Earth Fault Detection Capacitance Estimation
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Solution Overview
Problem
The existing earth fault detection apparatus using a flying capacitor faces a decrease in calculation accuracy of insulation resistance due to variations in the capacitance of the detection capacitor, especially under changing environmental conditions such as temperature.
Innovation Solution
An earth fault detection apparatus that includes a control unit to estimate the capacitance of the detection capacitor and refer to a conversion map corresponding to the estimated capacitance, ensuring accurate insulation resistance calculation even when capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed conversion map is used for insulation resistance calculation, then the device complexity is reduced, but the measurement precision deteriorates when capacitance changes due to environmental conditions
Solution Approach 1:
The patent applies dynamics by making the conversion map adaptive rather than fixed. The control unit dynamically selects or adjusts the conversion map based on the detected capacitance value of the detection capacitor. This allows the system to maintain high measurement precision across varying environmental conditions while avoiding excessive complexity through automated adaptation.
Solution Approach 2:
The patent changes the parameter of the conversion map based on capacitance variations. When the capacitance of the detection capacitor changes due to temperature or other environmental factors, the system adjusts the conversion map parameters accordingly. This ensures that the insulation resistance calculation remains accurate despite changes in physical conditions.
2Productivity
If the charging time is shortened to enable quick earth fault detection, then the productivity is improved, but the measurement precision deteriorates due to insufficient capacitor charging and increased noise influence
Solution Approach 1:
The patent optimizes the charging time parameter to achieve a balance between detection speed and measurement accuracy. By carefully selecting the charging time duration, the system ensures that the detection capacitor charges sufficiently to provide accurate voltage measurements while maintaining quick response time for earth fault detection.
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
Prevents a decrease in calculation accuracy of insulation resistance by dynamically adjusting the conversion map based on the estimated capacitance, maintaining accurate detection of earth faults in varying conditions.
Implementation Method 1
a detection capacitor C1 functioning as a flying capacitor
Implementation Method 2
a charging resistor R1, R2 provided on the measurement path
Data Source
AI summary
An earth fault detection apparatus includes a switch group configured to switch between a first measurement path including a battery and a capacitor, a second measurement path including the battery, a negative-side insulation resistance, and the capacitor, a third measurement path including the battery, a positive-side insulation resistance, and the capacitor; and a control unit configured to calculate a reference value, based on each charging voltage of the capacitor in each measurement path, and configured to calculate an insulation resistance with reference to a predetermined conversion map, in which the conversion map includes a conversion map corresponding to a capacitance of the capacitor, and the control unit estimates the capacitance of the capacitor, and refers to the conversion map corresponding to the capacitance of the capacitor that has been estimated.