Link Disconnect Box for Network Protector Isolation
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Solution Overview
Problem
In electrical power distribution systems, network protectors on the low voltage side cannot be isolated from low voltage current, posing safety risks for utility workers during maintenance, as the existing networked connections prevent isolation of the network protector itself, leading to potential arc flash hazards.
Innovation Solution
A link disconnect box is designed to be retrofitted onto existing network protector terminals, featuring a top and bottom bus bar configuration with an air gap that can be bridged by an electrical link, allowing for safe disconnection from the low voltage network, enabling isolation of the network protector from load side connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If network protectors are connected to the low voltage network for continuous operation, then power supply reliability is improved, but safety risks increase for utility workers during maintenance
Solution Approach 1:
The network protector system is segmented into isolated sections using disconnect boxes with individual breakers for each phase. This allows specific sections to be disconnected for maintenance while keeping other sections operational, maintaining power supply reliability while enabling safe maintenance work by isolating harmful electrical energy.
Solution Approach 2:
Disconnect boxes are introduced as intermediary devices between network protectors and the low voltage network. These boxes provide a physical and electrical barrier that isolates workers from energized components during maintenance, eliminating arc flash hazards while allowing continuous network operation through alternative paths.
2Duration of action of stationary object
If network protectors remain connected to the low voltage network, then continuous power delivery is maintained, but isolation for maintenance becomes impossible
Solution Approach 1:
The low voltage network is divided into manageable sections with individual disconnect boxes. Each breaker can be independently operated to isolate specific network protectors for maintenance while maintaining power delivery through other parallel paths in the network, achieving both continuous power delivery and maintenance isolation.
Solution Approach 2:
The system transitions from a static connected state to a dynamically controllable state with multiple on/off positions. Disconnect boxes provide dynamic control over electrical connections, allowing the system to switch between operational and maintenance modes as needed, enabling both continuous power delivery and isolation capability.
3Device complexity
If existing network protector terminals are used without modification, then device simplicity is maintained, but safety isolation cannot be achieved
Solution Approach 1:
Disconnect boxes are nested onto existing network protector terminals, with the breaker mechanism housed within the box structure. This nested configuration adds isolation functionality while minimizing overall structural complexity, as the new device integrates with and attaches to the existing terminal infrastructure rather than replacing it entirely.
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 link disconnect box allows for safe isolation of network protectors from low voltage networks, reducing the risk of arc flash and enabling safe maintenance by creating an air gap that can be bridged electrically, thus protecting utility workers from electrical hazards.
Implementation Method 1
An air gap electrically isolates the top bus bar from the bottom bus bar within the cavity
Implementation Method 2
An electrical link connects and disconnects the top bus bar and the bottom bus bar by electrically bridging the air gap
Data Source
AI summary
A link disconnect box enables easy field retrofitting of network protectors. The link disconnect box has an outer casing that defines a cavity with a front face opening and top and bottom bus bar openings. Top and bottom terminals seal the top and bottom bus bar openings. The bottom terminal is configured to connect to an existing terminal of the network protector. A removable face plate seals shut the front face opening. Top and bottom bus bars electrically connect to the top and bottom terminals, extending through the respective top and bottom bus bar openings towards each other, with an air gap between them within the cavity. An electrical link, which can be bolted closed, connects and disconnects the top and bottom bus bars by electrically bridging the air gap.