Fault Current Limiter With Liquid Dielectric Immersion
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Solution Overview
Problem
Current fault current limiters (FCLs) are not suitable for high voltage applications due to insulation challenges, particularly with dry type designs that rely on air as the insulation medium, which limits their effectiveness beyond 39 kV, and existing solutions for higher voltages are either impractical or economically unfeasible.
Innovation Solution
Inverting the conventional relative locations of AC and DC coils within a fault current limiter, allowing the entire structure to be immersed in a dielectric medium, with the AC coils wound around a magnetically saturable core and a DC biasing coil outside to bias the core into saturation during normal conditions and out of saturation during fault conditions, thereby providing increased current limiting impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dry type insulation with air as the insulation medium is used, then the device structure is simple and manufacturing is easier, but the voltage range is limited to up to approximately 39 kV
Solution Approach 1:
The patent changes the insulation medium from air (dry type) to liquid dielectric insulation medium, fundamentally altering the electrical insulation parameters to enable operation at higher voltages (33 kV to 750 kV) while maintaining structural integrity and performance
Solution Approach 2:
The patent employs liquid dielectric insulation medium (hydraulic principle) instead of air insulation, utilizing the superior electrical insulation properties and cooling capabilities of liquids to achieve high voltage operation and improved thermal management
2Reliability
If the AC phase coils are immersed in insulating gas, liquid, or vacuum, then the insulation strength is improved for high voltage applications, but the device complexity increases due to special dielectric interfaces and housing requirements
Solution Approach 1:
The patent merges the insulation function and cooling function into a single liquid dielectric medium, eliminating the need for separate insulation systems and cooling systems, thereby reducing overall device complexity while maintaining high voltage reliability
Solution Approach 2:
The liquid dielectric medium serves multiple functions simultaneously: electrical insulation, thermal cooling, and arc quenching, making the system more efficient and less complex than systems requiring separate components for each function
3Device complexity
If dry type insulation techniques are used, then the device structure is simpler and cooling is easier, but the insulation strength is insufficient for voltages greater than 39 kV
Solution Approach 1:
The patent changes the insulation medium from air to liquid dielectric, fundamentally altering the electrical and thermal parameters to simultaneously achieve superior insulation strength for high voltage applications and effective cooling, while maintaining reasonable device complexity
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 configuration enables the development of high voltage fault current limiters with lower insertion impedance, reduced footprint, and economic cost, suitable for high voltage designs without the need for special dielectric interfaces, and effectively limits fault currents while maintaining low harmonic distortion.
Implementation Method 1
a DC biasing coil for inducing a magnetic field in at least the portion of the core
Implementation Method 2
biases the core into magnetic saturation for low steady state un-faulted insertion impedance but during fault conditions takes the core out of magnetic saturation
Data Source
AI summary
A fault current limiter (FCL) includes a series of high permeability posts for collectively define a core for the FCL. A DC coil, for the purposes of saturating a portion of the high permeability posts, surrounds the complete structure outside of an enclosure in the form of a vessel. The vessel contains a dielectric insulation medium. AC coils, for transporting AC current, are wound on insulating formers and electrically interconnected to each other in a manner such that the senses of the magnetic field produced by each AC coil in the corresponding high permeability core are opposing. There are insulation barriers between phases to improve dielectric withstand properties of the dielectric medium.