WO2024082371A1

WO2024082371A1 - Three-phase high-voltage shunt reactor capable of being used for cable withstand voltage test, and design method

Info

Publication number: WO2024082371A1
Application number: PCT/CN2022/133244
Authority: WO
Inventors: 吴昊; 韩彦华; 王荆; 郭璨; 任双赞; 杨鼎革; 牛博; 左坤; 李鹏程; 师一卿; 王辰曦
Original assignee: 国网陕西省电力有限公司电力科学研究院
Priority date: 2022-10-20
Filing date: 2022-11-21
Publication date: 2024-04-25
Also published as: CN115639448A

Abstract

A three-phase high-voltage shunt reactor capable of being used for cable withstand voltage test, and a design method. By redesigning existing shunt reactors, the shunt reactor can be used for the cable withstand voltage test on the basis of original design requirements, such that the test time, site and manpower can be reduced, that is, the shunt reactor can be used for the cable withstand voltage test while satisfying the reactive power compensation requirement of a cable line, and plays a role in series resonance.

Description

Three-phase high-voltage shunt reactor for cable withstand voltage test and design method

Technical Field

The invention relates to the field of cable withstand voltage test, and in particular to a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test and a design method thereof.

Background technique

Due to its good electrical performance, power cables are widely used in urban power grids, offshore wind power, cross-sea power transmission and other projects. With the rapid construction of power grids, high-voltage, large-capacity, and long-distance power cables are put into operation on a large scale, playing an important role in the reliability of electricity for production and life. Before the cable is officially put into operation and after maintenance, the insulation performance of the cable line must be assessed through a handover test to ensure the long-term and stable operation of the cable line.

The AC withstand voltage test of high-voltage cables mainly adopts the variable frequency series resonance withstand voltage test method. This method is to change the system frequency to make the test reactor and the test cable resonate, thereby generating high voltage on the test cable. The test frequency range is 20-300Hz. IEC standards, IEEE standards, and national standards all recommend the use of this test method. When conducting series resonance AC withstand voltage tests on high-voltage cables (such as 220kV, 330kV, and 500kV), in order to achieve the ideal resonance frequency, a large number of series resonance reactors need to be matched, which places high requirements on the test site and requires the cooperation of a large-tonnage crane. It is difficult and risky to build a test circuit, which is particularly evident in offshore wind power projects.

Since the capacitance between cable phases and the capacitance between cable and ground are relatively large, in order to reduce the "capacitance rise" phenomenon at the end, reduce line operation overvoltage, improve line reactive power distribution and reduce line loss, high-voltage shunt reactors are configured at the head and end when designing high-voltage or long-distance cables. However, the existing high-voltage shunt reactors cannot be used for cable withstand voltage tests.

Summary of the invention

The purpose of the present invention is to provide a three-phase high-voltage shunt reactor and a design method that can be used for a cable withstand voltage test, so as to solve the problems existing in the prior art. The present invention redesigns the existing shunt reactor, and can use the shunt reactor for the cable withstand voltage test on the basis of the original design requirements, thereby saving test time, site, and personnel. That is, while meeting the demand for reactive power compensation of the cable line, it can be used for the cable withstand voltage test, thereby playing the role of series resonance.

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

A design method for a three-phase high-voltage shunt reactor that can be used for a cable withstand voltage test includes the following steps:

S1: Estimate the cable length and ground capacitance according to project requirements, determine the parallel reactor line compensation method according to the standard design process, and calculate the inductance of each phase of the reactor according to the reactor capacity;

S2: Calculate the test frequency under different wiring modes according to the inductance value of each phase of the reactor and the capacitance value of the cable to ground;

S3: If the test frequency is within the preset range, jump to S4, otherwise exclude the wiring method in which the test frequency is not within the preset range;

S4: Select any wiring method with a test frequency within the preset range, and check and design the insulation strength of the reactor according to the voltage level under this wiring method;

S5: Check and design the current amplitude of each pressurized phase and neutral point of the reactor according to the voltage level under the wiring mode;

S6: Perform magnetic field simulation calculation under this wiring mode, and check and design the iron core according to the magnetic density;

S7: Based on the magnetic field simulation under this wiring mode, the loss calculation is performed to check and design the heat dissipation of the reactor;

S8: Repeat steps S4-S7 until the wiring method design is completed so that the test frequency is within the preset range;

S9: Considering the insulation level, current tolerance level, and core interface design, determine the most economical wiring method and the corresponding design scheme to obtain a three-phase high-voltage shunt reactor that can be used for cable withstand voltage testing.

Furthermore, different wiring methods in S2 include a single-phase method, a two-phase parallel method, a three-phase parallel method and a support method.

Furthermore, the single-phase method is specifically as follows: connecting the neutral point of the reactor to the secondary side of the test excitation transformer, connecting one phase outgoing line of the reactor to the conductor of the tested cable, and performing a resonant withstand voltage test;

The two-phase parallel method is specifically as follows: the neutral point of the reactor is connected to the secondary side of the test excitation transformer, the two-phase outgoing lines of the reactor are connected in parallel and then connected to the conductor of the tested cable to perform a resonant withstand voltage test;

The three-phase parallel method is specifically as follows: the neutral point of the reactor is connected to the secondary side of the test excitation transformer, the three-phase outgoing lines of the reactor are connected in parallel and then connected to the conductor of the tested cable to perform a resonant withstand voltage test;

The supporting method is specifically as follows: two phases of the reactor are connected in parallel to the secondary side of the test excitation transformer, and the other phase is connected to the conductor of the tested cable to perform a resonant withstand voltage test.

Furthermore, S2 calculates the test frequency under different wiring modes, specifically:

Where, f is the test frequency, L is the inductance of the series reactance in the test circuit under different wiring methods, C is the capacitance of the tested cable to ground, when the single-phase method is adopted, L is L ₁ , when the two-phase parallel method is adopted, L is 0.5L ₁ , when the three-phase parallel method is adopted, L is 0.33L ₁ , when the support method is adopted, L is 1.5L ₁ , and L ₁ is the inductance of each phase of the parallel reactor.

Furthermore, the preset range in S3 is 20-300 Hz.

Furthermore, S6 is specifically as follows: calculating the magnetic flux distribution of the core under this wiring mode, comparing the B-H curve of the silicon steel sheet used in the design, the magnetic flux of the core should not be greater than the knee point of the B-H curve. When the magnetic flux distribution does not meet the design requirements, the core is redesigned to increase the cross-sectional area of the core and reduce the magnetic flux to an allowable level.

Furthermore, the loss calculation in S7 includes the calculation of eddy current loss, hysteresis loss and additional loss.

Furthermore, the eddy current loss calculation formula is as follows:

P _e = _Ke × B _rms ² × f ² × t ²

Where: _Pe - eddy current loss per unit volume of the core; _Ke - eddy current constant, determined by the core material; _Brms - effective value of magnetic flux density; f - frequency; t - thickness of the core laminations.

Furthermore, the hysteresis loss calculation formula is as follows:

P _b =K _p ×B _rms ⁿ ×f

Where: _Pb is the hysteresis loss per unit volume of the core; _Kp is the hysteresis loop constant, which is determined by the core material; _Brms is the effective value of the magnetic flux density; f is the frequency; n is the Steinmetz constant, which is 1.6 to 2.0 when hot-rolled laminations are used and is greater than 2.0 when cold-rolled laminations are used;

The additional loss is calculated by finite element simulation.

A three-phase high-voltage shunt reactor that can be used for cable withstand voltage test is obtained by adopting the above-mentioned design method.

Compared with the prior art, the present invention has the following beneficial technical effects:

When designing a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test, factors such as manufacturing difficulty and material cost should be considered. When selecting the wiring method, the test frequency should not be too high or too low. Since the magnetic flux density is basically inversely proportional to the frequency, when the frequency is too low, the magnetic flux density may be too large, which may easily cause the excitation current of the equipment to be distorted. On the other hand, when the frequency is too high, various losses such as hysteresis loss and eddy current loss of the iron core will also increase significantly, which may easily cause the iron core of the equipment to overheat. The present invention can design and verify the structure of the reactor according to the frequency under various wiring methods, the design requirements of the insulation level of the reactor, the current carrying capacity requirements, and the simulation results, and select the optimal wiring method and corresponding design scheme based on factors such as economy and manufacturing difficulty.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

Figure 1 shows the wiring method - single-phase method;

Figure 2 shows the wiring method - two-phase parallel method;

Figure 3 shows the wiring method - three-phase parallel method;

Figure 4 shows the wiring method - support method;

Figure 5 is a cloud diagram of the high coercivity distribution during the cable withstand voltage test;

Figure 6 is a B-H curve of the core material;

Figure 7 is a design flow chart of a three-phase high-voltage shunt reactor that can be used for cable withstand voltage.

Detailed ways

In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

A new type of three-phase high-voltage shunt reactor can be used for cable withstand voltage test while meeting the demand for reactive power compensation of cable lines, playing the role of series resonance. The design of the reactor is as follows:

1. Estimate the cable length and ground capacitance according to project requirements, and determine the parallel reactor line compensation method (undercompensation, overcompensation, etc.) according to the standard design process. Calculate the inductance value _L1 of each phase of the reactor based on the reactor capacity.

2. Design the wiring scheme. There are many wiring methods for conducting AC withstand voltage test using three-phase reactors, such as single-phase method, two-phase parallel method, three-phase parallel method, and support method. The specific wiring method of the single-phase method is shown in Figure 1. The grounding connection of the neutral point of the reactor is unlocked to ensure sufficient insulation distance, and it is connected to the secondary side of the test excitation transformer. The one-phase output line of the reactor is connected to the conductor of the tested cable to conduct a resonant withstand voltage test. The wiring of the two-phase parallel method and the three-phase parallel method are shown in Figures 2 and 3 respectively. Similar to the single-phase method, it is necessary to connect the neutral point of the reactor to the secondary side of the test excitation transformer, and the two-phase or three-phase windings of the reactor are connected in parallel to the conductor of the tested cable to conduct a resonant withstand voltage test. The wiring method of the support method is to connect the two phases in parallel to the secondary side of the test excitation transformer, and the other phase to the conductor of the tested cable.

Considering the symmetry and uniformity of the magnetic flux distribution of the high-voltage reactor in the test, the magnetic circuit is used more effectively to reduce the magnetic flux. It is recommended to take phase B for the test in the single-phase method; take phases A and C in parallel in the two-phase parallel method; and connect phases A and C in parallel to the excitation transformer in the support method, and phase B to the tested cable. In this connection method, phases A and C are called supporting phases, and phase B is called the supported phase.

The three-phase reactor structure includes three-phase three-column type and three-phase five-column type. Due to the problem of loop magnetic density, it is obvious that the three-phase parallel method is not applicable to the three-phase five-column reactor.

3. Test frequency calculation: The inductance value L of the series reactor in the test circuit under each connection method is different, namely L ₁ , 0.5L ₁ , 0.33L ₁ , and 1.5L ₁ (corresponding to the single-phase method, two-phase parallel method, three-phase parallel method, and support method, respectively; L ₁ is the inductance value of each phase winding of the parallel reactor). The calculation formula for the circuit resonant frequency under various connection conditions is shown in formula (1).

Where, f is the test frequency, L is the inductance of the series reactance in the test circuit under different wiring methods, and C is the capacitance of the tested cable to ground.

4. Reactor insulation level design: According to the relevant requirements of the national standard GB 50150-2016 "Electrical Equipment Acceptance Test Standard for Electrical Installation Engineering", 35kV and above cross-linked cables should adopt 20-300Hz AC withstand voltage test, and the withstand voltage test parameter requirements are shown in Table 1. Under the above various connection methods, the insulation level of the high-voltage outlet and neutral point outlet of the high-voltage reactor is redesigned and calculated to meet the test requirements. The specific requirements are shown in Table 2.

Table 1 Cable AC withstand voltage test voltage and time

Table 2 Design requirements for insulation strength of reactor

5. The current tolerance capacity of the neutral point of the reactor and each voltage phase is designed and checked. For smoothing reactors of cables of different voltage levels, according to the single-phase method, two-phase parallel method, three-phase parallel method and support method, the current levels of the voltage phase and neutral point are shown in Table 3.

Table 3 Design requirements for current withstand capability of reactor

In the table, L and ω are the inductance of the series reactor of the test circuit and the corresponding resonant frequency. The values of L and ω are different under different wiring methods. When using the single-phase method, two-phase parallel method, three-phase parallel method, and support method, the values of L are L ₁ , 0.5L ₁ , 0.33L, and 1.5L ₁ , respectively. L ₁ is the inductance of each phase of the parallel reactor. ω is 2πf, and the calculation formula of f is as shown in formula (1).

Perform magnetic field simulation calculation on the reactor and calculate the magnetic flux density distribution of the core under various wiring modes:

In the formula: B _max is the maximum value of magnetic induction intensity, _Ems is the effective value of voltage, f is the resonant frequency, N is the number of winding turns, and S is the effective area of the core.

Therefore, when the resonant frequency f is low, the magnetic induction intensity B _max may be large. The magnetic field simulation results when the support method is used under certain test conditions are shown in Figure 5. The BH curve of the silicon steel sheet used in the comparative design is shown in Figure 6. The core magnetic flux density should not be greater than the knee point of the BH curve to avoid excitation current distortion in the transformer. When the magnetic flux density distribution does not meet the design requirements, the core needs to be redesigned to increase the core cross-sectional area and reduce the magnetic flux density to an allowable level.

6. Based on the magnetic field simulation of various connection methods, various losses including eddy current loss, hysteresis loss, additional loss, etc. are calculated to ensure that the heat dissipation design of the equipment can meet the continuous operation of the reactor for one hour under the wiring conditions.

The eddy current loss calculation formula is as follows:

P _e = _Ke × B _rms ² × f ² × t ² (2)

The calculation formula of hysteresis loss is as follows:

P _b =K _p ×B _rms ⁿ ×f (3)

Where: _Pb - hysteresis loss per unit volume of core; _Kp - hysteresis loop constant, determined by core material; _Brms - effective value of magnetic flux density; f - frequency; n - Steinmetz constant, n for hot-rolled laminations is 1.6 to 2.0, and n for cold-rolled laminations is greater than 2.0.

From the calculation formulas of eddy current loss and hysteresis loss, it can be seen that the loss is related to magnetic flux density and frequency. When performing simulation, it is necessary to consider the heating phenomenon caused by various losses in the reactor during the test and verify and improve the design.

It is necessary to consider the additional losses caused by leakage flux in structural components such as oil tanks, clamps and pull plates, and use finite element simulation to calculate them.

7. Summarizing 1 to 6, the design flow chart of high-voltage shunt reactor that can be used for cable withstand voltage test is shown in Figure 7.

When designing a three-phase high-voltage shunt reactor that can be used for cable withstand voltage testing, factors such as manufacturing difficulty and material cost should be considered comprehensively, and the best design solution should be selected based on Items 3 to 6. When selecting the wiring method, the test frequency should not be too high or too low.

It can be seen that the magnetic flux density is basically inversely proportional to the frequency. When the frequency is too low, the magnetic flux density may be too large, close to the knee point of the BH curve of the equipment core material, which may easily cause the equipment excitation current distortion. On the other hand, when the frequency is too high, various losses such as hysteresis loss and eddy current loss of the core will also increase significantly, which may easily cause the equipment core to overheat. The structure of the reactor can be designed and verified according to the frequency under various wiring methods, the design requirements of the reactor insulation level, the current carrying capacity requirements and the simulation results, and the optimal wiring method and corresponding design scheme can be selected based on the comprehensive factors such as economy and manufacturing difficulty.

Example

The test product is a 330kV cable with a length of about 10km. The selected cable cross-section is ^2500mm2 , and its unit length capacitance is about 0.22μF/km (75228kVar). When testing phase by phase, the capacitance of the test product per phase is about 2.2μF. According to the reactive power compensation design, the pre-configured reactor is a three-phase integrated reactor with a rated capacity of 90000kvar and a rated voltage of 363/√3kV.

The following is the calculation of various parameters of the reactor:

① Reactor single-phase inductance value and test frequency of each connection method

According to the single-phase capacity S, the single-phase inductance value can be obtained as

L ₁ =U ² /2πfS

L ₁ = (363000/√3) ² / (2πf×30000000) = 4.66H

In the formula, the voltage borne by the single-phase coil is 363000/√3V, and the capacity of the single-phase is 30000000var.

That is, the inductance value _L1 of each phase winding of the shunt reactor is about 4.66H. The test frequencies under various connection methods are calculated respectively, and the calculation results are as follows:

Table 4 Test frequency under various wiring methods

The frequency under the three-phase parallel connection method does not meet the 30-80Hz test requirements of the cable withstand voltage test.

①Insulation level design under various connection methods and its comparison with standard design requirements of reactors

According to GB 50150-2016 "Electrical Equipment Acceptance Test Standard for Electrical Installation Engineering", when conducting AC withstand voltage test on 330kV cable, the test voltage is 1.7U ₀ , i.e. 1.7×330/√3＝323kV, and the voltage duration is 1 hour. Therefore, the insulation level of the reactor under various connection methods is as follows:

Single-phase method, two-phase parallel method, three-phase method: The winding outlet and bushing connected to the tested cable must meet the withstand voltage level of at least 323kV and 1 hour, and the insulation level of the corresponding winding outlet and bushing must be calculated;

Support method: In this connection method, two phases are connected in parallel and then in series with the third winding. For example, phases A and C are connected in parallel and then in series with phase B. The B-phase bushing is connected to the tested cable. In this connection method, phases A and C are called supporting phases, and phase B is the supported phase. At this time, the voltage of phases A and C is the output voltage of the excitation transformer, which is lower than the design value of the inductor. The output voltage of phase B is 323kV, and the voltage value at the neutral point is 323/3＝107.6kV, and both need to withstand the voltage for 1 hour.

Compared with the standard design requirements of reactors: According to the requirements of DLT 271-2012 "Technical Conditions for the Use of 330-750kV Oil-immersed Shunt Reactors", the rated insulation levels of shunt reactors and their bushings are as follows. The maximum effective voltage values of the equipment in the second column of the table, 363kV, 126kV, and 72.5kV, are all line voltages.

Table 5 Conventional design insulation level of 330kV shunt reactor

According to GB1094.3-2017 "Power Transformer Part 3: Insulation Level, Insulation Test and External Insulation Air Gap" and GB1094.6-2011 "Power Transformer Part 6: Reactor", the reactor needs to be subjected to an induction withstand voltage test phase by phase during the factory test, with a test voltage of 1.5U _m /√3 (U _m is 363kV) and a test time of 1 hour. During the withstand voltage test, the relative voltage to ground is 314kV, which is slightly lower than the cable test requirement of 323kV. Therefore, in this example, when the single-phase method, two-phase parallel method, and three-phase method are used, under the standard reactor design, the insulation margin of each part of the reactor can basically meet the cable AC withstand voltage test requirements, and it is necessary to slightly strengthen and leave enough insulation margin during the design. When the support method is used, the voltage of the reactor supported relative to ground is 323kV, and the neutral point needs to withstand 107.6kV, so it is necessary to consider the insulation level and leave enough insulation margin during the design.

② Design and verification of the current tolerance of the neutral point of the reactor and each voltage phase

Based on the design requirements of the reactor current withstand capability level in Table 3 above and the cable paper and resonant frequency of the test circuit under various wiring methods, the current under each wiring method in this case can be calculated as shown in Table 6 below.

Table 6 Phase current levels under various wiring methods

④ Reactor magnetic field simulation calculation and power consumption calculation

When designing coil-type equipment with iron cores, such as reactors and transformers, it is necessary to fully consider the maximum magnetic flux density of the iron core so that it is not greater than the knee point of the B-H curve of the core material to prevent oversaturation of the core and distortion of the excitation current.

According to the calculation formula of winding electromotive force and magnetic flux

E _rms ≈4.44fNΦ _max ≈4.44fNB _max S

Where _Ems is the effective value of the induced electromotive force, f is the frequency, N is the number of turns, Ф _max is the maximum magnetic flux, and B _max is the maximum magnetic density.

Therefore, it can be seen that when the voltage remains unchanged, the maximum magnetic flux density is inversely proportional to the frequency. When conducting the AC withstand voltage test of the cable, the test frequency may be lower than 50Hz, resulting in an increase in magnetic flux density. Therefore, it is necessary to fully consider this in the design and increase the core cross section if necessary. The design can be verified by finite element simulation and other methods.

During the AC withstand voltage test of the cable, when the three-phase cable is tested separately, it is necessary to conduct three tests with a high voltage reactor, each time continuously withstanding the test voltage for more than 1 hour, and the heating and loss issues need to be fully considered. The heating of the reactor includes the hysteresis loss and eddy current loss of the core, the additional loss of the accessories, the resistance loss of the winding, etc. Among them, the hysteresis loss and eddy current loss need to be fully considered, and the design verification can be carried out through finite element simulation calculation.

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 its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

A design method for a three-phase high-voltage shunt reactor that can be used for a cable withstand voltage test is characterized by comprising the following steps:

S1: Estimate the cable length and ground capacitance according to project requirements, determine the parallel reactor line compensation method according to the standard design process, and calculate the inductance of each phase of the reactor according to the reactor capacity;

S2: Calculate the test frequency under different wiring modes according to the inductance value of each phase of the reactor and the capacitance value of the cable to ground;

S3: If the test frequency is within the preset range, jump to S4, otherwise exclude the wiring method in which the test frequency is not within the preset range;

S4: Select any wiring method with a test frequency within the preset range, and check and design the insulation strength of the reactor according to the voltage level under this wiring method;

S5: Check and design the current amplitude of each pressurized phase and neutral point of the reactor according to the voltage level under the wiring mode;

S6: Perform magnetic field simulation calculation under this wiring mode, and check and design the iron core according to the magnetic density;

S7: Based on the magnetic field simulation under this wiring mode, the loss calculation is performed to check and design the heat dissipation of the reactor;

S8: Repeat steps S4-S7 until the wiring method design is completed so that the test frequency is within the preset range;

S9: Considering the insulation level, current tolerance level, and core interface design, determine the most economical wiring method and the corresponding design scheme to obtain a three-phase high-voltage shunt reactor that can be used for cable withstand voltage testing.
The design method of a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test according to claim 1 is characterized in that the different wiring methods in S2 include a single-phase method, a two-phase parallel method, a three-phase parallel method and a support method.
The design method of a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test according to claim 2 is characterized in that the single-phase method is specifically: connecting the neutral point of the reactor to the secondary side of the test excitation transformer, connecting one phase outgoing line of the reactor to the conductor of the tested cable, and performing a resonant withstand voltage test;

The two-phase parallel method is specifically as follows: the neutral point of the reactor is connected to the secondary side of the test excitation transformer, the two-phase outgoing lines of the reactor are connected in parallel and then connected to the conductor of the tested cable to perform a resonant withstand voltage test;

The three-phase parallel method is specifically as follows: the neutral point of the reactor is connected to the secondary side of the test excitation transformer, the three-phase outgoing lines of the reactor are connected in parallel and then connected to the conductor of the tested cable to perform a resonant withstand voltage test;

The supporting method is specifically as follows: two phases of the reactor are connected in parallel to the secondary side of the test excitation transformer, and the other phase is connected to the conductor of the tested cable to perform a resonant withstand voltage test.
The design method of a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test according to claim 2 is characterized in that the test frequency under different wiring modes is calculated in S2, specifically:

Where, f is the test frequency, L is the inductance of the series reactance in the test circuit under different wiring methods, C is the capacitance of the tested cable to ground, when the single-phase method is adopted, L is L 1 , when the two-phase parallel method is adopted, L is 0.5L 1 , when the three-phase parallel method is adopted, L is 0.33L 1 , when the support method is adopted, L is 1.5L 1 , and L 1 is the inductance of each phase of the parallel reactor.
The design method of a three-phase high-voltage shunt reactor that can be used for a cable withstand voltage test according to claim 1 is characterized in that the preset range in S3 is 20-300 Hz.
The design method of a three-phase high-voltage shunt reactor that can be used for a cable withstand voltage test according to claim 1 is characterized in that S6 specifically comprises: calculating the magnetic flux distribution of the core under the wiring mode, comparing the B-H curve of the silicon steel sheet used in the design, the magnetic flux of the core should not be greater than the knee point of the B-H curve, and when the magnetic flux distribution does not meet the design requirements, the core is redesigned to increase the cross-sectional area of the core and reduce the magnetic flux to an allowable level.
The design method of a three-phase high-voltage shunt reactor that can be used for a cable withstand voltage test according to claim 1 is characterized in that the loss calculation in S7 includes the calculation of eddy current loss, hysteresis loss, and additional loss.
The design method of a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test according to claim 7 is characterized in that the eddy current loss calculation formula is as follows:

P e = Ke × B rms 2 × f 2 × t 2

Where: Pe - eddy current loss per unit volume of the core; Ke - eddy current constant, determined by the core material; Brms - effective value of magnetic flux density; f - frequency; t - thickness of the core laminations.
The design method of a three-phase high-voltage shunt reactor that can be used for cable withstand voltage test according to claim 7 is characterized in that the hysteresis loss calculation formula is as follows:

P b =K p ×B rms n ×f

Where: Pb is the hysteresis loss per unit volume of the core; Kp is the hysteresis loop constant, which is determined by the core material; Brms is the effective value of the magnetic flux density; f is the frequency; n is the Steinmetz constant, which is 1.6 to 2.0 when hot-rolled laminations are used and is greater than 2.0 when cold-rolled laminations are used;

The additional loss is calculated by finite element simulation.
A three-phase high-voltage shunt reactor that can be used for cable withstand voltage test, characterized in that it is obtained by adopting the design method described in any one of claims 1 to 9.