JPH11273534A - Automatic high-speed current limiting device for circuit breaking - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic high-speed current-limiting device which easily limits and breaks a current even in a low-voltage circuit such as an electric light wire circuit, and which can be realized by a simple constitution at a low price and in small size. SOLUTION: Normally, resistance of PTC 13 is sufficiently lower than resistance of a resistor 12, therefore a circuit current is flowed through the PTC 13 and CP 11. However, when a short-circuited current Is is generated, the current flowed in the PTC 13 is increased, and the temperature of the PTC 13 is rapidly heightened. Consequently, the resistivity of the PTC 13 is increased, and the PTC 13 is shifted at once from a low-resistive state of several mΩ to a high-resistive state of MΩ order. Therefore, the short-circuited current Is is commutated to the resistor 12 set in parallel to the PTC 13, and it is limited by the resistance of the resistor 12. The CP 11 shuts off the limited short-circuited current Is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic high-speed current limiting device for interrupting a circuit, which automatically limits a fault current, which is interrupted by a circuit interrupter, at a high speed.

[0002]

2. Description of the Related Art Conventionally, as a high-speed current limiting device of this kind,
For example, there is a current limiting device used in the DC high-voltage circuit shown in FIG. This current limiting device includes a resistor 1 inserted in a DC high-voltage circuit, a circuit breaker 2 connected in parallel to the resistor 1, and a command device 3 for operating the circuit breaker 2. . The command device 3 is connected to a current sensor 4 for detecting the magnitude of the current flowing in the DC high-voltage circuit.
A circuit breaker 5 is connected to the resistor 1 in series.

In such a configuration, since the resistance of the circuit breaker 2 is smaller than the resistance of the resistor 1, the circuit current flows through the circuit breaker 2 and the circuit breaker 5 in a steady state.
In the event of an extreme short circuit current I _{S in the} circuit,
The current sensor 4 quickly detects the occurrence of this fault current,
The command device 3 causes the circuit breaker 2 to shut off. As a result, the short-circuit current _IS is commutated to the resistor 1 provided in parallel with the circuit breaker 2, and the current is limited by the resistance of the resistor 1. Thus, the elongation of the peak value of the short-circuit current I _S is suppressed, the responsibility of the circuit breaker 5 is reduced. That is, the short-circuit current I interrupted by the circuit breaker 5
The size of _S becomes smaller, and it is sufficient to cut off the current of small energy.

[0004] the resistance value of the resistor 1, use what breaker each circuit breaker 2,5, is determined by what size the short-circuit current I _S of the circuit.

[0005]

However, in the conventional high-speed current limiting device described above, the circuit used is a high-voltage circuit,
The device configuration is extensive. Therefore, even if it is intended to perform the current limiting interruption as described above in a low voltage circuit such as a power line circuit, the device configuration cannot be applied as it is.

Further, the circuit breaker 2 for commutating the short-circuit current to the resistor 1 needs to be operated by remote control of the command device 3. Therefore, the above-mentioned conventional high-speed current limiting device has a configuration requiring a number of components even in a circuit configuration.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is intended to connect an accident current to a current value equal to or less than the current interrupting capability of the circuit interrupting device in series with the circuit interrupting device. An automatic high-speed current limiting device for circuit interruption was constructed from a current-limiting resistor and a thermistor connected in parallel with the resistor and having a resistivity that increases with an increase in temperature.

In this configuration, the circuit current normally flows through the thermistor and the circuit cutoff means. However, when an accident current occurs, the current flowing through the thermistor increases, and the temperature of the thermistor rises. As a result, the resistivity of the thermistor increases, and the fault current is commutated to a resistor provided in parallel with the thermistor. The fault current commutated to the resistor is limited by the resistance of the resistor, and the circuit interrupting means cuts off the limited fault current.

Therefore, the current limiting device is simply constituted only by the resistor and the thermistor. Further, the thermistor for commutating the fault current to the resistor operates automatically by itself without giving a signal from outside as in the prior art.

Further, the present invention is characterized in that a plurality of the resistors are connected in series, and the thermistor is connected to each of the resistors in parallel.

According to this configuration, the magnitude of the voltage applied from the power supply to each thermistor is reduced, and a thermistor with a small voltage rating can be used.

Further, the present invention is characterized in that a varistor is connected in parallel to the thermistor.

According to this configuration, the varistor prevents an excessive voltage from being applied to the thermistor.

Further, the present invention is characterized in that a capacitor is connected in parallel to the thermistor.

According to this configuration, when a voltage having a large time rate of change is applied to the thermistor, and the resistivity of the thermistor is increased by the current flowing by applying the voltage, the capacitor connected in parallel to the thermistor conducts, The large current flowing through the increased thermistor commutates to the resistor and some of it bypasses the capacitor. The current flowing through the capacitor flows into the thermistor that has not yet increased the resistivity, and promotes the temperature rise of the thermistor. Further, according to this configuration, harmonic noise applied to the thermistor is removed by the capacitor.

Further, the present invention is characterized in that a varistor and a capacitor are connected in parallel to the thermistor.

According to this configuration, the varistor prevents an excessive voltage from being applied to the thermistor, the capacitor promotes the temperature rise of the thermistor whose resistivity is not increased, and eliminates the harmonic noise. Is done.

[0018]

Next, a first embodiment of an automatic high-speed current limiting device for circuit interruption according to the present invention will be described.

FIG. 1 is a circuit diagram showing the configuration of the automatic high-speed current limiting device according to the present embodiment. The automatic high-speed current limiting device includes a circuit protector (CP) 11 that constitutes a circuit breaking unit.
And a positive temperature coefficient thermistor (PTC) 13 connected in parallel to the resistor 12. CP11 is a contact 11 for opening and closing the circuit
a and a current trip element 11b for tripping the contact 11a which is closed. The resistance value of resistor 12 is set to a value that limits the fault current to a current value equal to or less than the current interrupting capability of CP11.

The PTC 13 is made of a conductive polymer, and its resistivity increases as the temperature rises.
That is, the conductive polymer is obtained by mixing a conductive substance such as carbon with an insulating polymer such as polyolefin or fluororesin. Due to the conductive material present in the polymer, there are countless conductive paths in the PTC 13
Are formed and exhibit a low resistance value at normal temperature.
However, when the polymer thermally expands as the temperature increases, the distance between the conductive materials increases, the conductive paths are gradually cut, and the resistivity increases. Utilizing this property, PTC
Reference numeral 13 functions as an overcurrent protection element.

In such a configuration, normally, P
Since the resistance of TC13 is sufficiently lower than the resistance of resistor 12, the circuit current is flowing through PTC13 and CP11. However, when the short-circuit current I _S is generated PTC
13, the current flowing through the PTC 13 increases, and the PTC 13 sharply increases its temperature. As a result, the resistivity of the PTC 13 increases, and the PTC 13 instantaneously trips from a low resistance state of several mΩ to a high resistance state of the order of MΩ. Therefore, the short-circuit current I
_At an extremely early stage, _S commutates to the resistor 12 provided in parallel with the PTC 13, and the current is limited by the resistance of the resistor 12.

For example, as shown in the graph of FIG. 2, the short-circuit current I _S rising to the peak value I ₀ is immediately limited to the peak value I _m (<< I ₀ ) by the resistance of the resistor 12. .
The horizontal axis of the graph is time [t], and the vertical axis is current [I]. Therefore, the CP 11 only needs to cut off the short-circuit current I _S which is limited, and the duty of the CP 11 is reduced.
CP11 is connected to the contact 11 by the current trip element 11b.
Since the opening a is mechanically opened, the opening speed of the contact point 11a is low, and the current limiting performance cannot be expected with CP alone.
However, according to the present embodiment described above, the combined use of automatic current limiting device electronically speed operation, flowed rapidly limited short-circuit current I _S is the time the CP11 to operate late, as described above Current limiting cutoff can be easily performed. Therefore, according to the current limiting device according to the present embodiment, C
It becomes possible to interrupt a large-capacity fault current that cannot be interrupted by P alone.

The fault current limiting device includes a resistor 12 and P
It is simply configured with only TC13. Further, the PTC 13 for commutating the fault current to the resistor 12 automatically operates by itself without giving a signal from outside as in the conventional case. Therefore, the current limiting device is configured to be small and inexpensive, can be easily applied to a low-voltage circuit, and can be built in a device.

Further, according to the present embodiment, the fault current is quickly limited and cut off, so that the magnitude I ² t of the current energy flowing through the circuit is suppressed. Therefore, even if a semiconductor element is used in the circuit, it is possible to cut off the fault current without damaging the semiconductor element.
The conventional configuration without the high-speed automatic current limiting device according to the present embodiment, that is, due to the mechanical operation delay of the CP alone,
Large current energy flows in the circuit, and it has not been possible to protect a semiconductor element in this way.

When a distribution board has a large number of CPs and NFBs (no-fuse breakers), if the current limiting device according to the present embodiment is provided alongside one of the CPs and NFBs,
And NFB block the fault current by current limiting, so that it is possible to selectively cut off. In other words, C with current limiting device
P and NFB operate faster than CPs and NFBs without a current limiting device because they block the fault current at a smaller peak value than CPs and NFBs without a current limiting device. That is,
If a fault current occurs, the CP with current limiting device
CP which operates NFB preferentially and has no current limiting device,
It is possible to selectively cut off the NFB so as not to operate. Therefore, C that supplies power to less important devices
By providing a current limiting device in parallel with P and NFB and operating these circuit breakers preferentially when an accident current occurs, power can be continuously supplied to important devices to the end. .

Next, an automatic high-speed current limiting device for interrupting a circuit according to a second embodiment of the present invention will be described.

FIG. 3 is a circuit diagram showing the configuration of the automatic high-speed current limiting device according to the present embodiment. The automatic high-speed current limiting device according to the present embodiment includes three resistors 12 a to 12
2c are connected to each of these resistors 12a to 12c.
Are connected in parallel with each other. The combined resistance value of the three resistors 12a to 12c is CP
The current value is set to a value that limits the fault current to a current value equal to or lower than the current interrupting capability of No. 11.

By connecting the PTCs 13 in series as in this embodiment, the circuit power supply voltage shared by one PTC 13 is reduced. Therefore, according to this configuration, a current limiting device can be realized using the PTC 13 having a low rated voltage. For example, when the present device is applied to a low-voltage distribution line circuit of 100 [V], for example, three PTCs 13 having a rated voltage of 30 [V] may be used in series.

Even in such a configuration, usually,
Circuit current is flowing through the series circuit of PTC 13 and CP11. However, when the short-circuit current I _S is generated PTC
13 increases, and any one of the PTCs 13
First raises its temperature rapidly. Therefore, the P
The resistivity of TC13 increases and the short-circuit current I _S
The current is commutated to the resistor 12 provided in parallel with C13. Therefore, the cut-off voltage waveform in the graph of FIG.
As shown in the cut-off current waveform graph, the short-circuit current I _S is limited flowed at a very early time t1. Here, the horizontal axis of each of these graphs is time [t], the vertical axis of the graph of (a) is voltage [V], and the vertical axis of the graph of (b) is current [I].

[0030] Following this, the other one PTC13 also raised the temperature becomes in a high resistance state, the short-circuit current I _S is then high became resistance state this PTC13 a resistor connected in parallel to the 12 To commutate. Therefore, at time t2, two resistors 12 are inserted into the circuit, and the short-circuit current I _S becomes equal to time t2.
Is further current-limited. Following this, the remaining one PTC 13 also raises its temperature to a high resistance state,
Short-circuit current I _S this was in a high resistance state in the last PTC1
3 commutates to the resistor 12 connected in parallel with the resistor 3. Therefore,
At time t3, all three resistors 12 are inserted into the circuit,
Short-circuit current I _S is further limited flowed at time t3.

As a result, the short-circuit current I _S is quickly limited by the combined resistance of the resistors 12, and the CP 11 interrupts the limited short-circuit current I _S with a delay at time t4.

Therefore, also with the automatic high-speed current limiting device according to the present embodiment, the short-circuit current _IS is subjected to the current limiting interruption, and the same effect as that of the first embodiment is obtained.

Next, an automatic high-speed current limiting device for interrupting a circuit according to a third embodiment of the present invention will be described.

FIG. 5 is a circuit diagram showing the configuration of the automatic high-speed current limiting device according to the present embodiment. The automatic high-speed current limiting device according to the present embodiment includes PTCs 13a to 13c in parallel with three resistors 12a to 12c connected in series to CP11.
c and varistors (ZNR) 14a to 14c are connected. Also in the present embodiment, the three resistors 12 a to 12
The combined resistance value of 12c is set to a value that limits the fault current to a current value equal to or less than the current interrupting capability of CP11.

By connecting the varistor 14 in parallel with the PTC 13 as in this embodiment, an excessive voltage
It doesn't cover C13. That is, the resistor 12 causes the PTC 13 to linearly increase the voltage V with respect to the increase in the circuit current I as shown by the straight line 21 in the graph of FIG.
It takes. Here, the horizontal axis of the graph is a logarithmic representation of the circuit current I, and the vertical axis is a logarithmic representation of the inter-terminal voltage V of the PTC 13. Further, the voltage V is applied to the PTC 13 by the varistor 14 as the circuit current I increases, as shown by the curve 22 in the graph. For this reason, in the present embodiment, P
The voltage V is applied to the TC 13 with the characteristic shown by the curve 23 indicated by the thick solid line.

That is, the resistor 12 is connected in parallel with the PTC 13.
When only the PTC 13 is connected, the voltage is linearly applied to the PTC 13 in accordance with the increase in the fault current.
3 and a varistor 14 is connected in parallel
The extension of the voltage applied to the TC 13 is suppressed. Therefore, according to the current limiting device according to the present embodiment, when an accident current occurs, P
Excessive voltage is not applied to TC13, and PTC
13 is prevented from being destroyed.

Even in the current limiting device according to the present embodiment, the circuit current normally flows through the series circuit of the PTC 13 and the CP 11. However, the current flowing through the PTC13 the short-circuit current I _S is generated is increased, PT
C13 sharply increases its temperature. As a result, PT
The resistivity of the C13 is increased, the short-circuit current I _S is, PTC13
Is commutated to a resistor 12 provided in parallel with the resistor 12, and the current is limited by the resistance of the resistor 12. Thus, CP11 interrupts the short-circuit current I _S that flows limited. At this time, as described above, application of an excessive voltage to the PTC 13 by the varistor 14 is prevented.

Therefore, also with the automatic high-speed current limiting device according to the present embodiment, the short-circuit current _IS is subjected to the current limiting interruption, and the same effect as that of the above-described first embodiment is exerted.

Next, an automatic high-speed current limiting device for interrupting a circuit according to a fourth embodiment of the present invention will be described.

FIG. 7 is a circuit diagram showing the configuration of the automatic high-speed current limiting device according to the present embodiment. The automatic high-speed current limiting device according to the present embodiment includes PTCs 13a to 13c in parallel with three resistors 12a to 12c connected in series to CP11.
c and the capacitors 15a to 15c are connected.
Also in the present embodiment, the combined resistance value of the three resistors 12a to 12c is set to a value that limits the fault current to a current value equal to or less than the current interrupting capability of CP11.

By connecting the capacitor 15 in parallel with the PTC 13 as in the present embodiment, the temperature rise of the PTC 13 is promoted, and the PTC 13 operates quickly. That is, a voltage having a large time change rate, for example, 0
A voltage that rapidly rises from [V] is applied to the PTC 13, and when the resistivity of any of the PTCs 13, for example, the PTC 13a increases, the capacitor 15a conducts. Therefore, a large current flowing through the PTC 13a whose resistivity has been increased is commutated to the resistor 12a, and a part of the commutated current is bypassed to the capacitor 15a. The current flowing through the capacitor 15a depends on the PTCs 13b and 13
c to promote the temperature rise of the PTCs 13b and 13c. Therefore, the remaining PTCs 13b and 13c also operate sequentially and immediately after the PTC 13a that trips earlier.

Further, according to this configuration, the harmonic noise applied to the PTC 13 is removed by the capacitor 15, and if a large harmonic noise is applied to the PTC 13, the overvoltage is absorbed by the capacitor 15 to prevent the PTC 13 from being destroyed. Is done.

Also, in this configuration, at the time of normal operation,
The circuit current flows through the series circuit of the PTC 13 and the CP 11, but when the short-circuit current I _S occurs, the resistivity of the PTC 13 increases, and the short-circuit current I _S is limited by the resistance of the resistor 12. Therefore, even by automatic high-speed current-limiting device according to the present embodiment, the short-circuit current I _S is cut off current limiting,
The same effects as those of the first embodiment are provided.

Next, an automatic high-speed current limiting device for interrupting a circuit according to a fifth embodiment of the present invention will be described.

FIG. 8 is a circuit diagram showing the configuration of the automatic high-speed current limiting device according to the present embodiment. The automatic high-speed current limiting device according to the present embodiment includes PTCs 13a to 13c in parallel with three resistors 12a to 12c connected in series to CP11.
c, varistors 14a to 14c and capacitors 15a to
15c is connected. Also in the present embodiment, the combined resistance value of the three resistors 12a to 12c is set to a value that limits the fault current to a current value equal to or less than the current interrupting capability of CP11.

When the varistor 14 and the capacitor 15 are connected in parallel to the PTC 13 as in this embodiment,
The varistor 14 causes an excessive voltage proportional to the current to PT
C13 is prevented from being applied to
5 promotes the temperature rise of the PTC 13 and
Harmonic noise is removed.

In such a configuration, the circuit current is normally controlled by the series circuit of the PTC 13 and the CP1.
While flowing through the 1, short-circuit current I _S is generated when PT
Resistivity of C13 increases, the short-circuit current I _S is limited flows through resistance of the resistor 12. Therefore, the same effect as that of the above-described first embodiment can be obtained by the automatic high-speed current limiting device according to the present embodiment.

In the first embodiment described above, the case where the PTC 13 is simply connected in parallel with the resistor 12 has been described.
4 and the capacitor 15 may be connected. According to such a configuration, effects similar to those of the second to fifth embodiments can be obtained.

Further, in the above-described second to fifth embodiments, the case where three resistors 12 are connected in series has been described, but the number of resistors 12 connected in series is not limited to this. is not. Further, in each of the embodiments described above, the case where the CP is used as the circuit interrupting means connected in series to the resistor 12 has been described.
May be used instead of NFB. Further, a non-contact semiconductor switch having no contact, for example, an element such as a power transistor (PT), a gate turn-off thyristor (GTO), or an IGBT may be used as the circuit breaking means. Further, the current limiting device according to each of the above-described embodiments can be applied to an AC circuit and a DC circuit. In each of these cases, the same effects as those of the above embodiments can be obtained.

[0050]

As described above, according to the present invention, the current limit interruption can be easily performed even in a low voltage circuit such as a power line circuit. Moreover, the current limiting device does not need to be remotely controlled as in the related art, and can be realized at a low cost and small size with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an automatic high-speed current limiting device for interrupting a circuit according to a first embodiment of the present invention.

FIG. 2 is a graph showing a waveform of a short-circuit current limited by the automatic high-speed current limiting device for circuit interruption according to the first embodiment.

FIG. 3 is a circuit diagram showing an automatic high-speed current limiting device for interrupting a circuit according to a second embodiment of the present invention.

FIG. 4 is a graph for explaining an operation of the automatic high-speed current limiting device for circuit interruption according to the second embodiment.

FIG. 5 is a circuit diagram showing an automatic high-speed current limiting device for circuit interruption according to a third embodiment of the present invention.

FIG. 6 is a graph showing a relationship between a voltage applied to a PTC and a circuit current in an automatic high-speed current limiting device for circuit interruption according to a third embodiment.

FIG. 7 is a circuit diagram showing an automatic high-speed current limiting device for circuit interruption according to a fourth embodiment of the present invention.

FIG. 8 is a circuit diagram showing an automatic high-speed current limiting device for interrupting a circuit according to a fifth embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional high-speed current limiting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Circuit protector (CP) 11a ... Contact of CP11 11b ... Current release element of CP11 12 ... Resistor 13 ... Positive thermistor (PTC) 14 ... Varistor 15 ... Capacitor

Claims (5)

[Claims] A resistor connected in series to the circuit interrupting means for limiting the fault current to a current value equal to or less than a current interrupting capability of the circuit interrupting means; An automatic high-speed current limiting device for circuit cut-off composed of a thermistor whose resistivity increases. 2. The automatic high-speed current limiting device for interrupting a circuit according to claim 1, wherein a plurality of said resistors are connected in series, and said thermistor is connected in parallel to each of said resistors. 3. The automatic high-speed current limiting device for interrupting a circuit according to claim 1, wherein a varistor is connected in parallel with said thermistor. 4. The capacitor according to claim 1, wherein a capacitor is connected in parallel to said thermistor.
3. The automatic high-speed current limiting device for circuit cut-off according to 1). 5. The automatic high-speed current limiting device for circuit interruption according to claim 1, wherein a varistor and a capacitor are respectively connected in parallel to said thermistor.