Solid-State DC Protection Circuit for Selective Fault Isolation
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Solution Overview
Problem
Existing DC electrical grids face challenges in providing selective protection, particularly in meshed topologies and bidirectional power flow systems, where faults need to be isolated without disrupting the entire grid, as conventional protection devices often fail to discriminate between upstream and downstream faults effectively.
Innovation Solution
The development of a solid-state DC protection device that includes a capacitor to supply short-circuit current for fault detection and a control circuit to selectively switch solid-state switches, enabling rapid and selective disconnection of faults while maintaining grid operation, with configurations for both unidirectional and bidirectional power flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protection devices are used in DC electrical grids, then fault detection capability is provided, but selectivity in isolating faults is insufficient causing unnecessary disconnection of healthy grid portions
Solution Approach 1:
The protection device segments the DC electrical grid into protected zones by implementing selective tripping capability. The breaker isolates faults to specific sections rather than disconnecting the entire grid, allowing healthy portions to remain operational. This is achieved through coordinated protection schemes that identify and isolate faults to minimal affected areas.
Solution Approach 2:
The patent introduces communication systems and control circuits as intermediaries between detection elements and switching devices. These intermediaries enable selective tripping by processing fault information and coordinating responses across multiple breakers, allowing precise isolation of faults while maintaining grid connectivity in non-affected areas.
2Speed
If protection devices disconnect faults rapidly, then fault isolation speed is improved, but discrimination between upstream and downstream faults deteriorates
Solution Approach 1:
The protection device employs feedback mechanisms where detection circuits continuously monitor current conditions and provide real-time information to control circuits. This feedback enables the system to distinguish between upstream and downstream faults by analyzing current flow patterns, allowing rapid response while maintaining accurate fault location discrimination.
Solution Approach 2:
The patent implements preliminary coordination between upstream and downstream protection devices through communication systems. Before fault isolation occurs, the system exchanges information to determine fault location and coordinates tripping actions, enabling both rapid response and precise discrimination. This preliminary coordination prevents misoperation while maintaining fast fault clearance.
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 solution allows for rapid detection and isolation of faults, preventing destructive current levels and ensuring selectivity, thereby maintaining normal operation of the grid by localizing faults and preventing upstream propagation.
Implementation Method 1
a capacitor coupled to each of the at least one solid state switching device and configured to store sufficient charge such that, in the event of a short-circuit condition
Data Source
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AI summary
The invention provides a DC solid state protection device (20) that comprises a capacitor (Cs) configured such that in the event of a short-circuit condition, the capacitor provides all the short-circuit current required for the solid state protection device to detect a current indicative of a short-circuit condition and to cause a solid state switch (NM1) to be opened, thereby tripping the solid state protection device (20).