Pressure Trip Unit Nonreturn Valve Selective Tripping
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Solution Overview
Problem
Current pressure trip units in electrical switches, particularly in current-limiting circuit breakers, face challenges in rapid and selective tripping during short circuits, as they often require precise control to prevent unnecessary disconnection of downstream consumers and ensure rapid switching off of the consumer-close switchgear.
Innovation Solution
A pressure trip unit with an actuating element and flow channels per electrical pole, featuring nonreturn valves that allow pressure from the disconnection zone to actuate the tripping mechanism, ensuring rapid and selective tripping by preventing flow between poles and utilizing a compact design with integrated nonreturn valves for efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressure trip unit uses a movable element with limited control stroke to respond to positive pressure from electric arc, then the tripping mechanism can be actuated during short circuit, but the device complexity increases due to the need for gas-tight units and restoring devices
Solution Approach 1:
The pressure trip unit is divided into separate flow channels for each pole, with each channel containing a nonreturn valve. This segmentation allows independent pressure buildup in each pole's disconnection zone, enabling selective tripping while simplifying the overall structure by eliminating the need for complex gas-tight units and restoring devices.
Solution Approach 2:
A nonreturn valve acts as an intermediary element between the disconnection zone and the actuating element. It mediates the pressure transmission by allowing pressure to build up unidirectionally during short circuit while preventing pressure equalization during normal operation, thus achieving selective tripping without complex restoring mechanisms.
2Speed
If the consumer-close switchgear opens with higher electric arc energy due to lower mass moment of inertia, then rapid single-pole opening is achieved, but the risk of unintended tripping in consumer-remote switchgear increases
Solution Approach 1:
The nonreturn valves are installed locally in each pole's flow channel at the consumer-close switchgear. This local modification ensures that pressure buildup occurs only in the specific pole experiencing short circuit, enabling rapid selective tripping of that single pole without affecting other poles or upstream switchgear.
Solution Approach 2:
The nonreturn valve changes the pressure parameter dynamics in the disconnection zone by allowing unidirectional pressure buildup during short circuit while preventing pressure equalization during normal operation. This parameter change enables the actuating element to respond only to abnormal pressure conditions, ensuring selective tripping reliability.
3Reliability
If nonreturn valves are integrated into flow channels for each pole, then selective tripping is enabled by preventing pressure flow between poles, but the manufacturing precision requirements increase
Solution Approach 1:
The nonreturn valve is merged with the flow channel structure, forming an integrated component. This merging eliminates the need for separate valve housings and complex assembly procedures, reducing manufacturing precision requirements while maintaining the selective pressure containment function for reliable tripping.
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
The solution enables rapid and selective tripping of electrical switches, preventing unnecessary disconnection of downstream consumers and ensuring efficient current limiting, thereby enhancing the reliability and safety of power distribution networks.
Implementation Method 1
an actuating element which responds to a positive pressure generated in the disconnection zone of the switching contacts by way of an electric arc drawn in the event of an electrodynamic recoil of the switching contacts
Implementation Method 2
the at least one flow channel comprises a nonreturn valve which permits a flow only from the disconnection zone in the direction of the actuating element
Data Source
AI summary
A pressure trip unit for an electrical switch, including an actuating element and at least one flow channel per electrical pole, is disclosed. In an embodiment, the at least one pole of the electrical switch includes at least two switching contacts for making or disconnecting a flow path. The switching contacts of the at least one pole of the electrical switch are disconnectable via the actuating element which can respond to a pressure generated in a disconnection zone of the, in each case, two switching contacts by an electric arc drawn in the event of an electrodynamic recoil of the switching contacts. Further, the disconnection zone is connectable to the actuating element via the flow channel, the at least one flow channel including a nonreturn valve to permit a flow only from the disconnection zone in the direction of the actuating element.