High-voltage switches with arc preventing or extinguishing devic – Arc preventing or extinguishing devices – Vacuum
Reexamination Certificate
1998-09-23
2001-12-18
Friedhofer, Michael (Department: 2832)
High-voltage switches with arc preventing or extinguishing devic
Arc preventing or extinguishing devices
Vacuum
C218S022000, C218S023000, C218S026000, C218S154000, C335S151000, C361S045000, C361S098000, C318S115000, C318S135000
Reexamination Certificate
active
06331687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and device for controlling electrical switchgear. More particularly, the invention relates to a method and device for controlling a switchgear utilizing a voice coil actuator to rapidly and positively open and close a current interrupter.
2. Description of Related Art
In a power distribution system, switchgear may be incorporated into the system for a number of reasons, such as to provide automatic protection in response to abnormal load conditions or to permit opening and closing of sections of the system. Various types of switchgear include a switch for deliberately opening and closing a power transmission line, such as a line to a capacitor bank; a fault interrupter for automatically opening a line upon the detection of a fault; and a recloser which, upon the detection of a fault, opens and closes rapidly a predetermined number of times until either the fault clears or the recloser locks in an open position.
Vacuum interrupters have been widely employed in the art because they provide fast, low energy arc interruption with long contact life, low mechanical stress and a high degree of operating safety. In a vacuum interrupter the contacts are sealed in a vacuum enclosure. One of the contacts is a moveable contact having an operating member extending through a vacuum seal in the enclosure.
SUMMARY AND OBJECTS
One of the objects of the present invention is to provide a switchgear actuator mechanism and control therefore that minimizes arcing and generated transients during opening and closing.
Another object of the present invention is to provide a switchgear actuator mechanism and control therefore that provides accurate monitoring of the system.
Another object of the present invention is to provide a switchgear actuator mechanism capable of a range of motion profiles, thereby eliminating the need for many types of mechanical systems.
Another object of the present invention is to provide a switchgear actuator mechanism capable of being controlled by any commercially available motor control circuitry or dedicated motion control circuitry.
Still another object of the present invention is to provide a switchgear actuator mechanism capable of procuring speeds and forces not readily achievable with prior art mechanical systems.
Still another object of the present invention is to provide an improved synchronously operating switchgear that results in a significant reduction in transients generated during the switching operation.
Generally, switchgear incorporating vacuum interrupters have utilized various spring loaded mechanisms which are connected to an operating member to positively open or close the interrupter contacts. One such device which is commonly used is the simple toggle linkage. The primary function of these mechanisms is to minimize arcing by very rapidly driving the contacts into their open or closed positions. Various applications may require the use of a number of spring loaded mechanisms with associated latches and linkages.
In order to prime these mechanical systems, either by compression or extension of the drive spring, an actuator is normally provided. These actuators can include, but are not limited to, solenoids, motors or hydraulic devices. In comparison to the inherent speed requirements of the interrupter to effectively interrupt current, these actuators are relatively slow with poor response times. For this reason they are not normally used to directly drive the interrupter contacts but are utilized to prime the fast acting spring mechanisms. The prime disadvantage of this system is that the spring driven operation does not lend itself to being easily controllable and it requires considerable engineering effort to finely adjust the mechanism's performance.
In practice, this means that many different mechanisms must be designed to accommodate the different operating requirements for switches, fault interrupters and reclosers and within each one of these switchgear classes, there are different mechanisms required depending on the application, including voltage and current requirements.
Furthermore, in view of the high voltages that are typically used in power applications, rapid and accurate movement of the interrupter contacts is desired to minimize arcing between the contacts and the generation of transients. Depending upon the application, whether it is capacitor bank switching or fault interruption, it can be determined by those skilled in the art when the most advantageous time to open or close the interrupter contact occurs. This optimum time correlates to a precise point on the voltage or current wave where current interruption or contact make would produce minimal arcing and transients. Since conventional spring driven mechanisms do not lend themselves to this degree of fine control, this invention offers a viable means to achieve point-on-wave or synchronous switching. Such synchronous operation of the interrupter is beneficial both in terms of the reduced wear on the interrupter contacts and the significant reduction in general transients experienced by the power system downstream of the switchgear unit.
A further feature of a controlled, synchronously operating switchgear unit is that the velocity at which the contacts close can be controlled. In conventional systems, the contacts are driven together in an uncontrolled fashion at very high velocity and it is possible that the contracts will bounce open a number of times before coming to rest. This bounce phenomenon is undesirable because the ensuing arcing can soften the contacts and create strong welds when the contacts finally mate.
In accordance with the present invention, a current interrupter includes a current interrupting device having at least one movable contact; an actuator coupled to the movable contact of the current interrupter; a feedback sensor for monitoring movement of the actuator; and a control system coupled to the feedback sensor so as to receive information from the feedback sensor concerning the movement of the actuator and for controlling movement of the actuator based on the information. The interrupter further includes a memory for storing a desired motion profile of the actuator; and a microprocessor for comparing the movement of the actuator with the desired motion profile and controlling movement of the actuator based also on a comparison of the movement of the actuator with the desired motion profile. The interrupter further includes a sensor for sensing a waveform of a voltage or current in a line to be switched and providing information concerning the waveform to the control system; wherein the control system controls the movement of the actuator based also on the information concerning the waveform.
The foregoing features and advantages of the present invention will be apparent from the following more particular description of the invention. The accompany drawings, listed hereinbelow, are useful in explaining the invention.
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Baranowski John F.
Dunk Michael P.
McCormick Garrett P.
Cooper Industries Inc.
Fish & Richardson PC
Friedhofer Michael
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