Fault Current Detection Circuit with Segmented Transformers
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Solution Overview
Problem
Conventional high-speed fault current detection circuits face reduced detection accuracy for fault currents due to the significant difference in size between fault and surge currents, affecting the overall reliability of the system.
Innovation Solution
A high-speed fault current detection circuit is designed with a primary current transformer and a pair of secondary current transformers, along with separate fault and surge detection circuit sections, amplifiers, and differentiators, to accurately distinguish and detect fault and surge currents using comparative and trip determination units, enhancing detection accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common secondary current transformer and common amplifier circuit section are used to detect both fault currents and surge currents, then the device complexity is reduced, but the detection accuracy of fault currents is reduced due to the significant size difference between surge currents and fault currents
Solution Approach 1:
The patent divides the detection circuit into separate fault detection and surge detection sections, each with dedicated current transformers and amplifier circuits. This segmentation allows independent optimization of detection parameters for each current type, resolving the contradiction between device simplicity and detection accuracy.
Solution Approach 2:
The patent applies different detection characteristics to different detection sections: the fault detection section uses settings optimized for small fault currents, while the surge detection section uses settings optimized for large surge currents. This local quality approach allows each section to perform its specific function accurately without being compromised by the other current type.
2Measurement precision
If the detection sensitivity is increased to detect small fault currents, then the fault current detection accuracy is improved, but the surge current detection becomes unreliable due to signal saturation
Solution Approach 1:
By separating the detection paths into independent fault detection and surge detection sections, the patent allows each section to have its own sensitivity settings. The fault detection section can use high sensitivity for small currents, while the surge detection section can handle large currents without saturation, thus resolving the contradiction between sensitivity and reliability.
Solution Approach 2:
The patent changes the detection parameters (amplifier gain, threshold settings) for different detection sections based on the expected current magnitude. Fault detection uses high gain for small signals, while surge detection uses lower gain for large signals, preventing saturation and maintaining reliability across different current types.
3Measurement precision
If separate detection sections with different amplification ratios are used for fault and surge currents, then the detection accuracy for both current types is improved, but the device complexity increases
Solution Approach 1:
The patent implements separate detection sections with dedicated current transformers and amplifier circuits for fault and surge detection. This segmentation, while increasing component count, allows independent optimization of detection parameters and provides reliable detection for both current types, justifying the increased complexity through improved performance.
Solution Approach 2:
The patent designs the detection system to handle multiple current types (fault currents and surge currents) with vastly different magnitudes through a unified architectural framework. While separate sections are used, they share common control logic and trip determination mechanisms, providing multi-functionality that justifies the structural complexity.
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 solution effectively enhances the detection accuracy of fault currents exceeding rated values and accurately identifies surge currents, improving the reliability of fault current detection and enabling timely trip operations to prevent mechanical and thermal stress on electric power devices.
Implementation Method 1
a primary current transformer configured to detect a current flowing through an electric power circuit in a grid to output a current detection signal
Implementation Method 2
a pair of secondary current transformers connected to the primary current transformer to convert and provide the current detection signal provided by the primary current transformer into secondary conversion signals, respectively, with a small current
Data Source
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AI summary
A fault current detection circuit according to the invention comprises a primary current transformer that detects a current; a pair of secondary current transformers that convert a current detection signal into secondary conversion signals with a small current; a fault detection circuit section that determines whether or not a fault current occurs by comparing a current value according to a secondary conversion signal with a predetermined reference current value; a surge detection circuit section that determines whether or not a surge current occurs on the electric power circuit; and a trip determination unit that receives a fault detection signal and a surge detection signal, and generates a trip control signal when at least either one of the fault detection signal and the surge detection signal is received.