JPH09223632A - Neutral-point current-limiting apparatus for transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a neutral-point current-limiting apparatus by which a site required for its installation is reduced by a method wherein an airtight container in which an insulating gas is sealed and in which a resistor is housed is provided and the neutral terminal of a transformer is pulled airtightly into the airtight container so as to be grounded via the resistor. SOLUTION: The neutral-point terminal of a transformer 1 which is placed on the ground 14 is pulled into an airtight container 20 via a housing 2 so as to be connected to a conductor 39. The conductor 39 rises to the upper part inside the airtight container 20, and it is passed airtightly through a spacer 21 so as to be connected to a resistor 27 inside an airtight container 19. The upper part side of the resistor 27 is connected to a conductor 16, and it is passed airtightly through the spacer 21 so as to be pulled into an airtight container 22. The conductor 16 is pulled airtightly out to the outside of the airtight container 22, it is supported by a support 23, and it rises along the left side face of the airtight container 19 so as to be connected to a grounding terminal E on the surface of the transformer 1. In addition, a changeover operating device 18 for the resistor 27 and a temperature detector 17 for an insulating gas inside the airtight container 19 are attached to the left side face of the airtight container 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for grounding a neutral point of a transformer via a resistor.

[0002]

2. Description of the Related Art When a large current flows to the neutral point of a transformer in the event of an accident, electromagnetic interference may occur in low-voltage distribution lines and communication lines of power plants and substations, and the equipment connected to them may be damaged. . Therefore, a resistor is provided in series with the neutral point to limit the magnitude of the neutral point current flowing in the event of an accident.

FIG. 4 is a side view showing the configuration of a conventional neutral point current limiting device of a transformer. The neutral point terminal of the transformer 1 mounted on the ground 14 is drawn out from the bushing 2 to the outside. The cable head 4 is mounted on the gantry 5 adjacent to the transformer 1. Conductor 3 from bushing 2
Is connected to the cable 6 via the cable head 4.

Further, in FIG. 4, the cable 6 is buried in the ground through the frame 5, and the transformer 1 and the frame 5 are connected.
The wiring is wired up to the lower part of the pedestal 7 separately installed. The cable 6 is re-raised up through the pedestal 7 to the upper cable head 47, and via the conductor 8, the resistance box 1
It is connected to the 0A bushing 9. Three resistance boxes 10A, 10B, 10C are stacked on the ground 14 in a state of being insulated from each other via the insulator 12.
Metal resistors 11 are housed in the resistance boxes 10A, 10B and 10C, respectively. The conductor 8 is drawn into the resistance box 10A via the bushing 9 and drawn to the outside of the resistance box 10A via the internal metal resistor 11 to be connected to the conductor 8A. Similarly to the conductor 8, the conductor 8A is drawn into the resistance box 10B and drawn to the outside through the metal resistor 11 and connected to the conductor 8B. Similarly, the conductor 8B has a resistance box 10C.
It is drawn in to the outside through the metal resistor 11 and finally connected to the ground terminal E. The gantry 7 and the resistance box 10C are surrounded by a wire fence safety fence 13.

In FIG. 4, a metal resistor 11 is provided for resistively grounding the neutral point of the transformer 1. The metal resistor 11 and the conductors 3, 8, 8A, 8A, 8B, 8C are
It is normally at ground potential, but it has a potential when a fault current flows. Since those having these potentials are exposed to the outside, a safety fence 13 is stretched around to prevent the risk of electric shock. In addition, the resistance boxes 10A, 10B, 10
The reason that C is provided separately from the transformer 1 is that maintenance personnel can go around the transformer 1.

[0006]

However, the above-mentioned conventional neutral point current limiting device has a problem that a large site is required for installation. That is, in FIG. 4, for example, in order to install a neutral point current limiting device with an insulation class of No. 60, about 1 m as L3 is required to install the pedestal 5, and about 9 m as L2 is required to install the safety fence 13. Moreover, the safety fence 13 had to be provided on a site separate from the transformer 1. Further, the depth in FIG. 4 was about 4 m, and a total site area of about 40 m ² was required. As the insulation class further increases, there is a part of the resistance box, which is the exposed portion of the power supply, and the site area becomes larger because it is necessary to increase the distance from the safety fence 13.

Further, the conventional neutral-point current limiting device has a problem in that a great amount of labor is required when it is desired to change the resistance value of the resistor after changing the system. That is, in FIG. 4, when changing the resistance value, the stacked resistance boxes 10A, 10B, 10C are temporarily lowered, and further,
After disassembling the inside of the resistance boxes 10A, 10B, 10C, the metal resistor 11 is reassembled. After that, the metal resistor 11 is housed inside the resistance boxes 10A, 10B, 10C, and again, the resistance boxes 10A, 1
0B and 10C are stacked. Moreover, during that time, it was necessary to stop the operation of the transformer 1.

An object of the present invention is to reduce the site required for installation and to change the resistance value in a short time.

[0009]

In order to achieve the above object, according to the present invention, there is provided a device for grounding a neutral point of a transformer through a resistor, which is filled with an insulating gas. It is preferable to provide a hermetically-sealed container in which the resistor is housed, and to neutralize the neutral terminal of the transformer in the hermetically-sealed container to be grounded via the resistor. Thereby,
Since there is no exposed part of the power distribution section, there is no need for a safety fence and the site required for installation is greatly reduced. In addition, since the voltage applying section is insulated with SF ₆ gas, which has a high dielectric strength,
The device itself becomes compact.

Further, in such a structure, a switching operator capable of switching the resistance value of the resistor outside the closed container may be provided. Thereby, the resistance value of the resistor can be changed in a short time. Further, in such a configuration, a gas blower that circulates the insulating gas via a radiator may be provided. Thereby, even if a large current flows through the resistor and the temperature of the insulating gas rises, the radiator can lower the temperature to an allowable temperature.

Further, in such a structure, a temperature detector is provided for outputting a signal when the temperature of the insulating gas in the closed container exceeds a predetermined temperature, and the gas blower is provided when the signal of the temperature detector is output. May operate. Thereby, the gas blower automatically stops when the temperature of the insulating gas in the closed container falls below a predetermined temperature, for example, an allowable temperature, and waste of energy can be avoided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG. 1 is a side view showing the configuration of a neutral point current limiting device of a transformer according to an embodiment of the present invention. An airtight container 20 is airtightly joined to the upper portion of the transformer 1 placed on the ground 14. Another closed container 19 is hermetically joined to this closed container 20 via a spacer 21. Further, another hermetic container 22 is hermetically joined to the hermetic container 19 via a spacer 21. Each of the hermetically sealed containers 20, 19, 22 is filled with SF ₆ gas which is an insulating gas, and is gas-divided via a spacer 21. Further, on the side surface of the hermetically sealed container 19, the hermetically sealed containers 25 are airtightly joined to each other at upper and lower portions. The airtight container 25 communicates with the airtight container 19 inside, and SF
Filled with ₆ gas. Further, the closed container 25 is formed in a U shape, and a gas blower 26 and a radiator 24 placed on the pedestal 15 are interposed in the middle thereof. The closed container 25 is for cooling the insulating gas in the closed container 19. The insulating gas is circulated in the closed container 25 by the gas blower 26 and the heat of the insulating gas is dissipated by the radiator 24.

Further, in FIG. 1, the neutral point terminal of the transformer 1 placed on the ground 14 is drawn out into the closed container 20 via the bushing 2 and connected to the conductor 39. The conductor 39 rises upward in the closed container 20, penetrates the spacer 21 in an airtight manner, and the resistor 27 in the closed container 19 is sealed.
It is connected to the. The upper side of the resistor 27 is connected to the conductor 16, penetrates the spacer 21 in an airtight manner, and is drawn out into the closed container 22. The conductor 16 is airtightly drawn to the outside of the closed container 22. The conductor 16 is a support 23
It is supported by, and falls along the left side surface of the closed container 19, and is connected to the ground terminal E on the upper surface of the transformer 1. In addition, a resistor 27 is provided on the left side surface of the closed container 19.
A resistance value switching operator 18 and a temperature detector 17 for the insulating gas in the closed container 19 are attached.

In FIG. 1, a resistor 27 is provided for resistively grounding the neutral point of the transformer 1. That is, the neutral point terminal of the transformer 1 passes through the bushing 2 and the conductor 39,
It is connected to the ground terminal E via the resistor 27 and the conductor 16. Since the resistor 27 is housed in the closed container 19,
There is no exposed part of the electricity section, so no safety fence is required. Therefore, the site required for installation is greatly reduced. In addition, since the electricity applying section is insulated with SF ₆ gas having high dielectric strength, the apparatus itself becomes compact. The range required for the installation is only the dimension L1 protruding from the right side surface of the transformer 1 to the right by the width of the gantry 15, and the depth of FIG. 1 is about 1 as well.
m is enough. For example, in the case of a neutral point current limiting device having an insulation class of No. 60, L1 is about 2 m, and the total site area is about 2 m ² . Therefore, it is reduced by about an order of magnitude compared to the site area required by the conventional device. As the insulation class further increases, conventionally, as described above, there is an exposed part of the power-supplying part called the resistance box, so that the site area becomes larger because it is necessary to further increase the distance from the safety fence. On the other hand, in the configuration of FIG. 1, even if the insulation class increases, the closed container 25 is for cooling the insulating gas,
L1 size and depth do not increase. Therefore, as the insulation class increases, the effect of reducing the site increases as compared with the conventional device.

Further, in FIG. 1, even if a large current flows through the resistor 27 and the temperature of the insulating gas rises, it can be lowered to the allowable temperature by the radiator 24. Therefore, the heat-resistant grade of the device can be reduced, and eventually the cost of the device can be reduced. In addition, the temperature detector 17 has a closed container 19
A temperature sensor 28 (FIG. 2) disposed inside is provided, and a signal is output when the temperature of the insulating gas exceeds a predetermined temperature. When the signal from the temperature detector 17 is output, the gas blower 26 operates.
As a result, the gas blower 26 automatically stops when the temperature of the insulating gas in the closed container 19 becomes equal to or lower than a predetermined temperature, for example, the allowable temperature of the device, and waste of energy can be avoided.

FIG. 2 is a side view of a partial crushing essential portion showing the detailed structure of the resistor shown in FIG. The resistor 27 is a series resistor 27A, 27 in which a plurality of ceramic resistors are connected in series.
It consists of B and 27C, and is housed in the closed container 19. The series resistors 27A, 27B and 27C are shown in FIG.
The series resistors 27D, 27 having the same configuration as described in
Two more E and 27F are provided on the depth side in FIG. 2, and a total of six series resistors are arranged on the circumference at equal intervals. The lower parts of the series resistors 27A to 27F are both fixed to the shield conductor 40 and connected to the conductor 39. The upper portions of the series resistors 27A to 27F have through-hole terminals 35 provided on the insulating plate 35 via conductors 36, respectively.
A is connected. The conductor 37 is connected to the connecting metal fitting 36A between the uppermost ceramic resistor of the series resistors 27A to 27F and the next second-stage ceramic resistor, and the through terminal 35B. Further, the connecting metal fitting 3 between the second-stage ceramic resistance and the third-stage ceramic resistance of the series resistors 27A to 27F is provided via the conductor 38.
7A and the through terminal 35C. The switching conductor plate 34 has six contacts 34A, and in the state of FIG. 2, each contact 34A is in contact with the through terminal 35A.
The switching conductor plate 34 is fixed to the switching shaft 30 and is rotatable around the switching shaft 30. Shield conductor 29
Holds the insulating plate 35 fixedly via the insulating rod 32, and also supports the switching shaft 30 rotatably. The shield conductor 29 is fixedly supported by the conductor 16, and further, the conductor 1
6 is fixed to the closed container 19 via a spacer 21.

Further, in FIG. 2, the operating shaft 31 has a closed container 1
It is rotatably supported on the inner wall of 9. The operating shaft 31 is
A spiral thread groove is formed in the center, and the switching shaft 3
The same spiral thread groove is formed in the direction 0. The thread groove of the operating shaft 31 is fitted to that of the switching shaft 30, and when the operating shaft 31 is rotated about the shaft, the switching shaft 30 also rotates about the shaft.
The operation shaft 31 penetrates the left side wall of the closed container 19 in an airtight manner, and is provided in the box of the switching operator 18 with the manual handle 18
A is attached. Opening / closing door 1 of switching operator 18
When 8B is opened and the manual handle 18A is rotated, the operation shaft 31 is rotated, the switching shaft 30 is also rotated accordingly, and the contact 34A of the switching conductor plate 34 is connected to the through terminal 35B.
Switch to 35C.

FIG. 3 is a view on arrow A of FIG.
It is the figure which looked at the lower part from the lower part of 1. As described above, the series resistors 27A to 27F are arranged in six equal parts. Through terminals 35A, 35B, 35C are provided on the insulating plate 35,
Among them, the through terminal 35A is provided right above each series resistor 27A to 27F. Through terminal 35A, 3
5B and 35C are arranged at equal intervals on the circumference between the respective through terminals 35A. The switching conductor plate 34 is provided with contacts 34A arranged at equal intervals on the lower surface of the protrusions 34B radially extending in six directions at the circumferential ends, and contacts the through terminals 35A. When the switching conductor plate 34 is rotated by the switching shaft 30, the contact 34 </ b> A contacts the through terminal 35.
It separates from A and comes into contact with the next through terminal 35B. Further, when the switching conductor plate 34 rotates, the contact 34
A separates from the through terminal 35B and comes into contact with the next through terminal 35C. After that, the contact 34A again contacts the through terminal 35A, and the state shown in FIG. 3 is obtained.

Returning to FIG. 2, when the switching conductor plate 34 rotates, the number of series-connected ceramic resistors of the series resistors 27A to 27F changes. That is, the resistance value of the resistor 27 can be easily and quickly changed from the outside of the closed container by the manual handle. In the embodiment of FIG. 2, the case where the number of series resistors is 6 is shown, but in general, M, N
Is a natural number, the number of series resistors of each series resistor is M, the number of parallel series resistors is N, and the values of M and N are selected according to the value of the ground resistance. The positions of the connection fittings 36A and 37A for connecting the conductors 37 and 38 in FIG. 2 are also determined according to the resistance value to be switched depending on the system.

[0020]

As described above, the present invention is provided with the hermetically sealed container in which the insulating gas is sealed and the resistor is housed, and the neutral terminal of the transformer is hermetically drawn into the hermetically sealed container. Grounded via a container. This significantly reduces the site required for installation and saves equipment site.

Further, in such a construction, a switching operator capable of switching the resistance value of the resistor outside the closed container is provided. The resistance value of the resistor can be changed in a short time, labor for switching is unnecessary, and the down time of the transformer can be shortened. Moreover, in such a structure, the gas blower which circulates an insulating gas through a radiator was provided. As a result, even if a large current flows through the resistor and the temperature of the insulating gas rises, the radiator can lower the temperature to an allowable temperature, which ultimately reduces the cost of the device.

Further, in such a structure, a temperature detector is provided which outputs a signal when the temperature of the insulating gas in the closed container exceeds a predetermined temperature, and when the signal of this temperature detector is output, a gas blower is provided. Shall work. Thereby, waste of energy can be avoided.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of a neutral point current limiting device of a transformer according to an embodiment of the present invention.

FIG. 2 is a side view of a partial crushing essential portion showing the detailed configuration of the resistor of FIG.

FIG. 3 is a view taken in the direction of arrow A in FIG. 2;

FIG. 4 is a side view showing a configuration of a conventional neutral point current limiting device of a transformer.

[Explanation of symbols]

1: Transformer, 2: Bushing, 19, 20, 22, 2
5: airtight container, 24: radiator, 26: gas blower, 1
8: Switching operator, 17: Temperature detector, 27: Resistor

Claims (4)

[Claims] 1. A device for grounding a neutral point of a transformer through a resistor, the device comprising a hermetically-sealed container in which an insulating gas is enclosed and a resistor is housed, and the transformer is provided in the hermetically-sealed container. A neutral point current limiting device of a transformer, wherein a neutral terminal of the transformer is drawn in an airtight manner and is grounded via the resistor. 2. The neutral point current limiting device of a transformer according to claim 1, further comprising a switching operator capable of switching the resistance value of the resistor outside the closed container. . 3. The method according to claim 1, wherein
A neutral point current limiting device for a transformer, comprising a gas blower for circulating insulating gas through a radiator. 4. The temperature detector according to claim 3, further comprising a temperature detector that outputs a signal when the temperature of the insulating gas in the closed container exceeds a predetermined temperature, and the signal of this temperature detector is output. A neutral current limiting device for a transformer, characterized in that the gas blower operates when it is turned on.