Method for Determining a Relationship Between Two Sinusoidally Varying Quantities and Diagnostic Device

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This invention provides a method and diagnostic device for determining the relationship (specifically, the phase difference and amplitude ratio) between two periodic, sinusoidal signals, such as voltage and current in a cable. Instead of traditional frequency-domain transformations, it uses direct measurements to form complex number representations at synchronized time points, calculates their ratios, and uses the average of these ratios to accurately determine key electrical parameters even when the signal frequency or sampling intervals are not perfectly constant. The approach is especially useful for assessing the health of medium- or high-voltage power cables by measuring characteristics like the loss factor and impedance.

Use CasesContent extracted from patent full text and abstract with AI.

• Monitoring and diagnosing the condition and aging of medium- and high-voltage underground cables.
• Detecting insulation deterioration or faults in power transmission cables.
• Assessing the suitability of cables for continued use versus replacement.
• Improving power grid reliability through precise cable diagnostics.
• Laboratory analysis of cable materials or setups where accurate loss factor measurements are needed.
• Quality control in cable manufacturing by evaluating electrical properties.

BenefitsContent extracted from patent full text and abstract with AI.

• Significantly higher precision and accuracy in determining phase relationships and related electrical properties, compared to prior methods.
• Improved robustness against variations in signal frequency, waveform distortion, noise, and non-uniform sampling times.
• Does not require precise knowledge or control of the system's fundamental frequency, reducing setup complexity and errors.
• Faster result availability, as accurate measurements can be made using as little as a quarter-period of the signal.
• Enables practical, automated, and digital diagnostics for in-field cable monitoring.
• Reduces the risk of undetected cable aging or degradation, improving safety and reliability of electrical infrastructure.

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Patent Abstract

In order to determine a phase ratio between two predominantly sinusoidally varying variables, respective measurement values for the two variables are expanded into complex numbers, then a ratio variable c[k] is calculated directly from these complex numbers, the average c of all ratio variables is determined, and then a statement about the ratio between the two variables can be made on the basis of this average. The invention is particularly suitable when the loss factor for a medium or high-voltage cable is to be determined.