Breaker Circuit Arc Suppression via Commutating Voltage
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Solution Overview
Problem
Existing breaker circuits for high voltage environments face challenges such as arcing in mechanical switches and high losses in solid state switches, which are exacerbated by the need for multiple solid state switches in series, leading to inefficiencies and equipment wear.
Innovation Solution
A breaker circuit that combines an isolation element, an energy absorption element, and a commutating voltage source with a switchable bypass path, utilizing components like active filters and capacitors to divert current away from mechanical switches during faults, reducing wear and losses by operating at lower voltages and sharing current paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical switches are used in high voltage environments, then the circuit can be opened to prevent current flow, but arcing occurs on opening causing equipment wear and potential danger
Solution Approach 1:
The breaker circuit performs preliminary actions by first closing the bypass path switches and opening the auxiliary breaker to divert current away from the mechanical switch before the mechanical switch opens. This sequence prevents arcing at the mechanical switch contacts by ensuring current flows through the bypass path with lower impedance, eliminating the harmful arcing effect while maintaining the fault isolation capability
Solution Approach 2:
The bypass path consisting of bypass switches and the auxiliary breaker acts as an intermediary current path. When activated, this intermediary path provides an alternative route for current flow, preventing direct current interruption at the mechanical switch and thereby eliminating arcing. The intermediary path allows the mechanical switch to open under zero-current conditions, resolving the contradiction between fault isolation and arcing prevention
2Object-affected harmful factors
If solid state switches are used to handle full voltage, then no arcing occurs, but multiple switches in series are required causing significant losses
Solution Approach 1:
The auxiliary breaker (solid state switch) is designed to handle only the commutating voltage required to divert current to the bypass path, rather than the full system voltage. This partial action approach reduces the voltage stress on solid state switches, allowing fewer switches to be used in series, thereby reducing the associated conduction losses while still achieving arc-free operation during the commutation phase
Solution Approach 2:
The solid state auxiliary breaker performs preliminary current diversion before the mechanical switch opens. By establishing the bypass current path in advance using the auxiliary breaker, the system eliminates arcing at the mechanical switch without requiring the full voltage capability across multiple solid state switches, thus reducing energy losses while achieving the arcing elimination benefit
3Reliability
If multiple solid state switches are connected in series to handle full voltage, then the circuit can operate without arcing, but the losses associated with their presence become appreciable
Solution Approach 1:
The auxiliary breaker is configured to provide only the necessary commutating voltage for current diversion, which is less than the full system voltage. This partial voltage provision reduces the number of solid state switches required in series, thereby minimizing their cumulative conduction losses and improving circuit efficiency while maintaining arc-free operation during fault conditions
Solution Approach 2:
The bypass path components (bypass switches and auxiliary breaker) serve dual functions: they provide a current diversion path for fault isolation and simultaneously act as a low-loss alternative to having multiple solid state switches in the main circuit during normal operation. This multi-functionality improves productivity by reducing overall circuit losses while maintaining reliability
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 configuration reduces the risk of arcing and wear on mechanical switches, minimizes losses in solid state switches, and allows for efficient operation with reduced additional components, enhancing reliability and cost-effectiveness by utilizing existing converter components for both fault and non-fault conditions.
Implementation Method 1
a commutating voltage source arranged to provide a source of commutating voltage to divert current away from the isolation element
Implementation Method 2
an energy absorption element, capable of receiving energy remaining in the circuit following activation of the isolation element
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
In one aspect, a breaker circuit arranged to isolate a converter (300, 400, 500) from a direct current network (204) in the event of a fault condition is described. The breaker circuit comprises an isolation element (104) such as a mechanical switch arranged, on activation, to prevent current flow between the network (204) and the converter (300, 400, 500) and an energy absorption element (1 12, 414, 556), capable of receiving energy remaining in the circuit following activation of the isolation element (104). Also provided is a commutating voltage source (106, 206, 570) arranged to provide a source of commutating voltage to divert current away from the isolation element (104) and a switchable isolation element bypass path (1 10) arranged to the receive the diverted current. At least one of the energy absorption element (1 12, 414, 556), the commutating voltage source (106, 206, 570) and the isolation element bypass path (1 10) is operable in a non-fault condition to provide a functional component of the converter. Converters and methods of operation thereof are also described.