Power Line Reclosing via Phase Current Comparison
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Solution Overview
Problem
Current reclosing systems for power transmission lines face challenges in accurately detecting the arc ion extinguishing time, which is crucial for preventing accidents during reclosing, due to the need for highly accurate voltage detection that varies with the position of the accident on the line.
Innovation Solution
The system employs protection relays with metering voltage transformers to detect line voltages and calculate induced voltages using electrostatic and electromagnetic coupling, allowing for a reclosing command to be issued when the line voltage reaches a predetermined value within a allowable range, ensuring accurate detection of arc ion extinguishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the no-voltage time period is extended to ensure arc ion extinguishing, then reclosing reliability is improved, but system stability and productivity deteriorate due to prolonged interruption
Solution Approach 1:
The patent replaces the conventional voltage-based detection method with a current-based detection method. By monitoring the accident phase current and comparing it with normal phase currents, the system can accurately detect arc ion extinguishing without requiring extended no-voltage time periods. This substitution enables faster reclosing decisions while maintaining reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the protection relay continuously monitors the accident phase current and compares it with the normal phase currents. When the accident phase current becomes substantially equal to the normal phase currents, indicating arc ion extinguishing, the system provides feedback to trigger reclosing. This real-time feedback enables precise timing without prolonged interruptions.
2Device complexity
If conventional voltage detection methods are used to detect arc ion extinguishing, then detection simplicity is maintained, but measurement precision deteriorates due to high detection accuracy requirements varying with accident position
Solution Approach 1:
The patent changes the detection parameter from voltage to current. Instead of measuring voltage which requires high accuracy varying with accident position, the system measures current in the accident phase and compares it with currents in normal phases. This parameter change simplifies detection while maintaining precision because current comparison is inherently more robust to position variations.
Solution Approach 2:
The patent uses the currents from normal phases as reference copies to compare against the accident phase current. By copying the normal phase current characteristics and comparing them with the accident phase, the system achieves accurate detection without requiring complex voltage measurement systems, thereby simplifying the detection mechanism while maintaining precision.
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 approach enables precise detection of arc ion extinguishing time, preventing accidents during reclosing and stabilizing the power system by ensuring the line voltage is within a safe range before reclosing, thus enhancing system stability.
Implementation Method 1
employing protection relays with metering voltage transformers to detect line voltages
Implementation Method 2
calculate induced voltages using electrostatic and electromagnetic coupling
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A reclosing system for a power transmission line performs high-speed reclosing using protection relays (RY) each having a protection calculation function (Pro) and a reclosing function (Rec). The protection calculation function (Pro) is configured to receive voltage signals VL and current signals I detected at each terminal of the power transmission line to execute a predetermined protection calculation to thereby cut off a phase with an accident on the power transmission line. The reclosing function (Rec) is configured to output a reclosing command to a circuit breaker of a corresponding terminal when the phase with the accident becomes to satisfy a reclosing condition. If a line voltage VL measured at an accident phase of a power transmission line after the accident phase is cut off falls within an allowable range (∥VL|- |Vk∥< k1) determined based on a line voltage Vk assumed at the phase when the phase is normal, a reclosing command is sent to a circuit breaker corresponding to the accident phase.