Integrated Fuse Relay Assembly for PV String Protection
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Solution Overview
Problem
Fuses in photovoltaic systems are limited to protecting strings from over-current conditions and fail to provide protection against other faults such as reverse current conditions, necessitating additional protection measures for strings.
Innovation Solution
A fuse assembly incorporating a relay with separable contacts and an operating mechanism, along with a control circuit, is introduced to provide comprehensive protection by interrupting current flow in response to faults, including over-current, reverse current, and arc fault conditions, within a string protector system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple fuse is used to protect photovoltaic strings, then over-current protection is provided, but protection against other faults such as reverse current conditions is not provided
Solution Approach 1:
The patent combines a fuse and a relay into a single integrated string protector assembly. The fuse provides over-current protection while the relay provides additional protection against reverse current and other faults. By merging these components into one device with shared housing and coordinated operation, the patent achieves comprehensive protection without requiring separate protective devices, thus improving reliability while controlling complexity.
Solution Approach 2:
The string protector assembly is designed to perform multiple protective functions: over-current protection via the fuse, reverse current protection via the relay, and arc fault detection via the control circuit. This multi-functional design allows a single device to replace multiple separate protective devices, expanding protection coverage without proportionally increasing device complexity.
2Reliability
If additional protection measures are added to protect against reverse current and other faults, then protection coverage is improved, but device complexity increases
Solution Approach 1:
The patent integrates the fuse, relay, control circuit, and housing into a single compact string protector assembly. This merging approach allows multiple protective functions to be implemented in one device rather than requiring separate devices for each function, thereby improving protection coverage while minimizing the increase in overall system complexity.
Solution Approach 2:
The control circuit acts as an intermediary that coordinates between the fuse and relay components. It monitors electrical parameters and triggers appropriate protective actions by operating the relay or allowing the fuse to blow, thereby integrating multiple protection mechanisms into a unified system that manages complexity through centralized control.
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 effectively enhances protection for photovoltaic strings by enabling the detection and interruption of various fault types, ensuring safer and more reliable operation of photovoltaic systems beyond just over-current conditions.
Implementation Method 1
The conductive element heats up due to current flowing therethrough. The fuse is designed such that when the current flowing through the power circuit exceeds a predetermined level, the conductive element becomes hot enough to melt and interrupt the current flowing through the power circuit.
Implementation Method 2
a relay electrically connected in series with the fuse, the relay disposed in the space defined by the fuse holder and including separable contacts, an operating mechanism structured to open and close the separable contacts
Data Source
AI summary
A fuse assembly structured for use with a power circuit includes: a fuse holder defining a space and including first and second terminals structured to electrically connect to the power circuit; a fuse disposed in the space defined by the fuse holder; and a relay disposed in the space defined by the fuse holder. The relay includes separable contacts, an operating mechanism structured to open and close said separable contacts, and a control circuit cooperating with said operating mechanism to cause said operating mechanism to open or close said separable contacts. Current flowing between the first and second terminals flows through the separable contacts and the fuse and opening the separable contacts interrupts said current flowing between said first and second terminals.