JPH07298475A - Circuit breaker - Google Patents

Abstract

PURPOSE:To prevent tripping of a contact mistakenly by performing re-judgment with trip re-judging means when a trip signal is output from a trip judging circuit or an instantaneous trip judging circuit. CONSTITUTION:A trip judging circuit 8 compares an integrated value of an integrating circuit 7 with a predetermined reference value, judges whether the reference value is exceeded and, if the reference value is exceeded, then a detected signal is output to trip re-judging means 13. The instantaneous trip judging circuit 9 receives a short-circuit signal output from a second transformer 3 and sends out a second detected signal to the trip re-judging means 13. The trip re-judging means 13 receives a detected signal from the trip judging circuit 8 or the instantaneous trip judging circuit 9 and judges again whether an overcurrent is flowing through a cable way 1. By doing this, mistakenly tripping a setting 12 can be reduced and the reliability of the tripping of the setting 12 can be improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electronic circuit breaker.

[0002]

2. Description of the Related Art A circuit breaker of this type generally has a structure shown in FIG. In the figure, 1 is a 3-phase 3-wire type electric circuit, 2 is a first current transformer that detects the current flowing in the electric circuit 1, and
3 is the second current transformer that detects the current flowing in the electric circuit 1 and is less sensitive than the first current transformer 2, and 4 is the DC current due to the DC offset of the output current of the first current transformer 2. Current-voltage conversion circuit for converting to, DC offset power supply circuit for 5 and 6 A / D conversion circuit for converting the DC voltage into a digital value by dividing the DC voltage with a predetermined time width, 7 for squaring the digital value and converting it An integrating circuit that integrates for a predetermined period, 8 is a trip determination circuit that compares the integrated value of the integrating circuit with a predetermined reference value and outputs a trip signal when in the trip state, and 9 is a second current transformer 3
Output circuit is input and the trip signal is output when it is in the instantaneous trip state.10 is the trip circuit that outputs the drive signal when the trip signals of both decision circuits 8 and 9 are input. A circuit, 11 is a trip coil that drives a contact 12 inserted in the electric line 1 to open and close the electric line 1 when a drive signal is input. Normally, A / D conversion circuit 6, integrating circuit
The electronic circuit parts such as 7, the trip determination circuit 8 and the instantaneous trip determination circuit 9 are configured by a microcomputer.

In such a circuit breaker, when an overcurrent flows in the electric circuit 1, the trip determination circuit 8 causes the short circuit current in the electric circuit 1 (a kind of overcurrent, a current of about 1000% or more of the rating). In the case where the current flows, the instantaneous trip determination circuit 9 outputs the trip signal to the trip circuit 10, and the trip circuit 10 outputs the drive signal to the trip coil 11 to trip the contact 12 (opening). To).

More specifically, in the former case, the alternating current in the electric circuit 1 is detected by the first current transformer 2, and the current-voltage conversion circuit 4 is detected.
Converted to AC voltage by DC offset power supply circuit
It is rectified into a DC voltage by the DC offset of 5. Then, the DC voltage is converted into a digital value by the A / D conversion circuit 6, and the digital value is integrated for a predetermined time by the integration circuit 7, and it is determined by tripping that the integrated value exceeds a predetermined reference value. When the circuit 8 detects it, it sends a trip signal to the trip circuit 10. A flowchart showing the algorithm at that time is as shown in FIG. In the latter case, if the second current transformer 3 detects the short-circuit current flowing in the electric circuit 1 and the instantaneous trip determination circuit 9 determines that there is a short circuit, the program is interrupted using the flowchart of the algorithm shown in FIG. Then, the trip signal is transmitted to the trip circuit 10.

[0005]

In the above-mentioned conventional circuit breaker, since the input signal of the A / D conversion circuit is 0 to 5V,
If noise is mixed in the trip determination circuit, etc., or if there is an abnormality in the power supply voltage of the circuit, it may appear that current is flowing even if no current is flowing in the circuit. , Accidentally trip the trip coil,
The contact may be tripped. In addition, the instantaneous trip determination circuit sends an interrupt signal to the program, but if noise is superimposed on this signal line and it is regarded as an interrupt signal, the contact is immediately tripped, and false trip occurs. Sometimes.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic circuit breaker which is highly reliable and has less malfunctions when tripping the contacts.

[0007]

In order to solve the above problems, a circuit breaker according to a first aspect of the present invention is provided with a first current transformer and a second current transformer for detecting a current flowing in an electric circuit, and a first current transformer. Current-voltage conversion circuit for converting the output current of the sink into a DC voltage by a DC offset, an A / D conversion circuit for dividing the DC voltage into a digital value by dividing the DC voltage in a predetermined time width, and a digital value squared And an integrating circuit that integrates it for a predetermined period,
A trip determination circuit that compares the integrated value of the integrator circuit with a predetermined reference value and outputs a trip signal when in the trip state, and the output current of the second current transformer is input and is in the instantaneous trip state. When the trip signal of both decision circuits is input, the trip circuit that outputs the drive signal when the trip signal of both decision circuits is input, and the contact that opens and closes the electric circuit when the drive signal is input are driven. In the circuit breaker having the trip coil, the first or second current transformer is provided when the trip signal of the trip judgment circuit or the instantaneous trip judgment circuit is input to the preceding stage of the trip circuit. The trip re-determination means for performing the determination again from the output current of 1 to output the trip signal is provided.

The circuit breaker according to claim 2 is the circuit breaker according to claim 1, wherein the trip redetermination means is:
When the first trip signal is input, the trip determination circuit immediately determines whether or not the output current of the first current transformer at that time is in the trip state, and the trip determination circuit again outputs the trip signal. When it is output, a trip signal is output to the trip circuit.

Further, in the circuit breaker according to a third aspect, the trip redetermination means according to the second aspect determines whether or not the DC offset voltage has a predetermined value. A configuration is provided in which a voltage monitoring unit is provided to allow the trip determination circuit to determine whether the output current is in the trip state.

According to a fourth aspect of the circuit breaker, the trip re-determination means according to the first aspect is provided with a storage means for storing the output current of the first current transformer for a predetermined time period. Immediately after the removal signal is input, the output current stored in the storage means is converted into a binarized pulse based on a predetermined value,
Further, when the sum of one of the binarized pulses reaches a predetermined number, it is determined that the instantaneous trip state is present and a trip signal is output to the trip circuit.

[0011]

According to the structure of claim 1, when the trip signal is output from the trip determination circuit or the instantaneous trip determination circuit, the contact is not immediately tripped, but the trip re-determination means is used again. By making the determination, accidental tripping of contacts is reduced.

According to the second aspect of the present invention, in addition to the effect of the first aspect, the trip re-determination means determines whether the output current of the first current transformer is in the trip state again. By adopting the configuration for making the judgment, the same parts such as the A / D conversion circuit can be used, and the parts can be shared.

According to the third aspect of the invention, in addition to the effect of the second aspect, the voltage monitoring section determines whether or not the DC offset voltage is a predetermined value, and when the DC offset voltage is the predetermined value, the trip determination circuit. By re-determining, the accuracy of overcurrent detection is further improved by simple addition of components.

According to the structure of claim 4, in addition to the effect of claim 1, it is possible to perform a short-time calculation by re-determining whether or not the short-circuit current has flowed with the current recorded in the storage means. The accuracy of overcurrent detection can be improved.

[0015]

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.

FIG. 1 is a block diagram showing the configuration of a circuit breaker, which is a three-phase three-wire type electric circuit 1, a first current transformer 2, a second current transformer 3, a current-voltage conversion circuit 4, a DC. Offset power supply circuit 5, A / D conversion circuit 6, integrating circuit 7, trip determination circuit 8
The instantaneous trip determination circuit 9, the trip redetermination means 13, the trip circuit 10, and the trip coil 11 are the main constituent members.
Also, A / D conversion circuit 6, integrating circuit 7, trip determination circuit
8, the electronic circuit portion such as the instantaneous trip determination circuit 9 is configured by the microcomputer 14. The electric circuit 1 connected to the circuit breaker shows the case of the three-phase three-wire system, but it is not particularly limited to the three-phase three-wire system.

The first current transformer 2 detects the current flowing in the electric path 1 and outputs an alternating current. First current transformer 2
Since the electric circuit 1 has a three-phase three-wire system, three electric circuits are used. For example, a current waveform as shown in FIG. 2 is detected.

The second current transformer 3 detects a short-circuit current flowing in the electric path 1 and outputs a pulse-like signal, and is less sensitive than the first current transformer 2. The short-circuit current is a kind of overcurrent and has a value of about 1000% or more of the rating.

The current-voltage conversion circuit 4 converts the AC current output from the first current transformer 2 into an AC voltage, rectifies it by adding a DC offset, and converts it into a DC voltage.
Specifically, the AC current is converted to a voltage value via a resistor,
The DC offset power supply circuit 5 adds a DC offset of 2.5 V for rectification. The output waveform of the current-voltage conversion circuit 4 is shown in FIG. Further, another output of the DC offset power supply circuit 5 is input to the A / D conversion circuit 6 described later.

The A / D conversion circuit 6 is a current-voltage conversion circuit.
The output voltage of 4 is divided by a predetermined time width and each divided voltage is converted 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. If the maximum input voltage of the A / D conversion circuit 6 is 5v and the resolution of digital conversion is 8 bits,
The output of the A / D conversion circuit 6 is 0 when it is 0v, 2.5v
Is 127 and 5v is 255. here,
If the current-voltage conversion circuit 4 is adjusted so that the 1-bit current value during A / D conversion corresponds to 2 A, the A / D conversion circuit
As the performance of 6, it is possible to measure the current from -256A to + 256A. Therefore, if a large overcurrent Q that cannot be A / D converted as shown in FIG.
As shown in, 255 above the upper limit and 0 below the lower limit
Will be the value.

The integration circuit 7 squares the digital value of each divided voltage of the A / D conversion circuit 6, and integrates the squared value over one cycle of the electric circuit current, which is the integration cycle of the integration time width.

The trip determining circuit 8 compares the integrated value of the integrating circuit 7 with a predetermined reference value and determines whether or not the reference value is exceeded. If the reference value is exceeded, a tripping operation described later is performed. The detection signal is output to the redetermination means 13. That is, the electric circuit
It detects the overcurrent of 1. The reference value of the trip determination circuit 8 can be set to an arbitrary value by input means and can be changed.

The instantaneous trip determination circuit 9 receives the short-circuit signal output from the second current transformer 3 and outputs a second detection signal to the trip redetermination means 13 similarly to the trip determination circuit 8. To do. Specifically, the pulse signal output from the second current transformer 3 is received, and a step voltage of 5 V is applied to the trip redetermination means 13.

The trip redetermination means 13 is a trip determination circuit 8
And the second detection signal of the instantaneous trip determination circuit 9 are received, and it is determined again whether or not an overcurrent is flowing in the electric circuit 1. The trip re-determination means 13 makes two types of determinations. First, the voltage monitoring unit 15 provided in the trip redetermination unit 13 determines whether the DC offset of the DC offset power supply circuit 5 is a predetermined value. If it is not the predetermined value, the DC offset is corrected. Secondly, the current flowing in the electric circuit 1 is detected again by the first current transformer 2, and the current-voltage conversion circuit 4,
After passing through the A / D conversion circuit 6 and the integration circuit 7, the trip determination circuit 8 determines again whether or not the integrated value exceeds the reference value.

The output circuit 16 receives a signal output by the trip re-determination means 13 when the DC offset has a predetermined value and the integrated value exceeds the reference value, and the trip circuit 10 receives the trip signal. Is output. Further, the trip circuit 10 includes a trip coil 11
The drive signal is output to and the contact 12 that opens and closes the electric path 1 is opened.

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 square root calculation. However, in this embodiment, the integrated value is treated as a virtual effective value.

Next, the operation of the present invention will be described. FIG. 6 is a flowchart showing an operation algorithm,
It shows a case where it is judged from the current detected by the first current transformer 2 whether it is an overcurrent, and the contact 12 is opened when it is judged as an overcurrent.

The first current transformer 2 detects the current flowing in the electric path 1 (a), and the current-voltage conversion circuit 4 adds a DC offset to convert it into a DC voltage, which is input to the A / D conversion circuit 6.
The A / D conversion circuit 6 divides the DC voltage and converts it into a digital value (b), and the integration circuit 7 integrates the squared value for a certain period (c). Then, the trip determination circuit 8 compares the integrated value with a predetermined reference value and determines whether or not the reference value is exceeded (d). If the reference value is exceeded, the trip redetermination means 13 is used. Again, the first current transformer 2 detects the current flowing in the electric circuit 1 and the DC offset of the DC offset power supply circuit 5 (e). Further, the voltage monitoring unit 15 determines whether this DC offset is a predetermined value (f),
When it is a predetermined value, the current detected by the first current transformer 2 is passed through the current-voltage conversion circuit 4, the A / D conversion circuit 6 and the integrating circuit 7 to check again whether the integrated value exceeds the reference value. Judgment is made by the trip judgment circuit 8 (g). If it is judged that the reference value is exceeded, it is judged as an overcurrent, and the trip circuit 10 is tripped from the output circuit 16.
A trip signal is output to the output terminal, a drive signal is output to the trip coil 11 (h), and the contact 12 is opened (i).

On the other hand, in response to the short circuit signal output from the second current transformer 3, the instantaneous trip determination circuit 9 trips and redetermines means 1
When the second detection signal is output to 3, the portion (e) of FIG. 6 is interrupted, and then the same operation as described above is performed.

With such a configuration, tripping determination is performed three times, so that more accurate overcurrent determination can be performed.

Although the trip re-determination means 13 is configured to perform two types of trip determinations, either one may be used separately. Further, although the A / D conversion circuit 6 and the like are configured by a microcomputer, this is not particularly limited.

Next, a second embodiment of the present invention will be described with reference to FIGS.
It will be described based on. Although not shown, in this embodiment, the trip re-determination means 13 is provided with a storage means and a short-circuit current re-determination part, and a part different from the first embodiment will be described.

The storage means is an electric circuit detected by the first current transformer 2.
The current flowing in 1 is stored for a predetermined time,
It is composed of a queue buffer and is provided inside the microcomputer 14. This storage means stores the current value from the present to a certain time ago at any time.

The short-circuit current re-determining unit converts the current value stored in the storage means into a binarized pulse by a predetermined threshold value R as shown in FIG. 8, and the sum of one of the binarized pulses reaches a predetermined number. Whether the short-circuit current has flowed or not is determined. The binarization process is performed in the range of 0-R and 0-R.
The processing is set to 0, and if R or more and -R or less, it is set to 1.
Is set to about 5% of the amplitude of the current. This is because, due to the characteristics of the first current transformer 2, when a short-circuit current of 1000% or more of the rating flows, the sampling result is divided into around 0 level and the overflow.

Next, the operation of the present invention will be described. In normal times, the circuit breaker is the first current transformer for the current flowing in circuit 1.
Detected by 2, current-voltage conversion circuit 4, A / D conversion circuit 6
After passing through the integrating circuit 7, the trip determining circuit 8 determines whether the integrated value exceeds the reference value. When a short-circuit current flows in the electric circuit 1, the second current transformer 3 outputs a short-circuit signal, and the instantaneous trip determination circuit 9 outputs the second signal to the trip re-determination means 13.
The detection signal of is output and the interrupt signal is output. Note that FIG.
Is a flowchart in normal times, and FIG. 10 is a flowchart when a short-circuit current flows. On the other hand, the instantaneous trip determination circuit
When the interrupt signal from 9 is received, the short-circuit current re-determination unit binarizes the current value previously stored in the storage means with a predetermined threshold value R, and whether or not the counted value exceeds the limit value. judge. Then, when the counted value is equal to or more than the limit value and it is determined that the short-circuit current has flowed, the output circuit 16 outputs the trip signal to the trip circuit 10, the drive signal is output to the trip coil 11, and the contact point is output. Open 12

With such a structure, it is possible to make a double trip determination in a short time.

[0037]

According to the circuit breaker of the present invention, when the trip signal is output from the trip determining circuit or the instantaneous trip determining circuit, the contact is not immediately tripped, but trip redetermination means is provided. Since the determination is performed again in step 1, the accidental tripping of the contact is reduced, and the reliability of tripping the contact is improved.

The circuit breaker according to the second aspect of the invention has the effect of the first aspect, and the trip redetermination means is used to determine whether the output current of the first current transformer is in the trip state again. Since the same component such as the A / D conversion circuit can be used and the components can be shared by adopting the determination configuration, it contributes to downsizing and cost reduction.

In addition to the effect of claim 2, the circuit breaker according to claim 3 determines whether the DC offset voltage is a predetermined value by the voltage monitoring unit, and when the DC offset voltage is a predetermined value, the trip determination circuit. By making the re-determination, the accuracy of overcurrent detection is further improved by simple addition of components, so that the contact is further tripped more reliably as well as the size and cost are further reduced.

In addition to the effect of claim 1, the circuit breaker according to claim 4 can perform a short-time calculation by re-determining whether or not the short-circuit current has flowed with the current recorded in the storage means. Since the overcurrent detection accuracy can be improved, highly reliable high-speed trip can be performed.

[Brief description of drawings]

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

FIG. 2 is a waveform of a current flowing through the electric path.

FIG. 3 is a diagram showing an input voltage of the A / D conversion circuit.

FIG. 4 is a diagram showing an upper limit value and a lower limit value of the A / D conversion circuit.

FIG. 5 is a diagram showing an input voltage after passing through the A / D conversion circuit.

FIG. 6 is a flowchart of the circuit breaker.

FIG. 7 is a diagram showing an upper limit value and a lower limit value of an A / D conversion circuit showing a second embodiment of the present invention.

FIG. 8 is a diagram showing an input voltage after passing through the A / D conversion circuit.

FIG. 9 is a flowchart of the circuit breaker.

FIG. 10 is another flowchart of the circuit breaker.

FIG. 11 is a block diagram of a circuit breaker showing a conventional example.

FIG. 12 is a flowchart of the circuit breaker.

FIG. 13 is another flowchart of the circuit breaker.

[Explanation of symbols]

 1 Electric circuit 2 1st current transformer 3 2nd current transformer 4 Current-voltage conversion circuit 5 DC offset power supply circuit 6 A / D conversion circuit 7 Integration circuit 8 Tripping judgment circuit 9 Instantaneous trip judgment circuit 10 Tripping circuit 11 Tripping coil 12 Contact 13 Tripping re-determination means 15 Voltage monitoring unit 16 Output circuit

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[Procedure amendment]

[Submission date] August 3, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

More specifically, in the former case, the alternating current in the electric circuit 1 is detected by the first current transformer 2, and the current-voltage conversion circuit 4 is detected.
Converted to AC voltage by DC offset power supply circuit
The DC offset of 5 raises it to the + side,
Convert. Then, the DC voltage is converted into a digital value by the A / D conversion circuit 6, and the digital value is integrated for a predetermined time by the integration circuit 7, and it is determined by tripping that the integrated value exceeds a predetermined reference value. When detected by circuit 8, trip circuit
Send trip signal to 10. A flowchart showing the algorithm at that time is as shown in FIG. In the latter case, when the second current transformer 3 detects the short-circuit current flowing in the electric circuit 1 and the instantaneous trip determination circuit 9 determines that there is a short circuit,
The program is interrupted according to the flowchart including the algorithm shown in FIG. 13, and the trip signal is transmitted to the trip circuit 10.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The current-voltage conversion circuit 4 converts the AC current output from the first current transformer 2 into an AC voltage, adds a DC offset to the positive side, and converts the AC voltage into a DC voltage. Specifically, the AC current is converted to a voltage value via a resistor and the DC offset power circuit 5 outputs 2.5.
Add a DC offset of v and raise to the + side to obtain a DC voltage
Convert to. The output waveform of the current-voltage conversion circuit 4 is shown in FIG. Further, another output of the DC offset power supply circuit 5 is input to the A / D conversion circuit 6 described later.

Claims (4)

[Claims] 1. A first current transformer and a second current transformer for detecting a current flowing in an electric circuit, a current-voltage conversion circuit for converting an output current of the first current transformer into a DC voltage by a DC offset, and A / D conversion circuit that divides a DC voltage into a digital value by dividing it with a predetermined time width, an integrating circuit that squares a digital value and integrates it for a predetermined period, an integrated value of the integrating circuit and a predetermined reference value And a trip determination circuit that outputs a trip signal when in the trip state, and an instantaneous trip circuit that outputs a trip signal when the output current of the second current transformer is input and the trip state is instantaneous. A judgment circuit, and a trip circuit that outputs a drive signal when the trip signals of both judgment circuits are input,
In a circuit breaker having a trip coil that drives a contact that opens and closes an electric path when a drive signal is input, a trip signal of the trip determination circuit or the instantaneous trip determination circuit is provided in a stage before the trip circuit. Is input, the circuit breaker is further provided with tripping redetermination means for performing determination again from the output current of the first or second current transformer and outputting a tripping signal. 2. The trip re-determination means determines whether or not the output current of the first current transformer at that time is in the trip state immediately when the first trip signal is input. The circuit breaker according to claim 1, wherein the circuit breaker is configured to output a trip signal to the trip circuit when the trip determination circuit outputs the trip signal again. 3. The trip redetermination means determines whether the DC offset voltage has a predetermined value, and when the DC offset voltage has the predetermined value, determines whether the output current of the first current transformer is in the trip state. The circuit breaker according to claim 2, further comprising a voltage monitoring unit configured to make a judgment by a circuit. 4. The trip re-determination means is provided with a storage means for storing the output current of the first current transformer for a predetermined time,
Immediately after the first trip signal is input, the output current stored in the storage means is converted into a binarized pulse based on a predetermined value, and the sum of one of the binarized pulses reaches a predetermined number. 2. The circuit breaker according to claim 1, wherein the circuit breaker is configured to output a trip signal to the trip circuit when it is determined that the trip circuit is in an instantaneous trip state.