JP3390691B2 - Current measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current measuring device for measuring a current flowing through a bus bar center conductor of GIS.

[0002]

2. Description of the Related Art FIG. 10 shows, for example, JP-A-63-2015.
FIG. 19 is a block diagram of a current measuring device using a Rogowski-type current transformer, which is similar to that shown in Japanese Patent Publication No. 69. In the figure, 1 is a current measurement target line such as a power bus, 2
Is a Rogowski type current transformer attached to the current measurement target line 1 and is hereinafter referred to as a Rogowski coil. 3 is an analog circuit for converting the output of the Rogowski coil 2 into an appropriate voltage signal, 4 is an A / D converter for converting the analog voltage signal output of the analog circuit 3 into a digital signal, and 5 is an A / D
A microcomputer for controlling the converter 4 to calculate the result (hereinafter also referred to as CPU), 6 is a C
This is an E / O module that converts the output signal of the PU 5 into an optical signal for transmission to a distant place, but is not used when the distance is short and may be sent to the next stage as an electric signal as it is without being used. 6
Reference numeral 1 is an optical cable for transmitting an optical output signal of the E / O module 6.

Reference numeral 7 is a display device for displaying the result of the microcomputer 5. Since the display device 7 is generally installed in a place far away from the measurement target line 1,
The optical signal line 61 becomes long, and an optical amplifier (not shown) may have to be installed in the middle if necessary.

Reference numeral 20 denotes an analog circuit 3, an A / D converter 4,
It is a DC / DC power supply unit for supplying power to the CPU 5, and is insulated from the input and the output, but its withstand voltage is at the electronic circuit level and is not generally high. 5
Reference numeral 1 is a substation power source (DC 100v in this case) line of a substation or a power plant where this type of current measuring device is often used. The current measuring device 100 includes the Rogowski coil 2 and
Analog circuit 3, A / D converter 4, CPU 5, DC / D
It is composed of a C power supply unit 20.

When a current flows through the wire 1 to be measured, a voltage corresponding to the magnitude of the current is generated in the Rogowski coil 2.
The detected voltage is adjusted by the analog circuit 3 to a voltage level suitable for the subsequent processing and input to the A / D converter 4. The microcomputer 5 controls the A / D converter 4, calculates the current value as a digital value, and outputs the calculation result as E.
The image is displayed on the display device 7 (display, printer, etc.) via the / O module 6 and the optical cable 61.

Next, the operation will be described. Generally, if the input line of the analog circuit 3 (the line connecting the Rogowski coil 2 and the analog circuit 3) is lengthened, noise tends to be picked up and the S / N ratio deteriorates. Therefore, the current measuring device configured as described above. When 100 is applied to a GIS circuit breaker and the current flowing through the center conductor of the GIS tank is detected, the current measuring device 100 is required to be attached to the outer wall of the GIS tank in order to shorten the wiring length. However, when the current measuring device 100 is easily attached to the outer wall of the GIS tank, if an accident such as a lightning strike or a ground fault occurs in the GIS,
The potential of the outer wall of the tank rises significantly with respect to the ground. The electric potential of a case (not shown) or the like housing the electronic circuit also rises, and as a result, the electric potential of a circuit such as a power source or a signal line of the electronic circuit which is capacitively coupled to the case also rises. The power source 51 is usually at ground potential, so the voltage is DC / D.
The insulation of the C power supply unit 20 is destroyed, and as a result, electronic circuits such as the analog circuit 3 and the CPU 5 are also destroyed.

[0007]

The conventional current measuring device is constructed as described above, and is mounted on the GIS tank because the insulation voltage of the DC / DC power supply unit cannot withstand the rising voltage of the GIS tank at the time of an accident. Therefore, there is a problem that it is difficult to use for current detection of GIS.

Further, if the current detection device is attached to a place far away from the display device, the optical signal output cable length becomes long, and there is a problem that it is expensive.

The present invention has been made to solve the above problems, and even if the current detecting device is attached to the outer wall of the GIS tank near the Rogowski coil, it is not destroyed in the event of an accident. Another object of the present invention is to obtain a current detection device which can ensure withstand voltage without using an optical signal output cable and which is not affected even when the mounting location becomes far from the display device.

[0010]

A current measuring device of the present invention processes a Rogowski coil mounted inside a GIS tank having a center conductor so as to surround the center conductor, and an output of the Rogowski coil. A current measuring device having an electronic circuit, the current measuring device being connected to the outside by two external lines of an output line for sending an output signal from the electronic circuit and a power line for supplying power to the electronic circuit,
Sea said electronic circuitry mounted to said GIS tank
The power supply line of the electronic circuit, which is housed in a case, supplies an AC / DC power supply unit that supplies power, a high-voltage transformer that supplies AC to the AC / DC power unit, and AC power to the high-voltage transformer. DC /
An insulating line and an AC inverter, the output lines of the electronic circuit E for converting the output signal into an optical signal
/ O module and an optical cable for transmitting the optical signal
It is an insulated line equipped with .

In the GIS tank having the center conductor ,
A Rogowski coil attached to a portion so as to surround the central conductor, and an electronic circuit for processing the output of the Rogowski coil. Two external lines, an output line of the electronic circuit and a power line of the electronic circuit, are provided. A current measuring device connected to the outside, wherein the electronic circuit is housed in a shield case attached to the GIS tank, and the power supply line of the electronic circuit supplies AC / power to supply power.
DC power supply unit, high withstand voltage transformer for supplying alternating current to the AC / DC power supply unit and having signal winding, and DC / A for supplying alternating current power to the high withstand voltage transformer
An insulating line including a C inverter, wherein an output line of the electronic circuit converts the output signal into a serial signal and outputs the serial signal from the signal winding of the high voltage transformer to the AC power to output a serial signal. Department,
An insulating line having a filter circuit for extracting the superimposed serial signal from the AC power supplied by the DC / AC inverter.

The high withstand voltage transformer is a first high withstand voltage transformer that insulates the AC output of the DC / AC inverter, and the output of the first high withstand voltage transformer is converted into a voltage level required by the AC / DC power supply unit. A second winding having a signal winding connected to the serial signal output part
And a high withstand voltage transformer.

The high withstand voltage transformer insulates the alternating current output of the DC / AC inverter and has a first high withstand voltage transformer having a signal winding connected to the filter circuit.
And a second high withstand voltage transformer having a signal winding connected to the serial signal output unit while converting the output of the first high withstand voltage transformer to a voltage level required by the AC / DC power supply unit and supplying the voltage level. It is a thing.

The serial signal output section is connected to a high voltage transformer via a capacitor.

The frequency of the AC power output from the DC / AC inverter is selected to be 50 HZ or more, which is less than half the fundamental wave of the frequency component contained in the serial signal.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a block diagram showing a configuration of a current measuring device according to a first embodiment of the present invention. In the following description of each drawing, the same reference numerals as those in the drawings of the conventional example indicate the same or corresponding portions, and thus detailed description thereof will be omitted. In the figure, 31 is the center conductor of the GIS that is the current measurement target, 2 is the Rogowski coil installed inside the GIS tank so as to surround the center conductor 31 of the GIS, and 3 is the proper output of the Rogowski coil 2. An analog circuit (shown as “input adjustment” in the figure) that performs input adjustment for converting to voltage is an A / D converter that converts the output of the analog circuit 3 into digital data.

Reference numeral 5 is a microcomputer (also referred to as CPU) which controls the A / D converter 4 to calculate the result and sends data as an output signal, and 58 is a serial signal output section incorporated in the microcomputer 5. (The description of the serial signal output unit 58 is omitted in the drawings of the following embodiments). Reference numeral 6 is an E / O module for optically converting and transmitting the calculation result, and 61 is an optical transmission cable (output line) for the output signal optically output from the E / O module 6, which is naturally an insulating line. The analog circuit 3, the A / D converter 4, the microcomputer 5, and the serial signal output unit 5
8. The E / O module 6 is generically called an electronic circuit. 7
Is a display device including a printer or a display for displaying the calculation result of the CPU 5. 8 is an analog circuit 3
And a case for shielding the electronic circuits of the A / D converter 4, the CPU 5, and the E / O module 6 (referred to as a shield case).
U) , 9 is a power source 5 for supplying power to electronic circuits.
It is an inverter that converts 1 (DC) into sinusoidal single-phase or multi-phase AC.

Reference numeral 10 is a first high voltage transformer (hereinafter referred to as a first transformer) for insulating the AC output of the inverter 9, and 11 is an AC / D output voltage of the first transformer 10.
A second high voltage transformer (hereinafter referred to as a second transformer) for converting into a low voltage that is convenient for the operation of the C power supply unit 12, and 12 is a DC power supply for operating the electronic circuit of the second transformer 11. It is an AC / DC power supply unit for converting into. The line from the inverter 9 to the AC / DC power supply unit 12 is generically called a power supply line.
Reference numeral 13 denotes a GIS tank that accommodates the GIS central conductor 31, and a case 8 including an electronic circuit on the outside of the tank 13.
Is attached.

The description of the method for measuring the current value flowing through the central conductor 31 of the GIS tank 13 is the same as the conventional method. That is, the current detected by the Rogowski coil 2 passes through the analog circuit 3 and the A / D converter 4 housed in the case 8 attached to the outer wall of the GIS tank 13 to the CPU 5
Is calculated by. Calculated data is E / O module 6
Is converted into light and transmitted to the display device 7 at a distance from the GIS tank 13. The display device 7 performs O / E conversion on the received data, and then outputs it to a display or printer.

The power supply for the electronic circuit housed in the case 8 must be supplied from the DC power supply of the on-site power supply 51. The DC power is converted into a sine wave AC by the inverter 9, and insulation is taken by the first and second transformers 10 and 11, and then the voltage value at which the analog circuit 3 and other electronic circuits operate in the AC / DC power supply unit 12. Converted to and supplied. The power supply line is a high withstand voltage insulation line insulated with a high withstand voltage by the first and second transformers 10 and 11.

Next, the operation will be described. When a ground fault occurs, the potential of the GIS tank 13 is several K with respect to the ground.
V rises. Since the electronic circuit is capacitively coupled to the tank 13, the ground potential of the electronic circuit also rises by the same amount. As a result, the potential of the secondary side of the second transformer 11 (the side to which the AC / DC power supply unit 12 is connected) also rises by the same amount. On the other hand, since the potential on the primary side of the first power transformer 10 does not change at the ground level, the potential difference of several KV described above becomes the primary-secondary voltage between the first transformer 10 and the second transformer 11. It is distributed and shared. Since both the first transformer 10 and the second transformer 11 have high withstand voltage, no dielectric breakdown occurs and no abnormality occurs in the electronic circuit.

Embodiment 2. In the case of the configuration of the first embodiment shown in FIG. 1, since the output waveform of the inverter 9 is a sine wave,
When this is full-wave rectified, a capacitor is used to smooth the shaded area in Fig. 2. However, since the area of the shaded area is large, a capacitor with a large capacity must be used, and a chemical capacitor with a short life should be used. I can't help it. Therefore, in the second embodiment, the output waveform of the inverter 9 is a rectangular wave. When a rectangular wave is full-wave rectified by using the AC / DC converter 12, it is only necessary to smooth a narrow rectangular slanted line portion as shown in FIG. 3, so that a capacitor having a smaller capacity than that of a sine wave output is used. Will be enough.
In this case, a ceramic capacitor can be used.

Embodiment 3. The output of the inverter 9 may be polyphase alternating current. In this case, the first transformer 10, the second
All of the transformers 11 are polyphase transformers, AC / DC
It goes without saying that the power supply unit 12 is a polyphase rectifier. FIG. 4 shows a waveform obtained by full-wave rectifying a three-phase power source. In this case, the part to be smoothed is the shaded part, and the pulsating part (shaded part) is smaller than that in FIG. 2, so that there is an advantage that the capacity of the smoothing capacitor can be reduced as in the method described in the second embodiment. . It goes without saying that this effect can be further enhanced by increasing the number of phases to 4 and 5.

Fourth Embodiment The output frequency of the inverter 9 may be a high frequency. FIG. 5 shows a waveform obtained by full-wave rectifying a high frequency wave. Since the smoothed portion is smaller than the waveform shown in FIG. 2, there is an advantage that the capacity of the smoothing capacitor can be reduced as in the method described in the second embodiment. Further, by setting the output frequency to a high frequency, the first and second transformers 10 and 1
The effect that 1 can be miniaturized is also obtained.

Embodiment 5. If the transformer 10 is intended to have high withstand voltage insulation, the shape becomes large. A normal transformer is insulated in the air, but the insulation distance can be shortened by molding with an insulator. As a result, first,
The second transformers 10 and 11 can be downsized.

Sixth Embodiment FIG. 6 shows a block diagram of a current measuring device according to a sixth embodiment of the present invention. In the figure, 16 is a serial signal output by a serial signal output unit 58 incorporated in the CPU 5, 17 is a signal winding provided on the secondary side of the second transformer 11 and applying the serial signal 16, 1
Reference numeral 9 is a narrow band cutoff filter for removing the power supply voltage waveform from the output of the inverter 9 and extracting the serial signal 16.

Next, the operation will be described. The signal calculated by the CPU 5 and output as the serial signal 16 is superimposed on the AC power supply voltage from the signal winding 17 of the second transformer 11 and appears on the primary side of the first transformer 10. The power supply voltage waveform of the line 14 on the secondary side of the first isolation transformer 10 is shown in FIG. 7 (c). By the narrow band cutoff filter 19,
The signal of FIG. 7A is extracted from the waveform of FIG.
The narrow band cutoff filter 19 causes the power supply frequency (see FIG.
Only the power supply waveform of (b)) is blocked and input to the display 12 for display.

Even if a lightning current or a fault current at the time of a ground fault / short circuit flows in the GIS center conductor 31 and the GIS tank 12, and the potential of the electronic circuit portion including the A / D converter 4, the CPU 5, etc. to the ground rises. Since the second transformer 11 and the first transformer 10 have sufficient insulation performance, insulation breakdown does not occur, and each electronic circuit or display 12 is not destroyed.
It is easy to manufacture a transformer having a large dielectric strength and capable of passing the serial signal frequency, and since the E / O module 6 and the optical cable 61 are not used as in the first embodiment shown in FIG. In addition, high insulation can be realized at low cost.

In order to facilitate the signal separation by the narrow band cutoff filter 19, the output frequency of the inverter 9 is the fundamental wave of the frequency component including the serial signal (generally several KHZ).
Is less than 1/2 of that used in commercial frequency 50 HZ
It is preferable to use frequencies in the above range. The lower the frequency of the inverter 9, the easier the separation. However, the higher the frequency, the smaller the shapes of the first and second transformers.

Embodiment 7. FIG. 8 shows a block diagram of a current measuring device according to a seventh embodiment of the present invention. In the figure, 18 is a signal winding provided on the primary side of the first transformer 10. In the case of FIG. 6 of the sixth embodiment, it is necessary to use a separation circuit having a sufficient withstand voltage performance in order to separate the serial signal from the power supply voltage waveform, but in the case of FIG. Since only a low power supply voltage appears, the advantage is that high withstand voltage performance is not required.

Embodiment 8. FIG. 9 shows a block diagram of a current measuring device according to an eighth embodiment of the present invention. In the figure, 24 is a power supply winding on the secondary side of the second transformer 11 and a CPU.
A capacitor (which is an element for bypassing only the serial signal and is also called a high frequency bypass capacitor) inserted in the middle of the serial signal line 16 connecting the five. In the case of FIG. 6 of the sixth embodiment and in the case of FIG. 8 of the seventh embodiment, it is necessary to provide the signal winding in the transformer, which makes the transformer expensive, but in the case of FIG. 9, the signal winding is not used. The insulating transformer can be made simpler and cheaper. Since an overvoltage is not applied between both electrodes of the capacitor at the time of a GIS accident, a capacitor having a low withstand voltage performance is sufficient.

[0032]

According to the current measuring device of the present invention, one of two lines connected to the outside from the current measuring device is insulated by the optical signal, and the other one is insulated by the AC / DC power supply unit and the high voltage transformer. Therefore, even if it is stored in the case attached to the GIS, the effect that the dielectric breakdown does not occur due to the rise in the ground voltage at the time of the accident is obtained.

Further, the output line of the electronic circuit uses the output signal as a serial signal, and the output line is eliminated by superposing it on the power supply line, and the power supply line is insulated by the high voltage transformer, so that it is attached to the GIS. Even if it is stored in, the effect that dielectric breakdown does not occur due to the rise in the ground voltage at the time of an accident is obtained. Further, since there is no optical signal line, the device can be constructed at low cost.

Further, since the high withstand voltage transformer is composed of the first high withstand voltage transformer and the second high withstand voltage transformer having the signal winding, it is possible to obtain the effect that the superposed serial signals can be easily separated.

Further, since the first and second high withstand voltage transformers each have the signal winding, it is possible to obtain the effect that the superposed serial signals can be separated more easily.

Further, since the serial signal is injected into the transformer through the capacitor, there is an effect that the device can be constructed at low cost.

Further, since the frequency of the DC / AC inverter is set to ½ or less of the fundamental frequency of the serial signal and 50 HZ or more, it is possible to obtain the effect that the separation of the serial signal is easy.

[Brief description of drawings]

FIG. 1 is a block diagram of a current measuring device according to a first embodiment of the present invention.

FIG. 2 is an operation explanation waveform of the AC / DC power supply unit of the current measuring device of FIG.

FIG. 3 is a waveform diagram for explaining the operation of the AC / DC power supply unit according to the second embodiment.

FIG. 4 is a waveform diagram for explaining the operation of the AC / DC power supply unit according to the third embodiment.

FIG. 5 is an operation explanation waveform of the AC / DC power supply unit according to the fourth embodiment.

FIG. 6 is a block diagram of a current measuring device according to a sixth embodiment.

FIG. 7 is a waveform explaining the operation of FIG.

FIG. 8 is a block diagram of a current measuring device according to a seventh embodiment.

FIG. 9 is a block diagram of a current measuring device according to an eighth embodiment.

FIG. 10 is a block diagram of a conventional current measuring device.

[Explanation of symbols]

1 Current measurement target line, 2 Rogowski coil, 3
Analog circuit, 4 A / D converter, 5 microcomputer, 6 E / O module, 7 display device, 8 case, 9 inverter,
10 first high voltage transformer, 11 second high voltage transformer, 12 AC / DC power supply unit,
13 GIS tank, 31 center conductor, 51
On-site power supply, 58 serial signal output section, 61 optical cable (output line), 100 current measuring device

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumiaki Eura Inventor Fumiaki Eura 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (56) Reference JP-A-251251 (JP, A) JP-A-7 -140180 (JP, A) JP 52-49715 (JP, A) JP 62-75800 (JP, A) JP 10-300796 (JP, A) JP 63-201569 (JP, A) ) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01R 15/00-15/26 H02B 13/02-13/075 H01F 38/28

Claims (6)

(57) [Claims] 1. A GIS tank having a central conductor, comprising a Rogowski coil mounted so as to surround the central conductor, and an electronic circuit for processing the output of the Rogowski coil. a signal current measurement device connected to the outside by two external line of the power supply line for supplying a power supply and output lines to said electronic circuit for delivering, Sea said electronic circuit attached to the GIS tank
The power supply line of the electronic circuit, which is housed in a case, supplies an AC / DC power supply unit that supplies power, a high-voltage transformer that supplies AC to the AC / DC power unit, and AC power to the high-voltage transformer. DC /
An insulation line including an AC inverter, wherein the output line of the electronic circuit is an insulation line including an E / O module for converting the output signal into an optical signal and an optical cable for transmitting the optical signal. Current measuring device characterized by. 2. A GIS tank having a central conductor, comprising a Rogowski coil mounted so as to surround the central conductor, and an electronic circuit for processing the output of the Rogowski coil. a current measuring device connected to the outside by two external line of the power supply line of lines and the electronic circuit, Sea said electronic circuitry mounted to said GIS tank
The power supply line of the electronic circuit is housed in a field case, the AC / DC power supply unit that supplies power to the electronic circuit, a high withstand voltage transformer that supplies alternating current to the AC / DC power supply unit, and has a signal winding; An insulating line provided with a DC / AC inverter for supplying AC power to the withstand voltage transformer, wherein the output line of the electronic circuit converts the output signal into a serial signal, and the serial signal is converted into a serial signal with the high withstand voltage transformer. It is an insulated line that includes a serial signal output unit that superimposes on the AC power from a signal winding, and a filter circuit that extracts the superposed serial signal from the AC power supplied by the DC / AC inverter. Current measuring device. 3. The high voltage transformer is a first high voltage transformer that insulates the AC output of the DC / AC inverter, and the output of the first high voltage transformer is converted to a voltage level required by the AC / DC power supply unit. The current measuring device according to claim 2, further comprising a second high voltage transformer having a signal winding that is supplied to the serial signal output unit and is connected to the serial signal output unit. 4. The high withstand voltage transformer insulates the AC output of the DC / AC inverter, and the first high withstand voltage transformer having a signal winding connected to the filter circuit and the output of the first high withstand voltage transformer are AC. 3. A second high voltage transformer having a signal winding which is connected to the serial signal output unit while being supplied after being converted to a voltage level required by the / DC power supply unit. Current measuring device. 5. The current measuring device according to claim 2, wherein the serial signal output unit is connected to a high voltage transformer via a capacitor. 6. The frequency of the AC power output from the DC / AC inverter is selected to be 50 HZ or more, which is half the fundamental wave of the frequency component contained in the serial signal or less. The current measuring device described.