Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1998-12-28
2001-08-28
Hopf, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S057000, C702S061000, C361S093100, C361S093200, C361S063000
Reexamination Certificate
active
06282499
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to intelligent electronic devices, e.g., electronic trip units and protective relays. More specifically, the present invention relates to a method of detecting manual open (trip) or reclose operations in an intelligent electronic device.
Intelligent electronic devices are well known. By way of example, an electronic trip unit (one such intelligent electronic device) typically comprises voltage and current sensors which provide analog signals indicative of the power line signals. The analog signals are converted by an A/D (analog/digital) converter to digital signals which are processed by a microcontroller. The trip unit further includes RAM (random access memory), ROM (read only memory) and EEPROM (electronic erasable programmable read only memory) all of which interface with the microcontroller. The ROM includes trip unit application code, e.g., main functionality firmware, including initializing parameters, and boot code. The EEPROM includes operational parameters for the application code.
These electronic trip units have included a feature to count the number of trips by category, e.g., instantaneous, short time, long time, ground fault, or manual. However, not all manual trips are counted.
Manual trips are initiated via either remotely issued commands, or locally issued commands. Remotely issued commands are received as a network command by the trip unit and then executed. Locally issued commands are commands to open or close the breaker that are not processed by the trip unit, e.g., when an operator turns a breaker handle on or off manually, pushes a trip or reclose button or a trip or reclose signal is received via an auxiliary contact input to the breaker. Locally issued commands are not easily detected and therefore the resulting manual operations are not counted. Being able to count all breaker operations whether manual or automatic, locally or remotely generated is required to properly assess breaker contact wear.
BRIEF SUMMARY OF THE INVENTION
An electronic trip unit is described herein by way of example only, as the present invention applies to other intelligent electronic devices as well. The electronic trip unit comprising voltage and current sensors which provide analog signals indicative of the power line signals. The analog signals are converted by an A/D (analog/digital) converter to digital signals which are processed by a microcontroller. The trip unit further includes RAM (random access memory), ROM (read only memory) and EEPROM (electronic erasable programmable read only memory) all of which communicate with the microcontroller. The ROM includes trip unit application code, e.g., main functionality firmware, including initializing parameters, and boot code. The application code includes code for the manual trip detection algorithm of the present invention. The EEPROM includes operational parameters which may be stored in the trip unit at the factory, but can also be remotely downloaded.
In an exemplary embodiment of the invention, the manual operation detection algorithm detects manual operations initiated via remotely issued commands directly. Additionally, the algorithm detects manual operations initiated via locally issued commands when the following conditions are satisfied: (1) no trip or reclose event message has been issued by the trip unit within the reaction time required to operate the circuit breaker (trip/open); (2) current becomes zero on all phases of the line; and (3) voltage downstream (load side) from the circuit breaker becomes zero on all phases (reclose, voltage downstream (load side) from the circuit breaker goes from 0V on all phases to nominal voltage on all phases).
The present invention is useful in determining contact wear. Contact wear is directly proportional to the energy dissipated through the contacts as breakers are tripped. Additionally, some types of faults have more severe affects on contact wear than others, e.g., ground faults will wear down circuit breakers more quickly than manual trips. Therefore, it is advantageous to the analysis of contact wear that the present invention provides for a more accurate determination of the number of total trips per fault type by taking into account both the locally issued and remotely issued manual trips.
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Bui Bryan
Cantor & Colburn LLP
General Electric Company
Hopf Marc S.
Horton Carl B.
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