JP2003125532A - Tracking breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct shutdown operation by detecting tracking short-circuit, without causing malfunction by load current or rush current, even if a plurality of household electrical appliances are used concurrently. SOLUTION: In a determination circuit 5, current information of a cable run detected by a current transformer 1 and voltage information of the cable run, detected by a voltage detection circuit 3, are inputted. A calculation circuit 8 compares the peak value for each half period, determines it as tracking short- circuit if a condition, where the variance in the peak value exceeds 5 amperes in current and a voltage variance exceeds 5 volts occurs 10 times continuously, and outputs the operating current of a tripping circuit 7 from an output circuit 11, to make a tripping coil 6 operate and operate a contact 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking breaker that cuts off a tracking short circuit, and more particularly to an improvement in a tracking short circuit detection method.

[0002]

2. Description of the Related Art A conventional tracking breaker tracking short-circuit detecting method capable of interrupting an electric circuit by detecting a tracking short-circuit occurring intermittently due to a short-circuit in an outlet circuit or a defective connection cord is shown in FIG. explain.
In FIG. 4, I is a current waveform and V is a voltage waveform. Conventionally, the current and the voltage of the electric circuit connecting the breaker are constantly monitored, and the current value is within a preset voltage phase range and a predetermined low threshold value. Of the two thresholds of S1 and the high threshold S2, the low threshold S1 is exceeded, and the current peak value continuously increases for three cycles or more as shown by P1, P2, and P3 in FIG. 4A, or Of the arbitrary two cycles, the threshold value S2 set higher in the first cycle is exceeded, and becomes lower than the threshold value S1 set low in the second cycle.
In the case of Q2, it was determined that a tracking short circuit had occurred and the cutoff operation was performed.

[0003]

However, in order to detect a short circuit current having a relatively small value such as a tracking short circuit, it is necessary to keep the threshold value small. If multiple home appliances are turned on at the same time, they may malfunction due to inrush current or increased load current. Further, when a plurality of home electric appliances are used at the same time, the change in the detected current value may be similar to that in tracking, and the occurrence of tracking short-circuit current may not be accurately detected. In view of the above problems, it is an object of the present invention to provide a tracking breaker that does not malfunction even if a plurality of home electric appliances are used at the same time due to a load current or an inrush current.

[0004]

In order to solve the above-mentioned problems, the invention of claim 1 incorporates a current detecting means and a voltage detecting means for detecting the current and voltage of an electric circuit, and a CPU, and the current detecting means and A determination circuit for determining a tracking short circuit by receiving the current waveform information and the voltage waveform information from the voltage detection means, and a trip circuit for tripping with an output signal from the decision circuit. When the difference between the current peak value and the voltage peak value of the two waves is calculated, and the number of times the calculated values exceed a predetermined value occurs a predetermined number of times within a predetermined time, a tracking short circuit is generated. It is judged that the operation signal of the trip circuit is outputted.

According to a second aspect of the present invention, in the first aspect of the present invention, the predetermined time is set to 8 times to 40 times the cycle of the input wave of the judgment circuit, during which the difference between the current peak value and the voltage peak value is predetermined. It is characterized in that it is determined that a tracking short circuit has occurred when the number of times exceeding the value occurs 8 to 20 times.

According to a third aspect of the present invention, in the invention according to the first or second aspect, the rectified waveform is used as a determination circuit input signal, and the determination circuit calculates a peak value difference every half cycle time of the circuit current and circuit voltage. It is characterized by executing.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a circuit block diagram showing an example of a tracking breaker according to the present invention, wherein 1 is a current transformer that detects the current in the electric path 12, 2 is a current-voltage conversion circuit, and 3 is a voltage detection circuit that detects the electric path voltage. Reference numeral 4 is a rectifier circuit, and 5 is a determination circuit. The current information of the electric circuit obtained by the current transformer 1 is converted into a voltage by the current-voltage conversion circuit 2 and then rectified and input to the determination circuit. The voltage detection circuit 3 detects the electric circuit voltage, rectifies it in the same manner as the current, and inputs it to the determination circuit. Further, 13 is a contact for connecting / disconnecting the electric path, 6 is a trip coil for tripping and operating the contact,
Reference numeral 7 is a trip circuit for operating the trip coil.

The determination circuit 5 has an arithmetic circuit 8 composed of a CPU, is provided with an A / D conversion I / O port 9 to which current / voltage information is input, a register 10 and an output circuit 11, and provides current information and voltage of the electric circuit. When a predetermined current change and voltage change set in advance from information occur, it is determined that tracking has occurred, and a trip circuit operation signal is output.

The specific operation of the determination circuit 5 will be described. Here, the determination operation is performed based on the following two criteria, and if either one of the criteria is satisfied, it is determined to be a tracking short circuit. First, FIG. 2 is a waveform diagram for explaining the operation according to the first determination criterion. FIG. 2A is a determination circuit input current waveform, and FIG.
Indicates a judgment circuit input voltage waveform. The judgment circuit A / D-converts the input current waveform and voltage waveform with a sampling time of, for example, 0.25 ms, and divides the data into a preset first time (for example, commercial frequency). Half cycle 10ms) T
1, the peak current value and the peak voltage value of each waveform are constantly detected, the current peak value and the peak value of the immediately preceding first set time T1 are compared, and the current fluctuation amount ΔI and the voltage fluctuation amount ΔV, which are the differences between them, are compared. Is calculated.

A state in which the current fluctuation amount ΔI and the voltage fluctuation amount ΔV thus obtained exceed preset predetermined values Is and Vs (for example, current 5 amperes and voltage 5 volts) by sequentially performing this calculation for each input waveform. If a predetermined number of times (for example, 10 times) occurs continuously during a second set time (for example, 100 ms) T2 set in advance, it is determined that a tracking short circuit has occurred, and a trip circuit operation signal is output.

If the predetermined number of times has not occurred in the second set time T2, that is, if the variation amount of the current or the voltage is less than the predetermined value, the determination process is reset at that point and the value exceeding the predetermined value is exceeded. Current variation ΔI, voltage variation Δ
Restart V counting. For example, in the waveform of the section A shown in FIG. 2 which is a section of one cycle of the electric circuit waveform, the voltage fluctuation amount ΔV exceeds the predetermined value Vs, but the current fluctuation amount ΔI is smaller than the predetermined value Is, so the determination process is reset. To be done.
Further, in the section B, the current fluctuation amount ΔI exceeds the predetermined value Is, but since the voltage fluctuation amount ΔV is smaller than the predetermined value Vs, the determination process is reset. The current fluctuation amount ΔI and the voltage fluctuation amount ΔV are absolute values of the difference between adjacent waveform peak values.

FIG. 3 is an explanatory diagram of the operation based on the second criterion, and the second set time T2 is 300 for three consecutive sections.
When ms is the third set time T3, this third set time T3
Between the current fluctuation amount ΔI and the voltage fluctuation amount ΔV are predetermined values Is,
If the number of times Vs is exceeded occurs 10 times, it is determined that a tracking short circuit has occurred. For example, as shown in FIG.
In the section of the third set time T3, the number of times that the current fluctuation amount ΔI and the voltage fluctuation amount ΔV exceed the predetermined values Is and Vs is 7 times and 10 times, respectively.
If the number of times is less than the number of times, it is determined that there is no tracking short circuit, the data of the first second set time T2 is deleted, and a predetermined unit time T3 shown in FIG. Based on this count, the current variation ΔI and the voltage variation Δ
If the number of times V exceeds the predetermined values Is and Vs is 10 or more, it is determined that a tracking short circuit has occurred. It should be noted that the current fluctuation amount ΔI and the voltage fluctuation amount ΔV within the predetermined time are the predetermined values Is and Vs.
The number of times described above is stored in the register.

As described above, when the tracking short circuit is detected, the first, second, and third set times are set as the predetermined time based on the fluctuation amounts of the current and the voltage.
Even if the magnitude of the current flowing due to the tracking short circuit is less than the current at which a normal circuit breaker operates, it is possible to determine the tracking short circuit in a short time, and there is no malfunction in the load current or the inrush current of home electric appliances. In addition, even if you use multiple home appliances at the same time, it is possible to detect the fluctuation of the current that is peculiar to the tracking short circuit, and reliably identify the tracking short circuit.
The shutoff operation can be performed without malfunction. Further, if the number of times the amount of fluctuation exceeds a predetermined value occurs 10 times in a row,
Since it is immediately determined that a tracking short circuit has occurred, a quick interruption operation can be performed according to the waveform information, and since the difference between peak values is calculated by rectification every half cycle, it can be determined in a shorter time.

In the above embodiment, the sampling time is 0.25 ms, the first setting time is 10 ms, the second setting time is 100 ms, and the third setting time is 300 ms. However, the shorter the sampling time, the more accurate the sampling accuracy. It is preferable that the first set time is one cycle of the determination circuit input waveform. In addition, the second set time is preferably set according to the first determination criterion, and for example, when the determination criterion for the number of times the amount of fluctuation continuously exceeds a predetermined value is shortened to exceed the set value eight consecutive times. The tracking short circuit may occur, and in that case, the second set time is preferably set to 80 ms. Further, it is convenient to set the third set time as an integral multiple of the second set time, and particularly preferably 2 to 4 times. From the above, it is preferable that the tracking short-circuit determination time is 8 to 40 times the input wave period. Further, the number of times the variation amount exceeds the predetermined value within the third set time may be equal to or more than the set number of times in the second set time, and is preferably 8 times (set number of times in the second set time) to 20 times.

[0015]

As described above in detail, according to the inventions of claims 1 and 2, since the determination for detecting the tracking short-circuit is made based on the amount of change in the current and the voltage, the magnitude of the current flowing due to the tracking short-circuit is large. However, even if the current is less than the current at which a normal circuit breaker operates, it is possible to determine a tracking short-circuit in a short time, and there is no malfunction due to load current or inrush current of home appliances. Further, even if a plurality of home electric appliances connected to the electric circuit are used at the same time, when a tracking short circuit occurs, the tracking short circuit can be surely identified, and a disconnection operation without malfunction can be performed.

According to the invention of claim 3, claim 1 or 2
In addition to the above effect, the calculation of the peak value difference can be performed every half cycle, and the determination can be performed in a shorter time.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an example of an embodiment of a tracking breaker according to the present invention.

FIG. 2 is an explanatory diagram of a tracking short circuit determination operation,
(A) is a current waveform diagram and (b) is a voltage waveform diagram.

3A and 3B are explanatory diagrams of a tracking short circuit determination operation different from FIG. 2, where FIG. 3A shows a case where a tracking short circuit is not determined, and FIG. 3B shows a case where a tracking short circuit is determined.

FIG. 4 is an operation explanatory diagram of a conventional tracking breaker, in which (a) is a current waveform diagram and (b) is a voltage waveform diagram.

[Explanation of symbols]

1 ... Current transformer, 2 ... Current-voltage conversion circuit, 4 ... Rectifier circuit, 5 ... Judgment circuit, 6 ... Tripping coil, 7 ...
Tripping circuit, 8 ... Arithmetic circuit, 9 ... A / D conversion I /
O port, 10 ... Register, 11 ... Output circuit, T1
..First set time, T2..second set time, T3..third set time

Claims (3)

[Claims] 1. A current detection means and a voltage detection means for detecting a current and a voltage of an electric circuit and a CPU are built in, and a tracking short circuit is performed by receiving the current waveform information and the voltage waveform information from the current detection means and the voltage detection means. The determination circuit includes a determination circuit and a tripping circuit that trips with an output signal from the determination circuit. The determination circuit calculates a difference between current peak values and a voltage peak value of two adjacent waves. When the number of times the calculated value exceeds a predetermined value occurs a predetermined number of times within a predetermined time set in advance, it is determined that a tracking short circuit has occurred, and the operation signal of the trip circuit is output. Tracking breaker to do. 2. The predetermined time is 8 times as long as the period of the input wave of the judgment circuit.
The tracking breaker according to claim 1, wherein the tracking breaker is determined to be 40 times when the difference between the current peak value and the voltage peak value exceeds the predetermined value 8 to 20 times during that time. 3. The tracking breaker according to claim 1, wherein the rectified waveform is used as an input signal of the determination circuit, and the determination circuit executes the calculation of the peak value difference every half cycle time of the circuit current and the circuit voltage.