Distance Protection Reach-Point Voltage for Distorted Fault Waveforms
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Solution Overview
Problem
Conventional distance protection methods for electrical transmission lines struggle to accurately identify fault types due to distorted fault current waveforms and higher harmonic components, especially when variable renewable sources like DFIGs are connected.
Innovation Solution
The method involves obtaining measurements of electrical parameters at a first location on the transmission line, determining these parameters in the time-domain for a second location, transforming them into the frequency-domain, and using these transformed parameters to control or protect the transmission line, thereby minimizing calculation errors caused by wave distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional distance protection methods are used, then the protection system can operate with simple calculation based on Ohm's law, but the measurement precision deteriorates due to distorted fault current waveforms and harmonic components from variable renewable sources
Solution Approach 1:
The patent transforms the calculation from using distorted time-domain voltage and current measurements directly to using frequency-domain parameters obtained through Fourier transformation. This parameter transformation allows the system to extract fundamental frequency components from distorted waveforms, thereby maintaining measurement precision while working with complex renewable source connections
Solution Approach 2:
The patent introduces an intermediary processing step (Fourier transformation) between the raw measurements and the final impedance calculation. This intermediary transforms the distorted time-domain signals into clean frequency-domain parameters, enabling accurate distance protection measurements even when variable renewable sources introduce harmonics and waveform distortions
2Adaptability or versatility
If variable renewable sources like DFIGs are connected to the transmission line, then the system can utilize renewable energy, but the measurement precision deteriorates due to distorted fault current waveforms and higher harmonic components
Solution Approach 1:
The patent applies parameter transformation by converting distorted time-domain measurements into frequency-domain parameters through Fourier transformation. This allows the protection system to accurately extract fundamental frequency components even when variable renewable sources introduce harmonics and waveform distortions, thereby maintaining measurement precision while supporting renewable energy integration
Solution Approach 2:
The patent converts the harmful effect of waveform distortion and harmonics into a benefit by using Fourier transformation to selectively extract the fundamental frequency components. The distortion that would normally degrade measurement accuracy is transformed into a situation where the fundamental components can be cleanly separated and used for accurate protection calculations
3Speed
If measurements are taken during fault period with variable renewable sources, then the system can detect faults in real-time, but the measurement precision deteriorates because voltages and currents do not have the same frequencies
Solution Approach 1:
The patent introduces Fourier transformation as an intermediary step that processes the multi-frequency voltage and current measurements during the fault period. This transformation converts the measurements into the frequency domain, allowing the system to separately identify and use fundamental frequency components for impedance calculation, thereby maintaining both real-time detection capability and calculation accuracy
Solution Approach 2:
The patent changes the parameter domain from time-domain measurements to frequency-domain parameters through Fourier transformation. This parameter change enables the system to handle the frequency mismatch issue by extracting fundamental frequency components, ensuring accurate impedance calculation even when voltages and currents have different frequencies during fault conditions
Data Source
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AI summary
The present disclosure relates to a method for controlling or protecting the transmission line within an electrical system comprising a transmission line, the method comprising: obtaining measurements of a first at least one electrical parameter being measured at a first location on the transmission line of the electrical system; determining, in a time-domain, a second at least one electrical parameter for a second location on the transmission line of the electrical system based on the measurements of the first at least one electrical parameter; determining, in a frequency-domain, a third at least one electrical parameter for the second location on the transmission line of the electrical system based on the second at least one electrical parameter; and controlling or protecting the transmission line within the electrical system based on the third at least one electrical parameter.