JPS6275362A - Optical current transformer - Google Patents

Abstract

PURPOSE:To enable highly accurate measurement without being affected by a magnetic field of an adjacent phase, by forming a ring section at a part of a cylinder conductor through which current to be measured flows to detect an axial magnetic field of the cylinder conductor being generated at a hollow section. CONSTITUTION:Cylinder conductors 9u-9w in respective phases u-w are arranged in a tank 8 along the axis thereof 8 and a ring section 19 is formed at a desired position in the axial direction of the conductors 9u-9w. An optomagnetic field sensor 11 is fixed at the end of the conductors 9u-9w connected to the ring section 19 through a support base 12 so as to be positioned on the center axis of the ring section 19. An axial magnetic field of the conductors 9u-9w generated at a hollow part in the ring section 19 is detected with the sensor 11 to eliminate effects of a magnetic field of an adjacent phase thereby enabling highly accurate measurement. Thus, a smaller and lighter optical current transformer is made possible as compared with a gas insulated current transformer using a current transformer core.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is used, for example, in a gas-insulated switchgear, and includes a magneto-optical field sensor having a magneto-optical effect disposed within a ring portion formed as a part of a high-voltage side conductor. Regarding optical current transformers.

[Technical Background of the Invention] Conventionally, gas-insulated current transformers used in gas-insulated switchgear have been constructed 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 current transformer is shown in Figure 8 (A>
, (B) will be explained by taking as an example a three-phase collective type gas-insulated three-phase current transformer.

Inside the cylindrical tank 1 are three-phase conductors 2u of U, V, and W phases.
~2W is installed. Insulating spacers 3 are provided before and after the tank 1, and the conductors 2u to 2W are supported by these spacers. The tank 1 is divided into front and rear parts perpendicular to its axis, and consists of a tank 1a at the front having the original diameter and a tank 1b at the rear having a diameter increased by the dimension of the current transformer core 4. has been done. Current transformer cores are installed on the extensions of the conductors 2u to 2W at the inner end of the tank 1b, respectively. 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 provide insulation from the conductors 20 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 current transformer, since the current transformer core 4 provided in each phase is heavy, a support plate 5, which supports it, is required.
The insulating shield 6 and the like are also quite large, and in a three-phase all-in-one type, they are provided in three locations, making the device complicated, large, and heavy. In addition, since one current transformer core 4 can only be used for one purpose, multiple current transformer cores 4 are required for each purpose, such as for relays and measurements, which also causes an increase in size. It also becomes expensive.

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. Attempts are being made to construct vessels.

An example of a conventional optical current transformer using such an optical magnetic field sensor will be explained according to FIG. 9 (A>, (B) and FIG. 10). Cylindrical conductor 9u~9
w (hereinafter collectively referred to as 9) are arranged in parallel along the axial direction of the tank 78. A space for arranging a coiled conductor is formed at a desired position in the axial direction of each of the cylindrical conductors 9, and a coiled conductor 10 in which a rod-shaped conductor is wound at least two turns is formed in this space. are arranged, and both ends thereof are fixed to the ends of the conductor 9 by bolts 14. In the hollow part of this coiled conductor 10, an optical magnetic field sensor 11 is arranged in a sphere having maximum sensitivity to the magnetic field in the axial direction of the cylindrical conductor 9. The optical magnetic field sensor 11 is a unidirectional sensor that measures a linear magnetic field, and is mainly composed of a Faraday element such as Zn5e, a polarizer, an analyzer, etc., and its shape also follows the axial direction of the cylindrical conductor 9. It has a straight rod-shaped body. This optical magnetic field sensor 11 includes a cylindrical conductor 9 connected to a coiled conductor 10.
The coiled conductor 10
It is fixed so that it is located on the central axis of.

On the other hand, a detection device 13 is disposed outside the tank 8 and is housed in a gas-insulated switchgear control panel and is composed of an optical transmitter 13a, an optical receiver 13b, and a calculator 130. 13 and the optical magnetic field sensor 1 in the tank 8
1 are optically connected by an optical fiber cable 15. In this case, the optical fiber cable 15 penetrates the tank 8 at the sealed terminal 16 in a gas-tight manner, and has an insertion hole 17 opened in the wall surface of the cylindrical conductor 9, and an end portion of the cylindrical conductor 9 and a coiled conductor. The optical magnetic field sensor 11 is connected to the optical magnetic field sensor 11 through an insertion hole 18 provided at the end of the optical sensor 10 .

As shown in FIG. 9(B), the location of the magneto-optical field sensor 11, that is, the position of the coiled conductor 10, is approximately equal to the length of the coiled conductor 10 in the longitudinal direction of each cylindrical conductor 9 of each phase. They are placed slightly apart.

The operation of the optical current transformer constructed in this way is as follows. Light guided from the optical transmitter 13a of the detection device 13 into the tank 8 via the optical fiber cable 15 becomes linearly polarized light by a polarizer in the optical magnetic field sensor 11, and is incident on a Faraday element. Then, an axial magnetic field is generated in the coiled conductor 10 by energization, and after the polarization plane of the light incident on the Faraday element is rotated by an angle proportional to the magnitude of the magnetic field applied to the Faraday element, the light is transmitted through the analyzer. The light whose intensity depends on the rotation of the plane of polarization is again input to the optical receiver 13b through the optical fiber cable 15, and is extracted as an electrical signal from the arithmetic unit 13C. In this case, the first
As shown in Figure 0, a current 11 flows in the axial direction of the cylindrical conductor 9, and a magnetic field φ1 with a component perpendicular to the axial direction is generated around the cylindrical conductor 9. Since L1 is a current 12 that flows while rotating in the coiled conductor 10, the direction of the magnetic field φ2 in the coil space is approximately parallel and coaxial with the axial direction of the cylindrical conductor 9, and the magnetic field due to the current L3 flowing through the conductor of the adjacent phase It is perpendicular to φ3 and is not affected by the magnetic field of the adjacent phase. Also,
By providing at least two turns of the conductor of the coiled conductor 10, the direction of the magnetic field within the coiled conductor 10 between each turn becomes linear, and the influence of the magnetic field of the adjacent phase can be effectively eliminated, thus improving accuracy. This has the advantage that high current measurement is possible.

[Problems with the Background Art] However, in the conventional optical current transformer described above, from the viewpoint of current carrying performance, even in the coiled conductor 10 disposed in a part of the cylindrical conductor 9 as the main circuit, the cylindrical conductor 9 It is necessary to have current carrying performance, that is, the ability to carry not only the rated current but also an excessive fault current for a short period of time. For this reason, it is essential that the coiled conductor 10 be made of a highly conductive material and that the conductor wire diameter of the coiled conductor 10 be large enough to carry the fault current for a short time.

Here, the method of manufacturing the coiled conductor 10 is generally to wind up a round bar material, but when the coiled conductor 10 is manufactured by winding up a round bar with a large wire diameter that satisfies the above conditions, It is inevitable that the outer diameter of the coiled conductor 10 is larger than the outer diameter of the cylindrical conductor 9 as the main circuit. Considering the interphase insulation, that is, the dielectric strength between the coiled conductor 10 and the main circuit conductor of the other phase, and the grounding insulation, that is, the dielectric strength between the coiled conductor 10 and the grounded tank 8,
Within the busbar range in which the coiled conductors 10 are disposed in three phases, the interphase distance of the three-phase conductors and the diameter of the tank 8 must be made larger than the dimensions of the surrounding busbars. In addition, in order to maintain insulation between turns of the coiled conductor 10 against electromagnetic attraction force acting between the turns of the coiled conductor 10 and thermal expansion and contraction of the cylindrical conductor 9, etc., and to always ensure the required number of turns, It is necessary to provide an appropriate interval therebetween, and the longitudinal dimension of the coiled conductor 10 increases accordingly. Furthermore, in order to suppress heat generation due to Joule heat in the coiled conductor 10 and provide sufficient current carrying performance, it is necessary and sufficient to use a highly conductive and low loss material such as copper as a member of the coiled conductor 10. However, as described above, since the coiled conductor 10 is large, this results in an increase in the mold opening.

These things are one of the main advantages of applying a current transformer configured with an optical magnetic field sensor to a gas-insulated switchgear instead of the gas-insulated current transformer described above, which is the miniaturization of the current transformer. This goes against the intention of reducing weight.

[Object of the invention] The present invention was proposed to solve the above-mentioned problems, and its purpose is to enable highly accurate measurement without being affected by magnetic fields of adjacent phases, and to be compact and lightweight. The purpose of this invention is to provide an optical current transformer that enables this.

[Summary of the Invention] In order to achieve the above-mentioned object, the present invention forms a ring portion made of a ring-shaped conductor in a part of a cylindrical conductor through which a current to be measured flows, and a hollow portion of the cylindrical conductor is formed in a hollow portion within the ring portion. By generating an axial magnetic field and detecting it with a unidirectional optical magnetic field sensor arranged along the axial direction at the center of the hollow part in the ring part, the magnetic field perpendicular to the conductor axis generated in the adjacent phase is detected. This makes it possible to measure without being influenced by

[Embodiments of the Invention] Examples of the present invention will be described below with reference to FIGS. 1 to 7.

FIGS. 1A and 1B are a front sectional view and a side sectional view showing only the main parts of an embodiment of the present invention, and as is clear from these, there are U, V, and W phases in the tank 8. Cylindrical conductor 9 for each phase
0 to 9w (hereinafter collectively referred to as one) are arranged in parallel along the axial direction of the tank 8. Each of the cylindrical conductors 9
A ring portion 19, which will be described below, is formed at a desired position in the axial direction. This ring portion 19 is shown in FIG.
As shown in the front and side views of FIGS. 3B) and 3A and 3B, there is a ring-shaped conductor 19a and one insulating plate.

It is composed of 19C. Here, in the ring-shaped conductor 19a, a current flowing from one of the cylindrical conductors 9 disposed on both sides of the ring portion 19 into the ring-shaped conductor 19a and flowing out to the other cylindrical conductor 9 forms about one turn in this part. A gap 19d is provided in a part of the annular conductor so that the conductor has a gap 19d. In addition, the insulating plates 19b and 19c insulate the turn portion of the ring-shaped conductor 19a and the cylindrical conductor 9, and protect the ring-shaped conductor 19a from external forces acting in the axial direction and circumferential direction of the cylindrical conductor 9 due to thermal expansion and contraction of the cylindrical conductor 9. This was installed in order to maintain the insulation of the gear 19d section. An optical magnetic field sensor 11 is arranged in a hollow portion within the ring portion 19 so as to have maximum sensitivity to the magnetic field in the axial direction of the cylindrical conductor 9. The optical magnetic field sensor 11 is a unidirectional sensor that measures the magnetic field in the axial direction, and is mainly composed of a Faraday element such as ZnSe, as well as a polarizer, an analyzer, etc., and its shape also follows the axial direction of the cylindrical conductor 9. It has a straight rod-shaped body. This optical magnetic field sensor 11 is fixed to the end of a cylindrical conductor 9 connected to one ring part via a support base 12 so as to be located on the central axis of the ring part 19.

On the other hand, a detection device @13 is disposed outside the tank 8 and is housed in a gas-insulated switchgear control panel and is composed of an optical transmitter 13a, an optical receiver 13b, and a computing unit 13C. Device 13 and the optical magnetic field sensor 1 in the tank B
1 are optically connected by an optical fiber cable 15. In this case, the optical fiber cable 15 penetrates the tank 8 at the sealed terminal 16 in a gas-tight manner, and has an insertion hole 17 opened in the wall of the cylindrical conductor 9 and an insertion hole provided at the end of the cylindrical conductor 9. It is connected to the optical magnetic field sensor 11 through 18.

As shown in FIG. 1(B), the location of the magneto-optical field sensor 11, that is, the position of the ring portion "19, is set in the UV phase (or VW phase) in the axial direction of the conductor for each phase conductor. They are staggered by an interval equal to 1/gate times the phase-to-phase distance.

The operation of the photometric flow device configured as described above is as follows. Light guided from the optical transmitter 13a of the detection device 13 into the tank 8 via the optical fiber cable 15 is converted into linear light by photons entering the optical magnetic field sensor 11, and is incident on the Faraday element. Then, an axial magnetic field is generated in the ring part 19 by energization, and after the excitation plane of the light incident on the Faraday element rotates by an angle proportional to the magnitude of the magnetic field applied to the Faraday element, it is transmitted through the analyzer and polarized. The light whose intensity depends on the rotation of the wavefront is again input to the optical receiver 13b through the optical fiber cable 15, and is extracted as an electrical signal from the calculator 13c. In this case, the current flows in the axial direction in the cylindrical conductor 9, and a magnetic field with a component perpendicular to the axial direction is generated accordingly, but since the current flows in the ring part 19 while rotating, this current causes the ring to The magnetic field generated in the hollow part is the cylindrical conductor 9
The conductor is substantially parallel and coaxial with the axial direction of the conductor, and is perpendicular to the magnetic field caused by the current flowing through the cylindrical conductor of the other phase, so it is not affected by these magnetic fields. However, since the magnetic field generated by the current flowing through the ring portion 19 disposed in the other phase is considered to include an axial component even in the ring hollow portion of the own phase, this influence poses a problem.

This will now be explained with reference to FIG.

FIGS. 4(A) and 4(B) are diagrams for explaining the characteristics of the magnetic field due to the current flowing through the ring-shaped conductor. If the current flowing through the other-phase ring-shaped conductor 20 is approximated by a line current, then the other-phase ring-shaped conductor 20 The magnitude of the magnetic field H at a point Q away from the conductor 20
r and HO are given by the following equation.

Here, I is the magnitude of the current flowing through the other-phase ring-shaped conductor 2o, a is the radius of the other-phase ring-shaped conductor 20, r is the distance from the center P of the other-phase ring-shaped conductor 20 to point Q, and θ is the point P The straight line connecting point Q and Q is the angle formed with the central axis of the ring-shaped conductor 20.

In addition, the magnetic field generated by the center P of the ring-shaped conductor 20 has an axial component, and its magnitude Ha is calculated from the following equation. The axial component H1 and the component H2 in the direction perpendicular to the axial direction of the magnetic field generated in the central part of the ring-shaped conductor 21, that is, in the optical magnetic field sensor installation part, are expressed as
Expressed as a ratio to , the following equation is obtained.

(x”+12.>a2) However, 1 is the interphase distance, and X is the axial deviation of the ring-shaped conductor arrangement portion.

Figure 4 (B) shows the magnetic field H for ×/1 based on equation (3).
The characteristics of r/Hb and H2/Ha are obtained and illustrated. The optical magnetic field sensor 11 located at the center of the ring-shaped conductor 19a is arranged so as to have maximum sensitivity to the axial magnetic field, so here, the axial magnetic field component H1/H
Focusing only on +, Hl/HO becomes maximum when x/Jl=o, that is, when two ring-shaped conductors 20 and 21 are arranged side by side, and as x/Jl increases, H1/H
1+ gradually decreases, and at the point where Tx /Jl = 1 / (V, Ht /Ha = O, and as x / J becomes larger, the direction of the magnetic field is reversed and Hl /HO increases slightly and then decreases. It becomes O at the beginning x/Jl-+ω.Therefore, by shifting the position of the ring part 19 including the optical magnetic field sensor 11 in the axial direction of the conductor by an interval equal to 1/r'i times the interphase distance, the adjacent It becomes possible to accurately measure the current of the own phase without being affected by the magnetic field generated by the current flowing through the ring-shaped conductor of the phase.

In this embodiment, the cylindrical conductor 9 of each phase of U, V, and W has isosceles 3
Since they are arranged in a rectangular shape, it is not possible to satisfy the condition that the positions of the ring portions 19 are shifted by an interval of 1/n- times the interphase distance for all U, V, and W phases. .

However, for example, as shown in FIG. 5 (A>, (B)),
Considering the case where the position of the ring part 19 of the U and W phases with respect to one ring part of the phase is shifted in the conductor axis direction by an interval of 1/(j times the interphase distance of the UV phase (= VW phase), the UV The influence of the magnetic field due to the current in the other-phase ring portion 19 between the phases and between the VW phases is completely eliminated.

On the other hand, for the UW phase, the ring part 19 of the U phase and W phase
The deviation in the conductor axis direction corresponds to the interphase distance of the UW phase, and the magnitude of the magnetic field due to the current in one of the other phase ring parts at this time is the fourth
In Figure (B), this is the value when x/f=1.

Here, when the optical current transformer of this embodiment is applied to a 275kV three-phase collective bus, the magnitude of the deviation of the ring portion 19 disposed in the U and V phase foils or the V and W phases is 2.
In addition, the current measurement error caused by the influence of the magnetic field due to the current in the ring section of the other phase between the UW phases is 0 even when a fault current, that is, a large current about 25 times the normal flow, flows in the other phase. .3%, and is hardly affected by the magnetic field of the adjacent phase.

Furthermore, if the ring-shaped conductor 19a is made of a highly conductive material such as copper, the ring-shaped conductor 19a is
An induced current flows through the ring-shaped conductor 19a, and the magnetic field created by this induced current cancels out most of the magnetic field of the adjacent phase, so the ring-shaped conductor 19a acts as a kind of magnetic shield, and the effect of this embodiment is even more remarkable. Become.

Further, the ring-shaped conductor 19a in this embodiment can be easily manufactured by cutting from a flat plate or round bar-shaped material as shown in FIGS. Furthermore, it is significantly smaller and lighter than the coiled conductor used in the conventional optical current transformer explained as an example. It is possible to reduce the outer diameter of the part by about 70%, the length by about 35%, and the weight by about 35%.

By making the cross-sectional shape of the ring-shaped conductor 19a rectangular, the direction of the magnetic field at the mounting position of the optical magnetic field sensor inside the hollow part is made linear, and by making the inner diameter of the ring-shaped conductor 19a smaller, the magnetic field is strengthened. Almost the same current measurement sensitivity as with a coiled conductor is obtained.

Next, FIG. 6(A) shows another arrangement example of the ring portion.

(B), and FIGS. 7(A) and (B).

In the arrangement example shown in Fig. 6 (A) and (B), the position of the ring part of the U and W phases with respect to the ring part of the ■ phase is 1/(7 times) the interphase distance of the IIV phase (= VW phase). Although they are arranged shifted by the distance in the conductor axial direction, the deviation in the conductor axial direction of the arrangement positions of the ring parts of the ■ phase and W phase is 0. Therefore, the difference in the conductor axial direction in the position of the Although the lengthwise dimension of the optical current transformer can be further reduced compared to the arrangement example, the influence of the magnetic field due to the other-phase ring portion between the UW phases increases.Furthermore, FIG. 7(A).

In the arrangement example shown in (B), the ring portions 19 of each phase are arranged side by side without shifting in the conductor axis direction, so the lengthwise dimension of the optical current transformer is the smallest. The influence of the magnetic field is the largest compared to other placement methods. However, when the ring-shaped conductors 19a are arranged side by side, the axial component of the magnetic field created by the current of the ring-shaped conductor 19a of the adjacent phase in the hollow part of the ring-shaped conductor 19a of the own phase is shown in FIG. 4(B). As shown in FIG.
Since the diameter of a can be made sufficiently small compared to the interphase distance, the diameter of
Even if the method of arranging one ring part shown in ) is applied, a remarkable effect of avoiding magnetic fields due to adjacent phases can be expected. Actually, when we apply these arrangement methods to a 275kV three-phase collective bus and calculate the current measurement error when a fault current flows to the adjacent phase, we get the following:
The error is approximately 2% in the case of the arrangement method shown in Figures 6 (A) and (B), and approximately 5% in the case of the arrangement method shown in Figure 7 (A>, (B)), which is within a sufficient error range for practical purposes. .

[Effects of the Invention] As described above, according to the present invention, a ring part made of a ring-shaped conductor is formed in a part of the cylindrical conductor through which the current to be measured flows, and the axial direction of the cylindrical conductor generated in the hollow part of the ring part is The simple configuration of detecting the magnetic field with a unidirectional optical magnetic field sensor eliminates the influence of the magnetic field of the adjacent phase and enables highly accurate measurement, while still using a gas-insulated current transformer core. It is possible to provide an optical current transformer that is significantly smaller and lighter than current transformers.

[Brief explanation of drawings]

FIGS. 1(A) and 1(B) are a front sectional view and a side sectional view showing only the essential parts of an embodiment of an optical current transformer according to the present invention, and FIG.
), (B) and Figure 3 (A). (B) is a front view, a side view, a front view, a side view, and Fig. 4 (A>, (B) respectively showing the structure of the ring part of the same example.
are explanatory diagrams showing the characteristics of the magnetic field due to the current flowing through the ring-shaped conductor of the same example, and FIGS. 5(A), (B) to 7
Figures (A) and (B) are a front sectional view, a side sectional view to a front sectional view, and a side sectional view showing different arrangement examples of the ring portion of the same embodiment, respectively. Front view and side sectional view showing a gas insulated current transformer using a conventional current transformer core, FIG. 9(A)
, (B) are a front sectional view and a side sectional view showing main parts of an example of a conventional optical current transformer, and FIG. 10 is a perspective view showing the state of a magnetic field near a coil portion. 1.1a, 1b... Tank, 2u ~ 2W-... Conductor, 3... Insulating spacer, 4... Current transformer core, 5...
・Support plate, 6... Insulation shield, 7... Sealed terminal,
8...Tank, 90~9W...Cylindrical conductor, 10...
- Coil part, 11... Optical magnetic field sensor, 12... Support stand, 13... Detection device, 13a... Optical transmitter, 13
b... Optical receiver, 13C... Arithmetic unit, 14... Volt, 15... Optical fiber cable, 16... Sealed terminal, 17.18... Insertion hole, 19... Ring Part, 19a... Ring-shaped conductor, 19b. 19C...Insulating plate, 19d...Gap, 20...
・Other-phase ring-shaped conductor, 21... Self-phase ring-shaped conductor. Applicant's representative Patent attorney Takehiko Suzue (A) Figure 1 Figure 2 Figure 3 (A) (B) Figure 4 Figure 5 Figure 6 Figure 7 (A) (B) Figure 8 (A) Figure 9

Claims (5)

[Claims] (1) In electrical equipment in which a cylindrical conductor is placed in a tank filled with an insulating gas such as SF_6 gas, the magnetic field generated by the current to be measured is detected by an optical magnetic field sensor, and the magnitude of the current is converted into an optical signal. In an optical current transformer that converts and measures current, a ring part made of a ring-shaped conductor is formed in a part of the cylindrical conductor through which the current to be measured flows, and a magnetic field in the axial direction of the cylindrical conductor is applied to a hollow part in the ring part. An optical current transformer characterized in that a unidirectional optical magnetic field sensor is disposed at the center of a hollow portion in the ring portion to detect the magnetic field in the axial direction. (2) The optical current transformer according to claim (1), characterized in that the cross-sectional shape of the ring-shaped conductor is rectangular, and the inner and outer diameters are made as small as possible within a range that can maintain current carrying capacity. . (3) The optical current transformer according to claim (1) or (2), wherein the ring-shaped conductor is made of a highly conductive member such as copper. (4) The cylindrical conductor has a multi-phase configuration, and the ring parts including the optical magnetic field sensors provided corresponding to each cylindrical conductor are arranged side by side at the same position in the axial direction of the cylindrical conductor. Claims (1) or (2) characterized in
Optical current transformer described in ). (5) The cylindrical conductors have a multiphase configuration, and the ring portion including the optical magnetic field sensor provided for at least one set of adjacent cylindrical conductors is positioned at an interval of 1/√2 times the interphase distance. The optical current transformer according to claim 1 or 2, characterized in that the cylindrical conductor is displaced in the axial direction of the cylindrical conductor.