HVDC Switch Segmentation for Reliable Current Interruption
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Solution Overview
Problem
High-voltage direct current (HVDC) circuit breakers face challenges in reliably switching off both rated and short-circuit currents while ensuring galvanic isolation, particularly as rated voltages increase and short-circuit currents become multiples of rated currents, with existing solutions being complex and costly.
Innovation Solution
A switch comprising a series circuit with a vacuum circuit breaker for current interruption and a gas-insulated or low-oil-content circuit breaker for voltage isolation, along with a counter-current device using a high-voltage capacitor and semiconductor switches to reduce current through the vacuum breaker, and a current limiter to manage short circuits, all controlled by a device that determines current changes and generates a counter-current for efficient switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single circuit breaker is used for HVDC current interruption, then the construction is simple, but it cannot reliably switch off both rated and short-circuit currents while ensuring galvanic isolation
Solution Approach 1:
The circuit breaker is divided into two separate switching devices: a vacuum circuit breaker for current interruption and a gas-insulated circuit breaker for voltage isolation. This segmentation allows each device to be optimized for its specific function, with the vacuum breaker handling current zero-crossing interruption and the gas-insulated breaker providing galvanic isolation and withstanding voltage stress.
Solution Approach 2:
A counter-current device using a high-voltage capacitor and semiconductor switch is introduced as an intermediary to generate a counter-current that forces the load current to zero. This mediator enables the vacuum circuit breaker to interrupt current reliably by creating a zero-crossing condition, which would not naturally occur in DC circuits.
2Power
If rated voltage increases to 800 kV or 1000 kV, then transmission capacity improves, but the difficulty of switching off short-circuit currents increases
Solution Approach 1:
The control device detects short-circuit conditions by monitoring current changes and preemptively activates the counter-current device before the vacuum circuit breaker attempts to interrupt the current. This preliminary action of generating the counter-current simplifies the switching task by forcing an early zero-crossing, making high-voltage switching more manageable.
Solution Approach 2:
The patent replaces traditional mechanical short-circuit breaking mechanisms with an electronic control system that uses semiconductor switches and capacitor-based counter-current generation. This substitution allows for faster, more precise control of current interruption at high voltages without relying on complex mechanical structures.
3Speed
If a vacuum circuit breaker is used for current interruption, then switching speed improves, but galvanic isolation becomes insufficient
Solution Approach 1:
The switching function is segmented between two specialized devices: the vacuum circuit breaker handles the fast current interruption at zero-crossing, while the gas-insulated circuit breaker provides the necessary galvanic isolation and voltage withstanding capability. This division allows each component to excel at its specific function.
Solution Approach 2:
The gas-insulated circuit breaker serves multiple functions: it provides galvanic isolation, withstands high voltage stress, and maintains system reliability. By assigning this multi-functional role to the gas-insulated device, the vacuum breaker can focus solely on fast current interruption.
4Manufacturing precision
If superconducting solutions are used for current limiting, then current control precision improves, but system complexity and cost increase due to cryogenic requirements
Solution Approach 1:
The patent uses conventional inductors and capacitors with predictable, temporary current-limiting behavior during fault conditions, replacing expensive superconducting components. These standard electrical components provide sufficient current control precision for the application without requiring complex cryogenic infrastructure.
Solution Approach 2:
The patent replaces superconducting magnetic field-based current limiting with an electronic control system using semiconductor switches and capacitor-based counter-current generation. This substitution achieves comparable current control precision through electronic means rather than requiring complex superconducting physics infrastructure.
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
Enables reliable and efficient switching off of currents at low cost by generating a counter-current at zero crossing, preventing reignition and ensuring dielectric strength, thus addressing the complexity and cost issues of prior art solutions.
Implementation Method 1
the device for building up a counter-current comprises a high-voltage capacitor and a switch
Implementation Method 2
the first switching device preferably comprises a vacuum circuit breaker
Implementation Method 3
the second switching device preferably comprises a gas-insulated, oil-insulated or low-oil-content circuit breaker
Implementation Method 4
Said device can comprise, for example, an inductance in series with a parallel circuit comprising a nonlinear inductance and a capacitance
Data Source
AI summary
A switch for a high-voltage direct current transmission path includes a vacuum circuit breaker for disconnecting the transmission path and a gas-insulated circuit breaker for disconnecting the transmission path. The gas-insulated circuit breaker is connected in series with the vacuum circuit breaker. A device is provided for building up a counter-current against the current in the transmission path for the purpose of reducing the current across the vacuum circuit breaker. The elements of the switch are actuated by a control device in such a way that the switch is switched off at or close to the zero crossing of the current.