JPH03169218A - Leakage detector - Google Patents

Abstract

PURPOSE:To enable normal leakage only due to a sine wave, to be detected by taking the output in the positive direction and the output in the negative direction, of a leakage detecting means, with same polarities, separately out of the output of a DC voltage multiplexing means, to generate leakage signal under the condition of the existence of both the output amounts, and by interrupting a main circuit interlocked with the function of a switching element. CONSTITUTION:Output from a leakage detecting means 1 is amplified by an amplifying means 5, and by a DC voltage multiplexing means 6, DC voltage is added and after that, both the directional output amounts in the positive direction and the negative direction, of the leakage detecting means 1 are detected separately from the output of the DC voltage multiplexing means 6, with same polarities, and the existence of the output amounts is discriminated. Then, under the condition of the existence of both the directional output amounts, by output from a leakage signal output means 12 for generating leakage signal, a switching element 14 is operated and a main circuit is interrupted. As a result, the device is not operated by signal only in one direction, such as lightning, and normal leakage only due to a sine wave can certainly be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an earth leakage detection device that detects earth leakage in various electrical circuits.

2. Description of the Related Art This type of conventional earth leakage detection device amplifies the output of a zero-phase current transformer for detecting earth leakage using one amplifier, compares and judges this output with a comparator, and obtains the output signal of this comparator. It is designed to operate a one-shot circuit, operate a mechanical part via an output circuit and a switching circuit, and interrupt the electrical circuit.

Problems to be Solved by the Invention Conventional earth leakage detection devices use either the positive or negative direction of the earth leakage signal to control their operation. Even if the signal is in one direction, if the signal becomes a signal in the operating direction of the earth leakage detection device, it is often determined that this is the earth leakage signal and operates.

Means for Solving the Problems The earth leakage detection means includes an earth leakage detection means for detecting earth leakage, an amplification means for amplifying the output of the earth leakage detection means, and a DC voltage superimposition means for adding a DC voltage to the output of the amplification means. first and second determination means for separately extracting the positive direction output J and the negative direction output of the detection means from the output of the DC voltage superimposition means with the same polarity;
4} An earth leakage signal output means that generates an earth leakage signal on the condition that there is a force, a switching element that is operated by the output from this earth leakage signal output means, and a cutoff operation that interrupts the main circuit in conjunction with the operation of this switching element. The means were established.

The output from the action earth leakage detection means is amplified by the amplification means and a DC voltage is added by the DC voltage superposition means, and then the positive and negative direction outputs of the earth leakage detection means are of the same polarity and are superimposed with a DC voltage. The presence or absence of the leakage signal is detected separately from the output of the means and the presence or absence thereof is determined, and the switching element is actuated by the output from the earth leakage signal output means which generates the earth leakage signal on the condition that there is an output in both directions, and the mechanism unit interlocked with this is operated. Since it is designed to operate, it is not activated by a signal such as lightning that is only in one direction, positive or negative, and can reliably detect only normal current leakage caused by a sine wave.

Example An embodiment of the present invention will be described based on the drawings.

First, a zero-phase current transformer 1 is provided as a leakage detection means that is installed in an electrical circuit to detect electrical leakage in the electrical circuit, and this zero-phase current transformer 1 includes a capacitor 2, a bidirectional diode 3, and a resistor An amplifier 5 serving as an amplification means is connected via the . A DC superimposition circuit 6 as a DC voltage superposition means is connected to the amplifier 5, and a first comparator 7 and a second comparator 8, which constitute determination means, are connected to the DC superposition circuit 6. .

Next, a first one-shot circuit 9 is connected to the first comparator 7, and a second one-shot circuit 9 is connected to the second comparator 8 through an inverter circuit 10.
・Circuit ■1 is connected.

These one-shot circuits 9 and 11 are connected to the input side of an AND circuit 12 serving as an earth leakage signal output means. This AND circuit 12 is connected to an output circuit 13, and the output side of this output circuit 13 is connected to the gate of an SCR 1.5 connected in series to a trip coil 14 serving as a cutoff operation means.

In such a configuration, the operation when a normal leakage occurs will be explained with reference to the waveforms of each part shown in FIG. First, if it is a normal earth leakage, it is a sine wave, so the output of the amplifier 5 is a sine wave.

Then, when there is no leakage signal to the output of the amplifier 5 by the DC superimposition circuit 6, a DC voltage is added so that the output voltage is in the positive direction. This voltage is compared by first and fifth second comparators 7 and 8, each having a determination voltage set, and outputs of the comparators 7 and 8 are obtained, respectively. Then, when the output of comparator 7 rises, the first one-shot I/circuit 9
Output J is generated, and the second one-shot circuit 11 generates an output at the falling edge of the comparator 8. Therefore, an operation signal is output from the AND circuit 12 at the same time as the output from the second one-shot circuit 11 is generated. As a result, the SCR 15 is turned on via the output circuit 13, the trip coil 14 is energized, a mechanical section (not shown) moves, and the contacts of the main circuit are opened.

Next, the operation when there is a half-wave electric leakage caused by lightning or the like will be explained based on FIG. 3. First, since lightning or the like is a unidirectional signal, either positive or negative, the output from the amplifier 5 is either positive or negative. Therefore,
An output is output from the first comparator 7 to start up the first one-shot circuit 9, but since the output of the second comparator 8 is at H level 6, there is no output from the inverter circuit 10, and the second one-shot circuit 9 is activated. The one-shot circuit 11 never starts up. Therefore, there is no output from A N I) circuit l3, and SCR l5 cannot be turned on. Therefore, the positive direction of lightning, etc. or ['J. A signal in only the - direction will not cause an electric leakage.

Effects of the Invention As described above, the present invention includes an earth leakage detection-F stage for detecting earth leakage, an amplification means for increasing the output of this earth leakage detection means,
DC voltage superimposition means for adding a DC voltage to the output of the amplification means; first and second determination means, an earth leakage signal output means that generates an earth leakage signal on the condition that there are outputs from both of these determination means, and a switching element that is operated by the output from the earth leakage signal output means; Since a cutoff operation means is provided to cut off the main circuit in conjunction with the operation of this switching element, the output from the earth leakage detection means is
After being amplified by the amplifying means and adding the DC voltage by the DC voltage superimposing means, the positive direction and negative direction outputs of the earth leakage detection means are separately detected from the output of the DC voltage superimposing means as having the same polarity. The switching element is operated by the output from the earth leakage signal output means which generates the earth leakage signal on the condition that there is an output in both directions. It has the effect that it is not operated by a signal in only one direction, positive or negative, and can reliably detect only normal earth leakage caused by a sine wave.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a circuit diagram, FIG. 2 is a waveform diagram of each part in a normal leakage state, and FIG.
The figure is a waveform diagram of each part in a signal state of only one direction, such as lightning. DESCRIPTION OF SYMBOLS 1... Earth leakage detection means, 5... Amplification means, 6... DC voltage superimposition means, 9, 11... Judgment means, 12...
Earth leakage signal output means, 14... Breaking operation means Applicant: Toshiba Lighting & Technology Corporation 9

Claims (1)

[Claims] A positive direction output of the earth leakage detection means, comprising: earth leakage detection means for detecting electric leakage; amplification means for amplifying the output of the earth leakage detection means; and DC voltage superimposition means for adding a DC voltage to the output of the amplification means. first and second determining means for separately extracting the negative direction output from the output of the DC voltage superimposing means with the same polarity, and generating an earth leakage signal on the condition that there are both outputs from these determining means. An earth leakage detection device comprising: an earth leakage signal output means that outputs an earth leakage signal; a switching element that operates according to the output from the earth leakage signal output means; and a cutoff operation means that cuts off a main circuit in conjunction with the operation of the switching element.