JP2636417B2 - Insulation breakdown detection circuit for instrument transformer and instrument transformer provided with the detection circuit - Google Patents

Description

The present invention relates to a primary coil and a secondary coil of an instrument transformer,
Alternatively, the present invention relates to a circuit for detecting insulation breakdown between a primary coil and an iron core, and an instrument transformer provided with the circuit.

[Conventional technology]

FIG. 5 is an external perspective view showing an example of a conventional instrument transformer, and FIG. 6 is a circuit diagram of a general power receiving facility using the conventional instrument transformer.

In the drawing, 1 is a high-voltage side electric circuit composed of an insulated cable or the like and supplies power to a load, 2 is a high-voltage side zero-phase current transformer that detects a ground fault current of the high voltage side circuit and transmits its secondary output to a ground fault relay 3,
Reference numeral 4 denotes a circuit breaker for tripping the load side of the high-voltage side electric circuit 1 via an output from the ground-fault relay 3 when the ground-fault current exceeds a predetermined level via a coil 4a. Is a voltmeter that measures the voltage of Reference numeral 10 denotes a transformer for an instrument, a primary coil 11, a secondary coil 13, and a secondary terminal.
14, the iron core 15 and the mounting frame 16. The primary coil 11 is connected to the high voltage side electric circuit 1 via the primary side fuse 12, and the secondary coil 13 is connected to the low voltage electric path via the secondary terminal 14. The iron core 15 is connected to the ground via a structure (not shown) to which the mounting frame 16 is attached.

In the power receiving equipment having this configuration, the A
When a ground fault occurs at a point, a ground fault current indicated by an arrow B flows and the circuit breaker 4 operates via the ground fault relay 3 by the output of the high-voltage zero-phase current transformer 2 to load the high-voltage side circuit 1. To protect the circuit.

The above is the case of the ground fault accident caused by the insulation breakdown of the high voltage side electric circuit 1, but the insulation breakdown between the primary coil 11 and the iron core 15 or the secondary coil 13 occurs inside the instrumentation transformer 10. In the case, primary coil 11 → iron core 15 → mounting frame 16 → to the ground via the above structure, and also primary coil 11 → secondary coil
The ground fault current flows from the high-voltage side electric circuit 1 to the low-voltage path 13 to the low-voltage path, and the circuit breaker 4 is activated by the output of the high-voltage current transformer 2 via the ground fault relay 3 in the same manner as described above.

Generally, after the circuit breaker 4 is actuated due to a ground fault, an electric manager checks the high-voltage circuit 1 and the components connected thereto, identifies an abnormality, removes the cause of the accident, and then removes the high-voltage circuit. The power supply to the load No. 1 is restored. in this case,
Insulation breakdown between the primary coil 11 and the secondary coil 13 or the iron core 15 due to insulation deterioration inside the instrument transformer 10 often has no abnormal appearance, and the voltmeter 8 connected to the low-voltage piezoelectric path It is very difficult to determine the dielectric breakdown inside the instrument transformer 10.

[Problems to be solved by the invention]

As described above, the conventional power receiving equipment circuit is protected against the ground fault by the high-voltage current transformer 2, but in the case of the ground fault inside the instrument transformer 10, it is necessary to find the fault location. There is a problem that it takes a long time until the power is restored and the power supply is restored, and the damage caused by the suspension of the operation of each electric device or the like during that time is great.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an insulation breakdown detection circuit of a transformer requiring an instrument, which can easily detect that a ground fault is caused by insulation breakdown inside the instrumentation transformer, and An object of the present invention is to provide an instrument transformer provided with a dielectric breakdown detection circuit.

[Means for solving the problem]

An insulation breakdown detection circuit according to claim 1 of the present invention comprises:
A ground wire connecting the above-mentioned iron core and the earth of the instrument transformer in which the iron core is insulated from the ground, an electric path connected to this ground wire and the secondary coil are used as a primary input, and a secondary output thereof is used to detect insulation breakdown of the transformer. The transformer according to claim 2, further comprising an insulated terminal block whose outer peripheral surface is formed as a zero-phase transformer fitting surface and protrudes outward. At least a part of the ground wire from the iron core and the coil end of the secondary coil extend in the insulating terminal block and are connected to the ground terminal and the secondary terminal provided on the insulating terminal block, respectively. According to the third aspect, insulation between the iron core and the ground is ensured by fixing the iron core to the mounting frame via an insulating spacer.

[Action]

According to the present invention, when the zero-phase transformer breaks down the insulation inside the instrument transformer, a ground fault current flowing from the primary coil to the ground wire via the iron core or from the primary coil to the low piezoelectric path via the secondary coil is determined. To detect.

Further, by fitting the zero-phase transformer to the insulated terminal block provided on the instrument transformer, an instrument transformer having an insulation breakdown detection circuit is configured.

〔Example〕

FIG. 1 is a circuit diagram of a power receiving facility using the embodiment of the insulation breakdown detecting circuit according to claim 1 of the present invention, and FIG. 2 is claim 1.
FIG. 3 is a circuit diagram of a power receiving facility using another embodiment of the insulation breakdown detecting circuit described above, and FIG. 3 is an external perspective view of an instrument transformer used in the present invention.

In the figure, reference numeral 17 denotes a ground wire, which is provided to ground the iron core 15 and the mounting frame 16. Reference numeral 18 denotes an insulating plate, which is provided to prevent the electric potential of the iron core 15 and the mounting frame 16 from leaking from other than the ground wire 17. Reference numeral 5 denotes a zero-phase transformer, which uses the low-voltage path from the secondary coil 13 and the ground line 17 as primary inputs (primary side) and inputs the secondary output to the earth leakage relay 6. The earth leakage relay 6 amplifies the secondary output of the zero-phase transformer 5 so as to amplify the ground fault relay 3 and the display 7.
And the circuit breaker 4 is operated via the ground fault relay 3 and at the same time, the display 7 indicates that the earth leakage relay 6 has been operated.

In this configuration, when a ground fault occurs in the high-voltage side electric circuit 1, the ground-fault relay 3 operates by the output from the high-voltage side zero-phase current transformer 2, and the circuit breaker 4 loads the high-side electric circuit 1. Cut off. Accordingly, there is no input to the display 7 and the display 7 does not perform the display operation, so that it is possible to determine that the generated ground fault is the ground fault of the high-voltage side electric circuit 1.

When the insulation between the primary coil 11 and the iron core 15 or the secondary coil 13 is deteriorated and mixed, the ground fault current flows from the primary coil 11 through the ground wire 17 or the low piezoelectric path. Since this ground fault current becomes the primary input of the zero-phase transformer 5, the earth leakage relay 6 operates, and the display 7 performs display. From this display, it is possible to know that a ground fault has occurred inside the instrument transformer 10.

In the above embodiment, since the zero-phase current transformer 5 for detecting insulation breakdown is provided in each of the instrument transformers 10, the instrument transformer 10 in which an internal ground fault has occurred can be identified.

FIG. 2 shows another embodiment of the present invention.
The zero-phase current transformers are configured to detect ground faults of all the transformers 10 for an instrument.

With this configuration, the instrument transformer 10 in which the internal ground fault has occurred cannot be individually identified, but the cost of installing the insulation breakdown detection circuit is lower than in the embodiment of FIG. There are advantages.

FIG. 4 shows an embodiment of the invention according to claim 2 of the present invention, wherein reference numeral 20 denotes an instrument transformer. This instrument transformer 20 has an insulated terminal block 22 that protrudes outward from the coil section 21 in a horizontal direction, and the iron core 15 is fixed to the mounting frame 16 with an insulating spacer 23 interposed between the core and the mounting frame 16. Have been. The insulating terminal block 22 has an outer shape that matches the shape of the space 5A of the zero-phase transformer 5, and its outer surface is
The terminal 14 of the secondary coil 13 and the ground terminal 24 are provided on the end surface thereof. Reference numeral 25 denotes a ground wire that connects between the iron core 15 and the ground terminal 24, passes through the outside of the mounting frame 16 from the iron core 15, enters the insulated terminal block 22 from the base of the insulated terminal block 22, and extends to the ground terminal 24. I have. An earth leakage relay 6 is connected to an output terminal 5a of the zero-phase transformer 5.

When this instrument transformer 20 is used in the circuits of the power receiving equipment shown in FIGS. 1 and 2, the zero-phase transformer 5 is extrapolated and fixed to the insulated terminal block 22, and the secondary terminal 14 is fixed. Is connected to the ground terminal 17, the ground wire 17 is connected to the ground terminal 24, and the earth leakage relay 6 is connected to the output terminal 5a of the zero-phase transformer 5.

When the instrument transformer 10 shown in FIG. 3 is used, since the zero-phase transformer 5 and the instrument transformer 10 are disposed at different positions,
A low-voltage path from the secondary terminal 14 of the secondary coil 13 to the core
The grounding wire 17 is extended from the 15 through the zero-phase transformer 5 located at another position. When the instrument transformer 20 shown in FIG. 4 is used, the grounding from the coil end of the secondary coil 13 and the iron core 15 is performed. Line 25
Since the insulating terminal block 22 passing through the inside passes through the zero-phase transformer 5, the labor for wiring and the labor for arranging the zero-phase transformer are reduced.

Further, in the instrument transformer 20, since the iron core 15 and the mounting frame 16 are insulated from each other by the insulating spacers 23, as in the case of the instrument transformer 10 shown in FIG. It is not necessary to provide plate 18.

〔The invention's effect〕

As described above, according to the present invention, the ground wire connecting the iron core of the instrument transformer and the ground and the electric circuit connected to the secondary coil are used as primary inputs, and the secondary output is used as the insulation breakdown detection output of the transformer. Since the zero-phase transformer is provided, the internal ground fault of the instrument transformer can be identified and detected as the ground fault of another part. Also, since the instrument transformer is provided with an insulated terminal block protruding to the outside and capable of extrapolating and fitting the zero-phase transformer, the line constituting the primary input of the zero-phase transformer does not have to be extended from the instrument transformer. This makes it possible to easily provide a dielectric breakdown detection circuit without any trouble.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power receiving facility using an embodiment of the present invention,
FIG. 2 is a circuit diagram of a power receiving facility using another embodiment of the present invention, FIG. 3 is a perspective view of an instrument transformer used in the power receiving facility, and FIG. 4 is an instrument transformer used in the power receiving facility. FIG. 5 is a perspective view of a conventional transformer for an instrument, and FIG. 6 is a circuit diagram of a power receiving facility using the conventional transformer for an instrument. In the figure, 1 ... high-voltage path, 2 ... high-voltage side zero-phase current transformer, 5 ... zero-phase transformer, 10, 20 ... instrument transformer, 11 ...
... primary coil, 13 ... secondary coil, 14 ... secondary terminal, 15
... iron core, 16 ... mounting frame, 17, 25 ... ground wire,
22 ... Insulated terminal block, 23 ... Insulated spacer, 24 ... Ground terminal. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

(57) [Claims] A ground wire for connecting said iron core and the earth in an instrument transformer comprising an iron core insulated from the earth, a primary coil and a secondary coil electromagnetically coupled via said iron core; An insulation breakdown detection circuit for a transformer for an instrument, comprising: a zero-phase transformer having a primary path of an electric circuit connected to a secondary coil and a secondary output of which is an insulation breakdown detection output of the transformer. 2. An instrument transformer having an iron core insulated from the ground by electromagnetically coupling a primary coil and a secondary coil to each other, wherein an outer peripheral surface is formed as a transformer fitting surface and is directed toward the outside. A protruding insulating terminal block, at least a part of a ground wire from the iron core and a coil end of a secondary coil extending inside the insulating terminal block, and a ground terminal and a secondary terminal provided on the insulating terminal block; And a zero-phase current transformer is extrapolated to the insulated terminal block.