JPH0652273B2 - Circular integration type optical CT - Google Patents

Description

TECHNICAL FIELD The present invention relates to a circular integration type optical CT, and more particularly, to an improved measurement accuracy thereof.

<< Prior Art >> In optical CT, when a sensor made of a substance exhibiting the Faraday effect is arranged in the vicinity of a conductor in which an electric current flows, a magnetic field generated around the electric current causes the polarization plane of light passing through the sensor to be changed. It is a current measuring device for electric power that measures the magnitude of current by utilizing the phenomenon of rotation.

In this type of current measuring device, the principle of measurement is to convert the current to be measured via the magnetic field generated around the outer circumference of the current to be measured, so if one point type sensor measures current, for example, the conductor and sensor Not only does the accuracy of the relative positional relationship with and affect the measurement accuracy, but the magnetic field due to the current of the other phase located near the conductor to be measured is a major cause of measurement error.

Therefore, as a means of compensating for such errors and improving the measurement accuracy, the optical path in the sensor is configured so as to go around the conductor, and the polarization plane approximately proportional to the circular integration of the magnetic field around the current to be measured. There is provided a circular integration type optical CT capable of obtaining the rotation angle (Faraday rotation angle).

FIG. 3 shows a typical structure example of the circular integration type optical CT.

The circular integration type light CT shown in the figure is composed of four Faraday rods F1 to F4 and a prism P.

The four Faraday rods F1 to F4 are made of, for example, a member having a Faraday effect such as lead glass, and the prism P has a right-angled prism so as to deflect light by 90 degrees.
Individually combined.

The four Faraday rods F1 to F4 are arranged on each side that is a square when seen in a plan view, and the other pair of Faraday rods F2 and F4 are opposed to the pair of Faraday rods F1 and F3 that face each other. It is placed above by the thickness.

The prisms P are respectively provided at the three corners of the square.
The incident light S _i introduced from the incident surface 1 at one end of the Faraday rod F1 is deflected upward by the prism P at the other end of the Faraday rod F1 and enters one end of the Faraday rod F2. Side, it is deflected downward again and is incident on the Frade rod F3, and finally the emitted light S _O is taken out from the emission surface 2 at one end of the Frade rod F4, and the outer circumference of the conductor 3 is inserted almost at the center of the square. A circular optical path S that is closed in a plane is formed.

In the circular integration type light CT configured as described above, the incident light S _i and the outgoing light S _O that has rotated the circular optical path S are located in directions orthogonal to each other, and these are the incident light of the circular optical path S. The device is designed so as to intersect three-dimensionally at the emission part, but such a structure had the technical problems described below.

<< Problems to be Solved by the Invention >> FIG. 4 is an enlarged plan view of the input and output portions of the conventional circular integration type optical CT shown in FIG. 3 as seen from the direction of the current I to be measured.

As is clear from FIG. 4, in the conventional circular integration type light CT, the intersection point O on the plane of the circular optical path S is located inside the entrance surface 1 and the exit surface 2.

For this reason, there are portions A and A that are out of the closed loop of the circular integration, and since these portions A have the Faraday effect, the influence of the magnetic field of the other-phase current particularly on this portion A causes measurement error. There was a problem that became large.

The present invention has been made in view of the above conventional problems, and an object thereof is a circuit integration type optical CT capable of improving the measurement accuracy by eliminating the influence of the magnetic field of another phase. To provide.

<< Means for Solving the Problem >> In order to achieve the above object, the present invention has a material having a Faraday effect on the outer circumference of a conductor through which a current to be measured flows, and three-dimensionally intersects at the exit portion, and , Forming a circularly closed optical path, introducing the incident light from one end of this circular optical path, and passing through the circular optical path, the Faraday rotation of the outgoing light extracted from the other end in the direction orthogonal to the incident light. In the optical CT for measuring the magnitude of the electric current from an angle, the incident surface and the outgoing surface are located at an intersection where the circular optical paths intersect on a plane.

<< Operation >> According to the circular integration type optical CT having the above configuration, the incident surface and the outgoing surface of the circular optical path formed on the outer circumference of the conductor in which the current to be measured flows are three-dimensionally intersected at the entrance and exit parts. Moreover, since it is located at the intersection of the plane-closed circular optical path on the plane, there is no part out of the circular integral closed circuit, and the influence of the magnetic field of the other-phase current is eliminated.

<Example> Hereinafter, a preferred example of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 show an embodiment of the circular integration type optical CT according to the present invention.

In the optical CT shown in the figure, the same reference numerals are used for the same or corresponding portions as those of the conventional circular integration type optical CT described above.

FIGS. 1 and 2 are enlarged views of the entrance and exit portions of the circulating optical path S of the optical CT according to the present invention, and the overall structure of the optical CT is as shown in FIG. It has books Faraday rods F1 to F4 and three sets of prisms P.

The Faraday rods F1 to F4 are arranged on the respective sides that are square in plan view, and the pair of Faraday rods F1 and F3 located on the opposite sides are the pair of F2 located on the other opposing sides. The prism P is arranged below F4 by the thickness thereof, and the prisms P are arranged at the three corners of the square, respectively, and the incident light S _i introduced from the incident surface 1 at one end of the Faraday rod F1 is The other end of the Faraday rod F1 is deflected upward by the prism P to enter one end of the Faraday rod 2, and the other end is again deflected downward to enter the Frade rod F3, and finally emitted light S _O Is taken out from the exit surface 2 at one end of the Frade rod F4, and the outer circumference of the conductor 3 is inserted into the approximate center of the square. There has been formed.

The basic configuration of the above-described circulation integration type optical CT is the same as that of the conventional device of this type.

However, in the optical CT having such a structure, a part of the Faraday rods F1 and F4 exists in a portion deviated from the orbiting optical path S, and this portion is affected by the magnetic field of the other phase to improve the measurement accuracy of the optical CT. Had lowered.

Therefore, in the present invention, the entrance surface 10 and the exit surface 12 of the orbiting optical path S are respectively positioned on the intersection C on the plane of the orbiting optical path S that three-dimensionally intersects at the entrance and exit portions.

That is, when the entrance and exit portions of the orbiting optical path S are viewed from the direction in which the current I to be measured flows, the intersection O of the orbiting optical path S that is three-dimensionally intersecting appears on the plane and is incident on this intersection O. The one end surface of the Faraday rod F1 serving as the surface 10 is located, and the one end surface of the Faraday rod F4 serving as the emitting surface 12 is located.

According to the circular integration type optical CT configured as described above, the incident surface 10 and the outgoing surface 12 of the circular optical path S formed on the outer periphery of the conductor 3 in which the current I to be measured flows are the entrance and exit portions. Since it is positioned on the intersection point O of the circular optical path S that is three-dimensionally intersected by and is planarly closed, there is no part outside the closed loop of the circular integration, and the influence of the magnetic field of the other phase current is eliminated, This greatly improves the measurement accuracy of the optical CT.

In the above-described embodiment, the Faraday rods F1 to F4 forming the orbiting optical path S and the prism P are separated, but these parts may be integrally formed. .

<< Effects of the Invention >> As described in the above embodiments, in the circular integration type optical CT according to the present invention, it is easy to change the positions of the entrance and exit surfaces of the circular optical path formed on the outer circumference of the current to be measured. The configuration eliminates the influence of the multilayer magnetic field on the optical CT, which has the particular effect of significantly improving the measurement accuracy.

[Brief description of drawings]

FIG. 1 is an enlarged plan view of an essential part showing an embodiment of a circular integration type optical CT according to the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a general perspective view of a conventional circular integration type optical CT. Fig. 4 and Fig. 3
It is a principal part enlarged plan view of the figure. 3 ... Conductor 10 ... Incident surface 12 ... Ejection surface F1-F4 ... Faraday rod I ... Current to be measured P ... Prism S ... Circular optical path _Si ... Incident light _SO ... Outgoing light

Claims (1)

[Claims] 1. A circular optical path which is three-dimensionally crossed at the entrance and exit parts of a conductor having a Faraday effect on the outer periphery of a conductor through which a current to be measured flows and which is closed in a plane,
An optical CT that measures the magnitude of the current from the Faraday rotation angle of the outgoing light that is introduced from one end of this circular optical path and that is extracted from the other end through the circular optical path in the direction orthogonal to the incident light. A circular integration type optical CT, characterized in that the entrance surface and the exit surface are located at an intersection where the circular optical paths intersect on a plane.