US3584171A

US3584171A - Electric circuit breaker of minimum liquid type

Info

Publication number: US3584171A
Application number: US787183A
Authority: US
Inventors: Walter Pucher
Original assignee: ASEA AB
Current assignee: ABB Norden Holding AB
Priority date: 1967-12-29
Filing date: 1968-12-26
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08
Also published as: GB1242860A; SE336160B; FR1598884A; DE6812479U; CH488276A

Abstract

A high-voltage circuit breaker of the minimum liquid type includes an elongated extinguishing chamber with a central, longitudinal arc channel for the movable contact. A plurality of outlet channels lead from a pressure accumulating space having a closed gas-filled space to an exhaust channel. The outlet channels cross the arc channel and are released by the movable contact when the circuit breaker opens. The pressure accumulating space and the exhaust channel extend along the arc channel at substantially the same distance from the latter.

Description

United States Patent I I I Inventor Walter Pucher Ludvika, Sweden Appl. No. 787,183 Filed Dec. 26, 1968 Patented June 8, 1971 Assignee Vasteras, Sweden Priority Dec. 29, 1967 Sweden 17976/67 Allmannn Svenska Elektrlska Aktiebolaget ELECTRIC CIRCUIT BREAKER OF MINIMUM LIQUID TYPE 9 Claims, 4 Drawing Figs.

U.S. Cl.

Int Cl Field of Search 200/150B l-l0lh 33/68 [56] References Cited FOREIGN PATENTS 230,991 1/l964 Austria 200/ 1 50B 1,203,659 8/1959 France 200/150RD 1,127,443 4/1962 Germany ZOO/150B Primary ExaminerRobert S. Macon Attorney-Jennings Bailey, .Ir.

PATENTED JUN 8197i INVENTOR.

WALTER PUCHER a I, M

ELECTRIC CIRCUIT BREAKER OF MINIMUM LIQUID TYPE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electric circuit breakers of the minimum liquid type andthe object of the invention is to effect a liquid circuit breaker having high breaking capacity at voltages up to about 25 kilovolts and which is at the same time cheap to manufacture and requires little space.

2. The Prior Art The invention is based on a previously known type of liquid circuit breaker consisting of an extinguishing chamber immersed in a liquid, in which is arranged a pressure accumulating chamber partly filled with liquid and containing a gasfilled, closed, annular space above the liquid surface. The movable contactof the breaker is moved into the extinguishing chamber from its lower side and is displaceable in an arc channel arranged through the extinguishing chamber to engage a stationary contact arranged at the upper end of the arc channel. A number of outlet openings arranged perpendicular to the arc channel lead from the pressure accumulating chamber and open out directly into the liquid-filled space surrounding the extinguishing chamber. During a breaking operation the outlet channels of the movable contact are opened so that the arc gases efi'ect a pressure increase in the gas-filled space of the pressure accumulating chamber. When the breaking current approaches zero, the pressure in the arc channel decreases so that a powerful flow of gas and oil is pressed against the arc and an extinguishing effort is initiated. This known type of extinguishing chamber, usually called a reaction chamber, has the advantage compared with the normal chambers of the cross-blowing type that the gas-filled space prevents the occurrence of extremely high pressure in the chamber and also provides effective rinsing of the arc channel directly after the breaking. Since the pressure stresses on the chamber are reduced to a reasonable value this can be produced more'cheaply and, by means of the powerful liquid flow which is obtained from the pressure accumulating chamber to the arc channel when the gas in the pressure accumulating chamber expands, a rapid increase in the voltage strength is obtained between the contacts, and thus a higher breaking capacity. The downward movement of the contact when the breaker opens has the advantage that the movable contact with the required sliding or roller contacts can be completely immersed in oil, which improves the cooling of these parts and makes smaller dimensions of the contacts possible, and thus also of the surrounding extinguishing chamber. In spite of this, however, the known circuit breaker is relatively space-consuming, mainly because the inside of the extinguishing chamber is designed in such a way with respect to, among other things, removal of the breaking gases, that the extinguishing chamber must be arranged inside an outer container filled with liquid. This is a big disadvantage, particularly with breakers to be erected indoors since the question of space is then of particular importance. It is also desirable in circuit breakers of this type to be able to decrease the necessary quantity of liquid as far as possible, particularly if inflammable liquid is used.

SUMMARY OF THE INVENTION The minimum liquid circuit breaker according to the invention comprises, as does the above-described known circuit breaker, an elongated, substantially vertical and preferably cylindrical extinguishing chamber, an arc channel running in the longitudinal direction of said chamber, a movable contact displaceable through said channel to engage a stationary contact in the upper end of the channel, at least one pressure accumulating space arranged in said extinguishing chamber, said pressure accumulating space being partly filled with liquid and containing a closed gas-filled space, at least one outlet channel from said pressure accumulating space crossing said are channel, said outlet channel being released by the movable contact when the circuit breaker opens. The circuit breaker is characterized in that said outlet channels open into at least one exhaust channel arranged inside said extinguishing chamber and leading into an expansion chamber arranged above the extinguishing chamber, said expansion chamber being partly filled with gas, said pressure accumulating space and said exhaust channel extending along said are channel at substantially the same distance from the arc channel. A circuit breaker constructed in this manner is very much smaller, particularly with respect to the pole diameter and thus the costs of the circuit breaker are lower. The smaller dimensions also result in indirect savings, particularly with indoor plants, since the space required for the circuit breaker is less.

In the previously known circuit breaker described above the uppermost of said outlet channels from the pressure accumulating chamber is arranged at a certain distance from the stationary contact so that the arc is extended to a certain length before the extinguishing process is initiated. At the voltages for which the circuit breaker according to the present invention is primarily intended, however, it has been found advantageous to attack the are as soon as it forms and the uppermost of said outlet channels is therefore suitably arranged immediately below the stationary contact. This has the additional advantage that the length of the chamber is considerably reduced. A circuit breaker constructed according to this method has, in breaking tests with voltages up to 20 kv, shown extremely short arcing times and little contact wear.

In order to increase the creep path between the openings of the various outlet channels in the exhaust channel and thus prevent reignition of the arc in this channel, it is suitable, particularly with high voltages, to arrange the outlet channels adjacent to each other so that the openings are displaced for example or in relation to each other around the central axis of the extinguishing chamber. It may be advantageous to arrange several exhaust channels separated from each other and possibly even several pressure accumulating spaces.

Available space is particularly well utilized if the pressure accumulating space and the exhaust channel have cross sections in the shape of ring sectors. They may also be arranged to become narrower in the downward direction to effect a favorable flow in the chamber.

With a circuit breaker according to the present invention where the extinguishing is effected by a liquid flow directed perpendicular to the arc, it is suitable for the part of the stationary contact situated nearest the exhaust channel to be formed as an arc contact, so that it extends further down than the rest of the contact. The arc is thus under better control and its upper end is more effectively cooled. Also, burn marks are prevented from occurring on that part of the contact surface of the stationary contact through which the current passes when the circuit breaker is closed.

At low currents the gas pressure in the pressure accumulating space may not be sufficiently high for the first extinguishing attempt to succeed. in order to facilitate the breaking in such cases, at least one liquid-filled space is suitably arranged below the outlet channels and surrounding the arc channel. The liquid-filled space communicates freely with the arc channel. Breaking of small currents can be further facilitated by utilizing the contact movement to pump liquid into the arc channel.

BRIEF DESCRIPTION OF THE DRAWING The invention will be further described with reference to the accompanying drawings in which FIG. 1 shows schematically by way of example a longitudinal section through a minimum liquid circuit breaker according to the invention and FIGS. 2, 3 and 4 show the same circuit breaker in cross section along the lines A-A, 8-H and C-C in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The circuit breaker shown in the drawings consists of a cylindrical extinguishing chamber 1 of insulating material having a metallic lid 2 arranged at its upper end which is electrically connected with the stationary contact 3 of the breaker. The movable contact 4 consists of a solid contact plug which is displaceable through an arc channel 5 arranged centrally in the extinguishing chamber, to engage the stationary contact 3 arranged at the upper end of the channel. The circuit breaker is filled with liquid, for example oil, to a level in the lower part of the lid 2. The lid 2 thus limits an expansion space 6 which is in communication with the open air through an opening 7. A so-called oil separator may suitably be arranged in this opening which prevents the liquid from being forced out of the circuit breaker when the liquid is set in motion during a breaking operation. Inside the extinguishing chamber is a pressure accumulating space 8 which is only partly filled with liquid so that a closed gas-filled space 9 is formed above the liquid surface. An oil level opening 10 is arranged in the pressure accumulating space 8 so that after each breaking operation the oil will return to the same level as before the breaking.

Three outlet channels 11 cross the arc channel 5 from the pressure accumulating space 8 and open into an exhaust channel 12. This exhaust channel 12 leads in turn up to the expansion chamber 6 in the lid 2. As is clear from F I05. 2 and 3, the pressure accumulating space 8 and the exhaust channel 12 have ring sector shaped cross sections and become narrower in downward direction.

The stationary contact 3 is constructed as a tulip contact, the part 13 situated nearest the exhaust channel 12 forming an arc contact which extends further down than the rest of the contact. The contact separation will therefore always take place at a distance from that part of the contact surface of the stationary contact through which the current passes when the circuit breaker is closed, and this part of the contact surface is thus not damaged by the arc.

In order to effect the breaking of small currents two liquid pockets 14 are arranged in the lower part of the extinguishing chamber. The movement of the contact is also utilized when the circuit breaker opens to pump liquid into the arc channel 5 through special holes 15 which form a connection channel from the lower part of the circuit breaker to the pressure accumulating space 8.

The circuit breaker operates in the following manner: When the movable contact 4 leaves the arc contact 13 an arc is formed which causes strong vaporization of the oil. The gases force away the oil in the accumulating space 8 and the gas pocket'9 is compressed. When the current wave approaches zero the pressure decreases very rapidly in the arc channel 5 and a powerful liquid flow is forced from the pressure accumulating space 8 through the outlet channels 11 and the exhaust channel 12 to the expansion space 6. The are path is thus rapidly de-ionized and the dielectric strength between the contacts is quickly restored so that reignition of the arc is prevented. Metal and carbon particles are simultaneously rinsed away from the important parts of the chamber.

The invention is not limited to the embodiment shown. Several modifications are feasible within the scope of the following claims. The arc channel 5 may, for example, be arranged eccentrically in the extinguishing chamber 1, so that the pressure accumulating space 8 and the exhaust channel l2 chamber and the insulator porcelain may be filled with liquid.

lclaim: 1. Electric circuit breaker of the minimum liquid type having an elongated, substantially vertical extinguishing chamber an arc channel running in t e longitudina direction of sat chamber, a stationary contact in the upper end of the channel, a movable contact displaceable through said channel to engage said stationary contact, at least one pressure accumulating space in said extinguishing chamber, said pressure accumulating space being partly filled with liquid and including a closed gas-filled space, a plurality of outlet channels from said pressure accumulating space crossing said are channel, the uppermost of said outlet channels being arranged immediately below the stationary contact, said outlet channels being uncovered by the movable contact when the circuit breaker opens, in which the invention comprises at least one exhaust channel arranged inside said extinguishing chamber and an expansion chamber arranged above the extinguishing chamber, said outlet channels opening into said exhaust channel and said exhaust channel leading to said expansion chamber, said expansion chamber being partly filled with gas, said pressure accumulating space and said exhaust channel extending along in the direction of said are channel at substantially the same distance therefrom, at least one liquid-filled space below the outlet channels, said liquid-filled space surrounding the arc channel and being in free communication therewith.

2. Electric circuit breaker according to claim 1, in which the pressure accumulating space and exhaust channel are arranged on diametrically opposite sides of the arc channel.

3. Electric circuit breaker according to claim 1, in which the pressure accumulating space and exhaust channel have cross sections in the shape of ring sectors.

4. Electric circuit breaker according to claim 1, in which the pressure accumulating space and exhaust channel become narrower in the downward direction.

5. Electric circuit breaker according to claim 1, in which the part of the stationary contact situated nearest the exhaust channel extends further down-than the rest of the contact.

6. Electric circuit breaker according to claim 1, in which the movable contact has means cooperating therewith forming a pump arrangement to pump liquid into the arc channel when the breaker opens.

7. Electric circuit breaker according to claim 6, in which said cooperating means comprises a connecting channel for liquid flow from the lower part of the breaker to the pressure accumulating space.

8. Electric circuit breaker according to claim 1, in which the expansion chamber is arranged in association with the upper end of the extinguishing chamber and has the same central axis and substantially the same diameter as the extinguishing chamber.

9. Electric circuit breaker according to claim 1, in which openings from adjacent outlet channels into the exhaust channel are displaced in relation to each other around the central axis of the extinguishing chamber.

Claims

1. Electric circuit breaker of the minimum liquid type having an elongated, substantially vertical extinguishing chamber, an arc channel running in the longitudinal direction of said chamber, a stationary contact in the upper end of the channel, a movable contact displaceable through said channel to engage said stationary contact, at least one pressure accumulating space in said extinguishing chamber, said pressure accumulating space being partly filled with liquid and including a closed gas-filled space, a plurality of outlet channels from said pressure accumulating space crossing said arc channel, the uppermost of said outlet channels being arranged immediately below the stationary contact, said outlet channels being uncovered by the movable contact when the circuit breaker opens, in which the invention comprises at least one exhaust channel arranged inside said extinguishing chamber and an expansion chamber arranged above the extinguishing chamber, said outlet channels opening into said exhaust channel and said exhaust channel leading to said expansion chamber, said expansion chamber being partly filled with gas, said pressure accumulating space and said exhaust channel extending along in the direction of said arc channel at substantially the same distance therefrom, at least one liquid-filled space below the outlet channels, said liquidfilled space surrounding the arc channel and being in free communication therewith.

5. Electric circuit breaker according to claim 1, in which the part of the stationary contact situated nearest the exhaust channel extends further down than the rest of the contact.