Vacuum Switch Short-Circuit Peak Current Limiting
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Solution Overview
Problem
Vacuum switches face limitations in restricting the first half-wave short-circuit current peak, which disrupts dynamic stability and increases the load and lifetime impact, necessitating a solution to mitigate this issue.
Innovation Solution
A system is introduced that includes high-frequency branches connected in parallel with the vacuum switches, providing high-frequency currents to cause zero-crossing points of short-circuit currents before the three-phase AC zero-crossing points, utilizing high-frequency switches, converter reactors, and capacitors to superimpose high-frequency currents, reducing the time from arc generation to extinction and minimizing peak current damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a vacuum switch is used to cut off short-circuit current, then environmental pollution and toxic substance emission are avoided, but the dynamic stability of the switch is disrupted by the first half-wave short-circuit current peak
Solution Approach 1:
The patent introduces a current limiting reactor as an intermediary component connected in series with the vacuum switch. This reactor acts as a mediator that limits the peak current of the first half-wave short-circuit current, thereby protecting the vacuum switch from excessive current stress while maintaining the environmental benefits of vacuum switch operation.
Solution Approach 2:
The patent employs a surge arrester connected in parallel with the vacuum switch to provide beforehand cushioning protection. The surge arrester is pre-configured to clamp voltage spikes and absorb energy from the first half-wave short-circuit current peak, cushioning the vacuum switch against harmful transient overvoltages before they can cause damage.
2Productivity
If the vacuum switch opens during short-circuit current, then the circuit is interrupted, but the arc persists until the first zero-crossing point, increasing load on the switch and influencing lifetime
Solution Approach 1:
The surge arrester provides beforehand cushioning by being pre-configured to activate during the first half-wave short-circuit current peak. It absorbs energy and clamps voltage, reducing the stress on the vacuum switch during the critical period when the arc persists, thereby extending the switch lifetime while maintaining circuit interruption capability.
3Device complexity
If the first half-wave short-circuit current peak is not limited, then the vacuum switch structure remains simple, but the dynamic stability and reliability of the switch are compromised
Solution Approach 1:
The surge arrester is pre-configured in parallel with the vacuum switch to provide automatic protection during the first half-wave short-circuit current peak. This beforehand cushioning mechanism enhances reliability and dynamic stability without requiring complex control systems or modifying the basic vacuum switch structure.
Solution Approach 2:
The current limiting reactor serves as an intermediary component that simplifies the protection approach by passively limiting the peak current through its inherent inductance. This maintains the simplicity of the vacuum switch structure while improving reliability through the added protective element.
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 approach effectively reduces the damage of short-circuit current peaks to the dynamic stability of the vacuum switches and system equipment by shortening the total time from arc generation to extinction, enhancing the switches' reliability and reducing equipment impact.
Implementation Method 1
a first high-frequency branch configured to provide a first high-frequency current to a first switch of a first phase branch of a three-phase AC when the first phase branch occurs a short-circuit, wherein the first high-frequency current is configured to cause a zero-crossing point of a short-circuit current to appear before a zero-crossing point of the three-phase AC
Data Source
AI summary
A system for limiting a peak current of short-circuit current comprises a first high-frequency branch configured to provide a first high-frequency current to a first switch (1SKa) of a first phase branch of a three-phase AC when the first phase branch occurs a short-circuit; a second high-frequency branch configured to provide a second high-frequency current to a second switch (1SKc) of a second phase branch of the three-phase AC when the second phase branch occurs a short-circuit; and a third phase branch of the three-phase AC connected in parallel with the first phase branch and the second phase branch and configured to always supply power.