A black start system and method for a hydropower station without a high-voltage auxiliary transformer with an internal and external bridge connection at the 220 kV voltage level

Abstract

A black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level without a high-voltage auxiliary transformer according to the present invention includes a first hydro-generator, a first 10 kV circuit breaker, a first 10 kV isolating switch, a first three-winding transformer, a first 220 kV isolating switch, a second 220 kV isolating switch, a first 220 kV circuit breaker, a third 220 kV isolating switch, a fourth 220 kV isolating switch, a first 220 kV line, a first 6 kV switch and a first 6 kV busbar; the system uses its own governor oil pressure system to store energy by the first hydro-generator, opens the guide vanes and adjusts to the rated speed, operates the excitation system to build the terminal voltage to the rated voltage, assists the superior substation to resume power supply, ensures the normal operation of the grid load, reduces the power outage loss; the system does not set up a special high-voltage auxiliary transformer, directly uses the three-winding transformer as the main transformer and the auxiliary transformer, simplifies the primary system wiring, reduces the operation steps for restoring the auxiliary power supply during black start, and at the same time reduces the investment in primary equipment, and realizes the rapid power transmission during black start.

Description

Technical Field

[0001] The present invention belongs to the technical field of black start, and particularly relates to a black start system and method for a hydropower station without a high-voltage auxiliary transformer with an internal and external bridge connection at the 220 kV voltage level. Background Art

[0002] Today, power technologies are developing rapidly along with information technology, big data technology, and blockchain technology. The types of power sources are also evolving from a single thermal power type to a diversified energy mix. Some energy sources have physical characteristics that are friendly to the power grid. For example, units with black start capabilities can relieve the power outage pressure on the power system in critical moments. However, some energy sources do not have black start capabilities due to their own factors. To transmit energy, they need to rely on external energy to resume their own operation before they can achieve energy conversion and transmission. From the perspective of the power grid, the requirements for black start are fast, stable, and accurate. All capable units are developing towards short start-up time, high stability, and accurate voltage build-up. When a power outage occurs, how to simplify the operation process and the primary equipment wiring has become the research focus. Usually, black start units are equipped with high-voltage auxiliary transformers, and corresponding switches and disconnectors are added. There are many operation steps during black start, which is not conducive to quickly transmitting power in the first place. At the same time, there is currently no application of internal and external bridge connections in black start units. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the present invention provides a black start system and method for a hydropower station without a high-voltage auxiliary transformer with an internal and external bridge connection at the 220 kV voltage level, which reduces the operation steps for restoring auxiliary power during black start, and at the same time reduces the investment in primary equipment, and realizes the rapid transmission of power during black start.

[0004] The present invention is realized through the following technical solutions:

[0005] A black start system for a hydropower station without a high-voltage auxiliary transformer with an internal and external bridge connection at the 220 kV voltage level includes a first hydro-generator, a first three-winding transformer, a first 220 kV line, and a first 6 kV bus;

[0006] The first hydro-generator is sequentially connected to the star side of the low-voltage winding of the first three-winding transformer through a first 10 kV circuit breaker, a first 10 kV isolating switch;

[0007] The delta side of the high-voltage winding of the first three-winding transformer is sequentially connected to the first 220 kV line through a first 220 kV isolating switch, a second 220 kV isolating switch, a first 220 kV circuit breaker, a third 220 kV isolating switch, a fourth 220 kV isolating switch;

[0008] The delta side of the low-voltage winding of the first three-winding transformer is connected to the first 6 kV bus through a first 6 kV switch.

[0009] Preferably, it further includes a second hydrogenerator, a second 220 kV line, and a second 6 kV busbar;

[0010] The second hydrogenerator is connected to the star side of the low-voltage winding of the second three-winding transformer via a second 10 kV circuit breaker and a second 10 kV isolating switch;

[0011] The delta side of the high-voltage winding of the second three-winding transformer is connected to the second 220 kV line via a fifth 220 kV isolating switch, a sixth 220 kV isolating switch, a second 220 kV circuit breaker, a seventh 220 kV isolating switch, an eighth 220 kV isolating switch in sequence;

[0012] The delta side of the low-voltage winding of the second three-winding transformer is connected to the second 6 kV busbar via a second 6 kV switch.

[0013] Preferably, it further includes a 6 kV tie switch, a ninth 220 kV isolating switch, a third 220 kV circuit breaker, a tenth 220 kV isolating switch, an eleventh 220 kV isolating switch, a fourth 220 kV circuit breaker, and a twelfth 220 kV isolating switch;

[0014] One end of the 6 kV tie switch is connected to the first 6 kV busbar, and the other end is connected to the second 6 kV busbar;

[0015] The ninth 220 kV isolating switch, the third 220 kV circuit breaker, and the tenth 220 kV isolating switch are connected in series. One end of the ninth 220 kV isolating switch is connected to the common point where the first 220 kV isolating switch and the second 220 kV isolating switch are connected. One end of the tenth 220 kV isolating switch is connected to the common point where the fifth 220 kV isolating switch and the sixth 220 kV isolating switch are connected;

[0016] The eleventh 220 kV isolating switch, the fourth 220 kV circuit breaker, and the twelfth 220 kV isolating switch are connected in series. One end of the eleventh 220 kV isolating switch is connected to the common point where the third 220 kV isolating switch and the fourth 220 kV isolating switch are connected. One end of the twelfth 220 kV isolating switch is connected to the common point where the seventh 220 kV isolating switch and the eighth 220 kV isolating switch are connected.

[0017] Preferably, before the first hydrogenerator starts black start with the first three-winding transformer and the first 220 kV line, the first 10 kV isolating switch, the first 220 kV isolating switch, the second 220 kV isolating switch, the third 220 kV isolating switch, the fourth 220 kV isolating switch, the second 10 kV circuit breaker, the second 10 kV isolating switch, the fifth 220 kV isolating switch, the sixth 220 kV isolating switch, the second 220 kV circuit breaker, the seventh 220 kV isolating switch, the eighth 220 kV isolating switch, the second 6 kV switch, and the 6 kV tie switch are all in the closed state, and the first 10 kV circuit breaker, the first 220 kV circuit breaker, the first 6 kV switch, the ninth 220 kV isolating switch, the third 220 kV circuit breaker, the tenth 220 kV isolating switch, the eleventh 220 kV isolating switch, the fourth 220 kV circuit breaker, and the twelfth 220 kV isolating switch are all in the open state; the first hydrogenerator, the first three-winding transformer, and the first 220 kV line are in the power-off state, the second hydrogenerator, the second three-winding transformer, the second 220 kV line, and the second 6 kV bus are in the energized state, and the first 6 kV bus is supplied with power through connection with the second 6 kV bus.

[0018] Furthermore, when the first hydrogenerator resumes power supply to the first 6 kV bus, the first hydrogenerator builds up voltage to the rated voltage, the 6 kV tie switch is in the open state, and the first 10 kV circuit breaker and the first 6 kV switch are in the closed state.

[0019] Furthermore, when the first hydrogenerator resumes power supply to the first 6 kV bus, the first hydrogenerator uses the governor oil pressure system to self-energize and start up to the rated speed, and further builds up voltage at the machine terminal to the rated voltage. First, the 6 kV tie switch is disconnected, and then the first 10 kV circuit breaker and the first 6 kV switch are closed to realize the operation of the first hydrogenerator with the first 6 kV bus as the station service power.

[0020] Furthermore, when the first hydrogenerator charges the first three-winding transformer and the first 220 kV line, the first 220 kV circuit breaker is in the closed state, and the voltages at both ends of the first 220 kV line are both the rated voltage.

[0021] Preferably, the rated voltages of the first hydrogenerator and the second hydrogenerator are 10.5 kV, and the rated voltages of the three sides of the first three-winding transformer and the second three-winding transformer are all 242 kV / 10.5 kV / 6.3 kV.

[0022] A black start method for a 220 kV voltage level hydroelectric power station with an internal and external bridge connection and no high-voltage station service transformer includes the following steps:

[0023] 1) When the first hydro-generator starts up black-starting with the first three-winding transformer and the first 220 kV line, check and confirm that the ninth 220 kV isolating switch, the third 220 kV circuit breaker, the tenth 220 kV isolating switch, the eleventh 220 kV isolating switch, and the fourth 220 kV circuit breaker are all in the open state, and proceed to step 2);

[0024] 2) Disconnect the 6 kV tie switch. The first 6 kV bus is in a power-off state. Check that the first hydro-generator is in a shutdown state, and the first three-winding transformer and the first 220 kV line are in a power-off state, and proceed to step 3);

[0025] 3) Close the first 10 kV isolating switch, the first 220 kV isolating switch, the second 220 kV isolating switch, the third 220 kV isolating switch, and the fourth 220 kV isolating switch in sequence, and proceed to step 4);

[0026] 4) Use the oil pressure of the governor oil pressure system of the first hydro-generator to start the machine to the rated speed, operate the excitation system to build the voltage of the first hydro-generator to the rated voltage, and close the first 10 kV circuit breaker, and proceed to step 5);

[0027] 5) Close the first 6 kV switch. The first 6 kV bus resumes power supply, and proceed to step 6);

[0028] 6) Close the first 220 kV circuit breaker. The first hydro-generator charges the first 220 kV line, and proceed to step 7);

[0029] 7) Check that the voltage phase sequence on the local side and the opposite side of the first 220 kV line is correct, and the indicated value is the rated voltage. The black-start of the first hydro-generator with the first three-winding transformer and the first 220 kV line is completed.

[0030] Compared with the prior art, the present invention has the following beneficial technical effects:

[0031] In the present invention, the first hydro-generator uses its own governor oil pressure system to self-store energy, opens the guide vanes and adjusts to the rated speed, operates the excitation system to build the terminal voltage to the rated voltage, closes the first 10 kV circuit breaker and the first 6 kV switch, makes full use of the characteristics of the first three-winding transformer, which acts as both a step-up transformer and a station service transformer, promptly restores the power supply of the first 6 kV bus, realizes the stable operation of the first hydro-generator with its own station service load in an island, then closes the first 220 kV circuit breaker, and immediately sends the power of the first hydro-generator to the first 220 kV line, assisting the superior substation to restore power supply, ensuring the normal operation of the power grid load, and reducing the power outage loss.

[0032] Furthermore, the first three-winding transformer and the second three-winding transformer of the present invention serve as both step-up transformers and station service transformers, reducing the investment in station service transformers. There is no need to set up redundant station service system switches and disconnecting switches, which facilitates quick operation during black start.

[0033] Furthermore, the first hydro-generator of the present invention utilizes the energy stored in its own governor hydraulic energy storage system to start up in time and build up voltage to the rated voltage, quickly restoring the power supply of the governor hydraulic energy storage system. This ensures that the first hydro-generator can operate stably with its own station service power without an external power source and can send power to the places where power supply is needed at any time.

[0034] Furthermore, the first 6kV bus and the second 6kV bus of the present invention are provided with a 6kV tie switch, realizing the interconnection and standby of the 6kV station service systems of the two machines, further enhancing the safety of the 6kV station service system. After the first hydro-generator successfully completes black start, it can supply power to the second 6kV bus through the 6kV tie switch. The first hydro-generator can also perform black start, and in the case where both outgoing lines are de-energized, black start of the two units can be achieved.

[0035] Furthermore, the present invention adopts a wiring method combining internal bridge and external bridge wiring, enabling the primary system to have the characteristics of both internal bridge and external bridge wiring, realizing the complementary advantages of the two wiring methods, increasing the flexibility of the primary system, and also facilitating the switching between the two lines during black start. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the black start system of the present invention.

[0037] Figure 2 It is a system state diagram before the first hydro-generator of the present invention performs black start with the first 220kV line.

[0038] Figure 3 It is a system state diagram when the first hydro-generator of the present invention restores the power supply of the first 6kV bus.

[0039] Figure 4 It is a charging state diagram when the first hydro-generator of the present invention charges the first 220kV line.

[0040] In the figure: First hydrogenerator 1; First 10 kV circuit breaker 2; First 10 kV isolating switch 3; First three-winding transformer 4; First 220 kV isolating switch 5; Second 220 kV isolating switch 6; First 220 kV circuit breaker 7; Third 220 kV isolating switch 8; Fourth 220 kV isolating switch 9; First 220 kV line 10; First 6 kV switch 11; First 6 kV busbar 12; Second hydrogenerator 13; Second 10 kV circuit breaker 14; Second 10 kV isolating switch 15; Second three-winding transformer 16; Fifth 220 kV isolating switch 17; Sixth 220 kV isolating switch 18; Second 220 kV circuit breaker 19; Seventh 220 kV isolating switch 20; Eighth 220 kV isolating switch 21; Second 220 kV line 22; Second 6 kV switch 23; Second 6 kV busbar 24; 6 kV tie switch 25; Ninth 220 kV isolating switch 26; Third 220 kV circuit breaker 27; Tenth 220 kV isolating switch 28; Eleventh 220 kV isolating switch 29; Fourth 220 kV circuit breaker 30; Twelfth 220 kV isolating switch 31. Detailed implementation manners

[0041] The present invention will be further described in detail below in conjunction with specific embodiments, which are explanations of the present invention rather than limitations.

[0042] The present invention can solve the problem of separately arranging a high-voltage station service transformer for the current black start unit. Without arranging a dedicated high-voltage station service transformer, the functions of a step-up transformer and a station service transformer are realized by using a three-winding transformer, simplifying the primary system wiring and being very beneficial to the operation of black start.

[0043] A black start system for a hydropower station with an inner and outer bridge connection at the 220 kV voltage level and without a high-voltage station service transformer according to the present invention, such as Figure 1As shown in the figure, a black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level and without a high-voltage auxiliary transformer includes a first hydro-generator 1, a first 10 kV circuit breaker 2, a first 10 kV isolating switch 3, a first three-winding transformer 4, a first 220 kV isolating switch 5, a second 220 kV isolating switch 6, a first 220 kV circuit breaker 7, a third 220 kV isolating switch 8, a fourth 220 kV isolating switch 9, a first 220 kV line 10, a first 6 kV switch 11, and a first 6 kV bus 12. Among them, the first hydro-generator 1 is successively connected to the star side of the low-voltage winding of the first three-winding transformer 4 through the first 10 kV circuit breaker 2, the first 10 kV isolating switch 3. The delta side of the high-voltage winding of the first three-winding transformer 4 is successively connected through the first 220 kV isolating switch 5, the second 220 kV isolating switch 6, the first 220 kV circuit breaker 7, the third 220 kV isolating switch 8, the fourth 220 kV isolating switch 9, and the first 220 kV line 10. The delta side of the low-voltage winding of the first three-winding transformer 4 is connected through the first 6 kV switch 11 and the first 6 kV bus 12.

[0044] In this embodiment, the rated power of the first hydro-generator 1 is 200 MW, the rated speed is 180 r / min, and the rated working pressure of the governor of the first hydro-generator is 3.6 Mpa.

[0045] This embodiment also includes a second hydro-generator 13, a second 10 kV circuit breaker 14, a second 10 kV isolating switch 15, a second three-winding transformer 16, a fifth 220 kV isolating switch 17, a sixth 220 kV isolating switch 18, a second 220 kV circuit breaker 19, a seventh 220 kV isolating switch 20, an eighth 220 kV isolating switch 21, a second 220 kV line 22, a second 6 kV switch 23, and a second 6 kV bus 24. Among them, the second hydro-generator 13 is connected to the star side of the low-voltage winding of the second three-winding transformer 16 through the second 10 kV circuit breaker 14 and the second 10 kV isolating switch 15. The delta side of the high-voltage winding of the second three-winding transformer 16 is successively connected through the fifth 220 kV isolating switch 17, the sixth 220 kV isolating switch 18, the second 220 kV circuit breaker 19, the seventh 220 kV isolating switch 20, the eighth 220 kV isolating switch 21, and the second 220 kV line 22. The delta side of the low-voltage winding of the second three-winding transformer 16 is connected through the second 6 kV switch 23 and the second 6 kV bus 24.

[0046] In this embodiment, it further includes a 6kV tie switch 25, a ninth 220kV isolating switch 26, a third 220kV circuit breaker 27, a tenth 220kV isolating switch 28, an eleventh 220kV isolating switch 29, a fourth 220kV circuit breaker 30, and a twelfth 220kV isolating switch 31. One end of the 6kV tie switch 25 is connected to the first 6kV busbar 12, and the other end is connected to the second 6kV busbar 24. After the ninth 220kV isolating switch 26, the third 220kV circuit breaker 27, and the tenth 220kV isolating switch 28 are connected in series, one end is connected to the common point where the first 220kV isolating switch 5 and the second 220kV isolating switch 6 are connected, and the other end is connected to the common point where the fifth 220kV isolating switch 17 and the sixth 220kV isolating switch 18 are connected. After the eleventh 220kV isolating switch 29, the fourth 220kV circuit breaker 30, and the twelfth 220kV isolating switch 31 are connected in series, one end is connected to the common point where the third 220kV isolating switch 8 and the fourth 220kV isolating switch 9 are connected, and the other end is connected to the common point where the seventh 220kV isolating switch 20 and the eighth 220kV isolating switch 21 are connected.

[0047] In this embodiment, the first 220kV isolating switch 5, the second 220kV isolating switch 6, the first 220kV circuit breaker 7, the third 220kV isolating switch 8, the fourth 220kV isolating switch 9, the fifth 220kV isolating switch 17, the sixth 220kV isolating switch 18, the second 220kV circuit breaker 19, the seventh 220kV isolating switch 20, the eighth 220kV isolating switch 21, the ninth 220kV isolating switch 26, the third 220kV circuit breaker 27, the tenth 220kV isolating switch 28, the eleventh 220kV isolating switch 29, the fourth 220kV circuit breaker 30, and the twelfth 220kV isolating switch 31 form an inner bridge and an outer bridge wiring.

[0048] In this embodiment, such as Figure 2As shown in the figure, before the black start of the first hydro-generator 1 with the first three-winding transformer 4 and the first 220 kV line 10, the first 10 kV isolating switch 3, the first 220 kV isolating switch 5, the second 220 kV isolating switch 6, the third 220 kV isolating switch 8, the fourth 220 kV isolating switch 9, the second 10 kV circuit breaker 14, the second 10 kV isolating switch 15, the fifth 220 kV isolating switch 17, the sixth 220 kV isolating switch 18, the second 220 kV circuit breaker 19, the seventh 220 kV isolating switch 20, the eighth 220 kV isolating switch 21, the second 6 kV switch 23, and the 6 kV tie switch 25 are all in the closed state, and the first 10 kV circuit breaker 2, the first 220 kV circuit breaker 7, the first 6 kV switch 11, the ninth 220 kV isolating switch 26, the third 220 kV circuit breaker 27, the tenth 220 kV isolating switch 28, the eleventh 220 kV isolating switch 29, the fourth 220 kV circuit breaker 30, and the twelfth 220 kV isolating switch 31 are all in the open state; the first hydro-generator 1, the first three-winding transformer 4, and the first 220 kV line 10 are in the power-off state, the second hydro-generator 13, the second three-winding transformer 16, the second 220 kV line 22, and the second 6 kV bus 24 are in the energized state, and the first 6 kV bus 12 is supplied with power through connection by the second 6 kV bus 24.

[0049] In this embodiment, when the first hydro-generator 1 resumes power supply to the first 6 kV bus 12, the first hydro-generator 1 builds up voltage to the rated voltage, the 6 kV tie switch 25 is in the open state, and the first 10 kV circuit breaker 2 and the first 6 kV switch 11 are in the closed state.

[0050] In this embodiment, as Figure 3 shown, when the first hydro-generator 1 resumes power supply to the first 6 kV bus 12, the first hydro-generator 1 uses the governor oil pressure system to self-energize and start up to the rated speed, and further builds up voltage at the machine terminal to the rated voltage. First, the 6 kV tie switch 25 is disconnected, and then the first 10 kV circuit breaker 2 and the first 6 kV switch 11 are closed to realize the operation of the first hydro-generator 1 with the first 6 kV bus 12 as the auxiliary power supply.

[0051] In this embodiment, as Figure 4 shown, when the first hydro-generator 1 charges the first three-winding transformer 4 and the first 220 kV line 10, the first 220 kV circuit breaker 7 is in the closed state, and the voltages at both ends of the first 220 kV line 10 are both the rated voltage.

[0052] In this embodiment, the rated voltage of the first hydrogenerator 1 and the second hydrogenerator 13 is 10.5 kV, and the rated voltages of the three sides of the first three-winding transformer 4 and the second three-winding transformer 16 are all 242 kV / 10.5 kV / 6.3 kV.

[0053] A black start method for a 220 kV voltage-class internal and external bridge connection hydropower station without a high-voltage auxiliary transformer according to the present invention includes the following steps:

[0054] 1) When the first hydrogenerator 1 drives the first three-winding transformer 4 and the first 220 kV line 10 for black start, check and confirm that the ninth 220 kV isolating switch 26, the third 220 kV circuit breaker 27, the tenth 220 kV isolating switch 28, the eleventh 220 kV isolating switch 29, and the fourth 220 kV circuit breaker 30 are all in the off state, and enter step 2);

[0055] 2) Disconnect the 6 kV tie switch 25. The first 6 kV bus 12 is in a power-off state. Check that the first hydrogenerator 1 is in a shutdown state, and the first three-winding transformer 4 and the first 220 kV line 10 are in a power-off state, and enter step 3);

[0056] 3) Close the first 10 kV isolating switch 3, the first 220 kV isolating switch 5, the second 220 kV isolating switch 6, the third 220 kV isolating switch 8, and the fourth 220 kV isolating switch 9 in sequence, and enter step 4);

[0057] 4) Use the oil pressure of the governor oil pressure system of the first hydrogenerator 1 to start the machine to the rated speed, operate the excitation system to build voltage of the first hydrogenerator 1 to the rated voltage, and close the first 10 kV circuit breaker 2, and enter step 5);

[0058] 5) Close the first 6 kV switch 11. The first 6 kV bus 12 resumes power supply, and enter step 6);

[0059] 6) Close the first 220 kV circuit breaker 7. The first hydrogenerator 1 charges the first 220 kV line 10, and enter step 7);

[0060] 7) Check that the voltage phase sequence on the local side and the opposite side of the first 220 kV line 10 is correct, and the indicated value is the rated voltage. The black start of the first hydrogenerator 1 driving the first three-winding transformer 4 and the first 220 kV line 10 is completed.

[0061] A black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level without a high-voltage auxiliary transformer according to the present invention includes a first hydro-generator, a first 10 kV circuit breaker, a first 10 kV isolating switch, a first three-winding transformer, a first 220 kV isolating switch, a second 220 kV isolating switch, a first 220 kV circuit breaker, a third 220 kV isolating switch, a fourth 220 kV isolating switch, a first 220 kV line, a first 6 kV switch and a first 6 kV busbar; the system uses the self-energy storage of the first hydro-generator through its own governor oil pressure system, opens the guide vanes and adjusts to the rated speed, operates the excitation system to build the terminal voltage to the rated voltage, closes the first 10 kV circuit breaker and the first 6 kV switch, makes full use of the characteristics of the first three-winding transformer, which acts as both a step-up transformer and a station service transformer, promptly restores the power supply of the first 6 kV busbar, realizes the stable operation of the first hydro-generator with its own station service load in an island, then closes the first 220 kV circuit breaker, and sends the power supply of the first hydro-generator to the first 220 kV line for the first time to assist the superior substation in restoring power supply, ensure the normal operation of the grid load, and reduce the power outage loss; the system does not set up a special high-voltage auxiliary transformer, directly uses the three-winding transformer as the main transformer and the station service transformer, simplifies the primary system wiring, reduces the operation steps for restoring the station service power during black start, and at the same time reduces the investment in primary equipment, and realizes quickly sending out the power supply during black start.

[0062] The above are only the preferred embodiments of the present invention patent, and do not impose any limitations on the present invention patent. Any simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level and without a high-voltage auxiliary transformer, characterized in that, it includes a first hydro-generator (1), a first three-winding transformer (4), a first 220 kV line (10) and a first 6 kV busbar (12); The first hydro-generator (1) is sequentially connected to the star side of the low-voltage winding of the first three-winding transformer (4) via a first 10 kV circuit breaker (2), a first 10 kV isolating switch (3); The delta side of the high-voltage winding of the first three-winding transformer (4) is sequentially connected to the first 220 kV line (10) via a first 220 kV isolating switch (5), a second 220 kV isolating switch (6), a first 220 kV circuit breaker (7), a third 220 kV isolating switch (8), a fourth 220 kV isolating switch (9); The delta side of the low-voltage winding of the first three-winding transformer (4) is connected to the first 6 kV busbar (12) via a first 6 kV switch (11).

2. The black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level and without a high-voltage auxiliary transformer according to claim 1, characterized in that, it further includes a second hydro-generator (13), a second 220 kV line (22) and a second 6 kV busbar (24); The second hydro-generator (13) is connected to the star side of the low-voltage winding of the second three-winding transformer (16) via a second 10 kV circuit breaker (14), a second 10 kV isolating switch (15); The delta side of the high-voltage winding of the second three-winding transformer (16) is sequentially connected to the second 220 kV line (22) via a fifth 220 kV isolating switch (17), a sixth 220 kV isolating switch (18), a second 220 kV circuit breaker (19), a seventh 220 kV isolating switch (20), an eighth 220 kV isolating switch (21); The delta side of the low-voltage winding of the second three-winding transformer (16) is connected to the second 6 kV busbar (24) via a second 6 kV switch (23).

3. The black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level and without a high-voltage auxiliary transformer according to claim 2, characterized in that, it further includes a 6 kV tie switch (25), a ninth 220 kV isolating switch (26), a third 220 kV circuit breaker (27), a tenth 220 kV isolating switch (28), an eleventh 220 kV isolating switch (29), a fourth 220 kV circuit breaker (30) and a twelfth 220 kV isolating switch (31); One end of the 6 kV tie switch (25) is connected to the first 6 kV busbar (12), and the other end is connected to the second 6 kV busbar (24); The ninth 220 kV isolating switch (26), the third 220 kV circuit breaker (27), and the tenth 220 kV isolating switch (28) are connected in series. One end of the ninth 220 kV isolating switch (26) is connected to the common point where the first 220 kV isolating switch (5) and the second 220 kV isolating switch (6) are connected. One end of the tenth 220 kV isolating switch (28) is connected to the common point where the fifth 220 kV isolating switch (17) and the sixth 220 kV isolating switch (18) are connected; The eleventh 220 kV isolating switch (29), the fourth 220 kV circuit breaker (30), and the twelfth 220 kV isolating switch (31) are connected in series. One end of the eleventh 220 kV isolating switch (29) is connected to the common point where the third 220 kV isolating switch (8) and the fourth 220 kV isolating switch (9) are connected. One end of the twelfth 220 kV isolating switch (31) is connected to the common point where the seventh 220 kV isolating switch (20) and the eighth 220 kV isolating switch (21) are connected.

4. A black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level without a high-voltage auxiliary transformer according to claim 3, characterized in that, Before the first hydro-generator (1) drives the first three-winding transformer (4) and the first 220 kV line (10) for black start, the first 10 kV isolating switch (3), the first 220 kV isolating switch (5), the second 220 kV isolating switch (6), the third 220 kV isolating switch (8), the fourth 220 kV isolating switch (9), the second 10 kV circuit breaker (14), the second 10 kV isolating switch (15), the fifth 220 kV isolating switch (17), the sixth 220 kV isolating switch (18), the second 220 kV circuit breaker (19), the seventh 220 kV isolating switch (20), the eighth 220 kV isolating switch (21), the second 6 kV switch (23), and the 6 kV tie switch (25) are all in the closed state, and the first 10 kV circuit breaker (2), the first 220 kV circuit breaker (7), the first 6 kV switch (11), the ninth 220 kV isolating switch (26), the third 220 kV circuit breaker (27), the tenth 220 kV isolating switch (28), the eleventh 220 kV isolating switch (29), the fourth 220 kV circuit breaker (30), and the twelfth 220 kV isolating switch (31) are all in the open state; the first hydro-generator (1), the first three-winding transformer (4), and the first 220 kV line (10) are in a power-off state, the second hydro-generator (13), the second three-winding transformer (16), the second 220 kV line (22), and the second 6 kV bus (24) are in a live state, and the first 6 kV bus (12) is supplied with power through connection by the second 6 kV bus (24).

5. A black start system for a hydropower station with an internal and external bridge connection at the 220 kV voltage level without a high-voltage auxiliary transformer according to claim 4, characterized in that, When the first hydrogenerator (1) resumes power supply to the first 6kV busbar (12), the first hydrogenerator (1) builds up voltage to the rated voltage. The 6kV tie switch (25) is in the open state, and the first 10kV circuit breaker (2) and the first 6kV switch (11) are in the closed state.

6. A black start system for a 220kV voltage level internal and external bridge connection hydropower station without a high-voltage auxiliary transformer according to claim 5, characterized in that, When the first hydrogenerator (1) resumes power supply to the first 6kV busbar (12), the first hydrogenerator (1) uses the governor oil pressure system to self-energize and start up to the rated speed, and further builds up voltage at the machine terminal to the rated voltage. First, the 6kV tie switch (25) is disconnected, and then the first 10kV circuit breaker (2) and the first 6kV switch (11) are closed to realize the operation of the first hydrogenerator (1) with the first 6kV busbar (12) as the auxiliary power supply.

7. A black start system for a 220kV voltage level internal and external bridge connection hydropower station without a high-voltage auxiliary transformer according to claim 5, characterized in that, When the first hydrogenerator (1) charges the first three-winding transformer (4) and the first 220kV line (10), the first 220kV circuit breaker (7) is in the closed state, and the voltages at both ends of the first 220kV line (10) are both the rated voltage.

8. A black start system for a 220kV voltage level internal and external bridge connection hydropower station without a high-voltage auxiliary transformer according to claim 1, characterized in that, The rated voltages of the first hydrogenerator (1) and the second hydrogenerator (13) are 10.5kV, and the rated voltages of the three sides of the first three-winding transformer (4) and the second three-winding transformer (16) are all 242kV / 10.5kV / 6.3kV.

9. A black start method for a 220kV voltage level internal and external bridge connection hydropower station without a high-voltage auxiliary transformer, characterized in that, Based on the system described in any one of claims 3-8, it includes the following steps: 1) When performing the black start of the first hydrogenerator (1) with the first three-winding transformer (4) and the first 220kV line (10), check and confirm that the ninth 220kV isolating switch (26), the third 220kV circuit breaker (27), the tenth 220kV isolating switch (28), the eleventh 220kV isolating switch (29), and the fourth 220kV circuit breaker (30) are all in the open state, and then enter step 2); 2) Disconnect the 6kV tie switch (25), and the first 6kV busbar (12) is in the power-off state. Check that the first hydrogenerator (1) is in the shutdown state, and the first three-winding transformer (4) and the first 220kV line (10) are in the power-off state, and then enter step 3); 3) Close the first 10kV isolating switch (3), the first 220kV isolating switch (5), the second 220kV isolating switch (6), the third 220kV isolating switch (8), and the fourth 220kV isolating switch (9) in sequence, and then enter step 4); 4) Start the first hydrogenerator (1) to the rated speed by using the oil pressure of the governor oil pressure system, operate the excitation system to build up the voltage of the first hydrogenerator (1) to the rated voltage, close the first 10 kV circuit breaker (2), and proceed to step 5); 5) Close the first 6 kV switch (11), restore the power supply of the first 6 kV busbar (12), and proceed to step 6); 6) Close the first 220 kV circuit breaker (7), charge the first 220 kV line (10) by the first hydrogenerator (1), and proceed to step 7); 7) Check that the voltage phase sequence on the local side and the opposite side of the first 220 kV line (10) is correct and the indicated value is the rated voltage, and the black start of the first hydrogenerator (1) with the first three-winding transformer (4) and the first 220 kV line (10) is completed.

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