CN106772037B - Synchronous generator rotor winding interturn short-circuit diagnostic method based on twin coil - Google Patents

Abstract

The invention discloses a method for diagnosing short-circuit between turns of a rotor winding of a synchronous generator based on a double coil, comprising the following steps: A. Two U-shaped detectors are installed on the stator core segment inside the synchronous generator with a certain distance and radial direction. Coil, the output ports of the two U-shaped detection coils are connected in parallel with high-resistance resistors with the same resistance value, and the data acquisition device is used to collect the voltage signals of the output ports of the two U-shaped detection coils; B. During the operation of the generator, the data The voltage signals at the outlet of the two U-shaped detection coils collected by the acquisition device are processed in real time, and the output voltages of the two U-shaped detection coils are differentiated or added. When the result exceeds the set threshold, it is determined that the synchronous generator has a rotor. Turn-to-turn short circuit fault. The present invention can improve the deficiencies of the prior art and improve the diagnosis level of such faults.

Description

Diagnosis method of inter-turn short circuit of synchronous generator rotor winding based on double coil

technical field

The invention relates to the technical field of generators, in particular to a method for diagnosing inter-turn short-circuits of rotor windings of synchronous generators based on double coils.

Background technique

The rotor winding inter-turn short-circuit fault is a common fault of synchronous generators. The further deterioration of the fault may cause the vibration of the synchronous generator to intensify, and even cause problems such as one-point grounding of the rotor, two-point grounding of the rotor, loss of magnetization, and large-axis magnetization. Therefore, enough attention should be paid to the inter-turn short-circuit fault of the rotor winding of the synchronous generator. It is the future development trend to use the online diagnosis method to detect the inter-turn short-circuit fault of the rotor winding of the synchronous generator.

At present, the main on-line diagnosis methods for rotor winding inter-turn short-circuit faults of synchronous generators are: detection coil method, excitation current method, stator winding parallel branch circulating current method, imaginary power method, expected potential method, stator detection coil method, shaft voltage method method and end leakage flux method, etc. Some of these detection methods rely on the accurate measurement of the excitation current, such as the excitation current method, the virtual power method, and the expected potential method. However, for brushless excitation synchronous generators, the excitation current cannot be accurately measured, so these methods are not suitable for brushless excitation synchronous generators. Some detection methods have high sensitivity in theory, such as stator winding parallel branch circulation method, stator detection coil method, shaft voltage method and end leakage flux method, etc., but their practicability is poor. For the stator winding parallel branch circulating current method, since the current synchronous generator (especially the turbogenerator) does not have an independent current transformer installed in the parallel branch of each phase winding of the stator, only the phase current transformer is installed, and the stator winding The parallel branch circulating current method does not have the conditions for collecting data and cannot be put into practical application; the stator detection coil method requires a large-sized detection coil to be placed in the stator slot of the generator, which may endanger the insulation of the stator winding, and reliability and safety are required. Problem solved first. The shaft voltage method needs to install shaft voltage measurement carbon brushes at both ends of the generator. Due to the poor contact reliability between the carbon brushes and the large shaft, the quality of the collected signals is affected, and it is rarely used at present. In the end leakage flux method, a magnetic flux detection coil should be installed on the leakage magnetic circuit at the end of the generator (generally, holes are drilled on the joint surface of the upper and lower end covers). In addition, the sensitivity and reliability of the proposed on-line detection methods are generally low, and the detection ability for minor rotor winding inter-turn short-circuit faults is limited. Taking the detection coil method as an example, this method diagnoses the inter-turn short-circuit fault of the rotor winding by detecting the change of the leakage flux of the rotor slot of the turbine generator. Turn-to-turn short circuit fault.

Among the above-mentioned on-line detection methods, many methods are only suitable for steam turbine generators, not for hydraulic turbine generators. This is because: the number of pole pairs of the hydro-generator is as many as tens of pole pairs, the speed is low, the space size is large, and the stator winding has many branches. The inter-turn short-circuit fault occurs in the rotor winding of a magnetic pole to affect the local related electrical quantities, and the impact on the entire generator is relatively small. Therefore, the excitation current method, the virtual power method, the expected potential method, the shaft voltage method and the end leakage method It is difficult to detect the short-circuit fault between turns of the rotor winding of the hydro-generator sensitively. The rotor of the hydro-generator is of salient pole structure, and the windings are centralized. The detection coil method most commonly used in turbo-generators is also not suitable for hydro-generators, because the detection coil can only detect the concentrated magnetic flux leakage at the rotor slot. It is impossible to detect the distributed main magnetic flux of the hydro-generator.

In a word, although much attention is paid to the fault diagnosis of rotor winding inter-turn short-circuit faults of synchronous generators, practical and excellent on-line detection methods are seriously lacking. Hydrogenerator. Therefore, it is necessary to further improve the diagnosis level of such faults, and develop an on-line detection method for short-circuit between turns of synchronous generator rotor windings with good practicability and versatility.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a method for diagnosing inter-turn short-circuits of synchronous generator rotor windings based on double coils, which can solve the deficiencies of the prior art and improve the diagnosis level of such faults.

In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows.

A method for diagnosing short-circuit between turns of a rotor winding of a synchronous generator based on a double coil is characterized by comprising the following steps:

A. Install two U-shaped detection coils in the radial direction at a certain distance on the stator core section inside the synchronous generator. The output ports of the two U-shaped detection coils are connected in parallel with high-resistance resistors with the same resistance value, and the data acquisition device is used to collect The voltage signals of the output ports of the two U-shaped detection coils;

B. During the operation of the generator, real-time processing is performed on the voltage signals at the exits of the two U-shaped detection coils collected by the data acquisition device, and the output voltages of the two U-shaped detection coils are differentiated or added. When the result exceeds the set value When the threshold is set, it is determined that the synchronous generator has an inter-turn short-circuit fault of the rotor winding.

Preferably, the distance between the two U-shaped detection coils is an integer multiple of the pole pitch of the generator, and the integer is greater than or equal to 1 and less than or equal to the number of magnetic poles minus 1.

Preferably, when the distance between the two U-shaped detection coils is an odd multiple of the generator pole pitch, add the output voltages of the two U-shaped detection coils; when the distance between the two U-shaped detection coils is the When the pole distance is an even multiple, the output voltage of the two U-shaped detection coils is made difference.

Preferably, the difference or addition of the output voltages of the two U-shaped detection coils is proportional to the degree of short-circuit fault between turns of the rotor winding.

Preferably, the fault determination threshold is set to 0.15V.

The beneficial effects brought by the above technical solutions are: the diagnostic method of the present invention can diagnose the rotor winding inter-turn short-circuit fault of the synchronous generator online, and the two U-shaped detection coils can eliminate the influence of the change of the generator operating conditions on the detection effect , with high anti-interference ability and diagnostic accuracy. This is of great significance for preventing the deterioration of the inter-turn short-circuit fault of the rotor winding of the synchronous generator, reducing the economic loss caused by the unplanned outage time, and improving the stability of the power system.

Description of drawings

Figure 1 is a schematic diagram of the excitation magnetic potential after the rotor winding is short-circuited between turns;

Figure 2 is a two-dimensional simulation model of a synchronous generator;

Figure 3 is a partial view of the no-load main magnetic field of the synchronous generator;

Figure 4 is a partial diagram of the main magnetic field of the rated load of the synchronous generator;

Figure 5 is a schematic diagram of the new detection coil structure and installation;

Fig. 6 is the induced voltage waveform of two detection coils when the no-load rotor winding of the synchronous generator is normal;

Fig. 7 Induced voltage waveforms of the two detection coils when the no-load rotor winding of the synchronous generator is short-circuited by 10%;

Figure 8 Induced voltage waveforms of the two detection coils when the no-load rotor winding of the synchronous generator is short-circuited by 20%;

Figure 9 is the induced voltage waveform of the two detection coils when the rated load rotor winding of the synchronous generator is normal;

Fig. 10 Induced voltage waveforms of two detection coils when the rotor winding of the rated load of the synchronous generator is short-circuited by 10%;

Fig. 11 Induced voltage waveforms of the two detection coils when the rotor winding of the rated load of the synchronous generator is short-circuited by 20%;

Fig. 12 The induced voltage waveforms of the two detection coils when the no-load excitation current of the synchronous generator increases by 10% when the rotor winding is short-circuited.

In the figure: 1. Faulty pole, 2. Normal pole, 3. Magnetic flux density of normal pole, 4. Magnetic flux density of faulty pole, 5. Damping strip, 6. Rotor pole core, 7. Stator winding, 8. Stator core, 9. Rotor winding, 10. High resistance resistor, 11. Detection coil, 12. Detection coil 1, 13, Detection coil 2.

Detailed ways

The standard parts used in the present invention can be purchased from the market, the special-shaped parts can be customized according to the description in the description and the drawings, and the specific connection methods of each part are all mature bolts, rivets, welding in the prior art. , pasting and other conventional means will not be described in detail here.

The list of symbols in the text is: ω _r , the mechanical angular velocity of rotor rotation; ω, the electrical angular velocity of rotor rotation, ω=2πf=314 (rad/S); L, the effective axial length of the detection coil; R, the probe of the detection coil The length from the rotor center; P, the number of pole pairs of the synchronous generator; _i , odd number, i.e. i=1, 3, 5...; B _i , the amplitude of the i harmonic magnetic density; The mechanical angle; F _f , the excitation magnetic potential after the short-circuit fault between turns of the rotor winding.

A specific embodiment of the present invention includes the following steps:

Two U-shaped detection coils are installed radially at a certain distance on the stator core section inside the synchronous generator. The output ports of the two U-shaped detection coils are connected in parallel with high-resistance resistors with the same resistance value. The voltage signal of the output port of the U-shaped detection coil;

During the operation of the generator, real-time processing is performed on the voltage signals at the outlets of the two U-shaped detection coils collected by the data acquisition device, and the output voltages of the two U-shaped detection coils are subtracted or added. When the result exceeds the set threshold , it is determined that the synchronous generator has an inter-turn short-circuit fault of the rotor winding.

The distance between the two U-shaped detection coils is an integer multiple of the pole pitch of the generator, which is greater than or equal to 1 and less than or equal to the number of magnetic poles minus 1.

When the distance between the two U-shaped detection coils is an odd multiple of the generator pole pitch, add the output voltages of the two U-shaped detection coils; when the distance between the two U-shaped detection coils is the generator pole pitch When it is an even multiple of , the output voltage of the two U-shaped detection coils is made difference.

The difference or addition of the output voltages of the two U-shaped detection coils is proportional to the degree of short-circuit fault between turns of the rotor winding.

The fault judgment threshold is set to 0.15V.

When a part of the winding of a certain magnetic pole of the rotor of a synchronous generator is short-circuited between turns, the internal current of the short-circuited winding is zero, the number of effective turns of the magnetic pole is reduced, and the generated excitation magnetic potential is significantly smaller than the normal magnetic pole. For example, see Figure 1.

The imbalance of the generator excitation potential will further cause the imbalance of the main magnetic field. In order to accurately calculate the main magnetic field of the synchronous generator, numerical analysis methods such as finite element are required. The following takes a 550MW synchronous generator as an example, and the parameters are shown in Table 1.

Table 1 Synchronous generator parameters

The simulation is divided into two working conditions, namely the generator no-load rated voltage operation and the rated load operation, respectively setting a certain magnetic pole winding of the rotor to be normal, short-circuit 5%, short-circuit 10%, short-circuit 15% and short-circuit 20%. The main magnetic field of the generator air gap is shown in Figure 2 and Figure 3:

It can be seen from Figure 2 and Figure 3 that no matter the synchronous generator is running at no-load or rated load, when the rotor winding is normal, the magnetic field of each magnetic pole is basically the same; The magnetic field of the magnetic pole is significantly smaller than that of the normal pole, and the magnetic field of the two magnetic poles adjacent to the magnetic pole is also weakened.

Generally, the stator core of large synchronous generator adopts a hydrogen-cooled structure. The stator core is divided into several sections along the axial direction, and hydrogen flows between the sections. The above structure of the synchronous generator provides a sensor installation space for the diagnosis of rotor winding inter-turn short-circuit faults. A new type of generator magnetic field detection coil is proposed below. Its structure and installation method are shown in Figure 4.

The detection coil presents a U-shape and surrounds an iron core segment of the stator of the synchronous generator in the radial direction, and the bottom of the U-shape is located in the air gap between the stator and the rotor. During the rotor rotation, the stator iron yoke flows through the main magnetic flux, and the detection coil surrounds the stator iron yoke. Therefore, the induced voltage of the detection coil reflects the main magnetic field of the synchronous generator. When an inter-turn short circuit occurs in a magnetic pole winding of a synchronous generator, the magnetic field of the magnetic pole is significantly weakened, and the voltage signal induced by the detection coil can reflect this phenomenon, and then the inter-turn short circuit fault of the rotor winding of the synchronous generator can be diagnosed.

Taking the no-load operation of a synchronous generator as an example, the generator air-gap magnetic flux density can be expressed as:

Assuming that the detection coil is just at a certain N-pole axis position of the rotor at the initial moment, the magnetic flux passing through the detection coil is zero. As the rotor rotates, the magnetic flux through the detection coil starts to increase, and after t time, the magnetic flux through the detection coil can be expressed as:

The AC potential induced by the detection coil can be expressed as:

It can be seen from the above formula that the detection coil is essentially a magnetic field measurement coil, and the electromotive force induced by the detection coil has the same shape as the generator air gap magnetic field.

After the excitation winding of the synchronous generator is short-circuited, the magnetic field of the faulty magnetic pole of the rotor is significantly reduced. Therefore, when the faulty magnetic pole sweeps the detection coil fixed on the stator core, the voltage amplitude induced by the detection coil will also be smaller than other magnetic poles. Sweep the detection coil.

However, the use of one detection coil to diagnose inter-turn short-circuit faults of the rotor winding also has certain problems: when the different magnetic poles of the synchronous generator sweep across the detection coil in turn, the operating conditions of the synchronous generator may have changed, and the stator core of the generator may have changed. The internal magnetic field will also change, causing the induced voltage value of the detection coil to change. In this way, even if the inter-turn short circuit does not occur in the rotor winding, it may be misdiagnosed as an inter-turn short circuit, and the anti-interference ability of the diagnosis is insufficient.

In order to solve the above problems, the present invention proposes to install two detection coils on the stator core of the synchronous generator at the same time, and the distance between the two detection coils is an integer multiple of the generator pole distance. When the pole distance is an odd multiple, one of the coils is under the N pole, and the other coil is at the corresponding position under the S pole, and the voltage waveforms induced by the two coils at any time are just out of phase. The output voltages are summed. If the rotor winding is normal, the added result will be zero. If there is an inter-turn short circuit fault in a certain magnetic pole of the rotor, the output voltage of the two detection coils will have a local deviation, and the added result will not be zero. Similarly, when two U When the distance between the detection coils is an even multiple of the generator's pole pitch, and one coil is under the N pole, the other coil is at the corresponding position under the other N pole, and the voltage waveforms induced by the two coils at any time are exactly the same. , After subtracting the output voltages of the two U-shaped detection coils, if the rotor windings are normal, the result will be zero after the subtraction. If there is an inter-turn short circuit fault in a certain magnetic pole of the rotor, the output voltages of the two detection coils will have local deviations , the subtraction result is not zero.

The above is the basic principle of the double-coil method for diagnosing the inter-turn short circuit of the rotor winding of the synchronous generator. The advantage of this detection is that when the generator operating conditions change, the magnetic field passing through the two detection coils changes simultaneously, so when the rotor winding of the synchronous generator is normal, the output voltages of the two detection coils are always the same. , the anti-interference ability of the diagnostic method has been greatly improved.

Taking the aforementioned 550MW synchronous generator as an example, set two detection coils with a pole distance of 6 times, as shown in Figure 5.

First, make the generator run stably under the no-load rated voltage condition, set a certain magnetic pole winding of the rotor to be normal, short-circuit 10%, and short-circuit 20% respectively. The induced voltages of the two detection coils are shown in Figures 6-8. It can be seen that when the rotor winding is short-circuited between turns of the synchronous generator, the output voltage of the two detection coils has a local deviation (elliptical area), and the voltage induced by the fault pole on the detection coil is significantly lower than that of the normal magnetic pole. The voltage value, the deviation position corresponds to the distance between the two detection coils. It can also be seen that the more severe the short circuit, the greater the above deviation.

It can also be seen from Figures 7 and 8 that under the no-load condition, the magnetic field of the magnetic pole adjacent to the faulty pole also changes slightly due to the influence of the faulty pole. Therefore, in Figures 7 and 8, the There are also slight deviations in the induced voltages of the two detection coils on the left and right sides of the oval area.

Let the generator run stably with the rated load, and set a certain magnetic pole winding of the rotor to be normal, short-circuit 10%, and short-circuit 20%. The induced voltages of the two detection coils are shown in Figures 9-11. It can be seen that when the rotor winding is short-circuited between turns of the synchronous generator, the output voltage of the two detection coils also has a local deviation (oval area), and the voltage induced by the fault pole on the detection coil is significantly lower than normal. The voltage value of the magnetic pole and the position where the deviation occurs corresponds to the distance between the two detection coils. It can also be seen that the more severe the short circuit, the greater the above deviation.

It can also be seen from Figures 10 and 11 that under the rated load condition, the magnetic field of the magnetic pole adjacent to the faulty pole also changes slightly due to the influence of the faulty pole. Therefore, in Figures 10 and 11, the There are also slight deviations in the induced voltages of the two detection coils on the left and right sides of the oval area.

In order to verify the anti-interference ability of the dual-coil diagnosis method, taking the generator no-load operation as an example, the excitation current is changed within one rotation cycle of the generator, so that the excitation current increases from 0.5 times the no-load rated excitation current to the no-load rated excitation current , set a certain magnetic pole winding of the rotor to be short-circuited by 10%, and the induced voltages of the two detection coils are obtained as shown in Figure 12. As can be seen from Figure 12, even if the working conditions of the generator change during operation, when the two detection coils scan the fault slot, the output voltage waveform still has obvious deviations. Therefore, the double detection coil method has a strong anti-interference ability.

The difference in the amplitudes of the induced voltages of the two detection coils can effectively diagnose the short-circuit fault between the rotor windings of the synchronous generator. Therefore, this method can also reflect the severity and development trend of rotor winding inter-turn short-circuit faults.

In the description of the present invention, it should be understood that the terms "portrait", "horizontal", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or It is implied that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. a method for diagnosing short-circuit between turns of a synchronous generator rotor winding based on a double coil, is characterized in that comprising the following steps: A. Install two U-shaped detection coils in the radial direction at a certain distance on the stator core section inside the synchronous generator. The output ports of the two U-shaped detection coils are connected in parallel with high-resistance resistors with the same resistance value, and the data acquisition device is used to collect The voltage signals of the output ports of the two U-shaped detection coils; B. During the operation of the generator, real-time processing is performed on the voltage signals at the exits of the two U-shaped detection coils collected by the data acquisition device, and the output voltages of the two U-shaped detection coils are differentiated or added. When the result exceeds the set value When the threshold is set, it is determined that the synchronous generator has an inter-turn short-circuit fault of the rotor winding; The U-shaped detection coil surrounds an iron core section of the stator of the synchronous generator in the radial direction, and the bottom of the U-shaped detection coil is located in the air gap between the stator and the rotor; during the rotor rotation, the stator iron yoke flows through the main magnetic flux, and the U-shaped detection coil Surrounding the stator iron yoke, therefore, the induced voltage of the U-shaped detection coil reflects the main magnetic field of the synchronous generator; when a turn-to-turn short circuit occurs in a magnetic pole winding of the synchronous generator, the magnetic field of the magnetic pole is significantly weakened, and the voltage induced by the U-shaped detection coil The signal can reflect this phenomenon, and then the short-circuit fault between turns of the rotor winding of the synchronous generator can be diagnosed. 2. The method for diagnosing short-circuit between turns of a synchronous generator rotor winding based on a double coil according to claim 1, wherein the distance between the two U-shaped detection coils is an integer multiple of the generator pole distance, and the integer Greater than or equal to 1 and less than or equal to the number of magnetic poles minus 1. 3. The method for diagnosing short-circuit between turns of a synchronous generator rotor winding based on a double coil according to claim 1, wherein: when the distance between the two U-shaped detection coils is an odd-numbered multiple of the generator pole pitch, The output voltages of the two U-shaped detection coils are added together; when the distance between the two U-shaped detection coils is an even multiple of the generator pole pitch, the output voltages of the two U-shaped detection coils are made difference. 4. The method for diagnosing inter-turn short-circuits of synchronous generator rotor windings based on double coils according to claim 3, wherein the output voltage of the two U-shaped detection coils is the result of difference or addition, and its size is the same as that of the rotor. The degree of short-circuit fault between turns of the winding is proportional. 5 . The method for diagnosing inter-turn short-circuits of synchronous generator rotor windings based on dual coils according to claim 4 , wherein the fault determination threshold is set to 0.15V. 6 .