Signal Conditioning Circuit for Rogowski Coil Power-Up Transients
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Solution Overview
Problem
Rogowski integrator circuits in protective relay applications exhibit transient states at power up, causing electrical stress due to high gain at low frequencies and stabilization time, which complicates the installation and operation of flexible current sensors like Rogowski coils.
Innovation Solution
A signal conditioning circuit that includes an integrator circuit, a time delay circuit to control an analog switch, and a power stage circuit, which isolates the power stage from the integrator during transient states and connects it once steady, along with a temperature detector to manage power stage temperature, ensuring safe and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Rogowski integrator circuit is used to process the output signal from a Rogowski coil, then the current waveform can be obtained, but the circuit presents a transient state at power up causing electrical stress on components
Solution Approach 1:
The time delay circuit generates a delay signal that activates the first analog switch before the integrator circuit completes its transient stabilization. This preliminary action prevents the power stage circuit from being exposed to the harmful transient state, allowing the integrator to stabilize first before signal transmission begins.
Solution Approach 2:
The first analog switch acts as an intermediary component between the integrator circuit and the power stage circuit. It conditionally connects or disconnects based on the transient state, mediating the signal flow to prevent electrical stress while maintaining normal operation when stable.
2Ease of operation
If flexible current sensors like Rogowski coils are used instead of traditional heavy rigid-body current sensors, then installation convenience is improved, but the circuit complexity increases due to the need for Rogowski integrator circuits
Solution Approach 1:
The signal conditioning circuit integrates multiple functions including transient state detection, conditional signal transmission, and temperature monitoring within a unified circuit architecture. This multi-functionality manages the complexity by consolidating control mechanisms rather than adding separate independent systems.
Solution Approach 2:
The circuit employs dynamic control through analog switches that automatically adjust their conduction state based on real-time conditions (transient detection and temperature monitoring). This dynamic adaptation simplifies operation while maintaining precise control over the signal path.
3Productivity
If the power stage circuit is continuously connected to the integrator circuit, then signal transmission is maintained, but electrical stress occurs during transient states
Solution Approach 1:
The circuit implements periodic connection and disconnection of the power stage to the integrator based on operational conditions. The first analog switch periodically enables or disables signal transmission according to the transient state, maintaining productivity when stable while protecting reliability during transient periods.
Data Source
AI summary
A signal conditioning circuit for monitoring at least one parameter of an electrical signal in an electrical conductor. The signal conditioning circuit can include an integrator circuit having an input for receiving a signal from a current sensor coupled to the electrical conductor. A first analog switch has an input coupled to the output of the integrator circuit, wherein the first analog switch is controlled by the output of a time delay circuit. A power stage circuit has an input coupled to the output of the first analog switch. The signal conditioning circuit can be used for line fault detection.