JPH03285180A - Light ct for complex conductors - Google Patents

Abstract

PURPOSE:To make an apparatus small in size and light in weight and to enable detection of a current flowing through all conductors without cutting the conductors, by providing a case of an opening-closing type so that it surrounds each of the conductors in a plurality and by fitting a series of toroidal coils inside each case. CONSTITUTION:A case 2 is fitted so that it surrounds each of a plurality of conductors 1 and the case 2 is opened and closed around a hinge part 3. Inside the case 2 a series of toroidal coils 4 are provided and they are rewound in each half part of the case 2 so that both forward and backward lines thereof pass the hinge part 3. The coils 4 of each conductor 1 are connected in series. The case 4 is provided with a conductor clamp 5 on one side thereof and thereby the conductor 1 is positioned correctly in the center of the coils 4. A sensor element 7 is connected with each case 2 by a pipe 8, a solenoid 9 on the secondary side of the coils 4 is provided inside the element, and a Faraday element 10 detecting a magnetic field being proportional to a whole current is fitted in the center of the element. A large current flowing through each conductor 1 is synthesized by the coils 4 and then detected as a light signal by the element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical CT for double conductors that can accurately detect large currents flowing in double conductor buses such as substations and power transmission lines.

(Conventional technology) Generally, as the transmission current increases, busbars used in substations and power transmission lines use more double conductors than single conductors, and 2 to 8 conductors are used. There are cases.

Conventional methods for detecting large currents ranging from several hundred amperes to several +KAO flowing through such multi-conductor busbars include ■? Two methods are known: one in which the number of I conductors is reduced to one, the I conductor is passed through a CT having a large winding core, and the total current is measured; and (2) the current in one conductor of a multiple conductor is measured by a similar CT.

However, all of these methods have the problem that in order to use a large CT, a large insulator tube must be installed below the CT to support it, and it can only be installed in locations where sufficient land can be secured. Ta. In addition, method (2) requires that the existing conductor be cut once and then converted into a negative conductor before the CT is inserted, resulting in a long construction period and an economical problem. Furthermore, method (2) has problems such as large measurement errors and failure to detect even if an accident occurs on another conductor to which the CT is not attached.

(Problem to be solved by the invention a) The present invention solves the above-mentioned conventional problems, and can be installed even in narrow spaces, and can be easily installed without cutting existing conductors. Moreover, it was completed in order to provide an optical CT for double conductors that can accurately detect the current flowing through all the conductors.

(Means for Solving the Problem) A first invention made to solve the above problem is to provide an openable case equipped with a conductor clamp around each of a plurality of conductors, and to A series of unwound toroidal coils are attached so as to pass through the hinge portion on both the outward and return trips, and a Faraday element that detects a magnetic field proportional to the total current is attached to the solenoid on the secondary side. It is.

A second invention made to solve the same problem is to provide a retractable case equipped with a conductor clamp around each of the plurality of conductors, and to install the hinge portion inside each case for both the outward and return paths. It is characterized by a series of toroidal coils that are unwound so as to pass through the coil, and a burden resistor and a Pockels element that detects the voltage generated at both ends of the coil are attached to the secondary side of the coil.

(Examples) These inventions will be described in detail below using illustrated examples.

Figures 1 and 2 show two optical CT for double conductor according to the first invention.
This shows an example in which it is attached to a conductor bus bar, and (1) is 2
The book conductor (2) is a retractable case attached around each conductor (1). This case (2) has an airtight structure made of metal such as aluminum, and has a structure that can be opened and closed around a hinge part (3) and can be closed around the conductor (1). Inside the case (2) there is a series of toroidal coils (4) that reach the tip of the case (2).

This toroidal coil (4) is unwound in each half of the case (2) so as to pass through the hinge part (3) on both the outward and return journeys, and the toroidal coil (4) is wound around the hinge part (3) in the case (2). ) can be opened and closed freely, and the case (
2) is constructed so that when it is closed around the conductor (1), it becomes a toroidal shape that surrounds almost the entire circumference of the conductor (1). As shown in the circuit diagram of FIG. 3, the toroidal coils (4) of each conductor (1) are coupled in series.

The case (2) is also provided with a conductor clamp (5) made of a material with poor thermal conductivity on one side. This conductor clamp (5) clamps the conductor (1) when the case (2) is closed, thereby positioning the conductor (1) accurately at the center of the toroidal coil (4) and preventing fluctuations in the output. It is for. Furthermore, each case (2) is provided with a heat dissipation fin (6) on the outside of the conductor clamp (5). This allows the heat due to the rise in temperature of the conductor (1) to escape and prevents the sensor section (to be described below) from becoming high temperature.

As shown in the figure, the sensor part (7) is airtightly connected to each case (2) by a pipe (8), and a solenoid (9) on the secondary side of the toroidal coil (4) is provided inside the sensor part (7). . A Faraday element 00) is attached to the center of this solenoid (9) for detecting a magnetic field proportional to the total current and converting it into an optical signal. Note that the entire sensor section (7) is covered with a shield case to improve detection accuracy.

The above toroidal coil (4) has an air core, a cross-sectional area of 10 to 20 cd, and a number of turns of 1500 to 3000 ter.
, the solenoid (9) has an air core and a diameter of 20 to 50 nm.
+o+, the appropriate number of turns is 4°OO to 8000 turns. This value is determined to satisfy the condition required for the Faraday element 00) that a magnetic field of 750 oerste.7 de or more can be obtained at 50 KA. That is, the fourth
When considering the graph shown in the figure, where the vertical axis is the required number of turns of the solenoid coil and the horizontal axis is the required number of turns of the toroidal coil, the current limit that can be passed through the solenoid coil is 5
If A, the area is required to be above the lower straight line. Further, if the cross-sectional area is 20 d or less from the maximum limit dimension of the toroidal coil (4), it is required that the area is below the upper straight line. Furthermore, if the cross-sectional area of the toroidal coil (4) is 20c+11 or less, 3
The limit is 000 turns, and the area is required to be on the left side of the right vertical line. By combining these, a preferable region with hunting can be determined, and the above-mentioned value can be obtained.

The optical CT for double conductor of the first invention configured in this way is as follows:
A large current flowing through multiple conductors (1) is synthesized by a toroidal coil (4) and then detected as an optical signal by a Faraday element 0ω of a solenoid (9) on the secondary side. With the advantages of street.

First, since the currents of each conductor (1) can be combined and detected, high measurement accuracy can be ensured.

Second, by closing the case (2) around the conductor (1), installation is possible without cutting the existing conductor (1).

Thirdly, since the conductor clamp (5) is provided on the case (2), the conductor (1) can always be correctly positioned at the center of the toroidal coil (4), and measurement errors can be reduced.

Fourth, it can be made smaller and lighter than conventional CTs with large wire-wound cores, and there is no need to put extra load on overhead wires, making it easy to install in narrow spaces or with existing equipment. It can be installed on.

Fifth, since the current is converted into an optical signal and extracted by the Faraday element 0ω, the signal can be freely routed from the sensor on the bus bar using the optical fiber and extracted, and the installation position is not limited.

FIG. 5 and subsequent figures show an embodiment of the second invention, which differs only in the sensor section (7) as shown in the circuit diagram of FIG. 6. That is, in the second invention, the burden resistance θD is attached to the secondary side of the toroidal coil (4), and
Pockels element α for detecting the voltage generated across it
2 is installed.

In addition, in this embodiment, a surge absorbing element OJ is connected in parallel with the burden resistance 00 to prevent damage to the Pockels element (12+).The above-mentioned Figures 5 and 6 show the one for two conductors. However, FIG. 7 shows one for three conductors, and FIG. 8 shows one for four conductors.

The size of the burden resistance (11) in the second invention is IKΩ
It is preferable to set it as above. This is because the generated voltage at the rated current of 6 KA is 100 V or less and at low current (0.2 K), which is required for the burden resistance (II) due to the characteristics of the Pockels element.
This is to satisfy the conditions of A) that the generated voltage is IV or more and the generated voltage at the time of short circuit current (50 KA) is 500 V or less. The burden resistance value that satisfies each of these conditions is determined from the graph shown in FIG. 9, in which the vertical axis is the output voltage and the horizontal axis is the conduction current.
It can be seen that it is preferable to be within the range of KΩ.

The optical CT for a double conductor of the second invention configured in this manner also includes:
The large current flowing through the plurality of conductors (1) is combined by the toroidal coil (4), and then the Pockels element 021
can be detected as an optical signal by
This invention has the same advantages as described for the first invention, except that the configuration of the detection section is different.

In the above embodiments of the first invention and the second invention, both the toroidal coil (4) and the solenoid (9) are air-core, but one or both of them may be provided with an iron core. can.

(Effect of the invention) As explained above, the optical CT for double conductor of these inventions
This has the advantage that it can be installed even in narrow spaces, can be easily installed without cutting existing conductors, and can accurately detect the current flowing through all conductors.

Therefore, the present invention can greatly contribute to the development of industry as a solution to the conventional problems.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an embodiment of the first invention, Fig. 2 is a front view thereof, Fig. 3 is a circuit diagram thereof, and Fig. 4 shows the relationship between the number of turns of the toroidal coil and the number of turns of the solenoid coil. Graph, Fig. 5 is a plan view showing the embodiment of the second invention, Fig. 6 is a plan view showing the embodiment of the second invention.
The figure is a circuit diagram, FIG. 7 is a front view showing an embodiment in which the second invention is applied to a three-conductor bus, FIG. 8 is a front view showing an embodiment in which the second invention is applied to a four-conductor bus, and FIG. It is a graph showing the relationship between the current flowing through the burden resistor and the output voltage. (1): Conductor, (2) Two cases, (3): Hinge, (
4): I-loidal coil, (5): Conductor clamp, (9): Solenoid, 0ω: Faraday element, 00:
Burden resistance, 021: Pockels element.

Claims (1)

[Claims] 1. Conductor clamps (5
), each case (2) is equipped with a retractable case (2).
) is equipped with a series of unwound toroidal coils (4) that pass through the hinge part (3) on both the forward and return trips, and a magnetic field proportional to the total current is applied to the solenoid (9) on the secondary side. Faraday element to detect (10
) is attached to an optical CT for double conductors. 2. Place conductor clamps (5) around each of the multiple conductors (1).
), each case (2) is equipped with a retractable case (2).
) is equipped with a series of toroidal coils (4) which are unwound so as to pass through the hinge part (3) on both the forward and return trips, and a load resistor (11) on the secondary side and the voltage generated at both ends thereof. Pockels element to detect (12)
An optical CT for a double conductor, characterized in that it is equipped with.