Mechanically Interlocked Grounding Switch for Vacuum Circuit Breakers
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Solution Overview
Problem
In wind farms, the interruption of electrical circuits using existing vacuum circuit breakers can lead to transient overvoltages when the circuit is opened, causing potential damage to wind energy generators and other circuitry, and requires the use of costly grounding transformers with significant energy losses.
Innovation Solution
A vacuum circuit breaker with an integral high-speed, mechanically interlocked grounding switch that rapidly connects and disconnects the circuit to ground, eliminating the need for grounding transformers and minimizing energy losses, and operates effectively at 34.5 kilovolts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing vacuum circuit breakers are used to interrupt electrical circuits, then circuit interruption function is achieved, but transient overvoltages occur causing damage to generators and circuitry
Solution Approach 1:
The grounding switch closes before the main breaker opens, establishing a ground path in advance. This preliminary action ensures that when the circuit is interrupted, the ground path is already in place to safely dissipate transient overvoltages, preventing damage to generators and circuitry.
Solution Approach 2:
The grounding switch acts as an intermediary element between the circuit and ground. By introducing this intermediate component, transient overvoltages are safely directed to ground through the grounding switch, protecting the main circuit components from voltage damage.
2Object-affected harmful factors
If grounding transformers are used to prevent overvoltages, then overvoltage protection is achieved, but energy losses increase and operational costs rise
Solution Approach 1:
The invention extracts the essential grounding function from the complex grounding transformer system and implements it through a simple grounding switch mechanism. This removes the energy-consuming transformer component while retaining the protective grounding function, eliminating unnecessary energy losses.
Solution Approach 2:
The grounding switch provides a simple, low-cost alternative to expensive grounding transformers. Although the switch operates intermittently (closing only when needed for protection), its simplicity and low operational cost make it an economically superior solution for overvoltage protection.
3Speed
If a mechanically interlocked grounding switch is implemented, then switching speed increases, but device complexity increases
Solution Approach 1:
The grounding switch mechanism is mechanically integrated with the existing vacuum circuit breaker structure. By merging the grounding switch with the breaker's mechanical components, the patent achieves coordinated operation without adding separate complex control systems, thus improving switching speed while limiting complexity growth.
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
The solution enables instantaneous switching of the circuit to ground, reducing the risk of overvoltages and eliminating the need for grounding transformers, thereby minimizing energy losses and operational costs while ensuring reliable operation in wind farm environments.
Implementation Method 1
A vacuum circuit breaker with an integral high-speed, mechanically interlocked grounding switch
Implementation Method 2
When the electrodes are parted, an arc is produced and supported by metallic vapor boiled from the electrodes. Vapor particles expand into the vacuum and condense on solid surfaces. At a natural current zero the vapor particles disappear and the arc is extinguished.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A circuit breaker apparatus (44) with an integrated grounding switch has a housing (74) with first (78) and second bushings (80) extending outwardly of the housing (74). A first vacuum bottle (90) is positioned in the housing (74) and has a pair of contactors (122 and 124) therein. A second vacuum bottle (92) is positioned in the housing and has a pair of contactors (128 and 130) therein. A mechanical linkage (88) is movable between a first position and a second position. The first position electrically connects the first bushing (78) to the second bushing (80). The second position electrically connects the first bushing (78) to ground. The first vacuum bottle (90) and the second vacuum bottle (92) are longitudinally aligned. The mechanical linkage (88) is interposed between the first (90) and second vacuum bottles (92).