JPH11203993A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit breaker capable of preventing maloperation of a breaker by interrupting flow of a grounding current to the inside of a bushing converter when an outside grounding is provided in the external air of a bushing. SOLUTION: A shield ring 13 is provided at a position proximal to a bushing converter 3 between a main circuit terminal 1 and the bushing converter 3 at the periphery of a bushing 2. The shield ring 13 is insulated from a converter cover, and is connected to an earth via the outside of the bushing converter 3 by means of a grounding conductor 19. Thereby, an outside grounding current bypasses the converter 3, and flows, and a mistaken alerting is never generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker used in power plants, substations, and the like, and more particularly, to stabilizing the protection operation thereof.

[0002]

2. Description of the Related Art High voltage. A breaker for interrupting the power line as necessary is used at a key point in a large current power line. When an abnormality such as a ground fault occurs at the load or at another place on the power line, the circuit breaker performs an operation of interrupting the power line according to a command from a device for detecting the abnormality. When an abnormality occurs in the system, it is configured to shut off by itself without receiving a command from others to prevent the accident from spreading.

FIG. 9 is an overall configuration diagram (front view) of a conventional circuit breaker, and FIG. 10 is a side view of FIG. 9 and 10, 1 is a main circuit terminal connected to the power line, 2 is a lower part of the main circuit terminal 1 formed of an insulating tube, and a current conduction path 21 connected to the main circuit terminal 1 is provided inside. It is a bushing provided. Reference numeral 3 denotes a bushing current transformer which is provided below the bushing 2 and detects and monitors a current flowing through the current conducting path 21 (there is a case where monitoring and detection are separated). If the current value exceeds a predetermined level, a warning signal is issued that the current inside the circuit breaker is abnormal.

[0004] Reference numeral 4 denotes a tank in which a shutoff device (not shown) for shutting off the current conducting path 21 is housed. The inside of the tank 4 and the bushing 2 is generally filled with an insulating gas such as SF6. Reference numeral 5 denotes a leg for supporting the tank 4, which is grounded to the ground.

FIG. 11 is an enlarged view of a main portion in the vicinity of the bushing current transformer 3 shown in FIG. In FIG. 11, reference numeral 22 denotes an internal shield provided inside the bushing 2, and reference numeral 25 denotes a holder for supporting the internal shield 22, but these are not directly related to the present invention, and a detailed description thereof will be omitted. 23 is a flange for attaching the bushing 2 and is made of metal in order to obtain structural strength. Reference numeral 24 denotes an airtight frame that structurally supports the flange 23. Although not shown in detail, it is electrically connected to the leg 5 and grounded. Numeral 31 denotes a current detecting coil constituting the bushing current transformer 3, which is provided outside the airtight frame 24 so as to cover the current conducting path 21 and to secure the withstand voltage performance of the main circuit and facilitate maintenance. I have. Reference numeral 32 denotes a cover (also referred to as a current transformer cover) of the current detection coil 31.

Next, the operation will be described with reference to the drawings. During normal operation, current is conducted between the two main circuit terminals 1 in FIG. Since this current flows through the current conducting path 21, the current is detected by the current detecting coil 31 of the bushing current transformer 3 and monitored by a monitoring circuit (not shown). If there is no abnormality in the detected current value, no signal is output. Next, when the value of the current flowing through the current conduction path 21 exceeds a predetermined value for some reason, a monitoring circuit (not shown) determines that an abnormality has occurred within the protection range of the current detection coil 31 of the circuit breaker. Although not shown, an alarm is displayed for an abnormality in the protection range of the current detector coil 31 of the circuit breaker, and the main circuit is shut off by operating the shut-off device in the tank 4.

In rare cases, for example, when a lightning strike or the like occurs in a connected transmission line, the lightning strike triggers a lightning strike between the main circuit terminal 1 and one of the ground potential portions, for example, the flange 23. In some cases, flashover (air discharge) occurs through an external space, and no abnormality occurs in the current flowing through the current conducting path 21. In this case, originally, there is no abnormality in the current value, and the current detection coil 31 of the circuit breaker is used.
Since there is no abnormality within the protection range, the bushing current transformer 3 does not detect the abnormal current and the abnormality display should not be displayed. However, the flash current generally has a high peak value, and a part of the flash current flows through the airtight frame 24 (that is, flows inside the current detection coil 31), so that the output signal of the bushing current transformer 3 becomes abnormal. As a result, an erroneous alarm signal indicating that an abnormality has occurred is transmitted even though an abnormality has not occurred within the protection range of the current detection coil 31 of the circuit breaker. When such an erroneous display is transmitted, it is determined that an abnormality has occurred within the protection range of the current detection coil 31 of the circuit breaker, and one or more other circuit breakers other than the circuit breaker are operated, and unnecessary operation is performed. There is a problem that the range of the power outage is extended.

At this time, the circuit breaker also naturally operates, but the operation itself of the circuit breaker is not regarded as a problem here. Because, even when an abnormality in the protection range of the current detection coil 31 of the circuit breaker is not detected, the flashover is detected by another protection system for the current detection coil (not shown) (for example, ground fault detection). This is because it is interrupted by any one of the circuit breakers.

[0009]

Since the conventional circuit breaker is configured as described above, the flashing occurring outside the bushing causes the output of the bushing current transformer to become abnormal,
There has been a problem that malfunction may occur as if an abnormality occurred within the protection range of the current detection coil of the circuit breaker.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and when an external flash ground occurs in the air outside the bushing, the flow of the ground fault current into the bushing current transformer is interrupted. An object of the present invention is to obtain a circuit breaker that can prevent a malfunction of the circuit breaker.

[0011]

A circuit breaker according to the present invention is constituted by an insulator tube having a main circuit terminal connected to a power line at one end, a bushing having a current conduction path inside, and a bushing having the other end connected to the other end of the bushing. A current detecting means provided for detecting a current flowing through the current conducting path, and interrupting a current flowing through the current conducting path when a current value detected by the current detecting means connected to the current conducting path exceeds a predetermined value. And a current interrupting means, which is provided around the bushing, between the current detecting means and the main circuit terminal, at a position close to the current detecting means, and is connected to the bushing from the main circuit terminal. And an external flash ground current bypass means for bypassing the external flash ground current flowing through the outside space to the ground line. The flash-to-ground fault current bypass means allows the generated flash-to-ground fault current to escape to the ground through the outside of the bushing current transformer, so that the bushing current transformer does not emit a false alarm signal.

The circuit breaker according to the present invention is provided at a position around the bushing, between the current detecting means and the main circuit terminal, close to the current detecting means, and has a shield ring having an inner diameter larger than a maximum outer diameter of the bushing. And grounding means for grounding the shield ring. The shield ring receives the external flash ground fault generated from the main circuit terminal, and the grounding means escapes the received ground fault current to the ground, so that the bushing current transformer does not give a false alarm during the external flash ground fault. Act on.

In the circuit breaker according to the present invention, the grounding means includes a conductor wire connected to the ground or a grounded object connected to the ground via the shield ring via the outside of the current detecting means. A grounding means consisting of a conductor connected to the ground or a grounded object connected to the ground via the outside of the current detecting means prevents the bushing current transformer from generating a false alarm in the event of an external flash ground. Act like so.

In the circuit breaker according to the present invention, the shield ring is held by insulating means provided on the surface of the current detecting means. The insulating means acts to insulate between the shield ring and the cover of the current detecting means so as to eliminate the possibility that the external flash ground current flows through the inside of the current detecting means.

In the circuit breaker according to the present invention, the insulating means has an axial adjusting mechanism for moving the position of the shield ring at least in the axial direction with respect to the center axis of the bushing. The axial adjustment mechanism provided on the insulating means makes it possible to adjust the distance between the shield ring and the flange below the bushing, so that the shield performance and the current bypass performance of the shield ring can be optimally adjusted.

The circuit breaker according to the present invention has a transverse adjusting mechanism in which the insulating means moves the position of the shield ring with respect to the center axis of the bushing in a direction perpendicular to the axis. The lateral adjustment mechanism provided in the insulating means acts so that the shielding performance and the current bypass performance of the shield ring can be optimally adjusted.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1 is an overall configuration diagram of a circuit breaker according to Embodiment 1 of the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a cross-sectional view showing a main part of FIG. In the figure, 1 is a main circuit terminal connected to the power line, 2 is a lower part of the main circuit terminal 2 formed of an insulating tube, and a current conducting path 21 connected to the main circuit terminal 1 is provided inside. Bushing. Numeral 3 denotes a bushing current transformer (current detecting means according to the present invention) which is provided below the bushing 2 and detects and monitors a current flowing through the current conducting path 21 (some monitoring and detection are separated). If the detected current value exceeds a predetermined level, the bushing current transformer 3 issues an alarm signal indicating that the current inside the circuit breaker is abnormal. (The output of this alarm may be performed by another device connected to the bushing current transformer 3)

Reference numeral 4 denotes a tank in which a shutoff device (not shown, shutoff means according to the present invention) for shutting off the current conducting path 21 is accommodated. The inside of the tank 4 and the bushing 2 is generally made of an insulating gas such as SF6. Is satisfied. Reference numeral 5 denotes a leg for supporting the tank 4, which is grounded to the ground.

FIG. 3 is a sectional view of a main part in the vicinity of the bushing current transformer 3 in order to explain the structure in the vicinity thereof in more detail. In FIG. 3, reference numeral 22 denotes an internal shield provided inside the bushing 2, and reference numeral 25 denotes a holder for supporting the internal shield 22, but these are not directly related to the present invention, and a detailed description thereof will be omitted. 23 is a flange for attaching the bushing 2 and is made of metal in order to obtain structural strength. Reference numeral 24 denotes an airtight frame that structurally supports the flange 23. Although not shown in detail, it is electrically connected to the leg 5 and grounded. 31 is a bushing current transformer 3
Are provided outside the airtight frame 24 so as to surround the current conducting path 21 with the current detecting coil constituting the above, and to ensure the withstand voltage performance of the main circuit and facilitate maintenance.
32 is a cover of the current detection coil 31.

A in FIG. 1 is an auxiliary line for explanation, and shows a path of a current flowing between the main circuit terminal 1 and the earth at the time of an external flash ground. B indicates a normal main circuit current path.

Reference numeral 13 denotes a shield ring provided at a position near the bushing current transformer 3 between the main circuit terminal 1 and the bushing current transformer 3 along the outer periphery of the bushing 2.
Reference numeral 15 denotes a station post insulator (insulating means according to the present invention) that holds the shield ring 13 and is mounted on the current transformer cover 32. Reference numeral 14 denotes a gap provided between the shield ring 13 and the current transformer cover 32 by the station post insulator 15.

Reference numeral 19 denotes a ground conductor (ground means) having one end connected to the shield ring 13 and the other end connected to the leg 5 of the tank at a point 192. Point 192 is a ground point below bushing current transformer 3. Although not shown, it goes without saying that the leg 5 is grounded. The shield ring 13 and the grounding conductor 19 are the external flash ground fault current bypass means according to the present invention.

Next, the operation will be described with reference to the drawings.
There is no difference from the conventional circuit breaker in the normal condition where no external flash ground fault occurs. That is, the current flowing into the main circuit terminal 1 flows through the current conduction path 21 (current B) and passes through the current detection coil 31 in the bushing current transformer 3. Then, it is determined whether or not the output signal of the bushing current transformer 3 is within the bushing current transformer 3 or within a predetermined value range determined by another circuit (not shown). If it is within the normal range, no special operation is performed.

Next, a case where an external flash ground fault occurs will be described. Since the shield ring 13 is provided between the main circuit terminal 1 and the bushing current transformer 3, the shield ring 13 is closer to the main circuit terminal 1 than any other grounded object. Therefore, flashes generated from the main circuit terminal 1 pass through the outside of the bushing 2 (route A in the drawing) and always occur with the shield ring 13.

At this time, the shield ring 13 is connected to the ground conductor 1.
9 (grounding means according to the present invention), which is grounded via the outside of the bushing current transformer 3 and the shield ring 13 is insulated from the cover 32 and the flange 23 of the bushing current transformer 3. The external flash ground current A flows outside the bushing current transformer 3 by bypass, and has no effect on its output.

The structure of the external flash ground fault current bypass means will be described in more detail. Needless to say, the shield ring 13 is made of a conductive metal, but its cross-sectional area needs to have a current capacity capable of withstanding an external flash ground fault current. The inner diameter of the shield ring 13 is determined as follows. That is, when an external flash occurs, the shield ring 13 has a certain potential due to the impedance of the ground conductor 19, but if the distance between the shield ring 13 and, for example, the flange 23 is too short, this potential causes a flash between the two. Occurs. The current caused by the flash passes through the inside of the bushing current transformer 3 and leads to malfunction, which is not preferable. The inner diameter is set so that an appropriate distance can be set so that such flashover does not occur.

If the mounting position of the shield ring 13 (that is, determined by the thickness of the gap 14 or the length of the station post insulator 15) is too close to the main circuit terminal 1, the original withstand voltage function of the bushing is impaired. If it is too close to the current transformer cover 32, the function of bypassing the flash current will be reduced.
It is appropriate to set it to 10 cm or more.

Although the number of the ground conductors 19 is one or two in the figure, it may be larger and thicker. Ground conductor 1
It is an essential condition that the grounding point 192 of 9 is closer to the ground than the bushing current transformer 3. Station post insulator 1
5 may be of any other type or material as long as it has a function of completely insulating the shield ring 13. If the ground conductor 19 has sufficient mechanical strength,
The station post insulator 15 is not always necessary.

Since the external flash ground fault current bypass means has a very simple structure including the shield ring 13 and the ground conductor 19, it is characterized in that it can be easily installed on site in an existing circuit breaker. In that case shield ring 13
May be configured by combining two semicircular rings that are split into two. Alternatively, a plurality of arc-shaped parts may be combined in a ring shape.

Embodiment 2 FIG. FIG. 4 is a main part configuration diagram of a circuit breaker according to Embodiment 2 of the present invention. In FIG.
Portions similar to those described above are denoted by the same reference numerals, and detailed description thereof will be omitted (the same applies to each drawing below). Another method for preventing the flash current A from passing through the bushing current transformer 3 is as follows.
As shown in FIG. 4, the arc phone 40 is connected to the bushing current transformer 3.
And close to the surface facing the main circuit terminal 1. The current transformer cover 32 or the flange 23 and the arc phone 40 are electrically insulated 4
1 (insulating means according to the present invention). The arcphone 40 is grounded via the grounding conductor 19 via the outside of the bushing current transformer 3.

Embodiment 3 FIG. 5 is an overall configuration diagram of a circuit breaker according to Embodiment 3. FIG. 6 is a side view of FIG. In the figure, reference numeral 51 denotes a direct ground conductor directly grounded from the shield ring 13 to the ground. By directly grounding to the ground, the impedance can be further reduced as compared with grounding via the leg 5 as shown in FIG. 1, so that the effect of improving the bypass effect can be obtained.

Such a direct grounding conductor 5 for directly grounding
1 can also be applied to the arc phone 40 of FIG. 4 of the second embodiment.

Embodiment 4 FIG. It is well known that the height and outer diameter of the bushing 2 vary depending on the voltage level of the transmission and distribution line in which the circuit breaker is used. In addition, the size of the bushing current transformer 3 (or the size of the current transformer cover 32 in some cases) varies depending on the current capacity to be supplied. FIG. 1 of the first embodiment
The inner diameter of the shield ring 13 described in (1) needs to be determined according to the outer diameter of the lower part of the bushing 2. However, since the bushing 2 is manufactured with a series of dimensions, the shield ring 13 It is possible to make the outer diameter dimensions various. However, it is extremely uneconomical to arrange the station post insulators 15 shown in FIG. 3 in various sizes with different heights and thicknesses because the types are too large.

Therefore, the mounting height of the shield ring 13 can be freely adjusted, and a mounting tool that can be used in common for the shield rings 13 having different outer diameters, that is, the diameter and the height are free. It is desirable to have a fixture that can be adjusted to a minimum. FIG. 7 shows an example of a fixture invented for such a purpose.

In the figure, reference numeral 42 denotes two ceramic or plastic L-shaped angles, each having an oblong mounting hole 43, and a bolt nut 44 inserted into the oblong hole 43. The height and mounting diameter can be adjusted. In the figure, L is a shield ring 13 and a flange 23.
And the insulation distance between L and L.
Can be adjusted.

The dimension L is extremely important for ensuring the function of the flash current bypass means. If L is too short, the current flows through the bushing current transformer 3 even if the shield ring 13 receives the flash current. Part of it will flow and the initial purpose will not be achieved. If L is too large, the original withstand voltage performance of the bushing 2 will be reduced. That is, what adjusts this L is the insulation rate adjusting means. The insulation rate adjusting means may be of any other type as long as the gap L can be adjusted, that is, as long as it can correspond to the diameter of the shield ring 2, and may be as shown in FIG.

In FIG. 8, reference numeral 46 denotes a porcelain tube having a screw hole at an upper portion and a mounting leg at a lower portion to ensure insulation of the shield ring 13. Reference numeral 47 denotes a height adjusting insulator having a screw 48 which can be screwed into a screw hole of the porcelain tube 46 to adjust the height. Reference numeral 49 denotes an oblong hole provided on the shield ring 13 in the radial direction, and the position in the radial direction can be adjusted by a bolt 44 inserted therein.

[0038]

As described above, according to the present invention, the air flows from the main circuit terminal through the outer space of the bushing around the bushing, between the current detecting means and the main circuit terminal, at a position close to the current detecting means. Since the external flash ground fault current bypass means for bypassing the external flash ground fault current to the ground line is provided, the flashing ground fault current is detected as an abnormality within the protection range of the current detection coil of the circuit breaker by the bushing current transformer, There is an effect that no alarm output is output.

Further, according to the present invention, the external flash ground fault current can be bypassed with a very simple configuration using the shield ring and the grounding means for grounding the shield ring.

Further, according to the present invention, the grounding means for grounding the shield ring via the outside of the current detecting means is provided, so that the external flash ground fault current reliably bypasses the bushing current transformer. be able to.

Further, according to the present invention, since the shield ring is held insulated from the current transformer cover, an external flash ground fault current can be ensured to bypass the bushing current transformer.

Further, according to the present invention, the insulating means can adjust the position of the shield ring in the axial direction or the direction perpendicular to the axis, so that the effect of the shield ring can be easily ensured.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a circuit breaker according to Embodiment 1 of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a detailed sectional view of a main part of FIG. 1;

FIG. 4 is a detailed sectional view of a main part of a circuit breaker according to Embodiment 2 of the present invention.

FIG. 5 is an overall configuration diagram of a circuit breaker according to Embodiment 3 of the present invention.

FIG. 6 is a side view of FIG. 5;

FIG. 7 is a detailed configuration diagram of main parts of a circuit breaker according to Embodiment 4 of the present invention.

FIG. 8 is another detailed sectional view of the circuit breaker according to Embodiment 4 of the present invention.

FIG. 9 is an overall configuration diagram of a conventional circuit breaker.

FIG. 10 is a side view of FIG. 9;

11 is a configuration diagram of a main part of FIG. 9;

[Explanation of symbols]

1 main circuit terminal, 2 bushing, 3 bushing current transformer, 13 shield ring,
14 gap, 15 station post insulator, 19 ground conductor, 21 current conduction path,
31 current detection coil, 32 current transformer cover,
A external flash ground current, 51 direct ground conductor,

Claims (6)

[Claims] A bushing having a main circuit terminal connected to a power line at one end and a current conducting path inside; a bushing provided at the other end of the bushing for detecting a current flowing through the current conducting path; A current detecting means connected to the current conducting path, and a current interrupting means for interrupting a current flowing through the current conducting path when a current value detected by the current detecting means exceeds a predetermined value. Around the bushing, provided between the current detection means and the main circuit terminal at a position close to the current detection means,
A circuit breaker comprising external flash ground fault current bypass means for bypassing an external flash ground fault current flowing from the main circuit terminal through the space outside the bushing to a ground line. 2. An external flash ground fault current bypass means is provided around the bushing, between the current detection means and the main circuit terminal, at a position close to the current detection means, and has an inner diameter larger than the maximum outer diameter of the bushing. The circuit breaker according to claim 1, further comprising: a shield ring having: a grounding means for grounding the shield ring. 3. The shut-off according to claim 2, wherein the grounding means comprises a conductive wire connected to the ground or a grounded object connected to the ground via the outside of the current detecting means through the shield ring. vessel. 4. The circuit breaker according to claim 2, wherein the shield ring is held by insulating means provided on a surface of the current detecting means. 5. The circuit breaker according to claim 4, wherein the insulating means has an axial adjusting mechanism for moving the position of the shield ring at least in the axial direction with respect to the center axis of the bushing. 6. The circuit breaker according to claim 4, wherein the insulating means has a lateral adjustment mechanism for moving the position of the shield ring with respect to the center axis of the bushing in a direction perpendicular to the axis.