JPH0528056B2 - - Google Patents

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a device for detecting arc light generated in a container of a gas insulated switchgear using an optical fiber sensor to determine whether or not a ground fault has occurred. .

[Technical Background of the Invention] In substations or switchyards installed around large cities or coastal areas, electrical equipment constituting the substation or switchyard is moved to SF due to difficulty in obtaining land or to prevent salt damage. Gas insulated switchgear sealed with an insulating medium such as ₆ gas that has excellent insulation and arc extinguishing properties is used. In this type of gas-insulated switchgear, disconnectors, disconnectors, and other necessary equipment are arranged three-dimensionally to reduce the distance between each piece of equipment, thereby significantly reducing the site area. Therefore, it can be configured to be significantly smaller than an air insulation type switchgear.

By the way, it is generally known that the majority of failures in power transmission lines are recoverable due to arcing, etc., and only 10% of all failures result in permanent failures. Therefore, in many cases, power transmission can be continued intermittently by immediately cutting off a faulty power transmission line, making the line voltageless, and then transmitting power to that section again. In this way, when a ground fault occurs in an overhead line, the disconnector is temporarily opened and then closed again to keep the power outage short. However, if a ground fault occurs between the metal container and the busbar in gas-insulated switchgear,
Again, since it is impossible to restore the insulation,
It was necessary to reliably detect a ground fault and issue a signal to prevent the circuit breaker from reclosing to prevent a major accident.

Conventionally, methods used to detect the occurrence of ground faults in gas-insulated switchgear include methods that detect decomposition products produced by arcs generated inside metal containers, or There was one that investigated fluctuations in gas pressure inside a container. However, the above-mentioned method has the drawback that the arc generated by a ground fault cannot be detected unless it exceeds a certain level, and is therefore unreliable.

Therefore, in order to eliminate such drawbacks of conventional ground fault detection devices, a method for optically detecting ground faults has been devised. This device uses a light-receiving sensor to directly receive the arc light associated with a ground fault occurring inside a metal container, and guides the optical signal to the optical/electrical converter via an optical cable to detect a ground fault. .

FIG. 3 shows the above-mentioned optical ground fault detection device.
That is, at one end of the optical fiber sensor 1 that receives the ground fault arc light, a plastic condensing lens 2 formed in a substantially hemispherical shape is provided to have a condensing effect. The end is connected to an optical-to-electrical converter 6 that converts the transmitted optical signal into an electrical signal and outputs it to an external control panel.

Conventionally, the optical ground fault detection device configured in this manner has been disposed on the side wall of the metal container 7, as shown in FIG. Then, the metal container 7 and the conductor 8
Ground fault arc light 9 caused by a ground fault accident that occurred during the test was detected.

[Problems with the background technology] In this technology, it has been proposed to provide a substantially hemispherical condensing lens on the detection side end face of an optical fiber sensor and guide the light collected by this lens to the sensor. However, in order to obtain a highly sensitive detection device, it is best to arrange the light guiding portion of the sensor so that it is located at the focal length of the condensing lens.

By the way, when the light guide part of the sensor is placed at the focal length position like this, in order to guide the light from the lens to the sensor, the core line of the sensor must be coaxial with the condensing spot of the lens. Since the diameter of the core wire of the sensor is extremely thin, approximately 200 to 250 μm, it is difficult at the current technological level to reliably align the axes, and misalignment is likely to occur.

In this case, as shown in FIG. 5, if the axis of the light guide portion 1a of the sensor 1 deviates from the focal point F by more than the core wire diameter d,
The light 3 collected by the lens 2 cannot be guided to the sensor 1, making it impossible to detect a failure point.

[Object of the Invention] The present invention was proposed in order to eliminate the drawbacks of the prior art as described above. By configuring it so that it can guide light to the sensor and maintain a constant sensitivity even when
It is an object of the present invention to provide an excellent optical ground fault detection device capable of quickly detecting the occurrence of a ground fault inside a gas insulated switchgear and preventing the triggering of a major accident.

[Summary of the Invention] The optical ground fault detection device of the present invention has a light guide section at the end of the optical fiber sensor that is slightly shifted forward and backward in the axial direction of the lens from the focal length of the lens. By expanding the light irradiation area on the plane of the light section, we have made it possible to guide light to the sensor and maintain a constant sensitivity even if the axis of the light guide section at the end of the sensor deviates from the light condensing spot. This is what I did.

[Embodiments of the Invention] Next, embodiments of the optical ground fault detection device according to the present invention as described above will be described. FIG. 1 shows an embodiment in which the light guide portion 1a at the end of the optical fiber sensor 1 is arranged to be slightly shifted rearward in the axial direction of the lens 2 from the focal length of the lens 2. The sensor 1 is composed of a core 4 at the center and a cladding 5 at the outer periphery.
Furthermore, an optical/electrical converter (not shown) is connected to the other end of the optical fiber sensor 1.

In FIG. 1, light 3 on the plane of the light guide 1a
The light 3 can be reliably guided to the sensor 1 by setting the irradiation range l to be larger than the possible axis deviation of the light guide portion 1a. In this case, although the sensitivity is slightly lower than the method of matching the light guide portion 1a with the focal length of the lens 2, the level of sensitivity required for detection is sufficiently maintained.

The light 3 guided to the optical fiber sensor 1 is outputted as an electrical signal by the optical-to-electrical converter, and the presence or absence of an accident is determined based on this signal.
Therefore, when a ground fault occurs inside the gas insulated switchgear, the occurrence of the fault can be detected quickly and reliably using the arc light, thereby preventing a major accident.

Further, FIG. 2 shows an embodiment in which the light guide portion 1a is arranged slightly forward in the axial direction of the lens 2 from the focal length of the lens, and its operation and effect are the same as in the previous embodiment.

In addition, in the present invention, an optical-to-electrical conversion section is connected to the other end of the optical fiber sensor, and the configuration of the determination section that inputs the signal and executes various programs for accident determination or accident processing is different. can be selected as appropriate.

[Effects of the Invention] As explained above, according to the present invention, the light guiding portion of the optical fiber sensor is slightly shifted back and forth in the axial direction of the lens from the focal length of the lens, so that
Even if there is a certain degree of misalignment between the axis of the sensor and the axis of the condensing spot, it is possible to quickly detect the occurrence of a ground fault inside the gas-insulated switchgear and prevent the triggering of a major accident. It is possible to provide an excellent optical ground fault detection device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a photodetector in one embodiment of the optical ground fault detection device according to the present invention, and FIG. 2 is a sectional view showing the photodetection portion in another embodiment of the optical ground fault detection device according to the present invention. 3 is a partial sectional view showing a conventional optical ground fault detection device, FIG. 4 is a sectional view showing the state of ground fault detection in the conventional optical ground fault detection device, and FIG. The figure is a sectional view showing a photodetector section of a conventional optical ground fault detection device. 1... Optical fiber sensor, 1a... Light guide section,
2...Lens, 3...Light, 4...Core, 5...Clad, F...Focus.

Claims (1)

[Claims] 1. One end of the optical fiber sensor is installed in a container of a gas-insulated switchgear, and a substantially hemispherical lens for condensing arc light is provided in front of this end to constitute a light detection section. , an optical ground fault detection device in which the other end of the optical fiber sensor is connected to an optical/electrical exchange section provided outside the container, in which a light guide section at the end of the optical fiber sensor in the light detection section is connected to a lens. An optical ground fault detection device characterized by being placed at a position slightly shifted forward and backward in the axial direction of the lens from the focal length.