WO2023179153A1

WO2023179153A1 - Generator iron core loss test system and method for reducing test impulse current

Info

Publication number: WO2023179153A1
Application number: PCT/CN2022/143193
Authority: WO
Inventors: 史振利; 何信林; 郭琳; 杨世强; 雷阳; 王创博; 刘旭辉; 李春丽; 张鹏; 季东旭; 张文斌; 倪继文
Original assignee: 西安热工研究院有限公司
Priority date: 2022-03-25
Filing date: 2022-12-29
Publication date: 2023-09-28
Also published as: CN114690095A

Abstract

A generator iron core loss test system for reducing test impulse current, comprising a power supply unit (4), a switch control unit (3), a current measurement unit (7), a voltage measurement unit (6), a multifunctional power measurement unit (8), a magnet exciting coil unit (2), a measurement coil unit (5), and an iron core unit under test (1). The magnet exciting coil unit (2) and the measurement coil unit (5) are wound on the iron core unit under test (1); the power supply unit (4) is connected to the magnet exciting coil unit (2) by means of the switch control unit (3); the magnet exciting coil unit (2) is connected to the multifunctional power measurement unit (8) by means of the current measurement unit (7); and the measurement coil unit (5) is connected to the multifunctional power measurement unit (8) by means of the voltage measurement unit (6).

Description

Generator core loss test system and method for reducing test impulse current

Cross-references to related applications

This application requires the priority of the Chinese patent application submitted to the China Patent Office on March 25, 2022, with the application number 202210302854X and the invention title "A generator core loss test system and method for reducing test impulse current", all of which The contents are incorporated into this application by reference.

Technical field

This application belongs to the technical field of motor stator core loss detection, and relates to a generator core loss test system and method for reducing test impulse current.

Background technique

As the source of power in the power system and its core position in various power plants, generators play a vital role in the entire power system and national life. Over the years, accidents caused by generator failure have occurred frequently, which is caused by not paying enough attention to the early signs of generator failure. At this stage, various power plants have also introduced various preventive tests to conduct regular inspections of generators, hoping to eliminate problems at the source in the early stages of generator failure, thereby improving the safety and stability of the power system. The generator stator core is made up of stacked silicon steel sheets. During normal operation, the core will be subject to the combined effects of mechanical force, thermal stress and electromagnetic force. Therefore, over time, different failures will occur in the core, such as When there are insulation defects between silicon steel sheet laminations, eddy currents will be generated in the core in a strong magnetic flux environment, which will lead to local temperature increases. In the long term, it will cause irreversible damage such as winding insulation damage or even core burning. Therefore, the iron loss test must be carried out after the core stacking is completed or the slot wedge is removed.

At this stage, conventional iron loss tests all use an unshielded cable with a length of about 300 meters and a cross-sectional area of ^120mm2 , which is evenly arranged around the entire core circumference. The generator stator core serves as a flux loop and excitation The winding and measuring coil serve as primary and secondary sides respectively. After the power circuit breaker is directly closed and AC power is supplied, an alternating magnetic flux close to saturation is generated inside the core, resulting in eddy current and hysteresis loss in the core, causing the core to heat up. The generator core is detected based on the temperature rise of the core. failure, so that the iron loss test plays a preventive role. Under this kind of test operation, the arrangement of a whole cable greatly increases the consumption of manpower and material resources, and lengthens the test preparation time; secondly, during the actual test process, the closing operation is generally performed from 6kV voltage, and the power generation The operating condition of the stator core of the machine is full voltage and no-load operation. Directly closing the circuit breaker will easily generate an inrush current of 5-7 times the rated current at the moment of closing, which not only easily causes the relay protection device on the power line side to malfunction, but also causes The sudden rise and fall of the upper-level line voltage will affect the normal operation of other electrical equipment, and in serious cases will damage the test equipment.

Contents of the invention

The purpose of this application is to provide a generator core loss test system and method that reduces test impulse current. This system and method can overcome the shortcomings of the above-mentioned existing technologies and effectively save test costs, reduce workload, and shorten test preparation time. Reduce the inrush current when the switch is closed and greatly improve the economy and safety of the iron loss test.

In order to achieve the above purpose, the generator core loss test system for reducing test impulse current described in this application includes a power supply unit, a switch control unit, a current measurement unit, a voltage measurement unit, a multifunctional power measurement unit, an excitation coil unit, and a measurement coil unit. And the core unit to be tested;

The excitation coil unit and the measurement coil unit are wound around the core unit to be measured. The power supply unit is connected to the excitation coil unit through the switch control unit. The excitation coil unit is connected to the multifunctional power measurement unit through the current measurement unit. The measurement coil unit is measured by voltage. The unit is connected to the multifunctional power measuring unit.

It also includes an infrared monitoring unit for real-time monitoring of the temperature of the core unit to be measured and the ambient temperature.

The switch control unit includes a computer, a logic loop controller, a high-voltage circuit breaker and a phase reference module. The power supply unit is connected to the excitation coil unit via the phase reference module and the high-voltage circuit breaker. The computer is connected to the high-voltage circuit breaker via the logic loop controller. Connected to the phase reference module.

The phase reference module includes a synchronous transformer unit, a low-pass filter unit, a high-pass filter unit, a square wave conversion unit and a hysteresis comparison unit that are connected in sequence.

The excitation coils in the excitation coil unit are evenly arranged on the core unit to be tested.

The measuring coil unit is arranged in the center of the generator hall.

The excitation coil unit is connected to the multifunctional power measuring unit through a current measuring clamp.

The generator core loss test method for reducing test impulse current described in this application includes the following steps:

1) Remove the connecting wire between the generator outlet and the closed busbar, remove the connecting wire of the stator three-phase winding at the neutral point, and measure the various CT secondary sides of the generator, the generator outlet, the closed busbar side, and each temperature measurement Components are shorted to ground;

2) The computer issues a test start command, and the phase reference module processes the voltage signal on the power supply side. The synchronous transformation unit transforms the power supply voltage and keeps the output signal in the same phase and frequency as the power supply voltage. Among them, through the low-pass filtering unit And the high-pass filter unit filters out the high-order harmonics and low-order harmonics in the signal, converts the voltage signal into a square wave signal through the square wave conversion unit, and finally removes the burrs in the square wave signal through the hysteresis comparison unit, and then inputs it to In the logic loop controller, the square wave signal is logically processed through the logic loop controller and a closing instruction of the high-voltage circuit breaker is issued. After receiving the test start instruction, the logic loop controller counts the time every 40 μs and reads the data. Read the voltage signal and determine whether its phase is 0+kπ (k=0,1,2,...,n). If not, continue to read the data. If so, delay T=nt ₁ -t ₂ (T≥0,n=1,3,5,...,n) and then output the closing command of the high-voltage circuit breaker. The high-voltage circuit breaker performs the closing action after receiving the closing command of the high-voltage circuit breaker.

This application has the following beneficial effects:

During specific operation, the generator core loss test system and method for reducing test impulse current described in this application performs logical processing on the square wave signal through the logic loop controller and issues a closing instruction of the high-voltage circuit breaker, wherein the logic loop controller receives After receiving the test start command, time it every 40μs and read the data. Read the voltage signal and determine whether its phase is 0+kπ (k=0,1,2,...,n). If not, then Continue to read the data, if so, then delay T＝nt ₁ -t ₂ (T≥0,n＝1,3,5,...,n) and then output the closing command of the high-voltage circuit breaker to achieve switch control The optimization of the unit not only saves test costs and shortens test preparation time, but also effectively reduces the inrush current when the switch is closed, greatly improving the economy and safety of the iron loss test.

Description of the drawings

Figure 1 is a schematic structural diagram of an embodiment of the present application.

Figure 2 is a schematic diagram of a system in an embodiment of the present application.

Figure 3 is a schematic block diagram of a system in an embodiment of the present application.

Figure 4 is a schematic diagram of a system in an embodiment of the present application.

Figure 5 is a schematic diagram of the uniform arrangement of the excitation coils in the excitation coil unit in an embodiment of the present application.

FIG. 6 is a flow chart of logic processing and closing command output of the high-voltage circuit breaker 31 in one embodiment of the present application.

Among them, 1 is the core unit to be measured, 2 is the excitation coil unit, 3 is the switch control unit, 4 is the power supply unit, 5 is the measurement coil unit, 6 is the voltage measurement unit, 7 is the current measurement unit, and 8 is the multi-functional power measurement unit. unit, 9 is an infrared monitoring unit, 10 is a current measuring clamp, 31 is a high-voltage circuit breaker, 32 is a phase reference module, 33 is a logic loop controller, 34 is a computer, 321 is a synchronous transformer unit, and 322 is a low-pass filter unit. , 323 is a high-pass filter unit, 324 is a square wave conversion unit, and 325 is a hysteresis comparison unit.

Detailed ways

In order to enable those in the technical field to better understand the solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only The embodiments are part of the present application, not all the embodiments, and are not intended to limit the scope of disclosure of the present application. Furthermore, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts disclosed in this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of this application.

A schematic structural diagram of an embodiment disclosed in the present application is shown in the accompanying drawings. The drawings are not drawn to scale, with certain details exaggerated and may have been omitted for purposes of clarity. The shapes of the various regions and layers shown in the figures and the relative sizes and positional relationships between them are only exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art will base their judgment on actual situations. Additional regions/layers with different shapes, sizes, and relative positions can be designed as needed.

Referring to Figure 1, the generator core loss test system for reducing test impulse current described in this application includes a power supply unit 4, a switch control unit 3, a current measurement unit 7, a voltage measurement unit 6, a multifunctional power measurement unit 8, and an excitation coil unit. 2. Measuring coil unit 5, infrared monitoring unit 9 and core unit 1 to be measured.

The power supply unit 4 is connected to each electrical equipment through the switch control unit 3 to provide AC power for the entire iron loss test. The excitation coil unit 2 and the measurement coil unit 5 are wound around the core unit 1 to be tested.

Referring to Figure 2, the switch control unit 3 includes a computer 34, a logic loop controller 33, a high-voltage circuit breaker 31 and a phase reference module 32. The power supply unit 4 communicates with the excitation coil unit 2 through the phase reference module 32 and the high-voltage circuit breaker 31. are connected, wherein the computer 34 is connected to the high-voltage circuit breaker 31 and the phase reference module 32 via the logic loop controller 33. The phase reference module 32 includes a synchronous transformer unit 321, a low-pass filter unit 322, a high-pass filter unit 322, and a high-pass filter unit 321 connected in sequence. The filtering unit 323, the square wave conversion unit 324 and the hysteresis comparison unit 325 perform filtering, square wave conversion and hysteresis comparison on the line voltage signal to obtain a processed voltage signal, and then input the processed voltage signal to the logic loop control The logic loop controller 33 is connected to the computer 34 for receiving switch closing information from the user and feeding back visual information to the user. On the other hand, it is connected to the high-voltage circuit breaker 31 to logically process the return signal and output the circuit breaker. The closing command controls the high-voltage circuit breaker 31 to close at the maximum or minimum voltage amplitude to reduce the inrush current.

Assume that the AC voltage when closing is:

Among them, α is the initial phase of voltage u(t) during no-load closing, and the magnetic flux φ is:

φ＝-φmcos(ωt+α)+φmcosα

It can be seen from the above formula that the size of the magnetic flux during no-load closing is related to the initial phase angle α of the power supply voltage, and has two components. The first one is the steady-state component, where the steady-state component decreases as time goes by; The second one is the transient component. Due to the existence of internal resistance, the transient component gradually decays to 0 as time goes by. Due to the existence of the transient component, a huge inrush current is easily generated at the moment of closing.

When closing at α=π/2+kπ (k=0,1,2,...,n), then there is:

φ＝φm sinωt

At this time, it enters the steady state process directly after closing, and there is no transient process, that is, the excitation current is the no-load current under normal operating conditions.

When α=0+kπ (k=0,1,2,...,n), the switch is closed, then:

φ＝-φm cosωt+φm

At this time, the magnetic flux has two components, namely -φm cosωt and φm. Since the relationship between magnetic flux and current is not linear, in the most extreme case, when the magnetic flux is 2φm, the core is deeply saturated and the excitation current increases sharply. , when closing under the condition of α=0+kπ (k=0,1,2,...,n), the inrush current will reach dozens or even hundreds of times of the no-load current during stable operation, which is the rated current 5-7 times. Therefore, based on the above analysis, the closer the initial phase of the voltage is to α=π/2+kπ (k=0,1,2,...,n), the closer the impulse current is to the no-load current.

The signal received by the logic loop controller 33 is a square wave signal converted from a voltage sine wave, so it is easy to determine the zero-crossing point signal when the voltage signal is converted from positive to negative, that is, the voltage phase α=0+kπ (k=0, 1,2,...,n), since the phase difference between voltage and current is 90°, the maximum or minimum value of the voltage is 1/4 cycle after the zero-crossing moment of the voltage, which is also the zero-crossing moment of the current. Assume

Among them, t ₁ is the 1/4 cycle duration at the actual voltage frequency.

The high-voltage circuit breaker 31 has a leading time for the closing pulse after the closing command is issued to when the main contacts are actually closed. The main reason is that the closing command needs to pass through the intermediate relay to drive the closing coil of the high-voltage circuit breaker 31, and the high-voltage circuit breaker The dynamic and static contacts of device 31 begin to move, and finally the main contacts are completely closed. The lead time includes the sum of the action times of all the intermediate components. Since the closing time of the high-voltage circuit breaker 31 is determined by itself, the lead time does not change with changes in frequency and voltage, that is, the constant lead time t ₂ .

Based on the above reasons, after collecting the voltage zero-crossing signal, the logic loop controller 33 is used to delay the closing of the high-voltage circuit breaker 31. The extension time is T=nt ₁ -t ₂ (T≥0, n=1 ,3,5,...,n), through the switch control unit 3, the high-voltage circuit breaker 31 can be closed at the maximum or minimum point of the voltage value, effectively reducing the inrush current at the closing moment; on the other hand, considering the lead time, through the switch The control unit 3 can control the actual closing time of the main contact in the high-voltage circuit breaker 31 to ensure the success rate of the test method.

The current measuring unit 7 is connected to the line through the current measuring clamp 10 . The current measuring unit 7 is connected to the multifunctional power measuring unit 8 for measuring the current and power of the excitation coil unit 2 .

The primary side of the voltage transformer in the voltage measurement unit 6 is connected to the measurement coil unit 5, and is connected to the multifunctional power measurement unit 8 through the secondary side of the voltage transformer in the voltage measurement unit 6 for recording the terminal voltage of the measurement coil.

The excitation coil unit 2 and the measurement coil unit 5 are both connected to the core unit 1 to be measured. Among them, the excitation coil unit 2 has 20 cables with a length of 15 meters and a cross-sectional area of 120 mm ² , respectively inside and outside the core unit 1 to be measured. Arrange 10 cables evenly, then connect the segmented cables in sequence according to the specified sequence numbers and arrange them evenly on the core unit 1 to be tested.

The infrared monitoring unit 9 uses an infrared thermal imager to monitor the temperature of the core unit 1 to be measured and the ambient temperature in real time.

The generator core loss test method based on reducing test impulse current described in this application includes the following steps:

The power supply unit 4 leads from the power plant and is connected to the excitation coil unit 2 through the high-voltage circuit breaker 31 in the switch control unit 3 to provide AC power for the entire iron loss test;

The excitation coils in the excitation coil unit are evenly arranged on the stator core of the generator. As shown in Figure 5, lay the insulating rods evenly in the generator hall. The distance between each insulating rod is 1 meter and the length of the insulating rod is 1.5 meters. Arrange the No. 1 cable on the far right side of the generator hall, No. 2 to Cable No. 10 is evenly arranged on the left side of cable No. 1; and cable No. 11 is arranged on the rightmost side outside the generator hall; cables No. 12 to 20 are evenly arranged on the left side of cable No. 11; finally, the cables are arranged in order Connection, that is, reliably connect No. 1 cable terminal 2 to No. 11 cable terminal 3, reliably connect No. 11 cable terminal 4 to No. 2 cable terminal 5, and so on according to the method in Figure 5 to form an excitation coil.

The measuring coil unit is arranged in the center of the generator hall and connected to the primary side of the voltage transformer in the voltage measuring unit 6. The secondary side of the voltage transformer is connected to the multifunctional power measuring unit 8. On the other hand, The current measuring clamp 10 is connected to the circuit of the excitation coil unit 2 and is connected to the multifunctional power measuring unit 8 for measuring the current and power of the excitation coil unit 2 .

An infrared thermal imager is used to record the initial temperature of the generator stator core, and monitor the changes in the generator stator core temperature and ambient temperature in real time.

The computer 34 issues a test start command, the phase reference module 32 processes the power supply side voltage signal, and the synchronous transformation unit 321 transforms the power supply voltage and keeps the output signal in the same phase and frequency as the power supply voltage, where the low-pass filtering unit 322 and the high-pass filter unit 323 filter out the high-order harmonics and low-order harmonics in the signal, convert it into a square wave signal through the square wave conversion unit 324, and finally remove the burrs in the square wave signal through the hysteresis comparison unit 325, and then input To the logic loop controller 33, the square wave signal is logically processed through the logic loop controller 33 and a closing instruction of the high-voltage circuit breaker 31 is issued. The logic processing and closing instruction output flow of the high-voltage circuit breaker 31 are shown in Figure 6, where , after the logic loop controller 33 receives the user's start information, it counts once every 40 μs and reads the data. It reads the voltage signal and determines whether its phase is 0+kπ (k=0,1,2,... ,n), if not, continue to read the data, if so, perform a delay operation, after a delay of T＝nt ₁ -t ₂ (T≥0,n＝1,3,5,...,n) The closing command of the high-voltage circuit breaker 31 is output. After receiving the closing command of the high-voltage circuit breaker 31, the high-voltage circuit breaker 31 performs a closing action, so that the entire circuit is powered on.

During the test, test data shall be recorded at least every 15 minutes, including frequency, excitation coil current, power, measurement coil terminal voltage, stator core temperature and ambient temperature.

It should be noted that the above is only used to illustrate the technical solution of this patent and not to limit it. Although the patent is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solution of this patent can be modified or equivalent. Replacements without departing from the purpose and scope of this technical solution shall be covered by the claims of this patent.

Claims

A generator core loss test system for reducing test impulse current, which is characterized by including a power supply unit (4), a switch control unit (3), a current measurement unit (7), a voltage measurement unit (6), and a multifunctional power measurement unit. Unit (8), excitation coil unit (2), measuring coil unit (5) and core unit to be measured (1);

The excitation coil unit (2) and the measurement coil unit (5) are wound around the core unit (1) to be measured. The power supply unit (4) is connected to the excitation coil unit (2) through the switch control unit (3). The excitation coil unit (2) 2) The current measuring unit (7) is connected to the multifunctional power measuring unit (8), and the measuring coil unit (5) is connected to the voltage measuring unit (6) to the multifunctional power measuring unit (8).
The generator core loss test system for reducing test impulse current according to claim 1, further comprising an infrared monitoring unit (9) for real-time monitoring of the temperature of the core unit (1) to be tested and the ambient temperature.
The generator core loss test system for reducing test impulse current according to claim 1, characterized in that the switch control unit (3) includes a computer (34), a logic loop controller (33), a high-voltage circuit breaker (31) and Phase reference module (32), in which the power supply unit (4) is connected to the excitation coil unit (2) via the phase reference module (32) and the high-voltage circuit breaker (31), in which the computer (34) is connected via the logic loop controller ( 33) is connected to the high-voltage circuit breaker (31) and the phase reference module (32).
The generator core loss test system for reducing test impulse current according to claim 3, characterized in that the phase reference module (32) includes a synchronous transformer unit (321), a low-pass filter unit (322) connected in sequence, High-pass filter unit (323), square wave conversion unit (324) and hysteresis comparison unit (325).
The generator core loss test system for reducing test impulse current according to claim 1, characterized in that the excitation coils in the excitation coil unit (2) are evenly arranged on the core unit (1) to be tested.
The generator core loss test system for reducing test impulse current according to claim 1, characterized in that the measurement coil unit (2) is arranged at a central position in the hall of the generator.
The generator core loss test system for reducing test impulse current according to claim 1, characterized in that the excitation coil unit (2) is connected to the multifunctional power measuring unit (8) through a current measuring clamp (10).
A generator core loss test method for reducing test impulse current, characterized in that, based on the generator core loss test system for reducing test impulse current according to claim 4, it includes the following steps:

1) Remove the connecting wire between the generator outlet and the closed busbar, remove the connecting wire of the stator three-phase winding at the neutral point, and measure the various CT secondary sides of the generator, the generator outlet, the closed busbar side, and each temperature measurement Components are shorted to ground;

2) The computer (34) issues a test start command, the phase reference module (32) processes the voltage signal on the power supply side, and the synchronous transformation unit (321) transforms the power supply voltage and keeps the output signal in the same phase and same state as the power supply voltage. frequency, in which the high-order harmonics and low-order harmonics in the signal are filtered out by the low-pass filtering unit (322) and the high-pass filtering unit (323), and the voltage signal is converted into a square wave signal by the square wave conversion unit (324). , and finally remove the burrs in the square wave signal through the hysteresis comparison unit (325), and then input it into the logic loop controller (33). The square wave signal is logically processed through the logic loop controller (33) and a high-voltage circuit breaker ( 31) closing command, in which, after receiving the test start command, the logic loop controller (33) times every 40 μs and reads the data, reads the voltage signal and determines whether its phase is 0+kπ (k=0 ,1,2,...,n), if not, continue to read the data, if so, delay T＝nt 1 -t 2 (T≥0,n＝1,3,5,..., n) and then outputs the closing command of the high-voltage circuit breaker (31), and the high-voltage circuit breaker (31) performs the closing action after receiving the closing command of the high-voltage circuit breaker (31).