System for induction partial discharge test of three-phase flexible direct-current connection transformer

Abstract

The utility model relates to a system used for an induction partial discharge test of a three-phase flexible DC connection transformer, one end of an output side of a single-phase power supply system is provided with a voltage increasing line, the other end of the output side of the single-phase power supply system is provided with a grounding connection line, and the grounding connection line is always connected with a grounding O end of the tested connection transformer. When a B-phase induction partial discharge test is carried out, the pressurization wire is connected with the B-phase test sleeve, the c-phase body sleeve is connected with the valve-side first grounding wire, the a-phase body sleeve is connected with the valve-side second grounding wire, and when a B-phase induction partial discharge test is carried out, the pressurization wire is connected with the B-phase test sleeve, the c-phase body sleeve is connected with the valve-side first grounding wire, and the b-phase body sleeve is connected with the valve-side second grounding wire. When a C-phase induction partial discharge test is carried out, the pressurization wire is connected with the C-phase test sleeve, the a-phase body sleeve is connected with the valve side first grounding wire, and the c-phase body sleeve is connected with the valve side second grounding wire. According to the utility model, the test requirement of the flexible connection transformer of the offshore platform can be met.

Description

Technical Field

[0001] The utility model relates to the technical field of transformer testing, in particular to a system for inductive partial discharge testing of a three-phase flexible direct current connection transformer. Background Art

[0002] Flexible DC transmission is a new type of DC transmission technology that meets the requirements of long-distance transmission of offshore wind farms. It has become the preferred technology for offshore wind farm network transmission, and the flexible connection transformer is the key equipment for this type of project.

[0003] The induced partial discharge test is a key part of the on-site acceptance test of the flexible connection transformer. For the connection transformer with three-phase cable outlet, if you want to shorten the on-site test time, according to the conventional test wiring method, you need to install temporary test bushings on the network and valve sides respectively, which requires a larger external insulation space. However, the test space on the offshore platform is limited, which usually cannot meet the external insulation distance requirements of the induced partial discharge test under conventional wiring. At the same time, according to the equipment capacity of the on-site test system of the offshore platform, only single-phase power supply can be used for pressure testing. Therefore, if the conventional wiring method is used, in addition to the valve side external insulation distance not meeting the requirements, the valve side to ground voltage test value will also exceed the transformer valve side test allowable value, especially for the connection transformer with a valve side voltage level exceeding 400KV. Therefore, what wiring method to use for the offshore platform induced partial discharge test has become a technical problem.

[0004] The patent with the authorization announcement number CN208188266U discloses a three-phase inductive withstand voltage and partial discharge test system for transformers. The innovation of this system is that: a magnetically controlled reactor is connected to the connection line between the three-phase output end of the excitation transformer and the three-phase input end of the tested transformer. When the three-phase partial test of the transformer is carried out, the three magnetically controlled reactors on the connection line between the three-phase output end of the excitation transformer and the three-phase input end of the tested transformer respectively control each magnetically controlled reactor to control the winding current to change its inductive reactance value, thereby achieving the purpose of adjusting the size of the reactance current and smoothly adjusting the inductance, and then achieving the requirements of phase compensation of the partial discharge test, but the system still needs to use bushing capacitors at the output end of the tested product. The patent with the authorization announcement number CN201402305Y discloses a wiring structure for partial discharge test of dry-type transformers, but the structure is three-phase symmetrical pressure on the low-voltage side, while the high-voltage circuit is Y-connected, the neutral point N is grounded, and the high-voltage side is connected to the partial discharge tester PD, which is mainly for 35kV dry-type transformers. Utility Model Content

[0005] The purpose of the utility model is to provide a system for induced partial discharge test of three-phase flexible DC connection transformer, which can meet the test requirements of valve side voltage to ground and phase-to-phase voltage when conducting on-site partial discharge test, and at the same time, there is no need to set valve side test bushing on the valve side of the tested connection transformer, and the test power supply can be realized by using a single-phase power supply system, which can meet the test needs of flexible connection transformer on offshore platforms.

[0006] The purpose of this utility model is achieved through the following technical solutions:

[0007] A system for induced partial discharge test of three-phase flexible DC connection transformer, comprising a single-phase power supply system, a connection transformer to be tested, a first measuring component and a second measuring component, wherein the grid side of the connection transformer to be tested is provided with an A-phase test bushing, a B-phase test bushing and a C-phase test bushing, the valve side of the connection transformer to be tested is provided with an a-phase body bushing, a b-phase body bushing and a c-phase body bushing, one end of the output side of the single-phase power supply system is provided with a pressurized line and the other end is provided with a grounding connection line, and the grounding connection line is always connected to the grounding O terminal of the connection transformer to be tested, when performing an A-phase induced partial discharge test, the pressurized line is connected to the A-phase test bushing, and the b-phase body bushing is connected to the grounding O terminal of the connection transformer to be tested. The main body sleeve is connected to the first grounding wire on the valve side, the a-phase main body sleeve is connected to the second grounding wire on the valve side, and the second grounding wire on the valve side is provided with a first measuring component. When conducting a B-phase induced partial discharge test, the pressurized line is connected to the B-phase test sleeve, the c-phase main body sleeve is connected to the first grounding wire on the valve side, and the b-phase main body sleeve is connected to the second grounding wire on the valve side. When conducting a C-phase induced partial discharge test, the pressurized line is connected to the C-phase test sleeve, the a-phase main body sleeve is connected to the first grounding wire on the valve side, and the c-phase main body sleeve is connected to the second grounding wire on the valve side. In addition, the pressurized line is always connected to the grid side grounding wire, and a second measuring component is provided on the grid side grounding wire.

[0008] The valve side of the tested connected transformer is provided with multiple elevated seats, and the a-phase body bushing, b-phase body bushing and c-phase body bushing are respectively arranged in the corresponding elevated seats, the a-phase body bushing, b-phase body bushing and c-phase body bushing are each provided with a first socket, and a second socket is provided on the outside of each elevated seat, and a valve-side bushing end screen grounding lead wire is provided inside each elevated seat, and one end of the valve-side bushing end screen grounding lead wire is connected to the corresponding first socket, and the other end is connected to the corresponding second socket. When performing the induced partial discharge test, the valve-side first grounding wire and the valve-side second grounding wire are each provided with a plug connected to the corresponding second socket respectively.

[0009] A lead-out sleeve is provided at one side of the transformer to be tested, and a welding flange is provided at the free end of the lead-out sleeve, which is sleeved on the corresponding raised seat to realize welding and fixing, and the second socket is provided on the corresponding welding flange.

[0010] The single-phase power supply system includes a variable frequency power supply, an excitation transformer, a compensating inductor and a high-voltage voltage divider, wherein the output side of the variable frequency power supply is connected to the input side of the excitation transformer, one end of the output side of the excitation transformer is connected to the pressurized line and the other end is connected to the grounding connection line, and the compensating inductor and the high-voltage voltage divider are both connected to the pressurized line at one end and the other end is connected to the grounding connection line.

[0011] The first measuring component and the second measuring component have the same structure, and both include a coupling capacitor, a detection impedance and a partial discharge tester.

[0012] The advantages and positive effects of the utility model are:

[0013] 1. The utility model adopts a special wiring structure to achieve the purpose of meeting the valve side voltage to ground test requirements when conducting on-site partial discharge tests. Taking the A-phase test as an example, the prior art tests the A-phase with the C-phase grounded, and the a-phase voltage Ua-ground is greater than the test allowable value. The utility model tests the A-phase with the a and b phases grounded, and the a, b, and c-phase voltages are all less than the test allowable value.

[0014] 2. The a-phase body sleeve, b-phase body sleeve and c-phase body sleeve of the utility model are respectively arranged in the corresponding lifting seats, and the a-phase body sleeve, b-phase body sleeve and c-phase body sleeve are each provided with a first socket, and each lifting seat is provided with a second socket, and each lifting seat is provided with a valve side sleeve end screen grounding lead wire, one end of the valve side sleeve end screen grounding lead wire is connected to the corresponding first socket, and the other end is connected to the corresponding second socket. The utility model realizes the connection of the external valve side first grounding wire and the valve side second grounding wire with the corresponding phase body sleeve through the valve side sleeve end screen grounding lead wire and the socket structure, which is convenient for test conversion and does not need to set up structures such as valve side test sleeves, and can meet the needs of offshore platform testing.

[0015] 3. The utility model can realize test power supply by using a single-phase power supply system, which can further meet the test needs of offshore platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the wiring structure of the utility model when the transformer under test is subjected to an induced partial discharge test.

[0017] Figure 2 for Figure 1 Enlarged schematic diagram of the grounding lead wire of the casing end screen on the middle valve side.

[0018] Figure 3 for Figure 1 A-direction view of the connected transformer under test,

[0019] Figure 4 for Figure 3Top view of the connected transformer under test,

[0020] Figure 5 It is a schematic diagram of the wiring structure when the transformer under test is subjected to an induced partial discharge test in the prior art.

[0021] Figure 6 for Figure 5 Top view of the connected transformer under test,

[0022] Figure 7 This is the electrical wiring diagram of the utility model when the tested connected transformer is subjected to the A-phase induced partial discharge test.

[0023] Figure 8 This is a schematic diagram of the wiring principle when the A-phase induced partial discharge test is carried out on the transformer under test in the utility model.

[0024] Fig. 9 This is a schematic diagram of the wiring principle when the tested connected transformer of the utility model is subjected to the B-phase induced partial discharge test.

[0025] Fig.10 This is a schematic diagram of the wiring principle when the C-phase induced partial discharge test is carried out on the tested connected transformer of the utility model.

[0026] Among them, 1 is the A-phase test bushing, 2 is the B-phase test bushing, 3 is the C-phase test bushing, 4 is the a-phase main body bushing, 5 is the b-phase main body bushing, 6 is the c-phase main body bushing, 7 is the valve side bushing end screen grounding lead-out wire, 8 is the valve side first grounding wire, 9 is the lead-out sleeve, 10 is the rising seat, 11 is the first socket, 12 is the second socket, 13 is the welding flange, 14 is the valve side test bushing, 15 is the single-phase power supply system, 1501 is the pressurized line, 1502 is the grounding connection line, 1503 is the variable frequency power supply, 16 is the valve side second grounding wire, 17 is the first measurement component, 18 is the grid side grounding wire, and 19 is the second measurement component.

[0027] T 0 is the transformer under test, T 1 is the excitation transformer, L is the compensation reactor, C VD For the high voltage divider, C A is the coupling capacitance, Z A To detect impedance, PD is a partial discharge tester. DETAILED DESCRIPTION

[0028] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0029] like Figures 1 to 10 As shown, the utility model includes a single-phase power supply system 15, a connection transformer T 0 , a first measuring component 17 and a second measuring component 19, wherein Figures 1 to 4As shown, the measured connection transformer T 0 The grid side is provided with an A-phase test bushing 1, a B-phase test bushing 2 and a C-phase test bushing 3. The tested connection transformer T 0 The valve side is provided with a phase a body bushing 4, a phase b body bushing 5 and a phase c body bushing 6, and the output side of the single-phase power supply system 15 is provided with a pressurized line 1501 at one end and a grounding connection line 1502 at the other end, and the grounding connection line 1502 is always connected to the measured connection transformer T 0 The ground O terminal is connected, such as Figures 7-8 As shown, when the A-phase induced partial discharge test is performed, the pressurized line 1501 is connected to the A-phase test bushing 1, the b-phase body bushing 5 is connected to the valve-side first grounding line 8, the a-phase body bushing 4 is connected to the valve-side second grounding line 16, and the valve-side second grounding line 16 is provided with a first measuring component 17, as shown in FIG. Fig. 9 As shown, when the B phase induced partial discharge test is performed, the pressurized line 1501 is connected to the B phase test bushing 2, the C phase body bushing 6 is connected to the first valve side grounding line 8, and the B phase body bushing 5 is connected to the second valve side grounding line 16, as shown in FIG. Fig.10 As shown, when the C phase induced partial discharge test is performed, the pressurized line 1501 is connected to the C phase test sleeve 3, the a phase body sleeve 4 is connected to the valve side first grounding line 8, and the c phase body sleeve 6 is connected to the valve side second grounding line 16. Figure 7 As shown, the pressurizing line 1501 is always connected to the grid-side grounding line 18 , and a second measuring component 19 is provided on the grid-side grounding line 18 .

[0030] like Figures 1 to 4 As shown, the measured connection transformer T 0 The valve side is provided with a plurality of raised seats 10, and the a-phase body sleeve 4, the b-phase body sleeve 5 and the c-phase body sleeve 6 are respectively arranged in the corresponding raised seats 10, such as Figure 2 As shown, the a-phase body sleeve 4, the b-phase body sleeve 5 and the c-phase body sleeve 6 are all provided with a first socket 11, the outer side of each elevation seat 10 is provided with a second socket 12, and the inside of each elevation seat 10 is provided with a valve side sleeve end screen grounding lead 7, and one end of the valve side sleeve end screen grounding lead 7 is connected to the corresponding first socket 11, and the other end is connected to the corresponding second socket 12, as shown in FIG. Figure 7 As shown, when conducting the induction partial discharge test, the first valve side grounding wire 8 and the second valve side grounding wire 16 are both provided with plugs and connected to the corresponding second sockets 12 respectively, and then connected to the corresponding phase body bushing through the corresponding valve side bushing end screen grounding lead wire 7. This structure also facilitates the test conversion of different phases. Figures 5-6 As shown, in the prior art, the transformer T 0In addition to the A-phase test bushing 1, B-phase test bushing 2 and C-phase test bushing 3 required on the grid side, the connected transformer T 0 Three valve side test sleeves 14 need to be set up on the valve side, and the valve side test sleeves 14 need to have a larger external insulation space. Because the spatial distance requirements of the offshore platform are strict and the space is limited, the present application replaces the existing valve side test sleeves 14 with the above structure to meet the needs of offshore platform testing.

[0031] like Figures 1-2 As shown, in this embodiment, the measured connection transformer T 0 One side is provided with a lead-out sleeve 9 , and a welding flange 13 is provided at the free end of the lead-out sleeve 9 to be sleeved on the corresponding raised seat 10 to achieve welding and fixing, and the second socket 12 is provided on the corresponding welding flange 13 .

[0032] like Figure 7 As shown, in this embodiment, the single-phase power supply system 15 includes a variable frequency power supply 1503, an excitation transformer T 1 , compensation reactor L and high voltage divider C VD , where the output side of the variable frequency power supply 1503 is connected to the excitation transformer T 1 Input side connection, excitation transformer T 1 One end of the output side is connected to the pressurized line 1501, and the other end is connected to the ground connection line 1502, and the compensation reactor L and the high voltage divider C VD One end is connected to the pressurized wire 1501, and the other end is connected to the ground connection wire 1502. In this embodiment, the variable frequency power supply 1503 is a single-phase variable frequency AC power supply, which is used to provide voltage, excitation transformer T 1 Provide the connection transformer T under test 0 The rated voltage on the grid side, the compensation reactor L compensates the connected transformer T under test 0 Capacitive current, high voltage divider C VD Correction excitation transformer T 1 The variable frequency power supply 1503, the excitation transformer T 1 , compensation reactor L and high voltage divider C VD All of these are well-known techniques in this field.

[0033] like Figure 7 As shown, in this embodiment, the first measuring component 17 and the second measuring component 19 have the same structure and both include a coupling capacitor C A , detection impedance Z A and partial discharge tester PD, where the coupling capacitor C A Take the partial discharge signal from the end screen of the casing on the valve side and detect the impedance Z A Measure the partial discharge value, the partial discharge tester PD shows the connected transformer T under test0 The coupling capacitor C A , detection impedance Z A The partial discharge tester PD is well known in the art.

[0034] The working principle of the utility model is:

[0035] like Figures 5-6 As shown, in the prior art, the transformer T 0 The grid side needs to be equipped with A-phase test bushing 1, B-phase test bushing 2 and C-phase test bushing 3, and the transformer under test T 0 Three valve side test sleeves 14 need to be set up on the valve side, and the valve side test sleeve 14 needs to have a larger external insulation space, which cannot be used on offshore platforms. In addition, there is a problem that the valve side test voltage value to the ground exceeds the test allowable value. A test example is listed below to illustrate this.

[0036] Test example 1:

[0037] In this test example, the rated data are:

[0038] Uac′=416.41kV, Ur=230kV;

[0039] Um=252kV;

[0040] Where Uac′ is the rated voltage between phase a and phase c, U AO ′ is the rated voltage between phase A and ground O terminal, Ur is the connected transformer T under test 0 The grid-side rated voltage, Um is the connected transformer T under test 0 Maximum operating voltage on the grid side.

[0041] according to Figures 5-6 The potential of each part of the existing connection method shown is calculated as follows: (Take phase A as an example, phase C is grounded)

[0042] Induction multiple K = 1.5;

[0043] The voltage of A relative to ground is:

[0044] The voltage between B and C is:

[0045]

[0046] The AB phase voltage and AC phase voltage are: U AB =U AC =1.5×199.2=298.8kV;

[0047] The voltage at the ground O terminal is: UO =0kV;

[0048] The actual voltage between ac phases is: Uac = Uac' × 1.5 = 416.41 × 1.5 = 625 kV;

[0049] a The voltage relative to ground is:

[0050] Ua-ground = +Uac = 625kV (greater than the test allowable value 630×0.8=504kV);

[0051] c relative to ground voltage: Uc-ground = 0kV;

[0052] b The voltage relative to ground is: Ub-ground = +Uac / 2 = +625 / 2 = 312.5kV.

[0053] From the above, it can be seen that the existing connection method Ua-ground is greater than the test allowable value.

[0054] And as Figures 8 to 10 As shown, the utility model adopts a special grounding method, specifically: the grounding connection line 1502 on one side of the single-phase power supply system 15 is always connected to the measured connection transformer T 0 However, when conducting the A-phase induced partial discharge test, if Figure 7 As shown, the pressurized line 1501 on one side of the single-phase power supply system 15 is connected to the A-phase test bushing 1, and both the a-phase and the b-phase are grounded, wherein the b-phase body bushing 5 is connected to the first grounding wire 8 on the valve side to achieve grounding, and the a-phase body bushing 4 is connected to the second grounding wire 16 on the valve side provided with the first measuring component 17. When the B-phase induced partial discharge test is performed, as shown in FIG. Fig. 9 As shown, the pressurized line 1501 on one side of the single-phase power supply system 15 is connected to the B-phase test bushing 2, and both the c-phase and the b-phase are grounded, wherein the c-phase 5 is connected to the first grounding line 8 on the valve side, and the b-phase is connected to the second grounding line 16 on the valve side. When the C-phase induced partial discharge test is performed, Fig.10 As shown, the pressurized line 1501 on one side of the single-phase power supply system 15 is connected to the C-phase test bushing 3, and both the a-phase and the c-phase are grounded, the a-phase is connected to the valve-side first grounding line 8, and the c-phase is connected to the valve-side second grounding line 16. The utility model can meet the test requirements of the valve-side voltage to ground through the above wiring method, and a test example is listed below for explanation.

[0055] Test Example 2:

[0056] In this test case, the rated data is the same as that in test case 1, which are:

[0057] Uac′=416.41kV, Ur=230kV;

[0058] Um=252kV.

[0059] Taking phase A as an example (phases B and C are the same as phase A), the above wiring method of the utility model is to increase the voltage of the single-phase power supply on the low-voltage side, and the high-voltage side circuit is angle-connected, such as Figure 7 As shown in the figure, when testing phase A, both phase a and phase b are grounded, and voltage is applied from both ends of A and O on the grid side, where phase b on the valve side is grounded. The waveform should be as sinusoidal as possible, and the test voltage measurement should be the peak value of the measured voltage divided by The partial discharge tester PD in the first measuring assembly 17 and the second measuring assembly 19 is used to measure the partial discharge amount on the grid side and the valve side respectively, and the standard high voltage divider C is used to measure the partial discharge amount on the grid side and the valve side respectively. VD Correct the voltage at the network side, and the potential of each part is calculated as follows:

[0060] Induction multiple K = 1.5;

[0061] The voltage of A relative to ground is:

[0062] The voltage between B and C is:

[0063]

[0064] The AB phase voltage and AC phase voltage are: U AB =U AC =1.5×199.2=298.8kV;

[0065] The voltage at the ground O terminal is: U O =0kV;

[0066] The above calculation is the same as that of test example 1;

[0067] The actual AC phase voltage is: Uac = Uac' × 1.5 = 416.41 × 1.5 = 625 kV;

[0068] a The voltage relative to ground is:

[0069] Ua-ground = +Uac / 2 = +625 / 2 = 312.5k (less than 630×0.8 = 504kV);

[0070] The voltage relative to ground is:

[0071] Uc-ground = -Uac / 2 = -625 / 2 = -312.5kV (less than 630×0.8 = 504kV);

[0072] b The voltage relative to ground is:

[0073] Ub-ground = 0kV;

[0074] From the above, it can be known that, in the present invention, Ua-ground, Ub-ground and Uc-ground are all smaller than the test allowable values.

[0075] In addition, Figures 1 to 4 As shown, the a-phase body bushing 4, the b-phase body bushing 5 and the c-phase body bushing 6 of the utility model are all provided with a first socket 11, each elevation seat 10 is provided with a second socket 12, and each elevation seat 10 is provided with a valve side bushing end screen grounding lead 7 inside, one end of the valve side bushing end screen grounding lead 7 is connected to the corresponding first socket 11, and the other end is connected to the corresponding second socket 12. In this way, the utility model can omit the valve side test bushing 14 structure in the prior art, the platform space occupies a small area, and the economy is better. Although the overall test time of the utility model is slightly longer, it can meet the test needs of offshore platform connection transformers.

Claims

1. A system for induced partial discharge test of three-phase flexible DC connection transformer, characterized in that: The invention comprises a single-phase power supply system (15), a tested connection transformer (T0), a first measuring component (17) and a second measuring component (19), wherein the grid side of the tested connection transformer (T0) is provided with an A-phase test bushing (1), a B-phase test bushing (2) and a C-phase test bushing (3), the valve side of the tested connection transformer (T0) is provided with an a-phase body bushing (4), a b-phase body bushing (5) and a c-phase body bushing (6), one end of the output side of the single-phase power supply system (15) is provided with a pressurized wire (1501) and the other end is provided with a grounding connection wire (1502), and the grounding connection wire (1502) is always connected to the grounding O terminal of the tested connection transformer (T0), and when performing an A-phase induced partial discharge test, the pressurized wire (1501) is connected to the A-phase test bushing (1), and the b-phase body bushing (5) is connected to the first grounding wire (1502) on the valve side. (8), the a-phase body bushing (4) is connected to the second grounding wire (16) on the valve side, and the second grounding wire (16) on the valve side is provided with a first measuring component (17); when the B-phase induced partial discharge test is performed, the pressurizing line (1501) is connected to the B-phase test bushing (2), the c-phase body bushing (6) is connected to the first grounding wire (8) on the valve side, and the b-phase body bushing (5) is connected to the second grounding wire (16) on the valve side; when the C-phase induced partial discharge test is performed, the pressurizing line (1501) is connected to the C-phase test bushing (3), the a-phase body bushing (4) is connected to the first grounding wire (8) on the valve side, and the c-phase body bushing (6) is connected to the second grounding wire (16) on the valve side; in addition, the pressurizing line (1501) is always connected to the grid-side grounding wire (18), and the grid-side grounding wire (18) is provided with a second measuring component (19).

2. The system for induced partial discharge test of three-phase flexible DC connection transformer according to claim 1 is characterized in that: The valve side of the tested connection transformer (T0) is provided with a plurality of raised seats (10), and the a-phase body bushing (4), the b-phase body bushing (5) and the c-phase body bushing (6) are respectively arranged in the corresponding raised seats (10), and the a-phase body bushing (4), the b-phase body bushing (5) and the c-phase body bushing (6) are each provided with a first socket (11), and each raised seat (10) is provided with a second socket (12) on the outside, and each raised seat (10) is provided with a valve side bushing end screen grounding lead wire (7) inside, and one end of the valve side bushing end screen grounding lead wire (7) is connected to the corresponding first socket (11), and the other end is connected to the corresponding second socket (12), and when performing an inductive partial discharge test, the valve side first grounding wire (8) and the valve side second grounding wire (16) are each provided with a plug connected to the corresponding second socket (12) respectively.

3. The system for induced partial discharge test of three-phase flexible DC connection transformer according to claim 2 is characterized in that: A lead-out sleeve (9) is provided on one side of the tested connection transformer (T0), and a welding flange (13) is provided at the free end of the lead-out sleeve (9) and is sleeved on a corresponding raised seat (10) to achieve welding connection, and the second socket (12) is provided on the corresponding welding flange (13).

4. The system for induced partial discharge test of three-phase flexible DC connection transformer according to claim 1, characterized in that: The single-phase power supply system (15) comprises a variable frequency power supply (1503), an excitation transformer (T1), a compensating reactor (L) and a high voltage divider (C VD ), wherein the output side of the variable frequency power supply (1503) is connected to the input side of the excitation transformer (T1), one end of the output side of the excitation transformer (T1) is connected to the pressurized line (1501) and the other end is connected to the ground connection line (1502), the compensation reactor (L) and the high voltage divider (C VD ) are connected to the pressurized line (1501) at one end and to the ground connection line (1502) at the other end.

5. The system for induced partial discharge test of three-phase flexible DC connection transformer according to claim 1, characterized in that: The first measuring component (17) and the second measuring component (19) have the same structure and both include a coupling capacitor (C A ), detection impedance (Z A ) and partial discharge tester (PD).

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