JP2006284261A - Residual magnetic flux measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a residual magnetic flux measuring instrument for a transformer capable of accurately measuring residual magnetic flux even if time has lapsed since an interruption time point. <P>SOLUTION: This residual magnetic flux measuring instrument measures residual magnetic flux by using: a transformer voltage measuring means 6 for measuring a transformer voltage; two DC voltage component calculation means 9 each calculating a DC voltage component 10 from a transformer voltage signal 8 within a prescribed past time period; two voltage integration means 11 each calculating a voltage integration signal 12 by voltage-integrating a signal obtained by removing the voltage component 10 from the voltage signal 8 at present; two magnetic flux DC component calculation means 13 each calculating a magnetic flux DC component 14 from the integration signal 12 within a prescribed past time period; and two magnetic flux calculation means 15 each finding a magnetic flux signal 16 obtained by removing the DC component 14 from the integration signal 12 at present. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transformer residual magnetic flux measuring device.

  In the conventional residual magnetic flux measuring device, the voltage waveform of the transformer is measured and integrated to obtain the magnetic flux waveform, and the average value of the maximum value and the minimum value of the magnetic flux waveform is subtracted as a DC component correction term to remain. The magnetic flux is obtained (see, for example, Patent Document 1).

  In the conventional residual magnetic flux measuring device, the voltage waveform of the transformer is measured and integrated to obtain the magnetic flux waveform. At this time, the final value of the magnetic flux waveform and the center of the sine wave vibration before the power is shut off are obtained. The residual magnetic flux is calculated | required by calculating | requiring the difference with (for example, refer patent document 2).

JP 2-179220 A JP 2000-275311 A

  In the conventional residual magnetic flux measuring device, it is assumed that the transformer voltage and the residual magnetic flux fluctuate only before and after the transformer is shut off. However, if the transformer circuit breaker is equipped with an inter-pole capacitor, not only before and after the circuit breaker but also when the transformer circuit breaker is open, system faults occur and the power supply voltage fluctuates. In such a case, the transformer voltage and the residual magnetic flux may fluctuate via the inter-pole capacitor. In order to accurately measure the residual magnetic flux even under such circumstances, it is necessary to always measure the voltage waveform of the transformer and obtain the residual magnetic flux by integral calculation.

  When the continuous measurement of the residual magnetic flux is realized with the configuration of the conventional apparatus, the final value of the magnetic flux waveform is obtained by integrating all voltage waveforms from immediately before the interruption to the present time. Therefore, it is necessary to obtain a voltage integral value for a long-time voltage waveform as time elapses from the cutoff point. In this case, there is a problem that a drift occurs in the voltage integral value due to fluctuation of the DC offset component superimposed on the voltage waveform, and the accurate residual magnetic flux cannot be calculated as time elapses.

  The present invention has been made to solve the above-described problems, and has an object to accurately measure the residual magnetic flux even when time elapses from the cutoff point.

  The residual magnetic flux measuring device according to the present invention includes a voltage direct current component calculating means for calculating the voltage direct current component of the voltage of the transformer, and a voltage integrating means for calculating the voltage integral signal by removing the voltage direct current component from the voltage of the transformer. And at least two systems comprising a magnetic flux direct current component calculating means for calculating a magnetic flux direct current component from the voltage integrated signal and a magnetic flux calculating means for calculating the magnetic flux signal by removing the magnetic flux direct current component from the voltage integrated signal. It is a characteristic.

  The residual magnetic flux measuring device according to the present invention includes a voltage direct current component calculating means for calculating the voltage direct current component of the voltage of the transformer, and a voltage integrating means for calculating the voltage integral signal by removing the voltage direct current component from the voltage of the transformer. Since there are at least two systems comprising a magnetic flux direct current component calculating means for calculating the magnetic flux direct current component from the voltage integrated signal and a magnetic flux calculating means for removing the magnetic flux direct current component from the voltage integrated signal and calculating the magnetic flux signal. The residual magnetic flux can be accurately measured even if time elapses from the interruption point.

Embodiment 1 FIG.
FIG. 1 is a block diagram of a residual magnetic flux measuring apparatus showing an embodiment of the present invention. A circuit breaker 3 is connected between the power source 1 and the transformer 2. The transformer voltage is measured by the instrument transformer 4 connected to the primary side of the transformer 2. In this embodiment, the transformer voltage is measured by connecting the instrument transformer 4 to the primary side of the transformer 2, but it may be measured by connecting to the secondary side, and there is a tertiary connection. When doing so, it may be measured by connecting to the tertiary side. In the present embodiment, a single-phase transformer is described as an example, but it goes without saying that a three-phase transformer can be realized with the same configuration.

  In the drawings, the same reference numerals denote the same or corresponding parts, and this is common throughout the entire specification. Further, the description of the constituent elements appearing in the whole specification is merely an example and is not limited to these descriptions.

  The transformer voltage measurement means 6 obtains a transformer voltage signal 8 by performing A / D conversion (analog / digital conversion) on the measurement voltage 7 obtained by the instrument transformer 4 at predetermined time intervals.

  First, the voltage DC component calculating means 9 calculates the voltage DC component 10 from the transformer voltage signal 8 stored for the past predetermined time. For example, when the A / D conversion speed is 5000 samples / second and the time length is 100 msec, the transformer voltage signal 8 for the last 500 samples is stored. Each time the latest transformer voltage signal 8 is obtained, the voltage direct current component 10 is calculated by the voltage direct current component calculation means 9 using the data of the transformer voltage signal 8 for the latest 500 samples. As a method of calculating the voltage DC component 10, the average value of the transformer voltage signal 8 for 500 samples may be used, the median value of the transformer voltage signal 8 for 500 samples may be used, or the sample for 500 samples may be used. An intermediate value between the maximum value and the minimum value of the transformer voltage signal 8 may be used. In this way, the voltage DC component 10 of the voltage of the transformer 2 can be calculated by the voltage DC component calculation means 9.

  Next, each time the latest transformer voltage signal 8 is obtained by the voltage integration means 11, the voltage integral of the previous sample is obtained by subtracting the voltage DC component 10 from the latest (latest) transformer voltage signal 8. By adding the signal 12, the latest voltage integration signal 12 can be obtained. That is, the voltage integrating unit 11 calculates the voltage integrated signal 12 by removing the voltage DC component 10 from the voltage of the transformer 2.

  The magnetic flux direct current component calculating means 13 calculates the magnetic flux direct current component 14 from the voltage integration signal 12 stored for the past predetermined time. For example, in the case of the above-described A / D conversion speed and time length, the voltage integration signal 12 for the latest 500 samples is stored. Every time one sample of the latest voltage integration signal 12 is obtained, the flux DC component 14 is calculated using the data of the voltage integration signal 12 for the most recent 500 samples. As a calculation method of the magnetic flux direct current component 14, the average value of the voltage integrated signal 12 for 500 samples may be used, the median value of the voltage integrated signal 12 for 500 samples may be used, or the voltage integrated signal for 500 samples may be used. An intermediate value between 12 maximum values and minimum values may be used. In this way, the magnetic flux direct current component calculating means 13 can calculate the magnetic flux direct current component 14 from the voltage integration signal 12.

  Further, the magnetic flux calculating means 15 can calculate the magnetic flux signal 16 by subtracting the magnetic flux direct current component 14 from the latest voltage integrated signal 12 every time one sample of the latest voltage integrated signal 12 is obtained. Note that the magnetic flux signal 16 may be normalized so that the amplitude of the magnetic flux signal 16 becomes 1 when the transformer voltage is in the rated application state. The magnetic flux calculating means 15 can calculate the magnetic flux signal 16 by removing the magnetic flux direct current component 14 from the voltage integration signal 12.

  When the magnetic flux signal 16 is obtained by the above method, when the transformer voltage signal 8 changes transiently, the A / D conversion speed and time length shown above are taken as an example, and 500 samples are output until a correct value is output. A sample time of +500 samples = 1000 samples, that is, a delay time of 200 msec is generated.

  The system composed of the voltage direct current component calculating means 9, the voltage integrating means 11, the magnetic flux direct current component calculating means 13 and the magnetic flux calculating means 15 includes at least two systems. Hereinafter, two systems will be described as an example. These two systems are called A system and B system, and are called main system and sub system according to their roles.

  The control means 17 uses the magnetic flux signal 16, the transformer voltage signal 8, the contact signal 5 which is a signal linked to the opening / closing position of the circuit breaker 3, etc. It can be transmitted to the DC component calculating means 13 and controlled. Further, the control means 17 calculates a residual magnetic flux 18.

  Next, operation | movement of the control means 17 is demonstrated using FIG.

  At the first point of time, system A will be described as a main system and system B will be described as a sub system. The control means 17 detects the opening point of the circuit breaker 3 using the contact signal 5 which is a signal interlocked with the opening / closing position of the circuit breaker 3, and at the same time uses the contact signal 5 to indicate that the circuit breaker 3 is open and the transformer voltage The voltage generation point, which is the time when the absolute value of the signal 8 exceeds the threshold, is always detected.

  In FIG. 2, the opening point is detected at time 101. When the opening point or the voltage generation point is detected, the calculation control signal 19 of the main system is turned off, and the calculation of the voltage DC component calculation means 9 and the magnetic flux DC component calculation means 13 of the main system is stopped. As a result, the subsequent magnetic flux signal 16 is calculated while the values of the voltage DC component 10 and the magnetic flux DC component 14 of the main system are fixed to the values immediately before the opening.

  Next, it is detected whether or not the maximum value of the absolute value of the transformer voltage signal 8 has become equal to or less than the threshold value within the past predetermined time. The predetermined time is set to be equal to or longer than the delay time described above. Here, explanation will be given by taking 200 msec shown above as an example. The time point 102 when the transformer voltage signal 8 has become equal to or lower than the threshold value for the past 200 msec is detected. At this time, it is considered that the magnetic flux signal 16 of the main system has converged, and the convergence value Δf1 of the magnetic flux signal 16 at this time is stored. Next, the calculation control signal 19 is turned on, and the calculation of the voltage direct current component calculating means 9 and the magnetic flux direct current component calculating means 13 of the main system is resumed. Further, by switching between the main system and the sub system, the system B becomes the main system after 102.

  Next, a voltage generation point is detected at a point 104 in FIG. When the voltage generation point is detected, similarly, the main system calculation control signal 19 is turned off, and the calculation of the main system voltage DC component calculating means 9 and the magnetic flux DC component calculating means 13 is stopped. Thus, the subsequent magnetic flux signal 16 is calculated while the values of the voltage direct current component 10 and the magnetic flux direct current component 14 of the main system are fixed to the values immediately before opening.

  Similar to the previous case, the time point 105 at which the maximum value of the absolute value of the transformer voltage signal 8 has fallen below the threshold value over the past 200 msec is detected. At this time, it is considered that the magnetic flux signal of the main system has converged, and the convergence value Δf2 of the magnetic flux signal 16 at this time is additionally stored. Next, the calculation control signal 19 is turned on, and the calculation of the voltage direct current component calculating means 9 and the magnetic flux direct current component calculating means 13 of the main system is resumed. Then, the main system and the sub system are switched. As a result, after 105, the A system becomes the main system.

  By repeating this, every time a voltage generation point appears, the convergence value of the magnetic flux signal 16 is additionally stored and the residual magnetic flux 18 is calculated.

  That is, when the circuit breaker 3 of the transformer 2 is opened, or when the circuit breaker 3 is open and the absolute value of the voltage of the transformer 2 exceeds a threshold value, the control means 17 The calculation of the DC voltage component 14 and the magnetic flux DC component 14 is stopped when the absolute value of the maximum voltage of the transformer 2 within a predetermined time becomes equal to or less than the threshold value. The main system and the sub system are switched.

  The residual magnetic flux 18 is obtained from the sum of the convergence values of the magnetic flux signal 16 stored up to the present after the breaker 3 is opened. The residual magnetic flux 18 at the right end of FIG. 2 is calculated as Δf1 + Δf2 + Δf3.

  A flowchart of the control means 17 is shown in FIG. First, when there is an open-point detection or a voltage generation point detection, the calculation control signal of the main system is turned off. Next, when the maximum value of the absolute value of the transformer voltage signal 8 within the past certain time is equal to or less than the certain value, the magnetic flux signal value is stored. Next, the main system calculation control signal 19 is turned on to switch between the main system and the sub system. By repeating this, the control means 17 stores the convergence value of the magnetic flux signal 16 of the main system before restarting the calculation, and calculates the sum of the convergence values after the circuit breaker 3 is opened as the residual magnetic flux 18. can do.

  According to the present invention, the residual magnetic flux is calculated using only the transformer voltage signal 8 before and after the voltage fluctuation occurs, and when calculating the magnetic flux signal 16 from the measured transformer voltage signal 8, In order to compensate for the inaccuracy of the magnetic flux signal value in the delay time portion generated when the voltage DC component 10 and the magnetic flux DC component 14 are removed. The operation part is configured to have two systems. As a result, there is an unprecedented remarkable effect that the residual magnetic flux 18 can be accurately measured even with respect to the transformer voltage signal 8 under all conditions.

It is a block diagram which shows the residual magnetic flux measuring apparatus by Embodiment 1 of this invention. It is a figure which shows the timing chart which shows operation | movement of the residual magnetic flux measuring apparatus by Embodiment 1 of this invention. It is a figure which shows the flowchart which shows operation | movement of the control means of the residual magnetic flux measuring apparatus by Embodiment 1 of this invention.

Explanation of symbols

1 power supply, 2 transformer, 3 circuit breaker, 4 instrument transformer, 5 contact signal, 6 transformer voltage measurement means, 7 measurement voltage, 8 transformer voltage signal, 9 voltage DC component calculation means, 10 voltage DC component, 11 voltage integrating means, 12 voltage integrated signal, 13 magnetic flux direct current component calculating means, 14 magnetic flux direct current component, 15 magnetic flux calculating means, 16 magnetic flux signal, 17 control means, 18 residual magnetic flux.

Claims (3)

Voltage DC component calculating means for calculating the voltage DC component of the voltage of the transformer;
Voltage integration means for calculating a voltage integration signal by removing the voltage DC component from the voltage of the transformer;
Magnetic flux direct current component calculating means for calculating a magnetic flux direct current component from the voltage integration signal;
A residual magnetic flux measuring device comprising at least two systems comprising magnetic flux calculation means for calculating a magnetic flux signal by removing the magnetic flux direct current component from the voltage integration signal. When the transformer circuit breaker is opened, or when the circuit breaker is open and the absolute value of the voltage of the transformer exceeds the threshold, the calculation of the voltage DC component and the magnetic flux DC component of the main system is stopped,
When the absolute value of the maximum voltage of the transformer within a predetermined time is equal to or less than a threshold value, the calculation of the voltage DC component and the magnetic flux DC component of the main system is resumed,
The residual magnetic flux measuring apparatus according to claim 1, further comprising a control unit that switches between the main system and the sub system. 3. The residual magnetic flux according to claim 2, wherein the convergence value of the magnetic flux signal of the main system is stored before restarting the calculation, and the sum of the convergence values after the circuit breaker is opened is calculated as the residual magnetic flux. measuring device.

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