Semiconductor DC Switch Reclosing for Selective Fault Isolation
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Solution Overview
Problem
DC voltage switches with semiconductor-based switching devices face challenges in achieving selectivity during faults, leading to unintended disconnection of non-faulty branches due to saturation current limitations, necessitating overdimensioning or expensive electromechanical solutions.
Innovation Solution
A DC voltage switch comprising a semiconductor-based, electronically controllable switching device with upstream and downstream voltage sensors, a current sensor, and a control device that periodically determines current direction and level, interrupting current flow when thresholds are exceeded, and reconnections based on voltage differences to ensure selective disconnection and reconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If semiconductor-based switching devices are used in DC voltage switches, then the switching speed and electronic controllability are improved, but the saturation current limitation causes unintended disconnection of non-faulty branches during faults
Solution Approach 1:
The patent introduces an intermediary mechanism (current direction detection and voltage comparison system) between the semiconductor switching device and the fault condition. This intermediary detects reverse current direction and voltage differences, controlling the switching device to maintain conductivity during reverse current flow, thereby preventing unintended disconnection of non-faulty branches while preserving the semiconductor device's fast switching capability
2Reliability
If the saturation current of semiconductor switching elements is increased to prevent unintended disconnection, then the selectivity during faults is improved, but the switching device becomes overdimensioned and more expensive
Solution Approach 1:
The patent applies dynamics by making the switching device's conductivity state dynamic rather than static. The device adjusts its operation mode based on real-time detection of current direction and voltage differences: maintaining conductivity during reverse current flow (fault condition) and enabling normal switching during forward current flow (normal operation). This dynamic adaptation allows the use of properly dimensioned semiconductor devices without overdimensioning
Solution Approach 2:
The patent changes the operational parameters of the switching device based on detected conditions. By monitoring current direction and voltage differences, the system alters the switching device's state (conducting vs. blocking) according to the operational phase, allowing standard semiconductor devices to operate within their rated parameters while achieving fault selectivity
3Reliability
If electromechanical switching devices are used instead of semiconductor devices to achieve selectivity, then the selectivity during faults is improved, but the switching speed and electronic controllability deteriorate
Solution Approach 1:
The patent replaces the mechanical switching mechanism with an electronically controlled semiconductor-based switching device. The semiconductor device is controlled through electronic detection of current direction and voltage differences, eliminating mechanical moving parts while achieving fault selectivity through electronic control logic, thus maintaining fast switching speed and electronic controllability
Data Source
AI summary
A DC voltage switch includes a semiconductor-based electronically controllable switching device, a sensor provided upstream of the switching device for determining the DC voltage bus-side voltage level, a sensor provided downstream of the switching device for determining the DC voltage branch-side voltage level, a current sensor for determining current level and direction, a control device designed such that the direction and level of the current are determined, the flow of current is interrupted by the switching device when a first threshold value of the current level is exceeded, and when the first threshold value of the current level is exceeded in the reverse direction: the DC voltage bus-side voltage level is compared with the DC voltage branch-side voltage level, and the switching device is switched on upon a voltage difference being less than a voltage difference value.