Overcurrent Protection Thermal Loading Estimation
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Solution Overview
Problem
Existing overcurrent protection systems face issues with nuisance tripping due to thermal characteristics of fuses, inaccuracies in current measurements caused by limited ADC resolution, and inadequate consideration of thermal loading in electrical systems, leading to unwanted isolation of critical loads.
Innovation Solution
A system comprising a current sensor, controller, and isolation device that estimates accumulated thermal loading and provides a signal to interrupt current if it exceeds a predetermined maximum, allowing for advanced overcurrent sensing and selective isolation of circuits to prevent unwanted operations and improve accuracy in current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fuses are used for overcurrent protection, then fast acting protection is achieved, but nuisance tripping occurs on temporary overloads
Solution Approach 1:
The system performs preliminary thermal modeling and predicts future thermal states before actual overheating occurs. By calculating accumulated thermal loading in advance and comparing it against thresholds, the system can take preventive action (issuing warnings or controlling loads) before the fuse would trip, thereby avoiding nuisance tripping while maintaining fast protection capability.
Solution Approach 2:
The system continuously monitors current draw, calculates thermal loading based on historical data and thermal characteristics, and uses this feedback to predict future thermal states. This closed-loop feedback mechanism allows the system to distinguish between temporary overloads that will self-correct and genuine dangerous conditions, preventing nuisance tripping while maintaining reliable protection.
2Device complexity
If ADC resolution is limited, then device complexity is reduced, but current measurement accuracy deteriorates
Solution Approach 1:
The system introduces thermal modeling as an intermediary layer between the limited-resolution ADC measurements and the overcurrent protection decision. Instead of relying solely on raw current measurements, the thermal model processes the measurements over time, accumulating thermal effects and providing a more accurate representation of the actual thermal state, thereby compensating for the limited ADC resolution.
Solution Approach 2:
The system transforms the current measurement parameter from instantaneous current values to accumulated thermal loading parameters. By integrating current measurements over time and applying thermal characteristics, the system converts limited-resolution instantaneous measurements into more accurate thermal state assessments, effectively improving measurement precision without increasing ADC resolution.
3Reliability
If main circuit breaker isolates all circuits, then system-wide protection is achieved, but critical loads are unnecessarily isolated
Solution Approach 1:
The system segments the electrical system into individual circuit-level thermal models, each with its own thermal characteristics and loading patterns. This segmentation allows the controller to identify and manage specific problematic circuits independently, taking corrective action only where needed rather than isolating the entire system, thereby maintaining critical load availability while providing system-wide protection.
Solution Approach 2:
The system applies different thermal models and protection strategies to different circuits based on their specific characteristics and criticality. By localizing the thermal analysis and protection control to individual circuits or groups, the system can maintain critical loads that have different thermal characteristics or higher priority, while applying protective isolation only to non-critical circuits experiencing problematic thermal loading.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively prevents nuisance tripping and improves accuracy in overcurrent protection by estimating thermal loading and selectively isolating circuits, reducing the risk of critical load isolation and enhancing the overall reliability of electrical systems.
Implementation Method 1
a current sensor configured to sense a current in a circuit protective device and to generate a signal corresponding to the sensed current
Implementation Method 2
a fuse includes a metal wire or strip that will melt when heated by a predetermined amount of electrical current
Implementation Method 3
The amount of time that the fuse will carry an overcurrent decreases as the magnitude of the current increases
Data Source
AI summary
In one aspect, the invention provides a method for overcurrent sensing including; generating an analog output signal representative of a sensed AC current, generating a digital representation of the analog output signal using a plurality of discrete samples, determining those of the plurality of discrete samples having a substantially identical magnitude and estimating an amount of overcurrent in the sensed AC current by evaluating those of the plurality of discrete samples that have the substantially identical magnitude. In some embodiments, the substantially identical magnitude is a maximum magnitude represented by the digital representation.