CO2 Switch for HVDC Grid Arc Interruption
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Solution Overview
Problem
High voltage direct current (HVDC) and medium voltage direct current (MVDC) transmission networks face challenges in efficiently interrupting direct current due to the lack of effective arc extinguishing methods, particularly at high voltages and varying temperatures, leading to increased switching costs and footprint.
Innovation Solution
A mechanical circuit breaker with an injection circuit for an oscillating current, utilizing a sealed enclosure with a gaseous fluid comprising at least 70% carbon dioxide, and a resonant circuit with specific capacitance and inductance values, optimized for wide temperature ranges and high switching performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SF6 gas is used in a DC circuit breaker with a resonant circuit, then arc extinguishing performance is achieved, but the operating temperature range is limited and the system becomes complex
Solution Approach 1:
The patent changes the chemical composition parameter of the gaseous medium from SF6 to CO2-based mixture. This parameter change enables the circuit breaker to operate reliably across a wide temperature range (-50°C to +50°C) while maintaining effective arc extinguishing performance, resolving the contradiction between reliability and adaptability.
2Power
If standard DC circuit breakers with sealed enclosures are connected in series to achieve higher voltage switching, then voltage switching capability is improved, but the footprint and cost increase
Solution Approach 1:
The patent changes the gaseous medium parameter to CO2 with optimized pressure (0.65-1.1 MPa) and composition ratios, which enables a single circuit breaker unit to achieve higher voltage switching capability without requiring series connections. This parameter optimization allows one compact unit to replace multiple series-connected units, reducing footprint.
3Productivity
If the capacitance value in the resonant circuit is increased to switch DC current, then current switching capability is improved, but the inductance value options become restricted
Solution Approach 1:
The patent changes the gaseous medium to CO2 and optimizes its pressure and composition parameters, which modifies the arc characteristics and allows for more flexible resonant circuit design. This enables a broader range of inductance values to be used effectively with the required capacitance values, expanding design options while maintaining current switching capability.
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 provides a compact, cost-effective switch with enhanced switching performance across a wide temperature range, improving the ability to interrupt direct current while reducing the need for large footprints and high costs.
Implementation Method 1
an arc-quenching gas, typically SF6, contained within the housing is compressed and sprayed onto the arc
Implementation Method 2
the gaseous fluid contained within the housing is compressed and sprayed onto the arc
Implementation Method 3
the resonant circuit, which includes an inductor and a capacitor, is connected in parallel to the circuit breaker to superimpose an oscillating current onto the direct current
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
The invention concerns a switch for a high or medium voltage DC grid, comprising a DC circuit breaker (5) the sealed chamber of which contains a gaseous fluid comprising at least 70% by volume carbon dioxide at a pressure of between 0.65 MPa and 1.1 MPa measured at a temperature of 20°C and a resonant circuit having a capacitance value (C) in μF and an inductance (L) in μΗ less than 2700*C-0.84.