US2003298A - Electrical protective apparatus - Google Patents

Description

Filed Dec. 19. 1931 INVENTOR 1 1 Patented June 4, 1935 UNITED STATES PATENT OFFICE George N. ileminon, Homewood, Ala, assignor to Southern States Equipment (Company, Birmingham, Ala.

Application December 19, 1931, Serial No. ESZAMI? '3 Claims.

The object of my invention is to provide a combined fuse and lightning arrester which shall be simpler, more easily made, and more effective in operation than equipment previously made.

Fuse equipment for protecting a transformer is already made with a tubular container which is pivoted at one end and so arranged that the tube swings open whenever the fuse link has been ruptured, thereby giving a positive indication that the circuit is open. Also lightning arresters have been used near such fuses, these arresters always being held to the cross-arms by separate mountings; and often it is found advisable to use additional cross-arms for the arresters.

Arresters are now used which consist merely of a suitable arc gap from line to ground. The gap is of such spacing that the voltage has to rise substantially above normal conditions before current will break across the gap. When once broken down, however, the arc offers but little resistance to the flow of current as the heated gases are highly conductive. Under such conditions a high voltage surge on the line is discharged across the gap to ground, and this is followed by a flow of dynamic current which is in reality a short-circuit to ground. This opens the oil circuit breakers and leaves the power supply off the line, so the arc across the gap immediately ceases and is replaced by cool air, restoring normal conditions as soon as the circuit breakers shall have been closed. The gap is so substantial that it can withstand such an are without serious damage. To prevent the shortcircuit and the consequent opening of the breakers and interruption to service, some arresters are made with resistance units in the ground path to limit the flow of dynamic current sufficiently for the arc across the gap to break the circuit before the breakers open. Such an arrester will discharge to ground the small high frequency surges which otherwise constitute many of the causes of line trouble. I

Arresters which have resistance members among their elements are'occasionally so badly damaged by lightning that they ceasev to function as arresters, and actually form a path from the line to ground. Such an occurrence interrupts service on the line until the damaged arrester can be disconnected; and it is often difficult to determine which of the arresters on a long line is the damaged one.

My arrangement overcomes these objections and provides a device that is compact and also low in cost.

. an arc across I2, I3, and to cause no blowing of Referring to the drawing, the figure shows one of my devices in actual service. To a cross-arm i is clamped the iron support 2 upon which two insulators 3, l are mounted. An insulating tube 5 is pivoted at i and held at its upper end by the latch members I, 8. Inside the tube is the fuse member 9, and when this is ruptured the tube automatically drops open to the position 5. All this is well known to those familiar with the art. 10

A third insulator I6 is clamped to 2 and contains a resistance element I I which forms a current-limiting path between the adjustable airgap I2, I3 and the ground-wire I4. Together these form a path for discharging high-frequency small-amperage currents from line to ground.

Occasionally an electric line is subjected to conditions which require a much heavier discharge to relieve the abnormal voltage. The adjustable horns I5, I6 give a direct path to 20 ground with no resistance member in the circuit after the gap has been spanned.

The insulator base I9 and the base member 20 of the horn I6, are held by two bolts 2|, so that they clamp tightly about the base member 2. 5 This clamp can be adjustably placed upon 2, and adjustment is also provided for the gap electrodes I2, I3 and I5.

The conductor I1 connects with the main line, and the conductor I8 connects with a transformer. The fuse 9 serves the double purpose of protecting the transformer and clearing the arrester units In, II, I2,- l3 from the line in case they become short-circuited.

In operation, any small high-frequency surge will be discharged through the resistance II as soon as the voltage gets high enough to span the closely-set gap I2, I3. The resistance II is enough to prevent linecurrent from maintaining the fuse in most cases.

However, a surge sometimes is so heavy that it cannot pass easily through the resistance I I and the voltage continues to increase until it is sufficient to span the gap I5, I6. This relieves all high-voltage surges which are on the line at this place, and it also usually causes the oil breaker at the power station to open.

The horns are heavy enough not to be damaged even by such discharge and service is resumed as soon as the oil breaker is reclosed. Such a momentary interruption is better than to allow the transformers or other apparatus to be damaged.

If for any reason the close gap I2, I3 should ment within the housing, two arc-gaps each consisting of two spaced electrodes, one electrode of one arc-gap attached directly to the base, one electrode of the second arc-gap connected to the high-resistance element, together with one other electrode for each of the two arc-gaps, one being connected to each of the said insulated fuse terminals.

2. Electrical protective equipment which includes a base, two fuse terminals insulated from the base, and two arc-gaps, one electrode of one of the arc-gaps being connected to one of .the

fuse terminals, one electrode of the other aregap being connected to the other terminal, the other electrodesof the two are gaps being connected together through a resistance.

3. As an article of manufacture, a single base supporting two fuse terminals" base, a fuse container supported between the said terminals, an arc-gap between each fuse terminal and the said base, at least one of the ,said are gaps being adjustable.

4. As an article of manufacture, a single base supporting two fuse terminals insulated from the base, a fuse container supported between the ulated from the I l aooaaae said terminals, an arc-gap between each fuse terminal and the said base, and a high-resistance in series with one of the said arc-gaps between a fuse terminal and the base.

. 5. Electrical protective equipment which includes a metal base supporting two spaced ter minals each insulated from the basei a container and a fuse within it connecting the said terminals, a discharge arc-gap between each of the said terminals and the said base, and a resistance forming part of the discharge path from one the terminals across the gap to the base.

6. Electrical protective equipment which includes a metal base supporting two spaced terminals each insulated from the base, a container and a fuse within it connecting the said terminals, a discharge arc-gap between each of the said terminals and the said base, a resistance forming part of the discharge path from one of the terminals across the gap to the base, and a metallic conducting path in series with the arc-gap which is between the second of the said terminals and the base.

7..Electrical protective equipment/which includes a metal base supporting two spaced terminals insulated from the base, a container and a fuse within it connecting the said insulated terminals, a ground, a discharge arc-gap between each of the said terminals and ground, the conductive part of the path from terminal to ground in series with one arc-gap being of substantialy higher resistance than the conductive part of the path from terminal to ground inseries with the other arc-gap.

. GEORGE N. LEMMON.

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