JP2575540Y2 - Leakage detection device in single-phase two-wire circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leakage detecting device for a single-phase two-wire circuit.

[0002]

2. Description of the Related Art Conventionally, an earth leakage detecting device for a single-phase two-wire circuit has a ground fault current flowing when insulation between a circuit and ground is abnormally reduced as shown in FIGS. The combined current with the leakage current that always flows through the ground capacitance between the grounds is detected by the zero-phase current transformer ZCT, and a leakage detection signal is output when the current value exceeds a set value.

[0003]

SUMMARY OF THE INVENTION The above-mentioned conventional single-phase two-wire leakage detection device has a small capacitance to ground and a low leakage current at all times in a short circuit over a wiring.
By setting the sensitivity current set value of the leakage detection device to be small, leakage detection can be performed with high accuracy. On the other hand, in an electric circuit having a long wiring length, the capacitance to ground is large, and the leakage current is always large.
There is a problem that the sensitivity current set value of the leakage detection device must be increased, and the leakage detection accuracy is significantly reduced.

[0004]

In view of the problems of leakage detecting device in the conventional single-phase two-wire path SUMMARY OF THE INVENTION An object of the present invention is also always leakage current in a large path, and cause a fire or electric shock The present invention provides a ground fault current detecting device capable of detecting a ground fault current with high accuracy. The configuration thereof is a single-phase two-wire circuit in which one line is grounded, and a zero-phase current transformer in which the line or the ground line is the primary side. The zero-phase current signal of the single-phase two-wire circuit from the device is converted into an electrical angle of a two-line voltage waveform of 90 degrees and 270 degrees .
Sampled at composed timing, and detects only the ground-fault current.

[0005]

According to the leakage detecting device for a single-phase two-wire circuit having the above structure, the zero-phase current is composed of a ground fault current as a resistive leakage current component and a constant leakage current as a capacitive leakage current component. , Each current component waveform has a phase difference. The present invention focuses on this point, and the electrical angle of the two-line voltage waveform is 90.
And 270 degrees , that is, the zero-sequence current waveform detected by the zero-sequence current transformer is sampled at the timing when the capacitive leakage current waveform becomes zero. Electric leakage can be detected accurately regardless of the magnitude of the current value.

[0006]

1 is an external connection diagram of a leakage detecting device in a single-phase two-wire circuit according to the present invention, and FIG. 2 is a single-phase two-wire circuit according to the present invention.
It is a block diagram of a leak detection device in a wire type electric circuit. FIG. 3 is a waveform diagram in a steady state, and shows a 1: L relative ground voltage waveform and 2: L relative ground capacitance leakage current waveform. FIG. 4 is a waveform diagram at the time of occurrence of a ground fault.
4: Ground fault current waveform, 5: Zero-phase current waveform. Hereinafter, the present invention will be described with reference to these drawings.

Now, when a ground fault occurs in an electric circuit, the following a to
In step h, a leakage detection signal is output. a: Zero-phase current is detected by the zero-phase current transformer ZCT. b: The signal is amplified by the amplifier. c: Full-wave rectification is performed by the full-wave rectification unit. d: The full-wave rectified signal is sampled by the sampling unit at timings of 90 degrees and 270 degrees. This sampling signal is generated by inputting a voltage between two lines of a single-phase two-wire circuit as a reference signal to a sampling pulse generator via a transformer. It should be noted that the sampling value is almost 0 V in a steady state, and becomes an instantaneous value of the peak of the ground fault current waveform when a ground fault occurs. e: The sampled signal is held by the hold unit from the end of sampling to the time of input of the reset signal. The output is a square wave having a peak value as the sampling value as shown in FIG. The reset signal is generated by a reset pulse generating unit that outputs a pulse after a time t with the sampling pulse as a trigger signal, and is input to a hold unit reset terminal. f: The voltage comparator detects whether or not the signal of e is equal to or higher than the threshold voltage. If the signal is equal to or higher than the threshold voltage, a square wave pulse having the same time width and a constant voltage value is output. g: When square wave pulses are continuously input to the integration section, the voltage rises to a certain voltage after a certain time. h: The voltage comparator detects the output voltage of g, that is, the fact that the resistance ground fault of the set value or more has continued for the set time or more, and outputs the leakage detection signal.

FIGS. 5 to 12 show waveforms at the time of steady state in which only continuous leakage is performed in each of the above steps a to h and waveforms at the time of occurrence of ground fault in which ground leakage is added to the continuous leakage.

[0009]

According to the present invention, there is provided a single-phase two-wire circuit having a single-phase two-wire circuit in which a single-phase two-wire circuit is grounded. The zero-phase current signal of the single-phase two-wire circuit from
Sampled at the timing when an electrical angle of 90 degrees and 270 degrees, can be detected only ground-fault current, there is an effect that can be detected accurately leakage at a significantly reduced state generation of unnecessary operation due to always leakage current .

[Brief description of the drawings]

FIG. 1 is an external connection diagram of a leakage detection device in a single-phase two-wire circuit according to the present invention.

FIG. 2 is a block diagram of the leakage detecting device in the single-phase two-wire circuit according to the present invention;

FIG. 3 is a waveform diagram in a steady state.

FIG. 4 is a waveform diagram when a leakage current is detected.

FIG. 5 is a waveform chart of step a in FIG. 2;

FIG. 6 is a waveform chart of step b in FIG. 2;

FIG. 7 is a waveform chart of step c in FIG. 2;

FIG. 8 is a waveform chart of step d in FIG. 2;

FIG. 9 is a waveform chart of step e in FIG. 2;

FIG. 10 is a waveform chart of step f in FIG. 2;

FIG. 11 is a waveform chart of step g in FIG. 2;

FIG. 12 is a waveform chart of step h in FIG. 2;

FIG. 13 is an external connection diagram of a leakage detection device in a conventional single-phase two-wire circuit.

FIG. 14 is a block diagram of a conventional leakage detecting device in a single-phase two-wire circuit.

[Explanation of symbols]

 ZCT: Zero-phase current transformer.

Claims (1)

(57) [Scope of request for utility model registration] 1. In a single-phase two-wire circuit in which one wire is grounded, a zero-phase current signal of the single-phase two-wire circuit from a zero-phase current transformer whose primary side is a circuit or a ground wire is: Of the voltage waveform between two lines
An earth leakage detection device for a single-phase two-wire circuit, wherein sampling is performed at timings at which the electric angle becomes 90 degrees and 270 degrees, and only a ground fault current is detected.