JPH08306297A - Earth leakage breaker - Google Patents

Abstract

PURPOSE: To avoid the phenomenon that an earth leakage breaker is easily operated by the high frequency leakage current, and to grasp the tolerance to the operation level. CONSTITUTION: A frequency changing means 21 (low pass filters 14, 15, 16 and a first changeover switch 17), which can change the frequency characteristic of a leakage detecting means 20, is provided so as to change the frequency characteristic and raise the sensitive current at a high frequency when an earth leakage breaker is operated by the high frequency zero-phase current by a load such as an inverter. A second leakage detecting means 28 is provided, and the leakage detecting level is changed by a leakage judging level changing means 26, and when the output signal of the second leakage detecting means 28 is generated in response to the change of the leakage detecting level, a display means 27 displays it, and largeness of the real leakage current is discriminated on the basis of the display of the display means 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage breaker for controlling the opening / closing of a main circuit based on a zero phase detection signal from a zero phase current transformer.

[0002]

2. Description of the Related Art The circuit configuration of a conventional earth leakage breaker is shown in FIG. Generally, an earth leakage circuit breaker is provided with a main contact 1 for opening and closing the main circuit 1 for supplying electric power to a load such as an electric motor, and the three-phase conductors that constitute the main circuit 1 are used as a group of primary conductors. A zero-phase current transformer 3 for detecting a phase current is provided, and a leakage detection means 4 for receiving a detection signal of the zero-phase current from the zero-phase current transformer 3 and performing a logical operation for determining the presence or absence of leakage, and A trip device 5 for opening the main contact 2 by a trip signal from the earth leakage detection means 4 is provided. When an electric leakage current occurs in a load or a load power feeding path, the main circuit 1 is operated by the main contact 2 described above. It is opened promptly and has a function of protecting the load or the line. In addition, FIG. 5 also shows a power supply circuit 6 for generating power supplied to the leakage detection means 4 and the trip device 5.

[0003]

In recent years, the load of inverters and the like has increased rapidly, and high-frequency leakage current has begun to flow. As shown in FIG. 6, the conventional earth leakage breaker generally has a characteristic such that the sensitivity current becomes higher as the frequency becomes higher, which makes it difficult to operate with the high frequency leakage current. However, there is a problem that it operates depending on the carrier frequency of the inverter and the length of the wiring cable.

Even when the earth leakage breaker does not operate, the magnitude of the high-frequency earth leakage current that is actually flowing is not known, so it is not possible to know how much margin the operation level has. For this reason, there is a problem in that the one having a low tolerance operates easily when actually installed.
Furthermore, when the earth leakage breaker operates, it is indistinguishable from whether it was operated by a high frequency leakage current or by a commercial frequency leakage current due to the occurrence of an actual ground fault. It was

The present invention has been made in view of the above circumstances, and therefore an object thereof is to provide an earth leakage breaker that is more difficult to operate against a high frequency earth leakage current, and, at the same time, to provide a wide range of operation levels. Another object is to provide an earth leakage breaker capable of grasping the degree of leakage and an earth leakage breaker capable of discriminating the frequency of an earth leakage current when the earth leakage breaker operates.

[0006]

To achieve the above object, in an earth leakage circuit breaker of the present invention, a main contact interposed in a main circuit for supplying electric power to a load and a zero phase provided in the main circuit. A current transformer, a leakage detection means for detecting the presence or absence of leakage on the basis of a zero-phase detection signal from this zero-phase current transformer, and a trip device for opening the main contact by a trip signal from this leakage detection means. And a frequency changing means for changing the frequency characteristic of the leakage detecting means.

In this case, the frequency varying means has a plurality of low-pass filters having different attenuation characteristics or low-pass filters having different cut-off frequencies, and each of the low-pass filters may be selected.

In the earth leakage circuit breaker of the present invention, the main contact interposed in the main circuit for supplying electric power to the load, the zero-phase current transformer provided in the main circuit, and the zero-phase current transformer And a trip device that opens the main contact by a trip signal from the first leakage detection means. Second leakage detecting means for detecting the presence or absence of leakage on the basis of the zero-phase detection signal from the phase current transformer, level varying means for varying the leakage detection level of the second leakage detecting means, and second leakage. It is also characterized by comprising display means for displaying that an output signal of the detection means is generated.

In this case, it is preferable to include frequency changing means for changing the frequency characteristic of the second leakage detecting means. Further, the frequency varying means has a bandpass filter or a notch filter that passes the commercial frequency, and a highpass filter that passes the high frequency exceeding the commercial frequency, and the second leakage detecting means uses one of the filters. The passed zero-phase detection signal or the zero-phase detection signal in which the commercial frequency and the high frequency are mixed may be selected and input.

Further, the frequency characteristics of the first leakage detection means and the second leakage detection means may be matched, or the cutoff frequency of the high pass filter may be variable. The variable frequency characteristic may be stepwise or continuous.

[0011]

With the frequency varying means for varying the frequency characteristic of the earth leakage detecting means, the frequency varying means changes the frequency characteristic when the earth leakage breaker is activated by a load such as an inverter (high frequency earth leakage current). Can be turned off. Further, the second leakage detecting means is provided, and the leakage detecting level of the second leakage detecting means is changed by the level changing means,
In response to this, when the output signal of the second leakage detecting means is generated, it is displayed on the display means, so that the magnitude of the leakage current actually flowing can be determined by the display on the display means. .

In this case, in the case where the frequency varying means for varying the frequency characteristic of the second earth leakage detecting means is provided, the magnitude of the earth leakage current actually flowing can be determined for each frequency. Further, the frequency varying means has a bandpass filter or a notch filter for passing the commercial frequency, and a high-pass filter for passing a high frequency exceeding the commercial frequency, and the second leakage detecting means includes any one of the filters. In the case where the passed zero-phase detection signal or the zero-phase detection signal in which the commercial frequency and the high frequency are mixed is selected and input, the magnitude of the leakage current that actually flows is specified as the commercial frequency. It can be distinguished from high frequencies, and in addition, it is possible to select and determine even frequencies that are mixed.

In the case where the frequency characteristics of the first and second leakage detecting means are made to coincide with each other, the magnitude of the leakage current actually flowing is expressed by the frequency characteristic of the operation of the earth leakage breaker. Can be determined. In addition, if the cutoff frequency of the high pass filter is variable, the frequency of the high frequency leakage current can be determined. Further, if the frequency characteristic is continuously variable, the frequency characteristic can be changed steplessly.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, FIG. 1 shows a circuit configuration of an earth leakage circuit breaker. A main circuit 11 that supplies electric power to a load such as an electric motor is provided with a main contact 12 that opens and closes the main circuit 11. A zero-phase current transformer 13 that detects a zero-phase current is provided as a primary conductor that is a collection of conductors.

The output of the zero-phase current transformer 13 is input to the first, second, and third low-pass filters 14, 15, 16 whose frequency characteristics are different as described later.
The outputs of these low-pass filters 14 to 16 are selected by the first changeover switch 17.

More specifically, the first changeover switch 17 includes a movable contact piece O, first, second and third fixed contact pieces A,
B and C, the output of the first low-pass filter 14 is selected when the contact piece OA between them is closed, and the output of the first low-pass filter 14 is selected when the contact piece OB is closed. The output of the second low-pass filter 16 is selected, and when the contact piece OC is closed, the output of the third low-pass filter 16 is selected.

The first selected by the first changeover switch 17
The outputs of the third low pass filters 14 to 16 are input to the first leakage determination circuit 18, and when the input exceeds the set level, the first leakage determination circuit 1
Reference numeral 8 outputs a trip signal to the trip device 19, and the trip device 19 opens the main contact 12 based on the output.

Therefore, the first to third presence / absence of leakage is detected from the first to third low-pass filters 14 to 16 to the first leakage determination circuit 18 based on the zero-phase detection signal from the zero-phase current transformer 13. Leakage detecting means 20 is configured, and the first to third low-pass filters 14 to 16 and the first changeover switch 17 among them constitute the frequency varying means 21 for varying the frequency characteristic of the first leakage detecting means 20. It is supposed to work.

The output of the zero-phase current transformer 13 is also input to a bandpass filter or notch filter 22 that passes only the commercial frequency and a highpass filter 23 that passes only the high frequency that exceeds the commercial frequency. The outputs of these filters 22 and 23 are selected by the second changeover switch 24.

The second changeover switch 24 has first, second, third and fourth fixed contact pieces A, B, C and D for the movable contact piece O in detail. The output of the bandpass filter or notch filter 22 is selected when the contact piece O-B is closed, and the output of the high-pass filter 23 is selected when the contact piece O-C is closed. It is like this.

The zero-phase current transformer 13 is directly connected to the first fixed contact piece A of the second changeover switch 24, and the first changeover switch 17 is connected to the fourth fixed contact piece D. Is connected to the movable contact piece O, the output of the zero-phase detection signal in which the commercial frequency and the high frequency are mixed from the zero-phase current transformer 13 is selected when the contact piece O-A is closed. , The output of any one of the first to third low-pass filters 14 to 16 selected by the first changeover switch 17 is selected when the contact piece O-D is closed.

The output of the zero-phase detection signal in which the commercial frequency and the high frequency are mixed from the zero-phase current transformer 13 selected by the second changeover switch 24, the output of the band-pass filter or notch filter 22, and the high-pass filter 23. And the output of any one of the first to third low pass filters 14 to 16 selected by the first changeover switch 17 are input to the second leakage determination circuit 25.

In the second leakage judgment circuit 25, it is possible to change the leakage judgment level by means of the leakage judgment level changing means 26 comprising a plurality of resistors having different resistance values and a selection switch or the like. When the judgment level is exceeded, the second leakage judgment circuit 25 outputs a display operation signal to the display means 27 such as a light emitting diode and operates it.

Therefore, the band-pass filter or notch filter 22 and the high-pass filter 23 are connected to the second leakage determination circuit 25 to detect the presence / absence of leakage based on the zero-phase detection signal from the zero-phase current transformer 13. The second leakage detecting means 28 is configured, of which the band pass filter or notch filter 22 and the high pass filter 23 are included.
And the second changeover switch 24 are the second leakage detecting means 2
It functions as frequency changing means 29 for changing the frequency characteristic of 0.

Next, the operation of the above structure will be described. The first to third low-pass filters 14 to 16 in the first leakage detecting means 20 have frequency characteristics, for example, as shown in FIG.
Alternatively, each of (b) is configured differently. Of these, the example of FIG. 2A is one in which the attenuation characteristics (slope) are made different without making the cutoff frequencies different, and more specifically, if the order of the primary, secondary, and tertiary filters is different. Configured. In the example of (b) of FIG. 2, the cutoff frequency is changed without changing the attenuation characteristic.

Since the first leakage judgment circuit 18 outputs the trip signal when the input exceeds the set level, the sensitivity current of the leakage breaker is determined by the first to third low-pass filters 14-16. In the case of the characteristic (2) of No. 2, the characteristic becomes as shown in FIG. On the other hand, the first to the third
When the low-pass filters 14 to 16 of FIG. 2 have the characteristic shown in FIG. 2B, the sensitivity current of the earth leakage breaker has a characteristic in which the frequencies at which the sensitivity current starts to rise are different as shown in FIG. 3B.

Therefore, the first changeover switch 17 has the contact piece O.
-A is closed to set the sensitivity current characteristics of (a) or (b) of FIG. The setting of the first changeover switch 17 is changed to a state in which the contact piece OB or the contact piece OC is closed, and the sensitivity current characteristic of or in the same figure is set, and the sensitivity current at high frequency is changed. By raising it, it is possible to prevent the earth leakage breaker from operating. Thus, regardless of the carrier frequency of the inverter, the length of the wiring cable, etc., it is possible to make it more difficult to operate with respect to the high frequency leakage current than the conventional one.

On the other hand, in the second leakage detecting means 28, if the zero-phase detection signal detected by the zero-phase current transformer 12 is the commercial frequency, it is passed through the bandpass filter or notch filter 22 and the commercial frequency is detected. If the high frequency exceeds
It is passed through the high pass filter 23. In this situation, now
If the second changeover switch 24 is closed between the contact pieces OB, only the commercial frequency component that has passed through the bandpass filter or the notch filter 22 is input to the second leakage determination circuit 25, and this is input to this. On the other hand, the leakage judgment level changing means 26
It is possible to operate the display means 27 by appropriately adjusting the. Thus, the current value of only the commercial frequency component can be quantitatively measured.

On the other hand, the second changeover switch 24 has the contact piece O-
When C is closed, only the high-frequency component that has passed through the high-pass filter 23 is input to the second leakage determination circuit 25, and the leakage determination level varying means 26 is also correspondingly provided. By adjusting, the display means 27 can be operated. Thus, the current value of only the high frequency component can be quantitatively measured.

Further, in this case, the cutoff frequency of the high-pass filter 23 is made variable by a variable means such as a variable resistor, so that the frequency of the high frequency leakage current can be determined. Further, when the second changeover switch 24 is closed between the contact pieces O-A, the second leakage determination circuit 25 has a zero phase in which the commercial frequency and the high frequency are mixed directly from the zero phase current transformer 13. The detection signal is input,
Thus, it is possible to measure only by the detection level regardless of the frequency.

Finally, the case where the second changeover switch 24 is closed between the contact pieces OD will be described.
At this time, the same signal as the signal input to the first leakage determination circuit 18 is input to the second leakage determination circuit 25, and the magnitude of the leakage current actually flowing is determined by the leakage breaker. It can be determined by the frequency characteristic of the operation of. FIG. 4 shows an example of the characteristic. By making the sensitivity current characteristic of the earth leakage breaker equal to the maximum value that can be set by the earth leakage judgment level changing means 26, the display means 27 can be operated by the sensitivity current and below that. It is also possible to operate the display means 27 with any characteristic of

In the above embodiment, the frequency characteristics of the first and second leakage detecting means 20 and 28 are changed stepwise by the first and second changeover switches 17 and 24. The frequency characteristics may be changed continuously and steplessly by changing the circuit constants of 16 to 22, 22 and 23, for example, by using variable resistors as resistors. in case of,
You will be able to provide more detailed support.

[0033]

The earth leakage breaker of the present invention is as described above, and has the following effects. First, a main contact interposed in a main circuit that supplies electric power to a load, a zero-phase current transformer provided in the main circuit, and a leakage current based on a zero-phase detection signal from the zero-phase current transformer. An electric leakage detecting means for detecting presence or absence and a trip device for opening a main contact by a trip signal from the electric leakage detecting means are provided with frequency changing means for changing the frequency characteristic of the electric leakage detecting means. By doing so, when the earth leakage breaker is activated by a high frequency zero-phase current due to a load such as an inverter, the frequency characteristics are changed to increase the sensitivity current at high frequencies so that the earth leakage breaker will not easily operate. You can

Secondly, a main contact interposed in the main circuit for supplying electric power to the load, a zero-phase current transformer provided in the main circuit,
First leakage detecting means for detecting the presence or absence of leakage on the basis of a zero-phase detection signal from the zero-phase current transformer, and a trip device for opening a main contact by a trip signal from the first leakage detecting means. And a second leakage detection means for detecting the presence or absence of leakage on the basis of the zero-phase detection signal from the zero-phase current transformer, and a level variable for varying the leakage detection level of the second leakage detection means. By providing the means and the display means for displaying that the output signal of the second leakage detecting means is generated, the magnitude of the leakage current actually flowing can be discriminated by the display by the display means. Therefore, it is possible to grasp the margin for the operating level.

Thirdly, since the frequency varying means for varying the frequency characteristic of the second leakage detecting means is provided, the magnitude of the leakage current actually flowing can be discriminated for each frequency.

Fourthly, the frequency varying means is a bandpass filter or a notch filter for passing a commercial frequency,
And a high-pass filter for passing a high frequency exceeding the commercial frequency, wherein the second leakage detecting means has a zero-phase detection signal passing through any one of the filters or a zero-phase detection signal in which the commercial frequency and the high frequency are mixed. By selecting and inputting it, the magnitude of the leakage current actually flowing can be specifically discriminated between the commercial frequency and the high frequency. Can be determined.

Fifth, by making the frequency characteristics of the first and second leakage detecting means coincide with each other, the magnitude of the leakage current that is actually flowing is determined by the frequency of the operation of the leakage breaker. It can be identified by the characteristics. Sixth, the frequency of the high-frequency leakage current can be determined by providing the means for varying the cutoff frequency of the high-pass filter. Seventh, by making the frequency characteristic variable continuously, the frequency characteristic can be changed steplessly, and more detailed correspondence can be made.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 2 is an example of characteristics of a low-pass filter (a) and (b).
Figure shown by two

FIG. 3 is a diagram showing two examples (a) and (b) of the sensitivity current characteristics of the earth leakage breaker.

FIG. 4 is a characteristic diagram when the frequency characteristics of the first and second leakage detecting means are matched.

FIG. 5 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 6 Sensitivity current characteristic diagram

[Explanation of symbols]

11 is a main circuit, 12 is a main contact, 13 is a zero-phase current transformer, 1
4, 15 and 16 are low-pass filters, 17 is a first changeover switch, 18 is a first leakage determination circuit, 19 is a trip device, 20 is a first leakage detection means, 21 is a frequency varying means, and 22 is a band. Pass filter or notch filter, 2
3 is a high pass filter, 24 is a second changeover switch, 2
5 is a second leakage determination circuit, 26 is a leakage determination level changing means, 27 is a display means, 28 is a second leakage detection means, 29
Indicates frequency changing means.

Claims (10)

[Claims] 1. A main contact interposed in a main circuit for supplying electric power to a load, a zero-phase current transformer provided in the main circuit, and a zero-phase detection signal from the zero-phase current transformer. It comprises a leakage detecting means for detecting the presence or absence of leakage, a trip device for opening the main contact by a trip signal from the leakage detecting means, and a frequency varying means for varying the frequency characteristic of the leakage detecting means. An earth leakage circuit breaker characterized by the above. 2. The earth leakage breaker according to claim 1, wherein the frequency variable means has a plurality of low-pass filters having different attenuation characteristics, and one of the low-pass filters is selected. 3. The earth leakage breaker according to claim 1, wherein the frequency variable means has low-pass filters having different cutoff frequencies, and one of the low-pass filters is selected. 4. A main contact interposed in a main circuit for supplying power to a load, a zero-phase current transformer provided in the main circuit, and a zero-phase detection signal from the zero-phase current transformer. First leakage detecting means for detecting the presence / absence of leakage, a trip device for opening the main contact by a trip signal from the first leakage detecting means, and a zero-phase detection signal from the zero-phase current transformer Second leakage detecting means for detecting the presence or absence of leakage based on the above, level changing means for varying the leakage detection level of the second leakage detecting means, and generation of an output signal of the second leakage detecting means. An earth leakage circuit breaker characterized by comprising display means for displaying. 5. The earth leakage breaker according to claim 4, further comprising frequency changing means for changing the frequency characteristic of the second earth leakage detecting means. 6. The frequency varying means has a bandpass filter or a notch filter for passing a commercial frequency and a highpass filter for passing a high frequency exceeding the commercial frequency, and the second leakage detecting means is any one of them. 6. The earth leakage circuit breaker according to claim 5, wherein the zero-phase detection signal that has passed through the filter or the zero-phase detection signal in which the commercial frequency and the high frequency are mixed is selected and input. 7. The frequency characteristic of the first leak detecting means and the frequency characteristic of the second leak detecting means are made to coincide with each other.
Alternatively, the earth leakage breaker described in 5. 8. The earth leakage breaker according to claim 6, further comprising means for varying a cutoff frequency of the high pass filter. 9. The earth leakage breaker according to claim 1, wherein the variable frequency characteristic is stepwise. 10. The earth leakage breaker according to claim 1, wherein the frequency characteristic is continuously variable.