US2887549A - Current surge arrester - Google Patents

Description

Fi led Dec.

fir/R575.

lNyENTOR. Sam 15m.

AUGUST CY United States Patent CURRENT SURGE ARRESTER August 'C. Schwager, Portland, Oreg., assignor to Schwager-Wood Corporation, Portland, Greg, a corporation of Oregon Application December 3, 1957, Serial No. 700,377

Claims. (Cl. 200-146) My present invention relates to circuit interrupting devices and more particularly to a current surge arrester for employment in connection with a vacuum insulated cir cuit breaker when interrupting inductive load currents such as transformer magnetizing currents or reactor currents of a power distribution system.

An object of the invention is to provide a surging and effective current arrester of novel construction which can be employed with a high voltage vacuum insulated circuit breaker when mounted within a high voltage terminal insulating support to interrupt and control load circuits of a high voltage power distribution system.

Another object of the invention is to provide a simple surging current dissipating arc-gap which can be employed in a novel manner in connection with a vacuum insulated circuit breaker as protection against arc-overs between the contacts of the circuit breaker when interrupting or disconnecting a load circuit in a power distribution system.

A further object of the invention is to provide a surging current arrester or arc-gap for use as a protection against arc-overs between the contacts of a vacuum insulated switch and having a condenser for dissipating gases generated in the arc-gap in a harmless manner.

Another object of the invention is to provide an expulsion type surging current arrester which is particularly adaptable for use with vacuum insulated circuit interrupting switches that are mounted within a weather protective line terminal supporting insulator and operating in the manner disclosed in my United States Patent 2,838,636, issued June 10, 1958, and entitled, High Voltage Circuit Interrupting Switch Means.

Other objects and advantages will be in part evident to those skilled in the art and in part pointed out hereinafter in connection with the accompanying drawing, wherein there is shown by way of illustration and not of limitation a preferred embodiment of the invention.

In the drawing wherein like numerals refer to like parts throughout the several views:

Figure 1 is a side view, partly in section and with parts broken away to disclose details of construction, showing my surging current arresting means as mounted upon the terminals,

Figure 2 is a fragmentary view partly in section showing the device of Figure 1 as mounted within a high voltage insulator and between the terminals of a vacuum insulated circuit breaker of conventional design and with a condenser by which the are generated deionizing gases are condensed and expelled in a harmless manner,

Figure 3 is a horizontal sectional view taken along lines IIIIII of Figure 2, and

Figure 4 is a curve diagrammatically illustrating operating conditions when employing my invention.

In the transmission of high voltage electric power, airbreak disconnecting switches are often used to isolate sections of the power transmission system or for disconnecting a load circuit from an associated network. To avoid arcing upon contact separation, this switching operation in most instances must be carried out under conditions of no-load on the circuit, but even under no-load conditions the high voltages employed on some transmission systems produce charging currents of appreciable magnitude which may cause considerable arcing even under no-load conditions. While certain of these disconnecting switches, particularly those of the low voltage type, have successfully interrupted charging and small load currents their use at high voltages is unsatisfactory as any are established during the circuit opening operation may be blown across the line or to grounded parts and thus cause a flow of fault currents.

To overcome the above arcing difficulties on the higher voltage power distribution systems, it is the practice to connect a circuit interrupting switch or circuit breaker having separable circuit controlling contacts which operate in an arc suppressing medium in series circuit with the air break disconnecting switch blade. These circuit breakers may have their circuit controlling contacts immersed in an oil or other are quenching liquid and/or they may be provided with air or gas blasts which operate to extinguish any are established between their contacts upon separation. Another such circuit breaker for use inthe manner here related is disclosed in my United States Patent No. 2,810,805 dated October 22, 1957, and entitled, Circuit Interrupting and Isolating Switch. In this patent the circuit controlling contacts of the circuit breaker are shown as confined in a vacuum insulated envelope and the circuit under control is interrupted by the circuit breaker prior to the circuit isolating operation of circuit isolating switch blade.

As is well known vacuum insulated circuit breakers of the type to be described and shown in the accompanying drawing provides one of the most effective means for interrupting alternating current circuits and from experionce such circuit breakers have been found to operate successfully for repeated switching operations on a power transmission system carrying moderate load currents up to 1000 amperes. In the switching of high voltage capacitor banks the current values are generally in the order of amperes and. with such a current value and possibly down to current values of approximately 10 amperes, interruptions of the circuit will always occur at the next succeeding current Zero on the circuit. However, when an attempt is made to interrupt smaller current values, for example, in the order of one ampere, the flow of current is interrupted immediately upon separation of the circuit breaker contacts. This is due to the fact that the deionization rate of the vacuum insulated circuit breaker is of extremely high magnitude. Therefore, instead of the flow of current being interrupted at the next current zero after contact separation, the current is chopped off, in point of time short of the next current zero on the line. While this chopping off of the current causes no ill effects when switching capacitor banks, it does, however, present a problem in switching reactive current such as the magnetizing current of transformers on the system. This is explained by the fact that the magnetic energy stored in the transformer cores prior to this chopping off of the current flow causes extremely high voltages to be built up across the open contacts of the circuit breaker. Under some conditions of operation these high voltages can set up a surge of current high enough to break down the gap between the separating contacts of the circuit breaker which aside from the fact that failure to interrupt the circuit occurs, will also cause damage to the circuit breaker contacts. This failure to interrupt the circuit at these extremely small current values requires that some means be provided to protect the circuit breaker contacts against this surge of current. Therefore, to overcome the difficulty due to this chopping off of the current at lower current values, my invention contemplates the connection 3 I of an efiective current surge expulsion means, which comprises two spaced electrodes mounted upon the terminals of the vacuum insulated circuit breaker and forming an air gap that is confined in a deionizing gas producing expulsion tube externally of the evacuated envelope within which the circuit breaker contacts operate.

In the drawing, I have shown my invention as employed with a vacuum insulated circuit breaker of the type covered by I. E. Jennings, Patent No. 2,740,869, dated April 3, 1956, and entitled, Vacuum Switch. As here shown, the vacuum insulated switch or circuit breaker, as I prefer to call it, consists of an evacuated envelope that forms an evacuated enclosure for a stationary contact 11 and a relatively movable contact 12. The stationary contact 11 is connected through the upper end wall of the envelope 10 to a terminal ring 13 and at the lower end of the envelope 10, the movable contact 12 is connected to a second terminal ring 14. In this particular assembly, the movable contact 12 is sealed for movement through the lower end wall of the envelope 10 by a Sylphon type bellows 15 which permits movement thereof when an operating force is applied to an operating rod 16 extending at the lowerend of the en velope 10. In Figure 1 of the drawing, the terminal ring 13 is shown as carrying a bracket 17 into which there is threaded an arc-gap forming electrode 18 which may be adjusted to a desired position and firmly locked by a check nut 19 at the threaded end thereof. Secured to the underside of the bracket 17 there is a spider-like support 20 which carries an expulsion chamber forming tube 21 of hard fiber or other like deionizing gas producing material. This tube 21 extends for some distance beyond the end of the arc-gap forming electrode 18 and spaced from the lower open end of the expulsion tube 21, there is a second arc-gap forming electrode 22 that extends upwardly from a bracket 23 carried by the lower terminal ring 14 of the vacuum insulated circuit breaker. With this arrangement, it will be seen that there will be provided a surging current dissipating arc-gap between the terminal rings 13 and 14 externally of the evacuated envelope 10 within which the circuit interrupting contacts 11 and 12 are confined.

While the above described arrangement will be found useful and practical in many situations where the expulsion of deionizing gases from either or both ends of the expulsion tube 21 may not be objectionable, there may be other situations where a difierent arrangement will be preferred. As showing one such difierent arrangement, 1 have in Figure 2 of the drawing shown the upper arc-gap forming electrode 18 as mounted upon the bracket 17 in the manner previously described. In this arrangement, however, the deionizing gas generating expulsion tube, here designated by the numeral 24, is shown as closed at both ends and in lieu of the lower arcing electrode 22, I here provide a deionizing gas cooling or condensing chamber 25. This chamber 25 is connected to and mounted upon the lower terminal ring 14 of the vacuum insulated circuit breaker so that it will form the lower electrode and operate in conjunction with the adjustable electrode 18 to form an arc-gap within the expulsion tube 24. The use of such a gas condensing and cooling chamber will be particularly useful where the vacuum insulated circuit breaker is mounted within a line terminal supporting insulator 26 as shown in my first above identified patent.

In Figure 3 of the drawing, the deionizing gas cooling and/or condensing chamber 25 has a spirally extending partition 27 that forms a lengthened involute path for the flow of the generated deionizing gas to a point of exit 28 where the gas is harmlessly exhausted. In this showing the deionizing gas cooling and/or condensing chamber 25 is shown, by dot and dash lines, as having three supporting pads 29 by which it may be mounted within the insulator 26 upon vertically extending supporting rods as shown in my aforesaid application for patent. i

For a description of the operation of my invention, reference is now made to Figure 4 of the drawing where I have shown the sinusoidal current waves of a power line circuit in relation to the time of the vacuum insulated circuit breaker contact separation. In this figure, the curve A shows a half cycle of a current having a value of amperes maximum, which when contact separation occurs at the point t with a current value of this magnitude the current wave will continue as here shown to be sinusoidal to the next natural current zero of the power line and at this instance, the current flow will be interrupted. However, as above stated, if an attempt is made to interrupt still smaller current values, for example, in the order of one ampere and contact separation occurs at the point t, the current flow will be immediately interrupted or chopped ofi short of the next current zero on the line as illustrated by the curve B. When this happens and an over-voltage occurs during contact separation due to this chopping off of current flow, this over-voltage will flash the gap between the arcgap forming electrodes 18 and 22. This flash-over will permit a follow-up current to flow as mentioned hereinbefore, but the current being in the order of one ampere, it will be harmlessly disposed of. The diameter of the expulsion tubes 21 or 24 will preferably be small, possibly no more than A; of an inch, which will be sufficiently small to interrupt this follow-up current at the next current zero on the line. Tests have shown such a gap with an expulsion tube of such small diameter is suitable for interrupting follow-up currents up toseveral thousand amperes, which is a value far in excess of the duty that the air gap as here proposed will ever be exposed to in its normal field of use.

When the follow-up current, upon contact separation is in excess of 100 amperes, interruption of the circuit may be accompanied with the emission of considerable flame at and around the air-gap between the arc-gap forming electrodes and in order to make this flame harmless, it is further proposed to cool the arc gases in the cooling chamber 25 as shown in Figure 2 of the drawings. Thus irrespective of the magnitude of the are by the arrangement here shown with a small diameter expulsion tube 21 or 24 an effective amount of arc extinguishing gases for any arcing after the initial spark-over upon separation of the contacts 11 and 12 of the vacuum insulated circuit breaker will be sufiicient to extinguish any are which may be caused by the chopping off of a low current flow as above indicated. In this latter arrangement, the arc-gas will travel along the spiral or involute path formed by the vertical partition 27 to the exhaust opening 28 of the condensing and cooling chamber 25 where it will be thoroughly cooled. In this way the are deionizing expulsion gases will be harmlessly neutralized with an assembly that will take up very little space and can be mounted as an integral part of the vacuum insulated circuit breaker.

While I have, for the sake of clearness and in order to disclose my invention so that the same can be readily understood, described and illustrated a specific form and arrangement, I desire to have it understood that this invention is not limited to the specific form disclosed, but may be embodied in other ways that will suggest themselves to persons skilled in the art. It is believed that this invention is new and all such changes as come within the scope of the appended claims are to be considered as part of this invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a circuit interrupting device of the character described, the combination of a vacuum insulated circuit breaker having cooperating circuit controlling contacts operating in a vacuum within an elongated evacuated envelope, spaced line terminals for connecting said circuit controlling contacts in a power line circuit between which the evacuated envelope of the circuit breaker is supported, a first arcing electrode mounted upon one of said spaced line terminals extending along the side of said envelope, a second arcing electrode adjustably mounted upon the other of said line terminals in spaced axial alignment with said first arcing electrode and forming an air-gap adjacent and externally of said evacuated envelope, and a tubular housing of arc pervious material forming a deionizing gas generating enclosure about the air-gap between said arcing electrodes, characterized by the fact the air-gap formed between said arcing electrodes when supported as a unitary structure by and between the spaced line terminals operates to protect the current controlling contacts of the circuit breaker against overvoltage arcing therebetween in the event of a chopping-off of current flow closely following a point of current zero on an alternating current power transmission line.

2. In a high voltage power line circuit interrupting system, the combination of a vacuum insulated circuit breaker having relatively movable circuit controlling contacts enclosed in an evacuated envelope, power line terminals carried by said envelope for connecting the contacts of said circuit breaker into a power line circuit, an arc-gap forming electrode connected to each of said power line terminals and forming an air-gap externally of and in parallel circuit with the enclosed contacts of said vacuum insulated circuit breaker, a cylindrical housing of deionizing gas producing material forming an enclosure about the air-gap between said electrodes, and characterized by the fact that one of said electrodes is constructed to form a chamber having a horizontally dis posed involute passageway surrounding the adjacent power line terminal of the circuit breaker through which gases generated upon a flash-over between said electrodes are cooled and rendered harmless.

3. In a high voltage circuit interrupting system, the combination of a vacuum insulated circuit breaker having relatively movable circuit controlling contacts enclosed within an evacuated envelope, external terminals carried by said envelope for connecting the contacts of the circuit breaker in a power line circuit, aligned arcgap forming electrodes carried by and forming an airgap between said external terminals externally of said evacuated envelope and in parallel circuit with the contacts of said vacuum insulated circuit breaker, and a tube of deionizing gas producing material forming a gas tight enclosure about the air-gap between said electrodes, characterized by the fact that one of said electrodes is in the form of a housing having an involute partition which forms a tortuous exhaust path for the cooling and exhaust of gases generated upon a flash-over between said electrodes.

4. In a power line circuit controlling device, the com bination of a circuit breaker unit having circuit interrupting contacts operatively associated within elongated evac uated envelope, power line terminals supported externally at opposite ends of said elongated envelope, means extending at one end of said envelope for operating one of said enclosed contacts between its circuit closed and circuit open positions, a bracket extending from one of said power line terminals, an air-gap forming electrode adjustably mounted upon said bracket and extending toward the other of said power line terminals, a second bracket extending from said other of said line terminals, a second air-gap forming electrode mounted upon said second bracket in axial alignment with said adjustable electrode, and a tubular member of deionizing gas producing material forming an arc confining chamber over the air-gap formed between said electrodes, the air-gap between said electrodes operating as a current discharge path externally of said evacuated envelope for current surges in the power line resulting from an interruption of an inductive load by the separation of said circuit breaker contacts closely following a point of current zero on the circuit.

5. In a power line circuit controlling device, the combination of a circuit breaker unit having normally closed circuit interrupting contacts operatively associated within an elongated evacuated envelope, power line terminals supported externally at opposite ends of said elongated envelope, means extending at one end of said envelope for operating said enclosed contacts into an open circuit position, a bracket extending externally of said envelope and toward the other of said power line terminals, said housing having a' horizontally disposed partition that forms an involute passageway with an inlet opening in alignment with said adjustably mounted air-gap forming electrode and an exhaust outlet inwardly therefrom, and a tubular member of deionizing gas producing material disposed about said adjustable air-gap forming electrode extending into the inlet opening of said housing, whereby gases produced by an are between said adjustable electrode and said housing upon an interruption of an inductive load by the separation of said circuit breaker contacts will be cooled before exhausted from said housing.

Great Britain 1933 Great Britain Sept. 5, 1944

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