US3177326A - Pressurized chamber arrangement for oil circuit breakers - Google Patents

Description

April 1965 A. ROXBURGH ETAL PRESSURIZED CHAMBER ARRANGEMENT FOR OIL CIRCUIT BREAKERS Filed July 30, 1962 .2 Sheets-Sheet l IN VENTORS:

A/ber'l Roxb urg/I A/ber'f Le/g/z ,4 TTOR/VE Y April 6, 1965 A. ROXBURGH ETAL PRESSURIZED CHAMBER ARRANGEMENT FOR OIL CIRCUIT BREAKERS .2 Sheets-Sheet 2 Filed July 30, 1962 Irv IN VENTORS:

W 5 M m W am h am www V K A A United States Patet s s Ciairns. (ca. ass-ass This invention relates to circuit breakers, of the small oil-volume kind, and aims at providing an improved con struction which enhances the arc extinguishing effect of the breaker by ensuring a predetermined static high 011 pressure before the contacts separate, which is most important if the current to be interrupted is comparatively low. A means is provided, however, to prevent excessive oil pressure when the arcing current is high, as may be the case when a short-circuit has to be interrupted.

Accordingly this invention resides in a circuit breaker having a contact immersed in a quantity of insulating liquid which is contained in a chamber, a first mechanism for opening said contact, and a second mechanism for applying pressure to said quantity of liquid while it is quiescent and not liable to convert the pressure energy into kinetic energy, the two mechanisms being interlinked to operate simultaneously.

Conveniently a pneumatic piston forms part of the second mechanism. The interlinking means may be electrical or mechanical. In the first case the piston movement is controlled by a trip-coil, connected to be energised simultaneously with a trip-coil which causes opening of the breaker contact, or by a manual member adapted to control both the piston movement and the contact opening movement.

More details will become apparent and the invention will be more readily understood from the following descripiion referring to the accompanying drawing, in which:

FIG. 1 shows diagrammatically and by way of example a preferred embodiment of the invention;

FIG. 2 shows a modification; and

FIG. 3 shows a means by which the mechanism which applies pressure to the oil is operated by the breaker mechanism in the first part of its opening stroke.

An arcing chamber 19 of the breaker is shown in section, with a movable contact rod 18 and co-operating contact fingers 19 therein. The chamber 1%) is of insulating material and is supported by a metal plate 35 on a hollow insulator 34 and a post insulator 36. The arcing space communicates through holes 38 in the wall of chamber with the space 9 between the walls of the chamber it and insulator 34. The annular space communicates through holes 39 in the plate with an auxiliary space I it) at the base of a container Ztia of insulating material, which is mounted on the plate 35, opposite the chamber It). A valve 11 is arranged in a wall 47 separating the space 49 from a main space 23 which forms a venting chamber. Valve 11 closes when the pressure in the space exceeds the pressure in the space 23. However, another valve 12 is arranged in the wall 47 to open when the pressure in space 4% exceeds a predetermined value. The main space 23 communicates with a ring space 20 in the container Mia. The ring space may be filled with a moisture absorbent material, such as silica gel, and communicates in turn through a hole 21 with a separating space 411. The space 41 opens to the outer atmosphere through an aperture 42.

A chamber 8 encloses a linkage mechanism for operating the contact 18, and is supported on a hollow post insulator 7. The parts '7, 8, 9, it? are filled with oil. When Free the pressure in chamber it) increases to a certain value, valve 11 closes to contain that pressure. Before the pressure increase exceeds a permissible value a relief valve 12 opens to discharge an oil and vapour mixture, due to the arcing, into the space 23. This mixture causes the oil level, which is normally at 36, to rise into the annular space 20. At the level of hole 21 mixture flows into the space 41, from where any gas escapes to atmosphere through the aperture 42, while the liquid portion of the mixture returns through the hole 22 to the space 23 as soon as the oil level falls again.

It will be understood that the breaker may have more than one set of contacts. An insulator 34 identical with insulator 34 and accommodating an identical contact arrangement is shown. In the present case the two contact gaps are connected in series and the movable contacts of the two arrangements are actuated by a common linkage 17 situated in the housing 8 of metal which is supported on the hollow insulator '7, and itself supports the insulators 34, 34'. Linkage i7 is connected to an actuating rod 15 of insulating material in the insulator 7. A spring 16 biases the rod upwards for contact opening. The contact 1%, rod 15 and linkage 17 are shown in full lines for contact closure. However, the position of the movable contact rod 18 and of the linkage is also shown in interrupted lines for contact opening.

The hollow insulator 7 and housing 3 are filled with oil which communicates through openings 33 in a mounting plate 3'7 with the space 9 in insulator 34. The hollow insulator 7 rests on a closure member 43a, casing 43, provided to enclose mechanisms for operating the circuit breaker contacts and also for increasing the oil pressure in accordance with the invention. The closure 43a seals the casing 43 from the oil in the insulator 7 and housing 8.

For contact closure the lower end of rod 15 is connected through a lever 54 to a piston 45 which is reciprocable in a chamber 27.

The chamber 27 is connected through a valve means 6% to a pressure air reservoir 4-. Said means comprises valve discs 25 and 26 mounted on a common rod which is biased by a spring 29. The rod moves against thespring bias when the upper end of a lever 24, which has an intermediary point pivoted to the rod, bears against a latch 28, while the lower end of the lever is forced in the right hand direction by a solenoid 46 when the solenoid is energized from a source via terminals C1, C2. When the valve rod moves thus valve 25 closes and valve 26 opens. Pressure air flows from reservoir 4 to piston cylinder 27 to move piston 45 upwards. Then lever 44 rotates counter-clockwise and rod 15 moves downwards to close the circuit breaker. When the breaker is closed a member 48 of lever 44 engages a latch is which holds the breaker closed against the action of spring 16. Thus when solenoid 46 is de-energized, valves 25 and 26 can return to their rest position without allowing opening of the breaker. The breaker is held closed by the latch 14 engaging a roller at the end of member 43. To open the breaker the latch 14 is removed by the action of a lever 13. This lever action also releases the latch 28, and permits a rotation of lever 24 which now operates the valves 25, 26 to ensure that the air supply to the breaker closing cylinder 27 is cut off and the air in the cylinder 27 is discharged to atmosphere.

Usually opening the breaker is caused by electrically exciting a tripping coil 31 through a tripping circuit connected to terminals Ti and T2, but mechanical means for closing or opening the breaker can be provided, if desired, by coupling the lever 24 and the lever 13 to handles which are external to the casing a The arrangement, however, is such that tripping operation can take place even though the closing solenoid 46 remains a?) energized, and an external handle attached to lever 24 is in the breaker closed position, since with the latch 28 removed, the lever 24 has no fixed pivot so that operation of solenoid 46 can not actuate valve disc 26.

The arrangement for increasing the pressure of the oil in the arcing chamber comprises a piston 6 arranged to reciprocate in a chamber which communicates with the hollow insulator 7.

As the oil is virtually not compressible, a very small movement of the piston 6 to the right-hand side causes a pressure increase, which is transmitted through the oil in the insulator 7 and housing 8, holes 33, space 9, and holes 39 to the space 40 to close the valve 11. The pressure increase is now contained, and is also transmitted to the oil in arcing chamber 10. The movement of piston 6 is caused through a linkage 49 by a piston which is reciprocable in a pneumatic cylinder 5. This cylinder communicates through a valve means 61 with'the pressure reservoir 4.

The valve means 61 comprises two valve discs 2, 3 mounted on a common operating rod which is linked to the upper end of a lever it. The lever 1 is pivoted at its lower end. Its operation is controlled by a coil 30 which is connected through a switch 32 to the terminals T1, T2 to be energized simultaneously with the solenoid 31. Terminals T1, T2 can be readily connected to an energizing or supervising circuit, such as derived for instance by transformer means from current flow in a network in order to ensure automatic pressure increase and breaker contact separation in dependence upon the current flow. Such energizing or supervising means are well-known and understood so that they can be omitted from the drawing for the sake of greater clarity. When switch 32 is closed energization of solenoid 30 causes movement of the valve rod to the left-hand side, valve disc 2 closes while valve disc 3 opens, and pressure air can flow from 4 into the pneumatic cylinder 5 to move the pneumatic piston through the linkage 49. The electrical circuit control can be arranged to provide for the oil-pressurization either when the breaker is opened by a manual control switch, or by a protective relay, or both.

When oil vaporization through arcing is suflicient to increase the oil pressure at the interrupting gap for safe arc interruption, as is usually the case with fault tripping on full load interruption additional pressure increase may not be required to assist directly in are interruption, but may be valuable in maintaining oil pressure to give high dielectric strength in the gap immediately after the arc has been interrupted.

The pressure increase by means of the invention can be maintained for any desired length of time while the breaking duty may vary from 100% short-circuit breaking to low-current breaking duty. Should undesirable pressure increase occur the valve 12 opens to prevent excess pressure. 5

If a low current arc has to be extinguished, such as the charging current of an unloaded line, or the magnetizing current of a transformer, then additional pressure increase is desirable, switch 32 will be closed or a linkage will be provided for initiating operation of piston 6 from a manually controlled member.

As shown in FIG. 2, the permanent communication through holes 38 of FIG. 1 between the chamber 10 and space 9 in the insulator 34 can be avoided, and an annular space 9a can be separated as by a partition rib of insulator 34 and seal 71. The pressure relief valves 12a now interconnect the chamber 10 and space 9a. The volume 9a surrounding the chamber 10 is not subjected to pressurization by piston 6, as chamber 10 communicates with space 9 through the entrance hole for rod 18.

According to FIG. 3, the lever 1 which operates the valve disc 3 in the valve 61, bears against a latch 73 whilst the left-hand end of lever 1 is forced downwards by a member 74 when the breaker opens. On breaker closing, the latch 73 is released by the operation of valve 60 and lever '75 so that when lever 1 is depressed by member 74 it rotates anticlockwise about a pivot on the operating rod of valve 61 and does not operate this valve.

Other parts of FIG. 3 correspond to those of FIG. 1 and are similarly referenced. Thus, trip coil 31, when energized, operates lever 13 which causes breaker opening by the displacement of latch 14. The opening of the breaker causes pressure gas from container 4 to be directed through valve 61 for operating piston 6 which in turn causes pressure increase in the chamber 10.

While preferred embodiments have been shown, it will be understood that variations are possible without departing from the invention. The pressure increase can be directly applied to the oil volume in the arcing chamber, without pressure being applied to the oil surrounding the chamber as shown in FIG. 2.

What we claim is:

1. A circuit breaker having a housing including an arcing chamber having separable contacts therein surrounded by a fluid insulant, means for increasing its static pressure without conversion into kinetic energy before said contacts separate, said means being positioned in said housing remotely from said arcing chamber, an overflow chamber, a valve connecting said overflow chamber with said arcing chamber, said valve closing in response to a first fluid pressure in said arcing chamber, and a safety valve in said arcing chamber opening in response to a second fluid pressure, said second fluid pressure being higher than said first fluid pressure.

2. A breaker as claimed in claim 1, wherein the operation of the pressure increase means and of the contact separating means is electrically initiated.

3. A breaker as claimed in claim 1, wherein a pneumatic means is provided to cause the pressure increase at the contact closure.

References Cited by the Examiner UNITED STATES PATENTS 2,409,723 10/46 Terry 200- 2,724,756 11/55 Gieifers 200-150 2,789,186 4/57 Coggeshall 200-150 2,909,633 10/59 Umphrey 200-150 2,943,173 6/60 Level 200-150 3,002,073 9/61 Cobine 200-150 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCI-IAEFER, Examiner.

Claims (1)

1. A CIRCUIT BREAKER HAVING A HOUSING INCLUDING AN ARCING CHAMBER HAVING SEPARABLE CONTACTS THEREIN SURROUNDED BY A FLUID INSULANT, MEANS FOR INCREASING ITS STATIC PRESSURE WITHOUT CONVERSION INTO KINETIC ENERGY BEFORE SAID CONTACTS SEPARATE, SAID MEANS BEING POSITIONED IN SAID HOUSING REMOTELY FROM SAID ARCING CHAMBER, AND OVERFLOW CHAMBER, A VALVE CONNECTING SAID OVERFLOW CHAMBER IWTH SAID ARCING CHAMBER, SAID VALVE CLOSING IN RESPONSE TO A FIRST FLUID PRESSURE IN SAID ARCING CHAMBER, AND A SAFETY VALVE IN SAID ARCING CHAMBER OPENING IN RESPONSE TO A SECOND FLUID PRESSURE, SAID SECOND FLUID PRESSURE BEING HIGHER THAN SAID FIRST FLUID PRESSURE.

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