A method and system for calculating the safety limit of a GPR for a neutral grounding resonance grounding system

Abstract

This invention discloses a method and system for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding. Based on the basic principle of surge arresters used in substation GPR backflashover stations, a simulation model of a 10kV system is built to determine the backflashover characteristics of the surge arrester under different arc suppression coil configurations. The discharge current waveform and voltage waveform across the surge arrester are recorded during the 0.5s fault process. By recording the voltage and discharge current waveforms across the surge arrester during the fault process, the energy absorbed by the surge arrester under GPR backflashover is calculated through convolution. By recording the voltage change waveform across the surge arrester during the fault process, the mechanism of GPR backflashover of the surge arrester when the neutral point of the 10kV system is grounded via an arc suppression coil is determined. The determined line-to-ground capacitance value is input into the simulation model, and the energy absorbed by the surge arrester is compared with its current carrying capacity to verify the safety of the surge arrester under GPR backflashover, obtaining the GPR safety limit of the surge arrester under different line-to-ground capacitances. This accurately determines the surge arrester backflashover situation, avoiding safety accidents and losses.

Description

Technical Field

[0001] This invention belongs to the field of high voltage electrical technology, specifically relating to a method and system for calculating the safety limit of the surge arrester GPR when the neutral point is resonantly grounded. Background Technology

[0002] The grounding method of the neutral point in a 10kV power supply system is related to the capacitive current of a single-phase grounding fault. In the early stages of power system development, due to the low capacitive current of a single-phase grounding fault, the neutral point of a 10kV power supply system was generally ungrounded. With the increase in power system capacity and the promotion of power cables, the capacitive current of a single-phase grounding fault in a 10kV power supply system has increased dramatically. In order to compensate for the fault capacitive current, the method of grounding the neutral point through an arc suppression coil has gradually emerged.

[0003] Existing research on surge arresters for ground potential rise (GPR) backflashover in substations assumes the system neutral point is ungrounded, failing to consider the differences in GPR backflashover arresters under different neutral point grounding methods. Simply applying the GPR safety limit for arresters with an ungrounded neutral point could lead to significant economic losses, or even arrester explosions. For example, when the system neutral point is grounded via an arc suppression coil, the arrester's GPR safety limit is lower than the GPR safety limit when the neutral point is ungrounded. Applying previous calculations when the neutral point is grounded via an arc suppression coil could very likely cause thermal breakdown and explosion of the arrester!

[0004] Therefore, it is necessary to study the mechanism of GPR backflash arrester and the calculation method of GPR safety limit under the system neutral point grounding through arc suppression coil. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for calculating the GPR safety limit of surge arresters when the neutral point is resonantly grounded, in order to address the shortcomings of the prior art. This method solves the technical problem that the GPR safety limit of station surge arresters cannot be calculated when the neutral point grounding method of the power system of the plant / station is resonant grounding.

[0006] The present invention adopts the following technical solution:

[0007] A method for calculating the safety limit of the surge arrester's GPR during neutral point resonant grounding includes the following steps:

[0008] S1. Based on the principle of GPR (Grounding PR) surge arrester for substations, a simulation model of the power system of the plant / station is built. GPR refers to the ground potential rise of the grounding grid.

[0009] S2. For the surge arresters of existing power plants, verify the safety of the arc suppression coil configuration scheme and the line-to-ground capacitance obtained in step S1 by inputting them into the power system simulation model of the plant / station.

[0010] S3. Based on the simulation model of the power supply system of the plant / station obtained in step S1 and the parameters of the simulation model of the power supply system of the plant / station obtained in step S2, determine the discharge current waveform and the voltage waveform at both ends of the surge arrester in the fault process of 0.5s, and perform integral calculation along time to obtain the energy absorbed by the surge arrester under GPR backflash.

[0011] S4. For the surge arresters of the existing power station, compare the energy absorbed by the surge arrester under GPR backflash obtained in step S3 with the set current carrying capacity of the surge arrester. When the energy absorbed by the surge arrester is greater than the set current carrying capacity of the surge arrester, the surge arrester has a safety risk. The safety of the surge arrester under GPR backflash is verified.

[0012] Specifically, in step S1, the simulation model of the power supply system of the plant / station is as follows:

[0013] This includes a high-voltage busbar, with one end grounded and the other end branching into four paths. Paths one, two, and three are connected to one end of the corresponding plant / station power supply system busbar. The other end of the corresponding plant / station power supply system busbar branches into two paths: one path is grounded via its corresponding grounding capacitor, and the other path is connected via a parallel nonlinear resistor, a surge arrester grounding capacitor, and the transformer 10kV side inlet capacitor C. B After being raised to ground potential, the fourth path passes through the arc suppression coil inductor L and the matching damping resistor R in sequence. L After the ground potential is raised, it is grounded, and a switch is connected in parallel across the two ends of the ground potential rise.

[0014] Specifically, in step S2, the surge arrester's backflash characteristics under different arc suppression coil configurations are as follows:

[0015] When the capacitive current of a single-phase ground fault in the power supply system of a plant / station is greater than 10A but less than 100A to 150A, a neutral point grounding method via an arc suppression coil is adopted, and the line-to-ground capacitance C... L The range is 1.5–30 μF.

[0016] Furthermore, the arc suppression coil satisfies the following conditions:

[0017]

[0018] Where ρ is the grid damping ratio, K C denoted by , and v by , which represents the degree of asymmetry.

[0019] Specifically, in step S2, for the surge arresters of the power station under construction, the parameters of the simulation model of the power system of the plant / station are set according to the quantitative relationship between the arc suppression coil and the line-to-ground capacitance, and the backflash characteristics of the surge arresters under different arc suppression coil configurations are determined. Based on the backflash characteristics of the surge arresters under different arc suppression coil configurations, the backflash characteristics of the GPR backflash arrester when the neutral point of the power system of the plant / station is grounded through the arc suppression coil are determined by the voltage change waveform across the surge arrester during the fault process. Using the backflash characteristics of the GPR backflash arrester when the neutral point of the power system of the plant / station is grounded through the arc suppression coil, different line-to-ground capacitances C are used. L The energy absorbed by the surge arrester under GPR backflash is calculated using a step-size interval, and compared with the set current-carrying capacity of the surge arrester to obtain the surge arrester's GPR safety limit under neutral point resonant grounding as a function of the line-to-ground capacitance C. L The changes.

[0020] Furthermore, the specific backflashover characteristics of the GPR backflash arrester are as follows:

[0021] Oscillations occur in the circuit between the arc suppression coil and the line-to-ground capacitance. The voltage across the surge arrester due to the backflashover of the GPR is higher than the sum of the GPR and the bus voltage. At this point, the voltage across the surge arrester is higher than the reference voltage, causing the surge arrester to break down and discharge. Based on the detuning degree v and the grid damping rate ρ, the bus voltage U... xge The phase and amplitude changes are consistent with those of the GPR backflash arrester. The voltage across the GPR backflash arrester does not decrease with the decay of the GPR, and the arrester repeatedly breaks down during the fault process.

[0022] Specifically, in step S3, the energy W absorbed by the surge arrester under GPR backflash is as follows:

[0023]

[0024] Where P(t) is the discharge power of the surge arrester, u(t) and i(t) are the voltage and discharge current across the surge arrester, respectively, and t0 is the duration of the fault.

[0025] Secondly, embodiments of the present invention provide a system for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding, comprising:

[0026] The simulation module builds a simulation model of the power system of the plant / station based on the principle of GPR backflash surge arrester in the substation. GPR refers to the ground potential rise of the grounding grid.

[0027] The parameter module verifies the safety of the power system simulation model of the power plant / station using the arc suppression coil configuration scheme and line-to-ground capacitance input to the simulation module for the surge arresters of the existing power plant.

[0028] The recording module, based on the simulation model of the power supply system of the plant / station obtained by the simulation module and the parameters of the simulation model of the power supply system of the plant / station obtained by the parameter module, determines the discharge current waveform and the voltage waveform at both ends of the surge arrester in the 0.5s fault process, and performs integral calculation along time to obtain the energy absorbed by the surge arrester under GPR backflash.

[0029] The calculation module compares the energy absorbed by the surge arrester under GPR backflash, obtained from the recording module, with the set current capacity of the surge arrester. When the energy absorbed by the surge arrester is greater than the set current capacity, the surge arrester has a safety risk. The safety of the surge arrester under GPR backflash is verified.

[0030] Thirdly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding.

[0031] Fourthly, embodiments of the present invention provide a computer-readable storage medium including a computer program, which, when executed by a processor, implements the steps of the above-described method for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] This invention provides a method for calculating the GPR safety limit of a surge arrester under neutral point resonant grounding. It accurately calculates the GPR withstand limit of the surge arrester in a power system where the neutral point is grounded via an arc suppression coil. This is achieved by adjusting the arc suppression coil inductance L and damping resistance R. L and line capacitor C L Oscillation analysis and voltage division calculations of the equivalent circuit clarified the backflashover mechanism and characteristics of the surge arrester when the neutral point of the GPR in the power supply system of the plant / station is grounded through the arc suppression coil. The differences from previous studies were also clarified: unlike the ungrounded neutral point mode in the power supply system of the plant / station, the GPR acts on the LC... L On the circuit, an oscillating voltage is generated. The voltage acting on the surge arrester is the vector difference between the vector sum of the oscillating voltage and the bus voltage and the GPR, i.e., oscillating voltage + bus voltage - GPR. This is significantly different from the current research status and avoids the safety accidents that would occur if the original research results were directly adopted.

[0034] Furthermore, the simulation model significantly simplifies the substation topology, requiring only the station-level surge arrester's operating circuit to be constructed. Line-to-ground capacitance is used to simulate line parameters, simplifying the calculation of line impedance, as the line impedance is relatively small and has no impact on the GPR backflash arrester. The high-voltage side of the transformer is used to simulate the substation's high-voltage system power supply, greatly simplifying the simulation model, as the high-voltage side power supply does not change with faults and has no impact on the GPR backflash arrester. A variable resistor is used to simulate the surge arrester, accurately reflecting its volt-ampere characteristics. Using an S0 switch to control the ground potential rise and simulate the power supply's switching effectively simulates the suddenness of fault occurrence during normal system operation and the arrester's recovery after fault clearance. Simulating the ground potential rise using two power supplies in series effectively reflects the transient effect of the ground potential rise, and the transient component in the GPR has a significant and non-negligible impact on the surge arrester's GPR backflash process.

[0035] Furthermore, according to the "Design Code for Overvoltage Protection and Insulation Coordination of AC Electrical Installations", when the single-phase ground fault capacitive current of the system is greater than 10A but less than 100A to 150A, it is advisable to adopt the neutral point grounding method through the arc suppression coil. Based on the relationship between the single-phase ground fault capacitive current of the system and the system voltage level, the range of line-to-ground capacitance change corresponding to the range of single-phase ground fault capacitive current of the system can be calculated. The calculation range can be appropriately widened at the boundary of the range, which fully reflects the changing characteristics of the surge arrester under the GPR backflash under the neutral point grounding condition.

[0036] Furthermore, through oscillation analysis and voltage division calculation of the equivalent circuit of the arc suppression coil inductance L, damping resistance RL, and line-to-capacitor CL, the backflashback characteristics of the surge arrester when the neutral point of the GPR is grounded through the arc suppression coil in the power supply system of the plant / station were clarified, and the differences from the previous studies were identified: unlike the ungrounded neutral point mode in the power supply system of the plant / station, the GPR acts on the LC L On the circuit, an oscillating voltage is generated. The voltage acting on the surge arrester is the vector difference between the vector sum of the oscillating voltage and the bus voltage and the GPR, i.e., oscillating voltage + bus voltage - GPR. For different detuning degrees, as the detuning degree increases, the arc suppression coil inductance L and the line-to-ground capacitance C... L The further the value deviates from the resonance point, the lower the oscillation voltage generated in the current circuit, the lower the voltage the surge arrester withstands, the less energy it absorbs, and the greater its tolerance to the GPR safety limit. For different damping rates, as the damping rate increases, the damping resistor value increases, the damping resistor voltage division ratio increases, the surge arrester withstands a lower voltage, and the tolerance to the GPR safety limit increases.

[0037] Furthermore, the setting of high-voltage side power supply and ground potential rise simulation power supply can effectively simulate the occurrence and clearing of faults, and can clearly reflect parameters such as the discharge current waveform of the surge arrester before and after the fault; the surge arrester adopts variable resistance equivalent, which can effectively reflect the volt-ampere characteristics of the surge arrester, and can accurately simulate the process of the surge arrester being subjected to GPR backflash.

[0038] Furthermore, the backflashover characteristics of the GPR surge arrester can better reflect the special characteristics of the GPR surge arrester when the neutral point is grounded through the arc suppression coil. Unlike when the neutral point is not grounded, the GPR does not directly backflash over the arrester here, but rather triggers the LC... L The circuit oscillates, further causing the surge arrester to backfire and break down.

[0039] Furthermore, according to the "AC Gapless Metal Oxide Surge Arrester" standard, a surge arrester should be able to withstand 18 impacts of a 2ms square wave current. The amplitude of the square wave current that a surge arrester should withstand for different voltage levels can be found in the "AC Gapless Metal Oxide Surge Arrester" standard. Based on the surge arrester's volt-ampere characteristics, the energy absorbed by the surge arrester under a single 2ms square wave current impact can be calculated and used as the surge arrester's current carrying capacity. By comparing the energy absorbed by the surge arrester during a fault with its current carrying capacity, if the energy absorbed by the surge arrester is less than its current carrying capacity, the surge arrester is considered to have no risk of explosion; if the energy absorbed by the surge arrester is greater than its current carrying capacity, the surge arrester has a risk of explosion.

[0040] It is understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0041] In summary, this invention simplifies the simulation model, focuses on the important factors in the GPR backflash arrester process, and meticulously models these important factors in the simulation model. Combining the arrester's volt-ampere characteristics and current carrying capacity, it proposes a verification method for arrester energy calculation, highlighting the backflash characteristics of the GPR backflash arrester when the neutral point of the power system is grounded through an arc suppression coil, and accurately calculating the arrester's safety limit for GPR withstand under different operating conditions when the system neutral point is grounded through an arc suppression coil.

[0042] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0043] Figure 1 Schematic diagram of a 10kV surge arrester for ground potential rise backflashover;

[0044] Figure 2 Simulation model diagram of 10kV surge arrester for ground grid GPR backflashover;

[0045] Figure 3This is the equivalent circuit diagram of the GPR backflash arrester when the neutral point is grounded through the arc suppression coil;

[0046] Figure 4 The waveform of the surge arrester discharge current when the neutral point is grounded through the arc suppression coil;

[0047] Figure 5 The voltage waveform across the surge arrester when the neutral point is grounded via the arc suppression coil;

[0048] Figure 6 The waveform of the neutral point voltage in a 10kV system;

[0049] Figure 7 This is a graph showing the variation of the surge arrester's GPR safety limit with the single-phase-to-ground capacitance of the line when the neutral point is grounded via an arc suppression coil. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0052] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0053] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations. For example, A and / or B can represent three cases: A alone, A and B simultaneously, and B alone. Additionally, the character " / " in this document generally indicates that the preceding and following objects have an "or" relationship.

[0054] It should be understood that although terms such as first, second, third, etc., may be used in the embodiments of the present invention to describe the preset range, these preset ranges should not be limited to these terms. These terms are only used to distinguish the preset ranges from one another. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0055] Depending on the context, the word "if" as used here can be interpreted as "when," "when," "in response to determination," or "in response to detection." Similarly, depending on the context, the phrase "if determination" or "if detection (of the stated condition or event)" can be interpreted as "when determination," "in response to determination," "when detection (of the stated condition or event)," or "in response to detection (of the stated condition or event)."

[0056] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0057] This invention provides a method for calculating the safety limit of the surge arrester's ground velocity (GPR) during neutral point resonant grounding. By simplifying the topology of the substation surge arrester's operating line, it clarifies that the GPR acts on the arc suppression coil L-line-to-ground capacitance C. L When the circuit is in a loop, a loop oscillation voltage is generated, further worsening the surge arrester's resistance to GPR backflash. Therefore, when the system neutral point is grounded through an arc suppression coil, the surge arrester is affected by the arc suppression coil, and the surge arrester is subjected to backflash from the voltage component coupled to its ends by the GPR. This invention fills the gap in existing research on the safety limits of surge arresters' GPR tolerance, and improves the variation law of the safety limits of surge arresters' GPR tolerance under different neutral point grounding methods in the system. It can be used as a reference for verifying the safety limits of GPR in substation design. When the system neutral point is grounded through an arc suppression coil, the surge arrester's resistance to GPR backflash is even more severe. This invention can accurately determine the surge arrester's backflash situation and propose corresponding safety limits of surge arrester's GPR tolerance for specific operating conditions, effectively avoiding safety accidents and economic losses.

[0058] Please see Figure 1When the system neutral point is grounded through the arc suppression coil, the arc suppression coil and the line-to-ground capacitance will oscillate under the action of the GPR. The voltage division of the inductance and capacitance causes the bus neutral point voltage to oscillate accordingly. During the fault, the surge arrester continuously withstands a large voltage difference, and the energy flowing through it is more likely to exceed its current carrying capacity. g For ground potential rise, U xge The phase voltage of the 10kV line bus is given, and the equivalent capacitance C of the surge arrester is given. B Much smaller than the 10kV line-to-ground capacitance C L When the system neutral point is grounded through an arc suppression coil, U g Part of the voltage is coupled to the bus neutral point through the damping resistor and the inductance of the digestion coil, resulting in a certain degree of voltage cancellation across the surge arrester.

[0059] This invention provides a method for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding, comprising the following steps:

[0060] S1. Based on the basic principle of GPR backflash surge arresters for substations, build a simulation model of the power supply system of the plant / station.

[0061] The neutral point grounding method of the power supply system of the plant / station is resonant grounding.

[0062] Please see Figure 2 In the simulation model of the power supply system of the plant / station, u ABC Represents the high-voltage bus voltage; u sa u sb u sc C is the system bus voltage; L For the line-to-ground capacitance, its specific value is set according to the specific parameters of the station's surge arrester operating line; R B This is a nonlinear resistor used to simulate a surge arrester, and its setting is based on the surge arrester's volt-ampere characteristics; C B The sum of the surge arrester's capacitance to ground and the transformer's 10kV inlet capacitance is taken as 1000pF; g To account for the rise in ground potential and transient effects, u g From transient component u d and power frequency component u a It consists of two parts, namely u g =u d +u a transient component u d The peak value is set to the steady-state amplitude of GPR, and the power frequency component u a The peak value is set to the steady-state amplitude of GPR, u g The equivalent power source for ground potential rise considers the transient component of ground potential rise, taking its decay time constant as 0.05, and setting the fault duration to 0.5s. The GPR phase is set to be opposite to the phase of the A-phase bus voltage; L is the inductance value of the arc suppression coil, R... LTo match the damping resistor, set it according to the actual arc suppression coil configuration parameters. If it is necessary to study the surge arrester backflash characteristics under different arc suppression coil configurations, set the arc suppression coil parameter range according to step S2. S0 is a switch that controls the opening and closing of the ground potential rise simulation power supply, keeps the system stable during non-fault periods, and puts the ground potential rise simulation power supply into operation at a preset time to simulate the occurrence of a fault.

[0063] S2. For the surge arresters of existing power plants, verify the safety of the arc suppression coil configuration scheme and the line-to-ground capacitance obtained in step S1 by inputting them into the power system simulation model of the plant / station.

[0064] For surge arresters in power plants under construction, the parameters of the power system simulation model of the plant / station are set according to the quantitative relationship between the arc suppression coil and the line-to-ground capacitance, and the backflash characteristics of the surge arrester under different arc suppression coil configurations are determined.

[0065] Based on the backflash characteristics of surge arresters under different arc suppression coil configurations, the backflash characteristics of GPR surge arresters when the neutral point of the power system of the plant / station is grounded through the voltage change waveform across the surge arrester during the fault process are determined.

[0066] Please see Figure 3 , is the GPR backflashover circuit when the system neutral point is grounded via the arc suppression coil, U g For ground potential rise, L is the arc suppression coil, R L To match the damping resistor, C L For line-to-ground electricity, C B The surge arrester's capacitance to ground and the transformer's 10kV input capacitance are combined. In the initial stage of the fault, the transient component of the surge arrester (GPR) is relatively large, causing oscillations in the circuit between the arc suppression coil and the line-to-ground capacitance. This results in a higher neutral point voltage amplitude, and the voltage across the surge arrester is higher than GPR + U. xge The voltage across the surge arrester is higher than its reference voltage, resulting in a larger discharge current during the initial breakdown. As the transient component of the GPR decays, the voltage across the arrester decreases, but due to the inductance L of the arc suppression coil and the line-to-ground capacitance C... L The ratio is constant, therefore GPR in L, C L Since the voltage division ratio in the circuit is constant, the voltage drop across the surge arrester is small and still higher than the reference voltage. During the fault, the surge arrester continues to discharge.

[0067] The capacitive current of a single-phase ground fault in a power system is related to the line-to-ground capacitance. The capacitive current is calculated for different ground capacitances as follows:

[0068]

[0069] Among them, I c For single-phase grounding capacitor current, A; U eω is the rated line voltage of the power system, kV; ω is the angular frequency; C is the capacitance to ground per phase of the system line, μF.

[0070] For existing power plants, the line-to-ground capacitance C can be calculated based on the length of the surge arrester's working line and the basic parameters of the line. L .

[0071] For the capacitance to ground of the power line of the power station under construction, C L It is uncertain. When the capacitive current of a single-phase grounding fault in a 10kV power supply system is greater than 10A but less than 100A to 150A, the neutral point should be grounded through an arc suppression coil.

[0072] According to the "Design Code for Overvoltage Protection and Insulation Coordination of AC Electrical Installations," when the single-phase ground fault capacitive current of a plant / station power system is greater than 10A but less than 100A to 150A, a neutral point grounding method via an arc suppression coil should be adopted. This imposes certain limitations on the line-to-ground capacitance. The capacitance C is set based on the single-phase ground fault capacitive current. L The range is 1.5–30 μF, and the step size can be adjusted according to requirements.

[0073] As the detuning degree increases, the oscillation amplitude of the arc suppression coil-line-to-ground capacitance circuit under the action of GPR will decrease, and the rise amplitude of the high-voltage bus will also decrease. Consequently, the voltage that the surge arrester withstands during the GPR backflash will decrease, the energy absorbed by the surge arrester during the fault will decrease, and the surge arrester's GPR withstand safety limit will increase.

[0074] As the damping ratio increases, the resistance of the damping resistor associated with the arc suppression coil will increase, resulting in a decrease in the component of the GPR acting on the surge arrester. Consequently, the surge arrester absorbs less energy during a fault, and the surge arrester's GPR tolerance safety limit will increase.

[0075] The single-phase-to-ground capacitance corresponding to a 150A single-phase ground fault capacitance current is 27.567μF. To prevent system oscillation and instability caused by neutral point unbalanced voltage, overcompensation and series damping resistors are usually used as protective measures when the system neutral point is grounded through an arc suppression coil.

[0076] The degree to which the inductance value of the arc suppression coil deviates from the tuning is represented by the detuning degree v, as follows:

[0077] v = (X L -X C ) / X L

[0078] Among them, X L X represents the inductive reactance of the arc suppression coil. C This represents the system's geopotential capacitance value.

[0079] The line-to-ground capacitance C can be used as a reference. LThe system detuning is set to the arc suppression coil inductance value L.

[0080] The damping ratio of a power grid consists of three parts: the line-to-ground leakage conductance, the conductance of the arc suppression coil itself, and the equivalent conductance of the damping resistor.

[0081] ρ=ρ0+ρ L +ρ R

[0082] Where ρ is the grid damping ratio; ρ0 is the line-to-ground leakage conductance damping ratio; ρ L ρ is the damping ratio of the arc suppression coil winding conductivity; R The damping ratio of the damping resistor is taken as ρ0, which is the minimum value of 2%. L ρ is negligible. R Take R / ωL.

[0083] The configuration of damping resistors should first be based on the tuning measurement method, taking into account the asymmetry of the power grid, the line damping ratio ρ0, and the detuning degree. According to regulations, the neutral point displacement voltage U0 during normal operation should not exceed 15% of the phase voltage U. Therefore, the formula for limiting the power grid damping ratio is as follows:

[0084]

[0085] Among them, K C The asymmetry is typically a maximum of 2.5%; v is the detuning degree, taken as -10%, resulting in ρ≥13.3%. Taking ρ0 as a minimum of 2%, then ρ R ≥11.3%, i.e., damping resistance R L ≥11.3%X L .

[0086] When the system neutral point is grounded via an arc suppression coil, the configuration of the arc suppression coil should follow the above-mentioned standards. For specific operating conditions, it should have a certain degree of detuning and damping rate. L and R can be set according to the above calculation method. L The values ​​are used for calculation.

[0087] The capacitance to ground of the working line of a typical substation service surge arrester is C. L Furthermore, the principle for configuring the arc suppression coil is that the detuning degree is v%, and the damping resistance damping rate is ρ. In this case, the inductance L of the arc suppression coil is X. L =X C / (1-v), that is, L=1 / (3ω) 2 C L (1-v), damping resistor R L =ρωL.

[0088] S3. Based on the simulation model of the power supply system of the plant / station obtained in step S1 and the parameters of the simulation model of the power supply system of the plant / station obtained in step S2, determine the discharge current waveform and the voltage waveform at both ends of the surge arrester in the fault process of 0.5s, and perform integral calculation along time to obtain the energy absorbed by the surge arrester under GPR backflash.

[0089] The energy W absorbed by the surge arrester under GPR backflash is specifically:

[0090]

[0091] Where P(t) is the discharge power of the surge arrester, W; u(t) and i(t) are the voltage and discharge current across the surge arrester, respectively; t0 is the fault duration, which is generally taken as 0.5s.

[0092] For surge arresters of different models and capacities, their current-carrying capacity can be calculated. According to GB / T 11032-2020 "AC Gapless Metal Oxide Surge Arresters", a surge arrester should be able to withstand 18 impulses of 2ms square wave current. The amplitude of the square wave current that surge arresters of different voltage levels should withstand can be found in "AC Gapless Metal Oxide Surge Arresters". Based on the surge arrester's volt-ampere characteristics, the energy absorbed by the surge arrester under a single 2ms square wave current impulse can be calculated and used as the surge arrester's current-carrying capacity. By comparing the energy absorbed W during a surge arrester failure with its rated current-carrying capacity, if the energy absorbed W is less than the current-carrying capacity, the surge arrester is considered to have no risk of thermal breakdown; if the energy absorbed W is greater than the current-carrying capacity, the surge arrester has a risk of thermal breakdown.

[0093] S4. For the surge arresters of the existing power station, compare the energy absorbed by the surge arrester under GPR backflash obtained in step S3 with the set current carrying capacity of the surge arrester. When the energy absorbed by the surge arrester is greater than the set current carrying capacity of the surge arrester, the safety of the surge arrester under GPR backflash is verified.

[0094] Based on the backflashover characteristics of the GPR backflashover arrester obtained in step S4, the safety of the arrester under GPR backflashover is verified in the following two cases:

[0095] For existing power plant surge arresters, the capacitance C of the surge arrester's operating line to ground is... L The numerical values ​​are substituted into the simulation model obtained in step S1 for calculation. Based on the energy absorbed by the surge arrester obtained in step S3, it is compared with the current carrying capacity of the surge arrester. When the energy absorbed by the surge arrester W is less than its current carrying capacity, it is considered that the surge arrester is not at risk of thermal collapse; when the energy absorbed by the surge arrester W is greater than its current carrying capacity, the surge arrester is at risk of thermal collapse. This is used to verify the safety of the surge arrester under GPR backflash.

[0096] For surge arresters in power plants under construction, utilizing the backflashover characteristics of GPR surge arresters when the neutral point of the power system is grounded via an arc suppression coil as determined in step S4, different line-to-ground capacitances C are used. L The energy absorbed by the surge arrester under GPR backflash is calculated using a step-size interval, and compared with the set current-carrying capacity of the surge arrester to obtain the surge arrester's GPR safety limit under neutral point resonant grounding as a function of the line-to-ground capacitance C. L The changes.

[0097] If it is necessary to calculate the surge arrester's withstand GPR safety limit under different operating conditions, the line-to-ground capacitance C in the simulation model in steps S1 and S2 can be changed. L The parameters are calculated separately, and the magnitude of the energy absorbed by the surge arrester and the current carrying capacity calculated in step S3 are compared to verify the safety of the surge arrester under GPR backflash.

[0098] In another embodiment of the present invention, a system for calculating the GPR safety limit of a surge arrester under neutral point resonant grounding is provided. This system can be used to implement the above-mentioned method for calculating the GPR safety limit of a surge arrester under neutral point resonant grounding. Specifically, the system for calculating the GPR safety limit of a surge arrester under neutral point resonant grounding includes a simulation module, a parameter module, a recording module, a characteristic module, and a calculation module.

[0099] Among them, the parameter module verifies the safety of the power system simulation model of the plant / station power supply system obtained by inputting the arc suppression coil configuration scheme and line-to-ground capacitance into the simulation module for the surge arrester of the existing power plant; for the surge arrester of the power plant under construction, the parameters of the power system simulation model of the plant / station power supply system are set according to the quantitative relationship between the arc suppression coil and the line-to-ground capacitance, and the surge arrester's backflash characteristics under different arc suppression coil configuration methods are determined.

[0100] The recording module, based on the simulation model of the power supply system of the plant / station obtained by the simulation module and the parameters of the simulation model of the power supply system of the plant / station obtained by the parameter module, determines the discharge current waveform and the voltage waveform at both ends of the surge arrester in the 0.5s fault process, and performs integral calculation along time to obtain the energy absorbed by the surge arrester under GPR backflash.

[0101] The characteristic module, based on the backflash characteristics of the surge arrester under different arc suppression coil configurations obtained from the parameter module, determines the backflash characteristics of the GPR surge arrester when the neutral point of the power system of the plant / station is grounded through the arc suppression coil by the voltage change waveform across the surge arrester during the fault process;

[0102] The calculation module, for existing power plant surge arresters, compares the energy absorbed by the arrester under GPR backflash as obtained by the recording module with the arrester's set current capacity to verify the arrester's safety under GPR backflash. For surge arresters in power plants under construction, it utilizes the backflash characteristics of the GPR backflash arrester when the neutral point of the power system is grounded through an arc suppression coil, as determined by the characteristic module, and applies different line-to-ground capacitances C. L The energy absorbed by the surge arrester under GPR backflash is calculated using a step-size interval, and compared with the set current-carrying capacity of the surge arrester to obtain the surge arrester's GPR safety limit under neutral point resonant grounding as a function of the line-to-ground capacitance C. L The changes.

[0103] In another embodiment of the present invention, a terminal device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to achieve a corresponding method flow or corresponding function. The processor described in this embodiment can be used for the operation of the method for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding, including:

[0104] A simulation model of the power supply system of a substation is built based on the principle of GPR (Grounding Potential Rise) surge arresters. GPR refers to the rise in ground potential of the grounding grid. For existing substation surge arresters, the arc suppression coil configuration scheme and line-to-ground capacitance are input into the simulation model for safety verification. Based on the simulation model and its parameters, the discharge current waveform and voltage waveform of the surge arrester during a 0.5s fault process are determined, and integral calculations are performed over time to obtain the energy absorbed by the surge arrester under GPR surge. For existing substation surge arresters, the energy absorbed under GPR surge is compared with the arrester's set current carrying capacity. When the absorbed energy exceeds the arrester's set current carrying capacity, the arrester faces a safety risk. The safety of the surge arrester under GPR surge is thus verified.

[0105] In another embodiment of the present invention, a storage medium is also provided, specifically a computer-readable storage medium (memory). This computer-readable storage medium is a memory device in a terminal device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and extended storage media supported by the terminal device. The computer-readable storage medium provides storage space that stores the terminal's operating system. Furthermore, this storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM or non-volatile memory, such as at least one disk storage device.

[0106] One or more instructions stored in a computer-readable storage medium can be loaded and executed by a processor to implement the corresponding steps of the method for calculating the GPR safety limit of a surge arrester during neutral point resonant grounding in the above embodiments; one or more instructions in the computer-readable storage medium are loaded and executed by the processor to perform the following steps:

[0107] A simulation model of the power supply system of a substation is built based on the principle of GPR (Grounding Potential Rise) surge arresters. GPR refers to the rise in ground potential of the grounding grid. For existing substation surge arresters, the arc suppression coil configuration scheme and line-to-ground capacitance are input into the simulation model for safety verification. Based on the simulation model and its parameters, the discharge current waveform and voltage waveform of the surge arrester during a 0.5s fault process are determined, and integral calculations are performed over time to obtain the energy absorbed by the surge arrester under GPR surge. For existing substation surge arresters, the energy absorbed under GPR surge is compared with the arrester's set current carrying capacity. When the absorbed energy exceeds the arrester's set current carrying capacity, the arrester faces a safety risk. The safety of the surge arrester under GPR surge is thus verified.

[0108] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0109] Please see Figure 1 and Figure 2 This invention establishes a simulation model of a GPR (Gas-Regulated Reverse) surge arrester for the operating condition where the neutral point of the system is connected to an arc-suppression coil, proposes corresponding calculation methods, and analyzes the influence mechanism of the arc-suppression coil on the GPR surge arrester, such as... Figure 3 As shown in the figure. This embodiment illustrates the implementation method of the present invention through two examples.

[0110] Example 1

[0111] The safety of the station surge arrester against GPR backflash is verified under the given operating conditions of detuning degree, damping rate, line-to-ground capacitance, and surge arrester model.

[0112] First step, take C L The inductance L of the arc suppression coil is 300mH, with a detuning degree v of 10μF and a detuning degree v of -10%. The inductance ρ is taken as... R =12%, then R L =12%X L That is, damping resistance R L Take 11.58Ω.

[0113] The second step is to substitute the above parameters into... Figure 2 In the simulation model diagram shown, the fault duration is set to 0.5s, the GPR transient component decay time is set to 0.2s, and the GPR phase is made opposite to the A-phase bus voltage.

[0114] Furthermore, calculations show that the discharge current of phase A surge arrester is the largest, such as... Figure 4 As shown, the discharge current of phase A surge arrester reached as high as 220A during the first breakdown, and then dropped to about 7A. This is because in the early stage of the fault, the transient component of GPR is large, which generates a large oscillating voltage at the neutral point, thereby raising the bus voltage and resulting in a large discharge current when the surge arrester breaks down for the first time.

[0115] Furthermore, as the transient component of GPR decays, the peak value of the oscillating voltage at the neutral point decreases, and the voltage across the surge arrester decreases, but the change is only 0.7kV. Figure 5 As shown in the figure. Because the voltage across the surge arrester is close to the reference voltage and the change amplitude is small, the subsequent discharge current amplitude is low, and the neutral point voltage change curve is as follows. Figure 6 As shown.

[0116] The third step is to combine Figure 4 and Figure 5 Multiplying the surge arrester voltage and current and integrating over a time interval of 0.5s, the steady-state effective value of GPR is taken as 10kV when the neutral point is grounded through the arc suppression coil. L Taking 10μF, the energy absorbed by the A-phase surge arrester during the fault process can be obtained from the calculation result of the convolution integral as 10480.67J.

[0117] According to GB / T 11032-2020 "AC Gapless Metal Oxide Surge Arresters", surge arresters should be able to withstand 18 impulses of 2ms square wave current. For 10kV power station surge arresters, it is specified that they should undergo a test of 18 square wave current impulses (square wave current capacity of 2ms, 150A). Based on the volt-ampere characteristics, when the discharge current is 150A, the voltage across the surge arrester is 30.5kV~31kV. Considering a certain safety margin, the current carrying capacity of a 10kV surge arrester is considered to be W=30000×150×2×10 -3 =9000J.

[0118] Therefore, the energy absorbed by the A-phase surge arrester exceeds its current carrying capacity, posing a risk of thermal collapse.

[0119] Example 2

[0120] For a given detuning degree and damping rate, calculate the line-to-ground capacitance C for different operating conditions. L The GPR safety limit for the surge arrester.

[0121] The first step, according to the "Design Code for Overvoltage Protection and Insulation Coordination of AC Electrical Installations", is that when the line capacitance is 1.5μF to 30μF, a system neutral point resonant grounding can be used. In this embodiment, C is taken as... L The available values ​​are 1.5μF, 3μF, 6μF, 9μF, 12μF, 15μF, 20μF, 25μF, and 30μF. The detuning degree v is set to -10%, meaning the inductance L of the arc suppression coil ranges from 100 to 2050 mH; ρ0 is set to a minimum of 2%, and ρ... R =12%, then R L =12%X L That is, damping resistance R L The value ranges from 3.77 to 77.28 Ω.

[0122] The second step is to substitute the above values ​​into the following... Figure 2 The model shown, and using the surge arrester energy absorption calculation method in Example 1, can yield the line-to-ground capacitance C for different lines. L The surge arrester absorbs energy under different GPR backflash conditions, and the GPR value is gradually refined using a bisection method until the energy absorbed by the surge arrester under a certain GPR backflash condition is equal to the current carrying capacity. At this point, the GPR is the safety limit of the surge arrester under that operating condition. The calculation results of the surge arrester's GPR safety limit under different operating conditions are as follows: Figure 7 As shown.

[0123] Furthermore, the analysis of the surge arrester's withstand GPR safety limit with C was performed. L Reasons for the variation pattern. When the neutral point is grounded through an arc suppression coil, the change in the surge arrester's GPR safety limit is extremely small. Figure 7 It can be seen that the safety limit of the surge arrester GPR only varies significantly when the line-to-ground capacitance is small. This is because when the line-to-ground capacitance C... L When C is small, its charging time constant is small; as C increases... L The increase in C leads to an increase in the charging time constant, resulting in the surge arrester absorbing more energy. L After increasing to a certain size, C often L Before the charging process is complete, the surge arrester reaches its critical current energy value.

[0124] Furthermore, when the system neutral point is grounded via the arc suppression coil, the GPR backflashover circuit is as follows: Figure 3 As shown, in the initial stage of the fault, the GPR transient component is relatively large, causing oscillations in the circuit between the arc suppression coil and the line-to-ground capacitance, resulting in a high neutral point voltage amplitude and a voltage across the surge arrester higher than its reference voltage. Therefore, the discharge current during the initial breakdown is large. As the GPR transient component decays, the voltage across the surge arrester decreases, but due to the inductance L of the arc suppression coil and the line-to-ground capacitance C... L The ratio is constant, therefore GPR in L, C L The voltage division ratio in the circuit is also constant, so the voltage drop across the surge arrester is relatively small and still higher than the reference voltage. During the fault, the surge arrester continues to discharge, resulting in its absorbed energy being much higher than that of a neutral-point ungrounded system. From the definitions of detuning degree and damping rate, it can be seen that the inductance L of the arc suppression coil is related to the line-to-ground capacitance C. L Related, the two are inversely proportional, and this embodiment applies to all C. L All calculations were performed with a detuning degree of -10%. Figure 3 It can be seen that regardless of C L Increase or decrease, GPR at L and C L The voltage division ratio in the circuit is constant, and the bus voltage and GPR change in the same direction, meaning their phase and amplitude changes are consistent. Therefore, the surge arrester at C... LThe voltage it withstands remains essentially constant under different conditions, meaning the surge arrester's GPR safety limit varies with different C values. L Under certain conditions, the variation is extremely small.

[0125] This invention also provides protection against backflashover for surge arresters. When the neutral point is grounded through an arc-suppression coil, the ratio of the inductance in the arc-suppression coil to the line-to-ground capacitance is determined by the detuning rate. Since the detuning rate varies relatively little, the GPR safety limit of the surge arrester remains essentially unchanged when the damping resistance is constant. When the damping resistance increases, its damping coefficient and voltage division ratio increase, effectively reducing the voltage across the surge arrester and improving the GPR safety limit. Therefore, it is crucial to rationally select the damping resistance to limit the inductance L and line-to-ground capacitance C when the neutral point is grounded through an arc-suppression coil. L The circuit oscillation effect is very important. Theoretically, the larger the damping resistance, the better its damping effect on the circuit oscillation. However, a large damping resistance will cause heat generation and economic losses. Therefore, it is necessary to weigh the advantages and disadvantages of both when making a choice.

[0126] In summary, this invention provides a method and system for calculating the GPR safety limit of a surge arrester under neutral point resonant grounding. It simplifies the simulation model, focuses on key factors in the GPR backflash arrester process, and meticulously models these key factors within the simulation model. Combining the surge arrester's volt-ampere characteristics and current capacity, it proposes a verification method for surge arrester energy calculation. It highlights the mechanistic characteristics of the GPR backflash arrester when the system neutral point is grounded via an arc suppression coil, accurately calculates the safety limit of the surge arrester's GPR withstand capability under different operating conditions when the system neutral point is grounded via an arc suppression coil, and proposes the influence of detuning degree and damping rate on the GPR backflash arrester. During the design phase, this invention can be used to design surge arrester configuration schemes; during the verification phase, it can be used to verify the safety of surge arresters, optimize surge arrester configuration schemes, and effectively avoid potential safety accidents and economic losses that may occur when using existing research results.

[0127] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0128] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0129] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0130] In the embodiments provided by this invention, it should be understood that the disclosed devices / terminals and methods can be implemented in other ways. For example, the device / terminal embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0131] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0132] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0133] If the integrated module / unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium can be appropriately added or removed according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media do not include electrical carrier signals and telecommunication signals.

[0134] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, 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, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0135] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0136] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0137] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for calculating the safety limit of the surge arrester's GPR (Ground Pressure Ratio) during neutral point resonant grounding, characterized in that, Includes the following steps: S1. Based on the principle of GPR (Grounding Potential Rise) surge arrester used in substations, a simulation model of the power supply system of the plant / station is built. GPR refers to the ground potential rise of the grounding grid. The specific simulation model of the power supply system of the plant / station is as follows: This includes a high-voltage busbar, with one end grounded and the other end branching into four paths. Paths one, two, and three are connected to one end of the corresponding plant / station power supply system busbar. The other end of the corresponding plant / station power supply system busbar branches into two paths: one path is grounded via its corresponding grounding capacitor, and the other path is connected via a parallel nonlinear resistor, a surge arrester grounding capacitor, and the transformer 10kV side inlet capacitor C. B After being raised to ground potential, the fourth path passes through the arc suppression coil inductor L and the matching damping resistor R in sequence. L After the ground potential is raised, it is grounded, and a switch is connected in parallel across the two ends of the ground potential rise. S2. For the surge arresters of existing power plants, the arc suppression coil configuration scheme and the line-to-ground capacitance are input into the power system simulation model of the plant / station obtained in step S1 for safety verification. The arc suppression coil meets the following conditions: in, For grid damping ratio, For asymmetry, Detuning degree; S3. Based on the simulation model of the power supply system of the plant / station obtained in step S1 and the parameters of the simulation model of the power supply system of the plant / station obtained in step S2, determine the discharge current waveform and the voltage waveform across the surge arrester during the 0.5s fault process, and perform integration calculations over time to obtain the energy absorbed by the surge arrester under GPR backflash. Specifically: in, The discharge power of the surge arrester. and These are the voltage across the surge arrester and the discharge current, respectively. Duration of the fault; S4. For the surge arresters of the existing power station, compare the energy absorbed by the surge arrester under GPR backflash obtained in step S3 with the set current carrying capacity of the surge arrester. When the energy absorbed by the surge arrester is greater than the set current carrying capacity of the surge arrester, the surge arrester has a safety risk. The safety of the surge arrester under GPR backflash is verified.

2. The method for calculating the safety limit of the surge arrester GPR during neutral point resonant grounding according to claim 1, characterized in that, In step S2, the surge arrester's backflashback characteristics under different arc suppression coil configurations are as follows: When the capacitive current of a single-phase ground fault in the power system of a plant / station is greater than 10A but less than 100A~150A, a neutral point grounding method via an arc suppression coil is adopted, and the line-to-ground capacitance C... L The range is 1.5~30μF.

3. The method for calculating the safety limit of the surge arrester GPR during neutral point resonant grounding according to claim 1, characterized in that, In step S2, for the surge arresters of the power plant under construction, the parameters of the power system simulation model of the plant / station are set according to the quantitative relationship between the arc suppression coil and the line-to-ground capacitance, and the surge arrester backflash characteristics under different arc suppression coil configurations are determined. Based on the backflashover characteristics of surge arresters under different arc suppression coil configurations, the backflashover characteristics of the GPR surge arrester when the neutral point of the power supply system is grounded through the arc suppression coil are determined by observing the voltage change waveform across the surge arrester during a fault. Utilizing these backflashover characteristics, different line-to-ground capacitances C are applied. L The energy absorbed by the surge arrester under GPR backflash is calculated using a step-size interval, and compared with the set current-carrying capacity of the surge arrester to obtain the surge arrester's GPR safety limit under neutral point resonant grounding as a function of the line-to-ground capacitance C. L The changes.

4. According to the method for calculating the safety limit of the surge arrester GPR during neutral point resonant grounding as described in claim 3, the backflashover characteristic of the GPR backflashover arrester is specifically as follows: Oscillations occur in the circuit between the arc suppression coil and the line-to-ground capacitance. The voltage across the surge arrester due to the backflashover from the GPR is higher than the sum of the GPR and the bus voltage. At this point, the voltage across the surge arrester is higher than the reference voltage, causing the surge arrester to break down and discharge. Based on the detuning degree... and grid damping rate Bus voltage U xge The phase and amplitude changes are consistent with those of the GPR backflash arrester. The voltage across the GPR backflash arrester does not decrease with the decay of the GPR, and the arrester repeatedly breaks down during the fault process.

5. A system for calculating the GPR safety limit of a surge arrester under neutral point resonant grounding, characterized in that, include: The simulation module builds a simulation model of the power supply system of the plant / station based on the principle of GPR (Grounding Regulator) surge arrester in the substation. GPR refers to the rise in ground potential of the grounding grid. The specific simulation model of the power supply system of the plant / station is as follows: This includes a high-voltage busbar, with one end grounded and the other end branching into four paths. Paths one, two, and three are connected to one end of the corresponding plant / station power supply system busbar. The other end of the corresponding plant / station power supply system busbar branches into two paths: one path is grounded via its corresponding grounding capacitor, and the other path is connected via a parallel nonlinear resistor, a surge arrester grounding capacitor, and the transformer 10kV side inlet capacitor C. B After being raised to ground potential, the fourth path passes through the arc suppression coil inductor L and the matching damping resistor R in sequence. L After the ground potential is raised, it is grounded, and a switch is connected in parallel across the two ends of the ground potential rise. The parameter module performs safety verification on the existing power plant surge arresters by inputting the arc suppression coil configuration scheme and line-to-ground capacitance into the simulation model of the power system obtained from the simulation module. The arc suppression coil must meet the following conditions: in, For grid damping ratio, For asymmetry, Detuning degree; The recording module, based on the power system simulation model of the plant / station obtained from the simulation module and the parameters of the power system simulation model obtained from the parameter module, determines the discharge current waveform and the voltage waveform across the surge arrester during the 0.5s fault process. It then performs integration calculations over time to obtain the energy absorbed by the surge arrester under GPR backflash. Specifically: in, The discharge power of the surge arrester. and These are the voltage across the surge arrester and the discharge current, respectively. Duration of the fault; The calculation module compares the energy absorbed by the surge arrester under GPR backflash, obtained from the recording module, with the set current capacity of the surge arrester. When the energy absorbed by the surge arrester is greater than the set current capacity, the surge arrester has a safety risk. The safety of the surge arrester under GPR backflash is verified.

6. A computer-readable storage medium for storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform the method of any one of claims 1 to 4.

7. A computing device, characterized in that, include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the one or more programs including steps for performing the method of any one of claims 1 to 4.

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