US3720799A

US3720799A - Gas blast circuit breaker

Info

Publication number: US3720799A
Application number: US00095553A
Authority: US
Inventors: A Eidinger; M Sanders; J Schnieder
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Switzerland; BBC Brown Boveri France SA
Priority date: 1969-12-11
Filing date: 1970-12-07
Publication date: 1973-03-13
Anticipated expiration: 1990-03-13
Also published as: AT302463B; DE2011521B2; DE2011521A1; FR2073140A5; GB1280258A; CH509649A; SE358769B; DE7008935U; CA929993A; NL7017902A; JPS511306B1

Abstract

In an electrical power circuit breaker of the gas blast type the switch contacts are subjected to a blast of pressurized gas in order to facilitate extinction of the arc when the contacts disengage under load. The pressure of the gas at the contacts is temporarily increased above the normal operating pressure by supplying additional gas to the switch contact chamber at a higher pressure from two serially connected storage chambers having unequal volumetric capacities in which the gas is stored and which communicate with each other through a constrictor. The larger of the two chambers is connected to a source of the higher pressure gas and the smaller chamber is connected to the circuit breaker for flow to the contact chamber by a pipe line which includes a controllable valve having a flow cross-section greater than that of the flow restrictor which interconnects the higher pressure gas storage chambers. This valve is opened for a brief period, e.g. about 50 milli-seconds when the switch contacts are opened.

Description

United States Patent 1 Eidinger et al.

1 1 GAS BLAST CIRCUIT BREAKER [75] lnventors: Adolf Eldinger, Nussbaumen; Mathias Sanders, Neuenhof; Jost Schnieder, Baden, all of Switzerland FOREIGN PATENTS OR APPLICATIONS France ..200/148 l 1March 13, 1973 Primary Examiner-Robert S. Macon Azt0rneyPierce, Scheffler & Parker [57] ABSTRACT In an electrical power circuit breaker of the gas blast type the switch contacts are subjected to a blast of pressurized gas in order to facilitate extinction of the are when the contacts disengage under load. The pressure of the gas at the contacts is temporarily increased above the normal operating pressure by supplying additional gas to the switch contact chamber at a higher pressure from two serially connected storage chambers having unequal volumetric capacities in which the gas is stored and which communicate with each other through a constrictor. The larger of the two chambers is connected to a source of the higher pressure gas and the smaller chamber is connected to the circuit breaker for flow to the contact chamber by a pipe line which includes a controllable valve having a flow cross-section greater than that of the flow restrictor which interconnects the higher pressure gas storage chambers. This valve is opened for a brief period, e.g. about 50 milli-seconds when the switch contacts are opened.

5 Claims, 4 Drawing Figures PATENTEDMARI 3 I973 W V m M. 3 my P "am m QJHE .MO." Wa sh w 3 J AM W 2 W. I, F

GAS BLAST CIRCUIT BREAKER This invention relates in general to electrical power circuit breakers of the so-called gas blast type wherein the switching contacts of the breaker are subjected to a blast of pressurized gas in order to facilitate extinction of the are when the contacts are disengaged. The present invention concerns an improvement in the known concept of temporarily increasing the pressure of the gas at the contacts above the normal operating pressure by supplying additional gas to the switch contact chamber from a compressed gas vessel in which it is stored at a pressure which is substantially higher than the normal operating pressure of the gas maintained in the contact chamber in readiness for use for contact blasting as soon as the contacts are disengaged. It is conventional for the switch contacts to reclose after an isolating switch in series with the circuit breaker has been opened and to re-pressurize the contact chamber to its normal operating pressure.

A circuit breaker arrangement is disclosed in German patent No. 609,941, wherein the contacts are subjected to an initial blast of compressed gas at the normal operating pressure prevailing in the contact chamber as soon as they disengage, this initial blast being followed by a supplemental temporary blowing at an increased gas pressure for approximately milliseconds while the contacts are still in the extinction position, and finally to continue the blowing at the initial, normal pressure. The compressed gas at the higher pressure for the supplemental blowing is obtained from compressed gas cylinders through suitably controlled valves.

A circuit breaker arrangement is also known from the German laid-open patent specification No. 1,176,233 in which a vessel, disposed at the high voltage potential of the circuit breaker in the vicinity of the contact chamber, stores compressed gas at a pressure higher than the normal operating pressure of the chamber, the higher pressure gas being expanded from the feed pressure to the operating pressure at the moment when contact separation takes place. For this purpose, the component controlling the gas expansion is a valve of the pressure reducing type which is so designed as to maintain the operating pressure at a constant level despite a diminishing cylinder pressure.

A principal object of the present invention is to provide an improved power circuit breaker of the type above mentioned for providing supplemental gas blasting of the switching contacts at a higher-than-normal pressure in the sense of minimizing the requirements regarding the time precision control for closing of the valve which releases the supply of compressed gas from the vessel of higher pressure to the chamber containing the circuit breaker contacts and at the same time protecting the contact chamber and other structural components through which the gas is conveyed to the chamber against an excessive pressure loading.

In accordance with the invention, this principal objective is attained by use of two serially connected chambers in which the gas is stored at the desired higher-than-normal pressure, these two chambers having unequal volumetric capacity and being in communication with each other through a restrictor. The smaller of the two high pressure gas storage chambers is connected to the circuit breaker for flow to the switch contact chamber by means of a controllable valve having a flow cross-section which is large in relation to the restrictor. By this improved arrangement, it is no longer necessary to ensure precise timing for closure of the controllable valve in order to limit the pressure peak which occurs in the circuit breaker and thus to protect it against excessive pressure stressing.

One suitable embodiment of the invention, now to be described, is illustrated in the accompanying drawings wherein:

FIG. 1 is a view in elevation of a high-voltage gas blast circuit breaker in single-pole configuration as improved by the invention;

FIGS. 1a and lb are views similar to FIG. 1 with the upper portion of the circuit breaker column deleted and which illustrate respectively different modified embodiments of the valve system connecting the high pressure gas storage chambers with the circuit breaker column; and

FIG. 2 are graphs depicting the course of the gas pressure variations in the circuit breaker and high pressure gas storage chambers with respect to time for two quickly following openings of the circuit breaker contacts such as would be caused for example by a tripping out of the circuit breaker in response to a transient disturbance on the line controlled by the breaker.

With reference now to the drawings, and to FIG. 1 in particular, numeral 1 designates in general a known circuit breaker installation of the gas-blast type which comprises four contact chambers 11b arranged in two pairs and in generally end-to-end relation atop a hollow columnar insulator 1a. Each contact chamber contains a pair of switch contacts which open in response to a switching-out command, and the four pairs of switch contacts are connected electrically in series to control the switching of a line to which the breaker is connected, the line connection not being illustrated. The pairs of switching contacts open simultaneously and are blasted with compressed gas maintained in the contact chambers so as to blow upon and effect extinction of the are drawn between the contacts as they disengage. In the usual construction, one of the switch contacts of each pair is configured as a nozzle and the other as a pin which is adapted to engage the mouth of the nozzle so that when the contacts disengage, the pressurized gas within the chamber flows past the contacts into and through the nozzle to a point of discharge.

The interiors of the two pairs of contact chambers communicate respectively with the Y-branched upper tubular ends of the tubular columnar insulator la. The lower end of insulator 1a is mounted atop and communicates with a vessel 2 which contains gas pressurized to the normal operating pressure of the switch contact chambers 11b. The gas storage vessel or container 2 is connected with a source of compressed gas by way of a compressor which maintains the gas pressure at the desired normal operating level.

In accordance with the invention, two serially connected chambers are provided in which gas is stored at a high pressure and from which high pressure gas is fed to the switch contact chambers 11b for supplementary higher pressure blowing of the arcs which are drawn in the respective chambers as the contacts disengage. In the illustrated embodiment, these two

chambers

4a and 4b are contained within a common pressurized generally cylindrical gas vessel 4, and are separated from one another by a transverse partition 4c provided with a flow restrictor 6 in the form of an orifice in the partition which places the two chambers in communication with each other. As is evident from the drawing, the two chambers have different volumetric capacities and the smaller one of the two, i.e. 4a communicates with the hollow columnar insulator la either directly or indirectly by way of the pressurized gas storage vessel 2 by means of a pipe line.3a containinga controllable valve 3. The flow cross-section of valve 3 is larger than that of the flow restrictor 6. The larger chamber 4b is provided with a booster supply of high pressure gas at a pressure of for example 150 atm. from a compressor or compressed gas supply network through the pipe line 5.

It is possible within the scope of the invention to constitute each of the

chambers

40, 4b as a separate vessel and to connect them serially by means of a short pipe line which itself forms the flow restrictor component required between the two chambers, or contains such a restrictor. This last mentioned embodiment is chosen with advantage if, for example, the flow restrictor is constructed in the form of a valve which opens with a predetermined delay towards the smaller chamber 4a, offering first a small, and then a relatively large booster crosssection since such a system will provide easy access to the valve.

Preferably, the larger of the two high-pressure storage vessels 4b has'a volumetric capacity which is at least four times greater than that of the other storage vessel 4a so that in the event of two contact interruption cycles occurring in quick succession which will arise in the event of a switching sequence occasioned by an unsuccessful switching out of a transient condition on the line, the peak pressure in the circuit breaker will remain practically unchanged even during the second interruption.

The circuit breaker operates in the following manner. An interruption order to the circuit breaker 1 through its control system 1c located at the lower end of the insulator column In is accompanied by an opening order to the valve 3, which may be of solenoid control type, the order being transmitted to valve 3 from control system 10 over the connection path indicated by the dashed line. The arrangement is such that valve 3 opens at about the same time as, or a few milliseconds in advance of, the opening of the circuit breaker contacts. Opening of valve 3 thus permits the higher pressure gas stored in the vessel 4a to flow over the line 33a into and upwardly through the supporting insulator column In to the switch contact chambers lb. Valve 3 remains open for a short period of from 20 to 30 milli-seconds and hence during that time interval, the contacts of the circuit breaker are subjected to a temporary higher pressure gas blast which is very effective in positively extinguishing the are drawn between the contacts. It is not essential that the desired re-closing time for valve 3 be accurately maintained since the volume of gas in the vessel 4a is rapidly discharged through the relatively large cross-section of valve 3 whereas replenishment of gas discharged from vessel 4a from the other vessel 4b takes place more slowly due to the flow throttling action of restrictor 6 in the connection between these two vessels.

In the modified embodiment illustrated in FIG. la, a second valve 7 is pneumatically and serially connected with valve 3 in the pipe line 3a, the two valves being controlled by the control system 1c. The control system is so designed that in a case where higher than normal operational currents have to be interrupted by the circuit breaker, e.g. short-circuit currents, valve 7 opens to develop a gas flow cross-section through it at least equal to that of valve 3. However, when interrupting at the normal operational current level, valve 7 is opened to a lesser extent thus releasing a flow-through cross section less than that of the opened valve 3, in which case valve 7 functions as a restrictor to decrease the flow of the higher pressure gas from vessel 40 into the pneumatic system of the circuit breaker.

In the modified embodiment illustrated in FIG. lb, a restrictor valve 8 is seen to be connected into the pipe line 3a in parallel with valve 3. Valve 8 is also controlled by the main control system 10 and the design is such that only valve 3 opens when high level (fault) currents are required to be interrupted and there is an unthrottled flow of gas through pipe line 3a. However, in the case where normal operational current is to be interrupted, valve 3 remains closed and valve 8 opens which has a smaller flow-through cross-section than valve 3 with the result that gas flow through pipe line 30 is correspondingly throttled.

FIG. 2 is an exemplified graph charting the variation in gas pressure with respect to time in milli-seconds in

thevessels

4a, 4b and circuit breaker 1. Curve a represents the pressure variation in vessel 4a, curve b the pressure variation in vessel 4b, and curve c the pressure variation in circuit breaker l for a case where two interrupting operations of the circuit breaker contacts occur in rapid succession over a time span of about 250 milli-seconds, as a result of an unsuccessful switching out of a transient. The gas pressure in the circuit breaker 1 will then increase temporarily at the instant of contact interruption from the normal operating pressure p to the higher level p The duration of this temporary pressure increase is seen to be something less than 50 milli-seconds.

Owing to the increase in current rupturing capacity, accompanied where appropriate by a simultaneous reduction in size of the contact chamber, as well as a reduction in the number of such chambers, the improved arrangement in accordance with the invention provides an overall reduction in cost of the circuit breaker installation.

In the embodiment of FIG. 1a, an electrical command to open the circuit breaker is delivered to the control system 10 and from there passes functionally to the switch contact chambers lb resulting in an opening of the circuit breaker contacts. The same command is delivered from the control system 1c to

valves

3 and 7, the command being delivered directly to valve 3 and indirectly to valve 7 through contacts of a relay, not illustrated, which is controlled in accordance with the magnitude of the line current. This relay responds when higher-than-normal currents have to be interrupted to actuate valve 7 to a more-open position so that the gas flow-through cross section of valve 7 is at least equal to that of the also open valve 3 as previously explained. However, for interruption of currents within the normal range, the relay remains non-responsive with the result that valve 7 remains in its rest position wherein the flow,through cross section of valve 7 remains at a value less than that of the opened valve 3.

In the embodiment of FIG. lb, and in a somewhat similar manner, a switch opening command is delivered to control system and also from there to

valves

3 and 8. A valve-controlling relay means, not illustrated, operated in accordance with the magnitude of the line current functions in conjunction with the

valves

3 and 8 so that only valve 3 opens when higher-than normal line currents are involved, whereas for line currents in the normal operating range, only valve 8 opens, this latter valve having a smaller flow-through cross section than valve 3.

We claim:

1. In an electrical power circuit breaker of the gas blast type wherein the contacts of the breaker are blasted with a pressurized gas the pressure of which is temporarily increased during disengagement of the contacts above normal operating pressure of the breaker by supplying gas thereto at a higher pressure from a supplementary gas source, the improvement wherein said higher pressure supplementary gas source is constituted by a pair of serially connected chambers in which the gas is stored at the desired higher-thannormal pressure, said chambers having an unequal volumetric capacity and being in communication with each other through a flow restrictor, the smaller of said gas storage chambers being connected to the circuit breaker for flow to the switch contact chamber by pipe line means including a controllable valve having a flow cross-section which is greater than that of said flow restrictor interconnecting said gas storage chambers.

2. An electrical power circuit breaker as defined in claim 1 wherein said pair of gas storage chambers are constituted by separate chambers located within a common storage vessel and which are separated from each other by means of a partition provided with said flow restrictor.

3. An electrical power circuit breaker as defined in claim 1 wherein the volumetric capacity of the smaller one of said pair of gas storage chambers is no more than one-fourth of the volumetric capacity of the other chamber.

4. An electrical power circuit breaker as defined in claim 1 and wherein said pipe line means connecting the smaller one of said pair of gas storage chambers also includes a restrictor valve connected in series with said controllable valve, said restrictor valve serving to release a flow cross-section of a magnitude at least equal to that of said controllable valve when high level fault currents are to be interrupted and to release a smaller flow cross-section when currents of a normal operational level are to be interrupted.

5. An electrical power circuit breaker as defined in claim 1 and which further includes a restrictor valve connected in parallel with said controllable valve as regards delivery of the higher pressure gas from the smaller one of said pair of gas storage chambers to said circuit breaker, said controllable valve being opened only when high level fault currents are to be interrupted, and said restrictor valve being opened only when currents of a normal operational level are to be interrupted.

Claims

1. In an electrical power circuit breaker of the gas blast type wherein the contacts of the breaker are blasted with a pressurized gas the pressure of which is temporarily increased during disengagement of the contacts above normal operating pressure of the breaker by supplying gas thereto at a higher pressure from a supplementary gas source, the improvement wherein said higher pressure supplementary gas source is constituted by a pair of serially connected chambers in which the gas is stored at the desired higher-than-normal pressure, said chambers having an unequal volumetric capacity and being in communication with each other through a flow restrictor, the smaller of said gas storage chambers being connected to the circuit breaker for flow to the switch contact chamber by pipe line means including a controllable valve having a flow cross-section which is greater than that of said flow restrictor interconnecting said gas storage chambers.