JP2000002738A - Direct current leak detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of a detecting part, and to reduce electronic circuits required for leak detection. SOLUTION: This detector is a direct current leak detector provided with a core 10 magnetized in response to a difference between a direct current in the first detected conductor 13 and a direct current in the second detected conductor 14, and a coil 11 wound for the core 10. The detector is provided with a high frequency output circuit 20 for outputting a high frequency current, a current limiter circuit 21 for making the high frequency current flow in the coil 11 and for limiting the current in the coil 11 not to get a prescribed value or more, a rectifier circuit 22 for detecting a voltage induced in the coil 11, and a comparing circuit 23 for comparing the voltage detected by the circuit 22 with a prefixed reference voltage to output a leak signal when the detected voltage is the reference voltage or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC leakage detector for detecting a leakage of a DC power generator such as a solar cell power generation system and a leakage due to insulation deterioration of various DC devices.

[0002]

2. Description of the Related Art In recent years, devices using DC have been increasing in a wide range of fields. In maintenance management for operating these devices smoothly and safely, for example, DC devices used in DC earth leakage breakers and the like are used. The necessity of a leak detection device has been increasing.

[0003] Conventionally, there has been widely known an earth leakage detection device used for an AC earth leakage breaker using a zero-phase current transformer. However, it is impossible to detect a direct current leakage with a leakage detection device using a zero-phase current transformer. For this reason, a zero-phase current transformer cannot be used for the DC detection device. Therefore, as a direct current detection device, a Hall element system, a shunt resistance system, a mag amplifier system, and a flux gate system (JP-A-47-1644, JP-A-53-31176)
JP-A-59-46859, JP-A-6-74978
No.) etc. have been proposed.

In the Hall element system, a detected wire is wound in a toroidal shape directly on a core of a magnetic material in which a gap for partially disposing a Hall element is formed, and the core is based on a change in a DC current flowing through the detected wire. This is a method in which a change in magnetic flux in the inside is directly detected by a Hall element.

In the shunt resistance method, a shunt resistor is connected in series to a conductor to be detected, and a potential difference generated at both ends of the shunt resistor is detected.

The mag-amp method uses a magnetic material core formed by winding a detection coil in a toroidal shape, penetrates a detected wire inside the core, and uses a direct current flowing through the detected wire to make the magnetic material core. DC bias within the saturation magnetic flux density to generate an imbalance during the time when the alternating magnetic flux generated by applying an AC current to the coil wound on the core in advance reaches saturation in the positive and negative directions. The change is detected by the detection coil. This method employs a configuration in which an exciting coil is wound around the core and an alternating current of a predetermined value is applied in order to apply a magnetic flux change in the core in advance.

In the flux gate method, a detection coil is wound in a toroidal shape around a core of an annular magnetic material which can form a magnetic gap periodically in a part thereof, and a detection target wire is disposed inside the core in a toroidal manner. A magnetic flux is generated in the core by a direct current flowing through the detected conductor, and the magnetic flux generated by the direct current is temporally changed (ON-OFF) by opening and closing the magnetic gap. This is a method of detecting by the electromotive force generated in the above.

[0008]

However, the direct current detection devices of the above-mentioned types use Hall elements or have a complicated core structure, and also use a change in magnetic flux as a principle. Since many electronic circuits are provided, there is a problem that the electronic circuit becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a DC leakage detector having a simple structure and requiring a small number of electronic circuits.

[0010]

In order to achieve the above-mentioned object, the present invention is directed to a method for controlling a direct current flowing through a first detected conductor which is a positive power supply line and a second detected conductor which is a negative power supply line. A DC leakage detection device including a core magnetized according to a difference from a flowing DC current, and an excitation coil and a detection coil wound around the core, wherein a high-frequency output circuit that outputs a high-frequency current, A current limiting circuit that allows a current to flow through the exciting coil and limits the current flowing through the exciting coil to not exceed a predetermined value; a voltage detecting circuit that detects a voltage induced in the detecting coil; A detection circuit that compares a detection voltage detected by the voltage detection circuit with a predetermined reference voltage and outputs a leakage signal when the detection voltage becomes equal to or lower than the reference voltage. And butterflies.

The invention according to claim 2 is characterized in that the detection coil is also used as an excitation coil.

According to a third aspect of the present invention, the core is formed in a shape having a closed magnetic path, and a part of the core is made divisible, and the first and second detected conducting wires are penetrated inside the core. It is characterized by the following.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a DC leakage detecting device according to the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 10 denotes an annular core made of a magnetic material such as a cobalt-based amorphous alloy having excellent square characteristics. The core 10 has an outer diameter of 21 mm and an inner diameter of 14 m.
m and a thickness of 4.5 mm. A coil (excitation coil / detection coil) 11 is wound around the core 10. The coil 11 is formed by winding an enamel wire having a conductor diameter of 0.2 mm in a toroidal shape 200 times. The core 10 and the coil 11 constitute a detection unit.

A conductor to be detected (first conductor to be detected) 13 and a conductor to be detected (second conductor to be detected) 14 penetrate through the hole 12 of the core 10, and the conductor to be detected 13 is connected to the DC power source E. The anode is connected to form a positive power supply line. The detected conductor 14 is connected to the cathode of the DC power supply E to form a negative power supply line. Reference numeral 15 denotes a load, and direct currents in opposite directions flow through the detected conductors 13 and 14.

Reference numeral 20 denotes a high-frequency output circuit that outputs a rectangular wave voltage having a frequency of 20 KHz, and 21 denotes a current limiting circuit that limits the current flowing through the coil 11 by the high-frequency output circuit 20.
A rectifier circuit 2 converts an AC voltage induced in the coil 11 into a DC voltage. This rectifier circuit 22 functions as a voltage detection circuit that detects a voltage induced in the coil 11. Reference numeral 23 denotes a comparison circuit that compares the DC voltage output by the rectifier circuit 22 with a preset reference voltage and outputs an H-level leakage signal when the output voltage becomes equal to or lower than the reference voltage.

Next, the operation of the DC leakage detecting device will be described.

First, a rectangular wave voltage having a frequency of 20 KHz is applied to the coil 11 by the high frequency output circuit 20. Note that, for convenience of explanation, the description will be made assuming that only the detected conducting wire 13 is used.
In the case where the change in the magnetic flux in the core 10 is shown in FIG. 2, if no DC current flows through the conductive wire 13 to be detected, the change in the magnetic flux in the core 10 is in the state of φ1. At this time, since the impedance of the coil 11 is set to be large, the alternating current flowing through the coil 11 is sufficiently small, and the current limiting (IM = current limiting value) of the current limiting circuit 21 does not operate. Therefore, the output voltage of the high-frequency output circuit 20 is applied to the coil 11 as it is.

Next, when a direct current (operating current) is applied to the detected conductor 13, the change in magnetic flux in the core 10 shifts to the state of φ2. Here, the current limit value IM is set to a current value at which the core 10 is saturated.

When the core 10 becomes saturated, the coil 11
, The current flowing through the coil 11 increases. Since the current flowing through the coil 11 cannot exceed the current limit value IM by the current limiting circuit 21, the voltage applied to the coil 11 decreases as the impedance of the coil 11 decreases.

That is, due to an increase in the DC current flowing through the conductive wire 13 to be detected, the core 10 becomes saturated, the magnetic flux in the core 10 changes to φ3, and the voltage applied to the coil 11 decreases.

When the change in magnetic flux is φ1, φ2, φ3, the coil 11
Is V1, V2, and V3, if it is known that the applied voltage of the coil 11 has decreased from V1 to V3, a DC leakage can be detected. In this embodiment, the rectifier circuit 22 and the comparator circuit 23 determine that the voltage has decreased, and detect DC leakage.

When a leakage occurs, the current becomes unbalanced (I1 ≠ I
2) occurs, and the difference (| I1-I2 |) is the leakage current. In this embodiment, this difference is used as the operating current to detect DC leakage. When no leakage occurs, I1 = I2, and the detected conductors 13, 14
Since the directions of the currents I1 and I2 flowing through are opposite to each other, the magnetic fields generated by
It remains at 1 and no DC leakage is detected.

FIG. 3A shows the voltage Vc of the coil 11 and the output voltage VO of the comparison circuit 23 when a current of 10 A flows through the detected conductors 13 and 14, respectively. Rectifier circuit 22
Rectifies the voltage Vc of the coil 11 and converts it to DC, and the comparison circuit 23 compares the converted DC voltage with a reference voltage. The comparison circuit 23 outputs an L-level output voltage VO when the converted DC voltage is equal to or higher than the reference voltage.

When the current flowing through the detected conductor 13 is 9.8 A,
When the current flowing through the detected conductor 14 is 10 A, the coil 1
1 and the output voltage VS of the comparison circuit 23 are shown in FIG.
It is shown in (B). In this case, since the voltage Vc of the coil 11 is small, the DC voltage converted by the rectifier circuit 22 becomes lower than the reference voltage. Therefore, the comparison circuit 23 outputs the output voltage (leakage signal) VS at the H level.

In the above embodiment, the coil 11 serves both as an exciting coil and a detecting coil. However, it goes without saying that the coils 11 may be provided separately.

By the way, according to such a DC leakage detecting device, since the annular core 10 employs the simplest configuration in which the coil 11 is wound in a toroidal shape, the structure is very simple. It is. Therefore, it is possible to easily and freely manufacture a DC leakage detection device according to the purpose. In other words, depending on the combination of the type and size of the core 10 and the number of penetrations of the detected conductors 13 and 14, the measurement sensitivity,
Since the measurement accuracy and the like can be freely manipulated, sufficient advantages can be obtained not only in terms of size and shape but also in particular in terms of cost.

Further, since the electronic circuits necessary for detecting the electric leakage may be the high-frequency output circuit 20, the current limiting circuit 21, the rectifying circuit 22, and the comparing circuit 23, the configuration of the entire circuit is very simple. Yes, the number of parts is small, and it is an inexpensive DC leakage detection device.

In the above-described embodiment, the core 10 is formed integrally with the ring. However, the core 10 may be configured such that the portion 10P indicated by a broken line can be divided, that is, detachably detachable. With such a configuration, the detected conductors 13 and 14 can be easily penetrated into the core 10.

Further, in the above embodiment, the voltage of the coil 11 is detected. However, a dedicated detection coil different from the coil 11 is wound around the core 10 to detect the voltage induced in the detection coil. May be. The core 10 is annular, but is not limited to this, and may have any shape as long as it has a closed magnetic path.

[0031]

As described above, according to the present invention, it is possible to freely operate measurement sensitivity, measurement accuracy, and the like with a detection unit having a simple structure, to reduce the number of required electronic circuits, and to reduce the cost. A DC leakage detection device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a DC leakage detection device according to the present invention.

FIG. 2 is a graph showing a change in magnetic flux in a core.

FIG. 3A is an explanatory diagram showing a relationship between a voltage of a coil and an output signal of a comparison circuit when no leakage occurs. (B) is an explanatory diagram showing the relationship between the voltage of the coil and the output signal of the comparison circuit when a leakage occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Core 11 Coil 13 Wire to be detected 14 Wire to be detected 20 High frequency output circuit 21 Current limiting circuit 22 Rectifier circuit 23 Comparison circuit

Claims (3)

[Claims] 1. A core magnetized according to a difference between a DC current flowing through a first detected conductor serving as a positive power supply line and a DC current flowing through a second detected conductor serving as a minus power supply line; A DC leakage detection device including a turned excitation coil and a detection coil, wherein a high-frequency output circuit that outputs a high-frequency current, the high-frequency current flows through the excitation coil, and the current flowing through the excitation coil has a predetermined value. A current limiting circuit for limiting the voltage so as not to be larger than the above, a voltage detecting circuit for detecting a voltage induced in the detecting coil, and comparing the detected voltage detected by the voltage detecting circuit with a predetermined reference voltage. And a comparison circuit for outputting a leakage signal when the detection voltage falls below the reference voltage. 2. The DC leakage detector according to claim 1, wherein said detection coil is also used as an excitation coil. 3. The core according to claim 1, wherein said core is formed in a shape having a closed magnetic path, a part of said core is made dividable, and said first and second wires are penetrated inside said core. The DC leakage detection device according to claim 1.