Circuit Breaker Impedance-Based Fault Classification
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Solution Overview
Problem
Current circuit breakers face strain and potential breakdowns due to repeated exposure to permanent faults, as they are not equipped to handle prolonged current and voltage levels, and it is challenging to differentiate between temporary and permanent faults during disconnection.
Innovation Solution
A circuit breaker that injects a test signal at a main frequency into a disconnected power line to measure impedance to ground, analyzing it against a reference threshold to determine fault permanence, allowing re-closing only for temporary faults and keeping the circuit open for permanent faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the circuit breaking element is re-closed after opening due to a fault, then temporary faults can be resolved and power supply restored, but permanent faults cause repeated opening and closing that strain the equipment
Solution Approach 1:
The control unit performs preliminary impedance measurement and fault classification before re-closing the circuit breaker. By injecting a test signal and measuring the impedance of the power line during the disconnection time interval, the system determines whether the fault is temporary or permanent before attempting to re-close, thereby avoiding repeated operations on permanent faults that would strain the equipment
Solution Approach 2:
The system uses feedback from impedance measurement to control the re-closing decision. The control unit continuously monitors the impedance characteristics of the power line and uses this feedback information to determine whether to permit re-closing, creating a closed-loop control system that adapts to the actual fault condition
2Reliability
If the circuit breaking element remains open for extended periods to avoid equipment strain, then permanent faults are prevented from causing damage, but temporary faults also experience unnecessary power interruption
Solution Approach 1:
The system performs preliminary fault classification through impedance measurement during the disconnection time interval. By determining the fault type before the full disconnection time elapses, the system can restore power sooner for temporary faults while maintaining extended open position for permanent faults, thereby reducing unnecessary power interruption time without compromising equipment safety
3Measurement precision
If impedance measurement is performed during the disconnection time interval, then fault type can be determined accurately, but the complexity of the control system increases
Solution Approach 1:
The control unit is designed to perform multiple functions: fault detection, impedance measurement, fault classification, and re-closing control. By making the control unit multi-functional, the patent avoids adding separate dedicated devices for each function, thereby achieving accurate fault type determination while minimizing the increase in overall system complexity
Solution Approach 2:
The control unit uses the existing disconnection time interval (which occurs naturally during circuit breaker operation) to perform impedance measurement. Rather than requiring additional measurement time or external assistance, the system utilizes its own operational characteristics to gather the necessary diagnostic information
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
This solution reduces equipment strain by accurately distinguishing between temporary and permanent faults, enabling controlled re-closing for temporary faults and preventing unnecessary stress on the power supply system, while allowing for quicker fault location and service actions.
Implementation Method 1
determine an impedance to ground of the power line from the response voltage and the response current
Data Source
Figure 1~2
Figure 3
AI summary
The present invention concerns a circuit breaker (18) for protecting a power line (14). The circuit breaker (18) includes a control unit (26) and a circuit breaking element (20) disconnecting the power line (14) from a power source. The control unit (26) detects a fault on the power line (14), opens the circuit breaking element (20), which opening starts a disconnection time interval, injects a test signal (t(f)) into the power line, measures a response (U(f)), (I(f)), determines an impedance of the power line (14) from the response (U(f)), (I(f)), analyses the impedance during the time interval based on comparing the impedance with a reference threshold, determines a permanent or a temporary fault based on the analysed impedance, re-closes the circuit breaking element (20) after the time interval if the fault is temporary and keeps the circuit breaking element (20) open after the time interval if the fault is permanent.