CN109738796B - Nuclear power half-speed steam turbine generator excitation winding fault diagnosis device and diagnosis method - Google Patents
Nuclear power half-speed steam turbine generator excitation winding fault diagnosis device and diagnosis method Download PDFInfo
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Abstract
The invention discloses a nuclear power half-speed steam turbine generator excitation winding fault diagnosis device and method based on stator double detection coils. Aiming at a half-speed steam turbine generator unit commonly adopted by a nuclear power plant at present, a coil is respectively arranged on the tops of 2 stator core teeth with a distance of 1 pole pitch, and the diagnosis method judges turn-to-turn short circuit faults and fault degrees of an excitation winding according to frequency domain and time domain characteristics of induced voltages of the 2 coils. The invention is not influenced by the running state of the generator and can realize accurate positioning of faults. The method solves the defects of the prior art, is more suitable for the diagnosis requirement of the nuclear power half-speed steam turbine generator unit, and improves the diagnosis level.
Description
Technical Field
The invention relates to a generator excitation winding fault diagnosis device and a diagnosis method, in particular to a nuclear power half-speed steam turbine generator excitation winding fault diagnosis device and a diagnosis method, and belongs to the technical field of generators.
Background
The turn-to-turn short circuit fault of the excitation winding is a chronic problem of large synchronous generators. The turn-to-turn short circuit fault of the excitation winding usually causes severe vibration of the generator, the unipolar effect of the fault may also magnetize the journal of the generator, the resulting shaft current risks burning the journal and the bearing bush, and the short circuit fault may develop into a one-point or two-point ground fault of the rotor winding. The negative factors seriously influence the normal operation of the synchronous generator, so that the realization of the on-line monitoring of the turn-to-turn short circuit fault of the excitation winding of the synchronous generator is of great significance.
The currently proposed synchronous generator excitation winding turn-to-turn short circuit fault online diagnosis method mainly comprises the following steps: an excitation current method, an axis voltage method, an end leakage flux method, a virtual power method, an expected electromotive force method, a stator branch loop method, and a search coil method.
The excitation current method is used for identifying faults by utilizing the characteristics that the excitation current of the generator is increased and the reactive power is reduced after the faults occur. The method can detect some obvious turn-to-turn short circuit faults, requires accurate excitation current measurement, and is not suitable for a rotary excitation type generator. The shaft voltage method and the end leakage flux method detect faults by using even or fractional harmonics induced by a main shaft and an end of the motor, but the two methods cannot realize fault location. The virtual power method and the expected electromotive force method are used for diagnosing turn-to-turn short circuit faults by utilizing the relative deviation of expected electromagnetic power and actual electromagnetic power or expected excitation electromotive force and actual excitation electromotive force, and the two methods are not suitable for rotary excitation generators and can not realize fault positioning. The stator branch circulation method is used for identifying faults through characteristic subharmonics generated by stator parallel branch circulation during faults, and a current transformer needs to be installed on the stator parallel branch.
The traditional detection coil method detects the slot leakage flux of a rotor through a miniature radial/tangential coil arranged at an air gap of a generator, judges turn-to-turn short circuit faults of an excitation winding based on the correlation between the rotor slot leakage flux and the number of effective ampere turns in a slot, has a fault positioning function, is widely applied, has the defects of insufficient anti-interference capacity and seriously reduced detection sensitivity under a load working condition. On the basis of the method, a novel detection coil method is developed, a U-shaped detection coil is installed around a stator core section, a rotor air gap main magnetic field is directly detected, faults are judged through main magnetic field harmonic waves, and the diagnostic anti-interference performance of the method is obviously improved compared with that of a traditional detection coil method. However, this method requires the detection coil to be inserted into the air gap field of the generator, which brings about a great safety hazard.
The nuclear power turbo generator set usually adopts two pairs of half-speed synchronous generators due to high output power, and an excitation system usually adopts a brushless excitation mode, so that the excitation current cannot be measured. In summary, the methods are not particularly suitable for fault diagnosis of turn-to-turn short circuit of the excitation winding of the nuclear power half-speed steam turbine generator, so that the diagnosis level of the faults needs to be improved, and the method is more suitable for application in the nuclear power field.
Disclosure of Invention
The invention aims to provide a nuclear power half-speed turbogenerator excitation winding fault diagnosis device and method based on stator double detection coils.
In order to solve the technical problems, the invention adopts the technical scheme that:
the first technical scheme is as follows:
a nuclear power half-speed turbine generator excitation winding fault diagnosis device based on stator double detection coils is characterized in that two detection coils surrounding stator tooth grooves are arranged in a generator, the two detection coils are led out through a stator core radial cooling air duct, an 800-omega resistor and a 1200-omega resistor are connected in parallel to an outlet of the cooling air duct, voltage output ends of the two detection coils are respectively connected to a data acquisition device, and superposition or difference making is carried out in the data acquisition device.
The two detection coils are arranged on the small teeth of the stator core of the generator at a certain distance.
The outlet of the cooling air duct is connected with a 1000 omega resistor in parallel.
The second technical scheme is as follows:
a nuclear power half-speed steam turbine generator excitation winding fault diagnosis method based on stator double detection coils comprises the following steps:
step a: when the generator runs, the data acquisition device acquires the output voltages of the two detection coils in real time;
step b: the data acquisition device makes a difference between the output voltages of the two detection coils;
step c: calculating the percentage content of preset harmonic in the output voltage difference result of the two detection coils, if the harmonic content exceeds a preset threshold value, judging that the generator has an excitation winding turn-to-turn short circuit fault, and turning to the step d; otherwise, turning to the step b;
step d: and the data acquisition device superposes the output voltage signals of the two detection coils, and if a wave crest appears in a superposition result curve, the turn-to-turn short circuit fault of the excitation winding at the wave crest is judged.
For a nuclear power half-speed generator, the distance between two detection coils is fixed as a polar distance.
For a nuclear power half-speed generator, preset harmonics are 1/2, 3/2, 5/2 and 7/2 subharmonics, and the percentage content of the harmonics is 5%.
The technical effect obtained by adopting the technical scheme is as follows:
1. the invention improves the diagnosis level of the nuclear power half-speed steam turbine generator unit;
2. the invention is not only suitable for the brushless excitation system, but also suitable for the brush excitation system, and is particularly suitable for the development trend of modern nuclear power;
3. the invention not only has high sensitivity, but also can realize accurate positioning of faults;
4. the detection coil is hidden in installation position, and the normal operation of the generator cannot be influenced.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a view showing the installation of a detection coil in embodiment 1 of the present invention;
fig. 2 is a partially enlarged view of a detection coil in embodiment 1 of the present invention;
fig. 3 is a waveform diagram of excitation magnetic potential of a two-pole generator in a normal state in embodiment 2 of the present invention;
FIG. 4 is a diagram of the distribution of the reverse current applied to the shorted turns in example 2 of the present invention;
FIG. 5 is a diagram showing the connection of the magnetic winding in embodiment 2 of the present invention;
fig. 6 is a waveform diagram of the induction voltage of the airborne detection coil in embodiment 2 of the present invention;
FIG. 7 is a graph of the induced voltage of the rated load search coil in example 2 of the present invention;
fig. 8 is a graph of induced voltage spectrum of an airborne search coil in embodiment 2 of the present invention;
FIG. 9 is a graph of the induced voltage spectrum of the rated load detection coil in embodiment 2 of the present invention;
fig. 10 is a waveform diagram of induction voltage of a detection coil with different slot winding faults in air load in embodiment 2 of the invention;
FIG. 11 is a waveform diagram of the induction voltage of the detection coil for the faults of the slot windings with different rated loads in embodiment 2 of the present invention;
fig. 12 is a detection circuit of a subsequent stage of the detection coil in embodiment 1 of the present invention;
wherein 1-detection coil.
Detailed Description
Example 1:
the utility model provides a nuclear power half-speed turbo generator excitation winding fault diagnosis device based on two detection coils of stator, generator inside is equipped with two detection coil 1 that surround the stator tooth's socket, and two detection coil 1 are all drawn forth through the radial cooling duct of stator core to at the parallelly connected 1000 omega resistance of cooling duct export, the voltage output end of two detection coil 1 inserts data acquisition device respectively, superposes or makes the difference in data acquisition device.
The two detection coils 1 are arranged on small teeth of a stator core of the generator at a certain distance.
Example 2: the difference from the embodiment 1 is that the outlet of the cooling air duct is connected with an 800 omega resistor in parallel.
Example 3: the difference from the embodiment 1 is that the cooling air duct outlet is connected with a 1200 omega resistor in parallel.
Example 4:
a nuclear power half-speed steam turbine generator excitation winding fault diagnosis method based on stator double detection coils comprises the following steps:
step a: when the generator runs, the data acquisition device acquires the output voltages of the two detection coils 1 in real time;
step b: the data acquisition device makes a difference between the output voltages of the two detection coils 1;
step c: calculating the percentage content of preset harmonic in the output voltage difference result of the two detection coils 1, if the harmonic content exceeds a preset threshold value, judging that the generator has an excitation winding turn-to-turn short circuit fault, and turning to the step d; otherwise, turning to the step b;
step d: and the data acquisition device superposes the output voltage signals of the two detection coils 1, and if a wave crest appears in a superposition result curve, the turn-to-turn short circuit fault of the excitation winding at the wave crest is judged.
For a nuclear power half-speed generator, the distance between two detection coils 1 is fixed as a polar distance.
For a nuclear power half-speed generator, preset harmonics are 1/2, 3/2, 5/2 and 7/2 subharmonics, and the harmonic percentage content threshold is 5%.
The percentage content a% of harmonic waves is as follows:
wherein, F1Is the fundamental amplitude, F1/2At 1/2 th harmonic amplitude, F3/2At 3/2 th harmonic amplitude, F5/2At 5/2 th harmonic amplitude, F7/2At 7/2 th harmonic amplitude.
The nuclear power unit generally adopts a 2-pair-pole steam turbine generator unit. Under the normal operation state, the excitation magnetic potential of the 2-pair-pole steam turbine generator is step-shaped wave, as shown in fig. 3.
PA、PB、PCAnd PDRespectively represent 4 magnetic poles of the rotor, and the magnetomotive force expression under the normal state is as follows:
in the formula: ffTo excite magnetic potential, IfFor exciting current, akIs the number of winding turns in the k-th slot of the rotor, beta is the rotor slot angle, gamma is the rotor large tooth area circumferential angle, thetarIs the rotor space electrical angle.
When the winding is normal, the excitation magnetic potential of the 2-pair-pole turbonator only contains odd harmonics. Under the condition of not counting magnetic field saturation and smooth rotor surface, the air gap main magnetic field only contains odd harmonics and is mainly a fundamental wave component.
After the turn-to-turn short circuit of the excitation winding, the excitation magnetic potential of the fault pole is weakened, and the magnetic potential of the generator is in an asymmetric state. The excitation magnetic potential after the fault is equivalent to the superposition of the magnetic potential in the normal state and the magnetic potential generated by applying reverse current to the short-circuit turn. The magnetomotive force profile produced by the application of reverse current by the shorting turn is shown in fig. 4.
Fourier analysis of the magnetic potential of the shorted turns of fig. 4 with reverse current applied gives:
in the formula: alpha is the mechanical angle of rotor space, w is the number of short-circuit turns of exciting winding, omegarFor rotation of rotorsMechanical angular velocity of, Δ FfAnd applying the excitation magnetic potential of reverse current to the short-circuit turns, wherein m is the number of the excitation coil.
After the turn-to-turn short circuit fault occurs in the excitation winding, the excitation magnetomotive force contains fractional harmonics.
A characteristic magnetic field generated by a turn-to-turn short circuit fault of the excitation winding circulates along a closed main loop formed by the rotor core-air gap-stator core, and as the rotor rotates synchronously, magnetic flux flowing through the detection coil 1 alternates with time, and the alternating magnetic flux induces a voltage in the detection coil 1.
Taking no-load operation as an example, a detection coil 1 is analyzed, and in a normal state, magnetic flux flowing through the detection coil 1 is alternately changed along with time, wherein the expression is as follows:
wherein phi1B is the magnetic flux density of the main magnetic field, l is the axial length of the search coil, and R is the distance from the search coil 1 to the rotor axis.
The induced electromotive force of the detection coil 1 can be obtained by derivation of the magnetic flux:
in the formula: e.g. of the type1To detect the induced electromotive force of the coil 1.
Similarly, the induced electromotive force e of the other detection coil 12Comprises the following steps:
the difference e (t) between the induced voltages of the two detection coils 1 is:
therefore, the induced voltage difference of the detection coil 1 in the normal operation state contains only odd harmonics such as 1, 3, 5, etc.
After the turn-to-turn short circuit fault of the excitation winding of the 2-pair pole generator occurs, 1/2, 3/2, 5/2 and 7/2 order fractional harmonics are generated by air gap magnetic flux. Magnetic flux of harmonic flux through one detecting coil 1 of'1Can be expressed as:
electromotive force e 'induced by the detection coil 1'1(t) is:
in the formula: theta is the angle between two coil sides in the axial direction of the detection coil 1, and omega is the electrical angular velocity of the rotor rotation.
The induced voltage difference of the two detection coils 1 is e' (t):
therefore, the electromotive force induced by the search coil 1 also has 1/2, 3/2, 5/2, 7/2 order equal-fraction harmonics, which can be used as a basic feature for detecting a turn-to-turn short circuit fault of the excitation winding.
The following takes a nuclear electric field TA-1100-78 type steam turbine synchronous generator as an example, and the parameters are shown in Table 1.
The excitation winding connection pattern and slot number are shown in fig. 5.
In the no-load and rated operation states, the No. 7 slot of the TA-1100-78 generator is respectively set to generate short circuits of the excitation windings with different degrees of 1, 3, 5 and 7 turns. The voltage waveforms induced by the search coil 1 on the stator during no-load and nominal operation are shown in figures 6 and 7 respectively.
As can be seen from fig. 6 and 7: when the No. 7 slot excitation winding has turn-to-turn short circuit fault, the induced voltage of the detection coil 1 has asymmetric phenomenon, the induced voltage waveform has locally reduced phenomenon, as shown in a rectangular area, and the more serious the short circuit degree is, the more obvious the induced voltage waveform asymmetry is.
The induced voltage in the detection coil 1 is fourier decomposed to obtain the content of each harmonic, as shown in fig. 8 and 9.
As can be seen from fig. 8 and 9: after the turn-to-turn short circuit fault occurs in the excitation winding, the fraction harmonic wave appears in the induction voltage in the detection coil 1, and the more serious the fault degree is, the higher the fraction harmonic wave content is.
And under the no-load and rated operation states, a short-circuit fault of No. 1 groove 3 turns, a short-circuit fault of No. 3 groove 3 turns and a short-circuit fault of No. 5 groove 3 turns are respectively set for simulation. The induced voltages of the two detection coils 1 are superimposed to obtain a voltage superimposed waveform as shown in fig. 10 and 11.
As can be seen from fig. 10 and 11: in normal operation, the sum of the induced voltages of the two detection coils 1 is almost zero. In a fault state, the induction voltages of the two detection coils 1 have local deviation, the superposition result is not zero, and the peak position and the position of the short circuit slot have a corresponding relation, so that the fault position of turn-to-turn short circuit can be effectively diagnosed.
The subsequent detection circuits of the two detection coils 1 are shown in fig. 12.
In conclusion, the method can effectively diagnose the turn-to-turn short circuit fault of the excitation winding, the harmonic content can effectively reflect the degree of the short circuit fault, and the method can realize accurate fault positioning.
TABLE 1
Claims (2)
1. A nuclear power half-speed steam turbine generator excitation winding fault diagnosis method based on stator double detection coils is characterized by comprising the following steps: the fault diagnosis device comprises two detection coils surrounding a stator tooth slot, wherein the two detection coils (1) are led out through a radial cooling air channel of a stator core, 800-1200 omega resistors are connected in parallel at an outlet of the cooling air channel, voltage output ends of the two detection coils (1) are respectively connected to a data acquisition device, and superposition or difference is carried out in the data acquisition device;
the two detection coils (1) are arranged on small teeth of a stator core of the generator;
the distance between the two detection coils (1) is fixed as a polar distance;
the method for diagnosing the fault of the excitation winding of the nuclear power half-speed turbonator based on the double detection coils of the stator comprises the following steps of:
step a: when the generator runs, the data acquisition device acquires the output voltages of the two detection coils (1) in real time;
step b: the data acquisition device makes a difference between the output voltages of the two detection coils (1);
step c: calculating the percentage content of preset harmonic in the output voltage difference result of the two detection coils (1), if the harmonic content exceeds a preset threshold value, judging that the generator has an excitation winding turn-to-turn short circuit fault, and turning to the step d; otherwise, turning to the step b;
step d: and the data acquisition device superposes output voltage signals of the two detection coils (1), and if a wave crest appears in a superposition result curve, the turn-to-turn short circuit fault of the excitation winding at the wave crest is judged.
2. The stator double-detection-coil-based fault diagnosis method for the excitation winding of the nuclear power half-speed steam turbine generator according to claim 1, characterized by comprising the following steps of: the outlet of the cooling air duct is connected with a 1000 omega resistor in parallel.
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| CN110197043B (en) * | 2019-06-11 | 2023-07-04 | 华北电力大学（保定） | Damping modeling and checking method in finite element simulation process of turbonator |
| CN111650509B (en) * | 2020-05-12 | 2022-10-14 | 浙江浙能电力股份有限公司台州发电厂 | Fault judgment method and device for brushless excitation motor, computer equipment and medium |
| CN112198449A (en) * | 2020-08-25 | 2021-01-08 | 中广核核电运营有限公司 | Excitation winding short-circuit fault detection method and device of brushless excitation system |
| CN113359027B (en) * | 2021-05-14 | 2023-03-21 | 重庆文理学院 | Permanent magnet synchronous motor turn-to-turn short circuit fault diagnosis method with low spatial magnetic field resolution requirement |
| CN113777530B (en) * | 2021-09-10 | 2023-07-11 | 华北电力大学（保定） | Open-circuit fault diagnosis method for rotating diode of inner rotor type three-phase brushless exciter |
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| CN102087329B (en) * | 2010-11-19 | 2013-05-22 | 清华大学 | Method for judging turn-to-turn short circuit fault position and number of short circuit turns of steam turbine generator rotor |
| CN102355090B (en) * | 2011-10-20 | 2013-02-27 | 清华大学 | Exploring coil arrangement method simultaneously reflecting electric generator stator and rotor internal short circuits |
| CN104155567B (en) * | 2014-08-30 | 2017-01-25 | 华北电力大学（保定） | Positioning method of turn-to-turn short circuit fault of doubly-fed generator rotor |
| CN106772037B (en) * | 2016-12-15 | 2019-07-09 | 华北电力大学（保定） | Synchronous generator rotor winding interturn short-circuit diagnostic method based on twin coil |
| CN106443318B (en) * | 2016-12-15 | 2019-06-18 | 华北电力大学（保定） | Hydraulic generator rotor winding interturn short-circuit diagnostic method based on core through screw rod |
| CN106771835B (en) * | 2016-12-15 | 2019-06-18 | 华北电力大学（保定） | Rotor of steam turbo generator turn-to-turn short circuit diagnostic device and method based on detection coil |
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