Wind driven generator blade lightning conductor broken line point positioning method based on radio frequency transformer

Abstract

The invention discloses a wind driven generator blade lightning conductor broken line point positioning method based on a radio frequency transformer, and relates to the field of wind driven generator blade lightning conductor broken line point positioning. A to-be-detected line is connected in series with the radio frequency transformer before being injected into traveling waves, and the change of traveling wave current is converted into the change of transformer output voltage; therefore, the output voltage of the radio frequency transformer is detected to judge the arrival time difference of the incident wave and the reflected wave, and then the breakpoint position is judged by multiplying the wave velocity by the time difference and dividing by 2. According to the wind driven generator blade lightning conductor breaking point positioning method based on the radio frequency transformer, the position of the lightning conductor breaking point can be efficiently, accurately, conveniently and flexibly detected at low cost, positioning measurement of disconnection of a multi-core wire part can be achieved, the specific positions of the breaking point and an abnormal point of the lightning conductor can be effectively determined, and the working efficiency is improved. After the positions of the broken line point and the abnormal point are determined, specific positions are repaired in a targeted manner, so that the cost for replacing the lightning conductor is saved.

Description

Technical Field

[0001] The present invention relates to the field of locating the broken point of the lightning protection wire of a wind turbine blade, and particularly to a method for locating the broken point of the lightning protection wire of a wind turbine blade based on a radio frequency transformer. Background Art

[0002] Wind turbines are mostly distributed in mountainous areas and coastal areas with frequent lightning strikes and are relatively tall themselves, so they are vulnerable to lightning strikes, which can cause serious damage to the power generation system, lead to long-term shutdowns, and result in huge economic losses. In addition, wind turbines are expensive, and the cost of maintenance, demolition, and replacement of damaged components is also huge. Therefore, the integrity of the lightning protection wire conductor is crucial for the safe operation of wind turbines. During the long-term operation of the blade, the lightning protection wire is subjected to a certain tension, and together with the multiple impacts of lightning current and aging problems, serious faults such as broken strands or fractures of the lightning protection wire may occur. Therefore, the detection of the broken wire of the lightning protection wire of a wind turbine blade is crucial in the design and operation process of the entire wind turbine.

[0003] Currently, the main traditional method used at home and abroad is to form a loop by connecting a wire outside the blade to the lightning protection wire, and the continuity is measured using Ohm's law. This method requires workers to be lowered by a hanging basket, so it is inefficient and costly. The lightning protection wire broken wire detection method based on the single-ended traveling wave ranging principle is a new research direction. Its main principle is to inject a pulse signal into one end of the lightning protection wire through a signal generating device, and at the same time, use a sensor to obtain the echo signal of the lightning protection wire, and calculate the length of the lightning protection wire through the echo signal to determine the broken wire position of the lightning protection wire. The key to realizing this method is the accurate detection of the arrival time of the echo signal. Due to the limited length of the lightning protection wire of the blade, the echo time is in the nanosecond range.

[0004] Currently, there are two problems in the research of this method: one is that the oscillation and trailing time of the incident wave of the pulse signal are long and the waveform is complex. When the broken wire point is relatively close to the detection point, the oscillation and trailing of the reflected wave and the incident wave are superimposed, making it difficult to analyze the arrival time of the incident wave. Therefore, the traditional single-ended traveling wave ranging method usually has a certain blind area. The other is that due to the use of electromagnetic induction method for traveling wave detection, the spatial magnetic field, wire non-uniformity and bending states will all add noise signals to the basis of the weak induction signal, and changing different detection objects and environments will affect the waveforms of the traveling wave voltage and current. Therefore, using methods such as peak value, wavelet analysis, and feature point learning and training to analyze the arrival time of the traveling wave voltage or current has certain robustness, resulting in large deviations in measurement.

[0005] Directly measuring the traveling wave voltage with an AD acquisition device, the input impedance and equivalent capacitance of the AD acquisition device will affect the waveform of the traveling wave voltage, resulting in measurement errors. Considering safety, usually the injected traveling wave energy is limited, generally a low-voltage signal, so the traveling wave current is very small. Measuring the traveling wave current through a high-frequency current transformer is prone to measurement errors caused by electromagnetic interference. The traveling wave passes through the equivalent inductance on the line, the wavefront time becomes longer, and there will be reflected signals when encountering impedance discontinuity points. Therefore, the waveforms of the actual incident and reflected traveling waves are very complex, which brings difficulties to accurately analyze the arrival time.

[0006] Therefore, it is necessary to propose a method for locating the broken point of the lightning protection wire of the wind turbine blade based on a radio frequency transformer to solve the above problems. Summary of the Invention

[0007] The main purpose of the present invention is to provide a method for locating the broken point of the lightning protection wire of the wind turbine blade based on a radio frequency transformer, which can effectively solve the problems in the background technology.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for locating the broken point of the lightning protection wire of the wind turbine blade based on a radio frequency transformer includes the following operation steps:

[0010] S1: Prepare the equipment for positioning, including an operation controller, a data collector, a radio frequency transformer, and a step signal generator;

[0011] S2: Input the primary lightning protection wire side in series through the radio frequency transformer before the measurement end of the lightning protection wire to be measured. When the traveling wave of the lightning protection wire passes through the transformer, a part of the electromagnetic wave energy will be transferred to the secondary side through magnetic field coupling. Judge the situation of the traveling wave passing through the transformer by monitoring the voltage and current on the secondary side;

[0012] S3: Give a low-voltage step voltage signal to the measurement end of the lightning protection wire to be measured as an excitation source. The forward traveling wave generated on the lightning protection wire to be measured is called the incident wave. During the transmission of the incident wave along the lightning protection wire to be measured, when encountering a break point, refraction and reflection phenomena of the traveling wave will occur. The reverse traveling wave reflected back is called the reflected wave;

[0013] S4: The incident wave current flowing through the primary and secondary sides of the radio frequency transformer will generate induced voltage and current; the reflected wave current flowing through the primary and secondary sides of the radio frequency transformer will generate induced voltage and current, and at the same time, the induced voltage and current will mutate; because the reflected wave and the incident wave are in opposite directions, the mutation directions of the induced voltage and current generated on the secondary side when the reflected wave and the incident wave pass through the primary side of the transformer are exactly opposite. Therefore, the current mutation point is the arrival time point of the reflected wave, and the trend of the current mutation can be judged by measuring the voltage on the secondary side. The formula is:

[0014]

[0015] Where U is the induced voltage; L is the equivalent inductance of the RF transformer; di and dt are the differentials of the RF transformer current with respect to time;

[0016] S5: Use a data collector to measure the voltage on the secondary side of the output of the RF transformer. By analyzing the voltage mutation, find the time difference △t between the accurate arrival times of the incident wave and the reflected wave;

[0017] S6: By previously measuring △ts for a known length of Ls cable of the same type as the lightning protection line to be measured, inversely calibrate the traveling wave velocity of the lightning protection line to be measured. The formula is:

[0018] V = Ls÷△ts;

[0019] S7: Based on the TDR principle, multiply △t×V / 2 of the lightning protection line to be measured to calculate the position of the break point of the lightning protection line to be measured from the test point.

[0020] Preferably, in S1, the operation controller is responsible for the process logic control, operation data processing, result display, and necessary human-machine interaction control in the positioning method;

[0021] The data collector is a high-speed data acquisition device, including at least 1 GHz sampling and 100 MHz bandwidth;

[0022] The RF transformer is a traveling wave current acquisition device, having a response speed at the ns level, at least 100 MHz bandwidth, and having impedance matching and signal isolation functions;

[0023] The step signal generator is used to generate a step signal with DC 10 - 30V adjustable and a rising edge less than 20 ns according to the signal given by the operation controller.

[0024] Preferably, in S2, after the measurement starts, first trigger the rising edge of the data collector, and then start with the given step signal. When the data collector acquires a valid signal of the voltage on the secondary side of the RF transformer, according to the longest length of the lightning protection line to be measured and the traveling wave velocity, select a complete set of data sampled for at least 2 us starting from the effective trigger. When the data is incomplete, restart the measurement once. For the complete data, perform basic low-pass filtering and window selection for further analysis and calculation.

[0025] Preferably, in S7, judge the inflection point of the traveling wave current through the rising and falling amplitudes of the output voltage of the RF transformer, the continuous transformation time, and the first derivative of the voltage. The difference between the two inflection point times is △t. Multiply △t×V / 2 to calculate the position of the break point of the lightning protection line to be measured from the test point. Compare the break point distance of the lightning protection line to be measured with the original length to judge whether there is a break and where the break point is located.

[0026] Compared with the prior art, the present invention provides a method for locating the break point of the lightning protection wire of the blade of a wind turbine based on a radio frequency transformer, which has the following beneficial effects:

[0027] 1. The method for locating the break point of the lightning protection wire of the blade of a wind turbine based on a radio frequency transformer can achieve efficient, accurate, low-cost, and convenient and flexible detection of the break point position of the lightning protection wire, and can also achieve the positioning measurement of partial disconnection of multi-core wires. Through this method, it is possible to enter the interior of the wind turbine and detect the continuity of the lightning protection wire at the hub of the wind turbine, and determine the specific positions of the break point and the abnormal point. After determining the positions of the break point and the abnormal point, targeted repairs can be carried out at the specific positions, saving the cost of replacing the lightning protection wire.

[0028] 2. The method for locating the break point of the lightning protection wire of the blade of a wind turbine based on a radio frequency transformer gives a low-voltage step voltage signal as the excitation source to the measurement end of the lightning protection wire to be measured; the primary side of the input of the radio frequency transformer is connected in series before the measurement end of the lightning protection wire to be measured; the incident wave current flows through the primary side of the radio frequency transformer, and an induced voltage and current are generated on the secondary side; when the reflected wave current flows through the primary side of the radio frequency transformer, the induced voltage and current generated on the secondary side will mutate.

[0029] 3. The method for locating the break point of the lightning protection wire of the blade of a wind turbine based on a radio frequency transformer can use a high-speed data collector to measure the voltage on the secondary side of the output of the radio frequency transformer. By analyzing the voltage mutation, the time difference △t between the accurate arrival times of the incident wave and the reflected wave can be found. According to the TDR principle, multiplying △t×V / 2 of the lightning protection wire to be measured can calculate the position of the break point of the lightning protection wire to be measured from the test point.

[0030] 4. For the method for locating the break point of the lightning protection wire of the blade of a wind turbine based on a radio frequency transformer, due to impedance increase caused by reasons such as local aging of the line and partial disconnection of multi-core wires, this method can also measure it, and the result can be calculated by multiplying the time difference △t×V / 2 between the voltage trough moment and the incident wave moment. Description of the Drawings

[0031] Figure 1 is the method topology diagram of the present invention;

[0032] Figure 2 is the operation flow chart of a single measurement of the present invention;

[0033] Figure 3 is the diagram of the secondary side voltage and the first derivative of the radio frequency transformer of the present invention. Detailed Embodiments

[0034] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0035] Example 1:

[0036] As Figures 1 - 3 shown, a method for locating the broken point of the lightning protection wire of a wind turbine blade based on a radio frequency transformer includes the following operation steps:

[0037] S1: Prepare the equipment for positioning, including an operation controller, a data collector, a radio frequency transformer, and a step signal generator;

[0038] The operation controller is responsible for the process logic control, operation data processing, result display, and necessary human-machine interaction control in the positioning method;

[0039] The data collector is a high-speed data collection device, including at least 1 GHz sampling and 100 MHz bandwidth;

[0040] The radio frequency transformer is a traveling wave current collection device, with a response speed at the ns level, at least 100 MHz bandwidth, and having impedance matching and signal isolation functions;

[0041] The step signal generator is used to generate a step signal with an adjustable DC of 10 - 30 V and a rising edge less than 20 ns according to the signal given by the operation controller;

[0042] S2: Before the primary lightning protection wire side is input in series to the measurement end of the lightning protection wire to be measured through the radio frequency transformer, when the traveling wave of the lightning protection wire passes through the transformer, a part of the electromagnetic wave energy will be transferred to the secondary side through magnetic field coupling. The situation of the traveling wave passing through the transformer is judged by monitoring the voltage and current on the secondary side;

[0043] After the measurement starts, first trigger the rising edge of the data collector, and then start with the given step signal. When the data collector collects the effective signal of the voltage on the secondary side of the radio frequency transformer, according to the longest length of the lightning protection wire to be measured and the traveling wave speed, select a complete data of at least 2 us of data sampled from the start of the trigger effective. For example, in the case of a wire with a maximum length of 200 m and a wave speed of 200 m / us, if the data is incomplete, restart the measurement once. For the complete data, perform basic low-pass filtering and window selection for further analysis and calculation;

[0044] S3: Given a low-voltage step voltage signal at the measurement end of the lightning protection wire to be measured as the excitation source, the forward traveling wave generated on the lightning protection wire to be measured is called the incident wave. When the incident wave travels along the lightning protection wire to be measured, refraction and reflection phenomena of the traveling wave will occur when it encounters a break point. The backward traveling wave reflected back is called the reflected wave;

[0045] S4: When the incident wave current flows through the primary and secondary sides of the RF transformer, induced voltages and currents will be generated; when the reflected wave current flows through the primary and secondary sides of the RF transformer, induced voltages and currents will also be generated, and at the same time, the induced voltages and currents will mutate; because the directions of the reflected wave and the incident wave are opposite, the directions of the mutations of the induced voltages and currents generated on the secondary side when the reflected wave and the incident wave pass through the primary side of the transformer are exactly opposite. Therefore, the current mutation point is the arrival time point of the reflected wave, and the trend of the current mutation can be judged by measuring the voltage on the secondary side. The formula is:

[0046]

[0047] Where U is the induced voltage; L is the equivalent inductance of the RF transformer; di and dt are the differentials of the RF transformer current with respect to time;

[0048] S5: Use a data collector to measure the voltage on the secondary side of the output of the RF transformer. By analyzing the voltage mutation, find the time difference △t between the accurate arrival times of the incident wave and the reflected wave;

[0049] S6: By measuring △ts in advance for a cable of the same type as the lightning protection wire to be measured with a known length of Ls, inversely calibrate the traveling wave velocity of the lightning protection wire of this type to be measured. The formula is:

[0050] V = Ls ÷ △ts;

[0051] S7: Based on the TDR principle, multiply △t × V / 2 of the lightning protection wire to be measured, and the position of the break point of the lightning protection wire to be measured from the test point can be calculated;

[0052] Judge the inflection point of the traveling wave current through the rising and falling amplitudes of the output voltage of the RF transformer, the continuous transformation time, and the first derivative of the voltage. Subtract the two inflection point times to get △t, and △t × V / 2 can calculate the position of the break point of the lightning protection wire to be measured from the test point. Compare the break point distance of the lightning protection wire to be measured with the original length, and it can be judged whether there is a break and where the break point is.

[0053] Embodiment 2:

[0054] A method for locating the break point of the lightning protection wire of a wind turbine blade based on an RF transformer, as Figure 2As shown, it is the flowchart of a single measurement run. After the measurement starts, the rising edge trigger of the data collector is first activated, and then a step signal is given. When the data collector acquires a valid signal of the voltage on the secondary side of the RF transformer, usually, according to the longest length of the lightning protection line to be measured and the traveling wave velocity, a complete set of data is selected. For example, in the case of a line with a maximum length of 200m and a wave velocity of 200m / μs, at least 2μs of data sampled from the start of the valid trigger is considered a complete set of data. If the data is incomplete, the measurement needs to be restarted. For the complete data, basic low-pass filtering and window selection are required for further analysis and calculation;

[0055] According to the traveling wave theory, in the case of a short circuit at the end of the line, there is a positive full reflection of voltage and a negative full reflection of current. Since the primary side of the RF transformer is in series with the lightning protection line to be measured, the incident wave current flows through the primary side of the RF transformer, and an induced voltage and current are generated on the secondary side; the reflected wave current flows through the primary side of the RF transformer, and the induced voltage and current on the secondary side will mutate; because the directions of the reflected wave and the incident wave are exactly opposite, when the reflected wave and the incident wave pass through the primary side of the transformer, the directions of the mutations of the induced voltage and current on the secondary side are exactly opposite. Therefore, the current mutation point is the arrival time point of the reflected wave. According to the formula:

[0056]

[0057] it can be known that the trend of the current mutation can just be judged by measuring the voltage on the secondary side;

[0058] Therefore, by judging the inflection points of the traveling wave current through the rising and falling amplitudes of the voltage output by the RF transformer, the continuous transformation time, and the first derivative of the voltage, the time difference between the two inflection points is △t, and the position of the break point of the lightning protection line to be measured from the test point can be calculated by △t×V / 2. By comparing the break point distance of the lightning protection line to be measured with the original length, it can be judged whether there is a break and where the break point is. In addition, due to reasons such as local aging of the line and partial disconnection of multi-core wires, which cause an increase in impedance, this method can also detect it. As Figure 3 shown, the voltage trough is the point where the impedance increases. By the time difference △t×V / 2 between the voltage trough moment and the incident wave moment, the abnormal point of the impedance increase can also be calculated.

[0059] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for locating the broken point of the lightning protection wire of a wind turbine blade based on a radio frequency transformer, characterized in that: It includes the following operation steps: S1: Prepare the positioning equipment, including an operation controller, a data collector, a radio frequency transformer, and a step signal generator; S2: Input it in series on the side of the primary lightning protection wire before the measurement end of the lightning protection wire to be measured through the radio frequency transformer. When the traveling wave of the lightning protection wire passes through the transformer, part of the electromagnetic wave energy will be transferred to the secondary side through magnetic field coupling. Determine the situation of the traveling wave passing through the transformer by monitoring the voltage and current on the secondary side; S3: Apply a low-voltage step voltage signal to the measurement end of the lightning protection wire to be measured as the excitation source. The forward traveling wave generated on the lightning protection wire to be measured is called the incident wave. During the transmission of the incident wave along the lightning protection wire to be measured, when it encounters a break point, refraction and reflection phenomena of the traveling wave will occur. Among them, the reflected backward traveling wave is called the reflected wave; S4: The incident wave current flowing through the primary and secondary sides of the radio frequency transformer will generate induced voltage and current; the reflected wave current flowing through the primary and secondary sides of the radio frequency transformer will generate induced voltage and current, and at the same time, the induced voltage and current will mutate; because the reflected wave and the incident wave are in opposite directions, when the reflected wave and the incident wave pass through the primary side of the transformer, the mutation directions of the induced voltage and current generated on the secondary side are exactly opposite. Therefore, the current mutation point is the arrival time point of the reflected wave, and the trend of the current mutation can be judged by measuring the voltage on the secondary side. The formula is: Where U is the induced voltage; L is the equivalent inductance of the radio frequency transformer; di and dt are the differentials of the radio frequency transformer current with respect to time; S5: Use the data collector to measure the voltage on the secondary side output by the radio frequency transformer. By analyzing the voltage mutation, find the time difference △t between the accurate arrival times of the incident wave and the reflected wave; S6: By measuring △ts in advance for a section of the same type of cable as the lightning protection wire to be measured with a known length of Ls, reverse calibrate the traveling wave speed of the lightning protection wire of this type. The formula is: V = Ls÷△ts; S7: Based on the TDR principle, multiply △t×V / 2 of the lightning protection wire to be measured, and the position of the break point of the lightning protection wire to be measured from the test point can be calculated.

2. The method for locating the broken point of the lightning protection wire of the wind turbine blade based on the RF transformer according to claim 1, wherein: In S1, the operation controller is responsible for the process logic control, operation data processing, result display, and necessary human-computer interaction control in the positioning method; The data collector is a high-speed data acquisition device, including at least 1 GHz sampling and 100 MHz bandwidth; The radio frequency transformer is a traveling wave current acquisition device, with a response speed of ns level, at least 100 MHz bandwidth, and has impedance matching and signal isolation functions; The step signal generator is used to generate a step signal with an adjustable DC of 10 - 30V and a rising edge less than 20 ns according to the signal given by the operation controller.

3. The method for locating the broken point of the lightning protection wire of the wind turbine blade based on the radio frequency transformer according to claim 1, characterized in that: In S2, after the measurement starts, first trigger the rising edge of the data collector, and then start to give the step signal. When the data collector acquires the effective signal of the voltage on the secondary side of the radio frequency transformer, according to the longest length of the lightning protection wire to be measured and the traveling wave speed, select a complete set of data with at least 2 us of sampling starting from the trigger effectiveness. If the data is incomplete, restart the measurement once. For the complete data, perform basic low-pass filtering and window selection for further analysis and calculation.

4. The method for locating the broken point of the lightning protection wire of the wind turbine blade based on the RF transformer according to claim 1, characterized in that: In the S7, the inflection points of the traveling wave current are judged by the rising and falling amplitudes of the output voltage of the radio frequency transformer, the continuous transformation time, and the first derivative of the voltage. The difference between the two inflection point times is △t. The position of the break point of the lightning protection line to be measured from the test point can be calculated by △t×V / 2. By comparing the distance of the break point of the lightning protection line to be measured with the original length, it can be judged whether there is a break and where the break point is located.

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