Circuit Breaker Current-Slope Detection for Inrush False Trips
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Solution Overview
Problem
False triggering of circuit breakers during start-up of equipment with capacitive or inductive loads is a common issue, particularly in DC grids, and existing circuit breakers have fixed protection levels that cannot be adjusted without reinstallation.
Innovation Solution
A digital real-time algorithm that samples incoming current to distinguish between short-circuit events and inrush currents by determining changes in slope, allowing for dynamic reconfiguration of circuit breaker settings to prevent false triggering and maintain protection during real short-circuit events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the circuit breaker uses a fixed protection level, then the CB structure is simple and reliable, but the CB cannot adapt to different load conditions and causes false triggering during start-up
Solution Approach 1:
The circuit breaker implements dynamic protection levels through a digital controller that continuously monitors incoming current and adjusts the trip threshold in real-time. The controller increases the protection level during start-up periods when inrush currents are expected, then returns to normal operation, enabling the CB to adapt to varying load conditions without physical modification
Solution Approach 2:
The invention changes the electrical parameter of the protection level dynamically based on operating conditions. The digital controller modifies the trip current threshold parameter according to the detected load state, using algorithms that distinguish between normal inrush currents and actual fault conditions, thereby preventing false triggering while maintaining protection
2Reliability
If the CB trips immediately on current threshold exceedance, then the protection response is fast, but the CB causes false triggering during capacitive/inductive load start-up
Solution Approach 1:
The digital controller performs preliminary analysis of the current waveform characteristics before triggering a trip. By examining the rate of change and pattern of the incoming current, the controller can predict whether an exceedance is due to normal start-up or a actual fault, allowing it to prepare appropriate response actions and avoid false tripping
Solution Approach 2:
The system implements feedback by continuously monitoring the incoming current and comparing it against dynamic thresholds. The controller uses the detected current characteristics to adjust the protection level in real-time, creating a closed-loop system that learns from operating patterns and distinguishes between harmless inrush currents and dangerous fault conditions
3Adaptability or versatility
If the CB protection level is changed by reinstallation, then the protection level is fixed and reliable, but the reinstallation process is time-consuming and costly
Solution Approach 1:
The invention replaces the mechanical reinstallation process with a digital control system. Instead of physically changing the circuit breaker or its components to alter protection levels, the system uses a digital controller with software algorithms that can dynamically adjust the protection characteristics through electrical signals, eliminating the need for time-consuming reinstallation
Data Source
AI summary
Described is a method of identifying a short-circuit (SC) like event in a circuit breaker (CB). The method comprises sampling an incoming current to the CB to determine a maximum value of a slope of a curve of the incoming current. The method includes sampling the incoming current again before a level of the incoming current reaches a predetermined, preset, selected, or calculated SC threshold value THSC for the CB. The method involves determining from the sampled incoming current that a value of the slope of the incoming current has changed from its maximum slope value to a lower slope value to thereby determine that the incoming current is indicative of a SC like event and does not comprise a real SC event.