Current Interrupting Arrangement With Resonance Circuit
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Solution Overview
Problem
Existing current interrupting technologies face challenges in efficiently handling high voltage breakdowns and achieving fast current interruption in both AC and DC systems, particularly in preventing fault currents from reaching dangerous levels and protecting sensitive equipment, with limitations in controllability and complexity in existing solutions.
Innovation Solution
A current interrupting arrangement featuring a parallel connection of two-pole branches with capacitors, inductors, and voltage control means, along with an over-voltage reducing circuit and a disconnecting switch, which generates an oscillating current to force current zero-crossing and includes a reverse current control mechanism to manage reverse currents, ensuring secure interruption and voltage limiting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a resonance circuit is used to generate oscillating current for forcing current zero-crossing, then fast current interruption is achieved, but the arrangement requires elaborate charging process and specific adaptation for each application
Solution Approach 1:
The capacitor in the resonance circuit is pre-charged to a voltage higher than the maximum system voltage before fault occurrence. This preliminary charging action eliminates the need for elaborate charging processes during operation and allows the resonance circuit to immediately generate sufficient oscillating current when activated, achieving fast current interruption without complex real-time charging control
Solution Approach 2:
The resonance circuit is designed with a capacitor charged to a universal voltage level that exceeds the maximum system voltage, making it applicable to different voltage levels and application scenarios. This universal design eliminates the need for specific adaptation for each application, as the same basic circuit topology can handle various voltage conditions by adjusting the initial charge voltage
2Speed
If a charged capacitor is used to force current zero-crossing in DC circuit breaker, then current interruption is achieved, but the solution has very limited controllability
Solution Approach 1:
The resonance circuit incorporates controllable switches (such as IGBTs or IGCTs) that dynamically control the timing and duration of oscillating current injection. This dynamic control capability allows precise adjustment of the current zero-crossing moment, enabling flexible and controllable current interruption unlike static capacitor discharge methods
Solution Approach 2:
The system includes control circuitry that monitors the current waveform and system conditions, providing feedback to adjust the resonance circuit activation timing and duration. This feedback mechanism enhances controllability by optimizing the oscillating current injection based on real-time measurements, ensuring reliable current zero-crossing under various operating conditions
3Speed
If mechanical contacts are separated to interrupt current, then physical separation is achieved, but arc generation occurs between contacts
Solution Approach 1:
The arc generated between separating contacts is converted into a beneficial tool by introducing a resonance circuit that forces the arc current to oscillate and reach zero-crossing. The arc, normally a harmful phenomenon, becomes the medium through which the oscillating current can be injected and controlled, enabling fast current interruption while the contacts separate mechanically
Solution Approach 2:
The resonance circuit acts as an intermediary between the mechanical contact separation and the current interruption. It introduces an oscillating current component that superimposes on the arc current, forcing the total current to zero-crossing before the contacts fully separate. This intermediary mechanism prevents sustained arcing and enables clean current interruption
4Speed
If resonance circuit generates oscillating current superposing arc current, then current zero-crossing is achieved, but the oscillation current is excited by arc voltage requiring auxiliary power supply
Solution Approach 1:
The capacitor in the resonance circuit is pre-charged to a voltage higher than the maximum system voltage before fault occurrence. This preliminary energy storage eliminates the need for auxiliary power supply during operation, as the pre-stored energy in the capacitor is sufficient to generate the required oscillating current when the fault occurs and the switch closes
Solution Approach 2:
The resonance circuit is designed to be self-sufficient by using a pre-charged capacitor that provides all necessary energy for generating oscillating current. The system serves itself by utilizing the stored energy in the capacitor rather than requiring continuous auxiliary power supply, achieving energy independence and simplifying the overall system architecture
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 effectively handles late voltage breakdowns and ensures secure current interruption by controlling the oscillating current to align with dielectric isolation strength, reducing the rate of current change and providing an alternative path for reverse currents, thereby preventing fault current escalation and protecting equipment.
Implementation Method 1
the branch containing the mechanical breaker and the two-pole together exhibit at least one resonance frequency
Implementation Method 2
a voltage-limiting energy-absorbing device is provided in the two-pole, which is adapted to limit the voltage across said capacitor and across the mechanical breaker when the latter is open (non-conducting) and to limit the voltage across the inductive element (32) in the loop constituted by the branch containing the mechanical breaker and the two-pole, if the voltage across the mechanical breaker breaks down
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An arrangement for interrupting current(10) comprising a first and a second terminal (11,12) being adapted to electrically connect two sections (100,200) of a power system is provided. A voltage control means (4) is controllable in use to inject energy into said loop to force a rapid increase of an alternating current (Io) flowing through said main branch (15) while it is being controlled to open to interrupt amain current (I), and whereby zero cross-over of the current (Isw) through the mechanical main circuit breaker (1) is realized as the amplitude (AIo) of the alternating current (Io) exceeds the amplitude (AI) of the main current. An energy absorbing device (2) is adapted to limit the voltage across said capacitor (31) and across said mechanical breaker (1) when the mechanical breaker is open. Furthermore, the energy absorbing device is adapted to limit the voltage across an inductive element (32) if the voltage across the mechanical breaker breaks down, at or immediately after an opening process, thereby limiting the rate-of-rise and the peak of the current through said loop.The rate-of-rise and the peak of the current through said resonant loopis thereby limited and an improved current interrupting capability is obtained regardless of the type of current to be interrupted. A system and a method for interrupting current are also provided.