A 220kV voltage level unit connection hydropower station self-storage black start system and method

Abstract

The present invention provides a self-storage black start system and method for a 220kV voltage level unit-connected hydropower station, comprising a hydro-generator, a high-voltage plant transformer, a first 400V low-voltage plant transformer, a second 400V low-voltage plant transformer, a flood gate diesel generator, a main transformer, and a 220kV line; the maximum allowable operating time after the speed regulator oil pressure system loses power is determined through testing. When the hydropower station loses power, the self-storage of the speed regulator oil pressure system is promptly used to open the guide vanes, adjust the water wheel to the rated speed, and the excitation system uses a DC excitation method to help the generator build up voltage to the rated voltage, further restore the plant power system, carry out a line charging test, and restore line power supply. If the generator fails to successfully build up voltage within the maximum allowable operating time after the speed regulator oil pressure system loses power, before the allowed time arrives, the diesel generator is quickly started to restore the plant power system and assist the unit in performing a black start; the power supply of the unit-connected hydropower station is quickly sent out to help the power grid restore power supply.

Description

Technical Field

[0001] The present invention belongs to the technical field of black start of hydropower stations, and in particular relates to a self-storage black start system and method for a 220kV voltage level unit-connected hydropower station. Background Art

[0002] The "black start" of hydropower units is one of the four major auxiliary services of the power grid (frequency regulation, standby, peak shaving, and black start). Power plants with black start capabilities will receive annual compensation for grid ancillary services. A "black start" occurs when a complete power outage occurs due to force majeure factors such as power grid failures, natural disasters, and war. In this situation, the hydropower station leverages its fast startup characteristics to provide the necessary plant power for startup. The hydropower unit starts at a constant speed, loads the excitation stator to build up to the rated voltage, and enters stable FCB operation mode. The voltage is then boosted by the main transformer and transmitted via transmission lines to the opposite substation, providing plant power for the generator set on the opposite side to start, achieving a spark that will spread rapidly and restore power to the grid system. The currently known black start technology has the following problems: (1) When the turbine unit is started by using the self-storage of the speed regulator oil pressure system, the maximum allowable time of the speed regulator oil pressure system is not measured when the turbine unit is without factory power supply, which poses a safety hazard to the black start of the turbine unit; (2) Self-storage and diesel generators have not yet been combined for black start; (3) There is currently no black start technology for hydropower stations related to the wiring of the generator and transformer units. Summary of the Invention

[0003] In response to the problems existing in the prior art, the present invention provides a self-storage black start system and method for a 220kV voltage level unit-connected hydropower station. In the event of a power outage on the transmission line, the system can safely, quickly and reliably transmit the power supply of the unit-connected hydropower station, thereby helping the power grid to resume power supply.

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

[0005] A 220kV voltage level unit connection hydropower station self-storage black start system, comprising a turbine generator, a 10kV plant busbar, a first 400V self-use busbar, a second 400V self-use busbar, a 400V self-use interconnecting switch, a 20kV knife switch, and a 220kV line;

[0006] One end of the hydro-generator is connected to the ground, and the generating end is connected to the 10kV plant busbar via a high-voltage plant transformer and a 10kV incoming line switch in sequence;

[0007] The second 400V private power bus is connected to the 10kV auxiliary power bus in sequence via the 400V private power contact switch, the first 400V private power bus, the first 400V private power switch, the first 400V low-voltage auxiliary power transformer, and the first 10kV feeder switch;

[0008] One end of the 20kV knife switch is connected to the common point where the hydro-generator and the high-voltage plant transformer are connected, and the other end is connected to the 220kV line via the main transformer, the grid-connected switch, and the 220kV knife switch in sequence.

[0009] Preferably, it also includes a flood discharge gate diesel generator and an interconnected 400V power switch;

[0010] The floodgate diesel generator is connected to the 10kV plant busbar via a 400V outlet switch, a second 400V low-voltage plant transformer, a 10kV knife switch, and a second 10kV feeder switch in sequence;

[0011] The interconnected 400V power switch is connected to the second 400V self-use bus;

[0012] The brake switch uses electromagnetic induction to generate electromagnetic force to brake the hydro-generator. One end of the brake switch is connected to the common point connected to the hydro-generator and the 20kV knife switch, and the other end short-circuits the three phases A, B, and C.

[0013] Furthermore, when determining the maximum allowable operating time of the hydraulic generator oil pressure system after power failure, the grid-connected switch, 10kV incoming line switch, first 10kV feeder switch, second 10kV feeder switch and interconnected 400V power switch are all in the disconnected state, used to cut off the working power supply of the oil pump of the hydraulic generator oil pressure system.

[0014] Furthermore, before the hydro-generator performs self-energy storage black start, the brake switch, grid-connected switch, 220kV knife switch, and second 10kV feeder switch are all in the disconnected state, and the neutral point grounding knife switch, 20kV knife switch, 10kV incoming line switch, first 10kV feeder switch, first 400V self-use power switch, 400V self-use power interconnection switch, and 10kV knife switch are all in the closed state.

[0015] Furthermore, before the hydro-generator with main transformer charges the 220kV line, the 20kV knife switch, grid-connected switch and 220kV knife switch are all in a closed state.

[0016] Furthermore, when the hydro-generator fails to start successfully within the Tmax time, and the first 400V self-use busbar and the second 400V self-use busbar fail to resume power supply within Tmax, that is, after Tmax is reached, the 10kV incoming line switch and the grid-connected switch are immediately disconnected, the 400V output switch and the second 10kV feeder switch are closed, and the voltage at the end of the flood discharge gate diesel generator is adjusted to the rated voltage. The first 400V self-use busbar and the second 400V self-use busbar are restored to be powered by the flood discharge gate diesel generator, the guide vanes of the hydro-generator are opened, the hydro-generator is adjusted to the rated speed of 136.4r / min, the voltage of the hydro-generator is built to the rated voltage, the hydro-generator with the main transformer is started again to charge the 220kV line, and the grid-connected switch is closed.

[0017] A self-storage black start method for a 220 kV voltage level unit-connected hydropower station comprises the following steps:

[0018] 1) Adjust the 220kV line and main transformer to cold standby state, close the neutral point grounding switch and 20kV switch, and proceed to step 2);

[0019] 2) Check that the 10kV auxiliary busbar is in a voltage-free state, disconnect the 400V outlet switch, the second 10kV feeder switch, and the 10kV incoming line switch, close the first 10kV feeder switch, the first 400V self-use switch, and the 400V self-use interconnecting switch, and proceed to step 3);

[0020] 3) Manually start the water turbine generator to supply water, start timing, and proceed to step 4);

[0021] 4) Adjust the speed of the hydro-generator to 136.4 r / min and the voltage to 100% of the rated voltage, and determine whether the timing time is ≤ the maximum allowable operating time of the self-storage black start (Tmax). If the timing requirement is met, close the 10 kV incoming line switch, and measure the first 400 V self-use busbar and the second 400 V self-use busbar to see that the rated voltage is 400 V. If the timing requirement is not met, immediately open the 10 kV incoming line switch, start the flood gate diesel generator to no load, and power the first 400 V self-use busbar and the second 400 V self-use busbar by the flood gate diesel generator; and proceed to step 5)

[0022] 5) The working power supply of the oil pump of the hydraulic system of the hydro-generator is restored, the 220kV line and the main transformer are operated to be in hot standby mode, the grid-connected switch is closed, and the process proceeds to step 6);

[0023] 6) Check and confirm that the voltage and phase sequence on the opposite side of the 220 kV line are correct, and proceed to step 7);

[0024] 7) The 220kV line and main transformer are switched to cold standby mode, the first 400V self-use power switch is disconnected, the interconnected 400V power switch is closed, the hydro-generator is shut down, and the second 10kV feeder switch and 400V outlet switch are disconnected.

[0025] Furthermore, the voltage of the hydro-generator in step 4) is 18kV; the flood discharge gate diesel generator is started to no-load, the no-load voltage of the flood discharge gate diesel generator is Uab=400V, Ubc=401V, Uca=401V, the frequency f=50.3Hz, the second 10kV feeder switch and the 400V export switch are closed, the 10kV plant bus phase voltage is Ua=5.9kV, Ub=6.0kV, Uc=5.9kV, the first 400V self-use bus voltage is Uab=400.42V, Ubc=400.65V, Uca=400.11V, the second 400V self-use bus voltage is Uab=400.42V, Ubc=400.59V, Uca=400.26V.

[0026] Compared with the prior art, the present invention has the following beneficial technical effects:

[0027] The present invention determines the maximum permissible operating time of the governor oil pressure system after a power outage through testing. When the hydropower station loses power, the governor oil pressure system's self-storage energy is promptly utilized to open the guide vanes, adjusting the turbine to the rated speed. The excitation system uses a DC excitation method to help the generator build voltage to the rated voltage, further restoring the plant power system, conducting line charging tests, and restoring line power. If the generator fails to successfully build voltage within the maximum permissible operating time after the governor oil pressure system loses power, the diesel generator is quickly started before the permitted time expires, restoring the plant power system and assisting the unit in a black start.

[0028] Furthermore, the present invention carries out a test on the maximum allowable operating time after the speed regulator oil pressure system loses power, predicts in advance the longest time that the equipment can withstand, takes safety measures, increases the success rate of black start, and ensures the safety of the host equipment.

[0029] Furthermore, if the hydraulic generator of the present invention fails to build pressure within the maximum allowable operating time, the diesel generator is started in time to ensure the safety of power supply in the factory. The diesel generator serves as a backup for the self-energy storage method to ensure that the black operation can proceed smoothly.

[0030] Furthermore, the hydro-generator, main transformer and 220kV line of the present invention adopt unit wiring, which has fewer devices and simple structure, is easy to operate during black start, can quickly deliver power, and has low construction cost.

[0031] Furthermore, the present invention uses electromagnetic induction of a brake switch to generate electromagnetic force to stop the hydro-generator, and in the event of loss of control, the hydro-generator can be quickly stopped in a short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the black start principle of the present invention.

[0033] Figure 2 This is a schematic diagram of the principle before black start of the present invention.

[0034] Figure 3 This is a schematic diagram of the circuit charging principle of the present invention.

[0035] Figure 4 This is a black start principle diagram when the self-storage energy of the present invention cannot start.

[0036] In the figure: 1-neutral point grounding switch; 2-hydrogenerator; 3-brake switch; 4-high-voltage auxiliary transformer; 5-10kV incoming line switch; 6-10kV auxiliary busbar; 7-first 10kV feeder switch; 8-first 400V low-voltage auxiliary transformer; 9-first 400V private power switch; 10-first 400V private power busbar; 11-second 400V private power busbar; 12-400V private power interconnecting switch; 13-20kV switch; 14-main transformer; 15-grid-connected switch; 16-220kV switch; 17-220kV line; 18-flood discharge gate diesel generator; 19-400V outlet switch; 20-second 400V low-voltage auxiliary transformer; 21-10kV switch; 22-second 10kV feeder switch; 23-interconnected 400V power switch. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0038] The present invention provides a self-storage black start system and method for a 220kV voltage level unit-connected hydropower station, comprising a hydro-turbine generator, a high-voltage plant transformer, a first 400V low-voltage plant transformer, a second 400V low-voltage plant transformer, a flood gate diesel generator, a main transformer, and a 220kV line. The present invention determines the maximum allowable operating time after the speed regulator oil pressure system loses power through experiments. When the hydropower station loses power, the self-storage of the speed regulator oil pressure system is promptly used to open the guide vanes, adjust the water wheel to the rated speed, and the excitation system uses a DC excitation method to help the generator build up voltage to the rated voltage, further restore the plant power system, carry out a line charging test, and restore line power supply. If the generator fails to successfully build up voltage within the maximum allowable operating time after the speed regulator oil pressure system loses power, before the allowed time arrives, the diesel generator is quickly started to restore the plant power system and assist the unit in black starting. The present invention can safely, quickly, and reliably send out power from the unit-connected hydropower station, helping the power grid to restore power supply.

[0039] like Figure 1 As shown, a 220kV voltage level unit connection hydropower station self-storage black start system includes a turbine generator 2, a 10kV plant bus 6, a first 400V self-use bus 10, a second 400V self-use bus 11, a 400V self-use interconnecting switch 12, a 20kV knife switch 13, and a 220kV line 17;

[0040] One end of the hydro-generator 2 is connected to the ground, and the generating end is connected to the 10kV plant bus 6 via the high-voltage plant transformer 4 and the 10kV incoming line switch 5 in sequence;

[0041] The second 400V private power bus 11 is connected to the 10kV utility bus 6 via the 400V private power contact switch 12, the first 400V private power bus 10, the first 400V private power switch 9, the first 400V low-voltage utility transformer 8, and the first 10kV feeder switch 7 in sequence;

[0042] One end T of the 20kV knife switch 13 is connected to the common point where the hydro-generator 2 and the high-voltage plant transformer 4 are connected, and the other end is connected to the 220kV line 17 via the main transformer 14, the grid-connected switch 15, and the 220kV knife switch 16 in sequence.

[0043] In this embodiment, the specific parameters of the hydro-generator 2 are as follows:

[0044]

[0045]

[0046] In this embodiment, the specific parameters of the 220kV line 17 are as follows:

[0047]

[0048] In this embodiment, the specific parameters of the main transformer are as follows:

[0049] model SFP8-380000 / 220 Rated capacity 380MVA Rated voltage 236kV±2×2.5% / 18kV Rated frequency 50Hz Rated current 929.9 / 12188.5A Connection Group Yn,d11 Manufacturer Xi'an Transformer Factory Impedance voltage 16.5％ No-load current 0.2％ No-load loss 163.75kW

[0050] In this embodiment, the specific parameters of the high-voltage plant transformer 4 are as follows:

[0051]

[0052] In this embodiment, a flood gate diesel generator 18 and an interconnected 400V power switch 23 are also included;

[0053] The floodgate diesel generator 18 is connected to the 10kV plant bus 6 via a 400V outlet switch 19, a second 400V low-voltage plant transformer 20, a 10kV knife switch 21, and a second 10kV feeder switch 22 in sequence;

[0054] The interconnected 400V power switch 23 is connected to the second 400V self-use bus 11;

[0055] The brake switch 3 uses electromagnetic induction to generate electromagnetic force to brake the hydro-generator 2. One end of the brake switch 3 is connected to the common point connected to the hydro-generator 2 and the 20kV knife switch 13, and the other end short-circuits the three phases A, B, and C. The brake switch 3 is in a closed state only when the hydro-generator 2 needs to be braked.

[0056] In this embodiment, the specific parameters of the floodgate diesel generator 18 are as follows:

[0057]

[0058]

[0059] In this embodiment, when determining the maximum allowable operating time of the hydraulic generator oil pressure system after power failure, the grid-connected switch 15, the 10kV incoming line switch 5, the first 10kV feeder switch 7, the second 10kV feeder switch 22 and the interconnected 400V power switch 23 are all in the disconnected state, which is used to cut off the working power supply of the oil pump of the hydraulic system of the hydraulic generator 2, record the hydraulic system pressure Pbt before the test, turn on the hydraulic generator 2, adjust the speed to the rated speed of 136.4r / min, and record the hydraulic system pressure of the hydraulic generator 2 dropping to The time Te of the minimum operating oil pressure Pmin, the oil pressure drop speed of the oil pressure system of the hydro-generator 2 is calculated as V = (Pbt-Pmin) / Te, before the self-storage black start of the hydro-generator 2 is performed, the maximum allowable operating time of the self-storage black start is predicted to be Tmax = (Pzcn-Pmin) / V according to the oil pressure system pressure Pzcn, that is, the hydro-generator 2 must be successfully started within the Tmax time, and the first 400V self-use electric bus 10 and the second 400V self-use electric bus 11 must resume power supply within Tmax.

[0060] In this embodiment, the hydraulic generator oil pressure system is adjusted to a rated oil pressure of 3.95 MPa, and is started up to a no-load constant speed of 136.4 r / min. After running for 22 minutes, the oil pressure of the hydraulic system is close to the minimum operating oil pressure of 3.2 MPa, and the oil pressure drop rate is 0.021 MPa / min.

[0061] like Figure 2 As shown, before the hydro-generator 2 performs self-energy storage black start, the brake switch 3, the grid-connected switch 15, the 220kV switch 16, and the second 10kV feeder switch 22 are all in the disconnected state, the neutral point grounding switch 1, the 20kV switch 13, the 10kV incoming line switch 5, the first 10kV feeder switch 7, the first 400V self-use switch 9, the 400V self-use contact switch 12, and the 10kV switch 21 are all in the closed state, the rated speed of the hydro-generator 2 is adjusted to 136.4r / min, the voltage of the hydro-generator 2 is built up to the rated voltage using a DC excitation method, the power supply of the first 400V self-use bus 10 and the second 400V self-use bus 11 is restored, the working power supply of the oil pump of the oil pressure system of the hydro-generator 2 is restored, and the oil pressure system of the hydro-generator 2 is adjusted to the rated oil pressure.

[0062] like Figure 3 As shown, before the hydro-generator 2 with the main transformer 14 charges the 220kV line 17, the 20kV knife switch 13, the grid-connected switch 15 and the 220kV knife switch 16 are all in a closed state, the end voltage of the hydro-generator 2 is 100% of the rated voltage, and the voltage on the opposite side of the 220kV line 17 is checked and confirmed to be the rated voltage.

[0063] like Figure 4 As shown, the hydro-generator 2 fails to start successfully within the Tmax time, and the first 400V self-use bus 10 and the second 400V self-use bus 11 fail to resume power supply within Tmax, that is, after the Tmax is reached, the 10kV incoming line switch 5 and the grid-connected switch 15 are immediately disconnected, the 400V outlet switch 19 and the second 10kV feeder switch 22 are closed, the voltage at the end of the flood discharge gate diesel generator 18 is adjusted to the rated voltage, the first 400V self-use bus 10 and the second 400V self-use bus 11 are restored to be powered by the flood discharge gate diesel generator 18, the guide vanes of the hydro-generator 2 are opened, the rated speed of the hydro-generator 2 is adjusted to 136.4r / min, the voltage of the hydro-generator 2 is built to the rated voltage, the hydro-generator 2 with the main transformer 14 is charged to the 220kV line 17 again, and the grid-connected switch 15 is closed.

[0064] A self-storage black start method for a 220 kV voltage level unit-connected hydropower station comprises the following steps:

[0065] 1) Adjust the 220kV line 17 and the main transformer 14 to a cold standby state, close the neutral point grounding switch 1 and the 20kV switch 13, and proceed to step 2);

[0066] 2) Checking that the 10kV auxiliary busbar 6 is in a no-voltage state, disconnecting the 400V outlet switch 19, the second 10kV feeder switch 22, and the 10kV incoming line switch 5, and closing the first 10kV feeder switch 7, the first 400V self-use switch 9, and the 400V self-use interconnecting switch 12, and proceeding to step 3);

[0067] 3) Manually start the water supply of the hydro-generator 2, start the timer, and proceed to step 4);

[0068] 4) Adjust the speed of the hydro-generator 2 to 136.4 r / min and the voltage to 100% of the rated voltage, and determine whether the timing time is ≤ the maximum allowable self-storage black start operating time Tmax. If the timing requirement is met, close the 10 kV incoming line switch 5, and measure the first 400 V self-use bus 10 and the second 400 V self-use bus 11 to find that the rated voltage is 400 V. If the timing requirement is not met, immediately open the 10 kV incoming line switch 5, start the flood gate diesel generator 18 to no load, and power the first 400 V self-use bus 10 and the second 400 V self-use bus 11 with power from the flood gate diesel generator 18; and proceed to step 5).

[0069] 5) The working power supply of the oil pump of the hydraulic system of the hydro-generator 2 is restored, the 220kV line 17 and the main transformer 14 are operated to be hot standby, the grid-connected switch 15 is closed, and the process proceeds to step 6);

[0070] 6) Check and confirm that the voltage and phase sequence on the opposite side of the 220 kV line 17 are correct, and proceed to step 7);

[0071] 7) The 220kV line 17 and main transformer 14 are switched to cold standby mode, the first 400V self-use power switch 9 is disconnected, the interconnected 400V power switch 23 is closed, the hydro-generator 2 is shut down, and the second 10kV feeder switch 22 and 400V outlet switch 19 are disconnected).

[0072] In this embodiment, the voltage of the hydro-generator 2 in the step 4) is 18kV; the flood discharge gate diesel generator 18 is started to no-load, the no-load voltage of the flood discharge gate diesel generator 18 is Uab=400V, Ubc=401V, Uca=401V, the frequency f=50.3Hz, the second 10kV feeder switch 22 and the 400V outlet switch 19 are closed, the 6-phase voltage of the 10kV plant bus is Ua=5.9kV, Ub=6.0kV, Uc=5.9kV, the voltage of the first 400V self-use bus 10 is Uab=400.42V, Ubc=400.65V, Uca=400.11V, and the voltage of the second 400V self-use bus 11 is Uab=400.42V, Ubc=400.59V, Uca=400.26V.

[0073] The above description is only a preferred embodiment of the present invention and does not limit the present invention. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A 220kV voltage level unit connection hydropower station self-storage black start system, characterized by: It includes a hydro-generator (2), a 10 kV plant busbar (6), a first 400 V self-use busbar (10), a second 400 V self-use busbar (11), a 400 V self-use interconnecting switch (12), a 20 kV knife switch (13), and a 220 kV line (17); One end of the hydro-generator (2) is connected to the ground, and the generating end is connected to the 10kV plant busbar (6) via a high-voltage plant transformer (4) and a 10kV incoming line switch (5) in sequence; The second 400V self-use busbar (11) is connected to the 10kV plant busbar (6) in sequence via the 400V self-use connecting switch (12), the first 400V self-use busbar (10), the first 400V self-use switch (9), the first 400V low-voltage plant transformer (8), and the first 10kV feeder switch (7); One end of the 20kV knife switch (13) is connected to the common point where the hydro-generator (2) and the high-voltage plant transformer (4) are connected, and the other end is connected to the 220kV line (17) via the main transformer (14), the grid-connected switch (15), and the 220kV knife switch (16) in sequence; Also included is a floodgate diesel generator (18), and an interconnecting 400V power switch (23); The floodgate diesel generator (18) is connected to the 10kV plant busbar (6) in sequence via a 400V outlet switch (19), a second 400V low-voltage plant transformer (20), a 10kV knife switch (21), and a second 10kV feeder switch (22); The interconnected 400V power switch (23) is connected to the second 400V self-use electric bus (11); The brake switch (3) utilizes electromagnetic induction to generate electromagnetic force to brake the hydro-generator (2), one end of which is connected to a common point connected to the hydro-generator (2) and the 20kV knife switch (13), and the other end short-circuits the three phases A, B, and C; When determining the maximum permissible operating time of the hydraulic system of the hydro-generator (2) after power failure, the grid-connected switch (15), the 10kV incoming line switch (5), the first 10kV feeder switch (7), the second 10kV feeder switch (22) and the interconnected 400V power switch (23) are all in an off state, for cutting off the working power supply of the oil pump of the hydraulic system of the hydro-generator (2); When the hydro-generator (2) fails to start successfully within the Tmax time, and the first 400V self-use busbar (10) and the second 400V self-use busbar (11) fail to resume power supply within the Tmax, that is, after the Tmax is reached, the 10kV incoming line switch (5) and the grid-connected switch (15) are immediately disconnected, the 400V outlet switch (19) and the second 10kV feeder switch (22) are closed, the voltage at the end of the flood discharge gate diesel generator (18) is adjusted to the rated voltage, the first 400V self-use busbar (10) and the second 400V self-use busbar (11) are restored to be powered by the flood discharge gate diesel generator (18), the guide vanes of the hydro-generator (2) are opened, the rated speed of the hydro-generator (2) is adjusted to 136.4r / min, the voltage of the hydro-generator (2) is built up to the rated voltage, the hydro-generator (2) with the main transformer (14) is again started to charge the 220kV line (17), and the grid-connected switch (15) is closed; Before the hydro-generator (2) performs a self-storage black start, the brake switch (3), the grid-connected switch (15), the 220kV knife switch (16), and the second 10kV feeder switch (22) are all in an open state, and the neutral point grounding knife switch (1), the 20kV knife switch (13), the 10kV incoming line switch (5), the first 10kV feeder switch (7), the first 400V self-use power switch (9), the 400V self-use power contact switch (12), and the 10kV knife switch (21) are all in a closed state; Before the hydro-generator (2) with the main transformer (14) charges the 220kV line (17), the 20kV knife switch (13), the grid-connected switch (15) and the 220kV knife switch (16) are all in a closed state.

2. A self-storage black start method for a 220kV voltage level unit connection hydropower station, characterized in that: The steps include: 1) Adjust the 220kV line (17) and the main transformer (14) to the cold standby state, close the neutral point grounding switch (1) and the 20kV switch (13), and proceed to step 2); 2) Check that the 10kV plant busbar (6) is in a no-voltage state, disconnect the 400V outlet switch (19), the second 10kV feeder switch (22) and the 10kV incoming line switch (5), close the first 10kV feeder switch (7), the first 400V self-use switch (9), and the 400V self-use interconnection switch (12), and proceed to step 3); 3) Manually start the hydro-generator (2) to supply water, start the timer, and proceed to step 4); 4) Adjust the speed of the hydro-generator (2) to 136.4 r / min and the voltage to 100% of the rated voltage, and judge whether the timing time is ≤ the maximum allowable operating time of the self-storage black start is Tmax. If the time requirement is met, close the 10kV incoming line switch (5), measure the first 400V self-use busbar (10) and the second 400V self-use busbar (11) to be the rated voltage of 400V; if the time requirement is not met, immediately disconnect the 10kV incoming line switch (5), start the flood gate diesel generator (18) to no load, and the first 400V self-use busbar (10) and the second 400V self-use busbar (11) are powered by the flood gate diesel generator (18); and enter step 5) 5) The working power supply of the oil pump of the hydraulic system of the hydro-generator (2) is restored, the 220 kV line (17) and the main transformer (14) are operated to switch to hot standby, the grid-connected switch (15) is closed, and the process proceeds to step 6); 6) Check and confirm that the voltage and phase sequence on the opposite side of the 220kV line (17) are correct, and proceed to step 7); 7) The 220kV line (17) and the main transformer (14) are switched to a cold standby state, the first 400V self-use switch (9) is disconnected, the interconnected 400V power switch (23) is closed, the hydro-generator (2) is shut down, and the second 10kV feeder switch (22) and the 400V outlet switch (19) are disconnected; In the step 4), the voltage of the hydro-generator (2) is 18 kV; the flood gate diesel generator (18) is started to no-load, the no-load voltage of the flood gate diesel generator (18) is Uab=400 V, Ubc=401 V, Uca=401 V, the frequency f=50.3 Hz, the second 10 kV feeder switch (22) and the 400 V outlet switch (19) are closed, the phase voltage of the 10 kV plant bus (6) is Ua=5.9 kV, Ub=6.0 kV, Uc=5.9 kV, the voltage of the first 400 V self-use bus (10) is Uab=400.42 V, Ubc=400.65 V, Uca=400.11 V, the voltage of the second 400 V self-use bus (11) is Uab=400.42 V, Ubc=400.59 V, Uca=400.26 V.

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