JPS6239393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormal current detection device.

A transformer or a search coil is used as a conventional abnormal current detection device. However, the former method is based on a link motion that utilizes a magnetization phenomenon caused by a passing current, and the detection sensitivity varies greatly depending on changes in the state of the coupling portion of the transformer.
Moreover, in order to obtain the required detection sensitivity, the latter must be installed near the passing current and have a very large number of coil turns. Therefore, it becomes quite large in size, and when built into an insulator or the like, it has to be larger than an insulator of the same insulation class in order to obtain the required insulation reliability. Another problem was that the detection sensitivity varied depending on the direction in which the search coil was attached.

By incorporating a magnetoresistive element into the insulator, the present invention can detect abnormal currents without having to create a mechanical loop configuration in which a conductor is wound around a current-carrying conductor, such as in a transformer, and the element itself can detect extremely small amounts of current. Utilizing the characteristic of good sensitivity, it is possible to increase the insulation distance between the current-carrying conductor and the element to improve insulation reliability, and to compare the insulator dimensions with conventional insulator-integrated transformers (ICT). An object of the present invention is to provide an abnormal current detection device that can be made smaller.

Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings. In the drawing, 1 is a support insulator having a hollow part 1a with an open lower end in the center, and a power line 2 is supported at the upper end thereof. ing.

Reference numeral 3 denotes a detection element inserted into the top of the hollow portion 1a of the support insulator 1, and the lower half of the support rod 5 made of an organic insulating material is inserted into the hollow portion 1a and fixed with an adhesive 4. is embedded and fixed, and four lead wires 6a, 6b,
6c and 6d pass through the support rod 5 and are led out to the outside.

Reference numeral 7 denotes a magnetoresistive element constituting the detecting element 3, which is represented as an equivalent circuit of resistors R ₁ and R ₂ as shown in FIG. A bridge circuit is constituted by R ₃ , R ₄ and the resistors R ₁ , R ₂ . A bias power supply 8 is connected to the lead wires 6a and 6b of the detection element 3, and is designed to constantly supply a DC voltage to the bridge circuit made up of the resistors _R1 to _R4 . 9 is an output terminal connected to the lead wires 6c and 6d of the detection element 3, and when the resistance values R ₁ and R ₄ are equal to R ₂ and R ₃ in the bridge circuit of the resistances R _{1 to} R 4, The output voltage between the same terminals 9 becomes zero, and the resistance value
If there is a difference between R ₁ , R ₄ and R ₂ , R ₃ , the same terminal 9
A voltage is now generated between them.

The magnetoresistive element 7 becomes a resistor when a magnetic field acts on it.
R ₁ and R ₂ increase at different rates, and therefore a difference occurs between the resistance values R ₁ and R ₄ and R ₂ and R ₃ , and the terminal 9
It has the property of generating a voltage between them.
That is, an abnormal current occurs in the power line 2, and the magnetic field generated by this abnormal current acts in parallel to the magnetoresistive element 7 as shown in FIG. 3, and the magnetic field strength H
When the magnetic field strength H increases, the output voltage V generated at the output terminal 9 increases as shown in FIG. 3 d to b, and when the magnetic field strength H decreases, the output voltage V decreases as shown in the same figure b to a. It has a hysteresis characteristic in that even when the magnetic field strength H becomes zero, a residual output voltage is generated at the output terminal 9 due to the residual magnetic field of the magnetoresistive element 7 itself, as shown at point a in the figure.

On the contrary, when a perpendicular magnetic field acts on the magnetoresistive element 7 and the magnetic field strength H increases, the output voltage V of the output terminal 9 increases as shown in FIGS. 3a to 3c, and the magnetic field strength H decreases. Then, the output voltage V decreases as shown in c to d of the same figure, and even when the magnetic field strength H becomes zero, the third
It has a characteristic that a residual output voltage in the opposite direction is generated as shown at point d in the figure.

Moreover, in the embodiment of the present invention, the magnetoresistive element 7
Since the relative positions of the power line 2 and the power line 2 are constant as shown in FIG. 1, only parallel magnetic fields act on the element 7. Therefore, the output voltage V of the output terminal 9 appears based on the characteristic curve a to b shown by the solid line in FIG.

Note that a detection display circuit (not shown) is connected to the output terminal 9, and the magnetic field strength H is as shown in FIG.
When the output voltage V becomes Ha, the output voltage Va is detected and displayed.

Next, the operation of the abnormal current detection device configured as described above will be explained.

Now, when an abnormal current flows through the power line 2 due to a short circuit or the like, a magnetic field is generated around it, and this magnetic field acts on the magnetoresistive element 7 as a parallel magnetic field. When the resistances R ₁ and R ₂ of the element 7 increase at different rates due to this parallel magnetic field, the resistance values R ₁ , R ₄ and R ₂ , R ₃ increase.
The difference in resistance value becomes larger than the difference in resistance value due to the residual magnetic field, and therefore, a voltage larger than the residual output voltage a is generated at the output terminal 9. Then, the magnetic field strength H is Ha
When the output voltage V reaches Va, a detection and display circuit (not shown) is activated to detect and display that an abnormal current has flowed through the power line 2. Note that when the abnormal current disappears and the magnetic field acting on the magnetoresistive element 7 disappears, the voltage between the output terminals 9 returns from Va to a in FIG. 3.

Now, in the embodiment of the present invention, a detection element 3 in which a magnetoresistive element 7 is integrated is built into the inner top part of the hollow part 1a of the support insulator 1, and the magnetic field generated in the power line 2 is converted into a voltage by the element 7. Since it is configured so that it can be detected by converting it into a power line, abnormal current can be detected without forming a mechanical loop with the power line 1, and since the element 7 is also very small, the insulator 1 can be miniaturized. Also, since the element 7 with good detection sensitivity is used, the insulation distance between the power line 2 and the element 7 can be increased, and the insulation reliability can be improved.

In addition, in the above embodiment, the magnetoresistive element 7 and the resistor
Although the detection element 3 is formed integrally with R ₃ and R ₄ and is housed in the insulator 1, only the magnetoresistive element 7 may be housed therein.

Further, in the embodiment described above, a bridge circuit was used as a means for detecting the output voltage V of the detection element 3, but other than this, for example, a potentiometer or the like may be used.

As described in detail above, the present invention provides a magnetoresistive element for detecting abnormal current, which has the characteristic of generating an output voltage due to the magnetic field generated around the conductor due to the abnormal current flowing through the current passing conductor. By incorporating it into the insulator, it is possible to detect abnormal current without mechanically configuring a loop for the current-carrying conductor.The element itself is very small and has good detection sensitivity, so the insulator dimensions can be compared to those of conventional insulator-integrated transformers (ICT). It is possible to make the insulation distance smaller than that of the current passing conductor and the element, and the insulation reliability can be improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the abnormal current detection device of the present invention, Fig. 2 is a voltage detection circuit diagram of a magnetoresistive element, and Fig. 3 is a magnetic field strength of the magnetoresistive element. FIG. 3 is a hysteresis characteristic curve diagram of output voltage. Support insulator 1, power line 2, lead wires 6a, 6b,
6c, magnetoresistive element 7, output terminal 9, resistor R ₁ ~
R ₄ , magnetic field strength H, output voltage V.

Claims (1)

[Scope of Claims] 1. The magnetoresistive element for abnormal current detection, which has a characteristic of generating an output voltage by a magnetic field generated around the conductor due to an abnormal current flowing through the current passing conductor, is built into an insulator. An abnormal current detection device characterized by: 2. The abnormal current detection device according to claim 1, wherein the magnetoresistive element has a hysteresis characteristic that generates a residual voltage due to a residual magnetic field even when the magnetic field strength due to the abnormal current becomes zero. 3. The abnormal current detection device according to claim 1, wherein the means for detecting the output voltage of the magnetoresistive element is a bridge circuit. 4. The magnetoresistive element constitutes a bridge circuit by the element and another resistor, and the circuit is integrated as a detection element, and the detection element is built in the insulator. Abnormal current detection device as described in .