DC Current Handling Device with Auxiliary Branch for Inrush Limitation
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Solution Overview
Problem
High inrush and fault currents during energizing in direct current power transmission systems pose challenges for existing technologies, particularly due to large stray capacitance in long transmission lines and cables, leading to inefficient current handling and costly, large-capacity surge arresters with low operating frequencies.
Innovation Solution
A current handling device with parallel branches, including a main branch with a circuit breaker switch and an auxiliary branch with a resistor and auxiliary switch, allows for inrush current limitation by closing the auxiliary switch during high inrush currents, providing a current limitation path and enabling standard component sizing and full-function DC breaker operation without additional equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a DC breaker with surge arrester is used to limit inrush current, then inrush current limitation is achieved, but the surge arrester requires large capacity and operating frequency is limited due to heat dissipation time
Solution Approach 1:
The current handling device is segmented into multiple parallel branches: a main branch with circuit breaker switch elements for fault current handling, and auxiliary branches with resistors and auxiliary switches for inrush current limitation. This segmentation allows independent optimization of each branch for its specific function, enabling the surge arrester to be sized appropriately without requiring large capacity for inrush current handling.
Solution Approach 2:
Resistors are introduced as intermediary elements in the auxiliary branches to limit inrush current. These resistors act as mediators that temporarily handle the inrush current limitation function, allowing the surge arrester to operate within its optimal capacity range and frequency characteristics without being overloaded by frequent inrush current events.
2Object-affected harmful factors
If DC breaker components are sized for handling energizing currents, then inrush current limitation is achieved, but component size and cost increase
Solution Approach 1:
The device segments the current handling function into separate branches: auxiliary branches with resistors for inrush current limitation and a main branch with circuit breakers for fault current handling. This allows each component to be sized appropriately for its specific function rather than requiring all components to handle the maximum inrush current, reducing overall component size and cost.
Solution Approach 2:
The auxiliary branches with resistors provide partial current limitation action during energizing, handling only the inrush current component while allowing the main branch to handle normal operating and fault currents. This partial action approach enables smaller, more cost-effective component sizing.
3Object-affected harmful factors
If section-by-section switching with surge arrester is used for energizing, then inrush current limitation is achieved, but the control complexity and system requirements increase
Solution Approach 1:
The invention merges the inrush current limitation function and fault current handling function into a single integrated current handling device. The auxiliary branches with resistors and auxiliary switches handle inrush current, while the main branch with circuit breakers handles faults, eliminating the need for separate control systems and reducing overall complexity.
Solution Approach 2:
The current handling device achieves multi-functionality by combining inrush current limitation and fault current handling in one device. The auxiliary branches provide inrush limitation while the main branch provides fault protection, allowing a single device to perform multiple functions that previously required separate equipment.
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 allows for efficient inrush current limitation and fault handling, enabling standardized component design, reduced costs, and higher operating frequencies without the need for large surge arresters, facilitating simpler DC system energization and reduced substation space requirements.
Implementation Method 1
an auxiliary branch comprising at least one resistor in series with an auxiliary switch, where the main branch is a part of a circuit breaking arrangement of the current handling device and the auxiliary switch is operative to close upon the occurrence of a high inrush energizing current in order to provide a current limitation path through the auxiliary branch
Data Source
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AI summary
The invention is directed towards a current handling device for connection in series with a transmission medium and a method of handling high current levels in a direct current power transmission system, where the current handling device (20) comprises a set of parallel branches, the branches comprising a main branch comprising at least one circuit breaker switch element (S1) and an auxiliary branch comprising at least one resistor (Ra) in series with an auxiliary switch (Sa), where the main branch is a part of a circuit breaking arrangement of the current handling device and the auxiliary switch (Sa) is operative to close upon the occurrence of a high inrush energizing current in order to provide a current limitation path through the auxiliary branch.