JPH04296409A - Optical fiber built-in bushing - Google Patents

Abstract

PURPOSE:To provide a bushing able to measure a temperature under practical operation. CONSTITUTION:Optical fibers 6 are passed into the inside of a central conductor 1 from the upper and lower oil flow openings 2, 3 of the tubular central conductor 1 of a bushing for going round, and both end parts thereof are taken outside from the earthing part 7 of the bushing in order to join an optical transmitter and an optical receiver 9. When a laser pulse is sent inside the optical fibers 6, intensity of scattered light changes according to a temperature, so that the inside temperature distribution can be known when a distance is known from a reflection time. Since the optical fibers 6 are insulator, temperature measurement can be performed in a charge state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bushing with a built-in optical fiber that has a function of measuring temperature under actual operating conditions.

0002

[Prior Art] When a bushing is energized, the center conductor generates heat due to Joule heat, and the capacitor core wound around the center conductor generates dielectric heat during energized operation in proportion to the dielectric loss tangent of its constituent insulating materials. Therefore, the temperature of the bushing increases. The temperature must be kept to a level that does not deteriorate the capacitor core or oil, for example, 105° C. or lower for an oil-immersed paper capacitor core that is Class A insulation. However, due to technical constraints in the insulation design of high-voltage bushings, there is no way to properly monitor the temperature inside the bushing. , provided for realistic driving.

[0003] In the above type test, temperature is verified through a rated current under typical ambient conditions, ie, the maximum expected air temperature and immersion oil temperature. Thermocouples are often used to measure temperature during this test, but with high-voltage bushings, it is impossible to apply current with a thermocouple attached inside due to insulation performance, so the temperature rise due to the energizing current cannot be applied. All I could do was confirm. Furthermore, since the ambient conditions change during actual operation, the temperature under actual operation cannot be clearly determined. The bushing specifications set the upper limit to conditions where both the air temperature and the immersion oil temperature are at their highest, and the rated performance is evaluated under these conditions. Therefore, in reality, overloading should be possible, but it is often not possible due to lack of data, and as a result, in most cases, bushings have to be operated with a margin for temperature rise, which is uneconomical. Met.

Furthermore, one of the deteriorations of the capacitor core due to long-term operation is a phenomenon in which the dielectric loss tangent gradually increases due to thermal deterioration. In this case, the amount of dielectric heat generated gradually increases with use. Therefore, the older the bushing is, the more it is necessary to reduce the allowable amount of current, but at present there is no way to know the guideline, and if used without knowing it, it will overheat and this overheating will further accelerate deterioration, resulting in the phenomenon of heat loss. There was a risk of causing

[0005]

[Problems to be Solved by the Invention] The present invention has been completed in order to solve the above-mentioned conventional problems and provide a bushing with a built-in optical fiber that can accurately measure the temperature inside the bushing under actual operating conditions. It is something.

[0006]

[Means for Solving the Problems] The present invention, which has been made to solve the above problems, involves inserting an optical fiber into the interior of the central conductor from one of the upper and lower oil flow ports of a tubular central conductor, and It is characterized in that it is pulled out from the flow port, and both ends of the bushing are taken out from the grounding part of the bushing to connect an optical transmitter and an optical receiver. These optical transmitters and optical receivers have a function of measuring the temperature distribution inside the bushing from the intensity of light scattering within the optical fiber, which changes with temperature, and the time it takes for the scattered light to return.

[0007]

[Operation] In the present invention, the intensity of scattering of the light beam sent from the optical transmitter into the inside of the optical fiber changes depending on the temperature inside the optical fiber, and the time it takes for the scattered light to return to the inside of the optical fiber changes. The temperature distribution inside the center conductor of the bushing can be measured by utilizing the fact that the temperature varies depending on the distance from the end. Furthermore, since the optical fiber is an insulator, the temperature of the center conductor can be constantly measured even during power application, and the load can be adjusted according to the measured temperature. Furthermore, even if dielectric heat generation increases due to an increase in dielectric loss tangent due to long-term insulation deterioration, this can be accurately known, and the risk of overheating can be prevented.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to illustrated embodiments. FIG. 1 shows a first embodiment of the present invention.
is a tubular central conductor, and oil flow ports 2 and 3 are provided above and below it. The oil inside the center conductor 1, which is heated by the energization heat generation of the center conductor 1 and the dielectric heat generation of the capacitor core 4, rises and flows to the outside of the center conductor 1 from the upper oil flow port 2, where the temperature is lowered by the outside air. The heat is radiated on the inner surface of the insulator tube 5 and enters the center conductor 1 again from the lower oil flow port 3. This convection circulation effect allows the bushing to efficiently dissipate heat to the outside.

By inserting the optical fiber 6 through one of the oil flow ports 2 and 3 of the center conductor 1 and pulling it out from the other oil flow port, the optical fiber 6 is made to go around the center conductor 1 once. Both ends of the optical fiber 6 are taken out from the grounding part 7 of the bushing and connected to an optical transmitter and an optical receiver 9 via an optical coupler 8. In this embodiment, the optical fiber 6 consists of a silica matrix containing a specific doping agent, for example germanium.

When laser pulse light is sent from one end of the optical fiber 6, the laser pulse light interacts with the silica and doping agent as it travels through the optical fiber 6, generating energy that is equally scattered in all directions. The intensity of the laser Raman scattered light within this optical fiber 6 is
The intensity of backscattered light increases as the temperature increases. Some of this scattered light returns to the light source, but the round trip time is proportional to the distance, so by measuring the time and intensity of the scattered light returning, you can measure the temperature depending on the location. becomes possible. Since the position is determined when the optical fiber 6 is first installed, it is possible to know which part of the bushing has which temperature. The temperature distribution measured in this way is continuous, and other measurement methods (e.g. the method of embedding a temperature-sensitive element)
Unlike others, there are no positional measurement omissions.

FIG. 2 shows a second embodiment of the present invention, in which an optical fiber 6 is made to go around the center conductor 1 in the same manner as described above, and an optical transmitter 9a is connected to both ends of the optical fiber 6 via an optical coupler 8.
and an optical receiver 9b. Also, as shown in Figure 3,
In the middle of the optical fiber 6 in the center conductor 1, there is a thin semiconductor 10 whose light transmittance changes depending on the temperature, such as CaAs or CdT.
e etc. are interposed. When the light emitted from the optical transmitter 9a passes through the semiconductor 10, it is attenuated according to the light transmittance determined by the temperature of that part, and returns to the optical receiver 9b. The center conductor 1 of the bushing depends on the intensity of the returned light.
You can know the internal temperature of. In this case, the temperature measured is the temperature at the point where the semiconductor 10 is installed, so the positional discrimination accuracy is good, and by appropriately arranging multiple pieces, it is not only possible to know the temperature inside the bushing. By installing it outside as necessary, it becomes possible to know the temperature distribution at various points along the circuit route, and it is possible to obtain a wealth of information for determining operating conditions.

It should be noted that if the oil flow ports 2 and 3 are made too large, the electric field in those portions is likely to be disturbed, so it is desirable to have a small diameter, and they are set to an appropriate size in consideration of the flow of oil. For this reason, it should be avoided as much as possible to block this part with the optical fiber 6, but in the present invention, since the temperature distribution of the entire bushing can be known with one optical fiber 6, the oil flow ports 2, 3 There is no risk of loss of functionality.

[0013]

As explained above, according to the present invention, it is possible to accurately measure the internal temperature of the bushing in an actual operating state where Joule heat and dielectric heat generation occur simultaneously due to energization and charging, thereby reducing the temperature rise. This makes it possible to operate near the limits of the equipment, increasing equipment efficiency. Furthermore, according to the present invention, even if the degree of heat generation changes due to an increase in dielectric loss tangent due to deterioration of the insulating material due to long-term operation, the degree of heat generation can be constantly monitored accurately, so damage caused by overheating can be prevented. can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the invention.

FIG. 3 is an enlarged sectional view of a semiconductor mounting portion in a second embodiment.

[Explanation of symbols]

1 Center conductor 2 Oil flow port 3 Oil flow port 6 Optical fiber 7 Grounding part 9. Optical transmitter and optical receiver 10 Semiconductor

Claims (3)

[Claims] [Claim 1] An optical fiber is inserted into the center conductor through one of the upper and lower oil flow ports of the tubular center conductor, pulled out from the other oil flow port, and both ends of the optical fiber are taken out from the grounding portion of the bushing. A bushing with a built-in optical fiber characterized by connecting an optical transmitter and an optical receiver. 2. The light according to claim 1, which has a function of measuring the temperature distribution inside the bushing from the intensity of light scattering within the optical fiber that changes depending on temperature and the time taken for the scattered light to return. Bushing with built-in fiber. 3. It has a function of inserting a semiconductor whose light transmittance changes depending on temperature into the middle of the optical fiber located in the center conductor, and measuring the temperature distribution inside the bushing based on the change in the light transmittance of the semiconductor. The optical fiber built-in bushing according to claim 1.