JP2013029349A - Impulse current detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impulse current detection device such that an impulse current can be observed with high precision using a Rogowskii coil without using an external integration circuit having a wide bandwidth.SOLUTION: Addition means 6 sums up an electromotive force signal obtained by connecting a resistor 3 for internal integration across the Rogowskii coil and a signal generated by integrating the electromotive force signal by an external integration circuit 7 having a high-range cutting frequency f0 equal to a low-range cutting frequency of an internal integration function of the Rogowskii coil, the frequency f0 being 600-700 Hz and the gain of the external integration circuit 7 being 70-80 db.

Description

  The present invention relates to an impact current detection apparatus suitable for detecting an impact current caused by a lightning strike.

  Since the electromotive force output of the Rogowski coil is a differential output of the impact current, the impulse current detection device using the Rogowski coil needs to extract the integral component of the electromotive force of the Rogowski coil to observe the original impact current. There is.

For this reason, a resistor having a predetermined value is connected in series to the Rogowski coil to form an internal integration type Rogowski coil, and the electromotive force of the resistor is used as a detection signal.
However, the frequency characteristic of the internal integration type Rogowski coil is affected by the differential characteristic at a low frequency of 1 KHz or less as shown in FIG. Note that the resonance signal in the region indicated by the ellipse in FIG. 3 is removed by an appropriate circuit technique such as a filter.
For this reason, it is difficult to accurately reproduce a current having a wave tail duration of as long as 1 second, such as lightning caused by snow clouds in winter, using the internal integration function of the Rogowski coil.

  Therefore, as shown in Patent Document 1, the first external integration circuit having characteristics suitable for the integration of the high-frequency component of the signal of the Rogowski coil and the second external integration having characteristics suitable for the integration of the low-frequency component. It has been proposed to optimize and combine the circuits in series and integrate the signal from the Rogowski coil with one external integration circuit according to the frequency component.

  According to this, even if it is a low frequency component signal such as lightning current in winter, the current waveform can be accurately reproduced, but the signal integrated by one integration circuit is integrated again by the other integration circuit. In order to avoid it, there is a problem that the setting for matching circuit constants is extremely troublesome.

For this reason, as shown in Patent Document 2, an impact current detection device has also been proposed which can be integrated by an external integration circuit whose gain characteristics increase as the low frequency range, and accurately detect components from the low frequency range to the high frequency range as a whole. ing.
However, it is difficult in terms of stability and cost to realize an integration circuit having a flat gain in a band of about 7 digits from about 0.1 Hz to several MKHz, which is close to direct current.

Japanese Patent Laid-Open No. 11-51975 JP 2001-343403 A

  The present invention has been made in view of such problems, and the object of the present invention is to observe an impact current with high accuracy using a Rogowski coil without requiring a wide bandwidth integrating circuit. It is an object of the present invention to provide an impact current measuring device that can be used.

  In order to achieve such a problem, the present invention provides an electromotive force signal obtained by connecting an internal integration resistor to both ends of a Rogowski coil, and the electromotive force signal is reduced in the internal integration function of the Rogowski coil. The signal integrated by the external integration circuit having the high frequency cut frequency f0 as the high frequency cut frequency f0 is added by the adding means, the frequency f0 is 600 to 700 Hz, and the gain of the external integration circuit is 70 to 80 db. .

  According to the present invention, by setting the high-frequency cutoff frequency of the internal integration circuit of the Rogowski coil to about 500 to 700 Hz, the drooping characteristics of the external integration circuit are positively used, and components that are close to direct current are included. Not only can the tail be detected with high accuracy, but the external integration circuit only needs to correct the band from 0.1 Hz, which is the internal integration function of the Rogowski coil, to a range of about 4 digits. A high performance impact current measuring device can be provided.

  FIG. 1 shows an embodiment of an impact current detection device of the present invention, in which a Rogowski coil 1 (symbolized with an inductance L and an internal resistance R in the figure) has its inductance L and A resistor 3 that forms the internal integration circuit 2 together with the internal resistor R is connected to both ends thereof.

  As shown in FIG. 2A, the resistor 3 has a low-frequency cut frequency of 500 to 700 Hz (FIG. 2A) when the internal integration circuit 2 is constituted by the inductance and internal resistance of the Rogowski coil 1. Is selected to be a dotted line a).

  The electrical characteristics of the Rogowski coil 1 are selected so that the inductance L is 500 μH in this embodiment, and the resistance 3 is 1 Ω combined with the internal resistance R of the Rogowski coil 1. Thereby, the internal integration circuit 2 has a drooping characteristic of −20 db / decade in a region from about 500 to 700 Hz to 0.1 Hz.

  A resistor 4 for detecting an electromotive force is connected to a connection point between the Rogowski coil 1 and the resistor 3, and the electromotive force of the internal integration circuit 2 is connected to the input circuit 6 via the resistor 4 via the buffer 5. Is output.

  An external integration circuit 7 is connected to the resistor 4, and the integration output signal is output to the other input terminal of the addition circuit 6 via the buffer 8. The external integration circuit 7 is adjusted so that the high-frequency cut frequency matches the low-frequency cut frequency 500 to 700 Hz (dotted line a in FIG. 2B) of the internal integration circuit 2 as shown in FIG. Has been.

  Further, the gain of the external integration circuit 7, that is, the gain of the operational amplifier constituting the integration circuit is set to about 70 to 80 db. If the gain is larger than this, for example, 120 db, the influence of 1 / f noise becomes large, and it becomes difficult to detect the low frequency component, that is, the tail part of the shock current with high accuracy, and the gain is more than 70 to 80 db. If it is low, sufficient integration effect cannot be obtained.

As described above, the low frequency cut frequency of the internal integration circuit of the Rogowski coil is 500 to 700 Hz, the high frequency cut frequency of the external integration circuit is 0.1 Hz, and the gain is 70 to 80 db.
In this case, the external integration circuit stably corrects and outputs the gain of the signal from the Rogowski coil whose gain greatly depends on the frequency from 0.1 Hz to 500 to 700 Hz.
That is, the gain-frequency characteristic of the adder circuit 6 is flat at 0.1 Hz or more while cutting the DC component as shown in FIG.

In this embodiment, when an impact current is generated by a lightning strike while the Rogowski coil 1 is mounted on a structure whose lightning current is to be monitored, the electromotive force of the Rogowski coil 1 is detected.
This electromotive force is integrated by the internal integration circuit 2 formed by the inductance L of the Rogowski coil 1 and the combined resistance of the resistance R of the coil and the resistor 3, and is output to the resistor 4 as a signal proportional to the impact current value. The
This signal is input to one input terminal of the adder circuit 6 via the buffer 5, integrated by the external integration circuit 7, and input to the other input terminal of the adder circuit 6 via the buffer 10.

  Since the reactance of the Rogowski coil 1 does not act so much in the low frequency component of the lightning current, the current is determined by the internal resistance R and the resistance 3, so that the voltage across the inductance L is a voltage obtained by differentiating the lightning current.

  The tail portion of the impact current is a component having a frequency lower than the high frequency cut frequency 500 to 700 Hz of the internal integration circuit 2 formed by the inductance L of the Rogowski coil 1 and the combined resistance of the resistance R of the coil and the resistor 3. Therefore, the integral gain in the internal integration circuit 2 is very small, and substantially only the electromotive force due to the impact current detected by the Rogowski coil 1, that is, only the signal applied to the resistor 3 is supplied to the external integration circuit 7. Will be input.

  Since the external integration circuit 7 has a drooping characteristic of −20 db / decade with 0.1 Hz as a low-frequency cut frequency and 500 to 700 Hz as a high-frequency cut frequency, the inductance L of the Rogowski coil 1 and the resistance R of the coil. Therefore, the drooping characteristic of the internal integration circuit 2 formed by the combined resistance of the resistor 3 and the resistor 3 is contradictory, and a flattened signal is output from 0.1 Hz to 500 to 700 Hz.

  On the other hand, in the high frequency component of lightning current, since the inductance L acts greatly on the current value, the voltage across the inductance is induced proportionally to the current differentiation and is almost balanced with the input, so the voltage across the resistor connected in series Is the integral value.

  Therefore, the high frequency component current is converted into a voltage signal by the internal integration function of the Rogowski coil, and the low frequency component current having a long duration is converted into a voltage signal by the external integration circuit 2, and these two signal components are added. It is possible to obtain a voltage signal that is synthesized by the device 9 and accurately reproduces the waveform pattern of the entire impact current.

  Further, only the region of about 4 digits of the lightning current frequency of 0.1 Hz to 500 to 700 Hz is integrated by the high gain external integration circuit 2, and the component in the frequency region higher than the frequency of 500 to 700 Hz is the gain of the Rogowski coil itself. However, since the internal integration function in a region that does not depend on the frequency characteristics is used, a stable external integration circuit can be easily configured, and a measurement apparatus that can ensure traceability for the measurement result can be realized.

It is a block diagram which shows one Example of the impact current detection apparatus of this invention. FIGS. 9A to 9C are diagrams showing frequency-gain characteristics of signals output from the Rogowski coil, the external integration circuit, and the adder, respectively. It is a diagram which shows the frequency-gain characteristic of an internal integral type Rogowski coil.

    1 Rogowski coil 2 Internal integration circuit 4 Detection circuit 6 Adder 7 External integration circuit 5, 8 Buffer

Claims (1)

In an impact current detecting device that detects an impact current by integrating an electromotive force of a Rogowski coil, an electromotive force signal obtained by connecting an internal integration resistor to both ends of the Rogowski coil, and the electromotive force signal The signal integrated by an external integration circuit that uses the low-frequency cut frequency f0 of the Rogowski coil internal integration function as the high-frequency cut frequency f0 is added by an adding means, and the frequency f0 is 600 to 700 Hz. An impact current detection device having a circuit gain of 70 to 80 db.

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