Varistor Disconnecting Device Arc Prevention
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Solution Overview
Problem
Existing surge arresters face challenges with aging, leading to leakage currents and arcs, which cause uncontrolled destruction or unnecessary downtime due to high voltage spikes during sudden current interruption, requiring complex and costly designs with increased structural volume.
Innovation Solution
A varistor with a disconnecting device featuring a thermally softenable holding device and a pretensioned detachment means, which gradually increases resistance to limit current flow and prevent arcs by mechanically separating the connection contact, allowing controlled dissipation of magnetic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating protective elements are inserted to extinguish arcs by sudden current interruption, then arc extinction is achieved, but voltage spikes occur due to stored magnetic energy causing flashovers and system failure
Solution Approach 1:
A resistive element is introduced as an intermediary between the connection contact and the insulating protective element. This resistive element gradually limits the current flow during separation, preventing sudden current interruption and the associated voltage spikes. The resistive element acts as a mediator that controls the energy dissipation process, allowing the arc to be extinguished without causing harmful voltage transients that would lead to flashovers.
Solution Approach 2:
The invention converts the harmful magnetic energy stored in the circuit into a beneficial controlled dissipation process. By using the resistive element to gradually limit current flow during separation, the stored magnetic energy is converted into heat in a controlled manner rather than causing sudden voltage spikes. This transforms the harmful effect of stored energy into a beneficial controlled energy dissipation that prevents flashovers while still achieving arc extinction.
2Duration of action of moving object
If current is interrupted quickly to prevent arc effects, then arc duration is reduced, but voltage at the disconnection point increases sharply due to stored magnetic energy
Solution Approach 1:
The separation process is made gradual rather than instantaneous. The connection contact separates from the insulating protective element over a period of time, with the resistive element progressively limiting the current flow. This periodic/gradual action allows the magnetic energy to be dissipated in stages rather than all at once, reducing the voltage stress at any given moment while still achieving arc extinction within an acceptable time frame.
3Device complexity
If simple spring systems with solder or adhesive are used for thermal disconnection, then device complexity is reduced, but they cannot prevent uncontrolled destruction or require upstream fuse triggering causing downtime
Solution Approach 1:
A resistive element is introduced as an intermediary component between the connection contact and the insulating protective element. This additional element, while increasing complexity slightly, enables controlled current limitation during separation. The resistive element acts as a mediator that prevents uncontrolled destruction by limiting current flow and prevents the need for upstream fuse triggering, thereby avoiding downtime while maintaining reasonable device complexity.
4Ease of manufacture
If simple thermal disconnection devices are used, then production costs are reduced, but they lead to significant and costly downtimes due to upstream fuse triggering
Solution Approach 1:
The resistive element serves as a cost-effective intermediary that prevents the need for upstream fuse triggering. By gradually limiting current flow during separation, it prevents uncontrolled destruction that would require fuse replacement and system downtime. The added cost of this single component is far less than the cost of downtime and fuse replacement, making it an economically attractive solution.
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 effectively limits current flow to safe levels, prevents arcs, and allows for controlled system shutdown without voltage spikes, reducing design complexity and size while ensuring safety and continued operation.
Implementation Method 1
leakage currents occur, for example, which lead to (continuous) heating of the surge arrester
Implementation Method 2
the solder or the adhesive softens, so that the energy stored in the spring system breaks the direct electrical contact with the surge arrester
Implementation Method 3
the disconnecting device/the detachment means 6 is now designed to be resistive. As a result, a current that is still flowing through the varistor 1 is limited to harmless values and at the same time the formation of arcs is prevented
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a varistor (1) comprising a disconnecting device (A) which can interrupt the flow of current through the varistor (1) in case of a fault. The disconnecting device (A) includes a terminal contact (5) that establishes an electrical contact with a first terminal (2) of the varistor (1), the electrical contact being secured by a thermally softenable holding device (4). The disconnecting device (A) further includes a separating means (6) which is biased by an energy accumulator (7) and which, in case of a fault, mechanically separates the terminal contact (5) from the first terminal (2) of the varistor (1) when the thermally softenable holding device (4) softens. The separating means (6) is resistive in order to limit the current flowing through the varistor (1) and prevent electric arcs from forming.