US3832502A

US3832502A - Electric circuit breaker with hydraulic actuating means including a plurality of valves for opening the breaker,and a plurality of valves for closing the breaker

Info

Publication number: US3832502A
Application number: US00257151A
Authority: US
Inventors: G Grieger; J Bohrdt
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1971-06-04
Filing date: 1972-05-26
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: JPS5328622B1; CH539940A; DE2128648B2; FR2139894A1; FR2139894B1; DE2128648A1

Abstract

AN ELECTRIC CIRCUIT BREAKER IS DISCLOSED HAVING A BLAST PISTON FOR COMPRESSING A GASEOUS QUENCHING MEDIUM SUCH AS SULFUR HEXAFLOURIDE, AND A HYDRAULIC DRIVE FOR THE BREAKER WHICH INCLUDES A MAIN HYDRAULIC ACTUATOR CYLINDER AND PISTON AND VALVES FOR CONTROLLING THE ADMISSION OF HYDRAULIC FLUID INTO THE CYLINDER. IN ADDITION, FOR CLOSING THE CIRCUIT BREAKER A HYDRAULIC LATCHING ARRANGEMENT IS DISCLOSED WHICH IS ASSOCIATED WITH THE VALVE CLOSEST TO THE MAIN ACTUATOR CYLINDER IN AN APPLICATION WHERE THERE ARE MORE THAN TWO SERIES-CONNECTED VALVES FOR CLOSING THE BREAKER. FOR OPENING THE BREAKER, A HYDRAULIC LATCHING ARRANGEMENT IS DISCLOSED WHICH IS ASSOCIATED WITH A VALVE WHICH IS SEPARATED FROM THE MAIN ACTUATOR CYLINDER BY AT LEAST ONE FURTHER VALVE.

D R A W I N G

Description

United States Patent 1191 Grieger et a1.

1451 Aug; 27115174" x 122 Filed:

[ 1 ELECTRIC CIRCUIT BREAKER WITH HYDRAULIC ACTUATING MEANS INCLUDING A PLURALITY OF VALVES FOR OPENING THE BREAKER, AND A PLURALITY OF VALVES FOR CLOSING THE BREAKER 175] Inventors: Gerhard Grieger; Joaquin Bohrdt,

both of Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Munich.

Germany May 26, 1972 211 Appl. No.: 257,151

[30] Foreign Application Priority Data June 4. 1971 Germany ..2128648 [52] US. Cl. 200/82 B, 200/148 A, 251/634 [51] Int. CL. H0lh 35/38, HOlh 33/34, H0lh 33/88 [58] Field of Search 200/82 AB, 82 R, 148 A,

FOREIGN PATENTS OR APPLICATIONS 4.519.250 1/1967 .lapan 200/82 1,203,632 1/1960 France 200/82 R Primary Examiner-Robert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney, Agent, or Firm-Hugh A. Chapin 5 7 ABSTRACT An electric circuit breaker is disclosed having a blast piston for compressing a gaseous quenching medium such as sulfur hexaflouride, and a hydraulic drive for the breaker which includes a main hydraulic actuator cylinder and piston and valves for controlling the admission of hydraulic fluid into the cylinder. In addition, for closing the circuit breaker a hydraulic latching arrangement is discosed which is associated with the valve closest to the main actuator cylinder in an application where there are more than two seriesconnected valves for closing the breaker. For opening the breaker, a hydraulic latching arrangement is disclosed which is associated with a valve which is separated from the main actuator cylinder by at least one further valve.

12 Claims, 1 Drawing Figure ELECTRIC CIRCUIT BREAKER WITH HYDRAULIC ACTUATING MEANS INCLUDING A PLURALITY OF VALVES FOR OPENING THE BREAKER, AND A PLURALITY OF VALVES FOR CLOSING THE BREAKER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an electric circuit breaker and more particularly, to a high-voltage power circuit breaker wherein a hydraulic drive and a hydraulic latching arrangement are provided for the breaker, and wherein a blast piston is provided for compressing an arc-quenching medium (such as sulfur hexaflouride gas), in which circumstances special problems are presented due to the large driving forces and compression employed.

2. Description of the Prior Art As illustrated by West German Pat. No. 1,225,497 an electric circuit breaker having a hydraulic drive is known wherein the actuator cylinder of the hydraulic drive is associated with a hydraulically operated main valve and two magnetically operated servo valves. In the past, for closing the circuit breaker, one of the servo valves is opened, and a piston thereby acted upon by the hydraulic fluid then opens the main valve. Subsequently, the main valve is kept under pressure when said servo valve closes, as through a branch line equipped with a choke off the hydraulic line leading to the cylinder, and a pressure line in parallel with the servo valve is provided. The choke permits the main valve to be reversed by the other servo valve for opening the circuit breaker without an unnecessarily large loss of oil. In such a circuit breaker the discharge crosssection of the servo valve through which the piston is relieved for the operation of the valve, must be larger than the cross-section constricted by the choke through which the hydraulic fluid can flow into the piston.

In known circuit breakers of the type described, due to the large actuating forces required for the circuit breaker and the small control forces, more servo action is sometimes needed than is attainable with two servo valves. In such a circumstance the known drive is not only no longer usable but there is also a danger that the known circuit breaker will not reliably perform its important circuit-opening operation. Thus, the servo valve for the opening of the breaker may close again after a short open period. and the hydraulic line provided for latching the breaker upon opening may refill the cylinder having the valve-actuating piston. In such a circumstance the circuit breaker may then either remain closed or remain in an intermediate position following a brief movement in the opening direction.

SUMMARY OF THE INVENTION It is an object of this invention to provide a reliable circuit breaker.

It is another object of this invention to provide an electric circuit breaker with reliable latching means.

It is a further object of this invention to provide an electric circuit breaker suitable for use for high-voltage power circuits with a blast piston for compressing a gaseous quenching medium. Other objects of this invention are referred to below.

With a circuit breaker according to this invention having more than two series-connected valves for closthe closing is associated with the valve closest to the main hydraulic actuator cylinder, and a hydraulic latching arrangement for the opening is associated with a valve which is separated from the cylinder by at least one further valve.

With a circuit breaker according to this invention, it has been found that the desired latching is achieved without impairment of the reliability of the circuit breaker, even where there is a large ratio between the actuating and control forces of the circuit breaker. Due to the fact that the latching for the closing of the breaker is assigned to the last valve ahead of the main actuator cylinder, only the opening of that valve which actually acts upon the drive supplies the hydraulic fluid used for the latching arrangement. Also, it is always possible to open the circuit breaker without having to transmit a long command. Further, by arranging the hydraulic line for latching when opening at least one further valve ahead of the cylinder in the series of opening valves, the hydraulic system inherently provides priority for the opening operation. In other known circuit breakers such priority is provided by additional means, particularly additional electrical means.

The hydraulic drive of the circuit breaker according to the invention can also be entrusted with a task which heretofore was accomplished by electrical interlock devices. Thus, according to a further aspect of the invention, the valve series provided for the opening is connected to the hydraulic line used for the latching arrangement for the closing. In this manner an opening command can be transmitted hydraulically only if the circuit breaker is actually closed.

According to another feature of this invention, the valve preceding the valve with the latching arrangement for closing can be shut off by a check valve,

thereby permitting the preceding valve to close without causing oil losses due to the pressure in the latching line.

According to a still further feature of this invention, in the preferred embodiment of the invention the valve provided with the closing latching arrangement is a two-three-way valve which is associated with the larger piston surface of'a differential piston while the smaller piston surface of the differential piston is continuously acted upon by hydraulic fluid. In this manner, a doubleaeting hydraulic actuator can be operated with a single accumulator without the necessity of special venting for rapid operation. The stroke of the two-three-way valve is preferably larger for the opening of its inlet than for the closing of its outlet, so that unnecessary losses of hydraulic fluid are avoided.

Although the invention is described herein with reference to a particular preferred embodiment, the scope of the claims hereof are'not intended to be limited to the details shown, since various modifications may be made within the range and scope of the accompanying claims.

' DESCRIPTION OF THE DRAWING The accompanying drawing is a schematic representation of a preferred embodiment of a circuit breaker constructed according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, the high-voltage power circuit breaker 1 is operated by a hydraulic actuator 2. As the high-voltage circuit breaker 1 may be designed for a rated voltage of l 10 kilovolts or more, and a flow of sulfur hexafluoride gas (SF,,) for quenching any electrical are formed between the electrical breaker contacts at the moment of switching is provided by means of a blast piston coupled with the movable contact 5, a considerable and reliable driving force must be provided for the device, especially for the opening of the breaker contacts. The hydraulic actuator 2 includes an actuator cylinder 3 with a differential piston 4 contained therein which is coupled by means of an insulating linkage 6 with the movable contact of the circuit breaker.

Hydraulic fluid such as oil for operating the circuit breaker comes from a hydraulic accumulator 10 in which the fluid is kept under a suitable pressure (for instance, 200 atmg) by means of gas in known manner. Connected to the outlet 11 of the hydraulic accumulator is a pressure line 12 which leads directly to a main valve 13 interposed before the main hydraulic actuator 2 for the circuit breaker 1. The main valve 13 has a passage 16 by means of which the portion of the actuator cylinder 3 associated with the smaller piston surface 18 of the differential piston 4 of the hydraulic actuator 2 is continuously acted upon by hydraulic fluid through a hydraulic line 19 extending from the main valve 13.

The larger piston surface 20 of the differential piston 4 within the main hydraulic cylinder 3 is connected through a hydraulic line 21 to a chamber 23 of the main valve 13 which is adapted to be shut off by a valve head 24 from the passage 16 communicating with pressure line 12 and the accumulator 10. This valve head 24 is spring-biased by a spring 25 which resiliently presses the valve head 24 against a valve seat 27. To actuate the valve head 24, a stem 29 is provided which is movably received within a recess 30 in the valve head 24. This stem 29 is an integral extension of the main valves actuator piston 31. The actuator piston 31 is guided within a cylinder 32.

At the portion of the stem 29 extending toward the piston 31, the stem widens and forms a cylindrical valve member 33 which serves as a slider and cooperates with a recess 34 in the cylinder such that the hydraulic connection between chamber 23 and outlet 36 of the main valve can be closed off.

For the hydraulic operation of the hydraulic actuator 22, a series of valves (39, 47, 65) is provided for the opening process and another series of valves (38, 46, 13) is provided for the closing process. the two valve series being to some extent of similar design. For example, the two valve series each include a

servo valve

38, 39 with an associated electro-

magnct

40, 41 for electrical operation thereof. The servo valve 38 for the closing process is connected to the pressure line 12 by means ofa hydraulic line 42, and the servo valve 39 for the opening process is connected by a hydraulic line 43 to a hydraulic line 44 which opens into chamber 23 of the main valve 13.

The two

servo valves

38, 39 are each followed by an associated

control valve

46, 47 which is operated hydraulically. The control valve 46 for the closing process is connected by means of a hydraulic line 50 with the pressure line 12, while the control valve 47 for the opening process is connected by means of a hydraulic line 51 to hydraulic line 43. The

respective actuator pistons

53, 54 of the

control valves

46, 47 are each adapted to be acted upon by hydraulic fluid through their

respective servo valves

38, 39 through respective hydraulic connecting

lines

55, 56. When the

servo valves

38 and 39 are closed, the

actuator pistons

53, 54 of the

control valves

46, 47 are relieved by means of

hydraulic lines

100 and 101 respectively.

From the control valve 46 for the closing process a hydraulic line having a check valve leads to the inlet 61 of the cylinder 32 for the actuating piston 31 of the main valve 13. As shown in the accompanying drawing, this inlet 61 is hydraulically connected with hydraulic line 44 as well as to a valve 65 which is operated by means of a piston 66. Valve 65 connects the part of the cylinder 32 of the main valve associated with the larger area of the main valvcs actuator piston 31 with an oil tank 62.

In the drawing the circuit breaker l is shown in the open position. To close the circuit breaker, electromagnet 40 is energized in a known manner, thereby opening its associated servo valve 38. Hydraulic fluid then flows to the piston 53 of control valve 46 to open the control valve 46, and hydraulic fluid then flows through hydraulic line 50, check valve 60 and the inlet 61 of the main valve to actuate the piston 31 of the main valve 13. The piston 31 of the main valve then moves from right to left with reference to the position of the piston shown in the accompanying drawing. Within the main valve 13, the length of the stem 29 has a predetermined relationship to that of the recess 30 in valve head 24 and to the distance between the valve seat 34 and the slider cylinder 33 such that outlet 36 of the main valve is closed off shortly after the actuator piston 31 moves from right to left. Thereafter, the valve head 24 of the main valve 13 is lifted from the valve seat 27, and the hydraulic fluid present at valve inlet 16 is thereby permitted to flow into a hydraulic line 21 extending to cylinder 3 of the main hydraulic actuator 2 with the result that the circuit breaker closes. Automatic latching is assured when the valve 13 opens by means of a hydraulic line 44 which bypasses the closing control valve 46, with the result that the closed circuit breaker remains in its closed position when the closing electromagnet 40 is de-energized and its associated

valves

38 and 46 close.

To open the circuit breaker 1, servo valve 39 is opened by an energization of electro-magnet 41 in a known manner. With the opening of servo valve 39 hydraulic fluid is permitted to flow through

hydraulic lines

44, 43 and 56 to control valve 47, and from there through hydraulic lines and 71 to valve 65. Through the practically simultaneous opening of control valve 47 and valve 65, inlet 61 of the main valve is hydraulically connected with the oil tank 62. Through suitable dimensioning of the outlet cross-section in relation to hydraulic line 44 which serves as the feed line and in which a choke 103 can be arranged, there is rapid pressure relief of the piston 31 in the main valve with'the result that spring 25 together with the force of the hydraulic fluid acting on the piston closes the main valve at valve seat 27. The large piston surface 20 of the differential piston 4 is then pressure-relieved rapidly and reliably by the opening of outlet 36 into an oil tank. Thereby, the pressure of the hydraulic fluid acting continuously on the small piston surface 18 of the differential piston 4 brings the circuit breaker l reliably into the open position.

From the drawing and the preceding description it will be seen that the hydraulic latching for the closing operation is due to hydraulic line 44, and the latching arrangement is consequently located directly at the main valve 13. On the other hand. the hydraulic latching for the opening operation is provided by

hydraulic lines

51 and 71. It is accordingly possible with the described invention to initiate the opening operation without having to actuate the main valve 13 itself. As a result the closing operation starts only when the closing command is executed with certainty, while the opening command can be given to the drive mechanism even when there is an existing closing command. Therefore, the opening command, which is important for the safety of the circuit breaker. is executed with priority in spite of hydraulic latching for the closing operation. The opening command remains in the latched condition as long as overpressure exists in

hydraulic lines

44, 43, 51 and 56.

It will be noted that in the described embodiment of the invention which has more than two

seriesconnected valves

13, 38, 46 for the closing. the latching arrangement for the closing is associated with the valve 13 closest to the cylinder 3 of the hydraulic actuator 2, and that a hydraulic latching arrangement 71 is also provided for the opening. The latching arrangement for the opening is associated with a valve 47 which is separated by valve 65 from the cylinder 3 of the hydraulic actuator 2. It will also be noted that the valves 39 47, 65 provided for the opening are connected to the hydraulic line 44 which is used for the latching arrangement for the closing.

We claim:

1. In an electric circuit breaker for use with hydraulic fluid and with a blast piston for compressing a gaseous quenching medium. the circuit breaker having a main hydraulic actuator. a plurality of valves for closing the breaker. and a plurality of valves for opening the breaker. the improvement comprising means for hydraulically latching the circuit breaker upon its closing, which means is connected to the one of the valves for closing the breaker which is hydraulically closest to the main hydraulic actuator;

means for hydraulically latching the circuit breaker upon its opening. which means is connected to one of the valves for opening the breaker which is hydraulically separated from the main hydraulic actuator by at least an additional one of the valves for opening the breaker;

an oil tank; and

a main valve having a hydraulic connection to said oil tank and a hydraulic connection to the hydraulic actuator.

2. An electric circuit breaker as in claim 1 wherein the valves for opening are hydraulically connected in series and wherein the valves for closing are hydraulically connected in series.

3. An electric circuit breaker as in claim 1 wherein the means for latching the circuit breaker upon its closing includes a hydraulic line between the main valve and said one of the valves for closing.

4. An electric circuit breaker as in claim 3 wherein the means for latching the circuit breaker upon its opening is connected to said hydraulic line.

5. An electric circuit breaker as in claim 3 wherein said hydraulic line has a check valve therein for shutting off said one of the valves for closing.

6. An electric circuit breaker as in claim 1 wherein S the main valve is a two-three-way valve, and

i the hydraulic actuator includes a differential piston with its larger piston surface having a hydraulic connection to said two-three-way valve, and'its smaller piston surface being continuously acted upon by hydraulic fluid.

7. An electric circuit breaker as in claim 6 further comprising the oil tank being hydraulically connected to an outlet of said two-three-way valve and wherein the stroke of said two-three-way valve for opening its said hydraulic connection to said differential piston is larger than the stroke of said two-three-way valve for closing its said outlet to said oil tank.

8. An electric circuit breaker as in claim 1 wherein two of the valves for opening the breaker are respectively identical to two of the valves for closing the I breaker.

9. In an electric circuit breaker for use with hydraulic fluid and with a blast piston for compressing a gaseous quenching medium, the circuit breaker having a main hydraulic actuator, a plurality of valves for closing the breaker, and a plurality of valves for opening the breaker. the improvement comprising means for hydraulically latching the breaker upon its closing, which means is connected to the one of the valves for closing the breaker which is hydraulically closest to the main hydraulic actuator;

an oil tank; and

a main valve having a hydraulic connection to said oil tank and a hydraulic connection to the hydraulic actuator,

which hydraulic actuator includes a differential piston with its larger piston surface having a hydraulic connection to the main valve and its smaller piston surface being continuously acted upon by the hydraulic fluid. and

which main valve comprises a two-three-way valve in which the stroke of the piston for opening its said hydraulic connection to the differential piston is larger than the stroke of the piston for closing its said hydraulic connection to said oil tank.

10. An electric circuit breaker as in claim 9 wherein said two-three-way valve comprises a spring-biased valve head with a recess therein, said valve head being within a chamber in said twothree-way valve; and

a piston within said two-three-way valve. said piston having a stem portion adapted to be received into the recess in said valve head for moving said valve head in a direction opposite to the spring-bias of said valve head.

11. An electric circuit breaker as in claim 9 which further comprises a moveable contact for opening and closing the circuit in which the breaker is interposed; and

means for linking said piston of said differential piston to said moveable contact. 12. An electric circuit breaker as in claim 9 wherein the valves for closing the breaker and the valves for opening the breaker each include an electromagnetically actuated servo valve.