Insulation Resistance Detection Using Digital Signal Processing
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Solution Overview
Problem
Conventional abnormality detection devices for high-voltage circuits require expensive input capacitors for filter circuits, leading to increased component costs and circuit area due to the need for large capacitance and high withstand voltage, which complicates the detection of insulation resistance abnormalities.
Innovation Solution
The device employs a coupling capacitor with a signal output unit and a signal extraction unit that includes low-pass filters and a differential amplifier to remove low-frequency noises without requiring an expensive input capacitor, using a detection resistor to output an alternating-current inspection signal and extracting a differential signal to detect insulation resistance abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter circuit with input capacitor is used to remove low-frequency noises, then noise removal effectiveness is improved, but component cost and circuit area increase due to expensive high-withstand-voltage capacitors
Solution Approach 1:
The patent replaces the traditional passive RC filter circuit (mechanical/electrical system requiring physical capacitors) with an active digital signal processing system. The low-pass filter function is implemented through digital algorithms in the signal processing unit, eliminating the need for physical input capacitors with high withstand voltage ratings. This substitution maintains noise removal effectiveness while reducing component cost and circuit area.
Solution Approach 2:
The patent introduces an intermediary high-voltage-to-low-voltage conversion stage between the high-voltage circuit and the signal processing unit. This intermediary converts the high-voltage inspection signal to low voltage before digital processing, allowing the use of standard low-voltage electronic components instead of expensive high-voltage components. The conversion is achieved through a voltage divider circuit followed by an operational amplifier stage.
2Object-affected harmful factors
If large capacitance input capacitors are used for high-voltage filter circuits, then noise filtering performance is improved, but component cost increases
Solution Approach 1:
The patent replaces physical capacitor-based filtering with digital signal processing. The signal processing unit implements digital low-pass filtering algorithms that achieve the same noise rejection performance without requiring large capacitance physical capacitors. This eliminates the cost burden of high-voltage, high-capacitance components while maintaining filtering effectiveness.
Solution Approach 2:
The patent transitions the filtering function from the electrical domain (physical capacitors and resistors) to the digital/domain of signal processing. By converting the analog inspection signal to digital form through ADC (analog-to-digital conversion), the filtering operation moves to the digital domain where algorithms provide the same functionality without physical component constraints.
3Measurement precision
If high-voltage inspection signals are directly processed, then signal integrity is maintained, but signal processing becomes difficult due to high voltage levels
Solution Approach 1:
The patent introduces a voltage conversion intermediary stage that safely bridges the high-voltage and low-voltage domains. The voltage divider circuit attenuates the high-voltage inspection signal to a safe level, and the operational amplifier restores the signal amplitude to usable levels. This intermediary enables standard low-voltage signal processing techniques to be applied while maintaining signal integrity through careful circuit design.
Solution Approach 2:
The patent segments the signal processing function into distinct stages: high-voltage signal acquisition, voltage attenuation, voltage restoration, ADC conversion, and digital processing. This segmentation allows each stage to be optimized independently, with the voltage conversion stage specifically designed to handle the high-to-low voltage transition safely and accurately.
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 configuration reduces the influence of low-frequency noises and eliminates the need for costly filter circuits, allowing for effective detection of insulation resistance abnormalities while minimizing component costs and circuit area.
Implementation Method 1
a coupling capacitor having a first end and a second end that is to be coupled with the high-voltage circuit
Implementation Method 2
a signal output unit coupled with the first end of the coupling capacitor via a detection resistor, and outputs an alternating-current inspection signal
Implementation Method 3
The signal extraction unit includes a signal removing filter and a subtraction circuit. The signal removing filter removes a signal equal in frequency to the inspection signal, and passes, through the filter, noises lower in frequency than the inspection signal
Implementation Method 4
The subtraction circuit outputs a differential signal as the extraction signal. The differential signal is a difference between a signal having been passed through the signal removing filter and a signal not having been passed through the signal removing filter
Data Source
AI summary
An abnormality detection device includes: a coupling-capacitor having a first-end and a second-end coupled with a high-voltage circuit; a signal output unit; a signal extraction unit; and a signal input unit. The signal output unit is coupled with the first-end of the coupling-capacitor via a detection-resistor, and outputs an alternating-current inspection-signal. The signal extraction unit extracts the inspection-signal, as an extraction-signal, output between the detection-resistor and the coupling-capacitor. The signal input unit detects abnormality of insulation resistance of the high-voltage circuit based on a level of the inputted extraction-signal. The signal extraction unit includes a signal removing filter and a subtraction circuit. The filter removes a signal equal in frequency to the inspection-signal and passes low-frequency noises lower in frequency than the inspection-signal. The subtraction circuit outputs a differential signal, as the extraction-signal, between a signal having passed through the filter and a signal not having passed through the filter.