Switching Device for Safe DC Overvoltage Protection Disconnection
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Solution Overview
Problem
The safe separation of overvoltage protection elements from power networks, particularly in direct current networks, is challenging due to the lack of natural zero crossings and the difficulty in interrupting continuous current flows, which can lead to heating and fire hazards, especially in photovoltaic systems where parasitic inductances complicate power interruption.
Innovation Solution
A method involving a second switch with a higher impedance supply path and a time-delayed opening mechanism, allowing current to divert to the second path when the first switch opens, separating surge voltage dissipation and arc extinguishing functions, and enabling safe disconnection of follow currents without requiring the second switch to handle surge currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single switch is used to interrupt the current path in DC networks, then the switch must be designed to safely interrupt surge currents and follow currents, but this leads to arcing and burning during separation, creating fire hazards
Solution Approach 1:
The current interruption function is segmented into two separate switches: a first switch (opening switch) that handles surge current interruption, and a second switch (follow current opening switch) that handles follow current interruption. This segmentation allows each switch to be optimized for its specific function, with the first switch designed for high current capacity and the second switch designed for safe arc extinction in DC conditions.
Solution Approach 2:
The first switch opens preliminarily before the second switch, creating a time-delayed sequence. This preliminary action allows the surge current to be interrupted first, followed by the follow current interruption. The time delay ensures that the most dangerous surge current is handled before the second switch operates, reducing the risk of arcing and burning.
2Productivity
If the second switch is opened immediately with the first switch, then the current path is quickly interrupted, but the follow current cannot be safely separated, leading to continued heating and fire hazards
Solution Approach 1:
The first switch opens preliminarily before the second switch, creating a time-delayed sequence. This preliminary action allows the surge current to be interrupted first, followed by the follow current interruption. The time delay ensures that the most dangerous surge current is handled before the second switch operates, reducing the risk of arcing and burning.
Solution Approach 2:
The switching device incorporates a time delay mechanism that dynamically controls the opening sequence of the two switches. The delay time can be adjusted to optimize the separation process, ensuring that the follow current is completely interrupted after the surge current has been handled. This dynamic control allows the system to adapt to different operating conditions while maintaining safe separation.
3Reliability
If a switch is designed to handle both surge current and follow current interruption, then it can provide complete protection, but the switch becomes overly complex and difficult to manufacture
Solution Approach 1:
The current interruption function is segmented into two separate switches: a first switch (opening switch) that handles surge current interruption, and a second switch (follow current opening switch) that handles follow current interruption. This segmentation allows each switch to be optimized for its specific function, with the first switch designed for high current capacity and the second switch designed for safe arc extinction in DC conditions.
Solution Approach 2:
The switching device provides multi-functionality by combining two switches with different capabilities in a single integrated system. The first switch is optimized for surge current handling while the second switch is optimized for follow current interruption. This universal design allows the system to handle both types of current interruption without requiring overly complex individual switch designs.
4Productivity
If the impedance of the second supply path is made significantly higher than the first, then the second path carries negligible current during normal operation, but this makes it difficult to safely interrupt follow current
Solution Approach 1:
The current interruption function is segmented into two separate switches: a first switch (opening switch) that handles surge current interruption, and a second switch (follow current opening switch) that handles follow current interruption. This segmentation allows each switch to be optimized for its specific function, with the first switch designed for high current capacity and the second switch designed for safe arc extinction in DC conditions.
Solution Approach 2:
The second supply path with higher impedance acts as an intermediary path that carries the follow current after the first switch opens. The time delay mechanism serves as a mediator that coordinates the opening sequence, allowing the second switch to safely interrupt the follow current after the surge current has been handled by the first switch.
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 approach allows for safe and complete disconnection of overvoltage protection elements from power networks, preventing heating and fire hazards by separating current paths and delaying the opening of the second switch to manage follow currents effectively, thus enhancing safety and reliability in direct current networks.
Implementation Method 1
an overvoltage protection element designed as a varistor
Implementation Method 2
Arcs typically occur during separation. A burning arc poses a significant danger.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a switching device for use as a second switch (26) in a method for disconnecting an electrical connection of an overvoltage protection element (12) connected between two connection points (16, 18) from one of these connection points (16), with a first supply path (20) which electrically connects a terminal of the overvoltage protection element (12) to one of the connection points (16), wherein a first opening switch (24) is arranged in the first supply path (20), which is triggered to open by a pressure change and/or a temperature change of the overvoltage protection element (12).It is provided that when the first switch (24) is opened, the system switches to a second supply path (22) connected in parallel to the first supply path (20), wherein a second opening switch (26) is arranged in the second supply path (22) for the safe disconnection of a follow current, and wherein the opening of the second switch (26) is delayed relative to the opening of the first switch (24), wherein the switching device is designed as a trailing contact (42) and has a device (56) for limiting the arc.