US1752970A - Electrical protective apparatus - Google Patents

Description

April 1, 1930.

w. WALTY 1,752,970

ELECTRICAL PROTECTIVE APPARATUS Filed Feb. 12 1926 yam/w;

Another object is the provision of appa- Patent ed Apr. 1, 1930 UNITED STATES PATENTOFFICE "WERNER WALTY, or ENNETBADEN, SWITZERLAND, ASSIGNOR TO A. G. nnown novnnr & GIE. OE BADEN, SWITZERLAND, A JOINT-STOCK COMPANY OF SWITZERLAND ELECTRICAL PROTECTIVE APPARATUS Application filed February 12, 1926, Serial No. 87,853, and in Germany February 16, 192 5.

the efiects resulting from short-circuits etc. It has to do particularly with the protection of respective generating or converting units interconnected in a system.

The general object of the invention is the provision of apparatus for automatically cutting out the unit affected and maintaining the desired functioning of the others.

ratus for effecting this result, which will be immediate and certain in response and of simple and compact construction.

Other and further objects will be pointed out or indicated hereinafter, or become obvious to one skilled in the art upon an undera standing of the present disclosure. The particular arrangement here shown and de generating or converting units, the short-cirscribed is presented for illustration only, and the invention may be embodied in apparatus differing therefrom in various particulars, all within the scope of the appended claims.

In the event of a short-circuit in one of the units of an electrical installation including cuit actsby way of the collectors or bus-bars on the other units and causes all the main automatic switches to open.

the switches will not all be left open, ac-

cording to the present invention reverse current relays are interposed between the automatic switches and a collector or bus-bar, of.

I which relays only that in the circuit containing the defective or short-circuited unit responds and prevents the opening of the automatic switches of the sound units.

The accompanying drawing illustrates diagrammatically by way of example one em-.

bodiment of the invention.

Inthe drawing I, II, III denote three mercury vapour rectifiers of which the main current switches h 7?, k located in the continuous or direct current leads from the rectifiers, are controlled by .zero voltage coils I 0 0 0 connected to an auxiliary source of the relative maximum current or overload- I relays a a a, the coils of whlch IIlELXlHlIlIIl of current is. The circuit of each zero voltage coil contains the normally closed contacts In order that 5 current relays are located in the main contlnuous current leads from the rectifiers I, II, III. The coils of reverse current relays b b 6 are also located in the leads from the rectifier-s between the main switches h 12 it and the bus-bar 9. Each of the reverse current relays b b 6 has switch contacts d, e, f, of which the contacts 6 and f are normally closed, the contacts cl being normally open. On passage of a return or reverse current the relays b 5 ,6 respond,

direct current'sources 9 ,1 and j Referring more particularly to relay b the arrangement is such that coil 2' tends to raise the; switch to its upper position, the extent of excitation of this coil, however, being such that the'same is not sufficient by itself to raise the switch to such position. During normal current'flow,the lower coil opposes theactionof coil i and has an influence on the switch tending to urge the same down- Wardly. Upon the occurrence of reverse current flow, however, the action of the lower coil with respect to the switch is reversed,

the lower coil then acting with and supplementing the action of ,coil 2' to raise the switch to its upper position. The manner or principle of operation of relays Z2 and b is the same.

Assuming that there is a return surge in the rectifier II because of a short-circuit, then all the three rectifiers work on the short circuit. The maximum current relays a a a all respond and open their contacts. Of the reverse current relays only 6 responds and opens its lower contacts 6 and 7, and closes its upper contacts d. The closure of the upper contacts (Z short-circuits the two auxiliary conductors 2', thereby bridging the con tacts of the maximum current relays a a This will prevent the circuit. breakers 7L and it from tripping in spite of the responsevof becomes currentless so that the switch a opens while the switches h and it remain closed.

What I claim is:

1. In combination, an electric supply line,

a plurality of current sources connected in' parallel to said circuit, a circuit breaker for each of said sources for disconnecting the same from said line, overload relay means associated with each circuit breaker for tripping the same in response to excess current flow from the respective source to said line,

and a reverse current relay means associated with each of said circuit breakers for preventing tripping of the circuit breakers associated with the sources to which no reverse current flow takes place, said relay means being so arranged that in absence of reverse current flow through any one of said circuit breakers, overload in any of said circuit breakers will cause the same to be tripped.

, 2. In combination, an electric supply line, a plurality of current sources, leadsconnecting each of said sources to said line in parallel, circuit breakers in said leads for individually disconnecting said sources from said line, overload relay means for individually tripping the circuit breaker associated with the respective leads on occurrence of overload therein, and reverse current relay means associated with each of said leads for rendering inefl'ective the action of the overload relay means associated with the leads wherein no reverse current flow takes place.

, 3. In combination, an electric supply line, a

normally closed double-pole switching con- "tacts for disconnecting the energizing contacts of the associated tripping coil from said auxiliary double-pole line, and normally plurality of current sources, leads for each of said sources for connecting the same to said line in parallel, a circuit breaker associated with each of said leads for disconnecting the respective sources from said line, a tripping coil for each of said circuit breakers, an overload relay associated with each of said leads for actuating the tripping coil of the associated circuit breaker to disconnect said source on occurrence of an overload in said lead, and a reverse current relay in each of said leads, an auxiliary control circuit normally interconnecting the control contact-s of said overload relays of the several leads, the reverse current relay of each of said leads having contacts operable to provide for disconnection of the associated overload relay from said control circuit and interlocking auxiliary control contacts for said control circuit operable to provide an interlocking circuit rendering ineffective the action of the overload relays of the leads that are free from reverse current flow.

4. In combination, an electric supply line, a plurality of current sources, leads for each of said sources for connecting the same in parallel to said line, a circuit breaker in each of saidleads for disconnecting said sources from said line, a no-voltage tripping coil for each of said circuit breakers, an overload current relay associated with each of said leads, each overload relay having control contacts fornormally energizing the tripping coil of the associated circuit breaker and being arranged to deenergize said circuit occurrence of an overload, an auxiliary control circuit interconnecting the control contacts of the overload relays associated with the several leads, a reverse current relay associated with each of said leads, each of said reverse current relays having normally closed contacts operable to provide for disconnection of-the associated overload relay from said auxiliary control circuit and bridging contacts for said auxiliary control circuits operable to provide an interlocking circuit bridging the control "contacts of the overload relays of the other circuit breakers to prevent tripping of their respective circuit breakers.

5. In combination, an electric supply line,

a plurality of parallel feeders connected to "said line, a circuit breaker associated with each of said feeders for disconnecting" the same from said line, a no-voltage tripping coil for each of said circuit breakers having a pair of energizing contacts, an overload relay associated with each of said feeders arranged tonormally hold closed said contacts and to open the same on occurrence of an overload, an auxiliary 2-pole'line interconnecting corresponding energizing contactsof the several tripping coils, a reverse current relay associated with each of said feeders, each of said reverse current relays having open bridging contacts for short circuiting said auxiliary double-pole line tobridge the energizing contacts of the tripping coils as sociated with the other feeders. I

6. In an electrical system, a plurality of direct current supply lines, cut-out devices associated respectively with said lines and each being responsive to abnormal current conditions in the respective associated line and being operable upon occurrence ofsuch conditions therein to cut out the same, control devices associated respectivelv with said lines and each being responsive to conditions of reverse current flow in the respective associated line, and connections providing-interlocking circuits between said cut-out devices and said control devices and which are effective upon operation of a control device, associated with one of said lines to lock out of operation the cut-out devices associated with the other of said lines.

In testimony whereof I have hereunto subscribed my name at Zurich, Switzerland, on

the 21st day of January, A. D. 1926.

WERNER WALTY.

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