and the grounding system layout plan in step 3;

[0011] Step 5, performing electromagnetic transient simulation on the equivalent circuit to determine the shell potential of each point on the shell of the gas-insulated transmission line when a short circuit fault occurs in the transmission line;

[0012] Step 6, verify whether the maximum shell potential is lower than the critical value of the contact voltage. If the shell potential is lower than the critical value of the contact voltage, the design scheme is feasible; if the shell potential is higher than the critical value of the contact voltage, return to step 3 to optimize the grounding device design.

[0013] Preferably, in step 1, the structural parameters obtained include the inner and outer diameters of the shell of the gas-insulated transmission line, the inner and outer diameters of the conductors, and the layout of the three-phase transmission line; the operating parameters obtained include the voltage level of the transmission line, the current value and frequency value of the three-phase bus.

[0014] Preferably, finite element calculation is used to obtain the electrical parameter values ​​of the gas-insulated transmission line in step 2, including the capacitance, inductance and AC resistance values ​​of the gas-insulated transmission line.

[0015] Preferably, the capacitance of the gas insulated transmission line is calculated using the following formula:

[0016]

[0017] Where:

[0018] W e is the electric field energy per unit length of gas-insulated transmission line;

[0019] S is the reference cross section;

[0020] ε is the relative dielectric constant;

[0021] E is the electric field strength;

[0022] C is the self-capacitance per unit length;

[0023] V is the voltage between the conductor and the shell.

[0024] Preferably, the inductance of the gas-insulated transmission line is calculated using the following formula:

[0025]

[0026] Where:

[0027] W m is the magnetic field energy per unit length;

[0028] S is the reference cross section;

[0029] μ is the relative magnetic permeability;

[0030] B is the magnetic field strength;

[0031] L1 is the self-inductance of the housing per unit length;

[0032] L2 is the conductor self-inductance per unit length;

[0033] I1 is the current on the shell;

[0034] I2 is the current on the conductor;

[0035] M is the mutual inductance between the shell and conductor.

[0036] Preferably, the AC resistance of the gas-insulated transmission line is calculated using the following formula:

[0037]

[0038] Where:

[0039] P0 is the energy lost per unit length;

[0040] ρ is the material resistivity;

[0041] J is the current density;

[0042] R is the AC resistance per unit length;

[0043] I is the effective value of the current on the conductor or shell.

[0044] Preferably, the number and location of the grounding points in step 3 are selected according to the line length and the rated current of the busbar; the grounding resistance Z1~Z n The design value of is expressed as follows:

[0045]

[0046] Where:

[0047] |Z i | is the design value of the i-th grounding resistor, i∈{1,2,...,n};

[0048] exp is the exponential function;

[0049] α is a design parameter, which is set manually according to the circulating current and margin on the housing when a short circuit fault occurs;

[0050] V m It is the maximum allowable voltage design value of the shell;

[0051] ρ s is the ground resistivity of the working environment;

[0052] ρ k is the shell resistivity;

[0053] D is the sum of the distances between the ith grounding resistor and the two grounding resistors before and after it. The first and last grounding resistors are taken as twice the distance to the adjacent grounding resistors.

[0054] When the grounding system layout is initially determined, the grounding points are designed to be arranged at equal intervals.

[0055] Preferably, in step 4, the equivalent circuit of the gas-insulated transmission line includes: transmission line impedance, mutual inductance between the conductor and the casing, conductor-to-ground capacitance, phase-to-phase shorting bar, grounding resistance and current-conducting copper busbar.

[0056] Preferably, in step 6, the critical value of the contact voltage is calculated by the following formula:

[0057]

[0058] Where:

[0059] ρ s is the ground resistivity of the working environment;

[0060] t s The major failure time;

[0061] C s is the surface attenuation coefficient, which is determined based on the actual situation of the transmission line workplace.

[0062] A second aspect of the present invention provides a grounding device for a GIL, obtained using the design method for the grounding device for a GIL, comprising a grounding point, a grounding resistor, a grounding copper bus and a grounding grid, wherein the grounding point and the grounding resistor are optimized and adjusted according to the following modules, and the device further comprises:

[0063] A parameter acquisition module, used to acquire structural parameters and operating parameters of a gas-insulated transmission line;

[0064] Parameter conversion module, used to calculate the electrical parameter values ​​of gas-insulated transmission lines;

[0065] The grounding point layout module is used to select the number and location of grounding points, determine the grounding resistance value of each grounding point, and output the grounding system layout plan;

[0066] Equivalent circuit module, used to build the equivalent circuit of gas-insulated transmission lines;

[0067] A simulation calculation module is used to simulate the grounding current value in each grounding loop and the shell potential of each point on the shell of the gas-insulated transmission line when a short circuit fault occurs in the transmission line;

[0068] The voltage verification module is used to verify whether the maximum shell potential is lower than the critical value of the contact voltage, and to determine the feasibility of the grounding system layout scheme output by the grounding point layout module; if the shell potential is higher than the critical value of the contact voltage, it returns to the grounding point layout module for grounding system design optimization.

[0069] Compared with the prior art, the beneficial effects of the present invention include at least:

[0070] 1) The present invention adopts a combination of multiple means to design the grounding system of the gas-insulated transmission line, controls the shell potential to be lower than the engineering allowable value, avoids the situation where the shell potential is too high due to the failure of a single means, improves the reliability of the grounding system, and provides guarantee for the safe and stable operation of the gas-insulated transmission line.

[0071] 2) The present invention can avoid the problem of too many grounding points through the design of grounding resistance, thereby reducing the amount of engineering work.

[0072] 3) The present invention verifies the feasibility of the scheme by simulating the maximum shell potential and comparing it with the critical value of the contact voltage. Through repeated optimization, the suppression effect of the grounding system on the increase of shell potential can be ensured, thereby ensuring the safety of personnel and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 is a flow chart of a design method of a grounding device of a GIL provided in accordance with an embodiment of the present invention;

[0074] Figure 2 is a schematic diagram of a geometric model of a gas-insulated transmission line provided according to an embodiment of the present invention;

[0075] Figure 3 is a schematic diagram of a gas-insulated transmission line grounding system provided according to an embodiment of the present invention;

[0076] Figure 4 An equivalent circuit model of a gas-insulated transmission line provided according to an application example of the present invention;

[0077] Figure 5 It is a shell potential curve diagram before and after the grounding resistance value of the grounding system provided in accordance with the application example of the present invention is changed;

[0078] Figure 6 It is a shell potential curve diagram before and after the number of grounding points of the grounding system is changed according to the application example of the present invention. DETAILED DESCRIPTION

[0079] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0080] like Figure 1As shown, embodiment 1 of the present invention provides a design method for a grounding device of a GIL to suppress the potential increase of a gas-insulated transmission line casing, comprising the following steps:

[0081] Step 1, obtain the basic structural parameters and operating parameters of the gas-insulated transmission line; the geometric model of the gas-insulated transmission line is as follows: Figure 2 As shown, it includes a center conductor, epoxy resin insulator, aluminum alloy shell and internal insulating gas.

[0082] Preferably, the basic structural parameters that need to be obtained include the inner and outer diameters of the shell of the gas-insulated transmission line, the inner and outer diameters of the conductors, and the layout of the three-phase transmission line; the operating parameters that need to be obtained include the voltage level of the transmission line, the current value and frequency value of the three-phase bus, etc.

[0083] Step 2, calculating electrical parameter values ​​of the gas insulated transmission line;

[0084] In a preferred but non-limiting embodiment of the present invention, based on the basic structural parameters and operating parameters obtained in step 1, finite element calculation is used to calculate the electrical parameter values ​​of the gas-insulated transmission line, including the capacitance, inductance and AC resistance of the gas-insulated transmission line.

[0085] Further preferably, the capacitance of the gas insulated transmission line is expressed by the following formula:

[0086]

[0087] Where:

[0088] W e is the electric field energy per unit length;

[0089] ε is the relative dielectric constant;

[0090] E is the electric field strength;

[0091] C is the self-capacitance per unit length;

[0092] V is the voltage between the conductor and the shell.

[0093] Further preferably, the inductance of the gas-insulated transmission line is expressed by the following formula:

[0094]

[0095] Where:

[0096] W m is the magnetic field energy per unit length;

[0097] μ is the relative magnetic permeability;

[0098] B is the magnetic field strength;

[0099] L1 is the self-inductance of the housing per unit length;

[0100] L2 is the conductor self-inductance per unit length;

[0101] I1 is the current on the shell;

[0102] I2 is the current on the conductor;

[0103] M is the mutual inductance between the shell and conductor.

[0104] Further preferably, the AC resistance of the gas insulated transmission line is expressed by the following formula:

[0105]

[0106] Where:

[0107] P0 is the energy lost per unit length;

[0108] ρ is the material resistivity;

[0109] J is the current density;

[0110] R is the AC resistance per unit length;

[0111] I is the effective value of the current on the conductor or shell.

[0112] Step 3: According to experience and engineering practice, select the number and location of grounding points, determine the grounding resistance value of each grounding point, obtain the grounding system layout plan, and arrange the grounding system;

[0113] Preferably, the number and location of grounding points are selected according to the line length and the rated current of the busbar;

[0114] Preferably, the grounding resistances Z1 to Z2 of each grounding point are n The design value of is expressed as follows:

[0115]

[0116] Where:

[0117] |Z i | is the design value of the i-th grounding resistor, i∈{1,2,...,n};

[0118] exp is the exponential function;

[0119] α is a design parameter, which is set manually according to the circulating current and margin on the housing when a short circuit fault occurs;

[0120] V m It is the maximum allowable voltage design value of the shell;

[0121] ρ s is the ground resistivity of the working environment;

[0122] ρ k is the shell resistivity;

[0123] D is the sum of the distances between the i-th grounding resistor and the two grounding resistors before and after it. The first and last grounding resistors are taken as twice the distance to the adjacent grounding resistor.

[0124] By designing the grounding resistance of each grounding point according to the above formula, the number and position of grounding points can be flexibly adjusted under the premise of ensuring that the shell potential of the GIL does not exceed the allowable value, avoiding the problem of too many grounding points and reducing the amount of engineering. When there is a place on the GIL line that is difficult to be used as a grounding point due to objective conditions, the problem of poor grounding effect caused by blind adjustment can be avoided.

[0125] Further preferably, when the grounding system layout is initially determined, the grounding points may be arranged at equal intervals for design.

[0126] It can be understood that the present invention designs the grounding system by combining multiple means such as the number and position of grounding points and the grounding resistance value, which can avoid the situation where a single method cannot be implemented or fails, and effectively suppress the increase of the GIL shell potential.

[0127] Step 4, constructing an equivalent circuit of the gas insulated transmission line according to the electrical parameter values ​​calculated in step 2 and the grounding system layout plan in step 3;

[0128] Preferably, the construction of the equivalent circuit needs to include: transmission line impedance, mutual inductance between the conductor and the shell, conductor-to-ground capacitance, phase shorting bar, grounding resistor, and current guide copper busbar and other components.

[0129] Step 5, performing electromagnetic transient simulation on the equivalent circuit to determine the grounding current value in each grounding loop and the shell potential of each point on the shell of the gas-insulated transmission line when a short circuit fault occurs in the transmission line;

[0130] Preferably, based on electromagnetic transient simulation software, the grounding current value and the shell potential are simulated according to the gas-insulated transmission line equivalent circuit constructed in step 4.

[0131] Step 6, verify whether the maximum shell potential is lower than the critical value of the contact voltage. If the shell potential is lower than the critical value of the contact voltage, the design scheme is feasible; if the shell potential is higher than the critical value of the contact voltage, return to step 3 to optimize the grounding system design.

[0132] Preferably, the critical value of the contact voltage can be calculated by the following formula:

[0133]

[0134] Where:

[0135] ρ s is the ground resistivity of the working environment;

[0136] t s The major failure time;

[0137] C s is the surface attenuation coefficient, and its specific value is determined according to the actual situation of the transmission line workplace.

[0138] Preferably, when the shell potential is higher than the critical value of the contact voltage and the grounding system of the gas-insulated transmission line needs to be optimized, strategies such as reducing the grounding resistance value, increasing the number of grounding points or changing the layout of the grounding points can be adopted.

[0139] Embodiment 2 of the present invention provides a grounding device for a GIL, which is obtained by using the design method for the grounding device for a GIL described in Embodiment 1, as shown in FIG. Figure 3 As shown, it includes grounding point, grounding resistor, grounding copper bar and grounding grid. The grounding point and grounding resistor are optimized and adjusted according to the following modules, and also include:

[0140] A parameter acquisition module, used to acquire structural parameters and operating parameters of a gas-insulated transmission line;

[0141] Parameter conversion module, used to calculate the electrical parameter values ​​of gas-insulated transmission lines;

[0142] The grounding point layout module is used to select the number and location of grounding points, determine the grounding resistance value of each grounding point, and output the grounding system layout plan;

[0143] Equivalent circuit module, used to build the equivalent circuit of gas-insulated transmission lines;

[0144] A simulation calculation module is used to simulate the grounding current value in each grounding loop and the shell potential of each point on the shell of the gas-insulated transmission line when a short circuit fault occurs in the transmission line;

[0145] The voltage verification module is used to verify whether the maximum shell potential is lower than the critical value of the contact voltage, and to determine the feasibility of the grounding system layout scheme output by the grounding point layout module; if the shell potential is higher than the critical value of the contact voltage, it returns to the grounding point layout module for grounding system design optimization.

[0146] Application example: A grounding system is obtained by using the grounding system design method for suppressing the potential increase of the gas-insulated transmission line shell described in Example 1. The equivalent circuit model is as follows: Figure 4As shown in the figure, the grounding system is optimized by reducing the grounding resistance and increasing the number of grounding points. The shell potential before and after optimization is shown in Figure 5 , Figure 6 As shown in the figure, it can be seen that the shell potential is positively correlated with the grounding resistance value and negatively correlated with the number of grounding points. Through optimized design, the shell potential can be significantly reduced and the protection level of the grounding system can be improved.

[0147] Compared with the prior art, the beneficial effects of the present invention include at least:

[0148] 1) The present invention adopts a combination of multiple means to design the grounding system of the gas-insulated transmission line, controls the shell potential to be lower than the engineering allowable value, avoids the situation where the shell potential is too high due to the failure of a single means, improves the reliability of the grounding system, and provides guarantee for the safe and stable operation of the gas-insulated transmission line.

[0149] 2) The present invention can avoid the problem of too many grounding points through the design of grounding resistance, thereby reducing the amount of engineering work.

[0150] 3) The present invention verifies the feasibility of the scheme by simulating the maximum shell potential and comparing it with the critical value of the contact voltage. Through repeated optimization, the suppression effect of the grounding system on the increase of shell potential can be ensured, thereby ensuring the safety of personnel and equipment.

[0151] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0152] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for designing a grounding device of a GIL, characterized in that: The following steps are involved: Step 1, obtaining structural parameters and operating parameters of a gas-insulated transmission line; Step 2, calculating electrical parameter values ​​of the gas-insulated transmission line according to the structural parameters and the operating parameters, including capacitance, inductance and AC resistance values ​​of the gas-insulated transmission line; Step 3: According to experience and engineering practice, select the number and location of grounding points, determine the grounding resistance value of each grounding point, and obtain the grounding system layout plan; Step 4, constructing an equivalent circuit of the gas-insulated transmission line according to the capacitance, inductance and AC resistance values ​​of the gas-insulated transmission line calculated in step 2 and the grounding system layout plan in step 3; Step 5, performing electromagnetic transient simulation on the equivalent circuit to determine the shell potential of each point on the shell of the gas-insulated transmission line when a short circuit fault occurs in the transmission line; Step 6, verify whether the maximum shell potential is lower than the critical value of the contact voltage. If the shell potential is lower than the critical value of the contact voltage, the design solution is feasible; If the shell potential is higher than the critical value of the contact voltage, return to step 3 to optimize the grounding device design.

2. The method for designing a grounding device of a GIL according to claim 1, characterized in that: In step 1, the structural parameters obtained include the inner and outer diameters of the shell of the gas-insulated transmission line, the inner and outer diameters of the conductor, and the layout of the three-phase transmission line; the operating parameters obtained include the voltage level of the transmission line, the current value and frequency value of the three-phase bus.

3. The design method of the grounding device of the GIL according to claim 1, characterized in that: The electrical parameter values ​​of the gas-insulated transmission line in step 2 are obtained by finite element calculation, including the capacitance, inductance and AC resistance values ​​of the gas-insulated transmission line.

4. The method for designing a grounding device of a GIL according to claim 3, characterized in that: The capacitance of a gas-insulated transmission line is calculated as follows: Where: W e is the electric field energy per unit length of gas-insulated transmission line; S is the reference cross section; ε is the relative dielectric constant; E is the electric field strength; C is the self-capacitance per unit length; V is the voltage between the conductor and the shell.

5. The method for designing a grounding device of a GIL according to claim 3, characterized in that: The inductance of a gas-insulated transmission line is calculated as follows: Where: W m is the magnetic field energy per unit length; S is the reference cross section; μ is the relative magnetic permeability; B is the magnetic field strength; L1 is the self-inductance of the shell per unit length; L2 is the conductor self-inductance per unit length; I1 is the current on the shell; I2 is the current on the conductor; M is the mutual inductance between the shell and conductor.

6. The method for designing a grounding device of a GIL according to claim 3, characterized in that: The AC resistance of a gas-insulated transmission line is calculated using the following formula: Where: P0 is the energy lost per unit length; ρ is the material resistivity; J is the current density; R is the AC resistance per unit length; I is the effective value of the current on the conductor or shell.

7. The method for designing a grounding device of a GIL according to claim 1, characterized in that: Select the number and location of grounding points in step 3 according to the line length and busbar rated current; Grounding resistance Z1~Z of each grounding point n The design value of is expressed as follows: Where: |Z i | is the design value of the i-th grounding resistor, i∈{1,2,...,n}; exp is the exponential function; α is a design parameter, which is set manually according to the circulating current and margin on the housing when a short circuit fault occurs; V m It is the maximum allowable voltage design value of the shell; ρ s is the ground resistivity of the working environment; ρ k is the shell resistivity; D is the sum of the distances between the ith grounding resistor and the two grounding resistors before and after it. The first and last grounding resistors are taken as twice the distance to the adjacent grounding resistors. When the grounding system layout is initially determined, the grounding points are designed to be arranged at equal intervals.

8. The method for designing a grounding device of a GIL according to claim 1, characterized in that: In step 4, the equivalent circuit of the gas-insulated transmission line includes: transmission line impedance, mutual inductance between the conductor and the shell, conductor-to-ground capacitance, phase-to-phase shorting bar, grounding resistance and current-conducting copper bar.

9. The method for designing a grounding device of a GIL according to claim 1, characterized in that: In step 6, the critical value of the contact voltage is calculated by the following formula: Where: ρ s is the ground resistivity of the working environment; t s The major failure time; C s is the surface attenuation coefficient, which is determined based on the actual situation of the transmission line workplace.

10. A grounding device for GIL, obtained by using the design method for a grounding device for GIL according to any one of claims 1 to 9, comprising a grounding point, a grounding resistor, a grounding copper bar and a grounding grid, characterized in that: The grounding point and the grounding resistance are optimized and adjusted according to the following modules, and the device also includes: A parameter acquisition module, used to acquire structural parameters and operating parameters of a gas-insulated transmission line; Parameter conversion module, used to calculate the electrical parameter values ​​of gas-insulated transmission lines; The grounding point layout module is used to select the number and location of grounding points, determine the grounding resistance value of each grounding point, and output the grounding system layout plan; Equivalent circuit module, used to build the equivalent circuit of gas-insulated transmission lines; A simulation calculation module is used to simulate the grounding current value in each grounding loop and the shell potential of each point on the shell of the gas-insulated transmission line when a short circuit fault occurs in the transmission line; The voltage verification module is used to verify whether the maximum shell potential is lower than the critical value of the contact voltage, and to determine the feasibility of the grounding system layout scheme output by the grounding point layout module; if the shell potential is higher than the critical value of the contact voltage, it returns to the grounding point layout module for grounding system design optimization.

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