A parameter calculation and test method for resonance withstand voltage of high voltage and large capacity equipment

Abstract

The present invention discloses a parameter calculation and test method for resonant withstand voltage of high-voltage and large-capacity equipment, comprising the following steps: 1) obtaining the equipment parameter C to be tested, determining the target test voltage value and the expected AC frequency range; 2) generating an optional solution set for the total number of available test reactors; 3) calculating the resonant frequency and quality factor for each test arrangement scenario in the solution set; 4) eliminating the situation where the resonant frequency value in the calculated scenario does not meet the requirements according to the test frequency condition limit; 5) calculating the current flowing through each reactor; 6) selecting the best test scheme in the configuration of the current solution set. The present invention can be used to guide the on-site AC withstand voltage parameter calculation and test configuration of high-voltage and large-capacity equipment, thereby ensuring the safe and stable operation of the power system equipment level.

Description

Technical Field

[0001] The invention belongs to the technical field of on-site test of resonance withstand voltage of electrical equipment, and in particular relates to a parameter calculation and test method for resonance withstand voltage of high-voltage and large-capacity equipment. Background Art

[0002] Based on the existing common series resonance principle, the best quality factor Q of the system is obtained under frequency modulation, and a voltage Q times the high-voltage side voltage of the excitation transformer occurs on the test product. However, it should be noted that when the circuit is not in the resonant state or the preferred resonant frequency is difficult to modulate, the inductive reactive power and capacitive reactive power in the system are not zero after synthesis. This part of the power needs to flow through the excitation transformer, reactor, and variable frequency power supply, which increases the demand for the capacity of these devices. Considering the characteristics of parallel resonance, a series-parallel hybrid resonance has also been used in the resonant withstand voltage test of large-capacity equipment in recent years. The parallel branch in the hybrid circuit is used to reduce the current of the entire circuit. However, due to the influence of the parallel branch, the calculation of the resonance point and quality factor of the original system also changes. For the calculation of the resonant frequency and quality factor of the hybrid resonance circuit, if the deviation of the resistance to the quality factor is not considered, it will be very obvious, and the error will affect the configuration results of the reactors in each branch. The main working modes of the current frequency-modulated test power supply are sinusoidal output and square wave pulse output, but there is no discussion on the impact on the test characteristic parameters.

[0003] The on-site AC test of high-voltage and large-capacity equipment is a "costly" test. It requires scientific and correct theoretical guidance to reduce the transportation and on-site assembly and placement costs of high-voltage test equipment. This patent summarizes and derives key characteristic parameters from the perspective of engineering application of resonant withstand voltage test (including conventional series resonance and hybrid resonance), and uses laboratory-level dynamic simulation experiments, on-site large-capacity submarine cable field cases and PSCAD simulation to empirically analyze the calculation of resonance parameters. Summary of the invention

[0004] In order to overcome the above technical problems, the present invention proposes a parameter calculation and test method for resonant withstand voltage of high-voltage and large-capacity equipment. The method can pre-calculate the key test parameters resonant frequency and quality factor before the test, so as to guide the test layout and plan formulation, and judge whether the test frequency meets the requirements of the regulations. The pre-calculation of the quality factor is used to assist in judging whether the test source capacity can meet the needs, determine the test plan with the optimal configuration, and guide the test site.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A parameter calculation and test method for resonance withstand voltage of high-voltage and large-capacity equipment, comprising the following steps;

[0007] 1) Obtain the equipment parameter C to be tested, determine the target test voltage value and the expected AC frequency range (for example, the frequency range of the cable AC withstand voltage is 30Hz to 300Hz);

[0008] 2) Generate an optional solution set M = {[n1, n2] | n1 + n2 ≤ N and n2 > 0} from the total number N of available test reactors, where n1 is the number of reactors in parallel in the parallel branches of the hybrid resonance; n2 is the number of reactors in parallel in the series branches of the pure series resonance or hybrid resonance;

[0009] 3) Calculate the resonant frequency and quality factor for each test arrangement scenario in the solution set M;

[0010] 4) Eliminate the calculated scenarios where the resonant frequency values ​​do not meet the requirements according to the test frequency condition restrictions;

[0011] 5) Calculate the current flowing through each reactor based on the values ​​of n1, n2 and the target test voltage. If the current exceeds the rated current value of a single reactor, the scenario is eliminated. It is also determined whether the capacity of the test excitation transformer and the power supply capacity meet the restrictions. The calculated quality factor Q value and the maximum voltage of the excitation transformer are used to determine whether the target withstand voltage value can be met. Scenarios that do not meet the conditions are eliminated.

[0012] 6) In the configuration of the current solution set, the best test solution is selected according to the condition that "the minimum number of reactors" is better than "the maximum Q value".

[0013] The test equipment parameters in step 1) include the test sample capacitance parameter C; the test reactor inductance L, resistance R and the total number of available test reactors N; the equivalent resistance R of the excitation transformer high voltage winding t , equivalent leakage inductance L of the excitation transformer high voltage winding t and field transformer rated voltage.

[0014] The M in step 2) is implemented by the following code:

[0015]

[0016] Where N is the total number of available test reactors, and M is a two-dimensional array, the first column of which represents n1 in the model, and the second column represents n2 in the model.

[0017] The specific operation of step 3) is: calculating the resonant frequency and quality factor of each test arrangement scenario in the solution set M;

[0018] (1) When n1 = 0, the resonant frequency calculation formula under pure series resonance is:

[0019]

[0020] If L t Substituting =0 into formula (1), we can get the approximate calculation formula:

[0021]

[0022] (2) When n1>0, the resonant frequency calculation formula under hybrid resonance is:

[0023] in,

[0024]

[0025]

[0026] We can get There are two cases for the sign of The sign of is positive, and the resonance is the global resonance point, that is, the hybrid system is the series resonance point after undercompensation of the n2 branch; when The sign of is negative, and the resonance is a local resonance point, that is, the hybrid system is a parallel resonance point obtained after the n2 branch and the test specimen branch are fully resonant. The sign of is positive to meet the AC withstand voltage requirement;

[0027] If R=0,r=0,L t =0 is substituted into equations (3)-(5) to obtain:

[0028]

[0029] It is obtained that the simplified calculated resonant frequency f′ has a similar calculation structure to that of formula (2), and both are that when the number of test reactors used is determined, the resonant frequency is also determined;

[0030] (3) An equation for quality factor suitable for field calculation is:

[0031]

[0032] This formula is applicable to the test case of series equivalent and needs to be calculated at the resonant frequency point. The Q value is related to the parameters R, L, C, R t , L t In addition, it should be pointed out that inadequate test measures may occur on site, such as poor grounding, severe corona, etc., which will also affect the Q value.

[0033] The elimination operation in step 4) is that if the acceptable range of the test frequency band is between 20 and 300 Hz, the resonant frequency of each combination of reactors in the solution set M is calculated, and if the frequency band range is not satisfied, this combination is deleted from the solution set M.

[0034] The specific operation of step 5) is as follows:

[0035] The current flowing through a single reactor in the n1 branch is calculated according to the following formula:

[0036]

[0037] The current flowing through a single reactor in the n2 branch is calculated according to the following formula:

[0038]

[0039] The total current of the n2 branch can be used to determine whether the capacity of the excitation transformer and the power supply capacity meet the restrictions. The product of the rated voltage on the high-voltage side of the excitation transformer and the Q value is compared with the target withstand voltage value to screen the lowest Q value range limit.

[0040] Beneficial effects of the present invention:

[0041] The present invention performs parameter calculation on pure series resonance and series-parallel resonance, and the calculation of resonance frequency and quality factor before the test can be used to guide the test configuration on site. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a general wiring diagram of the resonant withstand voltage in the present invention.

[0043] Figure 2 It is a simulation model diagram of the resonant withstand voltage in the present invention. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with embodiments.

[0045] like Figure 1 Figure 2 As shown: The parameter calculation and test method for resonant withstand voltage of high-voltage and large-capacity equipment described in the present invention includes the following steps:

[0046] 1) Obtain the capacitance parameter C of the test product to be tested; the inductance L, resistance R of the test reactor and the total number N of available test reactors; the equivalent resistance R of the excitation transformer high voltage winding t , the equivalent leakage inductance L of the excitation transformer high voltage winding t and excitation transformer rated voltage; and determination of the target test voltage value and the expected AC frequency range.

[0047] 2) According to Figure 1The test model shown generates an optional solution set M = {[n1,n2]|n1+n2≤N and n2>0} from the total number of available test reactors, where n1 is the number of reactors in parallel in the parallel branch of the hybrid resonance; n2 is the number of reactors in parallel in the series branch of the pure series resonance or hybrid resonance. M is implemented by the following code:

[0048]

[0049] Where N is the total number of available test reactors, and M is a two-dimensional array, the first column of which represents n1 in the model, and the second column represents n2 in the model.

[0050] 3) Calculate the resonant frequency and quality factor for each test arrangement scenario in the solution set M.

[0051] (1) When n1 = 0, the resonant frequency calculation formula under pure series resonance is:

[0052]

[0053] If L t Substituting =0 into formula (1), we can get the approximate calculation formula:

[0054]

[0055] (2) When n1>0, the resonant frequency calculation formula under hybrid resonance is:

[0056]

[0057] in,

[0058]

[0059] It can be found that the theoretical calculation formula of the resonant frequency is very complicated. In formula (3) There are two cases for the sign of . The sign of is positive, and the resonance is the global resonance point, that is, the hybrid system is the series resonance point after undercompensation of the n2 branch; when The sign of is negative, and the resonance is a local resonance point, that is, the hybrid system is a parallel resonance point obtained after the n2 branch and the test specimen branch are fully resonant. The sign of the resistor must be positive to meet the AC withstand voltage requirement.

[0060] If R=0,r=0,L t =0 is substituted into equations (3)-(5) to obtain:

[0061]

[0062] It can be found that the simplified calculated resonant frequency f′ has a similar calculation structure to that of formula (2), and both are that when the number of test reactors used is determined, the resonant frequency is also determined.

[0063] (3) An equation for quality factor suitable for field calculation is:

[0064]

[0065] This formula is applicable to the test case of series equivalent and needs to be calculated at the resonant frequency point. The Q value is related to the parameters R, L, C, R t , L t In addition, it should be pointed out that inadequate test measures may occur on site, such as poor grounding, severe corona, etc., which will also affect the Q value.

[0066] 4) It is necessary to eliminate the scenarios where the resonant frequency values ​​do not meet the requirements according to the test frequency condition. That is, if the acceptable range of the test frequency band is between 20 and 300 Hz, the resonant frequency of each combination of reactors in the solution set M is calculated. If it does not meet the frequency band range, this combination is deleted from the solution set M.

[0067] 5) Calculate the current flowing through each reactor based on the values ​​of n1, n2 and the target test voltage. If the current exceeds the rated current value of a single reactor, the scenario is eliminated.

[0068] The current flowing through a single reactor in the n1 branch is calculated according to the following formula:

[0069]

[0070] The current flowing through a single reactor in the n2 branch is calculated according to the following formula:

[0071]

[0072] The total current of the n2 branch can be used to determine whether the capacity of the excitation transformer and the power supply capacity meet the restrictions. The product of the rated voltage on the high-voltage side of the excitation transformer and the Q value is compared with the target withstand voltage value to screen the lowest Q value range limit.

[0073] 6) In the configuration of the current solution set, the best test solution is selected according to the condition that "the minimum number of reactors" is better than "the maximum Q value".

[0074] Example 1

[0075] To ensure the correctness of the deduction, a test circuit based on a pure sinusoidal power supply is built in PSCAD. The parameters of other parts remain the same. Only the voltage amplitude of the power module is adjusted until the voltage at the test position meets the requirements. The simulation model is shown in Figure 2 shown.

[0076] 1) Variable frequency power supply:

[0077] Rated input voltage: 380V

[0078] Rated output voltage: 480V

[0079] Rated capacity: 50kW

[0080] 2) Test reactance:

[0081] Rated capacity: 66kVar

[0082] Rated voltage: 30kV

[0083] Rated inductance: 43H

[0084] Reactor DC resistance: 192Ω

[0085] 3) Test excitation transformer:

[0086] Rated capacity: 18kVA

[0087] Rated transformation ratio: 500V / 8kV

[0088] High voltage side DC resistance: 90Ω

[0089] No-load voltage: 0.71%

[0090] 4) Nominal test capacitance:

[0091] Rated voltage: 20kV

[0092] Rated capacitance: 0.15uF

[0093] According to the rated voltage design target withstand voltage value of the nominal test capacitor, the qualified frequency range is 20Hz~300Hz, and six reactors are combined to simulate various series and parallel resonance test scenarios. The simulation results and calculated values ​​are compared as shown in Table 1. The value of Us in the table comes from the power supply voltage value, and Ub represents the measured voltage on the high-voltage side of the excitation transformer.

[0094] Table 1 Review and simulation results of quality factor

[0095]

[0096] Example 2

[0097] This example shows the comparison of the results of the field test. The 110kV cross-linked polyethylene submarine cable was subjected to a withstand voltage test on site, and the test analysis was carried out through field tests. In the test, a total of 4 test reactors with a rated voltage of 300kV and an inductance of 19.1H were used. The combination was: 2 series for series branches, and 2 parallel for parallel branches. The equivalent capacitance of the submarine cable was 4.62uF. The test product was applied with a relatively low AC withstand voltage of 128kV. The acceptable frequency range of the test was 20-300Hz, and the frequency conversion power supply cabinet on site used a sine wave output.

[0098] In order to keep the test combination mode on site consistent with the test structure of this paper, the parameters of the two-section reactor are first converted to a single section, and the original combination is equivalent to 1 series and 4 parallel reactors of 38.2H. The numerical equivalence does not affect the test process discussed, and the results of the calculation and field data are shown in Table 2. Theoretical calculations and field data once again verify the correctness of the derivation of the key parameters of the resonant withstand voltage in this paper, and give the theoretically optimal combination scheme.

[0099] Table 2 Comparison between field test and theory

[0100]

[0101] 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. Any modification or equivalent replacement that does 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 parameter calculation and test method for resonant withstand voltage of high-voltage and large-capacity equipment, characterized in that: The steps include: 1) Obtain the parameters C of the device to be tested, determine the target test voltage value and the expected AC frequency range; 2) Generate an optional solution set M = {[n1, n2] | n1 + n2 ≤ N and n2 > 0} from the total number N of available test reactors, where n1 is the number of reactors in parallel in the parallel branches of the hybrid resonance; n2 is the number of reactors in parallel in the series branches of the pure series resonance or hybrid resonance; 3) Calculate the resonant frequency and quality factor for each test arrangement scenario in the solution set M; 4) Eliminate the calculated scenarios where the resonant frequency values ​​do not meet the requirements according to the test frequency condition restrictions; 5) Calculate the current flowing through each reactor based on the values ​​of n1, n2 and the target test voltage. If the current exceeds the rated current value of a single reactor, the scenario is eliminated. Also, determine whether the capacity of the test excitation transformer and the power supply capacity meet the restrictions. The calculated quality factor Q value and the maximum voltage of the excitation transformer are used to determine whether the target withstand voltage value can be met. Scenarios that do not meet the conditions are eliminated. 6) In the configuration of the current solution set, select the best test solution according to the condition that "the minimum number of reactors" is better than "the maximum Q value"; The M in step 2) is implemented by the following code: Where N is the total number of available test reactors, M is a two-dimensional array, the first column of which represents n1 in the model, and the second column represents n2 in the model; The specific operation of step 3) is: calculating the resonant frequency and quality factor of each test arrangement scenario in the solution set M; (1) When n1 = 0, the resonant frequency calculation formula under pure series resonance is: If L t Substituting =0 into formula (1), we can get the approximate calculation formula: (2) When n1>0, the resonant frequency calculation formula under hybrid resonance is: in, We can get There are two cases for the sign of The sign of is positive, and the resonance is the global resonance point, that is, the hybrid system is the series resonance point after undercompensation of the n2 branch; when The sign of is negative, and the resonance is a local resonance point, that is, the hybrid system is a parallel resonance point obtained after the n2 branch and the test specimen branch are fully resonant. The sign of is positive to meet the AC withstand voltage requirement; If R=0,r=0,L t =0 is substituted into equations (3)-(5) to obtain: It is obtained that the simplified calculated resonant frequency f′ has a similar calculation structure to that of formula (2), and both are that when the number of test reactors used is determined, the resonant frequency is also determined; (3) An equation for quality factor suitable for field calculation is: This formula is applicable to the test case of series equivalent and needs to be calculated at the resonant frequency point. The Q value is related to the parameters R, L, C, R t , L t Related; The test equipment parameters in step 1) include the test sample capacitance parameter C; the test reactor inductance L, resistance R and the total number of available test reactors N; the equivalent resistance R of the excitation transformer high voltage winding t , equivalent leakage inductance L of the excitation transformer high voltage winding t and field transformer rated voltage; The elimination operation in step 4) is that if the acceptable range of the test frequency band is between 20 and 300 Hz, the resonant frequency of each combination of reactors in the solution set M is calculated, and if the frequency band range is not met, this combination is deleted from the solution set M.

2. A parameter calculation and test method for resonance withstand voltage of high-voltage and large-capacity equipment according to claim 1, characterized in that: The specific operation of step 5) is as follows: The current flowing through a single reactor in the n1 branch is calculated according to the following formula: The current flowing through a single reactor in the n2 branch is calculated according to the following formula: The total current of the n2 branch can be used to determine whether the capacity of the excitation transformer and the power supply capacity meet the restrictions. The product of the rated voltage on the high-voltage side of the excitation transformer and the Q value is compared with the target withstand voltage value to screen the lowest Q value range limit.

Images