JPH0546161B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a current transformer used, for example, in a three-phase integrated type gas-insulated switchgear, and in particular, a current transformer configured with a magneto-optical field sensor having a magneto-optical effect. Regarding gas insulated current transformers.

[Technical background of the invention]

Conventionally, a gas-insulated three-phase current transformer used, for example, in a three-phase all-in-one type gas-insulated switchgear is configured with an iron-core type current transformer core made by winding a coil around a silicon steel plate.

An example of such a conventional gas-insulated three-phase current transformer will be explained with reference to FIG. Three-phase conductors 2u to 2w of u, v, and w phases are arranged in a cylindrical tank 1. Insulating spacers 3 are provided before and after the tank 1, and the conductors 2u to 2w are supported by these. The tank 1 is divided into front and rear parts perpendicular to its axis, with the tank 1 having the original diameter at the front.
a, and a tank 1b located at the rear and having a diameter increased by the dimension of the current transformer core 4. Conductors 2u to 2w at the inner end of this tank 1b
A current transformer core is installed on each extension. A support plate 5 is provided in front of the current transformer core 4 (that is, at the end of the rear tank 1b), and an insulating shield 6 is provided inside the current transformer core 4 in connection with this. , these support the current transformer core 4 and insulate it from the conductors 2u to 2w. Furthermore, a sealed terminal 7 is provided at the bottom of the tank 1 for drawing out the current from the current transformer core 4.

By the way, in such a gas-insulated three-phase current transformer, the current transformer cores installed at three locations are heavy, so the supporting plates, insulation shields, etc. that support them are also quite large, and in order to install these at three locations, As a result, equipment becomes more complex, larger, and heavier. Furthermore, since one current transformer core can be used for only one purpose, multiple cores are required for relays, measurements, etc., which also causes an increase in size and increases cost.

In view of these shortcomings, measurement technology using optical fibers, which have excellent characteristics such as small diameter, insulation, non-induction, and environmental resistance, has recently attracted attention, and optical magnetic field sensors that apply this have attracted attention. Attempts have been made to construct a flow vessel.

An example of a gas-insulated three-phase current transformer using such an optical magnetic field sensor will be explained with reference to FIGS. 4 and 5.

Three-phase conductors 2u to 2w arranged in tank 1
is provided with an optical magnetic field sensor 8 on its high electric field side, and a sealed terminal 7 is installed on the outside of the tank 1 on this extension.
is provided. The optical magnetic field sensor 8 mainly consists of a Faraday element such as ZnSe, a polarizer, a 1/4 wavelength plate, an analyzer, etc., and the sealed terminal 7 consists of an optical transmitter LED, an optical receiver PD, and an operator OP. It is connected to a detection device 10 via an optical fiber cable 9. Here, the optical magnetic field sensor 8 is the fifth
As shown in the figure, a plurality of magnetic fields are provided around each of the conductors 2u to 2w, and the magnetic field in the concentric tangential direction centered on the axis of the conductor is measured, and based on the approximation formula of the circumferential integral, based on Ampere's theorem, the central conductor is It is designed to measure the current.

The operation of this gas-insulated three-phase current transformer is as follows. That is, when light is sent from the optical transmitter to the optical magnetic field sensor 8 via the sealed terminal 7, this light first passes through a polarizer, changes from random polarization to linear polarization, and becomes 1/
It undergoes phase modulation with a four-wave plate and becomes circularly polarized light. When passing through the Faraday element, it becomes elliptically polarized light according to the magnitude of the magnetic field, is intensity-modulated by the analyzer, returns to the sealed terminal 7, and is sent to the optical receiver connected to the detection device. is extracted as optical power, and an output proportional to the magnitude of the magnetic field is extracted through arithmetic processing.

Since the optical magnetic field sensor has excellent insulation properties, it can be placed near the conductors 2u to 2w as described above, and the sealed terminal 7 can also be miniaturized. As a result, the gas-insulated three-phase current transformer is significantly smaller and lighter. Specifically, there are examples where the length was reduced by about 20% and the diameter by about 60%. Also,
Optical magnetic field sensors can freely multiplex signals, so
Unlike the conventional technology, which requires multiple cores for different uses, just one sensor is provided and can be used for multiple purposes. Therefore, in this regard,
It is possible to further downsize and simplify the current transformer, and the cost is also low.

[Problems with background technology]

However, in such conventional current transformers, the direction of the magnetic field detected by each optical magnetic field sensor is the tangential direction of a concentric circle centered on the axis of the conductor. When the conductors are arranged,
Easily affected by components perpendicular to the conductor axis direction due to adjacent phases. That is, in FIG. 6, the u-phase conductor 2u
Considering the current of The magnetic fields due to the currents in the phase conductors 2u are combined. This means that the v-phase and w-phase conductors 2
The same is true when considering v and 2w, and the magnetic field of each conductor has a complicated aspect. Therefore, when an optical magnetic field sensor is provided near a conductor to measure the current and phase of the conductor, the accuracy of the measured data will be significantly reduced unless the effects of other phase magnetic fields are eliminated.

In particular, the fault current can reach up to 25 times the normal current, and although the magnetic field decreases in inverse proportion to the distance, it is inevitable that it will affect the measurement accuracy of the optical magnetic field sensor of the adjacent phase. do not have.

In this way, in a conventional current transformer in which an optical magnetic field sensor is installed around a conductor and circuit integration is performed for the component perpendicular to the conductor axis direction of the magnetic field, the magnetic field of the measurement phase is affected by the magnetic field of the adjacent phase. Since the image is distorted, this appears as a measurement error, creating a problem in which highly accurate measurements cannot be carried out.

In addition, when a magneto-optical field sensor is arranged around a conductor to perform circuit integration, the area around the conductor protrudes by the amount of the magneto-optical sensor, and in order to improve accuracy, the magneto-optical field sensor is placed around the entire circumference of the conductor. In this case, it is necessary to use a larger optical magnetic field sensor, which makes manufacturing the sensor extremely difficult and increases its weight.

Furthermore, the optical magnetic field sensor is a passive element and requires one or two optical fiber cables for the incident light and the output, and if there are many sensors like in the conventional type, the number of cables will also increase. When looking at the three-phase collective bus as a whole, the number of gas-tight parts at its connection points and through the ground tank has increased, resulting in an increase in the number of component parts and a decrease in reliability.

In order to solve the problems of the prior art as described above, the inventor first developed a unidirectional sensor that enables highly accurate measurement without being affected by the magnetic field of adjacent phases, and that does not require circular integration. We have developed a highly reliable gas-insulated three-phase current transformer with a small number of parts.

In other words, a hollow coil section is formed in the part of the conductor of each phase where the optical magnetic field sensor is installed, a magnetic field is generated in the axial direction of the conductor within this coil section, and this magnetic field is transmitted along the axial direction within the coil section. By detecting with a unidirectional optical magnetic field sensor provided, measurement is performed without being influenced by the magnetic field generated in the adjacent phase in the direction perpendicular to the conductor axis.

In particular, by forming the coil part with at least two turns or more, the direction of the magnetic field formed in the coil part is made to match the axial direction of the conductor as much as possible, so that the optical magnetic field sensor can detect the axial magnetic field with high precision. It was made so that it could be done.

However, the above-mentioned current transformer in which the optical magnetic field sensor is housed in the coil section has problems due to the insulation distance between the coil section, which is the energizing section, and the tank in which it is housed.
Since the cross section of the coil conductor cannot be made large, there is a concern that the temperature rise in the coil portion may not be suppressed within a predetermined value when considering application to large current energization. In other words, for large current ratings such as 6000A/8000A, the conductor is made of Al and the coil part is made of Cu.
Even if it is formed using a uniformly conductive material, there is a possibility that the temperature rise value of the coil portion will exceed a specified value, and it is desired to solve this problem.

[Purpose of the invention]

The present invention has been made in order to satisfy the above-mentioned needs, and aims to provide a gas-insulated current transformer that can suppress the temperature rise in the coil section, in particular, in a device in which an optical magnetic field sensor is housed in the coil section. This is the purpose.

[Summary of the invention]

According to the present invention, in order to achieve such an objective,
The conductor close to the coil section is provided with a heat suction means, specifically a heat pipe, etc., for actively transmitting the heat of the coil section to the adjacent conductor and suppressing the rise in temperature of the coil section.

[Embodiments of the invention]

Hereinafter, a first embodiment of the present invention will be specifically described with reference to FIG. 1 and FIGS. 2A and 2B.

Figures 2 A and B show a space transmission type current transformer that uses the space inside the tank as it is to transmit signals between the optical magnetic field sensor and the detection device on the tank side, without using fiber optic cables. This is an example in which the present invention is applied to. Also, a three-phase all-in-one type will be explained.

In this embodiment, a three-phase collective grounding tank 1
1 includes conductors 12u to 12 for each phase of u, v, and w.
w are arranged in parallel along the axial direction of the tank 11. Each of these conductors 12 is a cylindrical hollow conductor, and a coil portion 13 having a hollow interior is formed along the axial direction of the conductor 12 in the portion where the optical magnetic field sensor is disposed. This coil part 13
is formed by winding a rod-shaped conductor with at least two turns. An optical magnetic field sensor 14 having a Faraday element is disposed in the hollow portion of the coil portion 13 so as to have maximum sensitivity to the magnetic field in the axial direction of the conductor 12.

The optical magnetic field sensor 14 is a unidirectional sensor that measures a linear magnetic field, and its shape is a straight rod along the axial direction of the conductor 12. The optical magnetic field sensor 14 is positioned on the central axis of the coil section 13 via a support 15 that is fixed to the end of the cylindrical conductor 12 connected to the coil section 13 and protrudes into the coil section 13. It is fixed as follows.
A prism 14a that bends the light transmitted and received between the detection device 16 fixed to the tank 11 and the axial direction of the sensor (the axial direction of the conductor) is attached to the side surface of the end of the optical magnetic field sensor 14 on the support stand 15 side. Furthermore, a reflective surface 14b for light from the prism 14a is provided at the end of the optical magnetic field sensor 14 opposite to the support base.

A detection device 16 fixed to the tank 11 is provided at a sealed terminal 17 that penetrates the tank 11, and is composed of an optical oscillator (light emitting diode) LED, an optical receiver (photodiode) PD, and an operator 16a.

Here, the cylindrical conductor 1 connected to the coil part 13
2 will be explained in more detail. In FIG. 1 and FIG. 2B, the first embodiment will be explained using the conductor on the left side of the coil portion 13, and the second embodiment will be explained using the conductor on the right side.
In the first embodiment, a heat pipe 120A is housed inside a hollow conductor. The heat pipe is placed in close contact with the end of the conductor 12, that is, on the side of the coil portion 13. Further, in the second embodiment, a heat pipe 120B forming a conductor is connected to the connection between the conductor 12 and the coil portion 13.
Therefore, the coil portion 13 is connected to the conductor 12 via the heat pipe 120B.

In the current transformer of this embodiment having such a configuration, the light emitted from the optical transmitter LED of the detection device 16 is as follows.
The linearly polarized light is linearly polarized by a polarizer (not shown), and the linearly polarized light is spatially transmitted inside the tank 11, and the prism 1
The light enters the optical magnetic field sensor 14 from 4a, and then is sent into the optical magnetic field sensor 14 at the reflective surface 14b. Then, in the Faraday element of the optical magnetic field sensor 14, after being rotated by a predetermined Faraday angle due to the magnetic field applied thereto, it is spatially transmitted again via the prism 14a, inputted to the optical receiver PD as a change in the amount of light, and electrically transmitted from the operator 16a. Extracted as a signal.

In the current transformer of this embodiment, as shown in _FIG .
A magnetic field φ ₁ is generated around the center of the axis, but since there is a current i ₂ flowing while rotating in the coil portion 13, the direction of the magnetic field φ ₂ in the internal space of the coil is almost parallel to the axial direction of the conductor 12 and is coaxial. Therefore, it is perpendicular to the magnetic field φ ₃ due to the current i ₃ flowing through the conductor of the adjacent phase, and is not affected by the magnetic field of the adjacent phase. In particular, in this embodiment, by providing at least two turns in the conductor of the coil portion 13, the direction of the magnetic field within the coil portion 13 between each turn is made linear, so that the influence of the magnetic field of the adjacent phase is effectively reduced. can be excluded.

On the other hand, when considering the temperature rise in the conductor 12 and the coil portion 13 when energized, the temperature rise in the coil portion 13 is more significant than that of the conductor 12 connecting the coil portion 13 from the viewpoint of current carrying capacity. However, in the present invention, heat pipes 120A and 120B, which are heat suction means capable of actively transferring heat generated from the coil section 13, are provided on both sides of the coil section 13, so that the temperature of the coil section as a whole increases. It is possible to suppress the increase in current, and it becomes possible to use it as a current transformer with a large current rating.

As described above, the gas insulated current transformer according to the present invention has
A magnetic field parallel to the axial direction of the conductor is generated by a coil section made of at least two turns of a conductor, which is detected by an optical magnetic field sensor to measure the current. The configuration is not limited to that shown in the drawings.

For example, the number of turns of the conductor in the coil part is not limited to two turns; if the number of turns is increased, the magnetic field strength in the optical magnetic field sensor part can be increased.
The influence of other phase magnetic fields is correspondingly reduced, and even if there is some misalignment between the optical axis of the optical magnetic field sensor and the coil center axis, highly accurate magnetic field measurement can be performed.

Moreover, although the three-phase current transformer has been described, it goes without saying that a single-phase current transformer may also be used.

Furthermore, in the case of a three-phase all-in-one type, it is also possible to arrange the coil portions to be shifted in the axial direction of each conductor by at least the length of the coil portion. In this case, it is possible to reduce the coil diameter.

〔Effect of the invention〕

As described above, according to the present invention, a unidirectional type optical magnetic field sensor is provided in a coil portion formed in a part of a conductor, and a heat suction means is provided in a portion of the conductor to which the coil portion is connected, which is close to the coil portion. With this simple configuration, it is possible to provide a gas insulated current transformer that can perform highly accurate measurements and can also be applied to large current ratings. In addition, at least two conductors constituting the coil part
By forming a turn to generate a linear magnetic field along the axial direction of the conductor within the coil, in the case of a three-phase all-in-one type, it is not affected by the magnetic field of other phases, and moreover, it is a unidirectional type. This has the effect of enabling the use of optical magnetic field sensors.

In addition, by using a unidirectional type magneto-optical field sensor, the size of the magneto-optical field sensor can be made smaller and easier to manufacture.Furthermore, by reducing the number of magneto-optical sensors, the number of fiber cables connected to it can also be reduced. Therefore, it has the effect of simplifying the configuration of the current transformer.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the state of the magnetic field of a gas-insulated current transformer according to the present invention, FIGS. 2A and B are sectional views and side views showing one embodiment of the present invention, and FIGS. 3A and B are conventional Figures 4A and 4B are front and side views showing an example of a gas-insulated three-phase current transformer using a current transformer core. A side view, Fig. 5 is a cross-sectional view of a gas-insulated three-phase current transformer using an optical magnetic field sensor based on orbital integration, and Fig. 6
The figure is a cross-sectional view showing the influence of other-phase magnetic fields on a gas-insulated three-phase current transformer. 1, 1a, 1b...Tank, 2u~2w...Conductor,
3... Insulating spacer, 4... Current transformer core, 5... Support plate, 6... Insulating shield, 7... Sealed terminal, 8... Optical magnetic field sensor, 9... Optical fiber cable, 10... Detecting device, 11... Tank, 12... Cylindrical conductor, 13...
Coil part, 14... Optical magnetic field sensor, 15... Support stand,
16... Detection device, 16a... Operator, 17... Sealed terminal, 20... Volt, 21... Optical fiber cable, 22... Sealed terminal, 23, 24... Insertion hole,
LED...Optical transmitter, PD...Optical receiver, 120A, 1
20B...Heat pipe.

Claims (1)

[Claims] 1. A conductor is placed in a tank filled with an insulating gas such as SF ₆ gas, and the conductor is wound at least two turns to form a hollow conductive coil portion. A magnetic field in the axial direction of the conductor is generated within this coil section, and a unidirectional optical magnetic field sensor for detecting the magnetic field in the axial direction is disposed within this coil section, and there is no magnetic field on or outside the tank. , a detection device for each phase consisting of an optical transmitter, an optical receiver, and an operator is disposed, and the configuration is such that light is transmitted between the detection device and the optical magnetic field sensor, and the detection device is arranged close to the coil section. A gas insulated current transformer characterized in that the conductor is provided with heat suction means for suppressing temperature rise in the coil section. 2. The gas insulated current transformer according to claim 1, wherein the light transmission means between the detection device and the optical magnetic field sensor is based on spatial transmission of light. 3. The gas insulated current transformer according to claim 1, wherein the coil portions of each phase are disposed at positions shifted by at least the length of the coil along the axial direction of the conductor. 4. Claim 1, wherein the heat suction means applied to the conductor is a heat pipe housed within the conductor.
Gas insulated current transformer as described in Section. 5. The gas insulated current transformer according to claim 1, wherein the heat suction means applied to the conductor comprises a heat pipe in a portion connected to a coil portion of the conductor.