KR20050023034A - Diagnostic device for the detection of loosening bolts in the tower for transmission and distribution and thereof method - Google Patents

Abstract

PURPOSE: A diagnostic device and a diagnostic method for detecting loosened bolt in tower for transmission and distribution are provided to detect a signal of a loosened bolt in a normal state based on strength change characteristics. CONSTITUTION: A diagnostic device for detecting a loosened bolt in a tower for transmission and distribution includes a signal measurement unit(100), a filter(200), a converter(300), an operation unit(400), a diagnostic unit(500), and a display unit(600). The signal measurement unit(100) measures an input signal of a force sensor and an output signal of an acceleration/a sound sensor. The filter(200) amplifies an input/output signal from the signal measurement unit(100) and passes the input/output signal through a low pass filter. The converter(300) converts the filter input/output signal in a time domain into a signal in a frequency domain. The operation unit(400) calculates peculiar frequencies of the converted input/output signal filtered by the filter.

Description

Diagnostic device for the detection of loosening bolts in the tower for transmission and distribution and explanation method}

The present invention relates to an apparatus and method for diagnosing bolt loosening of transmission and distribution tower structure. More specifically, the present invention relates to a technology for checking the bolt loosening without checking the bolt fastening portion of the transmission and distribution tower structure.

Currently, there are about 1,300 distribution towers operated by KEPCO, but most of the distribution towers are installed at higher positions than the surrounding environment.

In particular, the Haewol Steel Tower was installed to supply power to island areas in Incheon, Jeonnam, and Gyeongnam, but these locations are the landing points of typhoons and winds with various wind pressures (frequency) at all times.

Thus, when the wind coincides with the natural frequency of the distribution tower structure, the vibration of the tower structure is amplified and transmitted, causing more frequent bolt loosening than other towers in the region. The opinions are divided because there is no representativeness of the inspection criteria.

At present, the countermeasure against this problem is costly by adopting a method of selecting bolts at random and occupying some bolts, and then tightening bolts of all pylons collectively when loosening is observed.

For example, in the Jeonnam branch office, it cost about 400 million won by tightening bolts of 152 distribution towers in 2000.

In the case of the distribution tower located near the coast, the bolts are tightened by strengthening the standard than the transmission tower due to frequent exposure to strong wind loads and bolt loosening, but it is pointed out in the audit because of the high frequency.

The method of checking the bolt's loosening degree can be determined by tapping the steel tower with a stick and checking the degree of trembling, and checking the loosening level manually using a tool. However, the former is an empirical method that requires a high level of skill and appropriateness. Judgment is also difficult, and the latter requires a manpower and expense because the bolts to the tower directly on the tower.

In the latter case, in order to reduce expenses, some of the tracks are extracted and inspected according to the operation standard of the power transmission facilities, but in the case of distribution towers, it is difficult to check the extraction as it consists of four steel towers on one track. Therefore, the development of a technique and diagnostic equipment that can determine whether the bolt is loosened was required.

As a known technique for solving this problem, "Application No. 20-2002-38120, Designation name: Rigidity measuring apparatus of assembly structure" is proposed.

According to the known technology as described above, by measuring the resonant frequency by converting the acceleration signal generated in the assembly structure to which the external force is applied to the frequency and then compares the previous measurement results with the current measurement results of the structure according to the change in the fastening force of the various fasteners The stiffness change can be measured.

However, the above known technique is that when the acceleration sensor is attached to an appropriate point of the steel tower assembly structure and external force is applied to a certain portion of the steel tower assembly structure in order to measure the change in rigidity of the assembly structure according to the change in the fastening force of various fastenings A lot of difficulties were involved in measuring consistent stiffness variations throughout the assembly. This lowers the reliability of the measurement result.

That is, the problem with the above known technique is clearly revealed by the experimental data of FIGS. 7A to 7F presented in the present invention.

Accordingly, the present invention is to solve the above problems, the present invention can detect the difference in the signal of the bolt loosening state of the steady state from the characteristic that the stiffness changes with respect to the specific constituents of the transmission and distribution steel tower structure when the bolt loosening occurs Therefore, the purpose of this is to diagnose the loosening using this.

As a technical idea for achieving the above object of the present invention

In the diagnostic method of bolt loosening of transmission and distribution steel tower structure,

Exciting the structure using an impact hammer;

Measuring the vibration and sound wave signals generated by the excitation using an acceleration and sound sensor installed at a specific structure of the steel tower structure;

Extracting a noise from a sound wave signal while extracting a resonant frequency from the measured vibration signal by using a fast Fourier transform (FFT) method;

Analyzing the bolt loosening of the structure and the sensitivity of the measurement signal;

Comparing and reviewing the analyzed sensitivity result data with data of a normal signal constructed in an existing database;

On the basis of the above results it provides a method for diagnosing the bolt loosening of the transmission and distribution tower structure comprising the step of diagnosing the bolt loosening of the transmission and distribution tower structure.

Hereinafter, with reference to the accompanying drawings, the configuration and operation of the embodiment of the present invention will be described in detail.

1 is an overall conceptual view of the bolt loosening diagnostic apparatus for the transmission and distribution steel tower structure according to the present invention.

Referring to Figure 1, the signal measuring means for measuring the output signal with the acceleration / sound sensor as well as measuring the input signal to the force (sensor) by the impact hammer (Impact hammer) from a specific end of the transmission and distribution steel tower structure ( 100); Filtering means (200) for amplifying the input / output signal from the signal measuring means (100) and performing low pass filtering; Conversion means (300) for converting the input / output signal filtered from the filtering means (200) from a time domain to a frequency domain by a fast Fourier transform (FFT) method; Calculation means (400) for calculating a natural frequency, shear rate, and a closeness function of the input / output signal converted from the conversion means (300); Diagnostic means (500) for diagnosing the bolt loosening of the entire structure from a specific member of the transmission and distribution steel tower structure by comparing operation data from the calculation means (400) with normal signal data from an existing database; And display means 600 for displaying the result data from the diagnostic means 500.

At this time, the specific portion of the transmission and distribution tower structure represents an area designated as at least one section (section) in the tower structure.

Figure 2 is a detailed configuration of the bolt loosening diagnostic apparatus for the transmission and distribution tower structure according to the present invention.

2, a digital signal processor (DSP) 10 serving as a central processing unit (CPU) and used as a 50 MHz oscillation module; A memory unit 20 having a ROM in which PCB diagnosis and application programs are stored, an SRAM for high-speed data input / output, and a flash memory having a data storage space of 1 Gbit; An A / D converter unit 30 having an input channel of analog data; A filter unit 40 used as a module for removing sensor input noise; A universal serial bus (USB) unit 50 for 12 Mb / sec high-speed data input / output; A serial communication unit 60 using 8251 and RS232; A power supply unit 70 including a battery and a DC-DC converter for system power supply is provided. In addition, a personal digital assistant (PDA) 80 for controlling the bolt loosening diagnosis device is provided.

That is, the apparatus for unfastening the bolt according to the present invention mainly uses a 32-bit floating point DSP 10 capable of performing a fast operation, and a ROM (ROM) in which a program for operating the equipment is stored, and quickly inputs data to the DSP ( 10) and the memory unit 20 having a 32-bit SRAM (SRAM) to perform the operation, stable to the A / D converter unit 30, the A / D converter unit 30, which is essential to data the frequency value In order to input data, the current filter unit 40 is designed to store all the necessary amount of data while driving the installation equipment. .

In addition, a DC-DC converter is used to install a battery for the portable and stable power supply 70, and a 5V supply for a circuit operation and a 24V output for supplying a sensor are made. In addition, the PDA 80, which is currently commercialized, was used for the operation of the equipment. The PDA 80 and the diagnostic apparatus used the RS232 serial communication unit 60 to transfer the collected data to the computer (PC) per second. It has a built-in USB unit 50 that can input and output at 12Mbit.

3 is an overall flowchart showing a bolt loosening diagnosis method of the transmission and distribution tower structure according to the present invention. 4 is a detailed flowchart of the bolt loosening diagnosis method of FIG. 3.

Referring to FIGS. 3 and 4, first, an impact hammer is used to have a transmission and distribution tower structure (S100). In this state, the vibration and sound wave signals generated by the excitation are measured (S111-S112).

At this time, as the impact hammer has a steel tower structure, an input signal (Input signal x (t)) (100a of FIG. 4) may be obtained by a force sensor, and an output signal by an acceleration / sound sensor. y (t)) (100b of FIG. 4) can be obtained.

Thereafter, the resonance frequency is extracted from the measured vibration signal and noise is extracted from the measured sound wave signals (S121-S122).

In this case, the measured input and output signals are signal amplified and subjected to low pass filtering (200 in FIG. 4), and the filtered input and output signals are converted from a time domain to a frequency domain (for example, a fast Fourier transform (FFT)). (Refer to 300 in FIG. 4) to extract the resonant frequency and noise.

In this state, the bolt loosening of the structure and the sensitivity of the extracted input and output measurement signals (Input signal x (t), Output signal y (t)) (400a, 400b of Figure 4) is analyzed (S130).

At this time, the sensitivity analysis is to calculate the natural frequency , Shear rate calculation , Close function calculation The process (500 of FIG. 4) is performed.

Then, the analyzed sensitivity results and the existing database Finally, through the data comparison and review with the normal signal constructed at (600 in FIG. 4) (S140), it is finally diagnosed whether the bolts of the transmission and distribution tower structure are loosened (700 in FIG. 4) (S150).

5A to 5C are diagrams illustrating an experimental apparatus and method for measuring a change in natural frequency and transmission rate due to bolt loosening according to a first embodiment of the present invention.

As shown in Figure 5a, by attaching the acceleration sensor to a specific locator of the transmission and distribution steel tower structure to obtain data. That is, after attaching four acceleration sensors in two directions as shown in FIG. 5B, the X-shaped member of A_point is excited with an impact hammer, and thus transmission rate data according to the excited bolt state of A_point can be obtained as shown in FIG. 5C.

Referring to FIG. 5C, the decrease in the transmission rate near 184 Hz of the acceleration sensor 1 was large, and the decrease in the transmission rate was observed at 188 Hz of the acceleration sensor 2. In addition, the transition of the first natural frequency was observed around 160 Hz.

The experimental results show that the limit range of the acceleration sensor can have accurate reliability in one ball.

6A to 6C are diagrams illustrating an experimental apparatus and a method for measuring changes in natural frequency and transmission rate due to bolt loosening according to another embodiment of the present invention.

In the experimental apparatus as shown in FIG. 5, the acceleration sensor is attached to a specific joint of the transmission and distribution steel tower structure to acquire data.

At this time, the experimental conditions are as shown in Figure 6a, test00: steady state, test01: all eight bolts loosened, test02: tighten three times, test03: tighten four times, test04: tighten two times, test05: tighten one times, test06: tightened 7 times, test07: tightened 8 times, test08: tightened 6 times, test09: tightened 5 times, test10: tightened 5 times. Graphs of the experimental results are as shown in Figures 6b and 6c.

According to the above test conditions, tighten the bolts of the 3rd and 4th stages and set the standard to the normal state, and loosen them all by 1 to 8 bolts and excite them at A_Point to change the transmission rate of the acceleration sensors 1 and 2 by the natural frequency ①. , ②, ③, ④, ⑤, ⑥ point was observed. The natural frequency and transmission rate of bolt tightening and bolt loosening changed so much that it was difficult to accurately determine the transition history.

Therefore, the field test shows that the natural frequency of the steady-state steel structure is compared with the natural frequency of the steel structure in which the bolt is loosened, and the reduction of the transmission rate and the transition of the natural frequency are apparent.

7A to 7F are diagrams showing an experimental apparatus and test result data for measuring a stiffness measurement limit range of a steel tower structure according to a third embodiment of the present invention.

As shown in Figure 7a, the experimental apparatus was attached to the four acceleration sensors in two directions, and experimented with an impact hammer on the bottom pillar of the X-type member bolt of A_point.

As a result of the experiment, the transition response of the pylon structure as shown in FIGS. 7b to 7f was obtained. In this case, the graphs of FIGS. 7B, 7C, 7D, 7E, and 7F show cases in which the first, second, third, fourth, and fifth pillars A_point are in order.

8A to 8C are diagrams illustrating an attachment position of an acceleration / sound sensor and an excitation point of an impact hammer according to a fourth embodiment of the present invention.

FIG. 8A shows the attachment position of the acceleration sensor, FIG. 8B shows the attachment position of the acoustic sensor, and FIG. 8C shows the excitation point of the impact hammer.

At this time, the accelerometer mounting position can be installed at any point where a lot of displacement occurs in a particular joint, the mounting position of the acoustic sensor can be installed at any point where a lot of bolts are fastened, impact hammer The point of excitation can be excitation anywhere of the point.

As described above, according to the above embodiment, the field test results have found that the fundamental low frequency frequencies affecting the bolt loosening are present in the range of 0 to 300 Hz, and through these results, whether the bolt is loosened in the frequency band of 0 to 300 Hz. Was found through frequency analysis.

In addition, the loosening position of the bolt occurs at the weak part of the upper part of the tower, so the acceleration sensor is fixed to the measuring position according to the type of the tower. I could build it.

9 is a flowchart illustrating a data collection process of the bolt loosening diagnosis apparatus according to the present invention.

First, in a state in which the diagnosis apparatus and the personal digital assistant (PDA) 80 according to the present invention are connected with a USB 50 cable (S201), a folder for storing data in the PDA 80 is created (S202). ).

Thereafter, the data stored in the diagnostic apparatus is transferred to the PDA 80 and stored (S203), and then, it is checked whether or not the data is completed (S204).

In this state, the flash memory of the memory unit 20 is reset and the system is initialized (S205).

Thereafter, the analysis program of the diagnostic apparatus is driven (S206), and then the reference data is read from the database (DB) in which the normal signal capable of diagnosing the bolt loosening is stored (S207), and the excitation of the impact hammer is measured. The data is read (S208).

Then, using the Fast Fourier Transform (FFT) theory, the two pieces of data are displayed on the screen of the PDA 80 as a graph (S209), and then the bolt data is diagnosed based on the result data. (S210, S211).

9 is a flowchart illustrating a data movement and analysis process of the bolt loosening diagnosis apparatus according to the present invention.

First, after the system initialization of the bolt loosening diagnosis device and the SRAM of the memory unit 20 are reset (S30), if the collection signal of the diagnosis device controller is large (S302), the collection is executed.

After having the structure of the transmission and distribution tower with the impact hammer in this state (S303), the measured analog values are converted into 2 ¹³ digital values and stored in the SRAM of the memory unit 20 (S304).

After completion of the excitation of the structure of the transmission and distribution tower, for example, about 10 times with an impact hammer (S305), data stored in the SRAM of the memory unit 20 is transferred and stored in a flash memory (S306). .

In this state, it is checked whether or not the data storage is completed (S307). If the data error does not occur when the storage is not completed, the data storage location is corrected and then stored again (S308).

As a result of the checking, when data storage is completed, the SRAM data of the memory unit 20 is reset (S309) to complete the data analysis process of the diagnosis state of the bolt loosening (S310).

As described above, according to the transmission and distribution pylon bolt loosening diagnosis apparatus and the method according to the present invention has the following effects.

First, the technical aspect can secure the diagnosis of bolt bolt loosening technology, and it is possible to easily check the fastening force in the general steel tower structure.

Second, in terms of economics, it is possible to reduce the cost of bolt loosening and tightening, and prevent accidents and losses caused by bolt loosening.

Therefore, the present invention can be used to check the tightening bolts of the steel tower under construction, it can also be used to check the fastening state for the truss structure in the power plant.

1 is an overall conceptual diagram of the bolt loosening diagnostic apparatus for the transmission and distribution tower structure according to the present invention.

Figure 2 is a detailed configuration of the bolt loosening diagnostic apparatus for the transmission and distribution tower structure according to the present invention.

3 is an overall flowchart showing a bolt loosening diagnosis method of the transmission and distribution tower structure according to the present invention.

4 is a detailed flowchart of the bolt loosening diagnosis method of FIG. 3.

5A to 5C are diagrams illustrating an experimental apparatus and method for measuring a change in natural frequency and transmission rate due to bolt loosening according to a first embodiment of the present invention.

6A to 6C are diagrams illustrating an experimental apparatus and a method for measuring changes in natural frequency and transmission rate due to bolt loosening according to a second embodiment of the present invention.

7A to 7F are diagrams showing an experimental apparatus and test result data for measuring a stiffness measurement limit range of a steel tower structure according to a third embodiment of the present invention.

8A to 8C are diagrams illustrating an attachment position of an acceleration / sound sensor and an excitation point of an impact hammer according to a fourth embodiment of the present invention.

9 is a flowchart illustrating a data collection process of the bolt loosening diagnosis apparatus according to the present invention.

10 is a flowchart illustrating a data movement and analysis process of the bolt loosening diagnosis apparatus according to the present invention.

Claims (9)

In the apparatus for diagnosing bolt loosening of transmission and distribution steel tower structure, Signal measuring means for measuring an input signal with an acceleration / acoustic sensor while measuring an input signal with a force hammer by an impact hammer from a specific end of a transmission and distribution steel tower structure; Filtering means for amplifying the input / output signal from the signal measuring means and performing low pass filtering; Conversion means for converting the input / output signal filtered from the filtering means from a time domain to a frequency domain by a fast Fourier transform (FFT) method; Calculation means for calculating a natural frequency, shear rate and a closeness function of the input-output signal converted from the conversion means; Diagnostic means for diagnosing bolt loosening of the transmission and distribution tower structure by comparing operation data from said computing means with normal signal data from an existing database; And And a display means for displaying the result data from said diagnosis means. 2. The apparatus of claim 1, wherein the specific portion of the transmission and distribution tower structure represents a region designated as at least one section of the tower structure. The method according to claim 1, wherein the acceleration sensor mounting position of the signal measuring means can be installed at any point where a lot of displacement occurs in a particular connection, the mounting position of the acoustic sensor at any point where a lot of bolts are fastened It is possible to install, the impact point of the impact hammer bolt loosening diagnostic apparatus of the transmission and distribution steel tower structure, characterized in that the excitation can be anywhere. The apparatus of claim 1, wherein the display means displays the result data using a personal digital assistant (PDA). In the diagnostic method of bolt loosening of transmission and distribution steel tower structure, Exciting the structure using an impact hammer; Measuring the vibration and sound wave signals generated by the excitation using an acceleration and sound sensor installed at a specific structure of the steel tower structure; Extracting a noise from a sound wave signal while extracting a resonant frequency from the measured vibration signal by using a fast Fourier transform (FFT) method; Analyzing the bolt loosening of the structure and the sensitivity of the measurement signal; Comparing and reviewing the analyzed sensitivity result data with data of a normal signal constructed in an existing database; On the basis of the results of the bolt unwinding diagnosis method of the transmission and distribution tower structure comprising the step of diagnosing the bolt unwinding structure. The method of claim 5, wherein the sensitivity analysis data includes natural frequency, a transmission rate, and a result of calculating a closeness function. The method of claim 5, wherein the data collection process of the bolt loosening diagnostic method Connecting a diagnostic device and a personal digital assistant (PDA) with a USB cable; Creating a folder to store data in the PDA; Transferring data stored in the diagnostic apparatus to a PDA and storing the data; Confirming whether or not the data has been stored; Resetting the memory of the diagnostic apparatus and initializing the system; Driving an analysis program of the diagnostic apparatus; Reading reference data from a database (DB) in which a normal signal capable of diagnosing bolt loosening is previously stored; Reading the excitation data measured by the excitation of the impact hammer; Displaying the two pieces of data graphically on the screen of the PDA using Fast Fourier Transform (FFT) theory; Diagnosing the bolt loosening of the transmission and distribution tower structure, characterized in that it further comprises the step of diagnosing the bolt loosening based on the result data. The method of claim 5, wherein the data movement and analysis of the bolt loosening diagnostic method Resetting the system and resetting the first memory unit of the bolt loosening diagnosis device; Performing a collection if the collection signal of the diagnostic apparatus controller is large; Having a structure of a transmission and distribution tower with an impact hammer; Converting the measured analog value into a digital value and storing the measured value in a first memory unit; Exciting the structure of the transmission and distribution tower again a predetermined number of times with the impact hammer; Transferring data stored in the first memory unit to a second memory unit; Checking whether or not the data storage is completed and resetting data of the first memory unit when the data storage is completed; And analyzing the data of the diagnosis state of the bolt loosening based on the result data. The transmission and distribution tower structure according to claim 8, wherein the first memory unit includes a high speed data input / output (SRAM), and the second memory unit includes a flash memory having a data storage space of 1 Gbit. To loosen the bolts.