US2856566A - Control system for electrically operated circuit interrupters - Google Patents

Description

Oct. 14, 1958 M. B. FORNWALT 2,855,565

CONTROL SYSTEM FOR ELECTRICALLY OPERATED CIRCUIT INTERRUPTERS Filed Dec. 3, 1956 SE'CONDARY NETWORK PIP/MAR Y FEEDER Inventor:

Max B. Fornwalt,

CONTROL SYSTEM FOR ELECTRICALLY OPER- ATED CIRCUIT INTERRUPTERS Max B. Fornwalt, Springfield, Pa., assignor to General Electric Company, a corporation of New York Application December 3, 1956, Serial No. 625,680

6 Claims. (Cl. 317-22) This invention relates to control systems for electrically operated circuit interrupters, and more particularly to an improved system for controlling the energization of the closing mechanism of an electric switch or circuit interrupter.

In conventional closing control systems for electrically operated circuit interrupters, it has been necessary to employ a cut-off switch to deenergize the closing mechanism at a critical moment during closing operation, thereby to prevent excessive and harmful overtravel in the mechanism. Precise adjustment of the cut-off switch is necessary in such conventional systems, and this adds significantly to the manufacturing and maintenance costs of the interrupter. Accordingly, a general object of this invention is the provision, for closing an electric circuit interrupter, of a control system that does not require the use of a critically adjusted cut-ofi switch.

A further object of the invention is the provision, for closing an electric circuit interrupter, of an improved control system which prevents energization of the interrupter closing mechanism whenever the interrupter is in its closed circuit position.

It is another object of the invention to provide an improved closing control system employing an auxiliary relay which prevents energization of the closing mechanism unless there is sufiicient voltage available for successfully completing the closing operation.

Another object of the invention is the provision of an improved closing control system employing an auxiliary relay arranged to permit automatic reclosing operation of the circuit interrupter in response to predetermined circuit conditions, said auxiliary relay being energized only during the reclosing operation.

A further object is to provide an improved closing control system in which the circuitry is such that the contacts of the auxiliary relay are not required to break the energizing current supplied to the closing mechanism.

Still another object is the provision, for a circuit interrupter having a closing mechanism which converts electric energy into mechanical energy and utilizes the mechanical energy to close the interrupter, of an improved control system for successfully performing a closing function independent of the value of supply voltage at the moment the interrupter contacts make circuit.

In carrying out my invention in one form, I provide a control system which is particularly well suited for controlling the closing of an electric circuit interrupter having a closing mechanism that converts electric energy into mechanical energy and utilizes the mechanical energy to close the interrupter. The interrupter also includes a position indicating contact which opens as the interrupter moves toward its closed circuit position. My improved control system comprises an auxiliary relay which is energized in controlled response to predetermined circuit conditions including the open circuit condition of the interrupter. The auxiliary relay is provided with a sealin contact connected to retain the relay energized as long as the interrupter remains open. I provide circuit means nited States Patent including another contact of the auxiliary relay and the position indicating contact of the interrupter to supply electric energy to the circuit interrupter closing mechanism only while the interrupter is open and the relay is energized.

My invention will be better understood and further objects and advantages will be apparent from the following description taken in conjunction with the accompanying drawing in which:

Fig. l is a schematic circuit diagram of a network system utilizing a circuit interrupter whose closing may be controlled in accordance with my invention; and

Fig. 2 is a schematic representation of a circuit interrupter utilizing a closing control system in accordance with one embodiment of my invention.

Referring now to Fig. 1, I have shown a segment of a 3-phase alternating current secondary network system in order to illustrate one practical application for my improved circuit interrupter closing control system. The secondary network system is entirely conventional and will be described only briefly herein. A grid of interconnected cables, labeled secondary network in the drawing, is energized at utilization voltage from at least one primary feeder which is connected to the secondary network at a plurality of points, only one of which has been illustrated. Each interconnection between primary,

feeder and secondary network, as shown in the brokenline box 1 of Fig. 1, comprises four integral components: a 3-pole isolating switch 2; a 3-phase network transformer 3; a 3-pole electrically operated circuit interrupter 4; and three suitable back-up fuses 5.

The circuit interrupter 4 has been shown schematically and only partially in Fig. 1, the details having been omitted here for the sake of drawing simplicity. A mechanism particularly well suited for closing the interrupter is illustrated in Fig. 2 and will be fully described hereinafter. This closing mechanism, as well as the interrupter tripping mechanism which has not been shown, operates in response to closing and tripping signals supplied by suitable network relays represented in Fig. 1 merely as a solid-line rectangle 6.

The network relays 6 may be of any suitable type, such as, for example, the combination of elements which are illustrated, described and claimed in U. S. Patent 1,971,810 issued to David K. Blake on August28, 1934. By means of current transformers 7, 8 and 9, the network relays 6 are provided with energization proportional to the current flowing through the closed contactsof interrupter 4 or, when the interrupter is open, with energization proportional to the voltage across the open contacts, this voltage being reflected in the aforesaid current transformers from the associated transformer windings 7', 8', and 9 which are connected via resistors 10, 11 and 12, respectively, between opposite terminals of the 3-pole interrupter. By means of the connections shown in Fig. 1, the network relays are additionally provided with energization proportional to the secondary network voltage and proportional to the voltage across the secondary windings of the network transformer 3. The network relays 6 in combination with the circuit interrupter 4 form a so-called network protector.

The illustrated network protector operates automatically as follows: Should electric power flow in a direction from secondary network to primary feeder, such as during a short circuit or fault in a primary feeder, network relays 6 close an appropriate contact (not shown) to energize the tripping mechanism of interrupter 4 thereby opening the interconnecting circuit. The load circuits connected to the secondary network are now supplied solely from the sound primary feeders which remain connected to the secondary network. After the fault has been corrected and as soon as the secondary cally reclosi-ng the interrupter.- Electric power will now flow in the correct direction from primary feeder to secondary network. Whenever a secondary fault occurs, it will either burn itself clear or be isolated by suitable limiters (not shown) which are connected to the opposite ends of each section of secondary cable.

Turning now to Figure 2, I have shown schematically an electroresponsive closing mechanism for circuit interrupter 4. This closing mechanism, as illustrated by way of example, includes an electric motor driven, energy storing operating device indicated generally by the reference character 15. The operating device 15, which may be of the improved type fully disclosed and claimed in U. S. Patent 2,667,076 issued on January 26, 1954, to John A. Favre, comprises an energy accumulator in the form of a heavy coil compression spring 16 having its upper end fixed against a suitable abutment 17 and its lower end engaging a spring seat 18 that is pivotally connected by means of a pin 19 to operate a bell crank 20 upon release of the mechanical energy stored in spring 16. The bell crank 20 is fixed to a shaft 21 that carries an arm. 22 having a roller 23 mounted at the end thereof for engaging a closing member 24 of sequential closing linkages of the circuit interrupter 4.

The sequential closing linkages, which have been indicated in Fig. 2 generally by the reference character 25,

may bev of the improved type fully described and claimed in U. S. Patent 2,581,181, issued on January 1, 1952, to John A. Favre. As the energy stored in the compression spring 16 is released to rotate the bell crank 20 and thereby shaft 21 in a clockwise direction, roller 23 engages the. closing member 24 to tilt this member counterclockwise about its. intermediate pivotal point 26. Member 24 is moved to a position wherein a pin 27 carried by it is engaged by a holding latch 28 pivoted on a pin 29 and biased by a suitable spring 30 into latching relation in the path of pin 27.

In moving toward its latched position, closing member 24 exerts force through a toggle link 31 to pivot a main tension link 32 clockwise about a point 32a to position wherein switch contacts are closed. By means of the various linkages shown, main tension link 32 carries a movable main switch contact 33 and a movable arcing contact 34 from their open circuit or reset position shown in Fig. 2 to a closed circuit position wherein they engage cooperating stationary main switch contact 35 and stationary arcing contact 36, respectively. An insulating crossarm 37 disposed on main tension link 32 interconnects the similar main tension links of the other two poles (not shown) of the 3-pole interrupter 4.

Before the closing operation described above can take place, bell crank 20 must be rotated counterclockwise to compress the coil spring 16 and store mechanical energy therein. This is accomplished by means of a rotatable crank arm 38 which carries a cam roller 39 at its free end to constitute an orbital element revolving in an orbital path to engage with a flat cam surface 40 of the bell crank 20. Spring 16 is practically fully compressed when the crank arm 38 is moved to the substantially dead center angular position in which it is shown in Fig. 2, and further counterclockwise movement by the orbital element 'will carry it overcenter to release the energy stored in compressed spring 16 thereby closing the circuit interrupter as described. The crank arm 33 is fixedly mounted upon the end of a shaft 41 which is rotated by means of the improved difierential force amplifying overrunning drive mechanism 42 described and claimed in the aforementioned Patent 2,667,076. The mechanism 42 is arranged to be driven by a relatively small electric motor 43, and my. improved control system is, utilized to. control the energization' of this motor in accordance with the appropriate closing signal received from network relays 6.

As can be seen in Fig. 2, the closing control system includes an electromagnetic auxiliary relay or switching means 44 having an actuating coil 45, a normally open seal-in contact 46 and a normally open main contact 47. The seal-in contact is shunted by a manually operable push button control switch 48. The motor 43 is connected to a pair of electric energy supply terminals 49 and by means of a circuit formed by main contact 47 which is serially connected to a position indicating contact 51 of the circuit interrupter 4.

The position indicating switch or contact 51 is held in a first circuit controlling position with its contact closed against the force of a bias spring 52 by the main tension link 32 of the closing linkages 25 whenever this link is in its open position, as is shown in Fig. 2. Thus, position indicating contact 51 is actuated to a second circuit controlling position with its contact open as the movable contacts 33 and 34 of circuit interrupter 4 move. toward their closed circuit position. In accordance with my invention, the exact point at which contact 51 opens during a closing operation isnot critical, as long as it opens after the main tension link 32 begins its closing movement but before the movable contacts reach a fully closed position.

The actuating coil 45 and seal-in contact 46 of auxiliary relay 44 are connected in series circuit relationship between energizing terminal 49 and position indicating contact 51. In other words, coil 45 and contact 46 are connected across the series combination of driving motor 43 and auxiliary contact 47. The common connection between coil 45 and contact 46 is designated terminal 53. Actuating coil 45 may be conveniently selected to respond only to voltage of greater than a predetermined magnitude. This predetermined magnitude of voltage is sufficiently great to energize properly the driving motor 43.

The terminals 49, 50 and 53 shown in Fig. 2 are also indicated in Fig. 1. It will be observed that energizing terminals 49 and 50 are connected to the secondary windings of network transformer 3 which comprises the source of electric energy for activating the closing mechanism of interrupter 4. Terminal 53 is coupled to terminal 49 by means of the series connected contacts 13 and 14 of the network relays 6.

From the foregoing detailed description of the components and circuitry of my improved control system, its mode of operation may now be readily followed. To close the circuit interrupter 4, actuating coil 45 of auxiliary relay 44 is connected directly to the energizing terminal 49. This connection may be accomplished automatically by the closure of network relaycontacts 13 and 14 which are connected between terminals 49 and 53, or manually by the closure of control switch 48. In either case, the resulting shunting of seal-in contact 46 will complete the energizing circuit for the actuating coil 45 if the position indicating contact 51 is closed thus ensuring that the circuit interrupter 4 is in an open circuit condition. If the magnitude of voltage available at energizing terminals 49 and 50 is greater than the aforesaid predetermined magnitude, auxiliary relay 44 will operate to close its contacts 46 and 47. It will be noted that the auxiliary relay 44 will not operate during abnormally low voltage conditions, and thus driving motor 43 cannot be connected for energization by inadequate voltage.

The closure of seal-in contact 46 will retain actuating coil 45 energized until position indicating contact 51 opens. The closure of main contact 47 completes the circuit which includes contact 51 for energizing the closing motor 43 of the circuit interrupter closing mechanism, thereby initiating closing movement of the interrupter. Closing motor 43 operates through mechanism 42 to rotate crank arm 38 counterclockwise and compress the coil spring 16. Thus electric energy supplied to the closing mechanism is converted into mechanical energy which is stored in spring 16 and released as crank arm 38 moves past its dead center position. Release of this stored energy rotates bell crank 20 and shaft 21 in a clockwise direction to close the interrupter contacts 3336 as described hereinbefore. At some noncritical point during movement of the sequential closing linkages 25 to closed position, position indicating contact 51 simultaneously breaks the energizing circuits of driving motor 43 and auxiliary relay 44, and motor 43 will now come to rest in readiness for the next closing cycle. Should the interrupter 4 be tripped while contacts 13 and 14 of network relays '6 remain closed, the closing operation just described will immediately be repeated, and the interrupter will automatically reclose.

The force exerted by the closing mechanism on the movable interrupter contacts as they move toward their fully closed position is independent of the value of voltage supplied to the motor 43. If the interrupter were closed on a faulted secondary feeder thereby temporarily reducing the network transformer secondary voltage to a subnormal magnitude, the closing mechanism will never theless successfully complete its closing operation.

The period of time required to charge the closing mechanism during a closing operation, i. e., the time which elapses while spring 16 is being compressed, presents no problem in the illustrated application of my control system. Since the secondary network and primary feeder are interconnected through other network prorectors, not shown, these two electric circuits are already in synchronism, and delayed closing of interrupter 4 can be tolerated without any harmful effects.

While I have shown and described a preferred form of my invention by way of illustration, many modifications will occur to those skilled in the art, I contemplate, therefore, by the claims which conclude this specification to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a control system for an electric circuit interrupter having a movable switch member and an electroresponsive closing mechanism for moving the switch member from an open circuit to a closed circuit position, a relay actuatable when energized to close a contact, control means connected to energize said relay in controlled response to predetermined circuit conditions, and means including said contact responsive to the actuation of said relay to energize the closing mechanism and initiate circuit closing movement of the switch member, said closing mechanism energizing means including means operable in response to the closing movement of the switch member before reaching its closed circuit position to deenergize said closing mechanism.

2. In a system for controlling the energization of the closing mechanism of an electric switch having a posi tion indicating contact which is closed while the switch is in its open position and which opens during the closing operation of the switch before the switch is closed, first and second energizing terminals, means connecting the position indicating contact to 'said first energizing terminal, an auxiliary relay having an actuating coil and a first normally open contact serially interconnected between said position indicating contact and said second terminal, said first normally open contact being adapted to be shunted in order to initiate a closing operation, and circuit means including a second normally open contact of said auxiliary relay connecting the closing mechanism of the switch between said position indicating contact and said second terminal, whereby said second contact will close to activate said closing mechanism whenever said first normally open contact is shunted while the switch is open.

.3. In a system for controlling the closing of an elec-' trio circuit breaker provided with an energy storing overrunning closing mechanism including a motor, an energy accumulator having a rotatable cam driven by the motor for storing energy during a partial revolution of the cam and for releasing the energy stored during the remainder of the revolution of the cam, and sequential closing linkages driven by the energy accumulator to close the circuit breaker upon release of the stored energy: a position indicating contact coupled to the closing linkages and operable from a closed to an open circuit position in response to the closing movement of said linkages, a pair of energizing terminals, switching means having an actuating coil and first and second contacts which are closed when the actuating coil is energized, said first contact being connected in series circuit relationship with the closing mechanism and the position indicating contact between said energizing terminals to permit energization of said closing mechanism only when the circuit breaker is in an open circuit condition and said actuating coil is energized, said second contact being connected in series circuit relationship with said actuating coil and said position indicating contact between said energizing terminals, and means shunting said second contact to energize said actuating coil in controlled response to predetermined circuit conditions including the open circuit condition of said circuit breaker.

4. A control system for an electric switch having a closing mechanism which operates to convert electric energy into mechanical energy and to utilize said mechanical energy for closing the switch and including a position indicating contact which opens as the switch moves toward its closed circuit position during closing operation comprising, a pair of electric energy supply terminals, an electromagnetic relay having an actuating coil and including seal-in and main contacts which close when said actuating coil is energized, circuit means serially connecting said main contact, the closing mechanism and the position indicating contact between said terminals, means serially connecting said seal-in contact and said actuating coil across the series combination of said main contact and said closing mechanism, and connections for shunting said seal-in contact when closing operation is desired.

5. In a control system for an electric circuit interrupter having a switch member movable between open circuit and closed circuit positions and having a closing mechanism including electromechanical means for converting electric energy into mechanical energy and utilizing the mechanical energy to carry the switch member from open to closed circuit positions: switching means operable to initiate operation of the closing mechanism; an auxiliary relay including a normally open contact and an actuating coil; a position indicating switch actuatable from first to second circuit controlling positions in response to closing movement of said switch member before said switch member reaches its closed circuit position; said position indicating switch in its first circuit controlling position having connections with said switching means for energizing the actuating coil of said auxiliary relay in response to operation of said switching means and having other connections with said normally open contact for activating said electromechanical means upon operable energization of said actuating coil and for deactivating said electromechanical means upon actuation of said position indicat ing switch to its second circuit controlling position.

6. In a control system for an electric circuit interrupter having a switch member movable between reset and latched-closed positions and having a closing mechanism including electromechanical means for converting electric energy into mechanical energy and utilizing the mechanical energy to carry the switch member from reset to latched-closed positions: an auxiliary relay; first and second energizing circuits respectively operable to energize said electromechanical means and said auxiliary relay; means for rendering said second energizing circuit operative to energize said auxiliary relay; contact means responsive to operable energization of said auxiliary relay for rendering said first energizing circuit operative to energize said electromechanical means; a position indicating switch connected in both of said energizing circuits and operated by the closing movement of said switch member before said switch member reaches its latchedclosed position for rendering said energizing circuits inoperative and thereby deenergizing said electromechanical means andsaid auxiliary relay.

References Cited in the file of-this patent UNITED STATES PATENTS Kautz F 11111621,]1 '2 CIaZO Mar. 21, 193'3 Johnson- Dec. 2 194.1: Thurnin Feb. 24-, 1942' Couggeshall et a1. Jan. 5, 19.43

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