JPH048595Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention consists of a plurality of contact pieces that surround a rod-shaped movable contact that advances and retreats in a straight line and that come into contact with and leave the circumferential surface of the contact piece, and A pedestal supported on the periphery, and an opening fixed to the pedestal that surrounds the contact piece from the outside and surrounds the outer peripheral surface of the movable contact through a ring-shaped interval to allow the contact to enter and exit. The fixed contact and the movable contact each having a bowl-shaped electrostatic shield correspond to three phases,
A fixed contact for improving insulation performance when interrupting loop current in a three-phase bulk gas switch that is housed in a common metal container and interrupts loop current and interrupts small currents such as transformer excitation current. Concerning child structure.

[Prior art and its problems]

Generally, in high-voltage substations, as shown in the single-line diagram in Figure 4, a double busbar is formed by two sets of busbars 31 and 32 running in parallel, and a busbar connection breaker is installed between them. 33. Load switch with disconnect function (herein simply referred to as switch) 34, 35,
36, 37, and circuit breakers 38, 39. 4
0 is a transformer, and 41 is a power transmission line. Now transformer 4
0 is receiving power from the power transmission line 41 via the switch 34, the bus bar 31, the switch 36, and the circuit breaker 39, and the switches 35 and 37 are assumed to be open. If this power is to be received via the busbar 32 for operational reasons at the substation, the switch 35 is first turned on, and then the switch 34 is opened. When the switch 35 is closed, the current from the power transmission line 41 is divided into both switches, but the shunt current flowing through the switch 34 is commutated to the switch 35 when the switch 34 is opened. This commutation phenomenon is equivalent to forcing a current of the same magnitude and opposite direction as the shunt current of the switch 34 to flow along the loop 42. The voltage required for this forced flow is equal to the product of the impedance of the loop 42 and the shunt current flowing through the switch 34, and this voltage appears across its breaking contacts as a recovery voltage after the switch 34 is opened.
Next, the commutation phenomenon when the switch 37 is closed and the switch 36 is opened is similar to that of the switch 3 along the loop 43.
6 is equivalent to passing a current of the same magnitude as the shunt current in the opposite direction. is equal to the product of In addition, in the power transmission line, for example, as shown in Fig. 5, among the two parallel lines running between the bus 44 of the upper substation and the bus 45 of the lower substation, one line 46 through which current flows is connected. When transferring a current to another line 47 in which no current is flowing, the current is once divided into two lines, and then a current of the same magnitude and opposite direction as the branched current of the first line is passed along the loop 48. By distributing the
The result is the same as when the switching device 49 interrupts the loop current equal to the shunt current, and the power transmission line is switched.

This type of loop current interruption differs from normal short-circuit current interruption in that the interruption current is small and the recovery voltage is low. , both load sides have a potential equal to the phase voltage with respect to the ground, and a line voltage is applied between the interrupting parts of each phase. This invention interrupts the loop current under such voltage application conditions, and during interruption, interruption and re-ignition are repeated in small increments, and each time a high transient recovery voltage is applied between the interruption contacts. However, the final cutoff was reached,
After this final disconnection, the recovery voltage that appears between the disconnection contacts transitions from a transient recovery voltage to a steady recovery voltage.A three-phase interrupter is housed in a common grounded metal enclosure for interrupting small currents such as transformer excitation currents. The present invention relates to a fixed contact structure of a three-phase lumped switch which does not cause a drop in withstand voltage between phases and between a phase and a container when switching the loop current as described above, and which has a conventional structure. An example is shown in FIG.

As shown in the figure, the fixed contact 2 includes a rod-shaped movable contact 3 that moves linearly forward and backward, and a contact piece 6 that contacts the circumferential surface of the movable contact at a position indicated by a chain line.
, a pedestal 5 that supports the contact piece 6 fixed to the main circuit conductor 1 on the circumference, and this pedestal 5 and the movable contact 3
a garter spring 9 that applies contact pressure to the contact piece bridging the contact piece; The main component is a bowl-shaped electrostatic shield 10 with an opening 10a for entering and exiting the movable contact 3, and when the current is cut off, the movable contact 3 is driven linearly downward in the figure and movable with the contact piece 6. An arc 12a is generated between the contactor 3 and the contactor 3. This arc comes into contact with the inside of the opening 10a of the electrostatic shield under the influence of thermal expansion of the arc extinguishing medium around the arc, and after contact, current flows through the electrostatic shield through a shorter arc path. In this way, the arc foot point is dislocated to the electrostatic shield and approaches the adjacent phase, which makes the arc susceptible to the electromagnetic force due to the arc current of the adjacent phase, and the arc becomes elongated as shown in 12b. It becomes easier to bend. Once curved, the arc generates an electromagnetic force F that tends to further curve itself, so the arc begins to extend in a direction perpendicular to the moving direction of the movable contact 3. Therefore, depending on the breaking conditions (breaking current, breaking speed of the movable contact, etc.), the arc 12b may well extend outside the diameter range of the electrostatic shield 10.
In a three-phase bulk switch arranged in a common metal container 20 as shown in the figure, a short circuit between phases (for example, S-T
These disadvantages include the risk of phase short circuits) and ground faults (for example, R-phase ground faults). In addition, if the arc foot point stays in the electrostatic shield for a long time, vapor from the metal material forming the electrostatic shield will be abundantly supplied around the arc, which will only worsen the decline in dielectric strength between phases and ground. However, due to the generation of this metal vapor, the arc voltage between the contact pieces does not increase and the current interrupting performance also deteriorates.

[Purpose of invention]

This invention is a three-phase parallel type gas switch with no arc extinguishing chamber, in which fixed contacts and movable contacts for three phases are housed in a common metal container, and the loop current is interrupted. The purpose of the present invention is to provide a gas switch that has improved dielectric strength between phases and to ground when loop current is interrupted, without increasing the interphase dimensions or the dimensions of the container, in those that interrupt small currents such as transformer excitation current. shall be.

[Key points of the idea]

This idea is based on the idea that when the loop current is interrupted in a parallel cut-off section that does not have an arc extinguishing chamber, the value of the arc voltage just before the current zero value is the peak value of the excessive recovery voltage that appears between the contacts immediately after the current interruption. The current is finally cut off when the current reaches a certain percentage, for example, about 1/3, and the conditions for normal loop current cutoff (current value is 2000 A or less, transient recovery voltage peak value is 700 V)
(below), if the arc length in the axial direction that curves due to the electromagnetic force from the adjacent phase is less than 1/2 of the arc length required for current interruption, there will be no substantial deterioration in the insulation between the phases and the ground (70KV). Based on test results for standard equipment, at least 1/2 or more of the arc length required for current interruption exists between the contact piece and the electrostatic shield opening, and the arc length that exists outside the opening is reduced to 1/2. By doing the following, the purpose is to ensure the dielectric strength between the phases and to ground when the loop current is interrupted without increasing the dimensions between the phases of the three-phase contactor or the size of the container. The axial distance between the electrostatic shield opening side end face and the opening is set to at least 1/2 or more of the arc length required to interrupt the loop current, and within this set interval dimension, a U-shaped cross section is set. An annular insulator formed in the U-shape with the open side of the U-shape facing the axis side is disposed to prevent the arc existing within this interval from contacting the inside of the electrostatic shield, and to has an inner diameter that allows the movable contact to pass almost tightly, and not only has a recovery voltage when the loop current is interrupted (for example, the peak value is 700V), but also a recovery voltage when a small current is interrupted, which is the other responsibility of the switch. (For example, the ring-shaped interval g (Fig. 6) of the opening is set to such a size that an insulating layer with a thickness that can withstand a wave height of 100 KV is formed. By extending one side of the electrostatic shield to the outside of the electrostatic shield while closely covering the opening and forming an insulating layer having the dimensions described above, when the movable contact escapes from the opening, the electrostatic shield is removed. The opening stroke of the movable contact is continued until the arc length reaches an arc length that can interrupt the current while withstanding all the voltages that may be applied between the openings. The purpose is to achieve the above objective by setting the arc length to 1/2 or less of the total arc length.

[Example of idea]

FIG. 1 shows a first embodiment of the present invention. The electrostatic shield 23 of the fixed contact 22 is formed long in the axial direction, and between the opening 23a and the contact piece 6,
At least 1/ of the arc length required to interrupt the loop current
A space with an interval dimension L ₁ equal to 2 is formed,
Here, an annular insulator 13 having a U-shaped cross section with the open side of the U shape facing the axis is disposed, and a ring between the opening 23a and the outer peripheral surface of the movable contact 3 is disposed. The size of the space h is determined to have an inner diameter that allows the movable contact 3 to pass almost densely in this opening, and to accommodate not only the loop current but also the recovery voltage applied between the movable contact and the electrostatic shield 23 when a small current is interrupted. The opening 23a is tightly covered with one side of the U-shape shown by the cross section of the insulator 13, and an insulating layer having the above-mentioned dimensions is formed. It is made to extend to the outside of the electrostatic shield 23 while being formed.

When the loop current is interrupted, the contact piece 6 and the movable contact 3
The arc generated between
increases in length as it is pushed into the annular space formed by the The axial dimension _L1 of the space between the contact piece 6 and the opening 23a, in which the annular insulator 13 is arranged, is set to at least 1/2 of the arc length required to interrupt the loop current. from,
Arc length outside the opening just before current interruption
L ₂ is less than 1/2 of the total arc length, and the electromagnetic force received from the adjacent phase is also reduced correspondingly to this arc length, and the degree of arc curvature is also reduced. Interruption becomes possible. Note that the movable contact 3 is located in the opening 23a.
An arc voltage is applied between the movable contact and the electrostatic shield until it escapes, but the opening of the electrostatic shield is tightly covered by the extension 13a of the annular insulator. , and the thickness of the insulating layer at this extended part is thick enough to withstand the recovery voltage when a small current is interrupted, so it can easily withstand this arc voltage and the arc will not be short-circuited in the middle and will reach the final stage. Extended to arc length.

2 and 3 show a second embodiment of the annular insulator structure of the present invention. Here, FIG. 2 is a front sectional view, and FIG. 3 is a plan sectional view taken along the line QQ in FIG. In this structure, whereas the insulator shown in the embodiment of FIG. 1 forms a simple annular space, this space is divided into a plurality of small spaces A arranged in the circumferential direction by partition plates 14 arranged radially. It is divided into. When the arc is pulled toward one of the small spaces due to uneven thermal expansion around the arc, the gas pressure in this small space increases due to the arc heat, and this pressure pushes the arc back to the center. It can be done. In this way, the arc can approach a small space,
Repeat the rebound movement. On the other hand, the annular insulator 13 and the partition plate 14 are usually formed using a resin such as tetrafluoroethylene resin, which does not form a conductive layer on the surface due to arc heat. The surface tissue decomposes and generates gas. Therefore, when the movable contact completes its opening stroke and escapes from the opening, the decomposed gas generated from the inner surface of the annular insulator and the partition plate is released in the axial direction.
It flows axially around the arc extending out of the opening to hold the arc on its axis. Moreover, as mentioned above, a large amount of gas is generated due to the repeated approach and repulsion of the arc to the annular insulator divided into small spaces, so the arc cannot be held securely on the axis. In addition, this gas generation is distributed almost evenly over all small spaces, which increases the life of the annular insulator and provides long-term dielectric strength, especially for gas switchgears that require frequent switching. A suitable means for ensuring this can be provided.

[Effect of idea]

As described above, according to the present invention, the contact piece of the fixed contact, the contact piece is surrounded from the outside, and the outer circumferential surface of the rod-shaped movable contact is surrounded through a ring-shaped interval. The distance between the opening of the electrostatic shield, which has an opening for entering and exiting the electrostatic shield, is set to a dimension that provides at least 1/2 or more of the arc voltage required to interrupt the loop current, and the distance between the opening and An annular insulator having a U-shaped cross section with the open side of the U-shaped facing toward the axis is arranged in a space located in the space, and one side of the U-shape is tightly covering the opening. By forming an insulating layer thick enough to withstand high recovery voltage when interrupting a small current and extending it to the outside of the electrostatic shield, the arc can be extended to the final current interrupting position without being short-circuited midway. At the same time, the arc length outside the opening at this position is shortened to less than 1/2 of the total arc length, so it is less susceptible to electromagnetic force due to the arc current of the adjacent phase, and bending is less likely to occur. This also has the effect of ensuring dielectric strength to ground without increasing the interphase dimensions of the three-phase contactor or the size of the container.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of the gas switch interrupting section for explaining the structure of the fixed contact according to the present invention and the distribution of arc length when loop current is interrupted, and Figs.
The figures show a second embodiment of the annular insulator shown in FIG. 1, FIG. 2 is a front sectional view, and FIG. 3 is a plan sectional view taken along the line Q--Q in FIG. Figure 4 is a single-line diagram to explain the responsibilities of a switch when switching a substation busbar, Figure 5 is a single-line diagram to explain the responsibilities of a switch when switching a power transmission line, and Figure 6 is a single-line diagram to explain the responsibilities of a switch when switching a power transmission line. The figure shows an example of the structure of a conventional gas switch and a vertical cross-sectional view of the gas switch interrupting section to explain the arc path when interrupting a loop current using this structure. Figure 7 shows a three-phase contact FIG. 2 is a cross-sectional view of the interrupting portion for explaining the influence of arc on the interphase and ground dielectric strength when loop current is interrupted in a conventional three-phase bulk gas switch in which the three-phase gas switch is housed in a common metal container. 2, 22... Fixed contact, 3... Movable contact,
5... Pedestal, 6... Contact piece, 10, 23... Electrostatic shield, 12, 12a, 12b, 12r, 12
s, 12t...Arc, 13...Annular insulator, 1
4...Insulating partition plate, 20...Metal container, 34,3
5, 36, 37, 49, 50... Switch, A...
Small space, g, h...ring spacing.

Claims (1)

[Claims for Utility Model Registration] 1. A plurality of contact pieces that surround a rod-shaped movable contact that advances and retreats in a straight line and move toward and away from the circumferential surface of the contact piece, a pedestal that supports the contact pieces on the circumference, a bowl-shaped electrostatic shield that is fixed to a pedestal, surrounds the contact piece from the outside, surrounds the outer peripheral surface of the movable contact through a ring-shaped interval, and has an opening through which the contact enters and exits. A three-phase all-in-one type gas switch in which the fixed contact and the movable contact for three phases are housed in a common metal container to interrupt loop current and interrupt small current such as transformer excitation current. , the axial distance between the electrostatic shield opening side end surface of the contact piece and the opening is set to be at least 1/2 or more of the arc length required to interrupt the loop current, and this setting An annular insulator having a U-shaped cross section with the open side of the U shape facing the axis is disposed within the interval dimension, and an inner diameter that allows the movable contact to pass through the opening almost tightly. The ring-shaped spacing of the openings is set so that an insulating layer having a thickness that can withstand the recovery voltage when the small current is cut off is formed, and one side of the U shape indicated by the cross section of the annular insulator is A gas switch characterized in that an insulating layer having the dimensions described above is formed to tightly cover the opening and extend to the outside of the electrostatic shield. 2 Utility Model Registration In the gas switch according to claim 1, the annular insulator disposed between the contact piece of the fixed contact and the electrostatic shield opening is arranged radially so that the insulator is A gas switch characterized by comprising an insulating partition plate that partitions a formed annular space into a plurality of small spaces in the circumferential direction.