JP2900448B2 - Earth leakage detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric leakage detection device for detecting electric leakage of various electric circuits.

2. Description of the Related Art As a first type of a conventional leakage detection device of this type, the output of a zero-phase current transformer for detecting leakage is amplified by a single amplifier, and the output is compared and determined by a comparator for detection. There is a configuration in which a one-shot circuit is operated upon receiving a signal, and a mechanical unit is turned off via an output circuit and a switching circuit.

In addition, as the second type, for example,
As described in Japanese Patent No. 44921, there is an apparatus in which the operation control is performed using both the positive direction and the negative direction of the leakage signal. That is, this prior art is
The positive and negative outputs of the zero-phase current transformer are applied to a time constant circuit, and a leakage detection signal is output when the integrated value of the time constant circuit reaches a predetermined level.

Problems to be Solved by the Invention In the conventional first type device, since the operation control is performed using either the positive direction or the negative direction of the leakage signal, for example, lightning and the like Even if such a signal in one direction becomes a signal in the operation direction of the leakage detection device, the signal is often determined to be a leakage signal and operated.

The device of the second type is intended to prevent an inoperative time from occurring when a leakage current occurs, and it is possible to obtain an output in both positive and negative cycles of the leakage current. In this way, the occurrence of the inoperative time is prevented. Therefore, even if the signal is a one-way signal such as lightning, a leakage signal is generated when the output of the time constant circuit reaches a predetermined level with one of the positive and negative detection outputs.

An object of the present invention is to provide a ground fault detecting device that does not operate by a signal in only one positive or negative direction such as lightning, and can reliably detect only normal ground faults due to a sine wave. is there.

Means for solving the problems: a leakage detection means for detecting a leakage; a positive determination means and a negative determination means for outputting a detection signal when a signal in the positive direction and the negative direction of the leakage detection means is a predetermined value or more; It is directly linked to the detection signal from the means, and operates by the leakage signal output means for outputting the leakage signal when the detection signals in the positive direction and the negative direction are continuously generated in order, and the output from the leakage signal output means. The switching device includes a switching unit and a shutoff operation unit that shuts off the mechanism unit in conjunction with the switching unit.

The output from the electric leakage detection means is output from the electric leakage signal output means for generating an electric leakage signal on the condition that both the positive direction and the negative direction are separately detected and the presence or absence of the detection is determined. Since the switching means is operated by the operation of the switching mechanism and the mechanism which operates in conjunction with the operation of the switching means, it does not operate by a signal in only one positive or negative direction such as lightning. It is possible to reliably detect only the leakage current, and in particular, to reliably detect the leakage current even when the leakage current has a short wavelength such as a harmonic.

Embodiment An embodiment of the present invention will be described with reference to the drawings. First,
A zero-phase current transformer 1 is provided in the electric circuit and serves as a leakage detecting means for detecting a leakage in the electric circuit.
The first and second amplifiers 2, 3 which are independent in the positive direction and the negative direction, respectively, are connected. And these amplifiers
2 and 3 generate outputs in the same direction.
The amplifiers 2 and 3 have a first comparator (positive determination unit) 4 and a second comparator (negative determination unit) as determination means for determining whether or not their outputs have exceeded a predetermined level. Means 5 are connected to each other.

Next, first and second one-shot circuits 6, 7 are connected to these determination means, and these one-shot circuits 6, 7 are connected to the input side of an AND circuit 8 as a leakage signal output means. ing. The AND circuit 8 is connected to an output circuit 9, and the output side of the output circuit 9 is connected to the gate of an SCR 11 as switching means connected in series to a trip coil 10 as breaking operation means.

In such a configuration, the operation when a normal earth leakage occurs will be described together with the waveforms of the respective parts shown in FIG. First, in the case of a normal leakage, since it is a sine wave, the amplifiers 2 and 3 generate half-wave sine-wave outputs in the positive and negative directions, respectively. And comparator 4,
A rectangular wave signal is output by 5 and an output signal is generated from the one-shot circuits 6 and 7 by this signal. As a result, the SCR 11 is turned on via the output circuit 9, and the trip coil 10 is energized to open a contact of a mechanism (not shown).

Next, the operation in the case where there is a signal of either positive or negative due to lightning or the like will be described with reference to FIG.
First, since lightning or the like is a signal of only one of positive and negative, an output is generated from the first amplifier 2, but no output is generated from the second amplifier 3. Therefore, the output from the first comparator 4 is output and the first one-shot circuit 6 is started. However, since there is no output from the second comparator 5, the second one-shot circuit 7 does not start. Therefore, there is no output from the AND circuit 8, and the SCR 11 is not turned on. Therefore, it does not operate as a leakage due to either a positive or negative signal such as lightning. Here, the lightning surge current has only one of the positive and negative components, but the current detected by the zero-phase current transformer is opposite to the rising and falling when the lightning surge current sharply falls. It has a current component in the direction. Since the detection current in the reverse direction is extremely small, it does not cause the comparators 4 and 5 to output.

Advantageous Effects of the Invention As described above, the present invention provides a ground fault detecting means for detecting a ground fault, a positive judging means and a negative judging means for outputting a detection signal when a signal in the positive direction and the negative direction of the ground fault detecting means is a predetermined value or more And an earth leakage signal output unit that directly interlocks with the detection signal from each determination unit and outputs an earth leakage signal when the detection signals in the positive direction and the negative direction are sequentially generated in sequence,
The output from the leak detection means is provided in both the positive direction and the negative direction because the switching means operates by the output from the leakage signal output means and the shutoff operation means for shutting off the mechanism in conjunction with the switching means. Are separately detected and the presence or absence thereof is determined, and a switching unit is operated by an output from a leakage signal output unit that generates a leakage signal on the condition that there is an output in both directions, and a mechanism unit interlocked with the operation of the switching unit Is operated, it does not operate with only one signal in the positive or negative direction such as lightning, it can reliably detect only normal leakage due to a sine wave, and in particular, This has the effect that it is possible to reliably detect even a short wavelength such as a wave.

[Brief description of the drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a circuit diagram, FIG. 2 is a waveform diagram of each part in a normal earth leakage state, and FIG. 3 is only one of positive and negative lightning or the like. It is a waveform diagram of each part in a signal state. 1 ... leakage detection means, 4,5 ... judgment means, 8 ... leakage signal output means, 10 ... operation cutoff means

Claims (1)

(57) [Claims] An electric leakage detecting means for detecting an electric leakage, a positive judging means and a negative judging means for outputting a detection signal when a signal in the positive direction and a negative direction of the electric leak detecting means is equal to or more than a predetermined value; Leakage signal output means for outputting a leakage signal when the detection signals in the positive direction and the negative direction are successively generated in order in direct cooperation with the detection signal of the above, and a switching means operated by an output from the leakage signal output means And an interruption operation means for intermittently operating the mechanism in conjunction with the switching means.