Common-Mode Voltage Fault Detection in Impedance-Grounded DC Feeders
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Solution Overview
Problem
Traditional current-based fault detection methods are no longer viable for high voltage DC systems with impedance grounding topology, necessitating new methods for fault isolation coordination in aircraft electrical systems.
Innovation Solution
A system utilizing voltage sensors and a controller to monitor common mode voltage across resistors connected to DC feeders and ground, determining faults based on changes in common mode voltage exceeding a threshold, and isolating faults to specific feeders using common mode voltage signatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If impedance grounding topology is used in high voltage DC systems, then fault current levels are reduced and equipment damage is mitigated, but traditional current-based fault detection methods become non-viable
Solution Approach 1:
The patent replaces current-based detection (electrical measurement) with voltage-based detection using voltage sensors to measure common mode voltage across grounding resistors. This substitution enables fault detection in impedance-grounded systems where traditional current methods fail, while maintaining the protective benefits of limited fault current.
Solution Approach 2:
The patent introduces voltage sensors as intermediary devices that measure the voltage across grounding resistors during faults. These sensors act as mediators between the fault condition and the control system, enabling indirect detection of faults through common mode voltage measurements without requiring high fault current levels.
2Reliability
If traditional generator neutral grounding is used, then current sensing functionality is provided for fault detection, but aircraft weight increases
Solution Approach 1:
The patent makes voltage sensors serve multiple functions: they monitor common mode voltage for fault detection, enable fault location identification through voltage pattern analysis, and work with existing grounding resistors. This multi-functionality eliminates the need for separate dedicated current sensors, reducing aircraft weight while maintaining comprehensive fault detection capability.
Solution Approach 2:
The patent changes the detection parameter from current magnitude to common mode voltage level. By monitoring voltage across grounding resistors instead of measuring fault current directly, the system achieves equivalent fault detection functionality with lighter sensing equipment, as voltage sensors can be smaller and less robust than current sensors designed for high fault current measurement.
3Productivity
If impedance grounding is implemented, then system continues to operate during faults, but new fault detection methods are required
Solution Approach 1:
The patent implements feedback by continuously monitoring common mode voltage across grounding resistors and comparing it against threshold values. The control system receives voltage sensor signals, determines when faults occur based on voltage exceedance, and triggers appropriate responses. This feedback mechanism enables automatic fault detection and system continuation without requiring complex manual intervention or additional hardware complexity.
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 effective fault detection and isolation in high impedance ground systems, reducing aircraft weight and cost by eliminating dedicated current sensors, allowing continued operation and quick recovery from faults.
Implementation Method 1
A first voltage sensor is operatively connected to detect voltage across the first resistor. A second voltage sensor is operatively connected to detect voltage across the second resistor.
Implementation Method 2
The rectifier is configured to convert three phase AC from the three AC feeders of the generator into DC output to a load via a first DC feeder and a second DC feeder.
Data Source
AI summary
A system includes a generator. Three AC feeders are connected for feeding AC output from the generator. A rectifier is electrically connected to the three AC feeders and to a load via a first DC feeder and a second DC feeder. A first resistor connects between a first one of the DC feeders and ground. A first voltage sensor is operatively connected to detect voltage across the first resistor. A second resistor connects between the second DC feeder and ground. A second voltage sensor is operatively connected to detect voltage across the second resistor. A controller is configured to monitor for changes in common mode voltage based on the input from the first sensor and from the second sensor, and to determine presence of a fault if change in the common mode voltage exceeds a predetermined threshold.