JP2011149896A - Partial discharge measuring method, locating method, and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a partial discharge measuring method capable of measuring with excellent SN ratio, partial discharge generated in a container of a power apparatus. <P>SOLUTION: In this partial discharge measuring method, which is a method for measuring partial discharge generated in the container 12 of the power apparatus 10 formed by storing a body part 14 in the metal container 12, the partial discharge is measured by measuring a potential V<SB>p</SB>on one or more points on the wall surface of the container 12. A three-dimensional generation position of the partial discharge can be also specified (namely, located) with high sensitivity by using this measuring method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to, for example, a transformer, a reactor, a capacitor, a rectifier, a circuit breaker, a switchgear, a switchboard, etc., and a partial discharge generated in a container of a power device in which a main body is housed in a metal container. The present invention relates to a measurement method for measuring, an orientation method for specifying a position where the partial discharge is generated, and related devices.

  Since accidents and breakdowns of electric power equipment are accompanied by power outages, the impact on the surroundings is very large. It is said that it is very effective to measure the partial discharge that occurs as a precursor phenomenon of dielectric breakdown in order to detect the abnormality of this electric power device at an early stage.

  As described in Non-Patent Document 1 (refer to page 7), partial discharge refers to discharge that bridges the insulation between the conductors only partially, and discharge that bridges the conductors completely. Not included.

  The generation mechanism of the partial discharge is described in detail in Non-Patent Document 1 (see, for example, pages 18-23), which will be briefly described with reference to FIG.

In the main body of the power equipment, there is an insulator 6 sandwiched between conductors 2 and 4 to which an AC voltage V _ac is applied, and there are minute voids (void defects) 8 in the insulator 6 (FIG. 1A However, the void 8 is not limited to the position shown in the figure.) The equivalent circuit can be represented by FIG. Here, C _g is the capacitance of the void 8, C _b is the combined capacitance of the portion of the insulator 6 in series with the void 8, and C _m is the static between the conductors 2 and 4 other than C _g and C _b. It is electric capacity.

In this case, the electric field concentrates on the void 8 as the AC voltage V _ac is applied. Therefore, as the instantaneous value of the AC voltage V _ac increases, the voltage applied to the void 8 (C _g ) also increases. When the voltage reaches the spark voltage of the void 8, spark discharge occurs in the void 8. This is a partial discharge. As a result, the voltage v _g across the void 8 (C _g ) decreases rapidly. The movement of charge due to a change of the rapid voltage v _g say discharge pulse. Such partial discharge is normally repeatedly generated every half cycle of the AC voltage V _ac as in the example shown in FIG. That is, the generation period of the partial discharge is usually twice the frequency of the AC voltage V _ac (for example, 120 Hz). However, the generation phase of the partial discharge is not limited to the illustrated example.

If the discharge charge moving through the void 8 due to the partial discharge is q _r and the charge lost from between the conductors 2 and 4 is q, the following relationship is established.

[Equation 1]
q = { _Cb / ( _Cb + _Cg )} _qr

As described above, as a result of the partial discharge, the charge q lost between the conductors 2 and 4 has a value different from the discharge charge q _r moved through the void 8. q is distinguished by referring to the apparent discharge charge (the magnitude of the discharge pulse) and q _r as the true discharge charge.

In actual measurement of partial discharge, since the capacitances C _g and C _b cannot generally be measured, the true discharge charge q _r cannot be measured. Therefore, it is important how to accurately measure the current (pulse current) corresponding to the apparent discharge charge q.

  FIG. 3 shows an example of a conventional partial discharge measuring method, and an equivalent circuit thereof is shown in FIG. A partial discharge measurement method using a circuit similar to this is also described in Non-Patent Document 1 (see, for example, pages 8-11).

  The power device 10 is configured by housing a main body 14 in a metal container 12. 18 is a lion. The electric power device 10 is simplified in illustration, but is, for example, a transformer, a reactor, a capacitor, a rectifier, a circuit breaker, a switchgear, a switchboard, or the like.

The main body 14 is, for example, a transformer main body when the electric power device 10 is a transformer, a reactor main body when the reactor is a reactor, a capacitor main body when the capacitor is a capacitor, and a rectifier main body when the power device 10 is a rectifier. In order to measure the partial discharge generated in the main body 14, an AC voltage V _ac is applied from the test AC power supply 20 to the main body 14.

  As can be seen from the generation mechanism of the partial discharge described above, the partial discharge portion is a kind of charge disappearance source 16 (see FIG. 4), which can be considered to exist in the main body portion 14. In the charge disappearance source 16, the aforementioned charge (apparent discharge charge) q disappears due to the partial discharge, and the disappearance is charged from the outside and compensated. This phenomenon is measured by partial discharge measurement.

In the conventional partial discharge measurement method, a coupling capacitor 22 is connected in parallel to the AC power supply 20, and a charging current I ₀ (this corresponds to the lost charge q) supplied from the coupling capacitor 22 to the charge dissipation source 16. Is converted into a pulse voltage V ₁ generated at both ends through the detection impedance Z _d of the detection circuit 24, and measured by the measuring device 26. This charging current I ₀ flows every time a partial discharge occurs. The waveform of the charging current I ₀ is generally a damped oscillation waveform determined by R, L, and C of the closed circuit. The same applies to the pulse voltage V ₁ . The measuring instrument 26 is an oscilloscope, for example. This is a measurement method that has been frequently used in the past.

Since the impedance Z ₀ and Z _d exist in the path of the charging current I ₀ and the high frequency impedance thereof is relatively large, the oscillation frequency of the charging current I ₀ and the pulse voltage V ₁ is, for example, several tens kHz to several hundreds. kHz order. This vibration frequency is different from the above-described partial discharge generation cycle. The measured waveform of the pulse voltage V ₁ will be described later with reference to FIG.

“Partial Discharge Measurement”, Institute of Electrical Engineers of Japan, Electrical Standards Committee, JEC-0401-1990, Denki Shoin, April 25, 1991, pp. 7-11, 18-26

In the conventional partial discharge measuring method, the SN ratio of the pulse voltage V ₁ that can be measured by the measuring instrument 26 is poor, and it is easily influenced by noise such as noise from the AC power supply 20 and external noise. There is a problem that it is difficult to perform measurement accurately.

This is because, as described above, since the high frequency impedance of the path of the charging current I ₀ is relatively large, the oscillation frequency of the charging current I ₀ is low, and that it is low means that the duration t is long, As can be seen from the following equation, when the same charge q is supplied when the duration t is long, the value of the charging current I ₀ becomes small and the value of the pulse voltage V ₁ also becomes small, making it difficult to distinguish from noise. Because. When the partial discharge is slight, the SN ratio becomes worse, so that measurement of the partial discharge becomes more difficult.

[Equation 2]
q = ∫I ₀ (t) dt

  Therefore, an object of the present invention is to provide a partial discharge measuring method capable of measuring a partial discharge generated in a container of a power device with a high SN ratio.

  Furthermore, it is another object of the present invention to provide a partial discharge position locating method capable of specifying with high sensitivity a three-dimensional generation position of a partial discharge generated in a container of a power device using the partial discharge measurement method. Yes.

  It is still another object to provide a partial discharge measuring sensor and a partial discharge measuring apparatus suitable for the above method.

  A partial discharge measuring method according to the present invention is a method for measuring a partial discharge generated in a container of a power device in which a main body is housed in a metal container, and is one or more points on the wall surface of the container. In this case, the partial discharge is measured by measuring the potential.

  There is always a floating electrostatic capacity between the wall surface of the container of the power device and the part of the partial discharge generated in the container. The inventors of the present application have found that the above-mentioned apparent discharge charge q that disappears due to partial discharge is compensated also from the floating electrostatic capacity, and a high-frequency pulse current flows through the wall surface of the container. The residual impedance of the pulse current charging path other than the stray capacitance is very small. This is because most of the residual impedance is the impedance of the wall surface of the container, and the impedance of the wall surface is very small because the wall surface is a surface.

  Therefore, the pulse current supplied from the stray capacitance is a high-frequency high-frequency damped oscillation current that rises sharply, and its duration t is very short. As can be seen from Equation 2 above, When supplying the same charge q, the value (amplitude) of the pulse current becomes very large. Corresponding to this pulse current, the potential of the wall surface of the container also changes steeply and greatly. Therefore, by measuring the potential at one or more points on the wall surface, the partial discharge generated in the container is improved in the SN ratio. Can be measured with high sensitivity.

  One of the partial discharge position locating methods according to the present invention uses the partial discharge measurement method to fix the first measurement point on the wall surface of the container of the electric power equipment, While moving a second measurement point different from the above, the point at which the position on the time axis of the signal waveform of the same partial discharge measured at the first and second measurement points overlaps is searched for, The step of specifying a perpendicular bisector between the second measurement point and the first measurement point is performed three times while changing the position of at least one of the first and second measurement points. Thus, three perpendicular bisectors intersecting at one intersection point are specified, three-dimensional coordinates of the intersection point are specified, and the coordinates of the intersection point are set as the partial discharge occurrence position.

  In another aspect of the partial discharge position locating method according to the present invention, when the container of the power device is a hexahedron or a cylinder, the partial discharge measurement method is used to specify a three-dimensional generation position of the partial discharge. Is.

  It is convenient to use a removable partial discharge measuring sensor for measuring the potential of the wall surface of the container.

  The invention according to claim 1 has the following effects. That is, when a partial discharge occurs, a very high frequency pulse current flows on the wall surface of the container of the power equipment, and the potential of the wall surface of the container also changes sharply and greatly in response to this pulse current. Therefore, by measuring the potential at one or more points on the wall surface, the partial discharge generated in the container can be measured with high SN ratio and high sensitivity.

  Moreover, in the above-described prior art, it is necessary to connect a high-voltage coupling capacitor for partial discharge measurement in parallel to the AC power supply. Therefore, (a) a high-voltage coupling capacitor is required. (B) The present invention has a problem that it takes a lot of time to connect, and (c) when the AC power supply cannot be stopped, the coupling capacitor cannot be connected, so the partial discharge cannot be measured. According to the present invention, since there is no need for a conventional coupling capacitor, the above problems (a) to (c) can be solved. Therefore, for example, it is possible to easily measure the partial discharge in the actually operating power equipment not only at a test site such as a factory but also at a site where the power equipment is operated.

  According to invention of Claim 2, there exists the following effect. That is, according to the partial discharge measuring method of claim 1, since the partial discharge can be measured with high SN ratio and high sensitivity, it is difficult to be affected by noise by using such a partial discharge measuring method. Therefore, the three-dimensional generation position of the partial discharge generated in the container of the power device can be specified with high sensitivity.

  In addition, as described above, since there is no need for an equivalent of a conventional coupling capacitor, the above-mentioned problems associated with providing a coupling capacitor can be solved. Therefore, for example, it is possible to specify the position of occurrence of partial discharge in a power device that is actually in operation not only at a test site such as a factory but also at a site where the power device is operated.

  According to invention of Claim 3-5, in addition to having the same effect as the effect of invention of Claim 2, there exists the following further effect. That is, since the method of searching for the point where the position on the time axis of the signal waveform of the same partial discharge measured at two measurement points overlaps, the occurrence of partial discharge is compared with the invention according to claim 2. The calculation for specifying the position is simplified. Therefore, it is more practical.

  The invention described in claim 6 has the following effects. That is, since the partial discharge measuring sensor can be attached to and detached from the wall surface of the container of the power device, it is easy to measure the potential of the wall surface of the container. Moreover, since this partial discharge measuring sensor has versatility, it can be easily applied to various power devices. Furthermore, since the partial discharge measuring sensor can be moved on the wall surface of the container, the operation of specifying the position where the partial discharge is generated becomes easy.

  Since the invention according to claim 7 includes the partial discharge measuring sensor according to claim 6, the same effect as the effect of the invention according to claim 6 is achieved.

It is the schematic for demonstrating the generation | occurrence | production mechanism of a partial discharge, (A) is sectional drawing in case a void exists in an insulator, (B) is the equivalent circuit schematic. It is the schematic which shows an example of the relationship between an applied alternating voltage and partial discharge. It is the schematic which shows an example of the conventional partial discharge measuring method. FIG. 4 is an equivalent circuit diagram of FIG. 3. It is the schematic which shows examples, such as a partial discharge measuring method and a partial discharge measuring apparatus which concern on this invention. FIG. 6 is an equivalent circuit diagram of FIG. 5. It is a figure which shows the example of the more concrete structure of the partial discharge measuring apparatus in FIG. 5 and FIG. It is a figure which shows an example of the signal waveform of the partial discharge measured by the conventional partial discharge measuring method which concerns on this invention. It is the schematic for demonstrating an example of the partial discharge position location method which concerns on this invention. It is the schematic which shows an example in case there exists a time difference in the signal waveform of the same partial discharge measured at two measurement points. It is the schematic for demonstrating the other example of the partial discharge position location method which concerns on this invention. It is the schematic which shows a mode when both signal waveforms are overlapped in the case where there is a time difference in the signal waveforms of the same partial discharge measured at two measurement points. It is the schematic for demonstrating the further another example of the partial discharge position location method which concerns on this invention. It is a figure which shows the horizontal plane in FIG.

(1) Partial discharge measuring method and related apparatus Examples of the partial discharge measuring method and the partial discharge measuring apparatus according to the present invention will be described with reference to FIGS. 3 and FIG. 4 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

  The partial discharge measuring method according to the present invention measures the partial discharge generated in the container 12 by measuring the potential at one or more points on the wall surface of the metallic container 12 of the power device 10 described above.

  The principle will be described with reference to an equivalent circuit shown in FIG.

  As described above with reference to FIG. 4, the partial discharge point is a kind of charge disappearance source 16, and it can be considered that this exists in the main body 14 of the power device 10. In the charge disappearance source 16, the aforementioned charge (apparent discharge charge) q disappears due to the partial discharge, and the disappearance is charged from the outside and compensated.

In the above-described prior art, the charging current I ₀ (this is a pulse current corresponding to the above-mentioned lost charge q) supplied from the coupling capacitor 22 (see FIG. 4) to the charge lost source 16 is measured. Even if the coupling capacitor 22 is not provided, the apparent discharge charge q disappears due to the partial discharge, and the disappearance charge q is compensated by some route. This is because the partial discharge phenomenon does not change depending on the presence or absence of the coupling capacitor 22.

As the compensation path, the inventors of the present application focused on the floating capacitance existing between the wall surface of the container 12 and a partial discharge location generated in the container 12. In other words, there is always a floating capacitance between the wall surface of the container 12 of the power device 10 and the portion of the partial discharge generated in the container 12. An example thereof is shown by floating electrostatic capacitances C ₁ and C ₂ in FIG. The apparent discharge charge q that disappears due to the partial discharge is compensated by the floating capacitances C ₁ and C ₂ , and the accompanying high-frequency pulse currents I ₁ and I ₂ flow through the wall surface of the container 12. The inventors have found. In addition, the residual impedances other than the stray capacitances C ₁ and C _{2 in} the charging paths of the pulse currents I ₁ and I ₂ are very small. This is because most of the residual impedance is the impedances Z ₁ and Z ₂ of the wall surface of the container 12 and the impedances Z ₁ and Z ₂ of the wall surface are very small because the wall surface is a surface.

Accordingly, the pulse currents I ₁ and I ₂ supplied from the floating electrostatic capacitances C ₁ and C ₂ become high-frequency damped oscillation currents that rise steeply and have a very short duration t. As can be seen from Equation 2 described above, when the same charge q is supplied, the values (amplitudes) of the pulse currents I ₁ and I ₂ become very large. Corresponding to the pulse currents I ₁ and I ₂ , the potential of the wall surface of the container 12 also changes steeply and greatly, so that the potential at one or more points on this wall surface (for example, the potential V _{p at the} point P) is measured. Thus, the partial discharge generated in the container 12 can be measured with high sensitivity and high sensitivity.

For simplification, assuming that the capacitances of the floating capacitances C ₁ and C ₂ are C and the inductance components of the impedances Z ₁ and Z ₂ of the wall surface of the container 12 are L, respectively, the pulse currents I ₁ and I ₂ The frequency f can be expressed by the following equation.

[Equation 3]
f ≒ 1 / 2π√ (LC)

The capacitance C is, for example, about several tens of pF. When the inductance component L is several μH, the frequency f is about several tens of MHz to 100 MHz. This is a frequency far higher than several tens kHz to several hundreds kHz, which is the frequency of the charging current I _{0 in} the case of the conventional measuring method described above.

In this embodiment, the wall surface potential V _p is measured by the measuring device 44 as the pulse voltage V ₂ using the partial discharge measuring sensor 30.

An example of the actual measurement result is shown in FIG. This figure shows that the partial voltage discharge of 100 pC is generated and the pulse voltage V _{1 in the} case of the conventional measurement method described above and the pulse voltage V _{2 in the} case of the measurement method according to the present invention are as follows: The results of simultaneous measurement with a two-channel measuring device (this corresponds to the measuring devices 26 and 44) are shown. Here, a digital oscilloscope DL1740 (4 input channels, maximum sampling speed (real-time sampling) 1 GS / s, frequency band 500 MHz) manufactured by Yokogawa Electric Corporation was used as the measuring instrument.

The time axes of the pulse voltages V ₁ and V ₂ are equally 2 μs / div. The frequency of the pulse voltage V ₁ is about 280 kHz, whereas the frequency of the pulse voltage V ₂ is about 20 MHz, which is a much higher frequency.

On the other hand, for the voltage axis, the channel of the pulse voltage V ₂ is 50 mV / div, while the channel of the pulse voltage V ₁ is 1 mV / div. This is because the pulse voltage V ₁ is small so that it can be enlarged and displayed easily. The output voltage (peak peak value) of the pulse voltage V ₁ is about 0.24 mV, whereas the output voltage (peak peak value) of the pulse voltage V ₂ is about 377 mV, which is much larger.

The actual measurement result shown in FIG. 8 is in good agreement with the above-described principle description of the measurement method according to the present invention. That is, the pulse voltage V ₁ is a small value and continues slowly for a long time, whereas the pulse voltage V ₂ rises sharply and very rapidly and rapidly decays. Therefore, by measuring the pulse voltage V ₂ , the partial discharge generated in the container 12 can be measured with high S / N ratio and high sensitivity.

In addition, since the rising time of the pulse voltage V ₂ is clear, it is convenient to measure the time difference between the signal waveforms of the two pulse voltages V _{2 in} the partial discharge position locating method described later.

  Furthermore, in the above-described prior art, it is necessary to connect the high-voltage coupling capacitor 22 for partial discharge measurement in parallel to the AC power supply 20, and therefore (a) the high-voltage coupling capacitor 22 is required. (B) There is a problem that it takes a lot of time to connect the coupling capacitor 22 and (c) when the AC power supply 20 cannot be stopped, the coupling capacitor 22 cannot be connected, so that partial discharge cannot be measured. On the other hand, according to the measuring method according to the present invention, since there is no need for a conventional equivalent to the coupling capacitor 22, the above problems (a) to (c) can be solved. Therefore, for example, it is possible to easily measure the partial discharge in the actually operating power device 10 not only at a test site such as a factory but also at a site where the power device 10 is operated. Therefore, it can be said that the utility value is very high.

  In the measurement method according to the present invention, the AC power supply 20 may be a test (partial discharge measurement) AC power supply or an AC power supply (for example, a commercial power supply) for actually operating the power device 10. But it ’s okay.

In order to measure the potential V _p of the wall surface of the container 12, a conductor may be directly attached to the wall surface of the container 12, but it is preferable to use the partial discharge measuring sensor 30 as in this embodiment.

The partial discharge measurement sensor 30 is also referred to in FIG. 7. In this example, the partial discharge measurement sensor 30 is close to the wall surface of the container 12 of the power device 10, thereby forming a capacitance C ₃ between the counter electrode 36 and the wall surface. The partial discharge measuring sensor 30 is connected to the container 12 so that one end is connected to the counter electrode 36 and the other electrode is connected to the ground potential portion, and the counter electrode 36 is close to the wall surface of the container 12. And attachment means 40 detachably attached to the wall surface.

  As shown in this example, the back surface of the counter electrode 36 is preferably covered with a grounded conductor (for example, metal) case 32, and the impedance element 38 is accommodated therein. If it does so, since case 32 will work as a shield box, it can control that external noise mixes in a measurement signal, and can raise SN ratio more. The case 32 and the counter electrode 36 are electrically insulated by an insulator 34.

The reason why the impedance element 38 is provided is to prevent the counter electrode 36 from becoming a floating potential and being easily affected by external noise unless it is provided. For the same reason, the impedance element 38 is preferably composed of an inductor or a resistor rather than a capacitor. Among them, if the impedance element 38 is formed of an inductor, the impedance element 38 has a low impedance for the commercial frequency and a high impedance for the pulse voltage V ₂ , and a low-pass that releases the commercial frequency noise to the ground. Since it works like a filter, the pulse voltage V ₂ can be extracted with a higher SN ratio.

  The attachment means 40 is, for example, a bonded magnet (also called a rubber magnet or the like), a magnet, a suction cup, or the like.

The capacitance C ₃ can be obtained by the following well-known expression. Here, S is an area [m ² ] of the counter electrode 36, L ₁ is a distance [m] between the counter electrode 36 and the wall surface of the container 12, and ε is a dielectric constant, which is about 9 × 10 ^{−12 in the} air. [F / m].

[Equation 4]
C ₃ = εS / L ₁ [F]

For example, when the counter electrode 36 is 10 cm square and the distance L ₁ is 2 mm, the capacitance C ₃ is about 45 pF. At this level, a sufficiently large pulse voltage V ₂ can be obtained.

The partial discharge measuring sensor 30 is detachably attached to the wall surface of the container 12 (for example, at a point P), and the pulse currents I ₁ and I ₂ flow due to the partial discharge generated in the container 12, so When the potential V _p changes, a pulse current flows through the impedance element 38 via the capacitance C _3, and the pulse voltage V ₂ is generated at both ends of the impedance element 38. Therefore, by measuring the pulse voltage V ₂ , the partial discharge generated in the container 12 can be measured.

In this measurement, as in this example, the partial discharge measuring sensor 30, a measuring device 44 for measuring the pulse voltage V ₂ generated at both ends of the impedance element 38, the partial discharging measuring sensor 30 and the measuring device 44, Alternatively, a partial discharge measuring device 50 having a conductor 42 for connecting may be used.

  The measuring device 44 is an oscilloscope, for example. A multi-channel oscilloscope is very convenient because the signal waveforms at a plurality of measurement points can be measured simultaneously with a single oscilloscope. More specifically, the measuring instrument 44 is a multi-channel digital oscilloscope as described above (see the description of FIG. 8). For example, the digital oscilloscope DL1740 described above. A higher-speed digital oscilloscope described later may be used.

  The conductor 42 is, for example, a coaxial cable. When the partial discharge measuring device 50 is used for the partial discharge position locating method described later and the signal waveforms at different measurement points are simultaneously measured, the lengths of the corresponding conductors 42 for the plurality of measurement points are the same. Keep it. This is because the propagation time difference of the electric signal in the conductor 42 is eliminated, and the position where the partial discharge is generated is specified accurately.

  According to the partial discharge measurement sensor 30 described above or the partial discharge measurement device 50 including the partial discharge measurement sensor 30, the partial discharge measurement sensor 30 can be attached to and detached from the wall surface of the container 12 of the power device 10. It becomes easy to measure the potential. Moreover, since the partial discharge measuring sensor 30 has versatility, it can be easily applied to various power devices 10. Furthermore, since the partial discharge measurement sensor 30 can be moved on the wall surface of the container 12, the operation | movement etc. which pinpoint the generation | occurrence | production position of a partial discharge become easy. For example, by using the partial discharge measurement sensor 30 or the partial discharge measurement device 50 including the partial discharge measurement sensor 30 in the first to fourth partial discharge position locating methods to be described later, it is easy to specify the position where the partial discharge is generated.

(2) Partial discharge position locating method Next, using the partial discharge measurement method described above, and further using the partial discharge measurement device 50 including the partial discharge measurement sensor 30 described above, a portion in the container 12 of the power device 10. Several examples of the partial discharge position locating method for specifying the discharge occurrence position will be described.

  The first partial discharge position locating method will be described with reference to FIG.

Using the partial discharge measurement method described above, partial discharge is measured at four different points (that is, four measurement points) on the wall surface of the container 12 of the power device 10. For example, these four points are represented by an orthogonal coordinate system and are represented as A (0, 0, 0), B (b, 0, 0), C (0, c, 0), and D (0, 0, d). . Also, let P _d (x, y, z) be the partial discharge occurrence position. The location of this occurrence is unknown.

Then, three detection time differences τ of the same partial discharge between two of the four points are measured between two different points. “The same partial discharge” means that, as described above with reference to FIG. 2, the partial discharge is normally repeatedly generated every half cycle of the AC voltage V _ac , but a predetermined one of them is generated. One partial discharge, for example, the partial discharge 70 in FIG. The same applies to the second to fourth partial discharge position locating methods described later. The partial discharge 70 and other partial discharges can be distinguished from each other because the period of the partial discharge is much longer than the time difference τ.

The partial discharge measurement at each point (measurement point) A to D is performed using, for example, the partial discharge measurement device 50 including the partial discharge measurement sensor 30 described above. That is, the above-described partial discharge measuring sensor 30 is attached to each of the points A to D. The same applies to the measurement of partial discharge at measurement points P _{1 to} P ₆ in the second to fourth partial discharge position locating methods described later. In particular, in the second to fourth partial discharge position locating methods to be described later, since the measurement point is moved, measurement is facilitated by using the partial discharge measurement sensor 30 that is easy to move.

The measuring device 44 constituting the partial discharge measuring apparatus 50 may be of a plurality of channels (for example, a multi-channel oscilloscope), and may be shared by a plurality of measurement points. Since the signal waveforms can be observed simultaneously, the time difference τ between the signal waveforms can be easily measured, and the number of measuring devices 44 can be reduced. For example, as in the example shown in FIG. 10, one of the pulse voltage V ₂ of the signal waveform of the measuring point measured by the channel CH1, and measuring the pulse voltage V ₂ of the signal waveform of the other measuring points channel CH2 The time difference τ between both signal waveforms is measured. The same applies to the second to fourth partial discharge position locating methods described later. When a plurality of signal waveforms can be observed simultaneously on the same screen, it becomes easier to find a point where both signal waveforms overlap (described later). Along with FIG. 12 and the description thereof, the number of measuring instruments 44 may be small.

  Further, when measuring the detection time difference τ between two measurement points, or when searching for a point where two signal waveforms overlap as in the case of the second to fourth partial discharge position locating methods described later, as described above. In addition, the lengths of the conductors 42 for the two measurement points are the same.

  Although the time difference τ is a propagation time difference of an electric signal and is very small compared to a sound wave, the time difference τ can be measured at present when the high-speed signal measurement technology has advanced. For example, the measurement can be performed using the digital oscilloscope DL1740 described with reference to FIG. A higher-speed digital oscilloscope made by the same company, such as the DL9000 series, may be used. The same applies to the second to fourth partial discharge position locating methods described later.

By the above measurement, in this example, the time difference τ _ab between the points AB, the time difference τ _ac between the points AC, and the time difference τ _ad between the points AD are measured. _Assuming that the distances between the points A, B, C, D and the partial discharge occurrence position P _d are L _a , L _b , L _c , L _d , respectively, the time differences τ _ab , τ _ac , τ _{ad respectively, L a -L b, L a} -L c, is proportional to L _a -L _d. The proportional constant is the speed of light C. Each distance L _{a to} L _d is specifically expressed by the following equation. b, c and d are known.

[Equation 5]
L _a = √ (x ² + y ² + z ² )
L _b = √ {(x−b) ² + y ² + z ² }
L _c = √ {x ² + (y−c) ² + z ² }
L _d = √ {x ² + y ² + (z−d) ² }

Therefore, the three time differences τ _ab , τ _ac , and τ _ad are respectively multiplied by known light speeds C to calculate three distances represented by the following equations.

[Equation 6]
L _a −L _b = τ _ab × C
L _a −L _c = τ _ac × C
L _a −L _d = τ _ad × C

Then, based on the three distances expressed by Equation 6, the three-dimensional generation position P _d (x, y, z) of the partial discharge is specified in consideration of Equation 5. Since there are three unknowns (x, y, z) and three equations as shown in Equation 6, this can be obtained by solving a ternary simultaneous equation.

The three time differences τ _ab , τ _ac , τ _ad are all measured using, for example, the four partial discharge measurement sensors 30 as described above, and further using, for example, an oscilloscope having four or more channels as the measuring instrument 44. The time differences τ _ab , τ _ac , and τ _ad may be measured separately. This is possible because, as described above, the partial discharge is normally repeatedly generated every half cycle of the AC voltage V _ac . That is, at least two points for measuring one time difference τ may be measured simultaneously. In that case, at least two partial discharge measuring sensors 30 are sufficient. When measuring another time difference τ, the partial discharge measuring sensor 30 may be moved.

  According to the first partial discharge position locating method, the following effects are obtained. That is, according to the partial discharge measuring method described above, the partial discharge can be measured with high S / N ratio and with high sensitivity. The three-dimensional generation position of the partial discharge generated in the container 12 of the device 10 can be specified with high sensitivity.

  One known partial discharge position locating method is an acoustic method for specifying the partial discharge occurrence position by measuring the propagation time difference of the sound at which the partial discharge occurs (for example, 13 of Non-Patent Document 1 above). Page, JP 2007-292700 A), the biggest problem of this method is that the detection sensitivity of sound is very poor, and therefore it is difficult to apply it unless it is a power device that is considerably deteriorated as a diagnostic target. On the other hand, the first partial discharge position locating method, as described above, is less susceptible to noise and can specify the position of occurrence of partial discharge with high sensitivity. Application to 10 is also possible. That is, early diagnosis is possible.

  In addition, since the first partial discharge position locating method is not required to be equivalent to the conventional coupling capacitor 22 as in the case of the partial discharge measurement method, the above-described problem associated with the provision of the coupling capacitor 22 is not necessary. Can be solved. Therefore, for example, it is possible to specify the position of occurrence of partial discharge in the power equipment 10 that is actually operating, not only at a test site such as a factory, but also on the site where the power equipment 10 is operated.

  A second partial discharge position locating method will be described with reference to FIG.

A first measurement point (for example, measurement point P ₃ ) is fixed on the wall surface of the container 12 of the power device 10 using the partial discharge measurement method described above, and a second different from the first measurement point. Of the same partial discharge signal waveform measured at the first and second measurement points while moving the measurement points (for example, moving the measurement point P ₄ parallel to the y-axis as indicated by the arrow A ₂ ). Search for points where positions on the time axis overlap.

For example, as in the example shown in FIG. 12, the signal waveform of the pulse voltage V ₂ at the first measurement point P ₃ is measured at the channel CH 1 using a multi-channel oscilloscope as the measuring instrument 44, and the second measurement point is measured. the pulse voltage V ₂ of the signal waveform of the P ₄ measured by the channel CH2. When the measurement point P ₄ is moved as indicated by the arrow A ₂ , the distance from the partial discharge generation position P _d changes, and the signal waveform of the channel CH 2 is on the time axis as indicated by the arrow F in FIG. Therefore, as shown by a two-dot chain line in FIG. 12, a point where the positions on the time axis of the signal waveforms of both channels CH1 and CH2 overlap is searched. Such an operation for searching for an overlapping point is possible because the partial discharge normally occurs repeatedly every half cycle of the AC voltage V _ac as described above. The same applies to other partial discharge position locating methods described later. Then, a perpendicular bisector 52 between the second measurement point P ₄ and the first measurement point P _{3 at} the overlapping point is specified. Vertical bisector plane 52 through the midpoint 62 between the two measuring points P _3, P _4, a plane orthogonal to the line connecting the two measurement points P _3, P _4.

Further, the step of specifying the vertical bisector as described above is performed three times by changing the position of at least one of the first and second measurement points, for example, the measurement point P _3. And P ₄ , the measurement at the measurement point P ₃ and the measurement point P ₆ different from the measurement point, and the measurement at the measurement point P ₁ and the measurement point P ₂ different from the measurement point P 3. Two vertical bisectors are specified, the three-dimensional coordinates (x, y, z) of the intersection are specified, and the coordinates (x, y, z) of the intersection are set as the partial discharge occurrence position P _d . .

Even moving the measuring point, if the non-superimposable but may be closer to two signal waveforms, so that than the moving direction further is generation position P _d of partial discharge to the outside, in which case, What is necessary is just to measure again after once moving the other party's measurement point to the said outer direction. The same applies to other partial discharge position locating methods described later.

  This second partial discharge position locating method is not limited to the hexahedron as in the example shown in FIG. 11 in the shape of the container 12 of the electric power device 10, and is also applicable to other shapes. Can do.

According to the second partial discharge position locating method, in addition to the same effects as those of the first partial discharge position locating method, the following further effects can be obtained. That is, since the method of searching for the point where the positions on the time axis of the signal waveform of the same partial discharge measured at two measurement points overlap is adopted, the partial discharge is compared with the first partial discharge position locating method. The calculation for specifying the occurrence position _Pd of the is simplified. Therefore, it is more practical.

  A third partial discharge position locating method suitable for the case where the container 12 of the power device 10 is a hexahedron (that is, a rectangular parallelepiped or a cube) will be described with reference to FIG. 11 again.

  Three axes of the orthogonal coordinate system in which the container 12 of the power device 10 is present are defined as an x-axis, a y-axis and a z-axis. More specifically, an orthogonal coordinate system is considered in which three surfaces orthogonal to each other at one point of the container 12 are parallel to the xy plane, the yz plane, and the xz plane, respectively, as shown in FIG.

  And the following 1st-3rd process is implemented using the partial discharge measuring method mentioned above. The order of implementation is not limited.

In the first step, the first measurement point P ₁ is fixed on the wall surface parallel to the xz plane of the container 12 of the power device 10, and the second measurement different from the _first measurement point P ₁ is performed. As in the case of the second partial discharge position locating method, the point P ₂ is moved in parallel to the x-axis as indicated by the arrow A ₁ (see, for example, FIG. 12 and the description thereof). A point where the positions on the time axis of the signal waveforms of the same partial discharge measured at the measurement points P ₁ and P ₂ overlap is searched, and the second measurement point P ₂ and the first measurement point P _{1 at the} overlap point are searched. The x coordinate of the midpoint 61 between is specified.

In the second step, the third measurement point P ₃ is fixed on the wall surface parallel to the yz plane of the container 12, and a fourth measurement point P ₄ different from the _third measurement point P ₃ is set. As shown by the arrow A ₂ , the signal waveforms of the same partial discharge measured at the third and fourth measurement points P ₃ and P ₄ are moved in the same manner as in the first step while being moved in parallel with the y-axis. The point where the positions on the time axis overlap is searched, and the y coordinate of the midpoint 62 between the fourth measurement point P ₄ and the third measurement point P ₃ at the overlapping point is specified.

In the third step, the fifth measurement point P ₅ is fixed on the wall surface parallel to the xz plane or the yz plane of the container 12, and the sixth measurement point is different from the _fifth measurement point P _5. While moving P ₆ parallel to the z-axis as indicated by arrow A ₃ , the same partial discharge measured at the fifth and sixth measurement points P ₅ and P ₆ is performed as in the first step. A point where the positions of the signal waveforms on the time axis overlap is searched, and the z coordinate of the midpoint 63 between the sixth measurement point P ₆ and the fifth measurement point P ₅ at the overlap point is specified.

Then, the three-dimensional coordinates (x, y, z) consisting of the x coordinate, the y coordinate, and the z coordinate specified in the first to third steps are set as a partial discharge generation position P _d in the container 12. As a result, the generation position P _d can be specified.

Note that, as in the example shown in FIG. 11, the third measurement point P ₃ may also serve as the _fifth measurement point P ₅ . By doing so, the number of measurement points can be reduced by one, which makes measurement easier. Similarly, when the z coordinate is specified on the wall surface parallel to the xz plane, the first measurement point P ₁ may also serve as the fifth measurement point P ₅ .

  The third partial discharge position locating method has the same effect as the second partial discharge position locating method.

  A fourth partial discharge position locating method suitable for the case where the container 12 of the power device 10 is cylindrical will be described with reference to FIGS. 13 and 14.

  The following first to third steps are performed using the partial discharge measurement method described above. The first step and the second step may be reversed.

In the first step, the first measurement point P ₁ is fixed on the side surface of the container 12 of the power device 10, and the second measurement point P ₂ different from the _first measurement point P ₁ is indicated by an arrow. As shown by A ₄ , while moving in the circumferential direction of the container 12, as in the second and third partial discharge position locating methods (for example, see FIG. 12 and its description), the first and second A point where the positions on the time axis of the signal waveforms of the same partial discharge measured at the measurement points P ₁ and P ₂ overlap is searched, and the second measurement point P ₂ and the first measurement point P _{1 at the} overlap point are searched. A vertical plane 56 is specified that passes through the midpoint 64 between them and includes the central axis 54 of the container 12 in the plane. Thereby, the deflection angle φ of the partial discharge generation position P _d in the cylindrical coordinate system can be specified.

In the second step, the third measurement point P ₃ is fixed on the side surface of the container 12, and a fourth measurement point P ₄ different from the _third measurement point P ₃ is indicated by an arrow A ₅ . In the same manner as in the first step, the time of the signal waveform of the same partial discharge measured at the third and fourth measurement points P ₃ and P ₄ while moving in parallel with the central axis 54 of the container 12 as described above. A horizontal plane 57 is searched for a point where the positions on the axes overlap, passing through a midpoint 65 between the fourth measurement point P ₄ and the third measurement point P ₃ at the overlap point and orthogonal to the vertical plane 56. Is identified. Thus, in the cylindrical coordinate system, z coordinates (height) of the generation position P _d of partial discharge can be identified.

In the third step, from the time difference on the time axis of the signal waveform of the same partial discharge measured at two points P ₅ and P ₆ where the intersecting line 58 of the vertical plane 56 and the horizontal plane 57 intersects the side surface of the container 12. The generation position of the partial discharge on the intersection line 58 is specified. Thus, in the cylindrical coordinate system, it is possible to specify the radius vector r of the generation position P _d of the partial discharge.

This third step will be described more specifically with reference to FIG. The distances from the two measurement points P ₅ and P ₆ to the partial discharge occurrence position P _d are m and n, respectively, and the time difference on the time axis of the signal waveform of the same partial discharge measured at both measurement points P ₅ and P ₆ . If τ is τ, the following relationship is established. C is the speed of light.

[Equation 7]
nm−τC

  On the other hand, when the radius of the horizontal plane 57 is R, the following equation is established. r is the above-mentioned moving radius.

[Equation 8]
r = R−m
r = n−R
∴r = (nm) / 2

  Therefore, the following equation is established from the above equations 7 and 8, whereby the moving radius r can be specified.

[Equation 9]
r = (τC) / 2

Then, the three-dimensional coordinates (r, φ, z) consisting of the deflection angles φ, z coordinates and the moving radius r identified in the first to third steps are used as the partial discharge occurrence position P _d in the container 12. To do. As a result, the generation position P _d can be specified.

  The fourth partial discharge position locating method has the same effect as the second and third partial discharge position locating methods.

10 power apparatus 12 container 14 body portion 20 AC power supply 30 partial discharge measurement sensor 36 counter electrode 38 impedance element 40 attachment means 42 conductor 44 meter 50 partial discharge measuring device P ₁ to P ₆ measurement points V _1, V ₂ pulse voltage P _d Location of partial discharge

Claims (7)

A method for measuring a partial discharge generated in a container of a power device comprising a main body housed in a metal container,
The partial discharge measuring method, wherein the partial discharge is measured by measuring a potential at one or more points on the wall surface of the container. Using the partial discharge measurement method according to claim 1,
Measure partial discharge at four different points on the wall surface of the container of the power device,
The difference in detection time of the same partial discharge between two of the four points is measured three times between two different points,
Calculate the three distances by multiplying the three detection time differences respectively by the speed of light,
A partial discharge position locating method, wherein a three-dimensional generation position of the partial discharge is specified based on the three distances. Using the partial discharge measurement method according to claim 1,
On the wall surface of the container of the electric power device, the first measurement point is fixed and the second measurement point different from the first measurement point is moved while the first and second measurement points are moved. A step of searching for a point where positions on the time axis of the measured signal waveforms of the same partial discharge overlap, and specifying a vertical bisector of the second measurement point and the first measurement point at the overlapping point , By changing the position of at least one of the first and second measurement points and performing three times, three perpendicular bisectors intersecting at one intersection point are specified, and 3 of the intersection points A partial discharge position locating method, characterized in that coordinates of a dimension are specified, and the coordinates of the intersection are used as the partial discharge occurrence position. The container of the electric power device is a hexahedron, and when the three axes of the orthogonal coordinate system in which the container exists are the x axis, the y axis, and the z axis,
Using the partial discharge measurement method according to claim 1,
On the wall surface parallel to the xz plane of the container of the power device, the first measurement point is fixed, and the second measurement point different from the first measurement point is moved in parallel with the x-axis, Searching for a point where positions on the time axis of the same partial discharge signal waveforms measured at the first and second measurement points overlap, the second measurement point and the first measurement point at the overlapping point, A first step of identifying the x-coordinate of the midpoint between
While fixing the third measurement point on the wall surface parallel to the yz plane of the container of the power device, moving the fourth measurement point different from the third measurement point in parallel to the y-axis, Searching for a point where positions on the time axis of the same partial discharge signal waveforms measured at the third and fourth measurement points overlap, the fourth measurement point and the third measurement point at the overlapping point, A second step of identifying the y-coordinate of the midpoint between
A fifth measurement point is fixed on a wall surface parallel to the xz plane or yz plane of the container of the power device, and a sixth measurement point different from the fifth measurement point is moved in parallel to the z axis. While searching for a point where the positions on the time axis of the signal waveforms of the same partial discharge measured at the fifth and sixth measurement points overlap, the sixth measurement point and the fifth measurement point at the overlapping point are searched. Performing a third step of specifying the z-coordinate of the midpoint between the measurement points;
A partial discharge position locating method, wherein a three-dimensional coordinate composed of the x coordinate, the y coordinate, and the z coordinate is used as the partial discharge occurrence position. The container of the power device is cylindrical,
Using the partial discharge measurement method according to claim 1,
The first measurement point is fixed on the side surface of the container of the power device, and the first measurement point is moved while moving the second measurement point different from the first measurement point in the circumferential direction of the container. And searching for a point where the positions on the time axis of the signal waveforms of the same partial discharge measured at the second measurement point overlap, and between the second measurement point and the first measurement point at the overlapping point A first step of identifying a vertical plane passing through the midpoint and including the central axis of the container in the plane;
The third measurement point is fixed on the side surface of the container of the electric power device, and the fourth measurement point different from the third measurement point is moved in parallel to the central axis of the container. Searching for a point where the positions on the time axis of the signal waveforms of the same partial discharge measured at the third and fourth measurement points overlap, and between the fourth measurement point and the third measurement point at the overlapping point A second step of identifying a horizontal plane that passes through the midpoint and is orthogonal to the vertical plane;
From the time difference on the time axis of the signal waveform of the same partial discharge measured at two points where the line of intersection between the vertical plane and the horizontal plane intersects the side surface of the container, the position where the partial discharge occurs on the line of intersection is specified. With the third step,
A partial discharge position locating method, wherein a three-dimensional generation position of the partial discharge is specified. A partial discharge measuring sensor used in the method according to claim 1,
A counter electrode that forms a capacitance with the wall surface by bringing it close to the wall surface of the container of the power device;
An impedance element having one end connected to the counter electrode and the other end connected to the ground potential portion;
A partial discharge measurement comprising: an attaching means for detachably attaching the partial discharge measurement sensor to the wall surface of the container of the power device so that the counter electrode is close to the wall surface of the container of the power device. sensor. The partial discharge measuring sensor according to claim 6,
A measuring instrument for measuring a voltage generated at both ends of the impedance element of the partial discharge measuring sensor;
A partial discharge measuring device comprising a conductor connecting the partial discharge measuring sensor and the measuring instrument.

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