JP6519810B2 - Method and apparatus for diagnosing internal abnormality and deterioration of transformer - Google Patents

Description

  The present invention relates to a method and an apparatus capable of easily diagnosing transformer internal abnormality and deterioration without shutting down an operating transformer.

  Transformers are an important component of power equipment. Since its service life is as long as several tens of years, it is important to be able to diagnose whether or not the transformer is operating without any problems during the service period, and to perform appropriate repair before failure. In addition, it is important from the aspect of securing the reliability of the equipment that it is important to take measures such as degradation diagnosis and update planning to what extent the equipment in use can continue to be used in the future. Is desired.

It is a commonly used means of machine equipment diagnosis to measure the strength of the machine by measuring the magnitude of the machine's vibration, and "experimental modal analysis" is known as a means to analyze the machine's vibration. (See Non-Patent Document 1).
In the experimental modal analysis, whether the object to be tested is struck with a hammer and shocked or a device called a vibrator is used to place it on a table that can be constantly oscillated at a single frequency, or contact The method of causing it to vibrate is adopted. In the former method, it is possible to test that the test object vibrates and damps at the natural frequency, and in the latter method, it is applied when the frequency is arbitrarily changed and the vibration experiment (frequency sweep excitation experiment) is performed. Related data of excitation force and response (frequency response function) can be obtained, and natural frequencies, eigenmodes, magnitudes of damping ratios, etc. mixed in a hidden manner in the data can be analyzed.

  Also, modeling the structure of a machine, establishing an equation of motion by force balance and energy principle, and solving it to determine natural frequency and natural mode is called "theoretical mode analysis". However, in theoretical mode analysis, it is difficult to solve the equation of motion analytically in a system with a large degree of freedom, and is often analyzed using a finite element method.

In the manufacture of mechanical devices, it is first to design the device to have the required functionality. However, the operation of the new device may generate unexpected vibration and noise, and the unexpected vibration and noise may make the device user uncomfortable. Therefore, in the business, improving vibration and noise characteristics will differentiate products from competitors, so in transformers, it is better to use a device that does not generate vibration or noise from the design stage, or Efforts have been made to measure vibration and noise characteristics to reduce vibration and noise.
As for transformers, each transformer manufacturer and each steel manufacturer have introduced measures to reduce noise in order to socially differentiate environmental protection and to differentiate them from other companies. For example, as shown in Non-Patent Documents 2 to 5, the natural frequencies of iron cores, windings, tanks, etc. are experimentally and analyzed from both sides of theory, and the natural frequency of the machine is close to twice the power supply frequency and resonates There are researches to reduce the noise by devising to avoid the problem and devising the shape of the core joint.

Although it is possible to actually hammer the structure inside the transformer with a hammer or vibrate it with a vibrator at the design and manufacturing stages of the transformer, such a vibration test can not be applied to a transformer in operation . Therefore, there has been proposed a method of diagnosing the inside of the transformer from the vibration or sound generated from the iron core or the winding, in which the current supplied to the transformer exerts an electromagnetic force on the iron core or the winding inside the transformer.
In Patent Document 1, instead of striking a transformer with a hammer, an excitation inrush current (a multiple of the rated current) is applied to the transformer, an impact force is applied using the electromagnetic mechanical force generated thereby, and a diagnosis based on the generated sound Is proposed.
In addition, Patent Document 2 describes a method of measuring the natural frequency of a transformer by exciting an iron core and a winding by changing an excitation frequency stepwise in a predetermined frequency range instead of using an exciter. . In this case, the transformer noise level for each excitation frequency is measured to obtain a frequency response function.

Patent No. 5691298 gazette JP 2008-82778 A Patent No. 2550066 Unexamined-Japanese-Patent No. 2010-271073 Unexamined-Japanese-Patent No. 4-318905

Akio Nagamatsu, ed., “Mode analysis and control of sound and vibration”, published by Corona, (1996) Maejima Masaaki, Sakurai Minoru "Recent Transformer Noise Reduction Technology" Hitachi Review, vol. 67 No. 2 (1985) Kiyoto Hiraishi, Yasuo Hori, Shigeru Shida "Short circuit strength of large capacity transformer winding" Hitachi Review, vol. 51 No. 6 (1969) Atsushi Katayanagi "Analysis of Transformer Tank Vibration" Takatake Review, vol. 56 No. 1 (2011) Mizokami Masato, Kurosaki Yosuke "Changes in noise and magnetostriction due to the junction type of transformer iron core" Electrology, vol. 134 No. 5 (2014) The Institute of Electrical Engineers of Japan Technical Report No. 1336, "Latest trends in transformer abnormality diagnosis technology using electrical and acoustic methods" (2015) Tanaka Motohachiro and Hori Yasuro ed. Ed. "Electromagnetic Vibration and Noise Design Method" Science Information Publishing Co., Ltd. (2015) Hirotaka Hanaomote, Tetsumi Takano, Noboru Otobe, Kenji Watanabe "Optical epoxy resin degradation diagnosis technology for molded transformers" Electrology A, Vol. 132 No. 11 (2012)

  In the prior art, passing a current with a stepwise change in the excitation inrush current and the excitation frequency in the transformer causes the transformer to generate a plurality of natural vibration modes, and their natural frequencies (hereinafter referred to as mechanical system characteristics) In order to diagnose the transformer in order to determine the frequency), an excitation force having a plurality of frequency components is applied to the iron core or the winding in the transformer. However, there is a problem that the operating transformer has to be shut down for testing because such a special current test can not be applied to the operating transformer.

  SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an apparatus and method for analyzing a transformer's vibrational response under operating conditions to diagnose the transformer.

The method for diagnosing internal abnormalities and deterioration of a transformer according to the present invention is a transformer having an iron core, a coil body, windings constituting the coil body, and a tank containing the coils, and the transformer vibration in the operating state, Using a vibration detector having detection sensitivity in the low frequency range to the audible sound range (1 Hz to 20 kHz), and using a means by signal processing using an electronic circuit or software, a predetermined load factor for the operating transformer can be obtained. in the vibration detector of a Fourier transform output waveform obtained at the position of the nodal smallest area of the tank surface vibration of the transformer in operation due to the electromagnetic force generated by the electric current which is added as a node of vibration to the results longitudinal axis vibration intensity, the peak of the horizontal axis results depicted in the graph is set to the frequency, the transformer tank surface running at a predetermined load factor by the vibration detector Comparing the peak results depicted in the graph that set the result ordinate vibration intensity and the horizontal axis the frequency output waveforms measured at a position deviated from the position of the node by Fourier transform, the measuring position of the node By changing from the position, the vibration of the frequency at which the vibration intensity indicated by the peak changes is grasped as the vibration of the tank, and the remaining vibration is grasped as iron core vibration or winding vibration, and the remaining iron core vibration or winding vibration The vibration intensity changes from the peak comparison of the Fourier transform results obtained by setting the measurement position of the vibration detector to the position of the node of vibration of the tank surface and changing the load factor from the predetermined load factor. Vibration of non-existent frequency is judged as iron core vibration, vibration of frequency whose vibration intensity is weakened is judged as winding vibration, and either or both of iron core vibration and winding vibration are paired with a sound transformer. It is characterized in that when there is a change as compared with one or both of the iron core vibration and the winding vibration obtained by the method equivalent to the above method, it is judged that the internal abnormality and the deterioration have occurred .
In the present invention, it is possible to analyze changes in time of one or both of the iron core vibration and the winding vibration determined previously and analyze the state of the operating transformer.

The present invention is a transformer having an iron core, a coil body, a winding constituting the coil body, and a tank accommodating the coils, and an electronic circuit or software using a vibration detector for operating transformer vibration. The smallest area of tank surface vibration of the operating transformer due to the electromagnetic force generated by the energizing current applied to the operating transformer at a predetermined load factor by means of signal processing using hardware Measuring the output waveform of the vibration detector at the position of the node with the node of the vibration, extracting an integer multiple of the transformer power supply frequency from the output waveform, and standardizing the amplitude of the integer multiple, The phase difference between the two waveforms is determined by comparing the normalized waveform of the amplitude of the same integer multiple wave and the same frequency from the power supply current waveform of the transformer, and the phase difference and variation measured with a sound transformer are present. Internal error and Characterized by determining that resulted in deterioration.
In the present invention, it is possible to analyze that the phase difference changes with time and analyze the state of the operating transformer.

The present invention is a device for diagnosing internal abnormalities and deterioration of a transformer applied to a transformer having an iron core, a coil body, a winding constituting the coil body, and a tank accommodating the coils, which is in operation. A vibration detector mounted on a transformer and having detection sensitivity to vibration ranging from a low frequency region generated by the transformer to an audible sound region (1 Hz to 20 kHz), and a detection signal from the vibration detector. The analyzer comprises: an analyzer for obtaining mechanical vibration associated with an excitation force due to current flowing to the operating transformer; and calculation means for calculating data obtained from the analyzer, the calculation means comprising an electronic circuit or software the smallest area of the transformer operating status due to the electromagnetic force generated by energizing current being added at a predetermined load ratio in operation transformer tank surface vibration using means by signal processing using Longitudinal axis vibration intensity results output waveform obtained from the vibration detector at the position of the nodal as a node of vibration by Fourier transform, the peak of the results depicted in the graph set on the horizontal axis the frequency, the predetermined load Fourier transform the output waveform measured at a position away from the position of the node of the vibration of the tank surface of the transformer in operation, and draw the result on the graph set to the vertical axis vibration intensity and horizontal axis frequency By comparing the peak with the peak and changing the measurement position to the position of the node and the position away from it , the vibration of the frequency at which the vibration intensity indicated by the peak changes is grasped as the vibration of the tank, and the remaining vibration is iron core vibration Alternatively, it is grasped as winding vibration, and regarding the remaining iron core vibration or winding vibration, the measurement position of the vibration detector is set to the position of the node of vibration of the tank surface, and the load factor is determined from the predetermined load factor. From the peak comparison of the Fourier transform results obtained by changing, it is determined that the vibration in which the vibration intensity does not change is an iron core vibration, the vibration in which the vibration intensity is weakened is determined as a winding vibration, and the iron core vibration and the winding vibration The computing means determines that an internal abnormality and deterioration have occurred when there is a change in one or both of the sound transformer and the iron core vibration and the winding vibration obtained by the equivalent method with respect to the sound transformer. It is characterized by having the following function .

The present invention is a device for diagnosing internal abnormalities and deterioration of a transformer applied to a transformer having an iron core, a coil body, a winding constituting the coil body, and a tank accommodating the coils, which is in operation. A vibration detector attached to the transformer, an analyzer for obtaining mechanical vibration accompanying an excitation force by the supplied current to the operating transformer in response to a detection signal from the vibration detector; Calculation means for calculating the stored data, and for the transformer vibration in the operating state, using the vibration detector, using the means by signal processing using an electronic circuit or software to specify the transformer in the operating state; Measuring the output waveform of the vibration detector at the position of the node with the smallest area of the tank surface vibration of the operating transformer due to the electromagnetic force generated by the applied current at a load factor of The integer harmonics of the transformer power supply frequency are extracted from the output waveform, and the amplitude of the integer harmonics is standardized from the power supply current waveform of the transformer and the waveform in which the amplitude of the integer harmonics is normalized. The calculation means has a function of determining the phase difference between the two waveforms by comparing the obtained waveforms, and determining that internal abnormality and deterioration have occurred when there is a change in phase difference measured with a sound transformer. It features.

According to the diagnostic method of the present invention, it is possible to externally diagnose internal abnormalities and deterioration in the operating state without stopping the operating transformer.
Moreover, in the frequency response analysis in electrical vibration, although an abnormality is diagnosed after an iron core and a coil actually produce a shift, in the diagnostic method according to the present invention, a decrease in tightening force of a coil winding can be diagnosed. Since it can be done, it is a method that can grasp abnormalities before the deviation actually occurs, and it is an excellent diagnostic method as a method of preventive maintenance of transformers.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows 1st Embodiment of the apparatus which diagnoses abnormality and deterioration of the transformer which concerns on this invention. An example structure of the transformer made into the measurement object by this invention is shown, (A) is the perspective schematic view which made one part fracture, (B) is an expanded sectional view of a coil part. The block diagram of a one-degree-of-freedom dynamic model used as a reference when making an equation of motion by approximating the vibration of a transformer winding. The graph which shows an example of the vibration detection waveform by the laser displacement meter measured from wall surface center vicinity of the working transformer tank. The graph which shows an example of the waveform obtained by Fourier-transforming the waveform shown in FIG. The graph which shows the waveform of the result of extracting the 2nd harmonic (component of 100 Hz) of a power supply frequency from the waveform shown in FIG. The graph which shows the phase difference of the waveform which squared the power supply current waveform of a transformer, and normalized the 100 Hz component, and the waveform shown in FIG. The figure which shows an example of the method of calculating | requiring the coefficient of a viscosity term using a high frequency component. The graph which shows an example of the waveform which Fourier-transformed the output waveform of AE sensor measured in the wall surface center of a tank in the transformer in operation with 60% of a load factor. The graph which displayed the vertical axis | shaft on the logarithmic scale about the waveform shown in FIG. The graph which shows an example of the waveform which Fourier-transformed the output waveform of AE sensor measured in the 65-cm lower position from a tank center, when calculating | requiring the waveform shown in FIG. The graph which shows an example of the waveform which Fourier-transformed the output waveform of AE sensor measured in the wall surface center of a tank in a transformer in operation with 30% of a load factor. The figure explaining an example of the measurement by a compensation method. The perspective view which shows the outline | summary of the transformer tank applied to the test in the Example. FIG. 14 shows the vibration mode of the iron core housed in the transformer tank shown in FIG. 14, (A) is a perspective view showing a twisting mode, (B) is a perspective view showing a bending mode 1 and (C) is a bending mode FIG. Explanatory drawing which shows the position which attached the sensor to the upper right side wall of the transformer tank in the Example. The graph which shows the value which Fourier-transformed the vibration measurement result at the time of real operation of the transformer tank obtained in the Example, and excitation.

First Embodiment
Hereinafter, a first embodiment of a method and an apparatus for diagnosing abnormality and deterioration of a transformer according to the present invention will be described based on the drawings taking an oil-filled transformer as an example.
FIG. 1 is a block diagram showing a first embodiment of a device for diagnosing abnormality and deterioration of a transformer, and a diagnosis device A of this embodiment is an abnormality of oil-filled transformer 1 having a structure shown in FIG. 2 as an example. It is a device that diagnoses deterioration.
In the oil-filled transformer 1 of this example, a plurality of winding type coil bodies 3 are accommodated inside the tank 2 with their central axes up and down, and the inside of the tank 2 is filled with insulating oil. The iron cores 5 made of magnetic material such as silicon steel plate are inserted into the central part of each coil body 3, and each iron core 5 is integrated with the rod-like yoke 6 made of magnetic material such as silicon steel plate at each upper and lower end. ing.
Frame-like clamps 7 are provided so as to surround both ends of each iron core 5 and the periphery of the yoke 6, and the clamps 8 extend from the upper and lower clamps 7 as shown in FIG. 2 (B). The coil bodies 3 are sandwiched from above and below by the upper and lower clamps 8, and a clamping force is applied to each coil body 3.

In the present embodiment, as shown in FIG. 2B, the coil body 3 is composed of an outer coil 9 and an inner coil 10, and the outer coil (primary coil) 9 is an outer winding (primary winding) 11 and an insulating spacer A stacked body in which (solid insulators) 12 are stacked up and down is sandwiched between an upper insulator 13 and a lower insulator 15. The inner coil (secondary coil) 10 is configured by sandwiching a stacked body in which an inner winding (secondary winding) 16 and an insulating spacer (solid insulator) 17 are stacked up and down with an upper insulator 18 and a lower insulator 19. It is done.
By clamping the upper insulators 13 and 18 and the lower insulators 15 and 19 with the upper and lower clamps 8, a clamping force is applied to each coil body 3 from the upper and lower sides, and in this state, the coil body 3 is immersed in the insulating oil ing.
Further, a bushing (not shown) for inputting and outputting electric power is formed on the ceiling of the tank 2 or on the side of the tank.

Since the transformer 1 of the said structure is used for the application etc. which pressure | voltage-falls the high voltage sent from a power transmission line etc. in the vicinity of a power user, current always flows through the winding 11 and 16. Since an electromagnetic force acts by supplying an electric current to the windings 11 and 16, the electromagnetic force acts on the coil body 3 and the iron core 5 to vibrate them. This vibration is transmitted to the whole of the transformer 1, and is also transmitted to the side wall 2A, the bottom wall 2B, and the ceiling wall 2C of the tank 2.
In addition, when a short circuit accident or a ground fault accident occurs in a transmission line, a large current that may reach 10 times to several tens times the rated load current may flow in the windings 11 and 16 of the transformer 1, Forces and vibrations may also act on the transformer 1.
Due to these various factors, the insulating oil of the transformer 1 gradually deteriorates with time. In addition, since the insulating spacers 12 and 17 on which clamping force and vibration always act are made of cellulose fiber, they may be deteriorated, and unexpected deterioration is also caused on the windings 11 and 16 due to a short circuit accident or a ground accident. It may occur.
As described above, the use of the transformer 1 for a long time may cause deterioration in each part.

  The diagnostic device A for abnormality and deterioration of the transformer 1 shown in FIG. 1 receives and amplifies a vibration detector (vibration sensor) 22 disposed along the transformer 1 and an output signal from the vibration detector 22. An amplifier (vibration sensor amplifier) 25 and a signal analyzer (phase difference detector) 26 receiving an output from the amplifier 25 and an arithmetic unit 27 connected to the signal analyzer 26 are mainly configured. In the diagnostic device A, a voltmeter (energization voltmeter) 23 for measuring a voltage for energizing the transformer 1 and a signal analyzer 26 are connected to the voltmeter 23 via an amplifier (energization voltage amplifier) 24.

Although the vibration of the transformer 1 is analyzed by the procedure described below using the diagnostic device A shown in FIG. 1, a basic theory according to the experimental mode analysis used when the diagnostic device A of the present embodiment diagnoses an abnormality and deterioration. Will be described below.
First, an equation of motion is made by approximating the vibration of a transformer winding as a damped forced vibration in a system of one degree of freedom. The mass of the winding is represented by m, the stiffness by k, and the viscosity by c (damping factor). The stiffness k is represented by a spring, and the viscosity c is represented by a damper as shown in FIG. This mechanical model with degrees of freedom is described in Non-Patent Document 1.
The displacement at time t is represented by x (t), and the equation of motion in the case of applying a harmonic excitation force of magnitude F and angular frequency ω can be represented by the following equation (1).

  The following equations (3) and (4) can be obtained by solving the displacement x assuming the following equation (2) in the equation (1).

Here, in the equations (3) and (4), Ω = (k / m) ^1/2 represents the undamped natural angular frequency, and β = ω / Ω represents the angular frequency of the external force and the undamped natural angular vibration The ratio of numbers is shown, c _c = 2 (m / k) ^1/2 is the critical damping coefficient, and ζ = c / _cc is the damping ratio (ratio of viscous damping to critical damping coefficient).
The equation (4) can be expanded into the following equations (5) to (9) as a vibration equation of the angular frequency ω whose phase is delayed from the harmonic excitation force.

  In the equation (9), the phase difference φ is given by the following equation (10).

  Therefore, the displacement X assumed by the equation (2) is given by the following equation (11).

  The equation (1) is an inhomogeneous linear differential equation because the right side is not zero. The general solution of an inhomogeneous linear differential equation can be written as the general solution of a linear homogeneous equation and the sum of one special solution that satisfies the inhomogeneous equation. The equation (4) is one special solution satisfying the equation (1) of the nonhomogeneous equation. Here, the linear homogeneous equation is given by the following equation (12).

  If the general solution of the equation (12) is obtained, the following equation (13) is obtained.

  The following equation (14) holds in the equation (13).

The above equation (14) has a square root, and different phenomena appear depending on whether the contents are positive or negative.
When ζ 1 ₁ , both λ ₁ and λ ₂ become negative real numbers, and the magnitude decreases with time, resulting in aperiodic motion approaching zero. Therefore, in this case, the general solution of the equation (1) is represented by the sum of the vibration of the angular frequency ω of the harmonic excitation force given by the equation (11) and the aperiodic motion given by the equation (13) Be done.
In the case of ζ <1, σ = Ωζ: Attenuation rate, ω _D = Ω (1−ζ ² ) ^1/2 : When the damped natural angular frequency is introduced, the above equation (13) is expressed by the following equation (15) be able to.

Therefore, in this case, the general solution of the equation (1) includes two of the angular frequency ω of the harmonic excitation force given by the equation (11) and the damped natural angular frequency ω _D given by the equation (15) It becomes a vibration with a component.
On the other hand, an equation of motion when an external force {f} acts on an N degree of freedom system is expressed by the following equation (16).

However, in said (16) Formula, [M] is a mass matrix, [C] is an attenuation matrix, [K] represents a stiffness matrix, and it is an N-dimensional square matrix, respectively.
Generally, in N-dimensional space, if there are _N mutually independent vector groups {φ ₁ } to {φ _N }, form a coordinate system based on them, thereby representing an arbitrary N-dimensional vector The expression is given by the following equations (17) and (18).

Since an N-degrees-of-freedom system is considered to form an N-dimensional space, it is an N-dimensional vector group having general orthogonality with respect to mass matrix [M], attenuation matrix [C], and stiffness matrix [K]. A coordinate system can be formed to be a reference vector.
Then, the equation of motion (16) of the N degree of freedom system reduces to the following equation of motion (19) of the one degree of freedom system relating to the r th -order eigenmode.

In the above equation (19), m _r = {ψ _r } ^T [M] {ψ _r }: mode mass, _cr = {ψ _r } ^T [C] {ψ _r }: mode damping coefficient, k _r = { ψ _r } ^T [K] {ψ _r }: mode stiffness.
When the harmonic excitation force with angular frequency ω and amplitude Fi acts only on the degree of freedom i in the multi-degree-of-freedom system, the external force vector {f} has all other terms in the _i- th row F _i e ^jωt. Becomes zero. Substituting this into the equation (19) gives the following equation (20).

In the equation (20), _{ri ri} is a term in the i-th row of the _{r th} eigenmode {モ ー ド_r }.
The equation (20) has the same form as the equation (1) in a single degree of freedom system.
Assuming that the solution ξ _r is expressed as a harmonic function, the solution is the following equation (21) for the r th -order eigenmode.

  Substituting this into the equation (18) and summing the all eigenmodes, the following equation (22) can be obtained as a solution on spatial coordinates.

  The above equation (16) is an inhomogeneous linear differential equation because the right side is not zero. The general solution of the above equation (16) can also be described by the general solution of a linear homogeneous equation and the sum of one special solution satisfying an inhomogeneous equation. The equation (22) is one special solution that satisfies the equation (16), which is an inhomogeneous equation. Here, the linear homogeneous equation is given by the following equation (23).

  The general solution of this equation (23) is obtained. The following can be considered with an example where the damping matrix [C] is proportional viscosity damping as represented by the following equation (24).

  Here, the displacement is assumed to be the following equation (25).

  Then, the equation (23) can be expressed by the following equation (26).

  Here, when the equation (24) is substituted into the equation (26) and the equation (27) below is set, the equation (23) becomes the following equation (28).

  Here, when p obtained by solving the equation (28) is substituted into the equation (27), the r-order λr can be obtained as the following equation (29).

  Here, the natural angular frequency is represented by the following equation (30), the mode damping factor is represented by the following equation (31), and the damped natural angular frequency is represented by the following equation (32). The modal damping ratio of is expressed by the following equation (33).

From the above, the general solution of the equation (16) is the damped angular natural angular frequency which appears in the equation (32) which indicates the angular frequency ω of the harmonic excitation force and the damped natural angular frequency given by the equation (22) It is a vibration with a component of ω _rd .

On the other hand, the propagation path of the vibration and noise generated by the transformer in the operating state is described in the above-mentioned Non-Patent Document 2.
The primary causes of vibration and noise are core core vibration and winding vibration, and both vibrations are transmitted to the tank and others. Thus, the vibration of the transformer tank is a combination of iron core vibration, winding vibration and tank's own vibration. When diagnosing the state of the iron core, the core vibration component is evaluated among the energized noise and vibration, and when diagnosing the state of the winding, the winding vibration component is evaluated. The iron core vibration and the winding vibration each have a natural frequency.
When the natural frequency is close to the frequency of the power supply system, a resonance phenomenon occurs. The excitation power is the largest of the double power supply frequency, but there is also an odd or even multiple of the power supply frequency, and the natural frequency of iron core vibration, winding vibration and tank vibration is other than twice power frequency If the frequency is close to an integral multiple of, the amplitude may be larger than the vibration of the double component of the power supply frequency. The natural frequency of the mechanical system with respect to the excitation force of the power supply system can be measured to diagnose internal abnormality and deterioration of the transformer. In addition, when direct measurement of the natural frequency is difficult because the natural vibration amplitude of the mechanical system is small, etc., the natural frequency of the mechanical system is determined by analyzing the phase difference of the forced vibration, and claim As described in 3, the transformer internal abnormality and deterioration diagnosis can be performed.
That is, it is possible to analyze the state of the transformer in operation by obtaining the natural frequency of the transformer component (the natural frequency of each of the core vibration, the winding vibration and the vibration of the tank itself).

Basically, the excitation force is twice the power source frequency. However, it is considered that vibrations with various natural frequencies are induced due to distortion of power supply voltage, distortion of generated magnetic force, distortion of transmitted force and the like.
The procedure of dividing the vibration of the tank 2 in the transformer 1 into the three components of iron core vibration, winding vibration and tank vibration will be described. It is assumed that the three component vibration holds the principle of superposition.
When the vibration is measured at the center of the tank wall, the tank vibration having an even number of antinodes in the longitudinal direction or in the lateral direction is a node of vibration, and only the tank vibration component having an odd antinode in both longitudinal and lateral directions. Therefore, when vibration is measured at the center of the tank wall surface, the vibration waveform is a superposition of the tank vibration component having odd antinodes in both the vertical and horizontal directions and the iron core vibration and the winding vibration. Next, if the vibration is measured at a position slightly lower than the center of the tank, the tank vibration with an even number of longitudinal method or lateral direction which has disappeared in the center of the tank is measured. The component has smaller amplitude.

On the other hand, the magnitudes of iron core vibration and winding vibration do not change. By measuring the position of the tank surface in this way, the natural vibration component can be grasped for all tank vibrations, and the remaining is the separation of the core vibration and the winding vibration.
Since the magnetic flux in the iron core does not change depending on the presence or absence of load current, iron core vibration does not change, but it is described on page 87 of Non-Patent Document 6 that winding vibration changes in proportion to the current squared. ing. Therefore, the load current is changed to measure the vibration, and by using the load dependency, it is possible to separate the iron core vibration and the winding vibration and to measure each vibration waveform.

"Analysis of winding vibration"
Next, an analysis example of winding vibration will be described.
The life of a general oil-filled transformer is considered to be a state in which the insulating paper of the coil can not withstand the electromagnetic mechanical force applied to the transformer coil winding when a short circuit failure occurs outside the transformer.
On the other hand, at the time of a short circuit failure, an electromagnetic force (external thrust) which the primary winding (outer winding) and the secondary winding (inner winding) repel also acts in the axial direction of the winding. If the insulator inserted in the winding portion shrinks due to age deterioration and the clamping force of the winding decreases, the external thrust may possibly damage the axial winding structure. Such a condition is considered to be the life of the transformer. If the tightening force is reduced and the winding becomes loose, the noise from the winding increases.
According to the description of Patent Document 4, when the tightening torque value of each portion of the transformer becomes smaller than the specified value, it is described that the level of each frequency component in normal time is a level largely deviated from the distribution range.

Next, the excitation force applied to the transformer winding will be described.
Current flows in the opposite direction in the inner winding 16 and the outer winding 11 of the transformer winding, forming a leakage magnetic field. The electromagnetic force applied to the winding is the Lorentz force, which acts perpendicular to the current and the magnetic field, respectively. The electromagnetic force in the axial direction is a compressive force for both the inner winding 16 and the outer winding 11, and the electromagnetic force is proportional to the square of the current. Therefore, the frequency of the oscillating force in the axial direction is twice the frequency of the current (ie, the power supply frequency).
The decrease in the clamping force of the windings 11 and 16 appears as a change in the natural frequency of the windings. Therefore, it is only necessary to clarify the vibration component included in the winding vibration by using the compensation method described below or directly by experimental modal analysis. Direct means that the raw waveform of the AE sensor or the acceleration sensor is subjected to Fourier transform to reveal the vibration component.

Next, the natural frequency of the winding can be determined with respect to the frequency of the power supply from the phase difference φ (the difference in the phase of the transformer vibration with respect to the phase of the excitation force due to the current flow). It is assumed that the vibration mode having a large signal strength due to the effect of twice the power supply frequency or resonance is the r-th mode. Assuming that the phase difference with respect to the r-th mode is φr, the r-th natural frequency Ω _r of the winding can be calculated using the equation (10) as in the following equation (34). At that time, the attenuation coefficient _cr is determined from another experiment.

Among the vibration of the transformer, the amplitude is small but free vibration can be determined directly or by measurement using a compensation method and a lock-in amplifier described later.
The method of determining the damping coefficient c is a method of measuring the mode i having a natural frequency several times larger than the frequency of the excitation force. The value of the damping coefficient c is considered to be different for each mode, but can be approximated by the value also in the frequency of the excitation force.
In that case, the damping coefficient c _i is determined from the damping motion for several cycles that appear before one cycle of the excitation force elapses. FIG. 8 is an explanation of the waveform.
In general, the amplitude of the damped free oscillation waveform decays exponentially. Therefore, I thought to always be a constant value when taking the logarithm of the ratio of adjacent amplitudes, the natural logarithm of the ratio of the adjacent amplitude is called the logarithmic decrement of [delta] _i. Assuming that the n-th amplitude at time t _n is a _n and the n + 1,..., N + m-th amplitudes are a _{n + 1} ,..., A _{n + m} , the logarithmic attenuation factor δ _i is defined by the following equation (35).

When approximating that δ _r is equal to δ _i , the r-order mode damping ratio ζ _r can be obtained by the following equation (36).

Thus, the damping coefficient _{c r} is calculated by the following equation (37).

  The relationship between the natural frequency of the winding and the clamping force is given by the following equation (38).

  Here, L represents the axial length of the winding, and ρ represents the linear density when the winding is regarded as a distributed constant system. Further, from the equations (34) and (38), the tightening force T can be determined as the following equation (39).

The natural frequency of the winding can also be determined using the modal damping ratio by dividing the damping natural angular frequency of the equation (32) in free vibration by 2π.
However, when the transformer is relatively new, the winding tightening force is sufficiently large that vibration hardly occurs. That is, it is considered that the damping coefficient c is larger than the critical damping coefficient c _c and the damping ratio ζ is larger than one. In that case, no vibration related to the natural frequency occurs, resulting in aperiodic damping motion. As a result, even if the forced vibration is applied, vibration components other than the frequency of the forced vibration do not occur. Even in such a case, if it is a method of measuring phase delay, information on natural frequency can be obtained.

When the tightening force T determined by the equation (39) is equal to or more than the design lower limit value of the transformer, the deterioration degree of the transformer is diagnosed as healthy. It can be determined that the transformer has reached the end of its life.
As an example, the analyzer 26 and the arithmetic unit 27 shown in FIG. 1 are constituted by a personal computer, the arithmetic unit 27 is a CPU, and a storage device such as a memory or a hard disk is mounted on the analyzer 26. The information of the tightening force T of the transformer in a sound initial state is stored. Each equation described above is recorded in the storage device of the analyzer 26, and information such as the natural frequency of the winding obtained from the measurement result is recorded in the storage device of the analyzer 26, and the transformer in the sound initial state A comparison with the clamping force is made.
A comparison table is recorded in the storage device of the analyzer 26 according to what percentage of a drop is found with respect to the tightening force of the sound transformer in the initial state and the tightening force. If it is found that the decrease in the tightening force actually measured and calculated by the arithmetic device 27 is lower than the initial state, it is diagnosed whether or not the deterioration degree of the transformer has reached the end of life . The reference value for diagnosis is set individually for each transformer. It is possible to diagnose the life of the transformer by recording the reference value of the diagnosis in the storage device of the analyzer 26 and comparing and judging the measurement result of the arithmetic unit 27 and the table.

When the natural frequency of a mechanical system is determined from the phase difference, if the deterioration of the insulator used in the winding part is mild, the vibration twice as high as the power supply frequency (the vibration twice) is the main transformer vibration. It is good to analyze paying attention to the phase difference of double vibration.
However, if the natural frequency of the mechanical system is close to a frequency that is an integral multiple of the frequency twice the frequency of the power supply frequency, the effect of resonance may give a larger vibration amplitude, in which case the large amplitude Sometimes it is better to analyze the frequency component of.

  If the tightening force decreases, in addition to the electromagnetic force acting in the axial direction of the winding, it is considered that the vibration due to the electromagnetic force acting in the radial direction of the winding is also generated. It is believed that the amplitude of Therefore, it is effective to analyze by focusing on the amplitude of the high-order vibration component for the transformer that has deteriorated.

The transient vibration due to the high-order natural vibration mode is considered as a vibration component to be added to the steady-state vibration shown by the equation (22), and is given by the equation (25).
Although Lorentz force generated by energization of the transformer is used as excitation force in this embodiment, the excitation force is only one frequency component and can not be efficient excitation force for all vibration modes. there is a possibility. However, if the winding tightening force becomes weak in the degraded transformer, the winding loosens and the vibration force of the single vibration is distorted and transmitted, causing various modes of vibration to be induced. Conceivable.
Therefore, it can be diagnosed that the insulator used in the winding part is deteriorated by grasping that the amplitude of the higher order vibration component becomes larger with respect to the double vibration amplitude. In this case, higher order vibration components are considered to be distorted and to have a fixed phase delay due to the transmitted excitation force.
Therefore, by removing background noise whose phase is not constant, it is possible to grasp high-order vibration components that cause a phase delay determined by the distorted and transmitted excitation force, and to use the insulator used in the winding part An increase in the amplitude of higher order vibration components related to the degradation of
However, the internal stress at the transformer manufacturing stage may be relieved over time, and the high-order vibration amplitude may be reduced, and the cause of the change must be interpreted to diagnose the transformer. Therefore, the fact that the specific frequency component determined for each transformer changes over time is analyzed to analyze and diagnose the state of the operating transformer. The reference value for diagnosis is set individually for each transformer.
As an example, if the analyzer 26 shown in FIG. 1 analyzes the graph of the measurement result and recognizes an increase in the high-order natural vibration, the degree of deterioration of the transformer 1 is calculated. The rate of increase of the high-order natural vibration is recorded in advance in the storage device of the analyzer 26 according to the degree of deterioration, and to what extent is the degree of deterioration of the transformer concerned according to the rate of increase calculated by the arithmetic unit 27 Also, it is diagnosed whether or not the life as a transformer has been reached.

An AE (Acoustic Emission) sensor having a wide frequency characteristic can be used to widely analyze from the low-order double vibration component to the high-order natural vibration component. Alternatively, it is possible to use a combination of low frequency and high frequency and high sensitivity AE sensors. Alternatively, high sensitivity AE sensors can be used in combination for each specific frequency.
In addition, if it is a sensor that measures vibration, it is not limited to an AE sensor, but it is not limited to an acceleration sensor or a method of measuring vibration with sound waves or analyzing vibration of the transformer tank wall directly with a laser displacement meter Is also possible.

"Analysis of core vibration"
Next, an analysis example of core vibration will be described.
The iron core is vibrated by the magnetostriction of the magnetic steel sheet. The magnetostriction generates vibration twice each time the direction of the magnetic field changes, that is, for one cycle of the supplied current. The transformer core is screwed or tightened with a band. When a transformer has been used for many years, repeated vibration or temperature change may cause the screw to loosen and reduce the tightening force.
Due to the magnetostriction of the magnetic steel sheet, the yoke (leg) of the iron core and the leg iron (core) are shaken and vibrated (see Non-Patent Document 6). If the tightening force of the iron core decreases, vibration occurs and the noise increases.
At the joints of the core, there is a slight air layer, and the magnetic flux passes through the steel plate avoiding the air portion, so that a suction force is exerted between the steel plates. The laminated steel plates are not completely flat but in partial contact and act as a spring as a whole in the laminating direction. The spring constant changes with the tightening force. In addition, if the tightening force becomes weak, slippage between the steel plates occurs, and the damping coefficient decreases.
Therefore, when the tightening force changes, the natural frequency changes as the change of the spring constant or the damping coefficient. By detecting changes in the natural frequency and the damping coefficient, it is possible to diagnose abnormalities or deterioration such as a decrease in clamping force of the iron core.
As an example, if the analyzer 26 shown in FIG. 1 analyzes the graph of the measurement result and recognizes the degree of decrease in the tightening force, the degree of deterioration of the transformer 1 is calculated. The rate of decrease in tightening force is recorded in advance in the storage device of the analyzer 26 according to the rate of decrease, and the degree of deterioration of the transformer according to the rate of decrease is also the life as a transformer It is diagnosed whether it has reached.
The reference value for diagnosis is set individually for each transformer.

"Analysis of dry transformers"
Next, diagnosis by vibration analysis of the dry type transformer will be described.
The dry type transformer is also called a molded transformer, and is made by immersing and hardening the inside of the transformer with an insulating epoxy resin instead of the insulating oil. Therefore, the main deterioration factor of the dry type transformer is the thermal deterioration of the epoxy resin (see Non-Patent Document 8).
When the epoxy resin is thermally deteriorated, the mechanical strength is reduced, and when a crack is generated due to an external force such as a short circuit current or an earthquake, a possibility of causing an insulation breakdown occurs. When the epoxy resin is thermally deteriorated, the natural frequency of the transformer is changed due to the evaporation of the epoxy resin and the decrease in mass.
Therefore, it is possible to diagnose abnormalities and deterioration by vibration analysis also for dry type transformers. In the case of a molded transformer in which an iron core and a winding are combined and resin-cured, the vibration of the container surface is measured.
In the case of a molded transformer in which the core and the winding are resin-hardened separately or in the case of a molded transformer in which only the wire is resin-hardened, the iron core and the winding vibrate separately. Vibration can be measured individually, and as with oil-filled transformers, diagnosis of abnormality and deterioration of iron core and winding can be performed.
As an example, the individual vibration state of the iron core or the winding of the transformer in a sound initial state is recorded in the storage device of the analyzer 26 shown in FIG. 1 and the ratio changed by comparing with the actual measurement result. It is possible to diagnose whether the degree of deterioration of the transformer is, and whether or not the life as a transformer has been reached.

In order to solve the above-described conventional problems, in the present embodiment, in the operating transformer, the amplitude and phase of the vibration are measured and compared with the amplitude and phase of the power supply voltage, and the abnormality and deterioration inside the transformer are It is a method of diagnosis. There is no need to apply a special current for diagnosis.
In the present embodiment, only the electromagnetic force generated by energization of the operating transformer is used as a source of excitation force that vibrates the iron core or the winding of the transformer. Therefore, the prior art Patent Document 2 is equivalent to limiting the excitation frequency to only the commercial frequency, and the diagnosis method of the present embodiment is partially similar to the method described in Patent Document 2, but in Patent Document 2 The measurement results for each frequency in which the frequency is changed stepwise are one set, and this is a method of analyzing the natural frequency.
On the other hand, in the diagnostic method of the present embodiment, the frequency of energization causing the vibration is basically only one, which is twice the power supply frequency, which is a big difference. It is important to capture various vibrations generated depending on the tightening condition of the iron core or the winding and the condition of heat deterioration of the epoxy resin focusing on this exciting force and compare it with the frequency of energization.

Further, although the power supply current causing the vibration in the present embodiment is only one frequency component, various modes are involved due to distortion of power supply voltage, distortion of generated magnetic force, distortion of transmitted force, and the like. It is thought that the vibration of is induced.
The power supply voltage is ideally a sine wave, but it is conceivable that the excitation wave itself includes harmonics due to distortion of the sine wave depending on the power supply stage and the contents of the load side connection device.
With regard to core vibration, the magnetic field generated by the excitation current is the source of core vibration, but the magnetic flux density includes harmonics due to the non-linearity of the magnetic saturation curve of the core. In addition, since there is non-linearity between the magnetization of the iron core and the magnetostriction, an excitation force of a frequency component different from the power supply voltage is also induced.
In the case of winding vibration, Lorentz force is generated from the leakage flux of the winding and the current flowing in the winding, but the leakage flux is distorted from the sinusoidal change due to the wiring and the bias of the winding method, An excitation force of a frequency component different from the power supply voltage is also induced.

In general transformers, iron cores are laminated with thin electromagnetic steel plates and screwed or clamped with a band. Also, the winding is tightened through a clamping screw. The iron core or winding that receives clamping force corresponds to a kind of spring, and the spring constant is changed due to the clamping force and non-uniformity of the clamping force causes the clamping force to be distorted and transmitted, which is different from the excitation force It induces oscillations of frequency components. Therefore, it is possible to obtain information on natural vibration modes of frequency components different from twice the power supply frequency without supplying a special current for diagnosis.
In that case, the main frequency component of the excitation force is an integral multiple of the power supply frequency (referred to as the natural frequency of the power supply system), and the even-multiple component is larger than the odd-multiple component. Is the largest of the double components. In addition, it contains a small component but also any frequency component other than an integral multiple of the power supply frequency, and excites free vibration of the iron core and the winding.

In addition, as the deterioration of the transformer progresses, the tightening force is weakened, and the vibration component of a frequency different from the excitation frequency is increased. Therefore, it is assumed that the insulator used in the winding part is deteriorated by catching that the vibration amplitude of the other vibration component becomes larger than the double vibration amplitude (about 100 Hz for the power supply frequency of 50 Hz). It can be diagnosed.
In this case, the other natural vibrations are considered to be distorted and to have a fixed phase delay due to the transmitted excitation force. Therefore, by analyzing in a pair with the phase information, it is possible to remove background noise whose phase is not constant and to grasp an increase in the amplitude of another vibration component limited to the vibration generated by the supplied current.
Of the vibration spectrum detected from the transformer in operation, the amplitude of the other vibration component in the audible sound area is larger than the magnitude of the frequency component of the excitation force by the energizing current, and it is in operation Analyzing the state of the transformer is a method of diagnosing abnormalities and deterioration inside the transformer as described above.

  A method of diagnosing abnormalities and deterioration inside the transformer only by measuring noise during transformer operation without supplying a special current for diagnosis has already been proposed. Patent Document 3 discloses a method of detecting a sound pressure of a machine and diagnosing a machine abnormality by comparing it with a preset reference spectrum. Further, according to Patent Document 4, when an abnormality occurs such as loosening a bolt tightening an iron core or a winding in a transformer, for example, the sound emitted by the device changes, and the sound pressure level of each frequency component changes from the normal time range It is described that it deviates greatly. These diagnostic methods are methods of comparing an acoustic pattern at the normal time and an acoustic pattern at the abnormal time to diagnose that an abnormality or deterioration occurs when the difference is large, and is an analysis method completely different from the modal analysis.

  As described in Patent Document 4, the upper and lower sound pressure level threshold values are set as a method of comparing the normal and abnormal sound patterns, and diagnosis is made based on the proportion of data exceeding that range. In this case, background noise may be superimposed to cause an erroneous determination, and there is a need to increase the width between the upper threshold and the lower threshold.

In the case of the present embodiment, since the phase of the excitation force due to the supplied current is used as a reference, background noise unrelated to the supplied current can be eliminated to prevent a decrease in diagnostic accuracy. Further, the phase difference φ of the forced vibration can be easily estimated by comparing it with the phase of the energizing power source in comparison with the amplitude information that changes depending on the degree of amplification of the measurement system.
Furthermore, if the phase of the mechanical vibration determined as described above is compared with the vibration phase of the sound transformer to analyze the state of the operating transformer, the phase difference is compared with the initial data of the transformer. If there is a change, it can be diagnosed that some internal abnormality or aging has occurred. However, it is necessary to measure the load current dependency and to examine the balance of iron core vibration and winding vibration in the initial data. Also, it is possible to collect initial data later by using a transformer of the same type.

Non-Patent Document 6 describes a technology for diagnosing abnormality of a transformer by an acoustic method. That is, when partial discharge occurs inside the transformer, the simultaneously generated ultrasonic wave is detected by the AE sensor, which is different from the method of judging the mechanical condition by the experimental modal analysis in mechanical vibration described in the previous paragraph .
Further, Non-Patent Document 6 describes a method of diagnosing a transformer by frequency response analysis (FRA). The frequency response in Non-Patent Document 6 is a method of applying a sine wave voltage and sweeping the frequency to measure a transfer function. The electrical impedance changes when the transformer core or coil is dislocated or the ground is disconnected due to a decrease in clamping force or external force, so that the short circuit impedance or the winding leakage inductance changes. This is a diagnostic method that focuses on, and is different from the above-described method of determining the mechanical condition by the experimental modal analysis in mechanical vibration described above.

Example 1
Laser displacement meter (3 phase, rated capacity 200kVA, rated current 550A, 9 years in operation, Mitsubishi Electric RA-TN type) operating at 50Hz (10% load factor) near the center of the tank wall The output waveform of Keyence Corporation LK-G5000) was measured. The wall of the transformer tank is about 80 cm high, and the area with the least vibration is the center of the tank wall, which is considered to be a node of the tank vibration.
FIG. 4 shows an example of the output waveform of the laser displacement meter. The waveform shown in FIG. 4 is a waveform in which a waveform of a frequency of 100 Hz which is twice the power supply frequency is superimposed on a basic waveform of about 10 Hz.
An example of a waveform obtained by Fourier-transforming the waveform shown in FIG. 4 is shown in FIG. In FIG. 5, the large peak waveform appearing in the portion of about 10 Hz was judged as noise due to the wind impact on the transformer and was eliminated in the following analysis.
The power supply frequency of the transformer is 50 Hz and has a peak at a frequency that is an integral multiple of that. The 100 Hz component which is twice the power supply frequency is the basis of the excitation force, and the component which is an integral multiple of 100 Hz is a forced vibration by the power supply system. Although a large vibration of about 10 Hz is also seen in FIG. 5, this vibration is excluded from the analysis in the future because it is a forced vibration due to wind or the like at the time of measurement other than the power supply system.

  Next, a waveform obtained by extracting the second harmonic (100 Hz component) of the power supply frequency from the laser displacement meter output waveform of FIG. 4 using a lock-in amplifier is shown in FIG. The amplitude is normalized to one. This transformer vibration includes core vibration in addition to winding vibration. The loading factor at the time of measurement was about 10%.

  Next, FIG. 7 shows a phase difference between a waveform (dotted line) obtained by squaring the power supply current waveform and the amplitude of the 100 Hz component normalized to ± 1, and a transformer vibration (solid line). The phase difference value can also be determined using a two phase lock in amplifier. If there is a change in the phase difference as compared to the initial data in which the load factor is 10%, it can be diagnosed that some internal abnormality or aging has occurred.

(Example 2)
Output waveform of AE sensor near the tank wall center of oil filled transformer (3 phase, rated capacity 12MVA, primary side 11kV, secondary voltage 3.45kV, 33 years of operation) operating at 50Hz (load factor 60%) FIG. 9 shows the result of Fourier transform of X.sup.2 with the horizontal axis representing frequency and the vertical axis representing amplitude on a linear scale. A peak appears that is an integral multiple of the power supply frequency.
As the deterioration of the transformer progresses, the ratio of high frequency components increases. Therefore, in the vibration spectrum of the tank of the transformer, the amplitude of the high order vibration component in the audible band is the frequency of the excitation force by the energizing current ( If an increase in the magnitude of the component of twice the power supply frequency is detected, internal abnormality diagnosis and deterioration diagnosis of the transformer can be performed.

FIG. 10 shows the result of re-displaying the measured waveform shown in the graph of FIG. 9 as a logarithmic scale on the vertical axis. Also, the measurement position of the tank side wall by the AE sensor was lowered by about 65 cm from the center position of the tank side wall (height 260 cm), and the result is shown in FIG. It is shown in FIG.
As shown in FIG. 10, the peak of the alternate long and short dash line shows the peak due to the vibration of the iron core, the peak of the dashed line shows the peak due to the tank vibration and the peak of the alternate long and two short dashed line shows the peak due to the winding vibration. In the measurement results, it is unclear which part of the vibration mode it is.
When the power supply frequency is 50 Hz, as shown in FIG. 10, a peak appears at a frequency that is an integral multiple of 50 Hz. The 100 Hz component which is twice the power supply frequency is the basis of the excitation force, and the component which is an integral multiple of 100 Hz is a forced vibration by the power supply system. In FIG. 9 in which the amplitude is plotted on a linear scale, a peak in which only forced oscillation due to the power supply system is noticeable is seen. However, in FIG. 10 in which the amplitude is logarithmically displayed, peaks are also seen in addition to the frequency of integral multiples of 50 Hz, which is considered to be mechanical system vibration.
The vibration of the mechanical system shown in FIG. 10 mainly includes three components of iron core vibration, winding vibration and tank vibration, but it is unclear in which part of the vibration mode it is from the measurement results at this stage.

  For two measurement results (graphs in FIG. 10 and FIG. 11) in which the measurement position was changed at a load factor of 60%, the measured natural vibrations of the mechanical system and the vibration strength thereof are summarized in Table 1 below. In Tables 1 and 2 below,-means that the amplitude could not be observed, and the following is shown by increasing the number of + according to the magnitude of the amplitude.

  The vibration mode in which the vibration intensity is changed by changing the measurement position is considered as tank vibration, and the rest are considered as iron core vibration and winding vibration. From the comparison between the results shown in FIG. 11 and the results shown in FIG. 10, each vibration of 37 Hz, 62 Hz, 99 Hz, 137 Hz, 174 Hz, 268 Hz, 329 Hz, 398 Hz, 478 Hz, 566 Hz is tank vibration and the remaining vibration component is It turns out that it is a vibration about an iron core and a winding.

  For two measurement results (graphs in FIG. 10 and FIG. 12) in which the measurement position is at the center of the tank wall and the load factor is changed, the measured vibration strengths of iron core vibration and winding vibration are shown in Table 2 below.

The vibration mode in which the vibration intensity is changed by changing the load factor is considered to be a winding vibration, and the rest is considered to be an iron core vibration. From the results shown in FIG. 12, it can be seen that 23 Hz, 78 Hz, and 97 Hz indicate the iron core, and 141 Hz and 582 Hz indicate the vibration of the winding.
Although this embodiment is a measurement using a sensor (one-dimensional sensor) that measures vibration in one direction, similar measurement and analysis can be performed when a three-dimensional sensor is used.

The frequency for higher order vibration modes can be estimated by Fourier transforming the vibration waveform. However, higher-order vibration modes are difficult to catch because they have small amplitudes, especially in transformers that are not well developed. Therefore, it is preferable to perform signal processing in synchronization with a power supply phase called a compensation method.
When noise components of a plurality of factors are included in addition to the physical quantity to be processed, this is removed using a measurement system having a main sensitivity to noise components that can not be removed by the differential method. The measurement accuracy can be enhanced by subtracting a fixed amount within the range not exceeding the measured amount from the measured amount and measuring the remaining part by the displacement method or the zero method.

The measurement of frequency, the mixing frequency (beat) method using a mixer 30 as shown in FIG. 13, pull the measurement frequency f from the standard frequency f _s, to measure the frequency f _B of the difference. The frequency f _B is called the intermediate frequency f _IF, the frequency to be amplified decreases, together with the measurement accuracy becomes easy amplification increases to facilitate the measurement of high frequency. The standard frequency used here is called local oscillation frequency f _LO .
When the frequency f _s included in the signal and the local oscillation frequency f _LO are matched, the difference is zero. That is, the method of selecting f _LO so that f _s and f _LO match from the beginning and directly dropping the original signal to the frequency zero which is the base band is called homodyne.
Also, the local transmission frequency f _LO can be selected so that the intermediate frequency f _IF of the sum or difference of the frequency f _s contained in the signal and the local transmission frequency f _LO is constant. Further, signal processing for converting a signal to an intermediate frequency is called heterodyne.

If the frequency f _s contained in the signal can be found by the above method, it is possible to measure the raw waveform of a minute target signal buried in large noise using a lock-in amplifier.
Further, since the standard frequency is variable from mHz to 100 kHz, analysis can also be performed using a method called PLL (phase locked loop: phase locked loop) in which the frequency is swept to find a resonance point.
Furthermore, it is also possible to analyze the phase information of the measurement frequency by adjusting the phase of the standard frequency with a phase shifter.

(Example 3)
Oil-filled transformer (3 phase, rated capacity 10MVA, primary side rated voltage 11kV, secondary side rated voltage 3.45kV, insulating oil amount 5300 liters, operating start at 1975) with rated frequency 60Hz in operation (load factor approx. 10%) Vibration sensors were installed at various positions on the wall of the transformer tank, and the vibration of the transformer tank was measured. As a vibration sensor, a three-axis accelerometer (356A17) manufactured by PCB (Toyo Technica) was used, a clamp ammeter was used for current measurement, and an FFT analyzer (OR38V3-32 manufactured by Oros) was used as a data logger.

The outline of the transformer tank is shown in FIG. However, the bushing and wiring for inputting and outputting electric power to and from the transformer are omitted in FIG.
The transformer tank 31 is a rectangular parallelepiped hollow container made of steel plate having a width of 2200 mm, a height of 2000 mm, and a depth of 800 mm, and metal waist wraps at two upper and lower positions dividing the height into about three. Reinforcing stays 32, 33 are provided.
A portion above the reinforcement stay 32 in the peripheral wall of the transformer tank 31 is constituted by the upper peripheral wall 31a, and a portion below the reinforcement stay 32 in the peripheral wall of the transformer tank 31 is constituted by the middle peripheral wall 31b The lower part of the reinforcement stay 33 is composed of the lower peripheral wall 31c.
Since the portions of the reinforcement stays 32 and 33 in the transformer 31 are at positions where the vibration is limited, the following eighteen positions are set as candidates for measuring the vibration by attaching a vibration sensor.

  In this transformer tank 31, vibration sensors can be attached to the positions surrounding the numbers 1 to 16 in FIG. The position of number 1 enclosed by ○ indicates the left side wall surface of upper peripheral wall 31a, and the position of number 2 enclosed by circle 相当 corresponds to the left end side of the front wall of upper peripheral wall 31a (approximately 40 cm from the left end of the front wall The position of the numeral 3 surrounded by ○ indicates the position corresponding to the right end side of the front wall of the upper peripheral wall 31a (around 40 cm from the right end of the front wall). The position of number 4 enclosed by ○ indicates the right side wall of upper peripheral wall 31a, and the position of number 5 enclosed by ○ corresponds to the right end of the back wall of upper peripheral wall 31a (about 40 cm from the right end of the back wall) The position of number 6 surrounded by ○ indicates the position corresponding to the left end side of the back wall of the upper peripheral wall 31a (around 40 cm from the left end of the back wall).

As illustrated here, the position where the vibration sensor is attached is at the positions 7, 8, 9 and 10 of the numbers surrounded by circles in the middle peripheral wall 31b below the reinforcement stay 32 and the lower peripheral wall 31c below the reinforcement stay 33. It may be any position of numbers 13, 14, 15, 16 enclosed by o marks. The mounting position on the back wall side of the middle peripheral wall 31b and the mounting position on the rear wall side of the lower peripheral wall 31c are omitted because they can not be illustrated in FIG. 14, but they correspond to the mounting positions surrounding the numbers 5 and 6 with ○ marks. The back wall side of the middle peripheral wall 31 b and the back wall side of the lower peripheral wall 31 c are respectively set.
At these vibration sensor mounting candidate positions, in the following tests, vibration sensors were installed on the upper right side wall corresponding to the positions surrounding the number 4 with circle marks to measure the vibration.

In the inside of the transformer tested in this example, as shown in FIG. 15, an iron core 38 of a well girder structure in which three legs 35 are connected by upper and lower yokes 36 and 37 is accommodated. The description of the primary side winding and the secondary side winding wound around the leg 35 in FIG. 15 is omitted.
In this iron core 38, it is assumed that three vibration modes, that is, the torsion mode shown in FIG. 15 (A) and the bending mode 1 shown in FIG. 15 (B) and the bending mode 2 shown in FIG. Can. The modal analysis shown in FIG. 15 is based on “natural vibration characteristics of transformer iron core” (2013, National Institute of Electrical and Electronics Engineers 5-195) according to Sueyoshi Mizuno et al.
In the case of the torsion mode transformer shown in FIG. 15 (A), by disposing a vibration sensor at a position surrounding circled numbers 2, 3, 5 and 6 shown in FIG. It is believed that In that case, the numbers 2 and 3 are in the opposite direction, the numbers 5 and 6 are in the opposite direction, the numbers 2 and 6 are in the same direction, and the numbers 3 and 5 are in the same direction. If displacement can be confirmed, it can be understood that the iron core vibrates in the torsion mode. Similarly, as shown in FIG. 15 (B), if the vibration sensor is installed at the positions 8, 9, 11 and 12 of the numerals and the displacement is confirmed, it can be understood that vibration is performed in mode 1. Similarly, as shown in FIG. 15C, if the vibration sensor is installed at the positions 7 and 10 of the numerals and the displacement is confirmed, it can be understood that vibration is performed in mode 2.
If the vibration mode can be identified to the natural frequency of the iron core, the tightening force of the iron core can be calculated from the natural frequency. However, if there is a variation in the tightening force of the iron core, the natural vibration peak will spread. Conversely, it is also possible to evaluate the spread of the natural frequency, for example, the variation in tightening force from the half width. The same evaluation is possible when the natural vibration peak of the winding has a spread. Although the broadening of the peak width is related to the deterioration of the iron core or the winding, it is necessary to determine for each transformer how much the peak width becomes the threshold of the deterioration diagnosis, because it depends on the design of each transformer.

In this example, in the right side wall of the upper peripheral wall of the transformer tank, as shown in FIG. 16, the right side wall right and left direction is divided as 1A, 2A,... 15A, and the right side wall vertical direction is 1A, 1B,. As shown in the figure, an impact test was conducted in which the vibration sensor was placed at a position of, for example, 3C, and the position of 4C on the right side was hit with a hammer to apply vibration.
Alternatively, a vibration sensor may be installed at the position of 13F and a test of striking the position of 13E with a hammer may be performed. The position where the vibration sensor is attached and the position where the hammer is hit may be any position as long as the vibration of the transformer tank can be picked up well, and is not limited to the position shown in FIG.

The vibration of the transformer tank in operation is measured while the vibration sensor is installed at the 3C position, and the result of Fourier transform of the measurement result is shown in the lower side of FIG. 17 as a waveform (waveform at the time of operation).
The waveform of the result of the Fourier transform of the vibration measurement result obtained when the impact test was performed by striking the position of 4C with a hammer while the transformer was in operation while the vibration sensor was installed at the position of 3C It shows by (waveform at the time of excitation).

  In the waveform showing the vibration measurement result during operation, a large peak is seen at an integer multiple of 60 Hz (120, 180, 240, 300, 360, 420 Hz), and a plurality of weak peaks are also seen. In the vibration measurement result at the time of excitation, some peaks are seen at frequency positions (142, 217, 334 Hz, etc.) indicated by vertical dotted lines (black dashed lines) other than integral multiples of 60 Hz. Of the peaks at the time of actual operation, those having overlapping peaks at the time of excitation are considered to be natural vibration components of the tank wall surface. However, whether the peak at the time of vibration is the natural vibration component of the tank wall is confirmed by checking the change of the phase component to be measured at the same time, and changing the installation position of the sensor and the hitting point. It is preferable to do.

It is preferable to change the load factor to identify a peak whose intensity changes, as described in paragraph 0079 above. Of the transformer vibrations, when the tank vibrations and the winding vibrations are separated as described above, the remainder is considered as iron core vibrations.
However, the area around the operating transformer is an environment where electromagnetic noise is large. It is conceivable that electromagnetic noise may affect a vibration sensor, an amplifier, an analyzer, a cable connecting them, and a driving power source of a measuring instrument. There is also a possibility that the building at the transformer installation site and the ground are shaking. It is also important to improve the accuracy of diagnosis by devising to eliminate or reduce the influence of the noise.

It is desirable to conduct the above-described test using a device such as a device susceptible to electromagnetic noise covered with metal foil, a sufficient grounding of the device can, and a device driven by a battery.
Also, if it is possible to simultaneously measure the vibration of the building or ground where the test is to be performed or if it is possible to regularly repair the transformer, measure and confirm background noise in advance at that opportunity to check the vibration of the transformer. It is desirable to perform processing such as subtraction from.

  A: Diagnostic device 1: Transformer 2: Tank 3: coil body 5: iron core 8: fastening bracket 9: outer coil (primary coil) 10: inner coil (secondary coil) 11: Outer winding (primary winding), 12 ... insulation spacer, 16 ... inner winding (secondary winding), 22 ... vibration detector (vibration sensor), 23 ... voltmeter, 24, 25 ... amplifier, 26 ... Analyzer, 27 ... arithmetic unit.

Claims (6)

A transformer comprising an iron core, a coil body, windings constituting the coil body, and a tank containing the coils,
With regard to transformer vibration in the operating state, using the vibration detector having detection sensitivity in the low frequency region to the audible sound region (1 Hz to 20 kHz), using the means by signal processing using an electronic circuit or software The smallest area of the tank surface vibration of the operating transformer due to the electromagnetic force generated by the energizing current applied to the transformer at a predetermined load factor as the node of the vibration, said vibration detector at the position of said node And the peak of the result drawn on a graph in which the result is set to the vibration intensity on the vertical axis and the frequency on the horizontal axis.
The output waveform measured at a position deviated from the position of the node on the tank surface of the operating transformer at the predetermined load factor by the vibration detector is subjected to Fourier transform, and the result is the vertical axis vibration intensity and horizontal axis frequency Compare with the peak of the result drawn on the set graph,
By changing the measurement position from the position of the node, the vibration of the frequency at which the vibration intensity indicated by the peak changes is grasped as the vibration of the tank, and the remaining vibration is grasped as iron core vibration or winding vibration.
Regarding the remaining iron core vibration or winding vibration, the measurement position of the vibration detector is set to the position of the node of vibration of the tank surface, and the load factor is obtained by changing the load factor from the predetermined load factor. Based on the peak comparison of the above, it is judged that the vibration of the frequency at which the vibration intensity does not change is the core vibration, and the vibration of the frequency at which the vibration intensity has become weak is the winding vibration,
Internal anomalies and deterioration when there is a change in either or both of the core vibration and the winding vibration as compared to one or both of the iron core vibration and the winding vibration obtained by the same method as the above method for a sound transformer A method of diagnosing internal abnormality and deterioration of a transformer characterized by determining that The transformer according to claim 1, wherein one or both of the iron core vibration and the winding vibration determined in claim 1 are captured by changing over time to determine the state of the transformer in operation . How to diagnose internal anomalies and deterioration. A transformer having an iron core, a coil body, windings constituting the coil body, and a tank containing the coils, wherein an electronic circuit or software is used for a transformer vibration in an operating state using a vibration detector. The smallest area of the tank surface vibration of the operating transformer due to the electromagnetic force generated by the energizing current applied to the operating transformer at a predetermined load factor using means by signal processing Measuring the output waveform of the vibration detector at the position of the node, extracting an integer multiple of the transformer power supply frequency from the output waveform, and standardizing the amplitude of the integer multiple, and a waveform of the transformer Determine the phase difference between both waveforms by comparing the normalized waveform of the same frequency with the integer multiple wave from the power supply current waveform, and if there is a phase difference and change measured with a sound transformer, an internal error And degradation Transformer internal fault and diagnostic methods deterioration is characterized by judging that. The method according to claim 3, wherein the state of the operating transformer is determined by capturing changes in the phase difference with time . It is a diagnostic device for internal abnormality and deterioration of a transformer applied to a transformer having an iron core, a coil body, a winding constituting the coil body, and a tank accommodating these,
A vibration detector mounted on an operating transformer and having detection sensitivity to vibrations from the low frequency range generated by the transformer to an audible sound range (1 Hz to 20 kHz), and a detection signal from the vibration detector And an analyzer for obtaining mechanical vibration associated with the excitation force due to the energizing current to the transformer in operation, and an operation means for operating data obtained from the analyzer.
The computing means
Tank surface vibration of the operating transformer due to the electromagnetic force generated by the energizing current applied to the operating transformer at a predetermined load factor by means of signal processing using electronic circuits or software The output waveform obtained from the vibration detector at the position of the node with the smallest region of vibration as the node of the vibration Fourier-transformed, and the result is the peak of the result drawn in the graph set to the vertical axis vibration intensity and horizontal axis frequency ,
The output waveform measured at a position deviated from the position of the node of vibration on the tank surface of the transformer operating at the predetermined load factor is subjected to Fourier transform, and the result is set to the vertical axis vibration intensity and horizontal axis frequency. Compare with the peak of the drawn result,
By changing the measurement position to the position of the node and the position away from it, the vibration of the frequency at which the vibration intensity indicated by the peak changes is grasped as the vibration of the tank, and the remaining vibration is grasped as iron core vibration or winding vibration. And
Regarding the remaining iron core vibration or winding vibration, the measurement position of the vibration detector is set to the position of the node of vibration of the tank surface, and the load factor is obtained by changing the load factor from the predetermined load factor. Based on the peak comparison of the above, the vibration in which the vibration strength does not change is judged as iron core vibration, and the vibration in which the vibration strength is weakened is judged as winding vibration,
Internal anomalies and deterioration when there is a change in one or both of the core vibration and the winding vibration as compared to one or both of the iron core vibration and the winding vibration obtained by the equivalent method for a sound transformer. A diagnostic device for internal abnormality and deterioration of a transformer characterized by having a function of determining that the computing means has occurred . It is a diagnostic device for internal abnormality and deterioration of a transformer applied to a transformer having an iron core, a coil body, a winding constituting the coil body, and a tank accommodating these,
A vibration detector attached to the operating transformer; an analyzer for obtaining mechanical vibration associated with the excitation force by the supplied current to the operating transformer in response to a detection signal from the vibration detector; Computing means for computing data obtained from the
With regard to the transformer vibration in the operating state, it is generated by the energizing current applied to the transformer in the operating state at a predetermined load factor using the vibration detector and means by signal processing using an electronic circuit or software. Measure the output waveform of the vibration detector at the position of the node with the smallest area of the tank surface vibration of the operating transformer due to the electromagnetic force, and from this output waveform, an integer of the transformer power frequency The phase difference between the two waveforms by comparing the waveform obtained by extracting the double wave and standardizing the amplitude of the integer multiple wave and the waveform obtained by normalizing the amplitude of the same frequency as the integer multiple wave from the power supply current waveform of the transformer Of the internal abnormality and deterioration of the transformer characterized in that the calculation means has a function of determining the internal abnormality and deterioration when there is a phase difference and change measured by the sound transformer. Medical examination Apparatus.

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