DC Grid Switch Power Supply Switching to Prevent In-Rush Currents
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Solution Overview
Problem
Existing DC electric grid switching apparatuses face issues with high manufacturing costs and limited current breaking performance due to in-rush currents during opening maneuvers, particularly in self-powered control stages with large input capacitances.
Innovation Solution
A switching apparatus with a secondary switching arrangement controlled by a control unit to alternate the connection of the power supply stage to different terminals based on the operating state, preventing in-rush currents and allowing a smaller, cheaper power supply stage design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self-powered control stage with large input capacitance is used to feed the control unit, then the control stage can be powered during opening maneuvers, but in-rush currents occur that increase manufacturing costs and limit current breaking performance
Solution Approach 1:
The patent applies dynamics by making the connection between the power supply stage and electric line terminals dynamic rather than static. The secondary switching devices dynamically connect the power supply stage to different terminals (first or second terminal) based on the operating state of the primary switching devices, allowing the system to adapt to different conditions and prevent in-rush currents while maintaining reliable control power supply
Solution Approach 2:
The secondary switching devices act as intermediaries between the power supply stage and the electric line terminals. These intermediary components control and regulate the connection, preventing direct in-rush current flow while ensuring the control stage receives adequate power during opening maneuvers
2Strength
If a bulky input capacitor is arranged in the power supply stage to withstand in-rush currents, then the power supply stage can avoid damages, but the current breaking performances of the switching devices are remarkably limited
Solution Approach 1:
The patent applies preliminary anti-action by using the secondary switching devices to prevent in-rush currents from occurring in the first place. The secondary switching devices are configured to disconnect or limit the connection to the first terminal during opening maneuvers, proactively preventing the harmful in-rush current phenomenon before it can damage the input capacitor or limit current breaking performance
3Ease of operation
If the power supply stage is electrically connected to the power source side to feed the control stage during opening maneuvers, then the control stage can operate, but in-rush currents subject the power supply stage to high energy phenomena
Solution Approach 1:
The patent makes the power supply connection dynamic by using secondary switching devices to selectively connect the power supply stage to different terminals based on operating conditions. During opening maneuvers, the secondary switching devices dynamically switch the connection to avoid in-rush currents while maintaining control stage operation
Solution Approach 2:
The secondary switching devices serve as intermediary components that mediate between the power supply stage and the electric line terminals. They control the connection to prevent harmful in-rush currents while ensuring the control stage receives necessary power during opening maneuvers
Data Source
AI summary
The present disclosure relates to a switching apparatus for DC electric grids. The switching apparatus comprises first and second electric terminals for electrical connection with corresponding conductors of an electric line. The switching apparatus further comprises a primary switching arrangement including primary switching devices configured to conduct or block a current along a conductive path between the first and second electric terminals. The switching apparatus additionally comprises a control stage configured to control one or more components of the switching apparatus and a power supply stage electrically connected to the control stage to feed the control stage with electric power. The switching apparatus also comprises a secondary switching arrangement including secondary switching devices controllable by the control stage. The secondary switching devices are configured to electrically connect the power supply stage with said first electric terminals or with said second electric terminals.