JP2703769B2 - Tokinobu ground fault detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a time-delayed ground fault detector, and more particularly to a time-delayed ground fault detector that prevents malfunction. [Prior Art] FIG. 4 is a diagram showing a configuration of a conventional time-delayed ground fault detecting device. In the figure, (1) is an electric circuit, (2) is a ground fault detector, for example, CT, (3) is a first level discriminator connected to the ground fault detector (2), and (7) is a first level discriminator. (8) a third level discriminator connected to the integral type timed circuit (7);
Is a thyristor connected to the third level discriminator (8),
(10) is an electromagnetic trip device connected to the anode of the thyristor (9), and (11) is a circuit breaker that cuts off the electric circuit (1) by the electromagnetic trip device (10). FIG. 5 is a frequency characteristic diagram of the conventional time-delayed ground fault detector of FIG. FIG. 6 is an operation waveform diagram of the conventional example of FIG. The conventional time-long ground fault detector is constructed as described above,
If no ground fault has occurred in the electric circuit (1), no current is detected by the ground fault detector (2), so that the first level discriminator (3), the integral type timed circuit (7) and the third The level discriminator (8) does not produce an output and the thyristor (9) is not triggered, so that the electromagnetic removal device (10) does not operate. If a ground fault occurs in the electric circuit (1), the ground fault detector (2) outputs a waveform as shown in FIG. 6 (A). This output waveform is supplied to a first level discriminator (3), and is compared with a first discrimination level indicated by a dotted line in FIG. 6 (A). As shown in B), the pulse waveform is a first level discriminator (3)
Output from Next, this pulse waveform is supplied to an integral type timed circuit (7), and a waveform obtained by integrating the pulse waveform of FIG. 6 (B) as shown in FIG. 6 (F) is converted to an integral type timed circuit (7). Is supplied to a third level discriminator (8), and is compared with a third discrimination level indicated by a dotted line in FIG. 6 (F). When the third discrimination level is exceeded, FIG. A pulse waveform as shown in I) is output from the third level discriminator (8), and this output pulse triggers the thyristor (9) to activate the electromagnetic trip device (10) to turn on the circuit breaker (10). 11) Operate. [Problems to be Solved by the Invention] In the above-described conventional time-delayed ground fault detecting device, the frequency characteristics are as shown in FIG. There is a problem that a malfunction occurs due to a high-frequency leakage current through a capacitance between the electric circuit and the ground due to a high-frequency component generated from the electric circuit. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a time-delay-type ground fault detecting device having a frequency characteristic as shown in FIG. . [Means for Solving the Problems] A time-delay type ground fault detecting device according to the present invention includes a ground fault detector for detecting a ground fault current generated in an electric circuit, and an output from the ground fault detector. A first level discriminator for discriminating at a discrimination level of 1, a constant current generator for generating a constant current to apply a constant current to the output from the first level discriminator, and charging and discharging by the constant current generator , A second level discriminator for discriminating the charging voltage of the capacitor at a predetermined second discrimination level, an integral timed circuit for integrating the output of the second level discriminator, and A mask circuit for masking the output of the timed circuit at a predetermined value or less, and an electromagnetic trip device for a circuit breaker that is energized by the output of the mask circuit. [Operation] In the present invention, since the capacitor is charged and discharged by the constant current generator, high frequency components are removed, and malfunction due to high frequency leakage current is prevented. Embodiment FIG. 1 is a diagram showing a configuration of a time-delayed ground fault detecting device according to an embodiment of the present invention. In the figure, (1) ~
(3), (7) to (11) are the same as the conventional one shown in FIG. (4) is a constant current generator connected to the first level discriminator (3), (5) is a capacitor, one end of which is connected to the output side of the constant current generator (4) and the other. The end is grounded. (6) is a mask circuit, the input side of which is connected to the output side of the integral timed circuit (7), and the output side of which is connected to the cathode of the thyristor (9). (12) is a second level discriminator whose input side is the output side of the constant current generator (4),
Its output side is connected to the output side of the integral timed circuit (7). FIG. 2 is a diagram showing frequency characteristics of the embodiment shown in FIG. FIG. 3 is a diagram showing operation waveforms of the embodiment shown in FIG. In the time-rolled ground fault detection device configured as described above, if no ground fault occurs in the electric circuit (1), the ground fault detector (2) does not detect the current, so the circuit breaker (11) Does not work. When a ground fault occurs in the electric circuit (1), a detection waveform as shown in FIG. 3A is obtained by the ground fault detector (2). This detected waveform is supplied to a first level discriminator (3), and is compared with the first discrimination level shown by a dotted line in FIG. 3 (A), and a pulse waveform shown in FIG. 3 (B) is obtained. can get. As the pulse waveform, an output waveform as shown in FIG. 3 (C) is obtained by the constant current generator (4). By charging / discharging the capacitor (5) with this output waveform, high-frequency components are removed, and the output waveform shown in FIG. 3 (D) is supplied to the second level discriminator (12), and FIG. 3), and the output waveform shown in FIG. 3 (E) is obtained. This output waveform is applied to the integral type timed circuit (7) to obtain an output waveform as shown in FIG. 3 (F). That is, the second level discriminator (12)
When the charging voltage of the capacitor (5) exceeds the discrimination level set by itself, a constant level output is output. Then the second
The level discriminator (12) discharges the applied charging voltage of the capacitor (5) with a time constant determined by a circuit constant or the like, and gradually reduces the output current. In the process of decreasing the output current, when the charging voltage of the capacitor (5) again exceeds the discrimination level due to the output of the constant current generator (4), the second level discriminator (12) outputs the constant level output. However, increase the output current again. By repeating the operation of the second level discriminator (12), a saw-tooth waveform shown in FIG. 3 (E) is formed. The mask circuit (6) masks an output waveform of the output waveform which is equal to or less than a set value indicated by a dotted line in FIG. 3 (F). Therefore, when the value is less than the set value, the thyristor (9) is not triggered, and the circuit breaker (11) does not operate. When the value exceeds the set value, the output waveform shown in FIG. 3 (G) is obtained from the mask circuit (6), and the thyristor (9) is triggered by this output waveform, and the electromagnetic trip device (10) is energized. Activate the circuit breaker (11). [Effects of the Invention] As described above, the present invention provides a ground fault detector for detecting a ground fault current generated in an electric circuit, and a first fault for determining an output from the ground fault detector at a predetermined first determination level. A level discriminator, a constant current generator for generating a constant current for adding a constant current to the output from the first level discriminator, a capacitor for charging and discharging by the constant current generator, and a charging voltage for the capacitor A second level discriminator for discriminating at a predetermined second discrimination level, an integral timed circuit for integrating the output of the second level discriminator, and an output of the integrated timed circuit equal to or less than a predetermined set value A high-frequency component can be removed by charging and discharging a capacitor with a constant current generator, and a high-frequency component such as an inverter. There is the effect that the protection cooperative operation as a time-delayed type can be performed without malfunction due to high-frequency leakage current when a load that generates a voltage containing many components is connected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a time-delayed ground fault detecting device according to one embodiment of the present invention, FIG. 2 is a frequency characteristic diagram of the above embodiment, and FIG. 3 is an operation of the above embodiment. FIG. 4 is a configuration diagram of a conventional time-delayed ground fault detecting device, FIG. 5 is a frequency characteristic diagram of the above-mentioned conventional example, and FIG. 6 is an operation waveform diagram of the above-mentioned conventional example. In the figure, (1) ... electric circuit, (2) ... ground fault detector,
(3)... First level discriminator, (4)... Constant current generator, (5)... Capacitor (6).
(7) ... Integral type timed circuit, (9) ... Mask circuit,
(10) Electromagnetic trip device (11) Circuit breaker (12)
... This is a second level discriminator. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

(57) [Claims] A ground fault detector for detecting a ground fault current generated in an electric circuit, a first level discriminator for discriminating an output from the ground fault detector at a predetermined first discrimination level, and a first level discriminator. A constant current generator for generating a constant current for adding a constant current to the output of the capacitor, a capacitor for charging and discharging by the constant current generator, and a charging voltage of the capacitor for a predetermined second.
A second level discriminator for discriminating at the discrimination level of the following, an integration type timed circuit for integrating an output of the second level discriminator,
A mask circuit for masking the output of the integral type timed circuit below a predetermined set value; and an electromagnetic trip device for a circuit breaker activated by the output of the mask circuit. A time-delayed ground fault detection device, wherein the electromagnetic trip device of the circuit breaker is activated only when the value is equal to or greater than the value. 2. 2. The time-delayed ground fault detector according to claim 1, wherein the ground fault detector is a CT.