Generator stator core magnetization test system

Abstract

The utility model relates to a generator stator core magnetization test system, and relates to the technical field of generator detection. The method comprises a target power supply, a target transformer, an excitation module and a measurement module, wherein the target transformer is connected with the target power supply, the excitation module is connected with the target transformer, and the measurement module is connected with the excitation module and a to-be-measured generator stator core. By adopting the method, the safety of the detection process of the generator stator core can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of generator detection, and particularly to a magnetization test system for a generator stator core. Background Art

[0002] The stator core of a large-capacity generator plays an important role in fixing the stator winding and forming the magnetic circuit of the generator. It is an important component of the generator. The quality of the stator core directly affects the safe operation of the entire generator. When the generator is operating, if the insulation between the silicon steel sheets of the core is damaged and a short-circuit fault occurs, a fault current path will be formed in the axial lamination of the core, the positioning ribs or the machine base, resulting in an increase in eddy current loss and an increase in the core temperature. If the defect is not resolved in a timely and effective manner, the heat generated by the eddy current will further damage the insulation between the silicon steel sheets of the core, causing the silicon steel sheets to burn or melt, and even damaging the stator winding in severe cases, leading to serious accidents. Therefore, during the factory test of the generator, before and after partially or completely replacing the stator winding, and when damage or other defects are found in the stator core, it is necessary to conduct a magnetization test on the generator stator core to check the quality of the core.

[0003] In traditional technologies, there are methods for magnetization testing of the core by directly exciting with high voltage and methods for detecting core defects with electromagnets. However, the current methods for detecting the generator stator core have problems with poor safety. Summary of the Utility Model

[0004] Based on this, in view of the above technical problems, it is necessary to provide a magnetization test system for a generator stator core that can improve the safety of the detection process for the generator stator core.

[0005] An embodiment of the present application provides a magnetization test system for a generator stator core, the system includes:

[0006] A target power supply; the target power supply is a power supply with a switching function and a voltage regulation function;

[0007] A target transformer; the target transformer is connected to the target power supply, and the target transformer is used to realize the transformation of the output voltage under the condition of compensating for reactive power;

[0008] An excitation module; the excitation module is connected to the target transformer, and the excitation module is used to generate an excitation magnetic field according to the voltage information output by the target transformer to test the generator stator core to be tested arranged in the excitation magnetic field;

[0009] Measurement module; the measurement module is respectively connected to the excitation module and the stator core of the generator to be measured. The measurement module is used to measure the temperature information of the stator core of the generator and the power loss information corresponding to the stator core of the generator. The temperature information and the power loss information are used to determine whether the stator core of the generator meets the quality requirements.

[0010] In one embodiment, the measurement module includes:

[0011] Measurement coil; the measurement coil is arranged at a position orthogonal to the excitation coil in the excitation module.

[0012] In one embodiment, the measurement module further includes:

[0013] Voltage transformer; the voltage transformer is connected to the measurement coil, and the voltage transformer is used to measure the induced voltage of the measurement coil;

[0014] Current transformer; the current transformer is sleeved on the excitation coil, and the current transformer is used to measure the excitation current of the excitation coil.

[0015] In one embodiment, the measurement module further includes:

[0016] Loss tester; the loss tester is respectively connected to the voltage transformer and the current transformer, and is used to determine the power loss information corresponding to the stator core of the generator according to the induced voltage and the excitation current.

[0017] In one embodiment, the measurement module includes:

[0018] Infrared thermal imager; the infrared thermal imager is used to measure the temperature information of the stator core of the generator.

[0019] In one embodiment, the measurement module includes:

[0020] Display module; the display module is used to display the temperature information.

[0021] In one embodiment, the measurement module includes:

[0022] Display module; the display module is used to display the induced voltage, the excitation current and the power loss information.

[0023] In one embodiment, the target transformer includes:

[0024] Compensation transformer; the compensation transformer is used to transform the voltage signal output by the target power supply into an excitation voltage signal that meets the requirements for establishing a magnetic field in the excitation coil.

[0025] In one embodiment, the target transformer further includes:

[0026] At least two shunt compensation capacitors; the compensation capacitors are used to compensate for the inductive reactive power generated when the voltage is transformed by the compensation transformer.

[0027] In one embodiment, the target power supply includes:

[0028] A test power supply; the test power supply is used to output an alternating current signal for testing;

[0029] A voltage regulator; the voltage regulator is connected to the target transformer, and the voltage regulator is used to adjust the magnitude of the output voltage signal;

[0030] A power switch; the power switch is respectively connected to the test power supply and the voltage regulator, and the power switch is used to disconnect and connect the test power supply.

[0031] In the above generator stator core magnetization test system, a compensation capacitor bank is used to compensate for the inductive reactive power in the core magnetization test, greatly reducing the output power and output current of the test power supply; the voltage regulator is used to boost the excitation voltage from zero, and the excitation voltage can slowly rise from zero to the test voltage, without generating an excitation inrush current similar to direct closing of a high voltage, without impacting the load on the power supply side and without affecting the operation of the load on the power supply side, improving the safety of the core magnetization test. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a structural block diagram of a generator stator core magnetization test system in one embodiment;

[0034] Figure 2 It is a schematic diagram of the principle of a generator stator core magnetization test system in one embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] To facilitate understanding of the present application, the present application will be described more comprehensively below with reference to the relevant drawings. Embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0037] It can be understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0038] It can be understood that for "connection" in the following embodiments, if there is transmission of electrical signals or data between the connected circuits, modules, units, etc., it should be understood as "electrically connected", "communicatively connected", etc.

[0039] It can be understood that "at least one" means one or more, and "a plurality" means two or more. "At least part of an element" means part or all of the element.

[0040] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprise / include" or "have" etc. specify the presence of the stated features, wholes, steps, operations, components, parts or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0041] An embodiment of this application provides a magnetization test system for a generator stator core, as Figure 1 shown. The magnetization test system for the generator stator core includes:

[0042] A target power supply 101, a target transformer 102, an excitation module 103 and a measurement module 104, wherein the target transformer 102 is connected to the target power supply 101, the excitation module 103 is connected to the target transformer 102, and the measurement module 104 is respectively connected to the excitation module 103 and the generator stator core to be tested 100; the generator stator core to be tested 100 is arranged in the excitation magnetic field generated by the excitation module 103.

[0043] Among them, the target power supply is a power supply with a switching function and a voltage regulation function; the target transformer is connected to the target power supply, and the target transformer is used to transform the output voltage under the condition of compensating for inductive reactive power.

[0044] Among them, the excitation module is connected to the target transformer, and the excitation module is used to generate an excitation magnetic field according to the voltage information output by the target transformer to test the stator core of the generator under test arranged in the excitation magnetic field.

[0045] Among them, the measurement module is respectively connected to the excitation module and the stator core of the generator under test. The measurement module is used to measure the temperature information of the stator core of the generator and the corresponding power loss information of the stator core of the generator. The temperature information and the power loss information are used to determine whether the stator core of the generator meets the quality requirements.

[0046] Exemplarily, the maximum temperature rise of the core tooth part or yoke part is not greater than 25K, that is, the difference between the final temperature and the initial temperature of the core at the same position before the end of the test is not greater than 25K. The maximum temperature difference of the core tooth part or yoke part is not greater than 15K, that is, the difference between the highest temperature and the lowest temperature at different positions of the core at the same moment is not greater than 15K. If the temperature rise, temperature difference and unit loss value of the core all meet the above requirements, it is determined that the quality of the stator core of the generator is good. If one of the temperature rise, temperature difference and unit loss value of the core does not meet the requirements, it is determined that the quality of the stator core of the generator is abnormal, and it is necessary to further check whether there are defects such as looseness and insulation damage in the core and perform relevant treatments.

[0047] In the above generator stator core magnetization test system, a compensation capacitor bank is used to compensate for the inductive reactive power in the core magnetization test, greatly reducing the output power and output current of the test power supply; the zero-position boost excitation of the voltage regulator is used, and the excitation voltage can slowly rise from zero to the test voltage, without generating an excitation inrush current similar to direct closing of high voltage, without impacting the load on the power supply side and without affecting the operation of the load on the power supply side, improving the safety of the core magnetization test.

[0048] In one embodiment, the measurement module includes: a measurement coil; the measurement coil is arranged at a position orthogonal to the excitation coil in the excitation module.

[0049] Exemplarily, the measurement coil uses a PVC insulated flexible wire, with 1 turn, a length of 30m, which can meet the requirement of winding one turn of the measurement winding through the core of a 1000MW generator (the stator core is about 13 meters long). The measurement coil is arranged at a position orthogonal to the excitation coil, and the alternating magnetic flux maximally vertically passes through the measurement winding, making the measured value of the excitation voltage accurate and reliable. Both ends of the measurement coil are connected to the primary terminals of the voltage transformer.

[0050] In this embodiment, by arranging a measurement coil in the measurement module and disposing the measurement coil at a position orthogonal to the excitation coil in the excitation module, the accuracy of the measured value of the excitation voltage is improved.

[0051] In one embodiment, the measurement module further includes: a voltage transformer; the voltage transformer is connected to the measurement coil, and the voltage transformer is configured to measure the induced voltage of the measurement coil; a current transformer; the current transformer is sleeved on the excitation coil, and the current transformer is configured to measure the excitation current of the excitation coil.

[0052] Among them, the voltage transformer is configured to measure the induced voltage of the measurement coil, and its accuracy class is 0.5. The secondary output terminal is connected to the voltage input terminal of the loss tester. The magnetic flux density of the iron core at different moments can be calculated from the measured voltage value.

[0053] Among them, the current transformer is a through-core current transformer. The through-core current transformer is sleeved into the excitation coil and is used to measure the excitation current of the excitation coil. Its accuracy class is 0.5, and the secondary output terminal is connected to the current input terminal of the loss tester.

[0054] In this embodiment, by arranging a voltage transformer and a current transformer in the measurement module, the measurement of the induced voltage of the measurement coil and the excitation current of the excitation coil is realized, which is convenient for observing the test process and calculating the power loss.

[0055] In one embodiment, the measurement module further includes: a loss tester; the loss tester is respectively connected to the voltage transformer and the current transformer, and is configured to determine the power loss information corresponding to the generator stator iron core according to the induced voltage and the excitation current.

[0056] Among them, the loss tester is configured to measure the power loss of the stator iron core.

[0057] In this embodiment, by arranging a loss tester in the measurement module, the measurement of the power loss of the stator iron core is realized.

[0058] In one embodiment, the measurement module includes: an infrared thermal imager; the infrared thermal imager is configured to measure the temperature information of the generator stator iron core.

[0059] Among them, the infrared thermal imager is an infrared thermal imaging device, which is used to measure the initial temperature of the stator iron core before boosting voltage, and is also used to measure the temperature of each position of the iron core during the test, including the highest temperature, the average temperature and the lowest temperature, and focuses on monitoring the positions with higher iron core temperature.

[0060] In this embodiment, by arranging an infrared thermal imager in the measurement module, the measurement of the iron core temperature before and during the test is realized.

[0061] In one embodiment, the measurement module includes: a display module; the display module is used to display temperature information.

[0062] In this embodiment, a display module is provided in the measurement module to display temperature information, which is convenient for presenting the temperature information to the tester.

[0063] In one embodiment, the measurement module includes: a display module; the display module is used to display induced voltage, exciting current, and power loss information.

[0064] In this embodiment, a display module is provided in the measurement module to display induced voltage, exciting current, and power loss information, which is convenient for presenting information such as voltage, current, and loss to the tester.

[0065] In one embodiment, the target transformer includes: a compensation transformer; the compensation transformer is used to transform the voltage signal output by the target power supply into an exciting voltage signal that meets the requirement for establishing a magnetic field in the exciting coil.

[0066] Among them, the compensation transformer is a single-phase oil-immersed self-cooled transformer, and its output terminal is designed with three sets of taps of 2 kV, 4 kV, and 6 kV. The 2 kV and 4 kV output terminals are used to further increase the output voltage of the voltage regulator to reach the exciting voltage value required for the exciting coil to establish a magnetic field. The 6 kV output terminal is used for the operation of the compensation capacitor bank.

[0067] In this embodiment, by providing a compensation transformer in the target transformer to transform the voltage signal output by the target power supply into an exciting voltage signal that meets the requirement for establishing a magnetic field in the exciting coil, while ensuring safety, the experiment can be carried out.

[0068] In one embodiment, the target transformer further includes: at least two parallel compensation capacitors; the compensation capacitors are used to compensate for the inductive reactive power generated when the compensation transformer transforms the voltage.

[0069] Among them, the compensation capacitor bank is composed of 10 parallel-connected capacitors of the same type with a rated capacity of 100 kVar. The parallel use of 10 capacitors can compensate for 1000 kVar of inductive reactive power, which can greatly reduce the output power and output current of the test power supply. The rated voltage of the compensation capacitor bank is 6 kV, and it is connected in parallel to the 6 kV output terminal of the compensation transformer during the test. During the test, as long as the appropriate number of capacitor banks is selected and the capacitance value is compensated properly, the test power supply only needs to provide a power of several hundred kilowatts equivalent to the stator core loss.

[0070] In this embodiment, by providing compensation capacitors in the target transformer to compensate for the inductive reactive power generated when the compensation transformer transforms the voltage, while ensuring safety, the experiment can be carried out.

[0071] In one embodiment, the target power supply includes: a test power supply; the test power supply is used to output an alternating current signal for testing; a voltage regulator; the voltage regulator is connected to the target transformer and is used to adjust the magnitude of the output voltage signal; a power switch; the power switch is respectively connected to the test power supply and the voltage regulator, and the power switch is used to disconnect and connect the test power supply.

[0072] Among them, the test power supply is taken from the in-plant 380V industrial frequency AC power supply. After compensating for inductive reactive power by a compensation capacitor bank, the power supply capacity is generally below 400 kVA. Only two phases are used during the test.

[0073] Among them, the voltage regulator is a dry-type air-cooled induction voltage regulator, which is used to adjust the magnitude of the output excitation voltage.

[0074] Among them, the power switch is an air switch. The air switch is used to disconnect and connect the test power supply. The two outgoing terminals of the air switch are connected to the input end of the voltage regulator through a non-armored connection cable without steel tape, and the output end of the voltage regulator is connected to the input end of the compensation transformer through a non-armored connection cable without steel tape.

[0075] In this embodiment, by setting up the test power supply, the voltage regulator and the power switch to form a target power supply with switching and voltage regulation functions, the stable progress of the test is ensured.

[0076] In one embodiment, the stator core of a large-capacity generator is laminated with sector-shaped non-oriented cold-rolled silicon steel sheets with high magnetic permeability, low loss, and a thickness of 0.35 - 0.50 mm. Epoxy insulating paint is coated on both surfaces of the silicon steel sheets, and adjacent silicon steel sheets are insulated from each other. Axially, the stator core is penetrated by high-strength non-magnetic steel through bolts with ground insulation, and is tightly pressed into a solid core body by nuts through the pressure fingers, pressure rings and segmented pressing plates at both ends. The stator core plays an important role in fixing the stator winding and forming the magnetic circuit of the generator, and is an important component of the generator. Therefore, the quality of the stator core directly affects the safe operation of the entire generator.

[0077] When the generator is running, the main magnetic flux rotates with the rotor. This alternating magnetic field generates hysteresis loss and eddy current loss in the iron core, which are collectively called core loss. If the insulation between the silicon steel sheets of the iron core is damaged and a short-circuit fault occurs, a fault current path will be formed in the axial laminations of the iron core, the positioning ribs or the machine base, resulting in an increase in eddy current loss and a rise in the iron core temperature. If the defect is not resolved in a timely and effective manner, the heat generated by the eddy current will further damage the insulation between the silicon steel sheets of the iron core, causing the silicon steel sheets to burn or melt, and even seriously damaging the stator winding in severe cases, leading to serious accidents. Therefore, during the factory test of the generator, before and after partially or completely replacing the stator winding, and when damage or other defects are found in the stator core, it is necessary to conduct a magnetization test on the stator core of the generator to check the quality of the iron core.

[0078] At present, there are two commonly used methods for the magnetization test of the generator stator core: the traditional high-voltage direct excitation core magnetization test method and the ELCID (Electromagnetic Core Imperfection Detector) method. The traditional high-flux core magnetization test method is to wind multiple turns of excitation coils around the core and pass a large power-frequency current through them to generate an alternating magnetic flux of 1.0T - 1.4T in the core. Eddy currents and hysteresis losses are generated in the core under the action of the alternating magnetic flux. If the insulation between the core laminations is damaged, larger local eddy currents will be generated, causing the core temperature to rise rapidly. Then, an infrared imaging device is used to detect the surface temperature of the stator core to find the surface overheating points. The traditional high-flux core magnetization test uses the 6kV or 10kV working section busbar in the power plant as the test power source, and the test power source has a large capacity. During the test, direct closing excitation is carried out at high voltage, and the test voltage is high, which can simulate the operation of the generator, and the test results are intuitive and clear.

[0079] The ELCID method is a new low-voltage and small-current core defect detection method. It winds 1 excitation coil around the central axis position inside the stator core cavity, and a small excitation current is passed through the excitation coil to make the rated magnetic flux of 4% evenly distributed circumferentially in the core. If the insulation between the core laminations is damaged, the defective silicon steel sheet and the positioning ribs on the outer side of the core jointly form a closed loop, and the alternating excitation magnetic flux will induce eddy current in the fault area loop. By using a Chattock magnetometer to bridge the surfaces of two adjacent stator core teeth, the magnetic potential difference generated by the fault current can be measured, thereby realizing the test of the fault current and the positioning of the fault point. Generally, it is considered that when the value of the stator core fault current is greater than 100mA, the insulation between the core laminations is abnormal. Compared with the traditional high-flux magnetization test method, the ELCID method has a smaller excitation capacity, and the test power source capacity only needs several kilovolt-amperes, which is very easy to obtain in the power plant. Due to the low voltage and small current during the test process, the test process is safe and controllable. In addition, the detection equipment of the ELCID method is light and easy to carry, and has a strong detection ability for the surface defects of the core teeth. It has been applied in some foreign power production and manufacturing units.

[0080] The traditional high-flux core magnetization test has the following problems:

[0081] (1) The test power source has a very large capacity. The stator core of a large generator is a highly inductive component with a large inductance. To establish the required magnetic field in the core, hundreds or even thousands of kilovolt-amperes of reactive power need to be provided, so the required test power source capacity is very large, reaching the megavolt-ampere level. The test power source for the high-flux core magnetization test is taken from the 6kV or 10kV working section busbar in the power plant. In order to keep the excitation voltage stable and the test power source from losing power, other loads on the power source side often need to be disconnected from the busbar to ensure that the core magnetic flux density remains at the specified test value.

[0082] (2) High-voltage direct-switching excitation results in a very large inrush current at the moment of switching. The magnetization test of the high-flux iron core is to directly conduct the breaker closing excitation at a voltage of 6 kV or 10 kV. At the moment of closing, the excitation coil is extremely likely to generate an inrush current 5 to 7 times the rated current. Such a large current load has a great impact on the loads on the 6 kV busbar. It not only easily causes malfunctions of relay protection devices such as instantaneous overcurrent protection and overcurrent protection on the power supply line side and the power supply of the security section, but may also cause sudden changes in the voltage of the upper-level line, affecting the normal operation of other electrical equipment.

[0083] (3) The test is highly dangerous. The high-voltage excitation cable is laid from the 6 kV working section to the generator platform. The cable laying path is relatively long, the test monitoring range is very large, and it is difficult to monitor the test process. If it is necessary to further check the iron core fault point, the test personnel have to enter the generator stator cavity where the 10 kV excitation cable is wound, and the risk of electric shock to the test personnel is high.

[0084] (4) The workload of winding the excitation winding is large, time-consuming and laborious. Due to the high excitation voltage, the number of turns of the excitation cable wound along the stator iron core is also large. In addition, the large excitation current results in a large cross-sectional area of the excitation cable, heavy cable weight, and it takes many people to work for a long time to wind the excitation cable.

[0085] With more and more generators with a capacity of 600 MW, 1000 MW and above put into operation, the capacity of the excitation power supply required for the magnetization test of the stator iron core is getting larger and larger, the preparatory work before the test is increasing, and the test conditions are getting higher and higher. This makes the operation of the traditional iron core magnetization test more difficult and difficult to implement on site.

[0086] The ELCID method has the following problems:

[0087] (1) The detection result is not intuitive enough. The detection result of the ELCID method is the fault current, which cannot directly reflect the temperature rise of the iron core, nor can it detect the power loss of the iron core.

[0088] (2) The detected data is prone to distortion and the accuracy of the detection result is not high. Since the excitation cable is suspended at the central position inside the stator core, restricted by the spatial position inside the core, when operating personnel use a handheld Chattock magnetometer trolley for testing, they have to lie prone inside the stator core, making movement and operation very inconvenient, which may have a certain impact on the measured value of the fault point current and the measured value of its accurate position. Additionally, the speed of the test trolley's advancement also affects the acquisition of data signals. If the speed is too fast, it is easy to miss information acquisition, resulting in data distortion. On the other hand, the surface of the stepped teeth at the slot openings on both sides of the generator is uneven, which can cause a sudden change in the fault current when moving from one step to the next. Moreover, many generator stator cores are equipped with windshields, which pose difficulties for continuously moving the Chattock magnetometer trolley. All these factors reduce the accuracy of the ELCID method.

[0089] (3) The degree of recognition is not high and the detection result has no national or power standard basis. Although the ELCID method can detect defects on the surface of the iron core, its ability to detect defects deep inside the iron core is poor. It is still unclear what the corresponding relationship is between the magnitude of the fault current and the temperature or temperature rise limit in the traditional iron core magnetization test. More application experience needs to be accumulated and further research and summary are still required. After detecting that the fault current exceeds the standard using the ELCID method, in order to identify whether the stator iron core can continue to operate with the detected defect location, it is generally necessary to supplement and conduct the traditional high-flux iron core magnetization test. Finally, the insulation condition of the stator iron core is determined based on the results of the high-flux magnetization test. There have even been cases in practice where the fault current exceeded the standard but the iron core magnetization test was qualified, wasting a large amount of time, manpower, and costs in vain.

[0090] (4) The instrument cost is expensive. ELCID belongs to a precision measuring instrument, with a quoted price of about more than 1.2 million yuan, which is expensive.

[0091] In view of the above-mentioned shortcomings and problems existing in the traditional high-flux iron core magnetization test method and the emerging low-flux ELCID method, a voltage regulator zero-position boost excitation iron core magnetization test system and method are designed, taking the power loss, temperature rise, and temperature difference of the iron core as the detection objects to judge the quality of the generator stator iron core.

[0092] Based on this, the embodiment of the present application provides a generator stator iron core magnetization test system. For the convenience of understanding by those skilled in the art, Figure 2 a schematic diagram of the principle of the generator stator iron core magnetization test system is provided. Below, with reference to Figure 2 , a specific embodiment is used to describe the generator stator iron core magnetization test system in detail. It should be understood that the following description is only an exemplary illustration and not a specific limitation of the application.

[0093] The generator stator core magnetization test system provided by this application is applied to products of large-capacity generators with a capacity of 6 MW to 1000 MW. The generator stator core magnetization test is a test that applies a certain magnetic flux density to the generator core and analyzes the quality of the core by detecting the temperature and power loss of the core.

[0094] A large-capacity generator stator core magnetization test system is as Figure 2 shown. It includes: test power supply 1, power cable 2, air switch 3, connecting cable 4, voltage regulator 5, connecting cable 6, compensating transformer 7, current transformer 8, excitation coil 9, generator stator core 10, measuring coil 11, voltage transformer 12, power loss tester 13, and compensating capacitor bank 14.

[0095] The generator stator core magnetization test system provided by this application specifically includes:

[0096] (1) The test power supply 1 is taken from the in-plant 380V industrial frequency AC power supply. After compensating for inductive reactive power by the compensating capacitor bank 14, the power supply capacity is generally below 400 kVA. Only two phases are used during the test. As Figure 2 shown, phase A and phase C are used.

[0097] (2) The power cable 2 is composed of two 380V armored cables with a specification of 3×Ф185mm2 (phase wires) + Ф95mm2 (neutral wire). The cross-sectional area of the power cable is large to avoid excessive voltage drop of the power supply during the test. One end of the power cable 2 is connected to the 380V industrial frequency AC power supply in the power plant, and the other end is connected to the incoming line terminal of the air switch 3. To avoid serious heating of the armored layer after the power cable passes through a large current, two phase wires (such as phase A and phase C) of the first power cable 2 and two wires of different colors (phase B and 0 wire) of the second power cable 2 are connected in parallel as one phase to one incoming line terminal of the air switch 3, and the remaining phase wires are connected to the other incoming line terminal of the air switch 3. That is, the cores of the same armored cable are divided into 2 groups, one group flowing in current and the other group flowing out current, to minimize the induced magnetic flux and loss on the armor as much as possible.

[0098] (2) The air switch 3 is used to disconnect and connect the test power supply. The two outgoing line terminals of the air switch are connected to the input end of the voltage regulator 5 through a non-steel tape armored connecting cable 4, and the output end of the voltage regulator 5 is connected to the input end of the compensating transformer 7 through a non-steel tape armored connecting cable 6.

[0099] (4) The voltage regulator 5 is a dry-type air-cooled induction voltage regulator, which is used to adjust the magnitude of the output excitation voltage.

[0100] (3) The compensation transformer 7 is a single-phase oil-immersed self-cooled transformer, and its output terminal is designed with three sets of taps of 2 kV, 4 kV, and 6 kV. The 2 kV and 4 kV output terminals are used to further increase the output voltage of the voltage regulator 5 to reach the excitation voltage value required for the excitation coil 9 to establish a magnetic field. The 6 kV output terminal is used for the operation of the compensation capacitor bank 14.

[0101] (4) The compensation capacitor bank 14 is composed of 10 parallel capacitors of the same type with a rated capacity of 100 kVar. The parallel use of 10 capacitors can compensate for 1000 kVar of inductive reactive power, which can greatly reduce the output power and output current of the test power supply 1. The rated voltage of the compensation capacitor bank 14 is 6 kV, and it is connected in parallel to the 6 kV output terminal of the compensation transformer 7 during the test. During the test, as long as the appropriate number of capacitor banks is selected and the capacitance value is compensated appropriately, the test power supply 1 only needs to provide a power of several hundred kilowatts equivalent to the stator core loss.

[0102] Method for obtaining the number n of compensation capacitors: From the equivalent circuit of the core magnetization test with capacitance compensation, we get , where U1 represents the power supply output voltage, I1 represents the power supply output current, U2 represents the capacitor voltage, I2 represents the capacitor current, U3 represents the excitation coil voltage, I3 represents the excitation coil current, R represents the equivalent resistance of the core loss, L represents the equivalent inductance of the excitation coil, and C represents the capacitor capacitance. When , the power supply output capacity is the smallest. That is, from the equivalent circuit of the core magnetization test without capacitance compensation, we can get , and n is rounded to the nearest integer.

[0103] (4) The excitation coil 9 is composed of 6 single-core non-armored flexible cables with a length of 30 meters and a cross-sectional area of 70 mm2. Even when several hundred amperes of large current flows through the excitation cable during the test, there is no situation of armored cable heating, which greatly reduces the temperature of the excitation cable and avoids the influence of the cable itself heating on the core loss value. The number of turns of the excitation coil is taken as 1 - 2 turns. According to the length of the generator stator core 10, the excitation cables are freely combined into multiple turns or multiple groups of excitation coils. One end of the excitation cable is connected to the output terminal of the compensation transformer 7, and the other end passes through the current transformer 8 and then is connected to the other output terminal of the compensation transformer 7. The excitation cables are evenly wound around the circumference of the generator stator core 10, so that the alternating magnetic flux is evenly distributed in the stator core. The excitation cables are supported by insulating rods in the stator cavity to isolate them from the stator core and avoid the influence of the excitation cable itself heating on the temperature measurement of the stator core.

[0104] (5) The through-type current transformer 8 is sleeved on the excitation coil 9 and is used to measure the excitation current of the excitation coil 9. Its accuracy class is 0.5, and the secondary output terminal is connected to the current input terminal of the power loss tester 13.

[0105] (6) The measuring coil 11 uses a polyvinyl chloride insulated soft wire, with 1 turn and a length of 30m, which can meet the requirements of a 1000MW generator core (stator core is about 13 meters long) to pass through one turn of the measuring winding. The measuring coil 11 is arranged at a position orthogonal to the excitation coil 9, and the alternating magnetic flux passes through the measuring winding vertically to the maximum extent, so that the excitation voltage measurement value is accurate and reliable. The two ends of the measuring coil 11 are connected to the primary terminal of the voltage transformer 12. The voltage transformer 12 is an electromagnetic voltage transformer.

[0106] (7) The voltage transformer 12 is used to measure the induced voltage of the measuring coil 11. Its accuracy level is 0.5, and its secondary output terminal is connected to the voltage input terminal of the power loss tester 13. The magnetic flux density of the core at different times can be calculated from the measured voltage value.

[0107] (8) The power loss tester 13 is used to measure the power loss of the stator core and display the current of the excitation coil 9 and the voltage of the measuring coil 11.

[0108] The implementation process of the generator stator core magnetization test system provided in this application includes:

[0109] (1) Calculate the excitation voltage UW1. The excitation voltage UW1 is given by the induced electromotive force formula Calculated. In the formula, f represents the excitation current frequency; B represents the core magnetic flux density, B is 1T; W1 represents the number of turns of the excitation winding, W1 is 1-2; S represents the cross-sectional area of ​​the stator core, which is provided by the motor manufacturer or obtained by calculation.

[0110] (2) Calculate the measured voltage UW2. The measured voltage UW2 is calculated by the formula Calculated. Where W1 represents the number of turns of the excitation coil, and W2 represents the number of turns of the measuring winding coil.

[0111] (3) Calculate the number of compensation capacitors n. n is given by the expression The calculated value n is rounded to the nearest integer.

[0112] (4) According to the number of turns of the excitation winding W1 and the number of compensation capacitors n, each system and each test equipment shall be Figure 2 The connection is complete.

[0113] (5) For water-cooled generators, the cooling water system must be stopped to prevent the cooling water from taking away the heat of the stator core and affecting the accuracy of the test data.

[0114] (5) Use an infrared thermal imager to measure the initial temperature of the stator core before boosting the voltage.

[0115] (6) Close the air switch 3, check whether the zero position of the voltage regulator 5 and the direction of the cooling fan of the voltage regulator 5 are correct, and start the test after confirming that the test wiring is correct.

[0116] (7) Slowly boost the excitation of the voltage regulator 5 to zero. During the boosting process, carefully observe the current and voltage in the test circuit, and use an infrared thermal imager to observe the test circuit. If any abnormal conditions such as overheating are found at the line joints, immediately reduce the voltage for treatment. If all meters show normal, continue to boost the excitation of the voltage regulator 5. When the measured voltage monitored by the power loss tester 13 reaches the test value, the magnetic flux density of the stator core reaches the magnetic density value required by the test, and the test officially starts timing.

[0117] (8) The magnetization test of the stator core lasts for 90 minutes. Record the data of the power loss tester 13 every 15 minutes, including the excitation current, the excitation measured voltage, and the total core loss value. And use an infrared thermal imager to measure the temperature at each position of the core, including the highest temperature, the average temperature, and the lowest temperature, with a focus on monitoring the positions with higher core temperatures.

[0118] (9) Before the end of the test, mark the specific positions with higher stator core temperatures, and then slowly reduce the output voltage of the voltage regulator 5 to zero.

[0119] (10) Disconnect the air switch 3, and then disconnect the switch of the upper-level 380V test power supply 1.

[0120] (11) Short-circuit and discharge the compensation capacitor bank 14. Only after the discharge is completed can the test wiring of the system be disassembled.

[0121] (12) Test data analysis. The maximum temperature rise of the core teeth or yoke is not greater than 25K, that is, the difference between the final temperature and the initial temperature of the core at the same position before the end of the test is not greater than 25K. The maximum temperature difference of the core teeth or yoke is not greater than 15K, that is, the difference between the highest temperature and the lowest temperature at different positions of the core at the same moment is not greater than 15K. The core loss per unit mass is not greater than 1.3 times the standard loss of the core silicon steel sheet. The core loss per unit mass is obtained by dividing the core power loss value by the core weight.

[0122] (13) If the core temperature rise, temperature difference, and unit loss value all meet the above requirements, it is judged that the quality of the generator stator core is good. If any one of the core temperature rise, temperature difference, and unit loss value does not meet the requirements, it is judged that the quality of the generator stator core is abnormal, and it is necessary to further check whether there are defects such as looseness and insulation damage in the core, and carry out relevant treatments.

[0123] The key points of the magnetization test system for the generator stator core provided by this application are as follows:

[0124] (1) This test system preferably uses the voltage regulator to boost the excitation to zero. The excitation voltage can slowly rise from zero to the test voltage, so that the core reaches the magnetic flux density required by the test. Boosting the excitation of the voltage regulator to zero does not generate an excitation impact current similar to direct closing of a high voltage, and the excitation process of the stator core is safe and reliable.

[0125] (2) This test system preferably uses a compensating capacitor bank to compensate for the inductive reactive power in the magnetization test, greatly reducing the capacity of the test power supply. The capacitor bank consists of 10 parallel capacitors of the same type with a rated capacity of 100 kVar. According to different types of generators, the number of capacitors can be flexibly selected for compensation. The number of compensating capacitors n is calculated by the expression and is rounded to the nearest integer.

[0126] (3) This test system preferably uses a 25K temperature rise limit, a 15K temperature difference limit, and a 1.3 - fold standard loss value of silicon steel sheets as the discrimination basis for the stator core magnetization test, which can accurately reflect the quality of the core and is conducive to correctly formulating the maintenance strategy for the stator core.

[0127] The generator stator core magnetization test system provided by this application is applicable to the stator core magnetization tests of various large - capacity generators with a capacity of 6 MW to 1000 MW. For generators of different capacities, only the capacity of the test power supply, the number of turns of the excitation red circle, and the number of compensating capacitors are different. The instrument wiring, test methods, and test result analysis of the system are the same, having general universality. This test system has the following advantages:

[0128] (1) The test system preferably uses a 380V power supply as the test power, with strong flexibility and does not require too much cooperation from the power plant side.

[0129] (2) The test system preferably uses the zero - position boost excitation of the voltage regulator. The excitation voltage can slowly rise from zero to the test voltage, without generating an excitation inrush current similar to direct closing of high voltage, will not impact the load on the power supply side, and will not affect the operation of the load on the power supply side, greatly improving the safety of the core magnetization test.

[0130] (3) The test system preferably uses a compensating capacitor bank to compensate for the inductive reactive power in the core magnetization test, greatly reducing the output power and output current of the test power supply. As long as the compensation capacitance value is appropriate, the test power supply only needs to provide a power of several hundred kilowatts equivalent to the core loss. On the other hand, as the output current of the power supply decreases, the cross - sectional area and weight of the power supply cable can also be reduced.

[0131] (4) The test system preferably applies a magnetic flux density close to the rated value to the stator core through high voltage and large current, making the core close to the normal operating condition, and truly reflecting the temperature rise value of the stator core under the rated condition and the quality of the stator core.

[0132] (5)The test system preferably uses a dedicated infrared thermal imager to measure the temperature of the iron core. Data can also be obtained from a long distance, and the test process is safe and convenient. The test results directly reflect the temperature rise of the defect points on the iron core, and the detection effect is clear, intuitive, and highly repeatable. This test system can accurately locate the fault points on the iron core, and there will be no problem of misjudgment like the ELCID method that causes artificial damage to the generator stator iron core, which is conducive to correctly formulating the maintenance strategy for the stator iron core.

[0133] In the description of this specification, the description with reference to terms such as "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0134] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0135] The above-described embodiments only represent several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A generator stator core magnetization test system, characterized in that: The system comprises: Target power supply; the target power supply is a power supply having a switching function and a voltage regulating function; A target transformer; the target transformer is connected to the target power supply, and the target transformer is used to achieve output voltage conversion under the condition of compensating for inductive reactive power; An excitation module; the excitation module is connected to the target transformer, and the excitation module is used to generate an excitation magnetic field according to the voltage information output by the target transformer, so as to test the stator core of the generator to be tested which is arranged in the excitation magnetic field; Measuring module; the measuring module is respectively connected to the excitation module and the stator core of the generator to be tested, and the measuring module is used to measure the temperature information of the stator core of the generator and the power loss information corresponding to the stator core of the generator, and the temperature information and the power loss information are used to determine whether the stator core of the generator meets the quality requirements.

2. The system according to claim 1, characterized in that The measuring module comprises: Measuring coil; the measuring coil is arranged at a position orthogonal to the excitation coil in the excitation module.

3. The system according to claim 2, characterized in that The measurement module also includes: A voltage transformer; the voltage transformer is connected to the measuring coil, and the voltage transformer is used to measure the induced voltage of the measuring coil; Current transformer; the current transformer is sleeved on the excitation coil, and the current transformer is used to measure the excitation current of the excitation coil.

4. The system according to claim 3, characterized in that The measurement module also includes: Loss tester; the loss tester is connected to the voltage transformer and the current transformer respectively, and is used to determine the power loss information corresponding to the stator core of the generator according to the induced voltage and the excitation current.

5. The system according to claim 1, characterized in that The measuring module comprises: Infrared thermal imager; the infrared thermal imager is used to measure and obtain the temperature information of the generator stator core.

6. The system according to claim 5, characterized in that The measuring module comprises: Display module; the display module is used to display the temperature information.

7. The system according to claim 4, characterized in that The measuring module comprises: Display module; the display module is used to display the induced voltage, the excitation current and the power loss information.

8. The system according to claim 1, characterized in that The target transformer comprises: Compensation transformer; the compensation transformer is used to convert the voltage signal output by the target power supply into an excitation voltage signal that is sufficient to achieve the excitation coil to establish a magnetic field.

9. The system according to claim 8, characterized in that The target transformer also includes: At least two compensation capacitors connected in parallel; the compensation capacitors are used to compensate for the inductive reactive power generated when the compensation transformer transforms the voltage.

10. The system according to claim 1, characterized in that The target power supply comprises: A test power supply; the test power supply is used to output an alternating current signal for testing; A voltage regulator; the voltage regulator is connected to the target transformer, and the voltage regulator is used to adjust the magnitude of the output voltage signal; A power switch; the power switch is connected to the test power supply and the voltage regulator respectively, and the power switch is used to disconnect and connect the test power supply.

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