Coanda-Effect Earthing Switch for Arc Quenching in g3 GIS
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Solution Overview
Problem
The new g3 gas used in gas-insulated substations is more easily decomposed and ionized, leading to persistent arcs during the opening of fast earthing switches, which is not effectively addressed by existing technologies.
Innovation Solution
A fast earthing switch design that includes a movable contact rod with a gas chamber and an outlet, where a flow of gas is directed along the contact rod to reduce its temperature, restoring dielectric properties and extinguishing the arc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If g3 gas is used to replace SF6, then environmental impact is reduced, but arc extinction capability deteriorates
Solution Approach 1:
The gas chamber is divided into multiple regions with different gas flow paths. The outlet is positioned to create a targeted gas flow along the contact rod, segmenting the arc quenching process into zones of cooling and dielectric restoration, thereby improving arc extinction capability while maintaining environmental benefits of g3 gas
Solution Approach 2:
Gas flow is directed along the contact rod before the arc fully develops, pre-cooling the rod surface and preparing the gas medium for faster dielectric recovery. This preliminary cooling action prevents the arc from becoming persistent, solving the arc extinction problem while preserving the environmental advantages of g3 gas
2Productivity
If gas flow rate is increased to improve arc quenching, then arc extinction speed increases, but gas consumption increases
Solution Approach 1:
Gas flow is concentrated locally along the contact rod surface where the arc occurs, rather than increasing overall gas flow rate. The outlet geometry creates a focused jet that cools the rod and quenches the arc efficiently in the critical zone, achieving fast arc extinction without proportionally increasing total gas consumption
Solution Approach 2:
The outlet is designed to utilize gas pressure and flow dynamics to create a coherent jet along the contact rod. By optimizing the outlet geometry and position, the gas flow maintains high velocity and coherence over the rod surface, improving arc quenching efficiency without requiring excessive gas quantities
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 efficiently quenches the arc, ensuring rapid and reliable switching operations in GIS filled with SF6 or alternative gases like g3, reducing environmental impact and maintaining operational efficiency.
Implementation Method 1
The flow of gas at the end portion of the contact rod reduces the temperature of the previously arced gas. The 'cooling' of this zone restores the dielectric properties of the gas and the electric arc is interrupted.
Implementation Method 2
Fast earthing switch implementing the coanda effect
Data Source
Figure 1A~1B
Figure 2~3
Figure 4~5
AI summary
The invention concerns a fast earthing switch (10) for a GIS comprising: - a movable contact rod (12), having an end (14); - a cylinder (20), fixed to said contact and forming a gas chamber (28) around at least part of said contact rod, said gas chamber comprising an outlet (22) around said contact rod so that gas can flow along said contact rod (12) and its end (14) when it moves from a closed to an open position; - means (6, 8) for actuating said contact rod between a closed and an open position.