Waveform Separator for HVDC Leakage Current Spike Detection
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Solution Overview
Problem
Conventional DC meters fail to accurately detect high-magnitude, short-duration spikes in leakage current in high voltage direct current (HVDC) systems, posing a risk of flashover due to their inability to react to momentary spikes, which are critical for early warning and safety.
Innovation Solution
A waveform separator system that separates composite DC current into DC and AC components using analog filters and amplifiers, with a microcontroller sampling the DC component at a low rate and voltage comparators producing digital signals for the AC component, allowing for accurate measurement and display of leakage current spikes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional DC meters are used to measure leakage current, then the device complexity is low and ease of operation is good, but the measurement precision is insufficient to detect high-magnitude short-duration spikes
Solution Approach 1:
The patent divides the leakage current measurement task into two separate measurement paths: one for DC component (using conventional DC meter) and one for AC component (using AC-coupled amplifier and rectifier). This segmentation allows each path to be optimized for its specific measurement task, achieving high precision for spike detection while keeping individual components relatively simple
Solution Approach 2:
The patent introduces an AC-coupled amplifier as an intermediary device between the leakage current source and the measurement system. This intermediary amplifies the AC component (spikes) before measurement, enabling detection of high-magnitude short-duration spikes without requiring the entire measurement system to have extremely high bandwidth and complexity
2Measurement precision
If high sampling rates are used to capture momentary spikes, then the measurement precision improves, but the productivity decreases due to increased data processing requirements
Solution Approach 1:
The patent extracts the AC component (spikes) from the composite leakage current signal using AC coupling, separates it from the DC component, and processes it independently through amplification and rectification. This extraction allows the system to focus processing resources only on the spike portions of the signal rather than sampling and processing the entire waveform at extremely high rates
Solution Approach 2:
The patent employs rectification to convert the AC spike component into a unidirectional signal that can be measured by DC meters. This periodic action (rectification) transforms the challenging AC spike waveform into a form that can be captured and processed more efficiently, reducing the overall sampling rate requirements while maintaining spike detection capability
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
Enables accurate detection and display of leakage current spikes in HVDC systems, providing early warning of potential flashovers and ensuring worker safety by effectively capturing momentary spikes without the need for extremely high sampling rates.
Implementation Method 1
a waveform separator configured to receive the composite DC current flowing through the insulating structure and to separate the composite DC current into corresponding direct current (DC) and alternating current (AC) component
Implementation Method 2
at least one comparator configured to receive the AC component and produce at least one corresponding digital signal
Data Source
AI summary
Determining direct current (DC) leakage current flowing through an insulating structure in a high voltage DC power system wherein the DC leakage current is a composite DC current having one or more high magnitude momentary spikes, and having a DC component and an alternating current (AC) component, wherein the AC component has a first rate of change, and wherein the DC component has a second rate of change less than the first, having (a) providing a waveform separator which is configured to receive the composite DC current flowing through the insulating structure and to separate the composite DC current into the corresponding DC component and AC component, and (i) receive at least one corresponding digital signal and the DC component, ii) analyze the at least one corresponding digital signal and the DC component, (iii) determine a resultant leakage current flowing through the insulating structure, (b) electrically connecting the waveform separator to the insulating structure, (c) separating, in the waveform separator, the composite DC current into the corresponding DC component and AC component, (d) receiving the AC component in at least one comparator and producing at least one corresponding digital signal, (e) counting one or more positive AC components in the at least one positive voltage comparator, (f) counting one or more negative AC components in the at least one negative voltage comparator, (g) producing at least one positive digital signal corresponding to the counted one or more positive components and a negative digital signal corresponding to the counted one or more negative components, (h) processing the positive digital signal and the negative digital signal, and the DC component, and determining a resultant leakage current flowing through the insulating structure.