Rogowski Coil Current Sensing via Frequency Domain Processing
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Solution Overview
Problem
Existing electrical power systems face challenges in accurately sensing and measuring current conditions due to signal distortion in current transformers and the need for complex signal processing to interface Rogowski coil outputs with digital equipment, leading to increased costs and reliability issues.
Innovation Solution
A protective relay system utilizing Rogowski coils that represents current flow in the frequency domain without determining integrals in the time domain, eliminating the need for complex filters and providing accurate current indications, thereby simplifying the system and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Rogowski coils are used for current sensing, then measurement precision is improved, but device complexity increases due to the need for complex signal processing and integration circuits
Solution Approach 1:
The patent extracts the integration function from the time domain and relocates it to the frequency domain through Fourier transformation. This separates the sensing function (performed by the simple Rogowski coil) from the integration function (performed digitally in the frequency domain), thereby reducing analog circuit complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces the mechanical/analog integration circuit with a digital signal processing approach. Instead of using analog integrators and filters, the system uses digital Fourier transformation and frequency-domain calculations, substituting physical electronic components with computational algorithms.
2Measurement precision
If time-domain integration is used to process Rogowski coil output, then current measurement is achieved, but loss of time occurs due to computational demands and processing delays
Solution Approach 1:
The patent transitions the integration operation from the time dimension to the frequency dimension. By applying Fourier transformation, the system operates in the frequency domain where integration becomes a simple division by frequency, dramatically reducing computational complexity and processing time compared to time-domain numerical integration.
Solution Approach 2:
The patent changes the operational parameters of the integration process by transforming the signal representation from time-domain samples to frequency-domain spectral components. This parameter transformation allows the integration operation to be performed more efficiently through algebraic operations rather than iterative numerical methods.
3Measurement precision
If complex filters are implemented for signal processing, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent substitutes physical filter circuits with digital signal processing algorithms. Instead of implementing analog low-pass, high-pass, or band-pass filters with multiple capacitors and inductors, the system uses digital filtering through frequency-domain multiplication and inverse Fourier transformation, eliminating complex passive component networks.
Solution Approach 2:
The patent implements a universal frequency-domain processing framework that can perform multiple functions (integration, differentiation, filtering, RMS calculation) through a single set of mathematical operations. This multi-functional approach replaces multiple specialized analog circuits with one versatile digital processing pipeline.
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 allows for accurate and reliable detection of current conditions without the need for time-domain integration, reducing costs and computational demands while maintaining high precision, enabling faster computing times and effective fault detection in electrical power systems.
Implementation Method 1
a Rogowski coil generating an output voltage signal corresponding to current flow in the current path
Data Source
AI summary
Relay devices, systems and methods for obtaining an accurate representation of a current monitored with a Rogowski coil, without integration of the Rogowski coil output voltage signal in the time domain.