JPH04172915A - Earth leakage breaker - Google Patents

Abstract

PURPOSE:To give a characteristic adaptive to a malfunction preventing condition to an earth leakage breaker by amplifying a leak detecting signal as an AC signal and supplying the signal to a comparator after the signal is converted into a signal, the high-frequency component of which is lowered to have a characteristic lower than a desired level by means of a low-pass filter, and then, deciding the presence/absence of a leak. CONSTITUTION:When a leaking accident occurs, a zero-phase detecting current is converted into a leak detecting signal V1 and the signal V1 is impressed upon an amplifier 13 through terminal pins T1 and T2. The amplifier 13 supplies the signal V1 to a comparator 15 through a low-pass filter 21 composed of a resistance 14a and capacitor 14b after amplification. The comparator 15 outputs a decision output V2 when the signal V1 exceeds a reference value V0. The output V2 becomes square waves depending upon the characteristic of the comparing operation of the comparator and charges an integration capacitor 20. When the charged voltage of the capacitor 20 reaches a prescribed value, a tripping command signal S1 is outputted from a latch circuit 16 and a thyristor 10 is conducted. As a result, a tripping coil 7 is energized and a main contact 4 is opened.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an earth leakage breaker that protects the load by disconnecting the load from the power supply path when an earth leakage accident is detected. The present invention relates to an earth leakage breaker that can adjust the frequency characteristics of an earth leakage determination circuit for determining the presence or absence of earth leakage.

(Prior art) Usually, an earth leakage breaker has a main contact interposed in the load power supply path,
A zero-phase current transformer provided in the load power supply path, an earth leakage determination circuit that receives an earth leakage detection signal from the zero-phase current transformer and determines the presence or absence of an earth leakage, and a trip output from the earth leakage determination circuit. It consists of a tripping device that opens the main contact in response to a command signal, and in particular, the earth leakage determination circuit receives an earth leakage detection signal output from a zero-phase current transformer when an earth leakage accident occurs and uses this as a reference. A comparator that outputs a rectangular wave judgment signal when the value is greater than or equal to a reference value, an integrating capacitor that integrates the judgment signal from this comparator, and a terminal voltage of this integrating capacitor that indicates that the terminal voltage of this integrating capacitor has reached a predetermined value. It consists of a latch circuit that outputs a tripping command signal in response.

By the way, the following has been reported regarding the frequency characteristics of leakage current. In other words, the higher the frequency, the more difficult it is for the leakage current to pass through the human body, and the larger the current that causes ventricular fibrillation, which stops the heart's function.Furthermore, if you are using an inverter device, it is difficult to pass through the human body. A high frequency leakage current is generated. In light of this fact, it is preferable for the earth leakage breaker to have a characteristic in which the higher the frequency of the detection target electrical circuit, the more difficult it is to interrupt the circuit, that is, a frequency characteristic in which the higher the frequency, the larger the sensitivity current becomes.

(Problem to be Solved by the Invention) However, in the conventional earth leakage breaker as described above, if a method is adopted in which the frequency characteristics are adjusted by adjusting the value of the capacitor that integrates the rectangular wave judgment signal, for example, the capacitor When the capacitance is increased, the pulse width of the rectangular wave determination signal to which the latch circuit responds needs to be increased, and the sensitivity current, that is, the cutoff response current increases. At the same time, the time it takes for the latch circuit to operate becomes longer as the capacitor capacity increases, meaning that the cut-off response time becomes longer.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an earth leakage breaker that can set the characteristic of the sensitive current with respect to frequency without causing a change in the interruption response time.

[Structure of the Invention] (Means for Solving the Problems) The earth leakage breaker according to the present invention includes a main contact interposed in a load power supply path, a zero-phase current transformer provided in the load power supply path, and a zero-phase current transformer provided in the load power supply path. an earth leakage determination circuit that receives an earth leakage detection signal from the phase current transformer and determines whether there is an earth leakage; and a tripping device that opens the main contact in response to a tripping command signal output from the gA electric current determination port. In the earth leakage breaker, the earth leakage determination circuit includes an amplifier that receives the earth leakage detection signal and outputs a signal having a waveform similar to the earth leakage detection signal, a low-pass filter that receives the output signal from this amplifier, and a signal that has passed through the low-pass filter. An earth leakage breaker comprising a comparator for comparing with a reference value.

(Function) The earth leakage detection signal output from the zero-phase current transformer due to an earth leakage accident is amplified as an AC signal by an amplifier circuit, and then converted by a low-pass filter into a signal with high frequency components reduced to the desired characteristics. The current is supplied to a comparator, where the presence or absence of a leakage is substantially determined, and a predetermined frequency characteristic is given to the sensitivity current for interrupting operation. .

(Example) An example of the present invention will be described below with reference to FIGS. 1 and 2. To explain the overall configuration with reference to Figure 2, there are conductors connected between three power supply side terminals 1 and three load side terminals 2 corresponding to each of the three phases, that is, three loads. Each of the power supply paths 3 is provided with a main contact 4 and a zero-phase current transformer 5 . A tripping coil 7, which forms part of a tripping device for opening the main contact 4, is interposed on the AC input side of the rectifier circuit 6 to which a single-phase AC voltage is applied between the two load feed paths 3. , and a cyrisk 10 is connected between the DC output lines 8 and 9,
A smoothing capacitor 11b is connected in parallel with this thyristor 10 via a current limiting resistor 11a. The earth leakage determination circuit 12 for determining earth leakage accidents based on the output current from the zero-phase current transformer 5 is integrated, and its specific configuration is shown in FIG. 1, and outputs a waveform similar to the input waveform. It includes an AC amplifier 13, its two input terminals are connected to terminal bins TI and T2, its amplification adjustment terminal is connected to terminal bin T3, and its output terminal is connected to terminal bin T3 through a resistor 14a forming a part of a low-pass filter. It is connected to T4 and one input terminal of comparator 15, respectively. This comparator 1
5, the reference voltage Vo is applied to the other input terminal, and the output terminal is connected to the terminal bin T5 and the input terminal of the latch circuit 16, respectively.

The output terminal of the latch circuit 16 is connected to the gate of the thyristor 10 via a terminal bin T6. This earth leakage determination circuit 12 also includes a power supply circuit 17, which includes terminal bins T7 from both ends of the smoothing capacitor 11b.
．． A DC voltage is applied via T8. At this time, the current limiting resistor 11a limits the amount of current flowing into the power supply circuit 17.

On the other hand, a voltage conversion resistor 18 is connected between the output terminals of the current transformer 5.
is connected to the terminal pin T, and both ends of the voltage conversion resistor 18 are connected to the terminal pin T.
1. Between the terminal pin T8, which is connected to T2 and is also a ground terminal, and terminal pins T3, T4, and T5 are an amplification degree setting resistor]9, a filter capacitor 14b forming a part of a low-pass filter, and an integrator. capacitor 2
0 or connected respectively.

Next, the operation of the above configuration will be explained. Now, if an earth leakage accident occurs, the zero-phase current transformer 5 outputs a zero-phase detection current, which is converted by the current conversion resistor 18 into an earth-leakage detection signal V1 having a voltage value, and this earth-leakage detection signal V1 is sent to the terminal. Pin Tl.

The signal is applied to the amplifier 13 via the input terminal 12, amplified there, and then supplied to the comparator 15 via the low-pass filter 21 consisting of a resistor 14a and a capacitor 14b. This comparator 15 outputs a judgment output V2 when it judges that the supplied detection signal V1 has reached the protection operation target level (cutoff response level), that is, when it exceeds the reference value 0. This judgment output V2 forms a rectangular wave due to the characteristics of the comparison operation, and the integrating capacitor 20 is charged with this, and when the charging voltage reaches a predetermined value, the latch circuit 16 outputs a tripping command signal S1 and the thyristor 10 is conductive. As a result, the tripping coil 7 is energized and the main contact 4 is opened. In the earth leakage breaker of this embodiment, the earth leakage detection signal outputted from the amplifier 13 is input to the comparator 15 while being converted by the low pass filter 21 into an AC signal having a frequency spectrum with a reduced high frequency component. Therefore, the waveform of the rectangular wave of judgment output 2 output from the comparator 15 corresponds to the current voltage frequency of the load feed line 3, which is the feed line to be detected, and as a result, the latch circuit 16
The magnitude of the current detected by the zero-phase current transformer 5 that responds has a predetermined frequency characteristic, for example, the higher the frequency, the more difficult it is to be interrupted.
The magnitude of changes with frequency. In the earth leakage breaker of this embodiment, general adjustment unrelated to the frequency of the sensitivity current can be achieved by adjusting the amplification degree of the amplifier 14 by appropriately selecting the value of the amplification degree setting resistor 19. There is no need to change the value of voltage conversion resistor 18.

[Effects of the Invention] According to the present invention, the earth leakage detection signal output from the zero-phase current transformer due to an earth leakage accident is amplified as an AC signal by the amplifier circuit, and the high frequency component is converted to desired characteristics by the low-pass filter. It is converted into a reduced signal and supplied to a comparator, where it is essentially determined whether there is an earth leakage.As a result, the sensitivity current has a predetermined frequency characteristic that changes depending on the frequency, which helps protect the human body. It is possible to provide an earth leakage breaker having characteristics that meet the conditions and the conditions for preventing malfunction due to in-type failure, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an earth leakage determination circuit in one embodiment of the present invention, and FIG. 2 is a circuit diagram showing the overall configuration of an earth leakage breaker in the same embodiment. In the figure, 3 is the load power supply path, 4 is the main contact, 5 is the zero-phase current transformer,
7 is a tripping coil (tripping device), 12 is an earth leakage determination circuit, 13 is an amplifier, 15 is a comparator, and 21 is a low bass fino 1-. Agent Patent Attorney Tsuyoshi Sato

Claims (1)

[Claims] 1. A main contact interposed in the load power supply path, a zero-phase current transformer provided in the load power supply path, and an integrated circuit that receives a leakage detection signal from the zero-phase current transformer and determines whether there is a leakage. In the earth leakage circuit breaker, the earth leakage breaker is composed of an earth leakage determination circuit that is configured as a circuit, and a tripping device that opens the main contact in response to a tripping command signal output from the earth leakage determination circuit. It is characterized by comprising an amplifier that outputs a signal with a waveform similar to the received signal, a low-pass filter that receives the output signal from the amplifier, and a comparator that compares the signal that has passed through the low-pass filter with a reference value. earth leakage breaker.