JP4878903B2 - Magnetic sensor for pillar transformer diagnosis - Google Patents

Description

  The present invention relates to a diagnostic method for a pole transformer.

In the pole transformer, the insulation deterioration inside the winding proceeds due to the intrusion of lightning surge and repeated overload operation. In locations where the insulation degradation is significant, dielectric breakdown occurs, and the circulating current flows due to the potential difference of the induced voltage based on the difference in the number of flux linkages between the adjacent winding conductors where the dielectric breakdown occurred. In addition, the insulation deterioration is accelerated. In general, a lightning arrester is installed on the primary side of the transformer to prevent lightning current from entering, but no lightning arrester is installed on the secondary side. Windings are often damaged.
In the pole transformer, the insulating oil is often replaced and reused, but the winding is not replaced. Thus, windings that have already deteriorated may burn out immediately after being reused, and in order to prevent such accidents, establishment of deterioration diagnosis technology for pole transformers is required. .

The transformer is manufactured to have a closed magnetic circuit as much as possible in order to eliminate loss during voltage conversion.
However, when an abnormal current far exceeding the rated current flows like the lightning current described above, the winding and core are distorted due to excessive electromagnetic force based on the abnormal current, and under such distortion, it is normal. The present inventors have confirmed that the magnetic flux leaks even when the load current is applied.
Thus, it was recognized that the deterioration diagnosis of the pole transformer can be performed by measuring the magnetic field state of the commercial frequency on the exterior surface of the pole transformer and using the measurement result as diagnostic data.

  In view of the above-described points, an object of the present invention is to easily diagnose deterioration of a pole transformer by measuring the magnetic field state of the commercial frequency on the outer surface of the pole transformer.

The magnetic sensor for diagnosing a pole transformer according to the present invention is contacted or scanned along the outer surface of the pole transformer in order to diagnose the pole transformer from the magnetic field state of the commercial frequency of the outer face of the pole transformer. A magnetic sensor, a pair of magneto-impedance effect elements, a high-frequency current source circuit for applying a high-frequency excitation current to both magneto-impedance effect elements, and the detected magnetic field acting in the axial direction of each magneto-impedance effect element; Each detection circuit for demodulating the modulated wave with the modulated current magnetic field, an operational differential amplifier for differentially amplifying both detection outputs to obtain a detection difference output, and the output of the differential amplifier for each negative feedback winding A negative feedback circuit for negative feedback to both magneto-impedance effect elements via wires and a bias magnetic field winding for each magneto-impedance effect element In addition, there is provided a correction circuit that uses the offset of the differential amplifier output as an input signal, generates a compensation signal for canceling the offset, and applies the compensation signal to the amplifier as an input for erasing the offset. It is characterized by that.
Another magnetic sensor for diagnosing a pole transformer according to the present invention is to contact or scan along the outer surface of the pole transformer in order to diagnose the pole transformer from the magnetic field state of the commercial frequency on the outer face of the pole transformer. A pair of magneto-impedance effect elements, a high-frequency current source circuit for applying a high-frequency excitation current to both magneto-impedance effect elements, and a detected magnetic field acting in the axial direction of each magneto-impedance effect element Each detection circuit for demodulating a modulated wave modulated with a high-frequency excitation current magnetic field, an operational differential amplifier for differentially amplifying both detection outputs to obtain a detection difference output, and each negative feedback for the output of the differential amplifier Negative feedback circuit for negative feedback to both magneto-impedance effect elements via a coil winding, and a bias magnetic field winding for both magneto-impedance effect elements In addition, a correction signal for canceling the offset is generated using the offset of the differential amplifier output as an input signal, and the compensation signal is applied as an input for erasing the offset between both input terminals of the amplifier. A circuit is provided between both input terminals of the differential amplifier.
In these, the correction circuit is provided with means for generating a compensation output when the offset of the amplifier or differential amplifier output reaches a predetermined value, and the offset of the amplifier or differential amplifier output is multiplied by n (n > 1) and a means for inputting to the correction circuit can be provided.

  The winding and core are distorted by excessive electromagnetic force due to the large current flowing inside the winding such as lightning current and switching surge current entering from the secondary side of the transformer, and magnetic flux leaks even when normal load current is applied. The From the strength of the leakage magnetic field at the commercial frequency, it is possible to detect the degree of distortion of the winding and the core and to detect deterioration based on the history of lightning current and the like.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a circuit diagram of an example of a magneto-impedance effect sensor used in the present invention.
In FIG. 1, reference numeral 1 denotes a magneto-impedance effect element, which has a zero magnetostriction or a negative magnetostriction having an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other in the circumferential direction of the wire are alternately separated by domain walls. Amorphous alloy wire is used. The inductance voltage component in the output voltage between both ends of the wire generated when a high-frequency excitation current is passed through an amorphous magnetic wire having zero magnetostriction or negative magnetostriction is obtained by the circumferential magnetic flux generated in the cross section of the wire. This occurs due to the magnetization of the easily magnetizable outer shell in the circumferential direction. Therefore, the circumferential magnetic permeability mu _theta depends on the circumferential direction of magnetization of Dosotokara portion. Thus, when a signal magnetic field is applied in the axial direction of the amorphous wire being energized, the outer shell portion having the easily magnetizable property in the circumferential direction is obtained by synthesizing the circumferential magnetic flux and the signal magnetic field magnetic flux by the energization. direction of magnetic flux acting deviates from the circumferential direction, correspondingly hardly occur magnetization in the circumferential direction, the circumferential permeability mu _theta changes, the inductance voltage content will vary to. This fluctuation phenomenon is called a magnetic inductance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a signal magnetic field (signal wave). Further, when the frequency of the energization current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμ _θ ) ^1/2 (μ _θ is the circumferential permeability, ρ as described above. electrical resistivity, w is shows the angular frequency, respectively) is changed by mu _theta, so changed by the mu _{as theta} is the signal magnetic field, the resistance voltage of the in wire ends between the output voltage variation at the signal magnetic field To come. This fluctuation phenomenon is called a magneto-impedance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a signal magnetic field (signal wave).

  In FIG. 1, 2 is a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element, 3 is a signal magnetic field (signal wave) acting in the axial direction of the magneto-impedance effect element, and the high-frequency excitation current (carrier wave). A detector circuit for demodulating the modulated modulated wave, 4 an amplifier circuit for amplifying the demodulated wave, 5 an output terminal, 6 a negative feedback winding, and 7 a bias magnetic field winding.

In the magneto-impedance effect element 1, as described above, the direction of the magnetic flux acting on the outer shell portion that is easily magnetized in the circumferential direction is obtained by combining the circumferential magnetic flux based on the excitation current and the axial magnetic flux based on the signal magnetic field. Since the circumferential permeability μ _θ is changed from the circumferential direction, the inductance is changed, and the impedance is changed by changing the skin depth of the high frequency skin effect of the circumferential permeability μ _θ . Therefore, it is also circumferentially displaced by the synthesized magnetic field by ± signal magnetic field phi becomes ± phi, the circumferential direction of the magnetic field reduction ratio cos (± phi) is unchanged, the degree of reduction in thus mu _theta is the direction of the signal magnetic field It is not changed by positive or negative. Therefore, the signal magnetic field-output characteristic is substantially symmetrical with respect to the y axis when the signal magnetic field is taken on the x axis and the output is taken on the y axis as shown in FIG. This signal magnetic field-output characteristic is non-linear. Non-linear characteristics are unstable and high-sensitivity measurement is difficult. Therefore, negative feedback is applied with a negative feedback winding to linearize the output characteristics as shown in FIG. In FIG. 2B, Δw is a linear range where the gain without negative feedback is very large and the gain is determined only by the feedback rate β. However, with this output characteristic, since the polarity of the signal magnetic field cannot be determined, a bias magnetic field is applied by the bias winding 7 so that the polarity can be determined as shown in FIG. That is, the characteristic of (b) in FIG. 2 is moved in the negative direction of the x-axis by the bias magnetic field -Hb as shown in (c) of FIG. 2, and the maximum detection range of the signal magnetic field is within the range of the single diagonal line region. -Hmax to + Hmax.

The magneto-impedance effect element 1 is an alloy of transition metal and non-metal having a non-metal composition of 10 to 30 atomic%, particularly an alloy of transition metal and non-metal, and the amount of non-metal accounts for 10 to 30 atomic%. The transition metal is Fe and Co and the nonmetal is B and Si, or the transition metal is Fe and the nonmetal is B and Si. For example, the composition Co _70.5 B ₁₅ can be used. Si ₁₀ Fe _{4.5 having} a length of 2000 μm to 6000 μm and an outer diameter of 30 μm to 50 μmφ can be used. For the magneto-impedance effect element 1, an amorphous ribbon, an amorphous sputtered film, or the like can be used in addition to an amorphous wire having zero magnetostriction or negative magnetostriction.

  In the above, normal high frequency such as continuous sine wave, pulse wave, triangular wave, etc. can be used as the high frequency excitation current, and examples of the high frequency excitation current source include Hartley oscillation circuit, Colpitts oscillation circuit, collector tuning oscillation circuit, base tuning In addition to a normal oscillation circuit such as an oscillation circuit, a rectangular wave generator that integrates the square wave output of a crystal oscillator through an integration circuit via a DC cut capacitor and amplifies the triangular wave of this integration output by an amplification circuit, and oscillates a CMOS-IC The triangular wave generator etc. which were used as a part can be used.

As the above detection circuit, for example, a configuration in which a modulated wave is half-wave rectified by an operational amplifier circuit and this half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave, A configuration in which the modulated wave is half-wave rectified by a diode and the half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave can be used.
Further, it is possible to use tuning detection in which a signal wave is sampled by multiplying the modulated wave by a square wave having a frequency fs tuned to the modulated wave (frequency fs).
In the above embodiment, the detected magnetic field is extracted by demodulating the modulated wave. However, the present invention is not limited to this, and the high-frequency excitation current wave (carrier wave) modulated by the signal magnetic field (signal wave) acting on the magneto-impedance effect element. Any suitable detecting means can be used as long as it can detect the signal magnetic field.

The negative feedback winding and the bias magnetic field winding can be wound around a magneto-impedance effect element. Further, as shown in FIG. 3, a negative feedback winding and a bias magnetic field winding can be wound around the iron core constituting the magneto-impedance effect element and the loop magnetic circuit. 3A is a side view showing an example of a magnetic impedance effect unit with an iron core winding, FIG. 3B is a bottom view, and FIG. 3C is a cross-sectional view of FIG. FIG.
In FIG. 3, reference numeral 100 denotes a substrate chip, and for example, a ceramic plate can be used. Reference numeral 101 denotes an electrode provided on one side of the substrate piece, and includes a magneto-impedance effect element connecting projection 102. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. 1x is a magneto-impedance effect element connected between the protrusions 102 and 102 of the electrodes 101 and 101 by soldering or welding, and an amorphous wire, amorphous ribbon, sputtered film, or the like having zero or negative magnetostriction can be used as described above. 103 is a C-type iron core made of iron, ferrite or the like, 6x is a negative feedback winding wound around the C-type iron core, and 7x is a bias magnetic field winding. 103, both ends of the C-type iron core 103 are fixed to the other surface of the substrate piece 100 with an adhesive or the like so as to constitute a loop magnetic circuit. The iron core material may be a magnetic material having a small residual magnetic flux density. Examples thereof include permalloy, ferrite, iron, amorphous magnetic alloy, magnetic powder mixed plastic, and the like.

According to the present invention, in order to diagnose the pole transformer, the magnetic sensor is contacted or scanned along the outer surface (made of steel plate) of the pole transformer while power supply is continued. The pole transformer is usually an inner iron type, and the core is formed by stacking silicon steel plates. The exterior is made of steel plate. It is assumed that a lightning current has flowed through the pole transformer in the past and the winding has deteriorated.
In such a pole transformer, magnetic flux leaks to the outer surface of the exterior even under normal load current due to distortion of the core and windings during a lightning strike, and the magnetic field strength of the leakage flux at this commercial frequency is measured by the above contact or scanning. By doing so, it is possible to detect abnormality of the pole transformer.
A magnetic field generated from an electric wire or the like in the vicinity of the pole transformer is usually sufficiently small in phase balance, and the influence of the magnetic field can be well eliminated, and abnormality of the pole transformer can be detected with sufficient accuracy.
The leakage magnetic flux is AC at commercial frequency, and it is desirable to measure only the AC component by cutting the DC component with a cutoff capacitor or DC cut filter in order to eliminate the influence of residual magnetism on the transformer exterior.

A differential type as shown in FIG. 4 may be used for the magneto-impedance effect sensor.
In FIG. 4, reference numerals 1a and 1b denote a pair of magneto-impedance effect elements each having negative feedback windings 6a and 6b and bias magnetic field windings 7a and 7b.
Reference numeral 2 denotes a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element. Reference numerals 3a and 3b denote signal magnetic fields Hex (signal waves) acting in the axial direction of the magneto-impedance effect elements 1a and 1b. A detection circuit 4 for demodulating the modulated wave having a modulated carrier wave) is an operational differential amplifier for obtaining a detection output by differentially amplifying both detection outputs. Reference numeral 60 denotes a negative feedback circuit for negatively feeding back the output of the differential amplifier 4 to the negative feedback windings 6a and 6b. Reference numeral 5 denotes a detection output terminal.

The leakage magnetic flux based on the load current under the deformation of the winding or the core has directionality, and the direction and magnitude of the leakage magnetic flux varies depending on the position of the exterior outer surface.
Thus, in the differential sensor shown in FIG. 4, the magneto-impedance effect elements 1a and 1b are spaced apart at a predetermined interval, and leakage based on the load current acting on each magneto-impedance effect element during the contact / scanning is performed. If the intensity of the magnetic field is different due to the directionality and the intensity is H and H ′, HH ′ is detected.
According to this differential type, noise caused by an external magnetic field such as geomagnetism or a temperature change on each side of the differential is input to the differential amplifier in the same phase, so that the noise can be eliminated well.

In any of the magnetic sensors, it is required to adjust the offset of the operational amplifier during scanning, and as shown in FIGS. 5A to 5C, the offset change in the output of the operational amplifier is automatically compensated. As a result, offset adjustment can be performed during scanning.
In the magneto-impedance effect sensor shown in FIG. 5A, reference numeral 40 denotes an output correction circuit, and other configurations are the same as those in FIG. The output correction circuit 40 uses the offset of the output of the operational amplifier as an input signal, generates a compensation signal for canceling the offset, and adds this compensation signal to the amplifier as an input for erasing the offset.

FIG. 6A illustrates an example of an output correction circuit. The output of the operational amplifier is compared with the input to detect the offset. If the offset is positive (negative), the electronic volume switches SW ₋₁ and SW ₋₂ are detected. ,... (SW _{+ 1} , SW _{+ 2} ,...) _Are sequentially turned on and off by the control IC, and a negative (positive) output voltage is sent to the offset adjustment terminal of the operational amplifier to reduce the offset of the amplifier output. When the offset becomes 0, the switch state at that time is held.
The offset of the output of the operational amplifier may be set within a predetermined range, for example, a range of −1v to + 1v. In this case, when the offset of the amplifier output exceeds 1v, the electronic volume is operated.
Further, a buffer having a gain of 1 or more, for example, 2 times, is incorporated in the control IC, and when the offset of the amplifier output exceeds ± 0.5 V, the electronic volume is operated so that the offset of the operational amplifier output is −0.5 V. It can also be set within the range of ~ 0.5V.

In the magneto-impedance effect sensor shown in FIG. 5B, reference numeral 40 denotes an output correction circuit, and other configurations are the same as those in FIG. The output correction circuit 40 uses the offset of the output of the operational amplifier as an input signal, generates a compensation signal for canceling the offset, and adds this compensation signal to the amplifier as an input for erasing the offset.
Reference numeral 40 denotes an output correction circuit, which uses the offset of the operational differential amplifier 4 as an input signal, generates a compensation signal for canceling the offset, and applies this compensation signal to the amplifier as an input for erasing the offset. It is.
The output correction circuit shown in FIG. 6A can be used similarly to the above, and the offset is detected by comparing the output and input of the operational differential amplifier. If the offset is positive (negative), the electronic volume Switches SW ₋₁ , SW ₋₂ ,... (SW ₊₁ , SW ₊₂ ,...) _Are sequentially turned on and off by the control IC, and a negative (positive) output signal is applied to the offset adjustment terminal of the operational differential amplifier. When the offset of the differential amplifier output is reduced and becomes zero, the switch state at that time is maintained.
The offset of the output of the operational differential amplifier may be set within a predetermined range, for example, a range of -1v to + 1v. In this case, when the offset of the differential amplifier output exceeds 1v, the electronic volume is manipulated.
In addition, a buffer with a gain of 1 or more, for example, 2 times, is incorporated in the control IC so that if the offset of the differential amplifier output exceeds ± 0.5 V, the electronic volume is operated to reduce the offset of the operational differential amplifier output. It can also be set within the range of -0.5v to + 0.5v.

In the magneto-impedance effect sensor shown in FIG. 5C, reference numeral 40 denotes an output correction circuit, and other configurations are the same as those in FIG. The output correction circuit 40 uses the offset of the output of the operational amplifier as an input signal, generates a compensation signal for canceling the offset, and adds this compensation signal to the amplifier as an input for erasing the offset.
Reference numeral 40 denotes an output correction circuit connected between both input terminals of the operational differential amplifier 4. The offset signal of the differential amplifier output is used as an input signal to generate a compensation signal for canceling the offset signal. Is added as an input for erasing the offset.

FIG. 6B shows an example of the output correction circuit. The output of the differential amplifier is compared with the difference output of the differential amplifier to detect the offset of the differential amplifier, and the offset is shown in FIG. It is set to 0 by the volume operation shown in (b) of 6-2, and the switches SW ₀ , SW ₋₁ , SW ₋₂ ,..., SW ₀ , SW _+1,. This is done by operating SW ₊₂ .
Similarly to the above, the offset of the output of the operational differential amplifier may be set within a predetermined range, for example, the range of -1v to + 1v. In this case, the offset of the output of the operational differential amplifier is set to -1v or + 1v. If exceeded, the electronic volume is operated. In this case, the offset of the output of the operational differential amplifier is set to −0.5v to +0 so that the electronic volume is manipulated when a gain of 1 or more, for example, a double buffer is incorporated in the control IC and exceeds ± 0.5v. It is also possible to fit within the range of .5v.

  In the present invention, the leakage magnetic field on the outer surface of the pole transformer is measured by arranging a number of magneto-impedance effect element units on a flexible substrate, and detecting each of the magneto-impedance effect element units with a detection circuit-detection. It is also possible to use a non-scanning method by using a multi-head sensor provided with ends and applying this multi-head sensor to the bottom or side of the exterior.

  Instead of the magneto-impedance effect sensor, a magnetoresistive sensor (MR type sensor), a Hall effect type sensor, a fluxgate sensor, or a SQUID can be used.

  In the above, a measurement meter can be connected to the detection end of the sensor via a lead wire, and measurement can be performed on the ground. It is also possible to use a method in which the detection output of the sensor is modulated with a carrier wave having a predetermined frequency, and the detection output is measured by receiving and demodulating the modulated wave on the ground.

It is a circuit diagram which shows an example of the magneto-impedance effect sensor used in this invention. It is drawing which shows the detection characteristic of a magneto-impedance effect element. It is drawing which shows the magnetic impedance effect unit with a core winding used in the said magnetic impedance effect sensor. It is a circuit diagram which shows an example of the differential type magneto-impedance effect sensor used in this invention. It is a circuit diagram which shows an example different from the above of the magneto-impedance effect sensor used in this invention. It is a circuit diagram which shows an example different from the above of the magneto-impedance effect sensor used in this invention. It is a circuit diagram which shows an example different from the above of the magneto-impedance effect sensor used in this invention. 6 is a diagram illustrating an example of a detection output correction circuit 40 in FIGS. 6 is a diagram illustrating an example of a detection output correction circuit 40 in FIG.

Explanation of symbols

1 magneto-impedance effect element 2 high-frequency current source circuit 3
Detection circuit 4 Amplification circuit 5
Detection output terminal 6
Negative feedback winding
7 Bias magnetic field winding

Claims (2)

A magnetic sensor that is contacted or scanned along the outer surface of the pole transformer in order to diagnose the pole transformer from the commercial frequency magnetic field state of the outer surface of the pole transformer, and a pair of magneto-impedance effect elements, A high-frequency current source circuit for applying a high-frequency excitation current to both magneto-impedance effect elements, a detection circuit that demodulates the detected magnetic field from the output voltage of each magneto-impedance effect element, and a detection difference by differentially amplifying both detection outputs An operational differential amplifier for obtaining an output, a negative feedback circuit for negatively feeding back the output of the differential amplifier to both magneto-impedance effect elements via the negative feedback windings, and both magneto-impedance effect elements A bias magnetic field winding is provided, and an offset for offsetting the offset of the differential amplifier output as an input signal is provided. A magnetic sensor for pole transformer diagnosis, characterized in that it comprises a correction circuit to apply an input for thereby generating a use signal erasing the offset the compensating signal to the amplifier. A magnetic sensor that is contacted or scanned along the outer surface of the pole transformer in order to diagnose the pole transformer from the commercial frequency magnetic field state of the outer surface of the pole transformer, and a pair of magneto-impedance effect elements, A high-frequency current source circuit for applying a high-frequency excitation current to both magneto-impedance effect elements, a detection circuit that demodulates the detected magnetic field from the output voltage of each magneto-impedance effect element, and a detection difference by differentially amplifying both detection outputs An operational differential amplifier for obtaining an output, a negative feedback circuit for negatively feeding back the output of the differential amplifier to both magneto-impedance effect elements via the negative feedback windings, and both magneto-impedance effect elements Compensation for canceling the offset of the differential amplifier output using the bias magnetic field winding as an input signal A correction circuit is provided between the two input terminals of the differential amplifier, and a correction circuit is provided between the two input terminals of the amplifier for generating the signal and applying the compensation signal as an input for eliminating the offset between the two input terminals of the amplifier. Magnetic sensor for transformer diagnosis.

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