JPH06245364A - Ground fault detector - Google Patents

Abstract

PURPOSE:To suppress erroneous function due to external noise, e.g. lightning, different from normal ground fault or leak while enhancing leak detection accuracy. CONSTITUTION:When the peak voltage of a leak signal exceeds reference values 1-5 of comparators 21-25, positive and negative level decision units 20, 30 produce output signals. When the data of the output signal exceeds each reference level, an adder 40 adds the data and produces an output signal (carry signal) when the sum reaches a predetermined value. A pulse count circuit 50 counts the output signal and produces an OUT signal when three output signals are counted. When the OUT signal is produced, a thyristor 6 is operated to break an AC circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting device for shutting off an AC line when a ground fault occurs in the AC line.

[0002]

2. Description of the Related Art Conventionally, when a ground fault occurs in an AC electric line, a ground fault detecting device that cuts off the AC line has a ground fault component of a zero-phase current transformer that detects the ground fault and has a predetermined magnitude or more. At this time, the switching element is operated, but a flip-flop is used in the signal width detecting device for the ground fault component, and a signal obtained by detecting the level of the leakage signal is used as the trigger signal.

FIG. 6 shows a block diagram of a conventional ground fault detecting device, which is described in Japanese Patent Application Laid-Open No. 4-200229. An electromagnetic contactor 3 is interposed in an AC electric circuit 1 that supplies power to a load 2, and a zero-phase current transformer 4 is provided in the AC electric circuit 1. The secondary side output of the zero-phase current transformer 4 is sent to the positive side level discriminator 11, the negative side level discriminator 12, the positive side signal width discriminator 13, and the negative side signal width discriminator 14 to detect leakage. In this case, the thyristor 6, which is a switching element, is turned on by the output of the pulse count determination circuit 15 to excite the exciting coil 5, thereby opening the electromagnetic contactor 3 and disconnecting the AC electric circuit 1.

[0004]

In such a conventional example, both the positive side and negative side level discriminators (comparators) 11,
The output signal of 12 is charged by the capacitors 16 and 17, and when it is charged to a certain reference level or more, a leakage detection signal is output to the thyristor 6 via the pulse count determination circuit 15 to operate the ground fault detection device. It was

However, in the conventional example, the input current at the time of starting the inverter device is recognized as a leakage current when external noise such as lightning and line noise charges the capacitors 16 and 17 to a certain reference level or more. , There was a problem of malfunction. Further, since the accuracy of the ground fault and the leakage detection level depends on the output signals of both the positive-side and negative-side level discriminators (comparators) 11 and 12, if the output accuracy of the comparator is not high, the detection accuracy is also high. There was a problem that I could not get it.

That is, when a signal in the vicinity of the discrimination level is input, in the conventional example, the trigger pulse is irregularly input to the pulse count discrimination circuit 15 composed of a flip-flop, which may be detected as a leakage. The present invention is provided in view of the above-mentioned point, and an external noise such as lightning that is different from a normal ground fault or a ground fault, and an object thereof is to prevent malfunction and to improve the ground fault detection accuracy. A ground fault detection device is provided.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a ground fault detecting device for interrupting an AC electric circuit by a switching element when a ground fault occurs in the AC electric circuit. Each of the positive-side level discriminator and the negative-side level discriminator having a plurality of reference levels for generating an output signal when a predetermined magnitude is exceeded for each waveform, and the positive-side level discriminator and the negative-side level discriminator, respectively. Add the output signals of the positive side and negative side signal width discriminators and the positive side and negative side signal width discriminators that are counted by a clock pulse of a constant cycle for discriminating that the output signal is equal to or larger than a predetermined pulse width. With an adder,
The switching element is operated by the output of the adder.

According to a second aspect of the present invention, in a ground fault detection device that shuts off the AC line by a switching element when a ground fault occurs in the AC line, each of the positive and negative waveforms of the ground fault component. A positive side level discriminator and a negative side level discriminator having a plurality of reference levels, and output signals of the positive side level discriminator and the negative side level discriminator. A positive side and a negative side adder for determining that is above a predetermined leakage detection level,
A flip-flop circuit that outputs the addition result of the adder with a clock pulse of a constant cycle; and a counter circuit that recognizes that the output signals of the positive-side and negative-side adders are input multiple times, The switching element is operated by the output of the counter circuit.

[0009]

According to the present invention, by adding a level to an external noise such as lightning or line noise which is different from a normal ground fault or earth leakage by an adder, noise of high frequency component can be cut off, and malfunction occurs. It is possible to realize a ground fault detection device that is difficult to perform. Further, the leak detection level can be controlled with higher accuracy by changing the count value of the counter circuit which is counted by the clock pulse of a constant cycle or by reducing the pulse width of the clock pulse.

Further, according to the second aspect, as in the first aspect, the level is added by an adder to external noise such as lightning and line noise different from a normal ground fault or earth leakage, so that a high frequency component is obtained. It is possible to realize the ground fault detection device capable of cutting off the noise of the above and less likely to malfunction. Also,
The leakage detection level can be controlled with higher accuracy by changing the count value of the counter circuit that is counted by the clock pulse of a constant cycle or by reducing the pulse width of the clock pulse.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. According to the present invention, an output signal of each of the positive-side and negative-side level discriminators is discriminated by the adder to detect a leak, and the ground fault detection device is activated. That is, the ground fault component of the AC circuit is input to the positive-side level discriminator and the negative-side level discriminator, and when a certain reference value is exceeded, the output signal that generates a signal is counted by a clock pulse of a certain cycle. In the flip-flop circuit, the output signal of the positive side level discriminator and the output signal of the negative side level discriminator are respectively added by the adder, and when the preset value is exceeded, by generating the output signal from the adder, The positive signal width and the negative signal width are discriminated.

At this time, if an output signal is not generated from the adder, it is not considered as a leakage signal. A counter that recognizes that the signal from the count circuit has been output a plurality of times outputs a leakage detection signal to the thyristor to activate the ground fault detection device. Hereinafter, specific examples will be described. FIG. 1 shows an embodiment corresponding to claim 1, and shows a block diagram on the positive side or the negative side. The positive-side level discriminator and the negative-side level discriminator 20 are composed of five comparators 21 to 25, and have different reference values 1 to 5 respectively.
And the input signal are compared.

That is, an output signal corresponding to each voltage reference level (the above reference values 1 to 5) is generated when a predetermined magnitude is exceeded for each waveform on the positive side and the negative side which are components of the leakage signal. is there. The positive-side and negative-side signal width discriminator 30 is composed of five flip-flops 31 to 35, and the outputs of the respective comparators 21 to 25 are input to the D input terminal.

The positive-side and negative-side signal width discriminator 30 counts with a clock pulse having a constant period for discriminating that the output signal of each of the positive-side and negative-side level discriminators 20 has a predetermined pulse width or more. I am trying to do it. The output signals of the positive-side and negative-side signal width discriminators 30 are added by the adder 40. When the output of the adder 40 is output a certain number of times, the pulse counting circuit 50 turns on the thyristor. Then, a signal for cutting off the AC circuit is output.

Next, the operation of the circuit shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 2A, the peak voltage value of the leakage signal is the threshold value TH1 of the comparators 21 to 25.
When TH5 is exceeded, the positive side level discriminator and the negative side level discriminator 20 generate output signals. When the data of the output signal exceeds each reference level, it is added by the adder 40 as shown in FIG. 2B, and when added to a certain value, an output signal (carry signal) is generated ( Figure 2
(See (c)).

The pulse count circuit 50 counts that this output signal has been output a plurality of times, and, for example, when it counts three, an OUT signal is generated as shown in FIG. 2 (d). When this OUT signal is generated, the thyristor 6 is operated to excite the exciting coil 5 to open the electromagnetic contactor 3 and disconnect the AC electric path 1 as shown in FIG.

(Embodiment 2) FIG. 4 shows an embodiment 2 and is an embodiment corresponding to claim 2. In the present embodiment, the positive side level discriminator 61 and the negative side which generate an output signal according to each voltage reference level when a predetermined magnitude is exceeded for each waveform of the positive side and the negative side which are components of the leakage signal. Level discriminator 62
And the positive side level discriminator 61 and the negative side level discriminator 6
Adder 64, 66 for determining that each output signal of 2 is above a predetermined voltage level, flip-flop circuits 63, 65 for outputting the addition result of the adder 64, 66 with a clock pulse of a constant cycle, A counter 67 that recognizes that the output signals of the adders 64 and 66 have been output multiple times.
It is composed of a pulse count detection circuit.

FIG. 5 shows the timing chart of FIG.
When the input signal (leakage signal) shown in FIG. 5 (a) exceeds the positive reference voltage and the negative reference voltage, FIG. 5 (b) (c)
As shown in FIG. 5, when the signals from the flip-flop circuits 63 and 65 are counted by the adders 64 and 66 for 4 clocks, the OUT signal is generated (FIG. 5).
(See (d) to (g)).

[0019]

According to the present invention, when a ground fault occurs in an AC electric circuit, a ground fault detecting device for interrupting the AC electric circuit by a switching element is provided for each of the positive and negative waveforms of the ground fault component. A positive side level discriminator and a negative side level discriminator having a plurality of reference levels, and output signals of the positive side level discriminator and the negative side level discriminator. Is a predetermined pulse width or more, a positive side and negative side signal width discriminator counted by a clock pulse of a constant cycle, and an adder for adding the output signals of the positive side and negative side signal width discriminators Since the switching element is operated by the output of the adder, the level is added by the adder to external noise such as lightning and line noise different from normal ground fault or earth leakage. This In, it is possible to cut the noise of high frequency component, it is possible to realize a malfunction difficult ground fault sensing device. Further, by changing the count value of the counter circuit which is counted by the clock pulse of a constant cycle or by reducing the pulse width of the clock pulse, it is possible to control the leakage detection level with higher accuracy. is there.

Further, according to a second aspect of the present invention, in the ground fault detection device that shuts off the AC line by a switching element when a ground fault occurs in the AC line, each of the positive and negative waveforms of the ground fault component. A positive side level discriminator and a negative side level discriminator having a plurality of reference levels, and output signals of the positive side level discriminator and the negative side level discriminator. A positive side and a negative side adder for determining that is above a predetermined leakage detection level,
A flip-flop circuit that outputs the addition result of the adder with a clock pulse of a constant cycle; and a counter circuit that recognizes that the output signals of the positive-side and negative-side adders are input multiple times, Since the switching element is operated by the output of the counter circuit, the level is adjusted by an adder with respect to external noise such as lightning and line noise different from a normal ground fault or earth leakage, as in the case of claim 1. By adding, the noise of the high frequency component can be cut, and a ground fault detection device that is less likely to malfunction can be realized. Further, the leak detection level can be controlled with higher accuracy by changing the count value of the counter circuit which is counted by the clock pulse of a constant cycle or by reducing the pulse width of the clock pulse.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a timing chart of FIG. 1 above.

FIG. 3 is a schematic block diagram of the entire ground fault detection device of the above.

FIG. 4 is a block diagram of a second embodiment of the above.

FIG. 5 is a timing chart of FIG. 4 above.

FIG. 6 is a block diagram of a conventional ground fault detection device.

[Explanation of symbols]

 1 AC line 2 Load 4 Zero-phase current transformer 6 Thyristor 20 Positive side and negative side level discriminator 30 Positive side and negative side signal width discriminator 40 Adder 50 Pulse count circuit

Claims (2)

[Claims] 1. A ground fault detecting device for interrupting an AC line by a switching element when a ground fault occurs in the AC line, wherein a predetermined magnitude is set for each of the positive and negative waveforms of the ground fault component. A positive side level discriminator and a negative side level discriminator having a plurality of reference levels for generating an output signal when exceeding, and the respective output signals of the positive side level discriminator and the negative side level discriminator having a predetermined pulse width or more. And a positive side and negative side signal width discriminator that is counted by a clock pulse of a constant cycle for determining that the output signal of the positive side and negative side signal width discriminator is added. A ground fault detection device in which the switching element is operated according to the output of the container. 2. A ground fault detecting device for interrupting the AC line by a switching element when a ground fault occurs in the AC line, wherein a predetermined magnitude is set for each of the positive and negative waveforms of the ground fault component. A positive side level discriminator and a negative side level discriminator having a plurality of reference levels for generating an output signal when exceeding, and the respective output signals of the positive side level discriminator and the negative side level discriminator have predetermined leakage detection levels. The positive-side and negative-side adders that determine that the above is true, the flip-flop circuit that outputs the addition result of the adder with a clock pulse of a constant cycle, and the output signals of the positive-side and negative-side adders are A ground fault detection device comprising a counter circuit for recognizing that a plurality of inputs have been made, and operating the switching element by the output of the counter circuit.