Measuring and testing – Testing of apparatus
Reexamination Certificate
1999-03-12
2001-09-11
Raevis, Robert (Department: 2856)
Measuring and testing
Testing of apparatus
Reexamination Certificate
active
06286377
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to testing of the mechanical operation of spring powered switches such as medium voltage circuit breakers.
2. Background Information
Switches carrying sizable electric currents, such as medium voltage circuit breakers, require substantial mechanical forces to operate the switch rapidly and to hold the contacts closed against the magnetic repulsion forces generated by the current. In a typical medium voltage circuit breaker, a set of charged closing springs is released to close the breaker and to charge an opening spring which, in turn, is later released to open the breaker. The speed at which the mechanism operates is so rapid that it is difficult to identify the nature of any malfunctions, or even in some cases, to discern that the breaker is not operating properly.
Under typical practice, a skilled engineer is dispatched to the field or the circuit breaker must be returned to the factory to determine the cause and remedy for a malfunction or inferior performance. Due to the high inertia developed in the operating mechanism, there is considerable overshoot and distortion of the parts during operation. Often, analysis, which typically is performed using an expensive camera system, is qualitative rather than quantitative (e.g., it is determined that there is excessive overshoot, but no measurement of the amount of overshoot is provided). This technique for analyzing the operation of such switches is expensive and time consuming, and is highly dependent upon the skill and experience of the tester.
U.S. Pat. No. 5,726,367 discloses a method and apparatus for testing the operation of a spring powered switch mounted in a support frame and operated by an operating mechanism having driven parts actuated by release of charged springs. A recording medium, such as a tape, is applied to one of the driven parts. A fixture mounted to the support frame adjacent the selected driven part supports a marking instrument in contact with the recording medium at a fixed point relative to the support frame. When the charged spring is released, the selected driven part, which carries the recording medium, moves relative to the marking instrument. This produces a trace on the recording medium representing the movement of the selected driven part relative to the fixed point. This trace provides a quantitative record of the movement of the selected driven part which can be used to analyze the performance of the operating mechanism of the switch.
N. Anger et al., “Diagnostics/Monitoring for Medium-Voltage Components and Systems”, pp. 1.14.1-1.14.4, discloses the detection of the angle of rotation curve for the breaker shaft of a vacuum circuit breaker's spring-stored-energy operating mechanism. An expert circuit breaker diagnostic system employs temperature sensors, current transformers, and an angle resolver to provide temperatures, opening and closing solenoid coil currents and charging motor currents, and shaft angles to a microprocessor in a continuous on-line operation. Trend analyses are performed using parameters of individual past switching operations with the aid of temperature, voltage and time-compensated classification models.
Although it is known to employ mechanical or electronic sensors for sensing movement of certain operating mechanism components to test a circuit breaker, there remains a need, however, for an improved method and apparatus for accurately testing spring operated switches.
There is a more particular need for such an improved method and apparatus which can be easily used by unskilled personnel.
There is another more particular need for such an improved method and apparatus which is inexpensive and can, therefore, be economically repeated frequently.
SUMMARY OF THE INVENTION
These needs and others are satisfied by the invention which is directed to a method and apparatus for testing the operation of a spring powered switch operated by an operating mechanism having a plurality of driven parts actuated by release of a charged spring. At least one sensor is employed to determine a plurality of variable linear positions of at least one of the driven parts. Operation data is collected for the operating mechanism including the linear positions of the at least one of the driven parts. The operation data is output.
As one aspect of the invention, a method of testing a spring powered switch comprises the steps of: selecting at least one of an operating mechanism's driven parts having a variable linear position, and releasing the operating mechanism's charged spring to actuate the driven parts and to produce linear movement of the selected at least one of the driven parts. At least one sensor is employed to determine a plurality of the linear positions of the selected at least one of the driven parts. Operation data is collected for the operating mechanism including the linear positions of the selected at least one of the driven parts. The operation data is output.
In one embodiment of the invention, a vacuum interrupter stem is employed as the selected one of the driven parts. Motion with respect to time of the vacuum interrupter stem is monitored.
In another embodiment of the invention, a push rod is employed as the selected one of the driven parts. Motion with respect to time of the push rod is monitored.
Preferably, at least one LVDT transducer is employed as the at least one sensor.
As another aspect of the invention, an apparatus for testing a spring powered switch includes a linkage to at least one of an operating mechanism's driven parts having a variable linear position. At least one sensor engages the linkage to determine the linear position of the selected at least one of the driven parts. A means collects operation data for the operating mechanism when the charged spring is released to actuate the driven parts and produce linear movement of the at least one of the driven parts. The operation data includes a plurality of the linear positions of the at least one of the driven parts. A means outputs the operation data.
REFERENCES:
patent: 3183599 (1965-05-01), Byrd et al.
patent: 5671161 (1997-09-01), Bennet et al.
patent: 5726367 (1998-03-01), Patel et al.
Berger et al., “Maintenance-Free Vacuum Circuit-Breaker”, The Reliability of Transmission and Distribution Equipment, IEEE Conference Publication No. 406, 6 pp., Mar. 29-31, 1995.
N. Anger et al., “Diagnostics/Monitoring for Medium-Voltage Components and Systems”, pp. 1.14.1-1.14.4, No date.
Benke James J.
Davis Norman
Marchand Francois J.
Patel Nagar J.
Eaton Corporation
Moran Martin J.
Raevis Robert
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