Medium-Voltage Electrical Contact Geometry to Prevent Arc Welding
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Solution Overview
Problem
Existing medium and high voltage switches, such as NAL, Versa Rupter, and NALF switches, face the issue of electric arc welding at the galvanic contact point, leading to potential operator hazards and system damage due to the unpredictable nature of arc formation and extinguishing.
Innovation Solution
The design of an electrical contact system for medium-voltage switch disconnectors, featuring a knife and fixed contact with specific positions and geometries to control and prolong the electric arc at the arc ignition point, reducing the likelihood of arc formation at the galvanic contact point, utilizing empirical testing to optimize the distance and shape of the contact elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a double arc extinguishing system with air blast and gas blast is used, then the arc is effectively cooled and extinguished, but the electric arc may form at the galvanic contact point causing welding between contact elements
Solution Approach 1:
The fixed contact is divided into two separate parts: a first part comprising the arc ignition point and a second part comprising the galvanic contact point. This segmentation ensures that the arc forms at the dedicated ignition point rather than at the galvanic contact point, preventing welding while maintaining effective arc extinguishing through the gas blast system
Solution Approach 2:
Different parts of the fixed contact are given different geometric properties: the arc ignition point is sharpened to facilitate controlled arc formation, while the galvanic contact point is rounded to prevent arc initiation. This local differentiation of contact properties ensures arcs form only at the intended location
2Strength
If the knife and fixed contact are made of durable materials like CuETP, then the contacts can withstand welding and splitting, but the risk of welding at the galvanic contact point remains
Solution Approach 1:
The harmful function of the galvanic contact point (arc formation) is extracted and separated from the actual galvanic contact function. By placing the arc ignition point on a separate first part of the fixed contact, the design removes the risk of welding at the galvanic contact point while maintaining the durability of the contact materials
3Speed
If a quick closing process is used, then the switch operation speed is improved, but the welding at galvanic contact point occurs more frequently
Solution Approach 1:
The arc ignition point is positioned and shaped in advance to intercept the arc formation process before it can reach the galvanic contact point. The sharpened geometry of the ignition point creates a preferred path for arc formation, ensuring that even during quick closing operations, the arc forms at the controlled location rather than causing welding
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 significantly reduces the chances of the main knife and galvanic contact welding, enhancing operator safety and system reliability by ensuring the electric arc remains primarily at the arc ignition point for a longer duration, thereby preventing unwanted welding.
Implementation Method 1
a first position, where the knife is in such distance from the fixed contact, that an air act as an electrical insulator
Implementation Method 2
a second position, wherein the closest distance between the knife and the fixed contact is between the first portion of the knife and the arc ignition point and wherein the closest distance allows to form an electrical arc between the first portion of the knife and the arc ignition point
Data Source
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AI summary
According to first embodiments of the invention the electrical contact, suitable for medium-voltage switch disconnector is provided. Electrical contact comprises of a knife, comprising a first portion and a second portion and a fixed contact, wherein the fixed contact comprises a galvanic contact point, and an arc ignition point. The electrical contact is characterized in that the knife is configured to take one of following positions: - a first position, where the knife is in such distance from the fixed contact, that an air act as an electrical insulator, - a second position, wherein the closest distance between the knife and the fixed contact is between the first portion of the knife and the arc ignition point and wherein the closest distance allows to form an electrical arc between the first portion of the knife and the arc ignition point; - a third position, wherein the closest distance between the knife and the fixed contact is between the second portion of the knife and the galvanic contact point; - a fourth position, where the knife and the fixed contact are electrically coupled, namely the second portion of the knife and the galvanic contact point are electrically coupled.