Vehicle Ground Fault Detection Using Isolation Resistance Comparison
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Solution Overview
Problem
Existing isolation monitoring systems in electrified vehicles cannot accurately determine the source of a faulty ground connection, leading to false indications of high isolation resistance and potential hazards due to leakage currents, especially in components like fuel cell stacks and immersion cooled battery systems.
Innovation Solution
A computer system that obtains isolation resistance data before and after connecting a vehicle subsystem to a traction voltage pole, compares the data to determine a faulty ground connection by analyzing the change in resistance, and optionally uses short circuits and temperature compensation to enhance detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation monitoring systems measure resistance from high voltage poles to chassis, then leakage current detection is enabled, but the source of faulty ground connection cannot be determined
Solution Approach 1:
The patent segments the grounding system into multiple measurement points by introducing separate grounding resistance measurement circuits for different components (fuel cell stack, battery system, motor controller) in addition to the main chassis isolation monitoring. This allows independent measurement of each component's grounding resistance, enabling fault source identification while maintaining overall leakage current detection capability.
2Measurement precision
If a component loses its ground connection, then measured isolation resistance improves, but actual hazard increases due to stopped leakage current flow
Solution Approach 1:
The patent implements preliminary detection of grounding connection status by continuously monitoring component-to-chassis resistance separately from isolation resistance. When a grounding fault is detected (abnormal resistance change), the system triggers an alarm or shutdown before dangerous voltage potentials can develop, preventing the harmful effect rather than just detecting it after isolation resistance measurement shows false improvement.
3Reliability
If multiple isolation resistance monitors are used to monitor individual devices, then fault detection capability improves, but device complexity and cost increase
Solution Approach 1:
The patent makes existing isolation resistance monitors multi-functional by configuring them to perform both traditional isolation resistance measurement and component grounding resistance measurement through appropriate circuit configuration and measurement sequencing. This eliminates the need for separate dedicated grounding monitors for each component, reducing overall system complexity while maintaining comprehensive fault 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
This method reduces the risk of false indications of high isolation resistance, ensuring robust handling of leakage currents by accurately identifying faulty ground connections, thereby enhancing safety in vehicles with fuel cell and immersion cooled battery systems.
Implementation Method 1
isolation resistance data between a traction voltage pole and a chassis of a vehicle
Data Source
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AI summary
A computer system is provided. The computer system comprises processing circuitry configured to: obtain first isolation resistance data (222) between a traction voltage pole (16A, 16B) and a chassis (P) of a vehicle (1) when at least one vehicle subsystem (10) is electrically disconnected from the traction voltage pole (16A, 16B); electrically connect the at least one vehicle subsystem (10) to the traction voltage pole (16A, 16B); obtain second isolation resistance data (224) between the traction voltage pole (16A, 16B) and the chassis (P) when the at least one vehicle subsystem (10) is electrically connected to the traction voltage pole (16A, 16B); compare the second isolation resistance data (224) with the first isolation resistance data (222); and determine a faulty ground connection of the at least one vehicle subsystem (10) based on the comparison of the second isolation resistance data (224) with the first isolation resistance data (222).