KR101358038B1 - Method for analysis on characteristics of winding in cast resin transformer - Google Patents

Abstract

The present invention relates to an apparatus for analyzing the characteristic of a winding in a cast resin transformer. Particularly, the present invention relates to a method for analyzing the characteristic of a winding in a cast resin transformer. According to the present invention, the method for analyzing the characteristic of a winding in a cast resin transformer includes (a) a step of supplying power to a cast resin transformer; (b) a step of generating a circulating current by supplying a copper loss according to the load current of the secondary side of the cast resin transformer; (c) a step of measuring the vibration signal of the outer wall of the high pressure side of the cast resin transformer generated according to the load current in a voltage applied to the cast resin transformer; and (d) a step of outputting each component of a vibration harmonic wave according to the change of vibration due to a winding according to the change of load current by analyzing the vibration frequency of the vibration signal. [Reference numerals] (110) Induction voltage regulator; (120) Mold transformer; (140) Vibration measurement device; (150) Vibration frequency analyzer; (160) Voltage and frequency regulator

Description

Method for analysis on characteristics of winding in cast resin transformer

The present invention relates to a vibration analysis method of a mold transformer, and more particularly, to a winding vibration characteristic analysis method of a mold transformer.

Conventionally, Korean Patent Application Publication No. 1998-0001213, 'Preventive diagnosis method and apparatus for a mold transformer using vibration signal analysis method', has been filed and disclosed in a number of applications.

[0003] In the preventive diagnosing apparatus of a mold transformer using vibration signal analysis, the related art includes a temperature measuring means for measuring the surface temperature and the ambient temperature of a mold transformer, a high voltage side voltage of the mold transformer, a load side and a supply current, respectively. A vibration signal collecting means comprising a voltage / current transformer for measuring the voltage, a high voltage winding of the mold transformer, and an acceleration sensor for measuring iron core vibration signals, and a power supply unit for amplifying a weak signal from the acceleration sensor. A signal converter converting the AC signal from the temperature measuring means, the voltage / current converting means and the power supply unit into a direct current signal, and an analog / digital signal conversion for converting the analog output signal of the signal converter into a digital signal; A vibration signal converting means comprising a negative portion and a digital signal from the vibration signal converting means By comprising a vibration signal analysis means for is characterized in that is made.

The transformer is an important element of power supply, and it is necessary to accurately understand the state of the transformer and prevent the power supply failure due to deterioration.

A mold transformer is a transformer in which iron cores and coils are not impregnated in insulating oil, and the entire surface of the winding is cast and solidified by synthetic resin such as epoxy.

It has excellent characteristics in electrical insulation and mechanical properties as well as flame retardancy and moisture resistance, and has been used for indoor water substation facilities requiring fire safety. Widely used in 22.9kV class transformers such as consumer.

If the life of the transformer is estimated to be 30 years, the mold transformer, which has been operating since the 1980s, is nearing the end of its life.

However, mold transformers are only inspected by visual inspection and maintenance methods are used to clean foreign substances such as dust, and mold transformers that are close to their life due to the lack of diagnostic methods for mold transformers to prevent malfunctions or accidents are not implemented. Or, there are not many diagnostic methods for mold transformers to prevent accidents, and thus, there is a risk of failure or accident of a mold transformer near its lifetime.

The iron core and the winding of the mold transformer may loosen the pressure of the clamp which fixes the iron core by impact during installation and movement of the transformer, and may cause mechanical deformation. In addition, insulation performance is deteriorated by repeated thermal shocks and deterioration of insulation, and insulation breakdown is caused by abnormal voltage such as switching surge, which may lead to transformer accident. This degradation causes partial discharge inside the transformer, which eventually leads to an accident such as a fire in the transformer.

Therefore, it is important to check the iron core of the transformer and the sound state of the windings from time to time. To do this, it is necessary to analyze the vibration characteristics of the iron core and the winding of the mold transformer in the sound state.

An object of the present invention has been made in view of the above point, to provide a method for analyzing the vibration characteristics of the mold transformer for analyzing the vibration characteristics generated by the iron core and the winding of the transformer and the correlation of the vibration magnitude according to the cause. Is in.

The present invention relates to a winding vibration analysis method of a mold transformer, the method comprising: (a) supplying power to a mold transformer; (b) supplying copper loss according to the load current to the secondary side of the mold transformer to generate a circulating current; (c) measuring a vibration signal of the outer wall of the mold transformer high pressure side generated according to the load current at the voltage applied to the mold transformer; And (d) analyzing the vibration frequency of the vibration signal and outputting the vibration magnitude change by the winding according to the load current magnitude change for each vibration harmonic component.

Preferably, step (a) is characterized in that the voltage applied to the mold transformer is applied at 80%, 90% or 100% of the rated voltage using the induction voltage regulator IVR.

And preferably, the step (c) is characterized in that for measuring the vibration signal of the outer wall of the mold transformer high pressure side generated by the load current at the voltage applied to the mold transformer using a laser.

As described above, according to the present invention, it is possible to analyze the vibration characteristics generated by the iron core and the winding of the transformer and to analyze the correlation of the vibration magnitude according to the cause.

1 is a configuration of the winding vibration analysis device of a mold transformer according to an embodiment of the present invention,
Figure 2 is an exemplary configuration of the vibration analysis device of the mold transformer according to an embodiment of the present invention,
3 to 7 are graphs showing the results of the frequency analysis of the iron core vibration of the vibration analysis device of the mold transformer according to an embodiment of the present invention,
8 is a graph showing the relationship between the applied voltage and the iron core vibration of the vibration analysis device of the mold transformer according to an embodiment of the present invention,
9 to 11 are graphs showing a load current and a vibration relationship according to winding vibrations according to an embodiment of the present invention.
12 is a flowchart illustrating a winding vibration analysis method of a mold transformer according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to exemplary drawings attached hereto.

1 is a configuration diagram of a vibration analysis device for winding of a mold transformer according to an embodiment of the present invention, Figure 2 is an overall configuration diagram of a vibration analysis device of a mold transformer according to an embodiment of the present invention, Figures 3 to Figure 7 is a graph showing the results of the iron core frequency analysis results of the vibration analysis device of the mold transformer according to an embodiment of the present invention, Figure 8 is the applied voltage and iron core vibration of the vibration analysis device of the mold transformer according to an embodiment of the present invention 9 to 11 are graphs showing a load current and a vibration relationship according to winding vibrations according to an embodiment of the present invention, and FIG. 12 is a winding vibration of a mold transformer according to an embodiment of the present invention. A flowchart of the analysis method.

As shown in Figure 1, the winding vibration analysis device of the mold transformer according to the present invention is an induction voltage regulator 110, mold transformer 120, vibration measuring instrument 140, vibration frequency analyzer 150, voltage frequency regulator ( 160).

Induction voltage regulator (IVR) 110 is a configuration for supplying power to the mold transformer 120.

Induction voltage regulator (IVR) of the present embodiment was set to one single-phase 30kVA (input: 220V, output: 0 ~ 300V) induction voltage regulator (IVR) for the transformer power supply. This induction regulator applies 80% or 90% or 100% of the rated voltage to the mold transformer.

For reference, the switch 130 shown in FIG. 2 is configured to block the load current by opening the secondary terminal of the mold transformer 120 to test the vibration characteristics by the iron core, so that the load current does not flow.

The voltage frequency regulator 160 is configured to supply a copper loss according to the load current to the secondary side of the mold transformer to generate a circulating current.

The vibration measuring unit 140 measures the vibration signal of the outer wall of the high pressure side of the mold transformer generated according to the load current at the voltage applied to the mold transformer. The vibration measuring device is characterized in that the non-contact vibration measuring device for measuring the vibration of the outer wall of the high pressure side generated in the mold transformer using a laser.

Although the vibration measuring device according to the present embodiment is set as a non-contact vibration measuring device, the present invention is not limited thereto.

Vibration frequency analyzer 150 is a configuration for frequency analysis of the vibration signal of the vibration measuring instrument. The vibration frequency analyzer analyzes the vibration frequency of the vibration signal and outputs the vibration magnitude change by the winding harmonic component according to the load current magnitude change.

In the present invention, the vibration of the mold transformer was measured according to the applied voltage and the load amount variation using a non-contact vibration measuring apparatus using a laser.

Referring to the vibration analysis device of the mold transformer according to an embodiment of the present invention in more detail.

The causes of vibration generated in the transformer can be divided into two categories. One is the iron core vibration, and the excitation caused by magnetization and excitation occurs in the gap, and the other is the vibration of the winding due to the electromagnetic force generated by the interaction of the leakage magnetic flux and the winding current.

When alternating current of constant frequency is applied to the transformer, a magnetic field is formed in the core of the transformer, and vibration occurs as the magnetic field changes.

The cause of vibration is due to magnetostriction, which is caused by mechanical deformation caused by the magnetic field, and the magnitude of the magnetic field is maximized twice during one alternating cycle. Therefore, vibration caused by magnetostriction occurs at twice the frequency of the alternating frequency.

The alternating magnetic field induced by the transformer core causes the silicon steel plate of the core to vibrate and is transmitted to the transformer outer wall through the support and the insulator of the core.

In the case of the transformer, the electric frequency generated by the magnetostriction of the inner iron core is discharged to the outside through the transformer outer wall by multiple combinations of 120 kHz.

The winding arrangement of the mold transformer mainly adopts the method of arranging the low voltage winding near the iron core and the high voltage winding on the bar side of the low pressure winding to maximize the insulation performance and reduce the cost.

When current flows through a conductor, a magnetic field is formed around the conductor, and when another conductor is placed near the current-carrying conductor, the magnetic field around these two conductors is the vector sum of the magnetic fields.

When two currents flow in opposite directions, the magnetic flux density increases in the space between the conductors, and a repulsive force occurs between the two conductors according to Lorentz's law. This causes the two conductors to move away.

In addition, when two currents flow in the same direction, the magnetic flux density increases in the outer space of the conductor and suction force is applied between the coil layers.

The electromagnetic force generated in the winding of the transformer can be calculated as the force in the axial direction and the radial direction.

The axial electromagnetic force generated by the leakage magnetic flux is generated by the outer winding outward and the inner winding inward.

In the transformer, the current density and leakage flux can be expressed as a linear function of the load current attributable to the time function, and the force acting on the winding becomes a function proportional to the square of the load current.

That is, the force acting on the winding has an alternating current component having a frequency of twice the direct current component and the load current frequency. Therefore, like the iron core vibration, the 120 kHz frequency component having a multiple of 60 kHz to the fundamental frequency acts as the fundamental frequency.

In the embodiment of the present invention may be configured as shown in Figure 2 to measure the vibration during operation of the mold transformer.

Test Mold Transformer Single Phase 30kVA (22,900 / 220V) Two (121,122) (Mold TR1, Mold TR2) and Single Phase 30kVA (Input: 220V, Output: 0 ~ 300V) for Power Supply of Induction Voltage Regulator 110 (IVR) 1 unit, single-phase 30 kVA for copper loss supply (input: 220 V, output: 0 to 10 V) 1 voltage frequency regulator 160 (VVVF), dry transformer 170 (TRc) single phase 30 kVA (input: 10 V, output: 0 1,500 V).

In the transformer load test, the actual load test is difficult to perform in terms of cost and control. Therefore, only iron loss and copper loss are supplied separately to the transformer to have the same effect as the actual load test.

In other words, when two transformers of the same rating are connected to the same power supply, the transformers can be tested because the two transformers are loaded with each other.

When the low voltage windings are connected in parallel and the high voltage windings of the two transformers are connected to each other with the same polarity, the induced voltages are the same in opposite directions and the reverse direction does not flow in the high voltage windings.

Low voltage windings receive a magnetizing current from the power supply, which corresponds to iron losses in both transformers. This equilibrium is broken by supplying an alternating current supply voltage through another transformer to the high-voltage circuit.

The variation of the supplied AC power supply voltage changes the circulating current flowing in the high voltage winding, causing a current proportional to that in the low voltage winding.

In this way, only the losses consumed in the two transformers are supplied from the outside so that the actual load can be simulated by the same condition as the actual load.

In this embodiment, a non-contact vibration measuring apparatus using a laser for measuring the vibration of the mold transformer is a non-contact vibration speedometer (LV110D, EM4SYS Co., Ltd.) having a Velocity output sensitivity of 15 mm / s / v, measuring range 0.1 ~ 40 Was used.

[Table 1]

As a result of measuring the vibration of the transformer, in order to identify the characteristics of the iron core vibration and the winding vibration which generate the vibration in the transformer, when testing the vibration characteristics by the iron core, open the secondary terminal of the transformer so that the load current does not flow. An open test was conducted.

As shown in Figures 3 to 7, the applied voltage was applied to 80%, 90%, 100%, 110%, 120% of the rated voltage while frequency analysis of the vibration signal at that time to determine the respective characteristics .

Also, in order to grasp the vibration characteristics when the current of the transformer flows, the short circuit test method was used to measure and analyze the vibration characteristics caused by the winding of the transformer according to the change of the current.

In order to measure only the vibration caused by the iron core, a transformer opening test was conducted to prevent the voltage from being applied to TRc so that vibration by the winding did not occur.

The applied voltage was applied 80%, 90%, 100%, 110%, 120% of the rated voltage using the induction voltage regulator (IVR), and the vibration frequency was measured by measuring the vibration of the outer wall generated at the high voltage side. Fourier Transform) analysis was performed.

The magnitude of the vibration by the iron core increases in proportion to the applied voltage, and it can be seen that the vibration is transmitted to the outer wall through the epoxy as a solid insulator.

The measured vibration frequencies were 120Hz, 240Hz, 360Hz, and 480Hz, and they were measured as multiple harmonics of 120Hz.

The oscillating harmonic component is reduced to near zero as the frequency approaches 1 kHz.

Assuming that 120 kHz is the fundamental frequency, it can be seen that at the frequency of 480 kHz, which is equivalent to 4 harmonics, the magnitude increases nonlinearly based on the harmonic components of the preceding order.

This is because the resonance occurs in the 480 ㎐ band of the natural vibration frequency of the test transformer.

It can be seen that the magnitude of the harmonic component increases almost linearly with increasing applied voltage.

As shown in Figure 8, the relationship between the iron core vibration according to the applied voltage is shown for each vibration harmonics (120 Hz, 240 Hz, 360 Hz, 480 Hz) through the vibration frequency analysis.

In order to measure the vibration caused by the winding, 80%, 90%, 100% rated voltage is applied to the inductive voltage regulator (IVR), and the experiment is conducted by generating a circulating current on the secondary side using the vibration frequency analyzer (VVVF). FFT analysis was performed on the vibration frequency by measuring the vibration of the outer wall generated at the high pressure side.

9 is a result of measuring the vibration of the transformer transmitted through the outer wall of the high voltage when the load current of 16.0%, 40.4%, 47.8%, 60.0%, 77.2% at 80% rated voltage.

The vibration measured through the outer wall of the high voltage side has harmonic vibrations of 240 Hz, 360 Hz and 480 Hz based on 120 Hz, and its magnitude decreases as the harmonic order increases.

However, it can be seen that the size increases at 480 처럼 as in the vibration measurement by iron core. Since this is the same test transformer used in the vibration measurement of the iron core, it is judged that the magnitude of the resonance is increased because the natural vibration frequency component of the transformer is the same.

As the load current increases at 80% of the rated voltage, the electromagnetic force due to leakage flux and winding current increases, indicating that the vibration of the winding increases.

As a result of the test, as the load current increases, the increase of the vibration value increases, but above that, the increase of the vibration value becomes slow.

As the load current increases, the winding vibration of the transformer increases, and the harmonic vibration component generated during the iron core vibration is relatively small.

The basic oscillation frequency component of 120 kHz can show the correlation function relationship with the load current magnitude change and the magnitude of vibration as a regression line as shown in Equation (1), and the correlation coefficient is 0.929.

A correlation coefficient of 1 indicates that all measurement points are in full agreement with the trend line. In the formula (1), when x = 0, that is, when the current value is 0, the magnitude of the vibration velocity is 18.16 μm / s. This result is almost the same as 18.3㎛ / s of 120㎐ in iron core vibration test result.

[Equation 1]

y = 23.81x + 18.16

FIG. 10 shows that the vibration change according to the load current at 90% rated voltage only increases the relative magnitude of the vibration frequency, and shows similar characteristics to the vibration change according to the load current at 80% rated voltage.

It can be seen that up to 70% of the load current increases the magnitude of 120㎐ and 480㎐, but as the load current increases, the magnetostrictive vibration by the iron core is relatively decreased due to the winding vibration caused by the linear load, resulting in a constant transformer vibration. have. If the vibration frequency component of 120 has a correlation function relationship as shown in Equation (2), the magnitude of load current and the magnitude of vibration have a correlation coefficient of 0.756. In Equation (2), when x = 0, that is, when the current value is 0, the magnitude of the vibration velocity is 31.11 μm / s. This result is almost the same as 28.2㎛ / s of 120㎐ in the iron core vibration test result.

&Quot; (2) "

y = 27.91x + 31.11

As shown in FIG. 11, the vibration according to the load current at 100% rated voltage shows almost similar characteristics to the previous test.

Since the test transformer is designed and manufactured under the design conditions under the operating conditions at 100% of the rated voltage, it is judged that the harmonic vibration of 480 ㎐ is relatively small at the rated voltage. The vibration of the 120Hz and 480Hz frequency components shows almost no change in the magnitude of the vibration of the 240Hz and 360Hz components as the load rate decreases to 100%.

In addition, unlike the previous experiment, it can be seen that the vibration magnitude of the 480㎐ component is small. If the oscillation frequency component of 120 kHz has the correlation function relationship as the variation of load current and the magnitude of vibration, the correlation coefficient is 0.761.

In equation (3), when x = 0, that is, when the current value is 0, the magnitude of the vibration velocity is 44.51 µm / s. This result is almost the same as 41.1㎛ / s of 120㎐ in iron core vibration test result.

&Quot; (3) "

y = 22.3x + 44.51

The vibration characteristics of the transformer can be understood only by removing the influence of magnetostrictive vibration by the iron core and measuring the vibration value purely by the electromagnetic force of the winding. However, it is impossible to exclude the vibration effect of the transformer core from the entire vibration because it operates only when the voltage is applied to the primary side to excite the transformer core.

However, if you analyze the experimental results, you can know the basic vibration value of the transformer by iron core without testing the transformer by checking the correlation between the load current and the transformer vibration by making the voltage on the primary side constant and changing the load current. .

Using this principle, it is possible to infer the basic vibration value by the iron core without the open test only by short-circuit test of the transformer, and it is possible to separate the transformer vibration value and the winding vibration value by the iron core at a constant voltage. do.

If there is more than 20% variation in the basic vibration value of a sound transformer core, a serious problem is likely to occur in the core of the transformer.

Using the present invention, if structural deformation occurs in the transformer core and causes a potential accident, it is determined that such structural deformation of the iron core can be found. Conversely, if there is no problem with the core of the transformer and the voltage applied to the transformer is constant and the variation of the increase due to the load current is very severe, it may be determined that a potential accident cause has occurred in the transformer winding.

In order to measure the vibration of the mold transformer using a non-contact vibration measuring device using a laser and to analyze the vibration signal in the frequency domain, the spectrum was obtained by using the FFT method.

Transformer core and winding generate vibration by magnetostriction and electromagnetic force and generate vibration waveform with frequency component based on 120 kHz.

The vibration caused by the iron core increases linearly with the applied voltage, and the vibration caused by the winding increases linearly with the magnitude of the load current, but it is found that it is stabilized above a certain load ratio.

In the present invention, the correlation of the vibration magnitude according to the cause of each vibration in the transformer was analyzed and a method for diagnosing structural deformation of the core and the winding of the mold transformer was proposed.

On the other hand, in the winding vibration analysis method of the mold transformer, as shown in FIG. 12, power is supplied to the mold transformer (S2). Here, the step S2 is characterized in that the voltage applied to the mold transformer using the induced voltage regulator (IVR) as 80%, 90% or 100% of the rated voltage.

Next, by supplying a copper loss according to the load current to the secondary side of the mold transformer to generate a circulating current (S4).

Next, the vibration signal of the outer wall of the high pressure side of the mold transformer generated by the load current at the voltage applied to the mold transformer is measured (S6).

Here, the step S6 is characterized in that for measuring the vibration of the outer wall of the high pressure side generated in the mold transformer according to the load current at the applied voltage using a laser.

And the frequency of the vibration signal is analyzed (S8). In step S8, the vibration frequency of the vibration signal is analyzed to output the magnitude of the vibration by the winding according to the magnitude of the load current.

110: induction voltage regulator 120: mold transformer
140: vibration measuring instrument 150: vibration frequency analyzer
160: voltage frequency regulator 170: dry transformer

Claims (3)

In the winding vibration analysis method of the mold transformer,
(a) supplying power to the mold transformer;
(b) supplying copper loss according to the load current to the secondary side of the mold transformer to generate a circulating current;
(c) measuring a vibration signal of the outer wall of the mold transformer high pressure side generated according to the load current at the voltage applied to the mold transformer; And
(d) analyzing the vibration frequency of the vibration signal and outputting a vibration magnitude change by the winding according to the load current magnitude change for each vibration harmonic component. The method of claim 1,
In the step (a)
Winding vibration analysis method of the mold transformer, characterized in that for applying a voltage applied to the mold transformer using an induction voltage regulator (IVR) at 80%, 90% or 100% of the rated voltage. The method of claim 1,
The step (c)
The vibration analysis method of the winding of the mold transformer, characterized in that for measuring the vibration signal of the outer wall of the mold transformer high pressure side generated by the load current at the voltage applied to the mold transformer using a laser.

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