Large-scale water-turbine generator set stator single-phase grounding and arc suppression coil gear shifting test method

Abstract

A stator single-phase grounding and arc suppression coil gear shifting test method for a large water-turbine generator set comprises the following steps: when a neutral point of a generator is not grounded, the generator set operates normally, and the displacement voltage and waveform of the neutral point at the moment are measured; when the neutral point of the generator is not grounded, measuring a grounding current effective value and a current waveform when the three phases are grounded in a single-phase manner; when the neutral point of the generator is grounded through 1-17 gears of an arc suppression coil, measuring the effective value and waveform of single-phase grounding current and the displacement voltage and waveform of the neutral point; when the neutral point of the generator is grounded through the normal operation gear of the arc suppression coil, the displacement voltage and waveform of the neutral point at the moment are measured. The invention provides a large-scale water-turbine generator set stator single-phase grounding and arc suppression coil gear shifting test method, and solves the problem of insufficient accuracy of an existing large-scale water-turbine generator set stator single-phase grounding and arc suppression coil gear shifting experience method. And the problem that the harmonic component of the generator set cannot be measured by the existing large-scale water-turbine generator set stator single-phase grounding and arc suppression coil gear shifting empirical method is solved.

Description

Technical Field

[0001] The invention relates to the technical field of generator detection, in particular to a large-scale hydro-generator set stator single-phase grounding and arc suppression coil gear adjustment test method. Background Art

[0002] The stator single-phase grounding fault is the most common fault among all grounding forms of large hydro-turbine generator sets. This fault will cause the neutral point voltage of the generator to shift and a large grounding current to be generated at the grounding point. If effective measures are not taken, the single-phase grounding current may burn the stator core and wire rods, and excessive neutral point voltage shift may also cause the unit to shut down due to accidents.

[0003] The neutral point of the hydro-turbine generator is grounded through the arc suppression coil, which can effectively reduce the stator single-phase grounding fault current, but at the same time, the arc suppression coil's access system will also cause the neutral point displacement voltage to increase. Therefore, it can be understood as a variable that increases while the other increases. Therefore, a test method that can comprehensively measure various parameters during the single-phase grounding of the stator of a large hydro-turbine generator set and the arc suppression coil gear adjustment test is designed, which is of great value for the correct selection of the arc suppression coil and the normal operation of the unit.

[0004] The traditional test method has the following shortcomings: 1. The influence of the harmonic component in the single-phase fault current of the generator stator on the selection of the arc suppression coil position is not considered; 2. The relationship between the voltage offset of the generator neutral point and the gear selection of the arc suppression coil was not measured; 3. The specific relationship curve between the generator neutral point displacement voltage, single-phase grounding current and arc suppression coil gear selection has not been obtained. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a test method for single-phase grounding and arc suppression coil gear adjustment of the stator of a large-scale hydro-turbine generator set, which solves the problem that the existing empirical method for single-phase grounding and arc suppression coil gear adjustment of the stator of a large-scale hydro-turbine generator set is insufficiently accurate, and the problem that the existing empirical method for single-phase grounding and arc suppression coil gear adjustment of the stator of a large-scale hydro-turbine generator set cannot measure the harmonic components of the generator set.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a large-scale hydro-generator stator single-phase grounding and arc suppression coil gear adjustment test method, When the neutral point of the generator is not grounded, the unit operates normally and the neutral point displacement voltage and waveform are measured; When the neutral point of the generator is not grounded, measure the effective value of the grounding current and the current waveform when the three phases are grounded separately; When the neutral point of the generator is grounded through the arc suppression coil 1-17, measure the effective value and waveform of the single-phase grounding current, and the neutral point displacement voltage and waveform; When the neutral point of the generator is grounded through the arc suppression coil in the normal operating position, measure the neutral point displacement voltage and waveform at this time.

[0007] Preferably, when the neutral point of the generator is not grounded, the unit operates normally, and the steps for measuring the neutral point displacement voltage and waveform at this time are as follows: (1) Start the unit and maintain the rated speed of the generator; (2) Pull open the neutral point switch and arc suppression coil, and close the demagnetization switch; the generator stops when the voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase; (3) Measure the neutral point displacement voltage and waveform to obtain the waveform components of the generator neutral point voltage.

[0008] Preferably, when the neutral point of the generator is not grounded, the steps of measuring the effective value of the grounding current and the current waveform when the three phases are grounded in a single phase are as follows: (1) Start the unit and maintain the rated speed of the generator; (2) Pull open the neutral point switch and arc suppression coil, and close the demagnetization switch; stop when the generator voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase, and measure the grounding current IcA of phase A and the neutral point-to-ground voltage UN1; (3) Use a portable electrical quantity recorder and analyzer to read and record the current waveform when phase A is single-phase grounded; (4) Reduce the excitation current to zero, open the demagnetization switch, stop the machine, change the single-phase grounding point to phases B and C, and repeat steps (1) to (3).

[0009] Preferably, when the neutral point of the generator is grounded through the arc suppression coil 1-17, the steps of measuring the effective value and waveform of the single-phase grounding current, the neutral point displacement voltage and waveform are as follows: (1) The arc extinguishing coil is put into operation and the gear is set according to the test method; (2) Start the unit and maintain the rated speed of the generator.

[0010] (3) Close the demagnetization switch; stop when the generator voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase, and measure the grounding point current Ic, the neutral point voltage to ground UN, and the inductor current IL; (4) Use a portable electrical quantity recorder to read and record the single-phase grounding current waveform, and use a fault recording device to record the neutral point voltage waveform; (5) Reduce the excitation current to zero, pull open the demagnetization switch, stop the machine, shift the arc extinguishing coil, and repeat steps (1) to (4) until all gears required by the test method are tested.

[0011] Preferably, when the neutral point of the generator is grounded through the arc suppression coil in the normal operation gear, the steps of measuring the neutral point displacement voltage and waveform at this time are as follows: (1) Put the arc suppression coil into operation, start the unit, and maintain the rated speed of the generator; (2) Close the demagnetization switch; raise the generator voltage from zero to the rated voltage, measure the neutral point to ground voltage UN, and record the voltage waveform; (3) Reduce the excitation current to zero, open the demagnetization switch, shut down the machine, and the experiment ends; (4) Remove all test lines.

[0012] The present invention provides a large-scale hydro-generator set stator single-phase grounding and arc suppression coil gear adjustment test method, which has the following beneficial effects: 1. It can effectively measure the harmonic components in the single-phase fault current of the generator stator and conduct quantitative analysis; 2. Able to effectively measure the voltage deviation of the generator neutral point; 3. The relationship curve between each gear of the arc suppression coil and the grounding current can be obtained, thereby avoiding the full compensation point; 4. The relationship curve between each gear of the arc suppression coil and the neutral point displacement voltage can be obtained.

[0013] 5. Through the relationship curve between each gear of the arc suppression coil and the grounding current and neutral point displacement voltage, the appropriate gear of the arc suppression coil can be selected more reasonably and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 This is a test diagram of the neutral point displacement voltage and waveform when the unit is operating normally when the neutral point is not grounded; Figure 2 This is a test diagram of the effective value and harmonic component of the three-phase single-phase grounding current when the neutral point of the present invention is not grounded; Figure 3 This is a test diagram of single-phase grounding and arc suppression coil adjustment when the neutral point of the present invention is grounded through an arc suppression coil; Figure 4 This is a test diagram of the neutral point displacement voltage and waveform when the neutral point of the present invention is grounded through an arc suppression coil and operates normally. DETAILED DESCRIPTION

[0015] A test method for single-phase grounding and arc suppression coil gear adjustment of stator of large hydro-generator set. When the neutral point of the generator is not grounded, the unit operates normally and the neutral point displacement voltage and waveform are measured; When the neutral point of the generator is not grounded, measure the effective value of the grounding current and the current waveform when the three phases are grounded separately; When the neutral point of the generator is grounded through the arc suppression coil 1-17, measure the effective value and waveform of the single-phase grounding current, and the neutral point displacement voltage and waveform; When the neutral point of the generator is grounded through the arc suppression coil in the normal operating position, measure the neutral point displacement voltage and waveform at this time.

[0016] Preferably, Figure 1 As shown in the figure, when the neutral point of the generator is not grounded, the unit operates normally. The steps for measuring the neutral point displacement voltage and waveform at this time are as follows: (1) Start the unit and maintain the rated speed of the generator; (2) Pull open the neutral point switch and arc suppression coil, and close the demagnetization switch; the generator stops when the voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase; (3) Measure the neutral point displacement voltage and waveform to obtain the waveform components of the generator neutral point voltage.

[0017] The terminal voltage is taken from the voltage transformer. The neutral point voltage and waveform are recorded by the fault recording device to obtain the waveform components of the generator terminal voltage. The neutral point knife switch and arc suppression coil are operated according to the test conditions. Always pay attention that the neutral point and the outlet cannot be directly grounded at the same time to avoid the formation of a loop current. Since the arc suppression coil is not connected, the terminal voltage is only added to 0.5 times the rated voltage.

[0018] Preferably, Figure 2 As shown, when the neutral point of the generator is not grounded, the steps for measuring the effective value of the grounding current and the current waveform when the three phases are grounded separately are as follows: (1) Start the unit and maintain the rated speed of the generator; (2) Pull open the neutral point switch and arc suppression coil, and close the demagnetization switch; stop when the generator voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase, and measure the grounding current IcA of phase A and the neutral point-to-ground voltage UN1; (3) Use the WFLC_VI portable power recorder and analyzer to read and record the current waveform when phase A is single-phase grounded; (4) Reduce the excitation current to zero, open the demagnetization switch, stop the machine, change the single-phase grounding point to phases B and C, and repeat steps (1) to (3).

[0019] The voltage at the machine end is taken from the voltage transformer (note that the generator has residual voltage). The neutral point switch and arc suppression coil are switched on and off according to the test conditions. The magnetization process should be uniform and stable to ensure that the voltage at the machine end rises at a uniform speed.

[0020] Preferably, Figure 3As shown, when the neutral point of the generator is grounded through the arc suppression coil 1-17, the steps of measuring the effective value and waveform of the single-phase grounding current, the neutral point displacement voltage and waveform are as follows: (1) The arc extinguishing coil is put into operation and the gear is set according to the test method; (2) Start the unit and maintain the rated speed of the generator.

[0021] (3) Close the demagnetization switch; stop when the generator voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase, and measure the grounding point current Ic, the neutral point to ground voltage UN, and the inductor current IL; (4) Use the WFLC_VI portable power recorder to read and record the single-phase grounding current waveform, and use the fault recording device to record the neutral point voltage waveform; (5) Reduce the excitation current to zero, pull open the demagnetization switch, stop the machine, shift the arc extinguishing coil, and repeat steps (1) to (4) until all gears required by the test method are tested.

[0022] Keep the wiring of test 1 unchanged, and install a fault recording device at the neutral point to record the neutral point voltage waveform. The neutral point knife switch and arc suppression coil are put into operation, and the power generation division is responsible for adjusting the arc suppression coil.

[0023] Preferably, Figure 4 As shown, when the neutral point of the generator is grounded through the arc suppression coil in the normal operation position, the steps for measuring the neutral point displacement voltage and waveform at this time are as follows: (1) Put the arc suppression coil into operation, start the unit, and maintain the rated speed of the generator; (2) Close the demagnetization switch; raise the generator voltage from zero to the rated voltage, measure the neutral point to ground voltage UN, and record the voltage waveform; (3) Reduce the excitation current to zero, open the demagnetization switch, shut down the machine, and the experiment ends; (4) Remove all test lines.

[0024] Select the most suitable operating gear for the arc-cancelling coil and connect it to the neutral point. The generator starts from zero and then increases the voltage to the rated voltage.

[0025] The grounding phase ground wire and CT wiring should be firm and cannot be disconnected. The grounding phase ground wire should use a multi-strand copper core wire with a sufficient cross-section. During the test, the tester should keep a safe distance from the live equipment. Before the test, the magnitude of the grounding current should be calculated. During the test, pay attention to the control of the inductance current and the grounding current to avoid resonance. Strictly prevent the secondary short circuit of the voltage transformer and the secondary open circuit of the current transformer. During the test, a dedicated person should monitor the demagnetization switch during operation, and demagnetize quickly in case of abnormality.

[0026] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A large-scale hydro-generator stator single-phase grounding and arc suppression coil gear adjustment test method, characterized in that: When the neutral point of the generator is not grounded, the unit operates normally and the neutral point displacement voltage and waveform are measured; When the neutral point of the generator is not grounded, measure the effective value of the grounding current and the current waveform when the three phases are grounded separately; When the neutral point of the generator is grounded through the arc suppression coil 1-17, measure the effective value and waveform of the single-phase grounding current, and the neutral point displacement voltage and waveform; When the neutral point of the generator is grounded through the arc suppression coil in the normal operating position, measure the neutral point displacement voltage and waveform at this time.

2. According to claim 1, a large-scale hydro-generator stator single-phase grounding and arc suppression coil gear adjustment test method is characterized by: When the neutral point of the generator is not grounded and the unit is operating normally, the steps for measuring the neutral point displacement voltage and waveform at this time are as follows: (1) Start the unit and maintain the rated speed of the generator; (2) Pull open the neutral point switch and arc suppression coil, and close the demagnetization switch; the generator stops when the voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase; (3) Measure the neutral point displacement voltage and waveform to obtain the waveform components of the generator neutral point voltage.

3. According to claim 1, a large-scale hydro-generator stator single-phase grounding and arc suppression coil gear adjustment test method is characterized by: The steps of measuring the effective value of the grounding current and the current waveform when the neutral point of the generator is not grounded are as follows: (1) Start the unit and maintain the rated speed of the generator; (2) Pull open the neutral point switch and arc suppression coil, and close the demagnetization switch; stop when the generator voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase, and measure the grounding current IcA of phase A and the neutral point-to-ground voltage UN1; (3) Use a portable electrical quantity recorder and analyzer to read and record the current waveform when phase A is single-phase grounded; (4) Reduce the excitation current to zero, open the demagnetization switch, stop the machine, change the single-phase grounding point to phases B and C, and repeat steps (1) to (3).

4. According to claim 1, a large-scale hydro-generator stator single-phase grounding and arc suppression coil gear adjustment test method is characterized by: When the neutral point of the generator is grounded through the arc suppression coil 1-17, the steps of measuring the effective value and waveform of the single-phase grounding current, the neutral point displacement voltage and waveform are as follows: (1) The arc extinguishing coil is put into operation and the gear is set according to the test method; (2) Start the unit and maintain the rated speed of the generator; (3) Close the demagnetization switch; stop when the generator voltage rises from zero to 0.5 times the rated voltage of the non-grounded phase, and measure the grounding point current Ic, the neutral point voltage to ground UN, and the inductor current IL; (4) Use a portable electrical quantity recorder to read and record the single-phase grounding current waveform, and use a fault recording device to record the neutral point voltage waveform; (5) Reduce the excitation current to zero, pull open the demagnetization switch, stop the machine, shift the arc extinguishing coil, and repeat steps (1) to (4) until all gears required by the test method are tested.

5. According to claim 1, a large-scale hydro-generator stator single-phase grounding and arc suppression coil gear adjustment test method is characterized in that: When the neutral point of the generator is grounded in the normal operating position through the arc suppression coil, the steps for measuring the neutral point displacement voltage and waveform at this time are as follows: (1) Put the arc suppression coil into operation, start the unit, and maintain the rated speed of the generator; (2) Close the demagnetization switch; raise the generator voltage from zero to the rated voltage, measure the neutral point to ground voltage UN, and record the voltage waveform; (3) Reduce the excitation current to zero, open the demagnetization switch, shut down the machine, and the experiment ends; (4) Remove all test lines.

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