JPH03176674A - Checker of electric leak - Google Patents

Abstract

PURPOSE:To make a device easy for handling, small in size, light in weight, and to attain a detection of electric leak from the outside of cable without contact by issuing an alarm when the output signal value of a detecting element exceeds a specified value. CONSTITUTION:When a ground fault is generated in a point P for example, a leak current Ig flows from that part and a return current I2 becomes I1-Ig accordingly, thereby a magnetic flux appeared outside becomes phi1-phi2not equal to 0. So, an output voltage 11a is generated in the detecting element 11. Since the output voltage 11a is extremely minute, the signal is amplified by a AC amplifying circuit 12. The amplified signal 12a becomes a detecting signal 13a passing through a detecting circuit 13, and after that, a comparison is made with a reference value by a comparator circuit 14 whether the detecting signal 13a is larger than the specified value or not. When the detecting signal is larger than the specified value, an output 14a is generated and made to pass through an output circuit 15, then the alarm buzzer 16 is sounded by the output signal 15a. By this arrangement, the electric leak is detected from the outside of cable without contact.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a new type of earth leakage checker that issues an alarm when it detects a leakage current in an indoor electrical wiring path.
In particular, the present invention relates to an earth leakage checker that allows leakage current to be detected from outside the line without contact, and is suitable for preventing fires caused by leakage current.

<Prior Art> Conventionally, there is an earth leakage fire alarm that detects leakage current in an indoor electrical wiring path and issues an alarm. This @ miscellaneous equipment is installed in electrical circuits with a voltage of 600V or less to prevent fires caused by leakage to metal laths, etc., and consists of a current transformer, a receiver, a sound device, etc.

The sensor used in this alarm automatically detects leakage current in the warning cable and sends it to the receiver.
A current transformer is used.

Current transformers are classified into through-type and split-type depending on their structure, but the principle is the same.

FIG. 3 is a schematic diagram of a conventional earth leakage fire alarm. 3
0 is a current transformer, inside of which a detection secondary winding 32 is wound around a magnetic core 31 such as a ferrite core or permalloy core.

33 is a receiver, and 34 is an audio device. Reference numerals la and 1b are electrical circuits that are installed to penetrate the magnetic core 31 within the current transformer 30.

Next, the operation will be explained. Assuming that the currents flowing in the electric circuits 1a and 1b are I8 and I2, respectively, when there is no leakage, I, = I, and the magnetic fluxes passing through the magnetic core 31 cancel each other out, and the current flows between both terminals m and n of the secondary winding 32. no voltage is generated. However, when an earth leakage occurs, a ground fault current (not shown) flows to the ground fault point, causing a difference between the currents 1 and I2 flowing in the electrical circuits 1a and 1b, which causes a difference in the generated magnetic flux, and the magnetic core 31 Magnetic flux Φ flows through. Therefore, an induced voltage E is generated between both terminals m and n of the secondary winding 32 of the current transformer 30.

The effective value E of this induced voltage is expressed by the following equation.

E = 4.44 f NΦ (V) where f (Hz) is the frequency, N is the number of turns of the secondary winding,
Φ (sister) is magnetic flux.

This induced voltage E is input to the receiver 33, and when it exceeds a predetermined value, an alarm is issued by the acoustic device 34.

<Problems to be solved by the invention> As mentioned above, the conventional earth leakage fire alarm uses a current transformer as a sensor, so it is necessary to insert the electric wire into the hole in the center of the current transformer. Ta.

Therefore, when installing a current transformer on existing wiring, a split type is used, which allows the current transformer to be divided into two while leaving the wires as is, but this type has a more complex structure than a through type (type that cannot be divided). It became larger.

In addition, the current transformer has a magnetic core inside and is heavy and difficult to handle.

Furthermore, even if a leakage was detected, the location of the leakage could not be determined, and it took time to check the wiring path.

Furthermore, this type of earth leakage fire alarm has a complex structure and is expensive, so it has not been used as a simple checker for earth leakage.

The present invention has been made to solve the above-mentioned problems, and provides an easy-to-handle, small and lightweight earth leakage checker that detects electric leakage from the outside of electric wires in a non-contact manner.

Means for solving the above problems〉 The earth leakage checker for solving the above problems has a magnetic sensing element inside which generates an output in proportion to the strength of the magnetic field,
A circuit that amplifies the output signal of the detection element and a circuit that generates an output when the output signal of the detection element exceeds a predetermined value are provided, and when the value of the output signal of the detection element exceeds the predetermined value, an alarm buzzer is activated. It makes a sound or activates an indicator light, etc.

<Function> The earth leakage checker according to the present invention is composed of a small detection element and a circuit, and automatically issues an alarm when there is an earth leakage in the wiring path, thereby preventing electrical fires caused by electric leakage. It can be prevented.

<Example> An example of the present invention will be described below with reference to the drawings. The second engineering drawing is a conceptual diagram showing the operating principle of the earth leakage checker.
1 is the power receiving transformer, 2 is the load of indoor electrical appliances, etc., 10
is an earth leakage checker. This earth leakage checker 10 includes a detection element 11, an AC amplifier circuit 12, a detection circuit 13,
It is composed of a comparison circuit 14, an output circuit 15, and an alarm buzzer 16. 1a and 1b are the outgoing and return paths of the current connected to the indoor wiring of the low-voltage side line of the power receiving transformer 1, respectively, IG is the grounding wire of the power receiving transformer, P is the indoor leakage point, and G is the ground. Also, I8 is the outbound route 1a
This forward current 1. Due to magnetic flux Φ,
occurs. I2 is a return current flowing in the return path 1b, and this return current I generates a magnetic flux Φ2. Tg is the leakage point P
This is a leakage current that flows more to the ground G.

Next, this operation will be explained. If there is no leakage indoors, the outgoing current is 1. and return current I2 are equal in magnitude, so each current 1. The magnetic fluxes Φ and φ2 generated by I2 and I2 are also equal in magnitude. Therefore, the outward journey 1a
The magnetic flux appearing outside the return path 1b becomes Φ, -Φ, = 0, and no voltage signal other than noise components is generated from the detection element 11 of the earth leakage checker 10. (when placed in close proximity to each other, such as when housed within a However, if a ground fault occurs at point P, leakage current Ig flows from that part, so return current I
, becomes I, -1g, so that the magnetic flux appearing outside becomes φ1-φ2≠O. Therefore, an output voltage 11a is generated in the sensing element 11.

Since the output voltage 11a is extremely weak, the AC amplifier circuit 12 amplifies the signal. The amplified signal 12a passes through a detection circuit 13 to become a detection signal 13a, and then a comparison circuit 14 compares the detection signal 13a with a reference value to see if it is greater than a predetermined value. If the value is above a predetermined value, an output 14a is generated, which passes through an output circuit 15, and the output signal 15a causes, for example, an alarm buzzer 16 to sound.

FIG. 2 is an example of a structural diagram of the sensing element 11 shown in FIG. Here, a semiconductor Hall element will be explained as an example of the sensing element. The Hall element is a typical magnetic sensing element, and a control g1 current Ic is passed from a to b of the control line 21 in the length direction of the semiconductor board 20, and a magnetic field B of 23 is applied at right angles thereto. This utilizes the so-called Hall effect in which an electromotive force (Hall voltage) is generated between both ends c and d of the output line 22 in the direction perpendicular to Ic and B. In this case, the electromotive force V generated is V=-Ic-B
It is expressed as (Here k is a sensitivity constant). When the magnetic field B and the control current Ic have an angle θ with respect to the right angle, the electromotive force generated is .cos θ. As this semiconductor board 20, GaAs (gallium arsenide) or InSb (indium antimony) is generally used. This sensing element 11 can be placed in a non-contact state near the outgoing current path 1a and the incoming current path 1b, as shown in FIG. 1, and is extremely easy to handle without making any changes to the existing line. When a leakage occurs, the outgoing current 11 and the returning current ■2 in Fig. 1 become I.
,-I! 40, the magnetic flux appearing outside the line becomes Φ, -Φ2≠O as described above, and the sensing element 11
This means that electrical leakage can be detected.

In the above example, a Hall element was used as the sensing element 11, but it is not limited to this, and any element that responds to a magnetic field may be used. For example, a magnetoresistive element whose resistance value changes depending on the magnetic field may be used. Good too.

<Effects of the Invention> As described above, according to the present invention, a small magnetic sensing element, an amplifier circuit, a comparison circuit, a buzzer, etc.
Since it is a lightweight earth leakage checker, it can be used in an inexpensive and simple manner, and the location of earth leakage can be detected by one person. Furthermore, since an alarm is emitted when there is a current leakage, it has the effect of preventing electrical fires caused by a current leakage.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the operating principle of an earth leakage checker according to an embodiment of the present invention, and FIG. 2 is an example of a structural diagram of a detection element.
FIG. 3 is a schematic diagram of a conventional earth leakage fire alarm. l...Power receiving transformer, 2...Load, 10...
Earth leakage checker 11...detection element, 12...AC amplifier circuit, ■3...detection circuit, 14...comparison circuit,
15...Output circuit, 16...Alarm buzzer-20...
・Semiconductor board, 30... Current transformer, 33... Receiver,
34...Sound equipment, Figure 1, Figure 2, Figure 3

Claims (1)

[Claims] a magnetic field generated by an electric current, a sensing element that responds to the magnetic field,
It includes a circuit that amplifies the output signal of the detection element, and a circuit that generates an output when the output signal of the detection element exceeds a predetermined value. An earth leakage checker characterized by operating an indicator light, etc.