Circuit Interrupter Phase Synchronization Nuisance Trip Reduction
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Solution Overview
Problem
Circuit interrupters, such as residential circuit breakers, often experience nuisance trips due to improper phase synchronization with alternating current power circuits, leading to unnecessary interruptions of power circuits, especially when the line frequency or processor timer frequency varies outside acceptable tolerances.
Innovation Solution
A circuit interrupter system that includes sensors to detect zero crossings and a processor with a timer to synchronize with the power circuit's phase, determining the number of samples of electrical characteristics in phase synchronization with zero crossings and generating a trip signal when frequency ratios exceed predetermined values, thereby minimizing nuisance trips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the processor captures critical system data at fixed timer intervals, then the processor operation is simple and regular, but the data may be collected at improper phase angles relative to the line-to-neutral voltage causing nuisance trips
Solution Approach 1:
The system uses zero-crossing detection to provide feedback about the actual phase angle of the voltage waveform. This feedback allows the processor to adjust its sampling timing dynamically, ensuring that critical data is always captured at the correct phase angles regardless of frequency variations, thus preventing nuisance trips while maintaining reliable operation
Solution Approach 2:
The system transitions from static fixed-interval sampling to dynamic phase-synchronized sampling. The sampling intervals are continuously adjusted based on the detected zero-crossing events, allowing the system to adapt to frequency variations and maintain accurate phase alignment with the voltage waveform
2Stability of the object's composition
If the processor uses a fixed timer frequency, then the timing is simple and stable, but the phase synchronization with the power circuit becomes improper when line frequency varies outside acceptable tolerances
Solution Approach 1:
The system maintains a stable fixed timer frequency for reliable processing while dynamically adjusting the interpretation and utilization of timer counts based on detected zero-crossing events. This allows the system to maintain internal timing stability while achieving external phase synchronization with the power circuit, even when line frequency varies
Solution Approach 2:
The zero-crossing detection circuit acts as an intermediary between the fixed-frequency processor timer and the variable-frequency power circuit. By detecting zero-crossing events and using these as reference points, the system bridges the frequency mismatch and achieves accurate phase synchronization without changing the processor's internal timer frequency
3Reliability
If the system trips on every frequency deviation, then hazardous conditions are detected promptly, but normal operation is interrupted unnecessarily due to frequency variations within tolerances
Solution Approach 1:
The system uses a threshold-based approach where frequency deviations are monitored continuously, but tripping action is taken only when deviations exceed predetermined tolerance thresholds. This partial action approach filters out normal frequency variations while still detecting and responding to hazardous conditions that exceed acceptable limits
Solution Approach 2:
The system continuously monitors the relationship between timer counts and zero-crossing events, providing feedback about frequency deviations. This feedback enables the system to distinguish between normal frequency variations within tolerances and hazardous conditions exceeding tolerances, triggering trips only when necessary
Data Source
AI summary
A circuit breaker includes a line terminal, a load terminal, separable contacts electrically connected in series between the terminals, a neutral conductor, and an operating mechanism structured to open and close the contacts and trip open the contacts in response to a trip signal. A first sensor senses an electrical characteristic operatively associated with the contacts. A second sensor detects zero crossings, a consecutive pair of the crossings defining a corresponding half-cycle and a first frequency. A processor cooperates with the sensors and includes a routine and a timer having a second frequency. The routine determines, for each of the half-cycles and responsive to the timer, plural samples of the sensed electrical characteristic in a phase synchronized relationship to a corresponding one of the crossings, and determines whether one of the frequencies exceeds a number of corresponding predetermined values for a number of times and responsively outputs the trip signal.