JPH0524464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a ground fault current detection device for high voltage equipment.

(Technical background of the invention and its problems) When a ground fault occurs in high-voltage equipment, such as a high-voltage transformer, an ultra-high-voltage gas insulated switchgear (GIS), a high-voltage cable line, or its terminal, the entire equipment or Some circuits are disconnected by circuit breakers.

The ground fault point is then searched for and repaired, and the waveform, direction, etc. of this ground fault current provide important clues to the state of the fault. A method as shown in FIG. 1 can be considered for detecting this ground fault current.

That is, this is a method in which a current transformer 2 is inserted into a grounding wire 1 that grounds equipment, and the current induced in the coil 3 is observed.

However, in general, in high-voltage equipment, a circulating current due to induction flows through the ground wire during normal operation, and furthermore, there is a large difference in short-circuit current depending on the impedance of the circuit. Since the short circuit current is a large current,
There may also be cases where the magnetic core 4 of the current transformer becomes saturated and the current waveform cannot be faithfully extracted. For this reason, it was necessary to design and manufacture a current transformer for each device. I can't stand this hassle.

Furthermore, in a system that constantly monitors ground fault current, it is necessary to guide the signal from this detector to a monitoring station. For this purpose, it is preferable to transmit signals using a non-metallic (containing no metal parts) optical fiber with good electrical insulation properties.

However, incorporating a complex circuit for light conversion into the detector has the drawback of lacking reliability.

(Object of the Invention) The present invention has been made to solve the above problems, and its purpose is to provide a ground fault current detection device that can be adjusted to obtain characteristics suitable for each device. .

(Summary of the Invention) That is, the present invention arranges a coil near a grounding wire, and makes it possible to change the magnetic coupling between the magnetic core passing through this coil and the grounding wire, thereby adjusting the magnetic saturation characteristics according to the device. The present invention relates to a ground fault current detection device that can be obtained.

(Structure of the Invention) The present invention will be described below based on embodiments of the drawings. 2 and 3 are diagrams of the principle of the present invention.

In the figure, grounding wire 1 of high voltage equipment (not shown)
A coil 3 for detecting ground fault current is arranged near. If a ground fault current flows through the ground wire 1, a magnetic field centered around the ground wire 1 is formed. A magnetic core 5 is inserted into the coil 3 and forms a magnetic path for the magnetic flux generated by this magnetic field. When the magnetic core 5 is rotated about the axis 6, the magnetic coupling between the ground wire 1 and the magnetic core 5 changes. Along with this, the induced current induced in the coil 3 changes. This induced current value can be selected by appropriately selecting the rotation angle of the magnetic core 5. The present invention takes advantage of this property.

FIG. 4 is a wiring diagram of main parts of the ground fault current detection device of the present invention.

The coil 3 wound around the magnetic core 5 has two light emitting diodes 7 and 8 connected to each other with opposite polarity.
are connected in parallel, and a semi-fixed resistor 9 is inserted in series in this circuit. One ends of optical fibers 10 and 11 are arranged opposite to the two light emitting diodes 7 and 8, and the other ends are connected to a receiver 12. The receiver 12 includes an O/E converter 13 that converts optical signals transmitted from the optical fibers 10 and 11 into electrical signals, and a synthesis circuit 14 that synthesizes these signals.
It has a determination circuit 15 that determines whether or not a current corresponding to a ground fault has flowed through the coil 3.

FIG. 5 is a partially cutaway perspective view of a ground fault current detection device according to an embodiment of the present invention. As shown in FIG. 5, the case 21 that houses the magnetic core 5 around which the coil 3 is wound is composed of a cylindrical case body 22 and a support body 23 that rotatably supports the case body 22. , the magnetic core 5 is connected to the case body 2
It is mounted and supported within 2.

Further, four mounting pieces 24, 24, . . . are provided on the outer periphery of the support body 23.
4, 24, . . . are fixed to a fixing member 28 having an insertion groove 27 for the grounding wire 1 with bolts 29, 29, . Note that the rotation angle of the magnetic core 5 can be determined from the scale 30 provided on the surface of the case body 22 and the arrow 31 provided on the surface of the support body 23.

The apparatus of the present invention having the above configuration operates as follows. When a ground fault current flows through the ground wire, an induced current flows through the coil 3. The ground fault current at the time of an accident flows from about 5KA to 50KA. The orientation of the magnetic core 5 is adjusted so that the induced voltage in the coil 3 at this time is about 100V. Since light emitting diodes emit light at tens of milliamps, the resistance value of the semi-fixed resistor is adjusted accordingly.

When a ground fault occurs, the circuit breaker of the protection device is activated in a very short time, so the time during which the waveform of the ground fault current can be observed is very short. Moreover, the direction of the current is not constant. During this time, in order to faithfully transmit the ground fault current waveform to the monitoring station, one light-emitting diode captures the positive polarity of the AC waveform, and the other diode captures the negative polarity. This signal is converted into an electric signal by a pair of O/E converters 13, and then synthesized by a synthesis circuit 14 to reproduce the original ground fault waveform. The determination circuit 15 records this ground fault waveform for analysis, and also rectifies and averages it using, for example, a double-wave rectifier circuit. For example, when a voltage higher than the output corresponding to the output at the time of ground fault current detection of 5KA is detected, an alarm is sounded.

In the ground fault current detection device shown in FIG. 5, when the case body 22 is rotated and the coil 3 is set in the position shown in FIG. Setting the position as shown in FIG. 3 will minimize the magnetic flux passing through the coil 3. In this way, in the ground fault current detection device of the embodiment, by rotating the case body 22, the magnetic coupling between the magnetic core 5 and the ground wire 1 can be changed, and the ground fault current flowing through the ground wire 1 can be predicted in advance. However, due to this ground fault current, the magnetic core 5
The angle of the magnetic core 5 is set at such an angle that the magnetic core 5 is not saturated.

The device of the invention described above is not limited to the embodiments thereof.

The magnetic core can take various shapes such as U-shape, U-shape, L-shape, etc.

The means for changing the relative angle between the magnetic core and the ground wire may be such that the magnetic core is provided with a shaft and rotatably supported by a bearing. Various changes can be made to the relative angle display means depending on the support structure. Furthermore, the magnetic coupling may be changed by changing the distance between the magnetic core and the ground wire, or by inserting a magnetic shield or closed body between the two.

(Effects of the Invention) As explained above, in the ground fault current detection device of the present invention, magnetic coupling can be changed by rotating the magnetic core, so ground fault current detection settings can be made according to the device. , ground fault current can be detected faithfully.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a method for detecting a ground fault current in a grounding wire, FIGS. 2 and 3 are perspective views explaining the operating principle of the device of the present invention, and FIG. 4 is a perspective view of the device of the present invention. FIG. 5 is a partially cutaway perspective view of a ground fault current detection device according to an embodiment of the present invention. 1... Ground wire, 3... Coil, 5... Magnetic core, 7, 8... Light emitting diode, 10, 11...
Optical fiber, 12...Receiver.

Claims (1)

[Claims] 1 Place a coil near the grounding wire of high voltage equipment,
A ground fault current detection device characterized in that magnetic coupling between a magnetic core passing through the coil and the ground wire is made variable by rotation of the magnetic core.