JP2003102125A - Ground fault detecting apparatus and ground fault detecting system in electric power system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground fault detecting apparatus and a ground fault detecting system in an electric power system, which can discriminate and detect ground faults on the power supply side and the load side in the electric power system, using an electric power conversion apparatus operated at different frequencies on the power supply side and the load side. SOLUTION: The ground fault detecting apparatus 1 comprises a ground detecting part 2, the first frequency ground fault discriminating part 3, a second frequency ground fault discriminating part 4, a first ground fault alarming part 5 and a second ground fault alarming part 6. The ground detecting part 2 converts a ground fault current flowing in a grounding conductor Le into a voltage and generates a ground fault detecting signal Ve. Since the first frequency ground fault discriminating part 3 discriminates and detects the ground fault in the first frequency electric power system, and the second frequency ground fault discriminating part 4 discriminates and detects the ground fault in the second frequency electric power system, the ground faults at two different frequencies in the electric power system are discriminated and detected by one ground fault detecting apparatus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention discriminates between a ground fault on the power source side and a ground fault on the load side in a power system using a power converter that operates at frequencies having different power source side frequencies and load side frequencies. The present invention relates to a ground fault detection device and a ground fault detection system in a power system.

[0002]

2. Description of the Related Art Conventionally, in a power system using a power converter that operates at frequencies different from each other on the power supply side and the load side, it is difficult to determine the frequency with a single ground fault detecting device. Therefore, the ground fault detection device is installed for each power system of each frequency, and the ground fault is detected for each power system of each frequency.

FIG. 7 is a schematic block diagram of a conventional ground fault detection device. In the figure, 40 is a ground fault detection device,
The ground fault detection unit 41, the ground fault determination unit 42, and the ground fault warning unit 43 are main components. The ground fault detection unit 41 detects the ground fault current flowing through the ground line Le by the ground fault detection winding 44 by electromagnetic coupling, and the current-voltage converter 45 converts the ground fault current into the ground fault detection signal Ve. The ground fault determination unit 42 includes a comparator 46 and a ground fault determination reference value generation circuit 47. The ground fault determination reference value generation circuit 47 obtains the ground fault determination reference value Vr by a resistor string connected to a predetermined power source. The comparator 46 compares the ground fault detection signal Ve with the ground fault determination reference value Vr, and the ground fault detection signal V
When e exceeds the ground fault judgment reference value Vr, the ground fault judgment signal S is output to the ground fault warning unit 43, and the ground fault warning unit 43 outputs the ground fault warning signal from the ground fault warning signal terminal Ar. .

FIG. 8 is a schematic system diagram of a ground fault detection system in a conventional power system. In the figure, the power system has an AC power supply 50, a power converter 51 (for example, an inverter device), and a load 52 as main components, and the AC power supply 50 supplies power to the power converter 51 via an input-side power line 53 to perform power conversion. The device 51 supplies AC power to the load 52 via the output power line 54. The AC power supply 50 is normally operated at the first frequency fp, and the power conversion device 51 converts AC of the first frequency fp into DC in the converter unit 55 and then converts DC into the first frequency fp in the inverter unit 56.
To a second frequency fs, which is a frequency different from. The converter unit 55 is configured by a full-wave rectification connection of a diode 57, and the inverter unit 56 is configured by a switching circuit connection of a transistor 58.
Incidentally, the diode 59 is for preventing the circulation.

In the power system shown in FIG. 8, since the input side (input side power line 53) and the output side (output side power line 54) of the power converter 51 are operated at different frequencies, a ground fault in the input side power line 53 occurs. (For example, the ground fault point is P
(In the case of a point), a ground fault current of the same frequency as the frequency on the input side flows, and a ground fault in the output power line 54 (for example, when the ground fault point is S point) occurs, the output side A ground fault current of the same frequency as the current flows. In order to discriminate between the ground fault in the input side power line 53 and the ground fault in the output side power line 54, the ground fault detection device 60p is connected to the ground line Le of the AC power supply 50, and the ground fault detection device 6 is connected to the output side power line 54.
0s are electromagnetically coupled and installed. That is, when a ground fault occurs in the input power line 53, the ground fault detection device 60p operates, and when a ground fault occurs in the output power line 54, the ground fault detection device 60p and the ground fault detection device 60.
Both s work. Due to this difference in operation, it is determined whether the ground fault position is the input side or the output side of the power conversion device 51.

As a method of detecting a ground fault in a power system using a power conversion device (for example, an inverter device) which is operated at a frequency where a power source side frequency and a load side frequency are different from each other, Japanese Patent Laid-Open No. 7-239359, Kaihei 5-328
739, Japanese Patent Laid-Open No. 5-328740, and Japanese Patent No. 3121570. JP-A-7-2393
59, JP-A-5-328739, JP-A-5
JP-A-328740 discloses a technique of detecting a ground fault on the output side of an inverter device. Japanese Patent No. 3121570 discloses a technique in which a circuit breaker close to the ground fault point is operated first by utilizing a difference in sensitivity of an earth leakage detector so that protection coordination is taken. Since it is not possible to determine whether the position is the input side or the output side of the inverter device, it is necessary to stop the device after the occurrence of the ground fault and determine the ground fault position by measuring the insulation resistance. That is, in any of the disclosed techniques, the ground fault position cannot be determined during the operation of the device, and the device must be stopped after the occurrence of the ground fault, and the ground fault position must be investigated and determined by measuring the insulation resistance.

[0007]

However, in the conventional ground fault detecting device, the frequency of the ground fault current cannot be discriminated, and in the power system of the frequency where the power source side and the load side of the power converter are different, Ground fault detectors are installed separately on both the power supply side and the load side, and each ground fault must be detected by a separate ground fault detector installed for each power system of each frequency. Therefore, there is a problem that the manufacturing cost becomes high.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power supply side ground fault and a load side ground fault in a power system having different frequencies on the power supply side and the load side of a power conversion device. An object is to provide a ground fault detection device capable of discriminating and detecting.

Another object of the present invention is to provide a ground in a power system capable of discriminating and detecting a power-side ground fault and a load-side ground fault in a power system having different frequencies on the power source side and the load side of the power converter. To provide a fault detection system.

[0010]

A ground fault detecting apparatus according to a first aspect of the present invention includes a ground fault detecting section for detecting a ground fault current and generating a ground fault detection signal, and a ground fault based on the ground fault detection signal. A ground fault detection device including a ground fault determination unit that determines the presence or absence of
The ground fault discriminating unit discriminates the presence or absence of a ground fault when the ground fault detecting signal has a first frequency, and the second frequency which the ground fault detecting signal differs from the first frequency. And a second frequency ground fault discriminating unit for discriminating the presence / absence of the ground fault.

In the ground fault detecting apparatus according to a second aspect of the present invention, in the first aspect, the first frequency ground fault discriminating section allows a ground fault detection signal of a first frequency to pass therethrough and outputs it as a first frequency ground fault signal. The first frequency filter circuit is compared with the first frequency ground fault signal and the first frequency ground fault determination reference value that is the ground fault determination reference value for the first frequency ground fault signal to output the first frequency ground fault determination signal. A second frequency ground fault discriminating unit, wherein the second frequency ground fault discriminating unit passes a ground fault detection signal having a second frequency and outputs the second frequency ground fault signal as a second frequency ground fault signal; A second frequency ground fault determination reference value that is a ground fault determination reference value for the second frequency ground fault signal and a second frequency ground fault determination signal that is output.
And a comparison unit.

A ground fault detection device according to a third aspect of the present invention is the ground fault detection device according to the second aspect, wherein the first frequency filter circuit is a bandpass filter circuit that passes a first frequency, and the second frequency filter circuit is a second frequency filter circuit. It is characterized in that it is a band pass filter circuit that passes a frequency or a band cut filter circuit that cuts off a first frequency.

A ground fault detecting apparatus according to a fourth aspect of the present invention is the second or third aspect of the invention, wherein the first comparing section receives the first frequency ground fault signal and the first frequency ground fault determination reference value as inputs. 1 comparator and a first frequency ground fault determination reference value generating first
A frequency ground fault determination reference value generating circuit, wherein the second comparison unit inputs a second frequency ground fault signal and a second frequency ground fault determination reference value, and a second frequency ground fault determination And a second frequency ground fault determination reference value generating circuit for generating a reference value.

A ground fault detection apparatus according to a fifth aspect of the present invention is the ground fault detection apparatus according to any one of the first to fourth aspects of the present invention, based on the determination results of the first frequency ground fault determination section and the second frequency ground fault determination section. It is characterized by having a ground fault alarm unit for outputting an alarm.

A ground fault detection apparatus according to a sixth aspect of the present invention is the ground fault detection unit according to the fifth aspect, wherein the ground fault alarm unit outputs a ground fault alarm based on the determination result of the first frequency ground fault determination unit. An alarm unit and a second ground fault alarm unit that outputs a ground fault alarm based on the determination result of the second frequency ground fault determination unit are provided.

A ground fault detecting device according to a seventh aspect of the present invention is characterized in that, in any one of the first to sixth aspects of the invention, the second frequency is variably controlled.

A ground fault detection system in an electric power system according to an eighth aspect of the present invention is an AC power supply of a first frequency, a ground line derived from the AC power supply, and the AC power supply connected via an input side power line. In a ground fault detection system in a power system including an electric power converter that supplies AC power of a second frequency different from the frequency to a load via an output power line, a ground fault in the input power line of the first frequency and a second The ground line is provided with a ground fault detection device for discriminating and detecting a ground fault in the power line on the output side of the frequency.

A ground fault detection system in a power system according to a ninth aspect of the present invention is the ground fault detection device according to the eighth aspect of the present invention.
First to determine a ground fault in the input side power line of the first frequency
A frequency ground fault discriminating unit and a second frequency ground fault discriminating unit for discriminating a ground fault in the output power line of the second frequency are provided.

A ground fault detection system in a power system according to a tenth aspect of the invention is characterized in that, in the eighth aspect or the ninth aspect, the ground line is derived from a neutral point of the AC power source.

An earth fault detection system in a power system according to an eleventh invention is characterized in that, in the eighth invention through the tenth invention, the second frequency is variably controlled.

In the first invention, the ground fault detection signal is the first
A first frequency ground fault discriminating unit for discriminating the presence / absence of a ground fault at a frequency, and a second frequency ground fault discriminating for discriminating the presence / absence of a ground fault at a second frequency where the ground fault detection signal is different from the first frequency. Since the ground fault detection device is configured to include a section, it is possible to provide a ground fault detection device capable of determining and detecting a ground fault system in a power system of two different frequencies with a single ground fault detection device. Becomes

In the second aspect of the invention, the first frequency ground fault discriminating unit is provided with the first frequency filter circuit, and the second frequency ground fault discriminating unit is provided with the second frequency filter circuit. Thus, it becomes possible to provide a ground fault detection device capable of surely determining the frequency and detecting the ground fault.

In the third invention, the first frequency filter circuit is a band-pass filter circuit that passes the first frequency, and the second frequency filter circuit is a band-pass filter circuit that passes the second frequency or the first frequency. Since the band cutoff filter circuit that cuts off is used, the filter circuit configuration is simplified, and it is possible to provide an inexpensive ground fault detection device that can reliably determine the frequency.

In the fourth aspect of the invention, the first comparing portion is the first
A frequency ground fault determination reference value generation circuit is provided in the second comparison unit.
Since the configuration is provided with the frequency ground fault determination reference value generation circuit, it becomes easy to set the ground fault determination reference value, and it is possible to provide the ground fault detection device that can reliably determine the frequency.

According to the fifth aspect of the invention, the ground fault alarm unit is provided which outputs the ground fault alarm based on the discrimination results of the first frequency ground fault discrimination unit and the second frequency ground fault discrimination unit. It is possible to provide a ground fault detection device having a simple structure and capable of performing a reliable ground fault warning.

In the sixth aspect of the invention, since the ground fault alarm unit is composed of two ground fault alarm units that operate according to each frequency, the alarm can be easily identified and the alarm can be reliably identified. It becomes possible to provide a ground fault detection device.

According to the seventh aspect of the invention, since the second frequency is variably controlled, a ground fault detection system in a power system for controlling the second frequency using a frequency conversion type power conversion device such as an inverter device is used. It is possible to provide an applicable ground fault detection device.

In the eighth aspect of the present invention, in the ground fault detection system in the electric power system, the ground fault detecting device for discriminating and detecting the ground fault in the input side power line of the first frequency and the ground fault in the output side power line of the second frequency. Since the above is provided in the ground line, it is possible to provide an inexpensive and reliable ground fault detection system in a power system.

According to a ninth aspect of the present invention, in the ground fault detection system in the electric power system, the first frequency ground fault discriminator and the second frequency ground fault discriminator are provided.
Since the configuration is provided with the frequency ground fault discriminating unit, it is possible to surely discriminate the ground fault frequency, and it is possible to provide an inexpensive and reliable ground fault detection system in a power system.

In the tenth aspect of the invention, since the ground wire is derived from the neutral point of the AC power source, the ground fault can be reliably discriminated, and the inexpensive and reliable ground fault detection system in the power system can be provided. It will be possible.

In the eleventh aspect of the invention, the second frequency is variably controlled, so that the second frequency is controlled even in the power system that controls the second frequency by using the power conversion device of the frequency conversion system such as the inverter device. It is possible to provide a ground fault detection system in an electric power system capable of surely detecting the ground fault according to the frequency control situation.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. <Embodiment 1> FIG.
It is a block diagram of the ground fault detection apparatus which concerns on Embodiment 1 of this invention. In the figure, reference numeral 1 is a ground fault detection device, which is a ground fault detection unit 2, a first frequency ground fault determination unit 3, a second frequency ground fault determination unit 4, a first ground fault warning unit 5, and a second ground fault warning. It is composed of the unit 6. The ground fault detection unit 2 is, for example, a ground fault detection winding 7 that is electromagnetically coupled to the ground line Le to detect a ground fault current flowing in the ground line Le, and a ground fault current detected by the ground fault detection winding 7 as a voltage. And a current-voltage converter 8 that generates a ground fault detection signal Ve. The first frequency ground fault discriminating unit 3 and the second frequency ground fault discriminating unit 4 form a ground fault discriminating unit of the ground fault detecting device 1. Here, the first frequency fp and the second frequency fs are different from each other, and the first frequency fp is, for example, a frequency on the AC power supply side, and is usually 50 Hz or 60 Hz.
The second frequency fs is a frequency on the load side of the power converter, for example, 15 to 40 Hz. The first frequency ground fault discriminating unit 3 discriminates and detects a ground fault in the first frequency power system, and the second frequency ground fault discriminating unit 4 discriminates and detects a ground fault in the second frequency power system. Due to
A single ground fault detection device can discriminate and detect a ground fault in a power system of two different frequencies.

The first frequency ground fault discriminating section 3 comprises a first frequency filter circuit 9, a first comparator 10, and a first frequency ground fault discriminating reference value generating circuit 11. First comparator 10
The first frequency ground fault determination reference value generation circuit 11 constitutes a first comparison section. The ground fault detection signal Ve is input to the first frequency filter circuit 9. The first frequency filter circuit 9 is, for example, a bandpass filter circuit having the first frequency fp as the center frequency, and only when the frequency of the ground fault detection signal Ve has the first frequency fp as the center frequency, the ground fault detection signal Output Ve as the first frequency ground fault signal Vfp,
If the ground fault detection signal Ve has another frequency, it is cut off.
The first frequency ground fault determination reference value generation circuit 11 generates a first frequency ground fault determination reference value Vp by appropriately dividing a resistor string connected to a predetermined power source. The first comparator 10 includes a first frequency ground fault signal Vfp and a first frequency ground fault determination reference value V.
When the first frequency ground fault signal Vfp is greater than or equal to the first frequency ground fault determination reference value Vp by comparing with p, the first frequency ground fault determination signal S1 is output to the first ground fault alarm unit 5. input. The first ground fault alarm unit 5 receives the first frequency ground fault determination signal S1.
In response, the first ground fault alarm signal terminal Ar1 outputs a proper alarm. The alarm may be in a form that can be perceived visually or aurally, or in the form of an operation signal that operates another control device, for example. First frequency ground fault discrimination signal S1
Can be, for example, a digital signal of "1,0".

The second frequency ground fault discriminating section 4 comprises a second frequency filter circuit 12, a second comparator 13, and a second frequency ground fault discriminating reference value generating circuit 14. Second comparator 1
The third and second frequency ground fault determination reference value generating circuit 14 constitutes a second comparing section. In the second frequency filter circuit 12,
The ground fault detection signal Ve is input. The second frequency filter circuit 12 is, for example, a bandpass filter circuit having the second frequency fs as a center frequency, and only when the frequency of the ground fault detection signal Ve is the second frequency fs, the ground fault detection signal Ve.
Is output as the second frequency ground fault signal Vfs, and is cut off when the ground fault detection signal Ve has another frequency. The second frequency ground fault determination reference value generation circuit 14 generates the second frequency ground fault determination reference value Vs by appropriately dividing a resistor string connected to a predetermined power source. The second comparator 13 compares the second frequency ground fault signal Vfs with the second frequency ground fault determination reference value Vs, and the second frequency ground fault signal Vfs is greater than or equal to the second frequency ground fault determination reference value Vs. In this case, the second frequency ground fault determination signal S2 is output and input to the second ground fault alarm unit 6. The second ground fault alarm unit 6 receives the second frequency ground fault determination signal S2 and then receives the second frequency ground fault determination signal S2.
An alarm is appropriately output from the ground fault alarm signal terminal Ar2. The alarm may be in a form that can be perceived visually or aurally, or in the form of an operation signal that operates another control device, for example. The second frequency ground fault determination signal S2 can be, for example, a digital signal of "1, 0", like the first frequency ground fault determination signal S1.

The first frequency filter circuit 9 and the second frequency filter circuit 12 are not limited to band pass filter circuits, but may be band stop filter circuits. For example, if the first frequency filter circuit 9 is a band pass filter circuit that allows the first frequency fp to pass, and the second frequency filter circuit 12 is a band stop filter circuit that blocks the first frequency fp, the configuration of the filter circuit is simple. Therefore, the cost can be reduced. Normally, the filter circuit is composed of a CR circuit, but not limited to this, the first frequency fp
And a second frequency fs can be separated as long as a predetermined frequency characteristic can be obtained. In the first frequency ground fault discriminating unit 3, the first frequency filter circuit 9 is used, and in the second frequency ground fault discriminating unit 4, the second frequency filter circuit 12 is used to detect the ground fault detection signal Ve at the first frequency fp and the second frequency. Since the ground fault detection signal Ve at the frequency fs is determined,
The frequency of the ground fault detection signal Ve can be reliably discriminated by a simple configuration in which two filter circuits each having a different predetermined frequency characteristic are added, and the ground fault location can be easily identified according to the frequency, and the stability can be improved. It is possible to realize a high ground fault detection device. The filter circuit is usually configured to include a CR circuit, but the present invention is not limited to this.

In FIG. 1, the first ground fault alarm unit 5 and the second ground fault alarm unit 6 are configured separately, but the first frequency ground fault determination signal S1 and the second frequency ground fault determination signal S2 are input. It may be a single ground fault alarm unit. In this case, the output form may be two output terminals (corresponding to the first ground fault warning signal terminal Ar1 and the second ground fault warning signal terminal Ar2).
The output form is changed as a terminal (for example, a high-pitched alarm sound for the first frequency ground fault discrimination signal S1 and a low-pitched alarm sound for the second frequency ground fault discrimination signal S2. , A red alarm display color may be used for the first frequency ground fault discrimination signal S1, and an orange alarm display color may be used for the second frequency ground fault discrimination signal S2. If a single ground fault alarm unit is used, the structure of the ground fault alarm unit can be simplified. or,
When the first ground fault alarm unit 5 and the second ground fault alarm unit 6 and the two ground fault alarm units are used, it is possible to easily identify the alarm and obtain a ground fault detection device that can reliably identify the alarm.

<Second Embodiment> FIG. 2 is a system diagram of a ground fault detection system in a power system according to a second embodiment of the present invention. In the figure, an AC power supply 20 and a power converter 2
1 and the load 22 are mutually connected by the input side electric power line 23 and the output side electric power line 24, respectively. The AC power supply 20 is, for example, a commercial AC power supply, and is operated at a first frequency fp, for example, 50 Hz or 60 Hz. The power conversion device 21 is, for example, an inverter device, and after converting the alternating current of the first frequency fp into the direct current in the converter part 25, the direct current is converted into the first frequency fp in the inverter part 26.
The second frequency fs, which is a different frequency from the above, is converted into alternating current, and alternating current power is supplied to the load 22. Second frequency fs
Is appropriately set according to the load demand, and is, for example, 15 to 40 Hz. The converter section 25 is configured by full-wave rectification connection of the diode 27 (here, composed of six diodes 27), and the inverter section 26 is configured by switching circuit connection of the transistor 28 (constituted by six transistors 28 here). Composed. A diode 29 connected in parallel between the collector and the emitter of the transistor 28 is a feedback diode for processing regenerative energy and reactive power. It goes without saying that the power conversion device 21 may be, for example, a cycloconverter or the like other than the inverter device.

When a ground fault occurs in the input power line 23 (for example, when the ground fault point is point P), the first frequency fp
When the ground fault current flows in the output side power line 24 (for example, the ground fault point is the point S), the ground fault current of the second frequency fs flows. In order to discriminate between the ground fault in the input side power line 23 and the ground fault in the output side power line 24, the ground fault detection device 1 is electromagnetically coupled to the ground line Le of the AC power supply 20 and installed. The ground fault detection device 1 is the one disclosed in FIG. 1, and a detailed description thereof will be omitted. Ground fault detection device 1
Even when the power system is operating, the frequency of the ground fault current flowing through the ground line Le is determined to determine the ground fault of the first frequency fp and the ground fault of the second frequency fs. The contact detection system can be simplified, resulting in low cost and space saving. Furthermore, since the ground fault detection device 1 includes the first frequency ground fault determination unit 3 and the second frequency ground fault determination unit 4, the ground fault of the first frequency fp and the ground fault of the second frequency fs are combined into one unit. The ground fault detection device 1 can be surely discriminated, the ground fault detection system in the power system can be simplified, and the cost and the space can be reduced.

When the power conversion device 21 is an inverter device, the frequency range between the first frequency fp and the second frequency fs is clear, and it is possible to provide a ground fault detection system that operates more reliably. . Since the AC power supply 20 normally adopts the neutral point grounding system, the ground fault detection device 1 is provided on the ground line Le derived from the neutral point of the AC power supply 20, but the grounding system is particularly limited to the neutral point grounding system. Not a thing.

FIG. 3 is a graph showing the frequency characteristics of the filter circuit in the ground fault detection apparatus according to the first embodiment of the present invention. In the figure, the horizontal axis represents frequency (Hz) and the vertical axis represents the filter output signal level. First in FIG.
The first frequency ground fault signal Vfp, which is the output of the frequency filter circuit 9, is shown by the solid line waveform centered around the first frequency fp, and the second frequency ground fault signal Vfs, which is the output of the second frequency filter circuit 12, is , And is indicated by a broken-line waveform centered on the second frequency fs. It can be said that the steeper the waveform is, the better the detection characteristic is, but any characteristic can be used as long as it can distinguish between the first frequency fp and the second frequency fs, which are fundamental frequencies.

FIG. 4 is an operation explanatory graph of the comparator in the ground fault detection apparatus according to the first embodiment of the present invention. In the figure, the horizontal axis represents time T (unit is arbitrary) and the vertical axis represents each signal level (unit is arbitrary), and the first comparator 10 in FIG.
The operation of the second comparator 13 will be described. FIG. 4A is an operation explanatory graph of the first comparator 10, in which the vertical axis represents the magnitude of the first frequency ground fault signal Vfp which is the input of the first comparator 10, and at the time T1, A situation in which a ground fault occurs at one frequency fp, and the first frequency ground fault signal Vfp increases accordingly, and the first frequency ground fault determination reference value Vp, which is another input of the first comparator 10, becomes greater than or equal to Show. Figure 4 (b)
Shows the situation of the first frequency ground fault discrimination signal S1 which is the output of the first comparator 10. When the first frequency ground fault signal Vfp in the first comparator 10 becomes larger than the first frequency ground fault determination reference value Vp, the output of the first comparator 10 changes from the ground fault detection OFF state to the ground fault detection state. It is turned on. That is, the first frequency ground fault determination signal S1 is the time T1.
In digital terms, "0" to "1"
The ground fault at the first frequency fp can be discriminated and detected.

FIG. 4C is a graph for explaining the operation of the second comparator 13, in which the vertical axis represents the magnitude of the second frequency ground fault signal Vfs which is the input of the second comparator 13, and the time T2.
At the time of, a ground fault occurs at the second frequency fs, and the second frequency ground fault signal Vfs increases accordingly, and the second comparator 13
2 shows a situation in which the second frequency ground fault determination reference value Vs, which is another input of, has become equal to or higher than the reference value Vs. FIG. 4D shows the state of the second frequency ground fault discrimination signal S2 which is the output of the second comparator 13. In the second comparator 13, the second frequency ground fault signal Vfs is
When it becomes larger than the frequency ground fault determination reference value Vs, the output of the second comparator 13 changes from the state of ground fault detection OFF (OFF) to
The ground fault detection is turned on. That is, the second frequency ground fault determination signal S2 changes from “0” to “1” when expressed digitally at time T2, and the second frequency f
The ground fault at s can be discriminated and detected. The first
The ground fault detection sensitivity can be adjusted by appropriately adjusting the values of the frequency ground fault determination reference value Vp and the second frequency ground fault determination reference value Vs.

<Third Embodiment> FIG. 5 is a system diagram of a ground fault detection system in a power system according to a third embodiment of the present invention. Using the inverter frequency control device 30 that is normally used in the ground fault detection system in the electric power system according to the second embodiment of the present invention shown in FIG. 2, a ground fault detection system capable of more efficient control is configured. Since the basic configuration is the same as that shown in FIGS. 1 and 2, detailed description of the same parts will be omitted. An inverter frequency control signal 30 a is supplied from the inverter frequency control device 30 for controlling the frequency of the inverter unit 26 to the inverter unit 26. Specifically, transistor 28
The frequency is controlled by on / off controlling the base current of. The frequency of the alternating current supplied from the inverter unit 26 to the load 22 is appropriately variably adjusted according to the load condition (request), and the second frequency fs, which is the frequency of the output side power line 24, is the inverter unit according to the inverter frequency control signal 30a. It is variably adjusted according to the control status of 26.

Therefore, the frequency characteristic of the second frequency ground fault discriminating section 4 for discriminating the ground fault at the second frequency fs is also adjusted appropriately according to the fluctuation of the second frequency fs. That is, the second frequency ground fault discrimination control signal 30b for controlling the frequency characteristic of the second frequency ground fault discrimination unit 4 is output from the inverter frequency control device 30 to the second frequency ground fault discrimination unit 4 of the ground fault detection device 1. The second frequency filter circuit 1 shown in FIG. 1 is supplied after being matched with the frequency control signal 30a.
The frequency characteristic of 2 is controlled.

FIG. 6 is a graph showing the frequency characteristic of the filter circuit in the ground fault detection device of the ground fault detection system in the electric power system according to the third embodiment of the present invention. In the figure, the horizontal axis represents frequency (Hz) and the vertical axis represents the filter output signal level. The output (Vfp) of the first frequency filter circuit 9 in FIG. 1 is shown by a solid line waveform centered on the first frequency fp, and the second frequency filter circuit 12
Output (Vfs) is shown by a solid line waveform centered on the second frequency fs. Here, the second frequency fs is f
The change situation of the output (Vfs) of the 2nd frequency filter circuit 12 at the time of being variably adjusted between sl and fsh (for example, 0-60Hz) is shown. That is, in accordance with the variable adjustment of the second frequency fs by the inverter frequency control signal 30a, the second frequency ground fault determination control signal 30b is used to change the second frequency fs.
By adjusting the pass center frequency of the band pass frequency characteristic of the frequency filter circuit 12, the output (Vfs) of the second frequency filter circuit 12 is represented by a broken line centered around the second frequency fsl and the second frequency fsh. Variable adjustment is performed according to the second frequency fs between the frequency characteristics shown by the broken line as the center. In this way, by controlling the frequency characteristic of the second frequency filter circuit 12 in conjunction with the frequency control of the inverter frequency control device 30, it is possible to reliably determine the ground fault that is not affected by the fluctuation of the second frequency fs. Becomes

[0046]

As described in detail above, according to the first aspect of the invention, the ground fault detecting device is configured to include the first frequency ground fault discriminating section and the second frequency ground fault discriminating section. It is possible to provide a ground fault detection device capable of discriminating and detecting a ground fault system in a power system operated by two different frequencies with a single ground fault detection device.

According to the second aspect of the invention, the first frequency ground fault discriminating unit is provided with the first frequency filter circuit, and the second frequency ground fault discriminating unit is provided with the second frequency filter circuit. With such a configuration, it is possible to provide a ground fault detection device that can reliably determine a frequency and detect a ground fault.

In the third invention, the first frequency filter circuit is a band-pass filter circuit that passes the first frequency, and the second frequency filter circuit is the band-pass filter circuit or the first frequency filter that passes the second frequency. Since the band cutoff filter circuit that cuts off the frequency is used, the filter circuit configuration is simplified, and it is possible to provide an inexpensive ground fault detection device that can reliably determine the frequency.

According to the fourth aspect of the invention, the first comparing section has the first
A frequency ground fault determination reference value generation circuit is provided in the second comparison unit.
Since the configuration is provided with the frequency ground fault determination reference value generation circuit, it becomes easy to set the ground fault determination reference value, and it is possible to provide the ground fault detection device that can reliably determine the frequency.

According to the fifth aspect of the present invention, the ground fault alarm unit for outputting the ground fault alarm based on the discrimination results of the first frequency ground fault discrimination unit and the second frequency ground fault discrimination unit is provided. It is possible to provide a ground fault detection device that has a simple configuration of the ground fault alarm unit and can perform a reliable ground fault alarm.

In the sixth aspect of the invention, since the ground fault alarm unit is composed of two ground fault alarm units that operate according to each frequency, the alarm can be easily identified and the alarm can be reliably identified. It is possible to provide a ground fault detection device capable of performing the above.

According to the seventh aspect of the invention, since the second frequency is variably controlled, the ground fault detection in the power system for controlling the second frequency by using the power conversion device of the frequency conversion system such as the inverter device is performed. It is possible to provide a ground fault detection device applicable to the system.

In the eighth aspect of the present invention, in the ground fault detection system in the electric power system, the ground fault is detected by discriminating between the ground fault in the input side power line of the first frequency and the ground fault in the output side power line of the second frequency. Since the detection device is provided in the ground line, it is possible to provide an inexpensive and reliable ground fault detection system in a power system.

According to the ninth invention, in the ground fault detection system in the electric power system, the first frequency ground fault discriminator and the second frequency ground fault discriminator are provided.
Since the configuration is provided with the frequency ground fault discriminating unit, it is possible to surely discriminate the ground fault frequency, and it is possible to provide an inexpensive and reliable ground fault detection system in a power system.

According to the tenth aspect of the invention, since the ground line is constructed so as to be derived from the neutral point of the AC power source, the ground fault can be reliably discriminated, and the ground fault detection system in the electric power system is inexpensive and reliable. It becomes possible to provide.

In the eleventh aspect of the invention, since the second frequency is variably controlled, the second frequency can be controlled by using the frequency conversion type power converter such as an inverter. It is possible to provide a ground fault detection system in an electric power system capable of performing reliable ground fault detection according to the frequency control status of two frequencies.

[Brief description of drawings]

FIG. 1 is a block diagram of a ground fault detection device according to a first embodiment of the present invention.

FIG. 2 is a system diagram of a ground fault detection system in a power system according to a second embodiment of the present invention.

FIG. 3 is a graph showing frequency characteristics of a filter circuit in the ground fault detection device according to the first embodiment of the present invention.

FIG. 4 is an operation explanatory graph of a comparator in the ground fault detection device according to the first embodiment of the present invention.

FIG. 5 is a system diagram of a ground fault detection system in a power system according to a third embodiment of the present invention.

FIG. 6 is a graph showing frequency characteristics of a filter circuit in the ground fault detection device of the ground fault detection system in the electric power system according to the third embodiment of the present invention.

FIG. 7 is a schematic block diagram of a conventional ground fault detection device.

FIG. 8 is a schematic system diagram of a ground fault detection system in a conventional power system.

[Explanation of symbols]

1 Ground fault detector 2 Ground fault detector 3 First frequency ground fault discriminator 4 Second frequency ground fault discriminator 5 First ground fault alarm section 6 Second ground fault alarm section 9 First frequency filter circuit 10 First comparator 11 First Frequency Ground Fault Judgment Reference Value Generation Circuit 12 Second frequency filter circuit 13 Second comparator 14 Second frequency ground fault determination reference value generation circuit 20 AC power supply 21 Power Converter 22 load 23 Input side power line 24 Output power line 30 Inverter frequency controller Le ground wire Ve Ground fault detection signal Vfp first frequency ground fault signal Vp 1st frequency ground fault judgment reference value Vfs 2nd frequency ground fault signal Vs 2nd frequency ground fault judgment reference value S1 First frequency ground fault discrimination signal S2 Second frequency ground fault discrimination signal

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daisuke Izu             Fukuoka Prefecture Kitakyushu City Kokurakita-ku, Konomi-cho 1-share             Ceremony Company Sumitomo Metal Kokurauchi (72) Inventor Atsushi Tanaka             Fukuoka Prefecture Kitakyushu City Kokurakita-ku, Konomi-cho 1-share             Ceremony Company Sumitomo Metal Kokurauchi (72) Inventor Tetsuya Sukuguchi             Fukuoka Prefecture Kitakyushu City Kokurakita-ku, Konomi-cho 1-share             Ceremony Company Sumitomo Metal Kokurauchi F-term (reference) 2G014 AA04 AB02 AC18                 5G053 AA06 BA01 DA01 EB06 EC03                       FA01                 5G058 BB02 BC16 CC02                 5H007 AA06 AA12 CA01 CB02 CC01                       CC09 DB02 DC02 FA03

Claims (11)

[Claims] 1. A ground fault detection unit including a ground fault detection unit that detects a ground fault current and generates a ground fault detection signal, and a ground fault determination unit that determines the presence or absence of a ground fault based on the ground fault detection signal. In the device, the ground fault discriminating unit discriminates whether there is a ground fault when the ground fault detecting signal has a first frequency, and the ground fault detecting signal has a first frequency. A second frequency ground fault discriminating unit that discriminates the presence / absence of a ground fault at different second frequencies. 2. The first frequency ground fault discriminator passes a ground fault detection signal of a first frequency and outputs a first frequency ground fault signal, a first frequency ground fault signal, and a first frequency ground fault signal. The first frequency ground fault determination reference value that is a ground fault determination reference value for the first frequency ground fault signal, and outputs a first frequency ground fault determination signal.
The frequency ground fault discriminating unit passes a ground fault detection signal of the second frequency and outputs it as a second frequency ground fault signal, and a ground for the second frequency ground fault signal and the second frequency ground fault signal. The ground fault detection according to claim 1, further comprising: a second comparison unit that compares a second frequency ground fault determination reference value that is a fault determination reference value and outputs a second frequency ground fault determination signal. apparatus. 3. The first frequency filter circuit comprises:
3. A band pass filter circuit that passes a frequency, wherein the second frequency filter circuit is a band pass filter circuit that passes a second frequency or a band stop filter circuit that cuts off a first frequency.
The ground fault detection device described in 1. 4. The first comparing unit receives a first frequency ground fault signal and a first frequency ground fault determination reference value as inputs, and generates a first frequency ground fault determination reference value. A frequency ground fault determination reference value generating circuit, wherein the second comparison unit inputs a second frequency ground fault signal and a second frequency ground fault determination reference value, and a second frequency ground fault determination The ground fault detection device according to claim 2, further comprising a second frequency ground fault determination reference value generation circuit that generates a reference value. 5. A ground fault alarm unit for outputting a ground fault alarm based on the discrimination results of the first frequency ground fault discrimination unit and the second frequency ground fault discrimination unit. The ground fault detection device described in 1. 6. The ground fault alarming unit discriminates between a first ground fault alarming unit that outputs a ground fault alarm based on the discrimination result of the first frequency ground fault discriminating unit and the second frequency ground fault discriminating unit. The ground fault detection device according to claim 5, further comprising a second ground fault alarm unit that outputs a ground fault alarm based on a result. 7. The ground fault detection device according to claim 1, wherein the second frequency is variably controlled. 8. An AC power supply of a first frequency, a ground wire derived from the AC power supply, and an AC power of a second frequency different from the first frequency, which is connected to the AC power supply via an input side power line. In a ground fault detection system in a power system including a power conversion device that supplies power to a load via a side power line, a ground fault in an input side power line of a first frequency and a ground fault in an output side power line of a second frequency are distinguished. A ground fault detection system in a power system, wherein the ground line is provided with a ground fault detection device that detects the ground fault. 9. The ground fault detection device comprises: a first frequency ground fault discriminator that discriminates a ground fault in an input side power line of a first frequency; and a second frequency discriminates a ground fault in an output side power line of a second frequency. The ground fault detection system in a power system according to claim 8, further comprising a ground fault determination unit. 10. The ground fault detection system in a power system according to claim 8, wherein the ground line is derived from a neutral point of the AC power source. 11. The ground fault detection system in a power system according to claim 8, wherein the second frequency is variably controlled.