JPS638693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to induction electric equipment, and more particularly to an induction electric equipment in which a main body of the equipment is housed in a grounded tank filled with an insulating medium.

In general, inductive electrical equipment such as oil-insulated or gas-insulated transformers or reactors is constructed by placing an iron core 2 and the A device main body 4 consisting of a three-phase coil 3 wound around an iron core 2 is housed, and an input/output terminal 5 of the device main body 4 is led out from the tank 1 through a bushing 6 inserted into the tank 1. A pressure relief device 7 is provided to prevent damage to the tank 1 in the event of an accident due to a flash arc A between a live part such as an input/output terminal 5 inside the tank 1 and the tank 1 at ground potential.

However, with the recent increase in the capacity of induction electrical equipment, the tanks for those with voltages of 275KV and 500KV have become larger, and the distance between the point of flash arc generation and the pressure relief valve of the pressure relief device has increased. Types with distances of 10 meters or more have appeared, and the arc energy of flash arcs is increasing due to ultra-high voltage.

However, if an internal flash fault occurs in an induction electrical device that uses insulating oil as an insulating medium, the propagation speed of the shock wave in the oil is approximately 1200 m/sec, so
The distance from the flash arc generation point to the pressure relief valve is 10m.
Then, the time required for the shock wave to reach the pressure relief valve is approximately 0.008 seconds, or in other words, approximately 0.42〓 (based on 50Hz). For this reason, although tanks are usually made of steel plates and have the ability to instantly expand to a certain size and increase the internal volume of the tank, they may be destroyed or exploded between the time of the accident and the activation of the pressure relief valve. There is a risk that this may occur.

In addition, when an internal flash fault occurs in induction electrical equipment that uses insulating gas as an insulating medium, the propagation speed of the shock wave in the air is approximately 350 to 400 m/sec.
The distance from the flash arc generation point to the pressure relief valve is 10m.
If the propagation speed of the shock wave is 400 m/sec, then
The time required for the shock wave to reach the relief valve is
It takes 0.025sec (2.5〓 based on 50Hz). for,
Tanks have a much higher probability of breaking or exploding than those filled with oil, and even if the tank does not explode and the pressure relief valve operates effectively, the insulating gas is SF ₆ gas. In some cases, SF ₆ gas may be decomposed by flash arcs and released from pressure relief devices, including toxic gases such as SF ₄ and S ₂ F ₁₀ .

Therefore, no matter which insulating medium is used, the strength of the tank must be increased, which is uneconomical, and if toxic gas is released, a device must be attached to absorb this gas. There are problems such as having to do this.

The present invention has been made in view of the above-mentioned problems, and its purpose is to insert a trigger-type vacuum gap between the charging part of the main body of the device and the tank, and to Internal flash faults can be eliminated by installing a current transformer on either or both sides and applying a high voltage to the trigger electrode of the vacuum gap using the differential current or overcurrent of the current transformer as a signal. To provide an induction electric device capable of igniting a vacuum gap to connect a live part and a tank in the event of an accident to immediately extinguish an internal flash arc, thereby preventing damage or explosion of the tank. . Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings from FIG. 2 onwards.

As shown in FIG. 2, which shows an example of an oil-immersed transformer, the induction electric device according to the present invention has a main body of the device in a tank 8 which is filled with insulating oil as an insulating medium and connected to earth E (grounded). It houses the primary coil 9 and the secondary coil 10, as well as the input terminal 9U of each phase of U, V, and W of the primary coil 9 (only the U phase is shown in the figure) and the secondary coil 10. The output side terminal 10U of each phase of U, V, and W (only the U phase is shown in the figure) is led out from the tank 8 by respective bushings 11 inserted into the tank 8. A trigger type vacuum gap 12 (only the U phase on the primary side is shown in the figure) is connected between both or one of the input terminal and output terminal of each phase in the tank 8 and the inner wall of the tank 8. Each is connected through an intervening connection. The trigger type vacuum gap 12 utilizes the internal discharge to momentarily ground the input and output terminals (live parts) that have caused an accident due to the flash arc A between the tank 8 and the inner wall of the tank 8, thereby eliminating the flash flash arc A. A plurality of insulating cylinders 13 made of cylindrical insulators are coaxially joined to form one insulating cylinder, and both open ends of this insulating cylinder are connected to disks. The inner end of the lead rod 15 is closed by metal end plates 14, 14 having a shape, and the inside is evacuated to a high vacuum to form a vacuum container, and the inner end of the lead rod 15 is airtightly introduced from the center of each metal end plate 14 of this vacuum container. It is supported by each insulating cylinder 13 via a support fitting 17 between electrodes 16 provided in the section, and
Electrode rods 19 with electrodes 18 attached to both ends are appropriately spaced apart on the axis of the vacuum container to form a plurality of gaps 20, and either one (left side in FIG. 2)
This metal end plate 14 is attached to the insulator 21.
Trigger electrode 22 introduced through hermetically through the
The tips of the two are opposed to each other with an appropriate gap between them.

Note that one metal end plate 14 of the vacuum gap 12
The outer end of the lead rod 15 inserted into the other metal end plate 14 is connected to the inner wall of the tank 8 via the connecting wire 23, and the outer end of the lead rod 15 inserted into the other metal end plate 14 is connected to the inner wall of the tank 8 via the connecting wire 24. It is connected inside the tank 8 to input and output terminals that are charging parts. In addition, in FIG. 2, 25a, 25b, 25
C is a shield for protecting the inner surface of the insulating cylinder 13, respectively.

Input and output terminals of each phase (U in Fig. 2)
In the phase (only phases shown), through-type current transformers 26 and 27 are fitted in the tank 8, and these current transformers 26 and 27 do not generate a differential current under normal load operation, In addition to being reversely connected so that a differential current occurs only in the event of an accident caused by flash arc A,
It is connected to the primary coil 28a of the instrument transformer 28. One end of the secondary coil 28b of the instrument transformer 28 is connected to the outer end of the trigger electrode 22 of the vacuum gap 12, and the other end of the secondary coil 28b is connected to the tank 8 and one lead. It is connected to a connecting line 23 that connects the rod 15.

The above configuration prevents a short circuit due to a flash arc A between the inner wall of the tank 8 and any terminal of each phase on the primary or secondary side, for example, the input terminal 9U of the U phase on the primary side. For example, since a short circuit current flows, a current flows through the primary coil 28a of the instrument transformer 28 due to the difference current between the current transformers 26 and 27, and the high voltage generated in the secondary coil 28b of the instrument transformer 28 is applied to the trigger electrode 22 of the vacuum gap 12. As a result, the tip of the trigger electrode 22 and one metal end plate 1 at ground potential.
An arc plasma is generated between
~20 each gap by being about 1/100
The arc plasma short-circuits them all at once. Therefore, the U-phase input terminal 9U on the primary side and the arc potential tank 8 are electrically connected via the vacuum gap 12, and the flashover arc is approximately 0.5〓(10
ms), and the increase in internal pressure is also stopped, thereby reliably preventing damage or explosion of the tank 8.

The connection between the input and output terminals of the vacuum gap 12 and the tank 8 is automatically cut off when the arc plasma interposed between the gaps 20 of the vacuum gap 12 disappears near the natural zero value of the current. In addition, if the insulating medium in the tank 8 is an insulating gas, for example SF ₆ gas, the arc voltage in vacuum is about 1/10 of the arc voltage in SF ₆ gas, so the insulation The input and output terminals are grounded by the vacuum gap 12 in the same way as by oil.

In the above embodiment, in order to obtain the voltage to be applied to the trigger electrode 22 of the vacuum gap 12, the alternating current from the current transformers 26 and 27 is directly input as a signal to the instrument transformer 28. As mentioned above, it is not limited to this,
For example, as shown in FIG.
A DC power supply is used to apply high voltage to the electrodes 22 through the inverter 29, which is equipped with an inverter 29 equipped with an automatic stop timer as an external circuit, and a current transformer 26, Relay 30 activated by the differential current of 27
It may also be done by

Furthermore, in the embodiment described above, in order to induce a high voltage directly or indirectly in the instrument transformer 28, the difference between the reversely connected current transformers 26 and 27 fitted to the input and output terminals in the tank 8 is Although we have described the case where current is used as a signal, the present invention is not limited to this.For example, a through-type current transformer may be fitted to either the input terminal or the output terminal, and the overcurrent may be directly connected to the voltage transformer or It may also be used as a signal that indirectly induces a high voltage.

Further, in the above embodiment, the vacuum gap 12 is disposed inside the tank 8, but the present invention is not limited to this. For example, the vacuum gap may be housed in a tank separate from the tank 8, and
This tank may be arranged above the tank 8 in line with the bushing 11, and the inlet and outlet terminals in the tank 8 and the vacuum gap may be connected through insulating spacers.

Further, in the above-described embodiment, the vacuum gap 12 is described as having a plurality of gap 20, but the vacuum gap 12 is not limited to this and may have one gap in a single insulating cylinder. Of course, as described above, the present invention provides an induction electric device in which the main body of the device is housed in a tank that is sealed with an insulating medium and is grounded. A current transformer is installed on both the input side and the output side of the device main body, and the differential current or overcurrent of the current transformer is used as a signal to apply a high voltage to the trigger electrode of the trigger type vacuum gap. Since the tank is provided so as to apply , flash arcs due to internal flash faults can be extinguished immediately, and damage or explosion of the tank can be reliably prevented. Therefore, it is not necessary to increase the strength of the tank as the tank becomes larger, which is economical, and even if the insulating medium is SF ₆ gas, it is necessary to provide a device to absorb the toxic decomposition gas of SF 6 gas. It has the effect that there is no waste.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional induction electric device, FIG. 2 is a schematic diagram of an induction electric device according to the present invention,
FIG. 3 is a circuit diagram of another embodiment of the main part of the present invention. 8...Tank, 9...Primary side coil, 9U...
Input terminal, 10... Secondary coil, 10U... Output terminal, 12... Vacuum gap, 22... Trigger electrode, 26, 27... Current transformer, 28... Instrument transformer.

Claims (1)

[Claims] 1. In an induction electric device in which the main body of the device is housed in a tank sealed with an insulating medium and grounded, a trigger-type vacuum gap is inserted between the live part of the device main body and the tank, and the input side of the device main body and A current transformer is disposed on both or either one of the output sides, and a high voltage is applied to the trigger electrode of the trigger type vacuum gap using the differential current or overcurrent of the current transformer as a signal. Features induction electrical equipment.