JPH03215760A - Earth detector - Google Patents

Abstract

PURPOSE:To preclude an earth accident by providing a track type iron core which is at a half conductor distance from respective conductors at the circumference of a three-phase conductor, providing a magneto-optical field sensor in the gap of the iron cores, and supporting the whole by an opto-insulator. CONSTITUTION:The track type iron core 2 is provided on the circumferences of the bare conductors 1, the distance from each conductor 1 is nearly a half as long as the distance between the conductors 1 at all parts, and the gap 3 is formed at a part of the iron core 2. In the gap 3, the magneto-optical field sensor 4 with Faraday effect is fitted and a magnetic field produced at the iron core 2 is converted into an optical signal. Then when the earth occurs to one of the conductors 1, a zero-phase current has a current value corresponding to the earth and a magnetic field is produced in the iron core 2, so that the sensor 4 generates an output. This output is led out to a ground side through an optical fiber 6 incorporated in the opto-insulator 5. Thus, the earth occurring to one of three-phase conductors 1 can be detected as the optical signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ground fault detection device used for detecting a bus ground fault current in a closed distribution board with a system voltage of 7.2 KV class, for example.

(Prior art) As shown in Fig. 4, the method for detecting the ground fault current of the bus is to pass the three-phase collective bus θ0 through a single ZCR (zero-phase current transformer) 02, and detect the zero-phase current. A common method is to detect However, when such a conventional ground fault detection device is used for detecting a faulty section in a switchboard, there are the following problems.

■Since it is necessary to surround the three-phase collective busbar with ZCT, it can only be attached to a cable portion covered with an insulating coating from the point of view of insulation, and the installation location is limited.

■If the insulation of the conductor in the CT section deteriorates, there is a risk of a ground fault occurring via the secondary winding.

■When applied to bare conductor parts other than cable parts, it is necessary to provide ground insulation in addition to phase-to-phase insulation, and the CT part must be enlarged.

(2) Since the ZCT requires a secondary winding, in addition to requiring induction countermeasures, countermeasures against the high voltage generated when the secondary side is opened (broken) are also required.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems, does not limit the mounting location, and can downsize the CT section, so that the CT section can be This was developed in order to provide a ground fault detection device that does not cause a ground fault even if the insulation deteriorates and does not cause problems when the secondary side opens.

(Means for Solving the Problems) The first five points made to solve the above problems are that the distance from each conductor around the three-phase conductor is approximately 1 of the distance between the conductors at a distance of 4. A T-rank type iron core with a size of /2 is provided, an optical magnetic field sensor is installed in a gas block formed in a part of this iron core, and the entire q is an opto-insulator with a built-in optical fiber heather connected to the optical magnetic field sensor. The central sign is that it was supported by

A second invention made to solve the same problem is a trunk in which windings are wound around the three-phase conductors so that the distance from each conductor is approximately 1/2 of the distance between the conductors in all parts. A type of iron core is provided, a burden resistor is provided at the open end of the circuit, and a photovoltaic sensor is provided to detect the voltage generated at both ends. It is characterized by being supported by an optical insulator.

(Example) The present invention will be explained in detail below with reference to illustrated embodiments.

FIG. 1 shows an embodiment of the first invention, in which (1) is a bare conductor, and (2) is a track-shaped iron core provided around these conductors (1). This iron core (2
) is such that the distance from each conductor (1) is approximately 1/2 of the distance between conductors (1) and (1) in all parts,
The entire structure is insulated. A gap (3) is formed in a part of this trunk-shaped core (2),
Inside this gap (3), an optical magnetic field sensor (4) having a Faraday effect such as YIG or BSO is attached to convert the magnetic field generated in the iron core (2) into an optical signal. (5)
is an opto-insulator (optical fiber-embedded insulator) that supports the entire iron core (2) and optical magnetic field sensor (4) with ground insulation. An optical fiber (6) is located in the center of the opto-insulator (5).
The upper end of this optical fiber (6) is connected to an optical magnetic field sensor (4), and the optical signal that is the output thereof can be taken out to the ground side.

A device configured in this way is used, for example, by being installed inside a closed switchboard, and while a three-phase alternating current with no ground fault component is flowing through the conductor (1), its zero-phase current is zero. Therefore, no magnetic field is generated in the iron core (2) around the three-phase conductor (1), and therefore the optical magnetic field sensor (4) does not generate an output. However, if there is a ground fault in any of the conductors (1), the zero-sequence current will have a current value corresponding to the ground fault, and the iron core (
A magnetic field is generated inside the iron core (2) and the gap (3) of the iron core (2) is generated.
) produces an output. This output will be taken out to the ground side through the optical fiber (6) built into the opto-insulator (5).

In this manner, the ground fault detection device of the present invention can detect a ground fault occurring in any of the three phase conductors (1) as an optical signal.

Figures 2 and 3 show an embodiment of the second invention, in which the distance from each conductor (1) around the three-phase conductor (1) is approximately 1 of the distance between the conductors in all parts. A track-shaped winding (7) with a diameter of /2 is provided. As shown in the circuit diagram of Figure 3, the open circuit end of this winding (7) has a burden resistance (
8) is provided, and in order to detect the voltage generated across this burden resistor (8), an optical voltage sensor ( 9) is connected. This winding (2) is supported with ground insulation by an opto-insulator (5) containing an optical fiber (6) connected to the photovoltage sensor (9) and a normal insulator θω. The ground fault detection device of the second invention configured in this manner, in which the output can be taken out to the ground side through this optical fiber (6), also has a zero state when a ground fault occurs in any of the three phase conductors (1). Since the phase current has a corresponding value, a t current is generated in the winding (2), producing a voltage across the burden resistor (8), which is converted into an optical signal by the optical voltage sensor (9). The output of this optical voltage sensor (9) is taken out to the ground side through an optical fiber (6).

(Operations and Effects) As explained above, the ground fault detection devices of the first and second inventions of the present application, when a ground fault occurs in any of the three phase conductors (1), ground the ground fault as an optical signal. Although it can be taken out to the side, it exhibits the following effects compared to the conventional one shown in FIG.

First, in the ground fault detection device of the present invention, since the track-shaped iron core (2) or the winding (7) is supported by the opto-insulator (5) for ground insulation, the conductor (1) is exposed in the bare portion. There are no restrictions on installation location. Therefore, it is effective for detecting failure points within a switchboard.

Second, in the ground fault detection device of the present invention, the conductor (1),
(1) It is only necessary to consider the interphase insulation between the conductor (1)
There is no need to consider the ground insulation between the iron core (2) and the winding (7). For this reason, the conductor (1) and the iron core (
2) The entire device can be made smaller compared to conventional ZCT, which requires a ground insulation distance between the It goes without saying that the reason why the distance between the conductor (1) and the iron core (2) etc. is set to approximately 1/2 of the distance between the conductors is to ensure interphase insulation.

Thirdly, in the ground fault detection device of the present invention, since there is air insulation between the conductor (1) and the iron core (2), etc., even if the mold of the iron core (2) etc. deteriorates, There is no risk of an accident occurring. Fourthly, the ground fault detection device of the present invention uses a photomagnetic field sensor (4) and a photovoltage sensor (9), and the output thereof is taken out to the ground side through an optical fiber (6), so it can be used in a narrow panel. Also, the optical fiber (6) can be freely routed without requiring special consideration for insulation. In addition, it is non-inductive and does not generate high voltage when the secondary side is open, so no countermeasures are required. As explained above, the ground fault detection device of the present invention greatly contributes to the development of industry by eliminating the problems of the conventional technology. It goes without saying that the ground fault detection device of the present invention can be used not only for detecting ground faults in a switchboard, but also for detecting ground faults on busbars outside.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a front view showing an embodiment of the first invention, FIG. 2 is a front view showing an embodiment of the second invention, FIG. 3 is a circuit configuration diagram thereof, and FIG. The figure is a perspective view conceptually showing a conventional example. (1): Conductor, (2) Two iron cores, (3): Gap, (4
): Optical magnetic field sensor, (5): Optical insulator, (6): Optical fiber, (7): Winding wire, (8): Burden resistance, (9): Optical voltage sensor.

Claims (1)

[Claims] 1. A track-shaped iron core (2) is provided around the three-phase conductor (1) so that the distance from each conductor (1) is approximately 1/2 of the distance between the conductors in all parts. , an optical magnetic field sensor (4) is installed in a gap (3) formed in a part of this iron core (2), and an optical fiber (6) connected to the optical magnetic field sensor (4) is built into the whole. A ground fault detection device characterized in that it is supported by an opto-insulator (5). 2. A track-shaped iron core (2) in which a winding (7) is wound around a three-phase conductor (1) so that the distance from each conductor (1) is approximately 1/2 of the distance between the conductors in all parts. A burden resistor (8) is provided at the open end of the circuit, and a photovoltage sensor (9) is provided to detect the voltage generated at both ends, and the entirety of these is connected to the photovoltage sensor (9). A ground fault detection device characterized in that it is supported by an opto-insulator (5) incorporating an optical fiber (6).