JPH076532Y2 - Current detector - Google Patents

Description

[Detailed description of the device] [Industrial applications]

This invention relates to a current detector using an optical fiber.

[Prior art]

Conventionally, as a detector for detecting that a current has flowed more than a set value (overcurrent), induction disk type, induction ring type, induction cup type, moving coil, as used in overcurrent relays, etc. Shapes, movable iron core shapes, static shapes with transistors, etc. are known.

[Problems to be solved by the device]

However, since the conventional current detector outputs an electrical signal such as a contact signal as an overcurrent detection signal,
It has the drawbacks of being vulnerable to noise and requiring a special circuit to distinguish between the signals when a large number are provided. An object of the present invention is to provide a current detector which has a simple structure, is resistant to noise, and can easily identify which of the overcurrents is detected when a large number are provided.

[Means for Solving the Problems]

To achieve the above object, in a current detector according to the present invention, a fuse that is blown by an overcurrent, a spring that is hooked by the fuse, an optical fiber that is bent by the return of the spring when the fuse is blown, And a device for detecting an increase in loss due to bending of the optical fiber.

[Action]

When an overcurrent flows and the fuse blows, the spring hooked on this fuse returns. Then, the optical fiber is bent and the transmission loss of the optical signal increases. This increase in loss can be easily detected by propagating an optical signal in the optical fiber and monitoring the emitted light with an optical power meter. Also, if an optical power analyzer that detects the loss increase amount and position by the OTDR (Optical Time Domain Reflectometer) method is connected to one end of this optical fiber, the location where the loss increase due to the fuse blowout can be easily detected. . Therefore, by providing a large number of current detectors so that the fuses can be bent at a large number of places in the optical fiber, it is possible to determine which of the large number of current detectors has detected the overcurrent with a simple configuration.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. First, as shown in FIG. 1, the fuse base 2 is fixed to the substrate 1, and one end of each of the electric wires 61 and 62 is screwed onto the conductive plates 23 and 26 by screws 21 and 24. The fuse 3 is screwed onto the conductive plates 23 and 26 with screws 22 and 25, thereby forming a current path from the wire 61 to the wire 62 through the conductive plate 23, the fuse 3 and the conductive plate 26. On the other hand, the substrate 1 is provided with locking pieces 51, 52, 53,
One end of a spring (coil spring) 4 is locked to the locking piece 51. Hook 41 provided at the other end of this spring 4
However, the spring 4 is stretched to be hooked on the fuse 3, and the further extended hook 42 is hooked on the optical fiber 7. The optical fiber 7 is locked to the locking pieces 52 and 53, and the hook 42 is hooked on the optical fiber 7 between the locking pieces 52 and 53. An optical power analyzer 8 is connected to one end of the optical fiber 7. In this state, it is assumed that an electric current is flowing through the electric wires 61 and 62. When this current exceeds the set value and becomes excessive, the fuse 3 is blown. Since the fuse 3 disappears due to melting, the spring 4 tries to return to its original state by contracting, as shown in FIG. As a result, the optical fiber 7 is pulled and bent by the hook 42 between the locking pieces 52 and 53. Then, microbending loss occurs in the optical fiber 7, and the transmission loss of light locally increases. Therefore,
If a light source (not shown) is connected to one end of this optical fiber 7 and an optical power meter (not shown) is connected to the other end, an increase in transmission loss caused by the occurrence of overcurrent can be detected. In this embodiment, as shown in the figure, the optical power analyzer 8 is used to detect the increase of the transmission loss and the position of the increase by the OTDR method. If the loss increase position is also detected in this manner, a large number of current detectors configured in this way are provided at each position with respect to one optical fiber 7, and at which position the transmission loss increase will occur. It is possible to know where the overcurrent has occurred and easily detect where the overcurrent has occurred. Since the microbending loss in the optical fiber 7 can be detected if it occurs at about 0.5 dB, a normal optical fiber (outer diameter: 125 μm, core diameter: 10 μm, difference in refractive index between core and clad: 0.3% quartz In the case of a system glass single mode optical fiber), the space between the locking pieces 52 and 53 and the restoring force, stroke, etc. of the spring 4 may be set so that the radius of curvature can be bent to about 5 to 10 mm. Next, the above-mentioned optical fiber is used as the optical fiber 7, the interval between the locking pieces 52 and 53 is set to 42 mm, and the spring 4 is bent so that the optical fiber 7 is bent to a radius of curvature of about 8 mm when the fuse 3 is blown.
When the experiment was performed by setting the force, stroke, etc., the following transmission loss increase data was obtained. Number of times Loss increase (dB) 1 0.48 2 0.55 3 0.57 4 0.56 5 0.52 6 0.58 7 0.57 8 0.51 9 0.55 10 0.53 From this experimental result, it was found that the blowout of the fuse 3 can be detected with sufficient reliability. Although the spring 4 is contracted by the blow of the fuse 3 in the above description, it may be arranged to extend in the opposite direction, and the optical fiber 7 may be bent when it extends.

[Effect of device]

According to the current detector of the present invention, the loss of the optical fiber locally increases when an overcurrent occurs, so that the overcurrent can be detected by detecting the increase in loss, and the position thereof can be easily known. Moreover, since an electrical signal is not used as an overcurrent detection signal but an optical signal propagating in an optical fiber is used, it is possible to perform highly reliable detection that is resistant to noise and does not cause erroneous detection.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is a plan view of the same embodiment when a fuse is blown. 1 ... Board, 2 ... Fuse stand, 21, 22, 24, 25 ... Screw, 23, 26 ... Conductive plate, 3 ... Fuse, 4 ... Spring,
41, 42 …… Hook, 51, 52, 53 …… Locking piece, 61,62 ……
Electric wire, 7 ... Optical fiber, 8 ... Optical power analyzer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Osamu Kojima 1440 Rokuzaki, Sakura City, Chiba Fujikura Electric Wire Co., Ltd. Sakura Factory Co., Ltd. (72) Mitsuhiro Tanaka 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Electric Line Co. Inside the company (72) Inventor Yuji Sugimasa 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Electric Wire Co., Ltd. (56) Reference JP-A-56-93242 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A fuse which is blown by an overcurrent, a spring which is caught by the fuse, an optical fiber which is bent by the return of the spring when the fuse is blown, and an increase in loss due to the bending of the optical fiber. A current detector having a device for detecting.