Circuit Interrupter Supervisory Function for Fault Detection
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Solution Overview
Problem
Circuit interrupters, such as arc fault circuit interrupters (AFCIs), face challenges in maintaining consistent protection due to intermittent hardware errors, which can lead to 'nuisance trips' where the device incorrectly identifies normal loads as faults or fails to detect actual faults due to impaired circuitry, resulting in suboptimal protection.
Innovation Solution
A supervisory function is implemented in the trip circuit that monitors repetitive test functions and error conditions, setting a timer and accumulator to determine if the protective functions' availability falls below a threshold, triggering the trip mechanism only when necessary, thereby preventing false trips and ensuring adequate protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If repetitive test functions continuously monitor hardware circuits, then detection capability is improved, but false trips increase due to intermittent error conditions
Solution Approach 1:
The supervisory function performs preliminary assessment of error conditions by counting them over a predetermined time period before triggering a trip. This preliminary action distinguishes between transient errors that should be tolerated and persistent errors that indicate genuine faults, thereby reducing false trips while maintaining detection capability.
Solution Approach 2:
The supervisory function continuously monitors error conditions from repetitive test functions and uses this feedback to make intelligent decisions about tripping. By implementing a counting mechanism that accumulates error occurrences over time, the system adapts its response based on the frequency and persistence of errors, balancing detection sensitivity with operational reliability.
2Measurement precision
If continuous monitoring is implemented, then fault detection is improved, but device complexity increases
Solution Approach 1:
The supervisory function is designed to be multi-functional, serving both to monitor error conditions from repetitive tests and to make trip decisions. By consolidating these functions into a single supervisory mechanism that counts errors and determines tripping, the patent reduces overall complexity compared to having separate dedicated circuits for each function.
Data Source
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Figure 3A
AI summary
A circuit interrupter (2) for a power circuit (4) includes separable contacts (10), an operating mechanism (12) structured to open and close the separable contacts, and a trip circuit (14) cooperating with the operating mechanism to trip open the separable contacts. The trip circuit includes a number of hardware circuits (16,18,20,22,24,26,28,30,32,34) having a processor (34) with a number of routines (38,40,42). The routines provide a number of protective functions (38) structured (40) to detect a number of faults of the power circuit, a number of repetitive test functions for the number of hardware circuits, and a supervisory function (42) cooperating with the number of repetitive test functions. The supervisory function is structured to prevent availability of protection by the number of protective functions from falling below a predetermined threshold as a result of a plurality of intermittent error conditions of the number of hardware circuits.