JPH07296708A - Wiring breaker - Google Patents

Abstract

PURPOSE:To detect flow of a high frequency leakage current by detecting a high frequency component in a cable run and outputting it to the outside. CONSTITUTION:A current flowing through a cable run 1 is detected by a current transformer 2, converted to a DC voltage by adding DC offset at a current detecting circuit 10 and inputted to an A/D converting circuit 11 and a DC voltage is divided and converted to a digital value. The square values thereof are integrated by a calculating part 12 for a certain period and an integrated value and a reference value are compared with a each other. When the integrated value exceeds the reference value, presence of some overcurrent is judged, a driving signal is outputted from a pulling out circuit 6 and a contact point 7 is opened/closed. As for detection of a high frequency leakage current, after a leakage current flowing in the cable run 1 is detected by means of a zero phase current converter 4 and converted to a voltage value by means of a resistor 13, the high frequency component of a signal voltage is detected by means of a high-pass filter 15. Then, after this is converted to a digital value by means of an A/D converting circuit 10, the effective value of a high frequency is obtained by means of the calculating part 12 and in response thereto, outputted to the outside from an output device 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit breaker for wiring.

[0002]

2. Description of the Related Art A circuit breaker for wiring is a circuit for tripping a contact by a drive signal from a tripping circuit to interrupt the circuit when an overcurrent flows through the circuit. Conventionally, in an electronic circuit breaker for wiring, a structure as shown in FIG. In this figure, 1 is a 3-phase 3-wire type electric circuit, 2 is a current transformer that detects the current flowing in the electric circuit 1, and 3 is an overcurrent that receives the output current of the current transformer 2 and determines whether there is an overcurrent. Determining means 6 is a trip circuit which receives the output signal of the overcurrent determining means 3 and drives a contact 7 which opens and closes the electric path 1. Also, the overcurrent determination means 3
Has a current detection circuit 10, an A / D conversion circuit 11, and a calculation unit 12. With such a configuration, the AC current of the electric circuit 1 is detected by the current transformer 2 and converted into an AC voltage by the current detection circuit 10 of the overcurrent determination means 3. Then, the AC voltage is converted into a digital value by the A / D conversion circuit 11, and when the arithmetic unit 12 determines that it is an overcurrent, an output signal is transmitted to the trip circuit 6 and the contact 7 is tripped. . There is also a type in which a zero-phase current transformer is built in a circuit breaker for wiring to detect a leakage current and trip the contact.

On the other hand, recently, due to the increase in the number of semiconductor switching circuits used in inverters and the like, the high frequency leakage current in electric circuits has increased. This high-frequency leakage current may be a cause of malfunction when it is superimposed on a communication line and adversely affects other devices, or when a circuit breaker for wiring with leakage detection is used to detect the leakage current and cut off the electric circuit. To become. Therefore, a high-frequency leakage current is detected by arranging a current transformer for measurement or a zero-phase current transformer on the electric wire of the electric circuit and measuring it with a dedicated measuring instrument. Measures have been taken to remove high frequency leakage current, such as adding filters. In addition, in the case of a circuit breaker with leakage detection, a low-pass filter is used to reduce the frequency to 50 H
In some cases, a high frequency component may be removed as noise by inputting the z, 60 Hz component as a signal voltage and determining leakage.

[0004]

As described above, the detection of the high frequency component of the electric circuit must be measured by a dedicated measuring instrument, which is troublesome and troublesome. In addition, the measure for removing the high frequency component as noise in the circuit breaker with the leakage detection is not to inform the outside when the high frequency leakage current is flowing in the electric line.

The present invention has been made in view of the above circumstances, and provides an electronic circuit breaker, which can inform a high-frequency leakage current when a high-frequency leakage current is flowing in a circuit. The purpose is to

[0006]

In order to solve such a problem, a wiring breaker according to claim 1 receives a current transformer for detecting a current flowing in an electric circuit and an output current of the current transformer. In a circuit breaker for wiring, which comprises an overcurrent judging means for judging the presence or absence of an overcurrent and a trip circuit for driving a contact for opening and closing the electric circuit by receiving an output signal of the overcurrent judging means, a leakage current flowing in the electric circuit. A zero-phase current transformer that detects a current, a high-frequency detection unit that detects a high-frequency component of the electric path from the output current of the zero-phase current transformer, and an output device that outputs to the outside based on the output signal of the high-frequency detection unit. It has an attached structure.

According to a second aspect of the present invention, there is provided a circuit breaker for wiring according to the first aspect, wherein the high-frequency detecting means has a high-pass filter for obtaining a high-frequency component of the output current of the zero-phase current transformer and a higher frequency than the output signal of the high-pass filter. A determination unit for determining the level,
It is configured to have.

The circuit breaker for wiring according to a third aspect of the present invention is such that the determination section according to the second aspect includes an effective value calculation section for calculating and determining an effective value from an output signal of the high-pass filter.

According to a fourth aspect of the present invention, there is provided a wiring breaker in which the judging section according to the second aspect includes a comparator for comparing the output signal of the high pass filter with a predetermined level.

[0010]

According to the structure of the first aspect, by detecting the high frequency component of the electric line and outputting it to the outside when it is present, the electric circuit can be easily connected to the place where the circuit breaker for wiring is installed. It can be seen that high frequency leakage current is flowing.

According to the structure described in claim 2, in addition to the effect of claim 1, the high-frequency component of the electric path can be obtained by the high-pass filter, so that it can be realized with a simple structure.

According to the third aspect of the present invention, in addition to the effect of the second aspect, the high frequency level can be determined by calculating the effective value of the output signal of the high pass filter in the arithmetic unit. The value of the high frequency level can be judged numerically.

According to the structure of claim 4, in addition to the effect of claim 2, the high frequency level can be determined by comparing the output signal of the high pass filter with a predetermined level by a comparator. , It is possible to output accurately to the outside based on the level.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. Members having the same basic functions as those described in the conventional example are designated by the same reference numerals.

In the present embodiment, a circuit breaker for wiring which is provided with overcurrent detection and leakage detection is provided with high frequency leakage current detection. FIG. 1 is a block diagram showing the configuration of a circuit breaker for wiring, which includes a circuit 1, a current transformer 2, an overcurrent determination unit 3, a zero-phase current transformer 4, an earth leakage detection unit 5, a trip circuit 6, and a contact 7. The high frequency detection means 8 and the output device 9 are the main constituent members.

The electric circuit 1 is for connecting a circuit breaker for wiring, and shows a case of a three-phase three-wire system. In addition, electric line 1 is 3
The phase 3-wire system is not particularly limited.

The current transformer 2 detects the current flowing in the electric path 1 and outputs an alternating current. Current transformer 2 is circuit 1
Since it is a three-phase three-wire system, three are used.

The overcurrent judging means 3 receives the output current of the current transformer 2 and judges whether or not there is an overcurrent. The overcurrent judging means 3 is composed of a current detection circuit 10, an A / D conversion circuit 11 and an arithmetic unit 12. It The current detection circuit 10 converts an AC current output from the current transformer 2 into an AC voltage, rectifies it by adding an offset, and converts it into a DC voltage. Specifically, the AC current is converted into a voltage value via a resistor, and a DC offset of 2.5 V output from a DC offset power supply circuit (not shown) is added to rectify the voltage.

The A / D conversion circuit 11 divides the output voltage of the current detection circuit 10 into a predetermined time width and converts each divided voltage into a digital value. For example, the output voltage is digitized every 1 msec which is a sampling time which is a divided time width. Assuming that the maximum input voltage of the A / D conversion circuit 11 is 5v and the resolution of digital conversion is 8 bits, A / D
The output of the conversion circuit 11 is 0 when 0v, 127 when 2.5v, and 255 when 5v. Where A / D
When the current detection circuit 10 is adjusted so that the 1-bit current value at the time of conversion corresponds to 2 A, the current of -256 A to +256 A can be measured as the performance of the A / D conversion circuit 11. When a large overcurrent that cannot be A / D converted is input, the value becomes 255 above the upper limit value and 0 below the lower limit value.

The arithmetic unit 12 is mainly composed of a microcomputer, squares the digital value of each divided voltage of the A / D conversion circuit 11, and squares the squared value of the electric current of the electric circuit at the integration period. Accumulate over one cycle. Then, the integrated value is compared with a predetermined reference value to determine whether or not the reference value is exceeded. If the reference value is exceeded, an output signal is transmitted to a trip circuit 6 described later. The reference value can be set to an arbitrary value by the input means and can be changed. Further, the effective value of the current flowing through the electric circuit 1 is obtained by dividing the integrated value by the integration period and then performing the square root calculation.

The zero-phase current transformer 4 is formed of permalloy or the like and detects a leak current flowing through the electric path 1, and outputs an output current proportional to the leak current.

The earth leakage determining means 5 receives the output current of the zero-phase current transformer 3 and determines the presence or absence of earth leakage, and
3. Low-pass filter 14 and A / D conversion circuit 1 described above
1. Comprised of a calculation unit 12. The resistor 13 is for converting the output current of the zero-phase current transformer 4 into a signal voltage, and the low-pass filter 14 is a filter for passing the low-frequency component of the signal voltage. The signal is digitally converted by the A / D conversion circuit 11. After the conversion, the arithmetic unit 12 determines the presence / absence of electric leakage, and when the electric leakage is determined, an output signal is transmitted to a trip circuit 6 described later.

The tripping circuit 6 receives the output signal of the overcurrent judging means 3 or the leakage judging means 5 and outputs a drive signal to a contact 7 which will be described later.

Although not shown, the contact 7 has a movable contact and a fixed contact, and receives the drive signal of the trip circuit 6 to open and close the electric path 1.

The high frequency detecting means 8 detects the high frequency component of the electric path 1 from the output current of the zero-phase current transformer 4. The high frequency detecting means 8 is composed of a high-pass filter 15 and a judging section 16, and the judging section 16 is composed of the A / D conversion circuit 11 and the arithmetic section 12 described above. The high-pass filter 15 is a filter that passes the high-frequency component of the signal voltage obtained by converting the output current of the zero-phase current transformer 4 by the resistor 13, and after converting the signal into a digital value by the A / D conversion circuit 11, the calculation unit
Calculate the effective value in 12, and output device described later according to the value.
Output the output signal to 9.

The output device 9 outputs to the outside based on the output signal of the high frequency detecting means 8. As a means therefor, there is a method of turning on an alarm or an LED, or outputting to the outside as a contact signal. When the effective value itself is required, the value can be displayed directly on the LCD or the like, or the value can be displayed externally by using the communication function.

Next, the operation of the present invention will be described. First, overcurrent detection will be described. The current flowing through the electric circuit 1 is detected by the current transformer 2, and the current detection circuit 10 adds a DC offset to convert it into a DC voltage, which is input to the A / D conversion circuit 11. In the A / D conversion circuit 11, the direct current voltage is divided and converted into a digital value, the square value is integrated for a certain period in the arithmetic unit 12, the integrated value is compared with a predetermined reference value, and the reference value is calculated. Determine if it has been exceeded. When it exceeds the reference value, it is judged as an overcurrent, a trip circuit 6 outputs a drive signal, and the contact 7 is opened and closed.

Further, in the case of detecting the leakage, the zero-phase current transformer 4 detects the leakage current flowing in the electric path 1, the resistance 13 converts it into a voltage value, and the low-pass filter 14 extracts the low-frequency component of the signal voltage. To do. Then, after the digital value is converted by the A / D conversion circuit 10, the presence / absence of electric leakage is judged by the arithmetic unit 12, and if the electric leakage is judged, the trip circuit 6 outputs a drive signal to open / close the contact 7. To do.

Further, the high-frequency leakage current is detected by detecting the leakage current flowing in the electric path 1 with the zero-phase current transformer 4, converting it into a voltage value with the resistor 13, and then extracting the high-frequency component of the signal voltage with the high-pass filter 15. To do. Then, after being converted into a digital value by the A / D conversion circuit 10, the effective value of the high frequency is obtained by the arithmetic unit 12 and correspondingly output to the outside from the output device 9. Further, in the high frequency detection, by sampling every 1 μs, a frequency up to about 1 MH can be detected.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the determination unit 16 is different from that of the first embodiment, and that point will be mainly described.

Reference numeral 17 denotes a comparator, which is a judging section 16 of the high frequency detecting means 8 and judges the high frequency component of the electric circuit 1. This comparator 17 compares the voltage signal with a predetermined level, and outputs a signal to the output device 9 when the voltage signal is exceeded.

With this structure, the high frequency leakage current can be detected as follows. First, zero-phase current transformer 4
The leak current flowing in the electric circuit 1 is detected by, the voltage value is converted by the resistor 13, and the high frequency component of the signal voltage is extracted by the high pass filter 15. Then, the comparator 17 compares the high frequency component with a predetermined level, and when it exceeds the predetermined level, the output device 9 outputs it to the outside.

Although the high frequency detecting means is provided in the circuit breaker for wiring capable of both overcurrent detection and leakage detection, it may be provided in only one of them. Further, when the high-frequency detecting means is provided in the wiring breaker with the leakage detection, the zero-phase current transformer can also be used, so that low cost can be realized.

[0034]

The wiring breaker according to the first aspect of the present invention makes it easy to install the wiring breaker by detecting the high frequency component of the electric path and outputting it to the outside when it is present. Since it can be seen that the high frequency leakage current is flowing in the electric circuit, it is easy to take measures against the high frequency leakage current.

The circuit breaker for wiring according to claim 2 achieves the effect of claim 1, and since the high-frequency component of the electric path can be obtained by the high-pass filter, it can be realized with a simple structure, so that the device can be made compact. Can be achieved.

The circuit breaker according to claim 3 achieves the effect of claim 2 and further determines the high frequency level.
Since the calculation unit can calculate and determine the effective value of the output signal of the high-pass filter, the magnitude of the high-frequency level can be determined as a numerical value, so that the high-frequency level can be accurately grasped and the countermeasure can be more easily taken.

Further, the circuit breaker for wiring according to claim 4 achieves the effect of claim 2, and in addition, the determination of the high frequency level is:
Since it is possible to compare the output signal of the high-pass filter with a predetermined level by the comparator, it is possible to accurately output the signal to the outside on the basis of the level, so that it is possible to reduce an erroneous decision.

[Brief description of drawings]

FIG. 1 is a block diagram of a wiring breaker showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration thereof.

FIG. 3 is a block diagram showing the high frequency detecting means.

FIG. 4 is a block diagram showing a high frequency detecting means of a circuit breaker for wiring according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a wiring breaker showing a conventional example of the present invention.

[Explanation of symbols]

 1 Electric circuit 2 Current transformer 3 Overcurrent judging means 4 Zero-phase current transformer 5 Leakage judging means 6 Tripping circuit 7 Contact 8 High frequency detecting means 9 Output device 10 Current detecting circuit 11 A / D conversion circuit 12 Arithmetic unit 14 Low pass filter 15 High-pass filter 16 Judgment section 17 Comparator

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[Procedure amendment]

[Submission date] August 3, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The overcurrent judging means 3 receives the output current of the current transformer 2 and judges whether or not there is an overcurrent. The overcurrent judging means 3 is composed of a current detection circuit 10, an A / D conversion circuit 11 and an arithmetic unit 12. It The current detection circuit 10 converts the alternating current output from the current transformer 2 into an alternating current voltage by adding an offset to +
Lift to the side and convert to signal voltage . Specifically, the alternating current is converted into a voltage value via a resistor, a 2.5v direct current offset output from a DC offset power supply circuit (not shown) is added, and the voltage is raised to the + side .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

Next, the operation of the present invention will be described. First, overcurrent detection will be described. The current flowing through the electric circuit 1 is detected by the current transformer 2, a DC offset is added by the current detection circuit 10 and converted into a signal voltage, which is input to the A / D conversion circuit 11. In the A / D conversion circuit 11, the signal voltage is divided and converted into a digital value, and the square value is integrated for a certain period in the arithmetic unit 12, and the integrated value is compared with a predetermined reference value, and the reference value is calculated. Determine if it has been exceeded. When it exceeds the reference value, it is judged as an overcurrent, a trip circuit 6 outputs a drive signal, and the contact 7 is opened and closed.

Claims (4)

[Claims] 1. A current transformer that detects a current flowing through an electric circuit, an overcurrent determination unit that receives the output current of the current transformer and determines the presence or absence of an overcurrent, and an output signal of the overcurrent determination unit. In a circuit breaker for wiring that includes a trip circuit that drives a contact that opens and closes the circuit, the zero-phase current transformer that detects the leakage current flowing in the circuit and the high-frequency current of the circuit from the output current of the zero-phase current transformer A circuit breaker for wiring, comprising: a high-frequency detecting means for detecting a component; and an output device for outputting to the outside based on an output signal of the high-frequency detecting means. 2. The high-frequency detecting means includes a high-pass filter for obtaining a high-frequency component of the output current of the zero-phase current transformer, and a judging section for judging a high-frequency level from the output signal of the high-pass filter. The circuit breaker according to claim 1. 3. The wiring breaker according to claim 2, wherein the determination unit includes an effective value calculation unit that calculates and determines an effective value from an output signal of the high-pass filter. 4. The wiring breaker according to claim 2, wherein the determination unit includes a comparator that compares the output signal of the high-pass filter with a predetermined level.