JPS62257071A - Earth current detection sensor - Google Patents

Abstract

PURPOSE:To dispense with a drive power source and to remove the effect of electromagnetic induction, by detecting the movement of a magnetic body part by an earth current as light transmission loss due to the change in the width of the gap between the end surfaces of optical fibers. CONSTITUTION:When an earth current flows to an earth cable 20, a magnetic field is generated and a magnetic body part 13 moves so as to be attracted to the earth cable 20. When the magnetic body part 13 moves as mentioned above, the end surface 2a of one optical fiber 2 moves simultaneously. Because the other optical fiber 1 is fixed by a fixing jig 15, said optical fiber 1 does not move and the width of the gap between the end surfaces 1a, 2a of the optical fibers 1, 2 becomes large. If the width of the gap between the end surfaces of the optical fibers becomes large, an earth current can be detected by the increase in the transmission loss of light transmitted from one optical fiber to the other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ground fault current detection sensor for detecting a location where a ground fault current flows.

[The problem that the prior art and the invention are trying to solve] In high-voltage power transmission lines, when the ground and the line are short-circuited for some reason, abnormal cross-contact currents called ground fault currents can occur. It is necessary to detect the locations where ground fault currents have flowed and take appropriate action.For this reason, ground fault current detection sensors are grounded at each location on the power transmission line.

However, many conventional sensors are electrical sensors that convert fluctuations into signals electrically and transmit them through metal lead wires for detection, and require a power source to drive each sensor. Additionally, since it is installed near a high-voltage power transmission line, it is affected by electromagnetic induction, making it difficult to perform stable and accurate detection.

Furthermore, it is necessary to connect each sensor and the detection section, which are installed in large numbers at various locations on the power transmission line, with metal lead wires, resulting in a problem that the number of metal lead wires becomes extremely large.

Therefore, an object of the present invention is to provide a ground fault current detection sensor that does not require a driving power source and is not affected by electromagnetic induction.

[Means for Solving the Problems] The ground fault current detection sensor of the present invention includes a pair of optical fibers arranged such that their end faces face each other with a gap therebetween, and further includes one of the pair of optical fibers. Attached to the side is a magnetic body that moves due to the magnetic field generated when ground fault current flows.

[Function] In the ground fault current detection sensor of the present invention, a magnetic part is attached to one side of a pair of optical fibers, and the sensor is arranged so that the magnetic part is located near the grounding table through which the ground fault current flows. will be installed. If a ground fault current flows through the ground cable,
A magnetic field is generated, and the magnetic material in the vicinity moves so as to be attracted by this magnetic field. When the magnetic body portion moves, one of the optical fibers to which the magnetic body portion is removed moves, and the width of the gap between the end faces of the pair of optical fibers changes.

As shown in Figure 2, there is a proportional relationship between the width of the gap between the end faces of optical fibers and the optical transmission loss caused by passing through the gap, so the optical transmission loss changes as the gap width changes. do. Therefore, when a ground fault current flows, the optical transmission loss of light transmitted from one side of the optical fiber to the other changes, so by detecting this change in optical transmission loss, the location where the ground fault current has flowed can be detected. can do.

Embodiment FIG. 1 is a sectional view showing an embodiment of the present invention. In FIG. 1, a pair of optical fibers 1.2 have their end faces 1.
a and 2a are arranged to face each other with a gap in between,
The optical fibers 1 and 2 are each attached to an optical fiber fixing member 3.
It is fixed at 4.

Each of the optical fiber fixing members 3.4 has a flange portion 3.
a, 4a are formed, and the outer vibrator 7 is positioned so as to be sandwiched between the flanges 3a, 4a. The outer vibrator 7 is provided with a bellows approximately at the center. Grooves are formed in the portions of the flange portions 3a, 4a that the outer vibrator 7 contacts, and an O-ring packing 5 is inserted into the grooves.
．． 6 are fitted together. The O-ring packing 5.6 maintains the airtight condition inside the outer vibrator 7. A limiter vibe 8 is provided inside the outer vibe 7 via a coil spring 9. Optical fiber fixing members 3. are installed inside the limiter vibe 8 from both sides.
4 ends are fitted. The limiter vibe 8 is provided so that the end surfaces 1a and 2a of the optical fibers do not collide with each other when they approach each other. Further, both ends of the coil spring 9 are fixed to the flange portions 3a, 4a, respectively, and always act in the direction of contraction so as to minimize the gap between the end faces 1a, 2a of the optical fiber.

Screw threads are formed near both ends of the outer vibrator 7, and nuts 1 are screwed onto the threads.
0.11 are fitted and fixed. The nut 11 is integrated with the tip fiber 2 via the optical fiber fixing member 4, and a magnetic body portion 13 is attached to the nut 11 via the connecting portion 12. The ground fault current detection sensor of this embodiment is installed such that the magnetic body portion 13 is located near the ground cable 20.

The other optical fiber fixing member 3 is fixed by a fixture 15. Further, an external stopper 14 is provided on the outside of the nuts 10 and 11 so as to sandwich them, and the external stopper 14 prevents the nut 11 from moving excessively to the left in the drawing and damaging the bellows of the outer vibrator 7. is being defended.

When a ground fault current flows through the grounding cable 20, a magnetic field is generated, and the magnetic body part 13 moves so as to be attracted to the grounding cable 20. When the magnetic body part 13 moves in this way, the end face 1a of one optical fiber 1 also moves at the same time.

The other optical fiber 2 does not move because it is fixed by the fixture 15, so the end faces 1a and 2 of the optical fiber
The width of the gap between a becomes larger. As the width of the gap between the end faces of the optical fiber increases, as shown in FIG. 2, the optical transmission loss ΔP increases, so the transmission loss of light transmitted from one side of the optical fiber to the other increases.

Therefore, a ground fault current is detected due to this increase in optical transmission loss.

When the ground fault current stops flowing in the grounding cable 20, the magnetic field weakens and the optical fiber fixing member 4 returns to its original position on the right side of the drawing by the action of the coil spring 9. At this time, since the limiter vibe 8 is provided, the end surfaces 1a and 2a of the optical fibers do not come into contact with each other.

As explained above, the ground fault current detection sensor of the second embodiment detects the ground fault current by transmitting light from one optical fiber to the other optical fiber and measuring the power of the transmitted light. be able to. Therefore, unlike conventional electrical detection sensors, it does not require a power source.

Furthermore, the ground fault current detection sensors of this embodiment can be connected in series as shown in FIG. That is, by connecting each sensor with one optical fiber, light can be sequentially transmitted to each sensor. The light transmitted through each sensor in this way can be shared, for example, by a light backscatter meter.

FIG. 4 is a diagram showing an example of a waveform observed by this optical backscattering measuring device. The light backscattering measuring device can thus calculate the received light level corresponding to the distance of each point on the optical fiber. As shown in Fig. 4, the transmitted light is transmitted while decreasing its reception level at a constant slope, and the reception level of each sensor A, B, C, etc. is further rapidly decreased. There is. This corresponds to the optical transmission loss due to the gap between the end faces of the optical fibers in each sensor. Therefore, a ground fault current flows at a point where a sensor with a large optical transmission loss is located.

For example, in the case of Figure 4, the optical transmission loss ΔP2 at the point of sensor B is larger than the optical transmission loss of other sensors, and it is difficult to know that a ground fault current has flowed at the point of sensor B. can.

1-1 The ground fault current detection sensor of the present invention has been described using examples, but the invention is not limited to these examples. For example, the coil spring for returning the gap between the end faces of the optical fiber to its original width may not be provided as in the embodiment, and may be restored by other means. In addition, although an example has been shown in which each sensor is connected in series, each sensor does not necessarily need to be connected in series. They may also be connected by fiber.

Further, the end face of the tip fiber may be subjected to an end face treatment that is conventionally performed in optical connectors.

The end fiber used in this invention is not particularly limited, and conventionally used end fibers such as plastic fibers and silica fibers can be used.

[Effects of the Invention] As explained above, since the ground fault current detection sensor of the present invention transmits and detects an optical signal, it is not affected by electromagnetic induction unlike the conventional sensor. Therefore, the ground fault current can be detected more stably and accurately than before.

Furthermore, since detection is performed using light transmitted through an optical fiber, there is no need for a power source to drive a conventional sensor, and it can be easily installed.

Furthermore, as shown in the examples, the ground fault current detection sensor of the present invention can be connected in series, so it does not require a large number of lead wires unlike conventional sensors. , can be installed easily and economically.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the width of the gap between the end faces of optical fibers and optical transmission loss. FIG. 3 is a schematic configuration diagram showing an example of the connection state of the ground fault current detection sensor of the present invention. FIG. 4 is a diagram showing an example of a waveform observed by the optical backscattering ρ1 constant. In the figure, 1 and 2 are optical fibers, la and 2a are end faces of the optical fibers, 13 is a magnetic body part, and 20 is a ground cable.

Claims (1)

[Claims] (1) 1 arranged so that the end faces face each other with a gap in between
A pair of optical fibers is provided, and a magnetic body part is attached to one side of the pair of optical fibers and moves by a magnetic field generated when a ground fault current flows. A ground fault current detection sensor that detects ground fault current by changing the width of the gap.