Off-line detection device and method for turbonator rotor winding turn-to-turn short circuit

Abstract

The invention discloses a turbonator rotor winding turn-to-turn short circuit off-line detection device and method, and belongs to the technical field of generators. The device comprises an open iron core wound with a coil, a protective resistor, an alternating current power supply and a weak magnetic detection device. The method is based on the electromagnetic induction principle, an alternating magnetic field of a part of rotor windings of the cross-linked steam turbine generator is manufactured, a weak magnetic sensor is used for scanning notch leakage magnetic flux of a groove where the part of rotor windings are located, and when the notch leakage magnetic flux of a certain groove is abnormally large, it is judged that turn-to-turn short circuit happens to the rotor windings of the groove. According to the invention, whether the turn-to-turn short circuit occurs or not and the turn-to-turn short circuit degree can be accurately judged, the diagnosis method is simple to operate, clear in result and obvious in distinguishing, high diagnosis precision is achieved, and the method can be widely applied to off-line detection of the turn-to-turn short circuit fault of the rotor winding of the steam turbine generator.

Description

Technical Field

[0001] The invention relates to the technical field of generators, and in particular to an off-line detection device and method for inter-turn short circuit of a turbine generator rotor winding. Background Art

[0002] As one of the common electrical faults of steam turbine generators, the inter-turn short circuit of rotor windings is mainly caused by unreasonable manufacturing process, metal foreign matter intrusion, deep peak regulation, etc. The inter-turn short circuit fault is not obvious in the early stage of development, but as the fault develops, it will lead to the increase of rotor current, winding temperature, rotor mechanical vibration and other phenomena. These phenomena will affect the power production and service life of the unit, and even threaten the safe operation of the unit. Therefore, it is of great significance to propose a high-sensitivity and high-reliability steam turbine generator rotor winding inter-turn short circuit diagnosis method.

[0003] In recent years, with the increasing normalization of deep peak regulation of steam turbine generators, the rotor winding inter-turn short-circuit fault has shown an explosive growth trend, and the detection research of rotor winding inter-turn short-circuit is in urgent need of breakthroughs. At present, the existing detection technologies are divided into two types: online and offline. The online detection technology is to obtain the real-time operating parameters of the unit to make fault judgments, while the offline detection method is carried out during the shutdown stages such as the generator leaving the factory, handover, and major and minor repairs. Since the offline detection is carried out when the generator is stationary, the interference is small and the fault diagnosis sensitivity is high. The current main offline detection methods include: no-load short-circuit test method, DC resistance method, AC impedance and loss test method, two-pole voltage balance method, distributed voltage method, open transformer method, repeated pulse method and endoscope detection method. Among these detection methods, the no-load short-circuit test method, DC resistance method, AC impedance and loss test method, and two-pole voltage balance method do not have the function of fault location. The endoscope detection method is only applicable to short-circuit faults visible at the end, and cannot detect short circuits in the straight section of the winding and the invisible area at the end. Although the distributed voltage method can determine the fault location, the test operation is complicated, takes a long time, and there is a risk of metal foreign matter entering the rotor winding and damaging the inter-turn insulation. The open transformer method requires the injection of AC current into the generator excitation winding, which requires a large current and is difficult to implement for brushless excitation generators. Only the repeated pulse method has relatively excellent performance. In view of the current situation, it is urgent to develop a new offline detection method and device for rotor winding inter-turn short circuit that is simple to test, safe, reliable, and has fault location function. Summary of the invention

[0004] The purpose of the present invention is to provide an off-line detection device and method for inter-turn short circuit of a turbine generator rotor winding, which can solve the deficiencies of the prior art and improve the off-line diagnosis level of inter-turn short circuit fault of the turbine generator rotor winding.

[0005] To achieve the above-mentioned purpose, the present invention provides an off-line detection device for short circuit between turns of rotor winding of a steam turbine generator, comprising an open iron core wound with a coil and a weak magnetic detection device. When performing fault detection, the open iron core is tightly fitted with the tooth top surfaces of any two small teeth in a small tooth area of ​​the rotor. The weak magnetic detection device is placed at the slot where the excitation winding is located, which is linked by the closed magnetic circuit formed by the open iron core and the above-mentioned two small rotor teeth. The coil wound on the open iron core is connected in series with an AC power supply and a protective resistor to form a magnetic field generating circuit. The weak magnetic detection device includes a weak magnetic detection sensor and a weak magnetic field display device.

[0006] Preferably, the protective resistor is used to prevent the current of the magnetic field generating circuit from exceeding the tolerance current of the loop element.

[0007] Preferably, the AC power supply adopts a 50 Hz industrial frequency power supply.

[0008] An off-line detection method for inter-turn short circuit of a turbine generator rotor winding comprises the following steps: S1. During the test, the open core with the coil wound on it is closely fitted to the top surface of the small teeth of the rotor with a few slots between them. The AC power supply is used to inject AC current into the coil wound on the open core to form an alternating magnetic flux that interlinks the excitation winding. S2. Use a weak magnetic field detection sensor to closely contact the slot of the linked excitation winding, detect the leakage magnetic field in the radial and tangential directions of the slot, and observe the voltage displayed on the weak magnetic field display device. The voltage amplitude is proportional to the magnitude of the leakage magnetic field; S3. When the radial or tangential leakage magnetic field amplitude of a slot is significantly greater than that of other slots, it can be determined that a turn-to-turn short circuit fault occurs in the slot winding.

[0009] Preferably, in step S1, the magnitude of the coil current on the open core is set according to the magnetic flux density expected to be generated.

[0010] Preferably, in step S2, the weak magnetic field detection sensor is arranged at any position of the winding in the rotor slot spanned by the open core of the winding coil.

[0011] Therefore, the present invention adopts an off-line detection device and method for short-circuit between turns of a steam turbine generator rotor winding using the above structure, which has the following beneficial effects: The present invention can detect that the rotor winding has no current under normal circumstances, and in the case of an inter-turn short-circuit fault, the short-circuited winding will induce current, and the weak magnetic sensor can detect the increase in slot leakage magnetic field generated by the current, thereby determining and locating the fault. It can also accurately determine whether an inter-turn short circuit occurs and the degree of the inter-turn short circuit. The diagnostic method is simple to operate, the results are clear, the distinction is obvious, and a high diagnostic accuracy is achieved. It can be widely used in offline detection of inter-turn short circuit faults in steam turbine generator rotor windings.

[0012] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of a detection device and a rotor of an off-line detection device and method for inter-turn short circuit of a turbine generator rotor winding according to the present invention; Figure 2 It is a schematic diagram of a geometric model of a QFSN-300-2 type steam turbine generator rotor in an off-line detection device and method for inter-turn short circuit of a steam turbine generator rotor winding of the present invention; Figure 3 A distribution diagram of magnetic flux density on the surface of a turbine generator rotor of an off-line detection device and method for inter-turn short circuit of a turbine generator rotor winding according to the present invention; Figure 4 The figure is a time domain distribution diagram of the induced voltage of the detection coil of slot 32 of the steam turbine generator rotor of the offline detection device and method of the steam turbine generator rotor winding inter-turn short circuit of the present invention. DETAILED DESCRIPTION

[0014] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0015] Unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0016] Example The present invention provides an off-line detection device for short circuit between turns of rotor winding of a steam turbine generator, comprising an open iron core wound with coils, an AC power supply, a protective resistor and a weak magnetic field detection device. The open iron core winding wound with coils is connected in series with the AC power supply and the protective resistor to form an external circuit. The weak magnetic field detection device comprises a weak magnetic field detection sensor and a weak magnetic field display device. During operation, the two end surfaces of the open iron core wound with coils are tightly fitted with the tooth top surfaces of any two small teeth on one side of the rotor iron core. The weak magnetic field detection device is placed at the slot of the excitation winding where the closed magnetic circuit formed by the open iron core and the above two small rotor teeth intersects, and detects the slot leakage magnetic field of this part of the winding. The principle is as follows: Figure 1 As shown, whether a turn-to-turn short circuit occurs is determined based on the voltage difference corresponding to the magnetic induction intensity.

[0017] The function of the protection resistor is to prevent the current in the magnetic field generating circuit from exceeding the withstand current of the loop components.

[0018] The open core structure of the wound coil should match the rotor parameters to ensure that the open core fits tightly against the top surface of the rotor teeth.

[0019] The AC power supply can be selected as 50Hz power frequency.

[0020] The detection method in the present invention is based on the principle of electromagnetic induction, which produces an alternating magnetic field of a part of the rotor winding of the interlinked steam turbine generator, and uses a weak magnetic sensor to scan the slot leakage flux of the slot where this part of the rotor winding is located. When the slot leakage flux of a slot is abnormally large, it is determined that a short circuit occurs between the turns of the rotor winding in this slot.

[0021] An off-line detection and diagnosis method for inter-turn short circuit of a turbine generator rotor winding comprises the following steps: S1. During the test, the open core with the coil wound on it is closely fitted to the top surface of the small teeth of the rotor with a few slots between them. The AC power supply is used to inject AC current into the coil wound on the open core to form an alternating magnetic flux that interlinks the excitation winding. S2. Use a weak magnetic field detection sensor to closely contact the slot of the linked excitation winding, detect the leakage magnetic field in the radial and tangential directions of the slot, and observe the voltage displayed on the weak magnetic field display device. The voltage amplitude is proportional to the magnitude of the leakage magnetic field; S3. When the radial or tangential leakage magnetic field amplitude of a slot is significantly greater than that of other slots, it can be determined that a turn-to-turn short circuit fault occurs in the slot winding.

[0022] The weak magnetic field detection sensor is arranged at any position of the winding in the rotor slot spanned by the open core of the winding coil.

[0023] The open core winding current is generated according to the expected value.

[0024] When a short circuit occurs between turns of the rotor winding of a steam turbine generator, the rotor winding is divided into two parts, namely the short-circuited excitation winding and the residual excitation winding.

[0025] During offline testing, the turbine generator rotor is pulled out and the rotor winding is in an open circuit state. When there is no short circuit between the rotor winding turns, an AC voltage is applied to both ends of the open transformer winding to generate an alternating magnetic field, which passes through the rotor winding to generate an induced electromotive force. However, since the rotor winding is open, no induced current is generated and no induced magnetic field is generated.

[0026] When the turbine generator rotor winding has an inter-turn short circuit, a closed loop is formed inside the rotor winding. At this time, the alternating magnetic field generated by applying AC voltage to the open transformer winding will generate an induced electromotive force and induced current in the rotor winding, and then generate an induced magnetic field, which will be detected by the weak magnetic sensor.

[0027] In order to verify this method, the present invention uses a QFSN-300-2 steam turbine generator as the research object, uses Maxwell software to establish a two-dimensional simulation model of the generator rotor, and performs finite element simulation analysis. The basic parameters of the generator are shown in Table 1, and the established two-dimensional model of the generator is shown in Table 2. Figure 2 ,The numbers in the figure represent the slot numbers.

[0028] Table 1

[0029] In order to set the short-circuit fault between the rotor winding turns, it is necessary to use a switch to control the application of the short-circuit turns of the rotor winding. Therefore, the generator model built with Maxwell software is imported into Simplorer software, the peripheral circuit and control part of the generator are built, and the field-circuit coupling joint simulation is carried out.

[0030] This turn-to-turn short-circuit detection method is an offline detection, so the rotor is in a stationary state, and the two core sections of the open transformer are attached to the top surfaces of the small teeth on both sides of slot 1. A 5V AC voltage is applied to both ends of the coil wound by the open transformer.

[0031] The normal, 2-turn short-circuit, 4-turn short-circuit and 6-turn short-circuit operating conditions are simulated respectively to obtain the magnetic flux density distribution diagram on the surface of the turbine generator rotor, as shown in Figure 3 As shown, the horizontal axis is the slot number. It can be seen that compared with the rotor surface flux density under normal working conditions, the rotor surface flux density under inter-turn short-circuit conditions is significantly increased, and increases with the increase of the number of short-circuit turns. The difference between the normal working condition and the short-circuit condition near the target slot No. 32 is obvious, which can be used as a criterion for distinguishing whether the rotor winding is short-circuited between turns. The flux density at the slot No. 32 of the rotor under the short-circuit state of each turn is shown in Table 2. A detection coil is placed at slot No. 32 where a weak magnetic detection sensor is deployed, and the resulting induced voltage time domain diagram is shown in the following figure. Figure 4 shown.

[0032] Table 2

[0033] In summary, when a turn-to-turn short circuit fault occurs in the generator rotor winding, the magnetic field detected by the weak magnetic sensor is significantly greater than that in the normal state of the rotor winding. Therefore, this method can effectively detect the turn-to-turn short circuit fault of the rotor winding.

[0034] Therefore, the present invention adopts the above-mentioned offline detection device and method for inter-turn short circuit of steam turbine generator rotor winding, which can accurately determine whether inter-turn short circuit occurs and the degree of inter-turn short circuit. The diagnostic method is simple to operate, the results are clear, the distinction is obvious, and a high diagnostic accuracy is achieved. It can be widely used in offline detection of inter-turn short circuit faults in steam turbine generator rotor windings.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. An off-line detection device for short-circuit between turns of a turbine generator rotor winding, characterized in that: It includes an open iron core wound with a coil and a weak magnetic detection device. When performing fault detection, the open iron core is tightly fitted with the tooth top surfaces of any two small teeth in a small tooth area of ​​the rotor. The weak magnetic detection device is placed in a slot where the excitation winding is located and the closed magnetic circuit formed by the open iron core and the above two small rotor teeth intersects. The coil wound on the open iron core is connected in series with an AC power supply and a protective resistor to form a magnetic field generating circuit. The weak magnetic detection device includes a weak magnetic detection sensor and a weak magnetic field display device.

2. The off-line detection device for inter-turn short circuit of a turbine generator rotor winding according to claim 1, characterized in that: The protection resistor is used to prevent the current of the magnetic field generating circuit from exceeding the withstand current of the loop element.

3. The off-line detection device for inter-turn short circuit of a turbine generator rotor winding according to claim 1, characterized in that: The AC power source adopts a 50 Hz industrial frequency power source.

4. An off-line detection method for inter-turn short circuit of a turbine generator rotor winding is applied to an off-line detection device for inter-turn short circuit of a turbine generator rotor winding according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. During the test, the open core with the coil wound on it is closely fitted to the top surface of the small teeth of the rotor with a few slots between them. The AC power supply is used to inject AC current into the coil wound on the open core to form an alternating magnetic flux that interlinks the excitation winding. S2. Use a weak magnetic field detection sensor to closely contact the slot of the linked excitation winding, detect the leakage magnetic field in the radial and tangential directions of the slot, and observe the voltage displayed on the weak magnetic field display device. The voltage amplitude is proportional to the magnitude of the leakage magnetic field; S3. When the radial or tangential leakage magnetic field amplitude of a slot is significantly greater than that of other slots, it can be determined that a turn-to-turn short circuit fault occurs in the slot winding.

5. The off-line detection method for inter-turn short circuit of a turbine generator rotor winding according to claim 4, characterized in that: In step S1 , the magnitude of the coil current on the open core is set according to the magnetic flux density expected to be generated.

6. The off-line detection device and method for inter-turn short circuit of a turbine generator rotor winding according to claim 4, characterized in that: In step S2, a weak magnetic field detection sensor is arranged at any position of the winding in the rotor slot spanned by the open core of the winding coil.

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