DC Grid Protection With Position-Dependent Inductance Selectivity
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Solution Overview
Problem
DC electric grids face challenges in achieving selective disconnection of faulted portions without affecting normally operating parts due to uniform fault current distribution and high peak values, leading to non-selective intervention of protection devices.
Innovation Solution
The DC electric grid incorporates protection devices with magnetic devices having position-dependent inductance values and control devices to manage switching assemblies, allowing selective disconnection based on fault location and current thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection devices are arranged at various positions in the DC electric grid to provide circuit protection, then the grid safety is improved, but the selectivity of disconnection deteriorates because all protection devices intervene simultaneously due to uniform fault current distribution
Solution Approach 1:
The patent applies local quality by assigning different inductance values to magnetic devices at different positions in the DC electric grid. Each protection device is configured with a specific inductance value tailored to its location, creating local differentiation that enables selective operation. This resolves the contradiction by maintaining grid safety through comprehensive protection while achieving selectivity through position-dependent inductance characteristics.
Solution Approach 2:
The patent implements parameter changes by varying the inductance values of magnetic devices based on their position in the grid. The inductance parameter is specifically adjusted so that protection devices at different locations have different electromagnetic responses to fault currents. This allows the control system to distinguish between faults at different positions and trigger only the appropriate protection devices, thereby achieving both safety and selectivity.
2Speed
If protection devices use uniform fault threshold values to respond to fault currents, then the response speed is improved, but the precision of fault location identification deteriorates
Solution Approach 1:
The patent applies local quality by configuring each protection device with position-specific inductance values. This creates local differentiation in the electromagnetic characteristics of protection devices, enabling the system to identify fault locations precisely while maintaining fast response times. The local quality principle resolves the contradiction by allowing uniform response speed across all devices while achieving precise location identification through differentiated inductance parameters.
Solution Approach 2:
The patent implements preliminary action by pre-configuring different inductance values in magnetic devices at various grid positions before faults occur. This preliminary differentiation of inductance parameters enables the control system to quickly identify fault locations as soon as a fault current flows, without requiring additional measurement time. The pre-established inductance variations allow simultaneous fast response and precise location identification.
3Ease of operation
If magnetic devices with position-dependent inductance values are used to achieve selective disconnection, then the selectivity is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by implementing position-dependent inductance values in magnetic devices, which provides the necessary selectivity for differentiated disconnection. However, to manage the resulting complexity, the system uses a centralized control device that automatically determines fault locations based on current measurements and triggers appropriate protection devices. This approach maintains selectivity while reducing operational complexity through automated control logic.
Solution Approach 2:
The patent implements feedback by using the control device to continuously monitor current flow and inductance characteristics, automatically identifying fault locations and triggering the appropriate protection devices. The feedback mechanism processes information from the differentiated inductance configurations and translates it into selective disconnection actions, thereby managing device complexity through intelligent control while maintaining high selectivity.
4Reliability
If all protection devices intervene simultaneously during a fault, then the grid protection coverage is improved, but the loss of operational capacity increases due to unnecessary disconnections
Solution Approach 1:
The patent implements parameter changes by using position-dependent inductance values to differentiate the electromagnetic response of protection devices. This allows the control system to identify the specific location of a fault and trigger only the necessary protection devices, preventing unnecessary disconnections. The parameter differentiation maintains comprehensive protection coverage while minimizing outage duration by avoiding blanket disconnections of healthy grid portions.
Solution Approach 2:
The patent applies the taking out principle by extracting and isolating only the faulted portion of the grid for disconnection, while leaving the rest of the grid operational. The position-dependent inductance configuration enables the control system to precisely identify and isolate the specific branch or node where the fault occurs, rather than disconnecting entire sections. This resolves the contradiction by maintaining full protection coverage while minimizing the loss of operational capacity through targeted disconnection.
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 enables precise identification and isolation of faulted grid portions while maintaining normal operation of unaffected parts, reducing unnecessary outages and enhancing grid management efficiency.
Implementation Method 1
The one or more permanent magnets generate a magnetic flux bringing said magnetic body in a saturated condition in absence of a current feeding said one or more excitation coils
Implementation Method 2
at least one excitation coil is wound on said magnetic body in such a way to generate a magnetic flux having an opposite direction compared to the direction of the magnetic flux generated by said permanent magnets
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
A DC electric grid comprising a plurality of electric nodes, one or more electric branches electrically connecting said electric nodes and a plurality of protection devices arranged at said electric branches. Each protection device of the electric grid comprises a first terminal for coupling to a first branch portion and a second terminal for coupling to a second branch portion. Each protection device further comprises a switching assembly including one or more switching devices and a magnetic device electrically connected in series with said switching assembly between the first and second terminals of said protection device. The electric grid, according to the invention, further includes one or more control devices included in or operatively coupled to the above-mentioned protection devices. Each control device is configured to control one or more switching devices of the switching assembly of one or more protection devices to cause said switching devices to switch selectively between a closed state and open state.