Cable Impedance Monitoring via Phase Amplitude Modulation
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Solution Overview
Problem
Existing methods for monitoring electrical cables, such as LIRA, face limitations in sensitivity at cable terminations and areas of impedance changes, as well as the severity of degradation, particularly for cables longer than a few kilometers.
Innovation Solution
The method involves applying a broadband signal phase and amplitude modulated by cable impedance, calculating complex impedance, translating it into a time domain, performing power spectrum analysis to localize degradation, and identifying impedance changes through real and imaginary parts of the phase impedance spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If broadband signal with phase and amplitude modulation is applied to enhance detection sensitivity, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent applies phase and amplitude modulation to the broadband signal to encode cable impedance information. By changing the signal parameters (phase and amplitude) in response to impedance variations, the system achieves enhanced detection sensitivity without requiring complex hardware modifications
Solution Approach 2:
The patent uses an intermediary signal processing approach where the modulated broadband signal acts as a mediator between the cable impedance and the measurement system. The phase and amplitude modulation transfers impedance information into the signal domain, enabling precise detection through spectral analysis
2Measurement precision
If power spectrum analysis is performed on complex impedance to localize degradation, then measurement precision improves, but loss of time increases
Solution Approach 1:
The patent employs periodic action through the application of a swept-frequency broadband signal that excites resonant frequencies in the cable. By analyzing the periodic response and power spectrum at different frequencies, the system efficiently localizes degradation spots without requiring continuous monitoring
Solution Approach 2:
The patent performs preliminary action by pre-calculating the relationship between impedance changes and power spectrum characteristics. This allows the system to quickly identify degradation locations by comparing measured spectra against expected patterns, reducing analysis time
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 enhances the detection of local and global degradation in electrical cables, improving sensitivity and accuracy, especially for long cables, and allows for real-time monitoring and severity assessment of insulation degradation.
Implementation Method 1
applying a broadband signal wave having a frequency f to a first end of the electrical cable, wherein the broadband signal wave is phase and amplitude modulated by at least a cable impedance of the electrical cable
Implementation Method 2
applying a broadband signal wave having a frequency f to a first end of the electrical cable, wherein the broadband signal wave is phase and amplitude modulated by at least a cable impedance of the electrical cable
Implementation Method 3
acquiring at the first end of the cable the phase and amplitude modulated broadband signal wave transmitted and reflected by the electrical cable
Data Source
AI summary
A method and a system are described for monitoring a condition of an electrical cable. The method comprises applying a broadband signal wave to a first end of the electrical cable, wherein the broadband signal wave is phase and amplitude modulated and acquiring the phase and amplitude modulated broadband signal wave transmitted and reflected by the electrical cable. Signal analyses is performed which results in establishing a relationship between a real and an imaginary part of a phase impedance spectrum Fourier transform of the power spectrum in an interval around at least one of the locations along the cable, and identifying impedance changes in these locations. Analyzing a second order reflection of the broadband signal in said identified fault locations may establish a local degradation severity of an identified fault in the cable insulation in at least one of the locations along the cable.