Corona Shield on Movable Contact Limits Arc Duration
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Solution Overview
Problem
High-voltage electrical equipment for transmission lines, such as earthing switches and circuit breakers, face challenges in managing the duration and occurrence of electric arcs during closing and opening phases, leading to increased wear and pollution, with existing solutions like increasing movement speed being costly and inefficient.
Innovation Solution
Incorporating a corona shield component on the movable contact that distributes electrical charge evenly and limits arc formation by projecting radially from the contact's upstream end, reducing the likelihood and duration of electrical breakdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the speed of movement of the movable contact is increased to reduce the duration of the electric arc, then the arc duration is reduced, but the drive means must be of large dimensions, thereby increasing the costs of the apparatus
Solution Approach 1:
A corona shield component is introduced as an intermediary element between the movable contact and the fixed contact. This corona shield distributes the electrical charge more evenly across the contact surface, delaying the moment of arc formation and reducing arc duration without requiring high-speed drive mechanisms. The corona shield acts as a mediator that modifies the electrical field distribution to achieve the desired effect.
Solution Approach 2:
The invention changes the surface characteristics of the movable contact by adding a corona shield with a smooth upstream face. This parameter change in surface topology modifies how electrical charge is distributed, transforming the charge concentration pattern from point-like (at the angular end) to distributed (across the smooth corona shield surface), thereby delaying arc formation.
2Ease of operation
If the movable contact has an angular shape to concentrate electrical charge and facilitate connection, then connection is facilitated, but the electric arc forms at a greater distance from the contacts, increasing arc duration and contact wear
Solution Approach 1:
The corona shield is applied locally at the upstream end of the movable contact rod, specifically at the location where charge concentration occurs. This local modification creates a smooth surface region that redistributes charge without altering the overall angular connection geometry. The local quality change addresses the arc duration problem while preserving the connection facilitation benefit.
Solution Approach 2:
The corona shield extends radially outward from the rod axis, adding a dimensional element that increases the effective surface area for charge distribution. This radial extension creates a larger charge distribution zone without changing the axial position or the fundamental angular connection shape, thus reducing arc duration while maintaining ease of connection.
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 corona shield effectively delays the onset and shortens the duration of electric arcs, reducing contact erosion and pollution, thereby extending the service life of the equipment while avoiding the need for large, costly drive mechanisms.
Implementation Method 1
the upstream face of the corona shield component, which is located axially opposite the fixed contact, is smooth... makes it possible to delay the instant of appearance of the arc
Implementation Method 2
the presence of the corona shield component at the level of the upstream end of the rod makes it possible to distribute the electrical charge of the moving contact more evenly over a large surface. Also, the presence of the corona barrier limits the frequency of electrical breakdowns
Implementation Method 3
the enclosure is filled with an electrically insulating gas such as for example sulfur hexafluoride SF6 or a pressurized gas mixture, making it possible to limit the formation of the electric arc
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention proposes a high-voltage appliance (10) comprising a fixed contact (12), a contact (22) in the appliance (10) that is movable between an upstream position in which the movable contact (22) is connected to the fixed contact (12) and a disconnected downstream position, in which the movable contact (22) comprises an axial rod (26) extending in the upstream direction, the upstream axial end (26a) of which is able to come into contact with the fixed contact (12), characterized in that the movable contact (22) carries a discharge-arrester component (34) extending radially around the end (26a) of the rod (26), and of which an upstream face (36) of the discharge-arrester component (34), which face is situated axially opposite the fixed contact (12), is smooth.