Waveform Separator for HVDC Leakage Current Spike Detection
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Solution Overview
Problem
High voltage direct current (HVDC) systems require a method to accurately measure leakage current, which consists of fast DC transients or spikes, as conventional DC meters fail to detect these momentary spikes due to their low sampling rates and inability to react to high-magnitude, short-duration discharges, posing a risk of flashover.
Innovation Solution
A waveform separator system that separates DC leakage current into DC and AC components using analog filters and amplifiers, with a microcontroller ADC sampling the DC component at a low rate and voltage comparators generating digital pulses for AC components, allowing for the detection of both polarities without swapping inputs, and a microprocessor to count these pulses for accurate measurement.
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, but the measurement precision is insufficient because they cannot detect short-duration spikes
Solution Approach 1:
The patent segments the leakage current measurement task into two distinct components: DC component measurement using a low-pass filter and ADC, and AC transient component measurement using a high-pass filter and comparator. This segmentation allows each subsystem to be optimized for its specific function, achieving high measurement precision for both steady-state and transient leakage currents while keeping individual subsystems relatively simple
Solution Approach 2:
The patent introduces waveform separator circuitry as an intermediary component that divides the composite leakage current signal into DC and AC components before measurement. This intermediary separates the measurement functions, enabling accurate detection of both types of components without requiring a single complex high-speed sampling system
2Measurement precision
If high sampling rates are used to capture short-duration spikes, then the measurement precision improves, but the use of energy and device complexity increase
Solution Approach 1:
The patent segments the signal processing into frequency-based components, using a high-pass filter to isolate transient spikes from the DC component. This allows the system to process only the relevant transient portion with high precision while keeping the overall sampling rate low, thereby reducing power consumption compared to continuously high-rate sampling
Solution Approach 2:
The patent changes the measurement parameter from time-domain sampling rate to frequency-domain separation. Instead of increasing sampling rate to capture spikes, the system uses frequency-based waveform separation to isolate and measure transient components, achieving spike detection capability without the energy cost of high-rate continuous sampling
3Measurement precision
If AC multimeters are used to measure leakage current, then the measurement precision for transient spikes improves, but they cannot be safely used in HVDC systems due to fundamental differences between AC and DC
Solution Approach 1:
The patent creates a universal measurement system that can handle both DC steady-state currents and AC transient spikes within a single HVDC-compatible apparatus. The waveform separator and dual-path measurement architecture provide multi-functionality, making the system adaptable to different leakage current characteristics while maintaining safety for HVDC applications
Solution Approach 2:
The waveform separator acts as an intermediary that adapts the measurement approach for HVDC conditions. It separates DC and AC components, allowing the system to measure transient spikes similar to AC systems while being specifically designed and safe for HVDC operation, thus bridging the gap between AC measurement capabilities and DC system requirements
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 the accurate measurement and timely indication of leakage current spikes, providing early warning of potential flashovers and ensuring safety by effectively capturing short-duration spikes in HVDC systems without the need for extremely high sampling rates.
Implementation Method 1
a waveform separator to separate the composite DC current into DC and AC components
Implementation Method 2
voltage comparators to convert the AC component into digital pulses
Implementation Method 3
an ADC to convert the DC component into digital values
Data Source
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AI summary
A waveform separator system for determining DC leakage current flowing through an insulating structure in a high voltage direct current power system, wherein the DC leakage current is a composite DC current comprising one or more high magnitude momentary spikes, and having a DC component and an AC component includes: (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) components wherein the AC component has a first rate of change, and wherein the DC component has a second rate of change, and wherein the first rate of change is greater than the second rate of change; (2) at least one comparator configured to receive the AC component and produce at least one corresponding digital signal; and (3) a processor configured to: (a) receive the at least one corresponding digital signal and the DC component, (b) analyze the at least one corresponding digital signal and the DC component, and; (c) determine a resultant leakage current flowing through the insulating structure.