Compressible Multi-Cable Transit Seals for Arc-Resistant Enclosures
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Solution Overview
Problem
Conventional sealing methods for medium voltage electrical equipment compartments, particularly around cable passageways, are inadequate in preventing the spread of arc-generated gases, flames, and debris, which can compromise the integrity of arc-resistant enclosures and pose a risk to vulnerable control circuitry.
Innovation Solution
The use of flexible Multi Cable Transits (MCTs) with compressible modules and user-configurable compression rings to create sealed paths for cables between compartments, ensuring that arc gases and pressures are contained, thereby maintaining the arc-resistant rating of the enclosure without the need for retesting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sealing methods (silicone RTV) are used around cable passageways, then installation is possible, but the seal reliability is insufficient and may break when cables move
Solution Approach 1:
The patent employs a flexible grommet made of elastomeric material that forms a compliant seal around the cable bundle. This flexible membrane structure can deform to accommodate cable movements while maintaining the seal integrity, preventing arc gases from penetrating through the cable passageway.
Solution Approach 2:
The sealing solution changes the physical state of the sealing material from rigid (silicone RTV) to elastomeric and compressible. The grommet material is selected to have specific durometer properties that allow it to be compressed during installation and then recover to maintain constant sealing pressure, adapting to thermal expansion and cable movement.
2Adaptability or versatility
If cables are allowed to pass between compartments, then electrical connectivity is maintained, but arc gases can breach the cubicle through unsealed passageways
Solution Approach 1:
The grommet acts as an intermediary element between the cable bundle and the compartment wall. It provides a transition zone that allows the cable to pass through while maintaining the barrier function against arc gases. The grommet material is selected to be resistant to degradation from arc exposure while maintaining flexibility.
Solution Approach 2:
The grommet is installed within a mounting plate or flange that is itself mounted in the compartment wall. This nested arrangement allows the grommet to be pre-positioned and secured, with the cable then passing through the grommet's central opening, creating multiple layers of protection and ensuring proper sealing geometry.
3Reliability
If a sealed enclosure is designed to withstand arcs, then control circuitry is protected, but manufacturing precision is difficult to achieve with conventional sealing
Solution Approach 1:
The elastomeric grommet possesses self-sealing properties where the material's elasticity automatically compensates for minor variations in installation torque, cable position, and thermal expansion. The grommet maintains constant contact pressure around the cable bundle without requiring precision adjustment, making the sealing process more forgiving and consistent across different installation scenarios.
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 MCTs effectively prevent the passage of harmful gases, flames, and debris between compartments, ensuring the integrity of the arc-resistant enclosure and protecting vulnerable equipment, thus maintaining the equipment's rating and preventing damage to control circuitry.
Implementation Method 1
a compression ring configured to compress the cable seal around the cable
Implementation Method 2
an elastomeric cable seal configured to surround the cable
Data Source
AI summary
An apparatus includes an enclosure comprising first and second abutting compartment and at least one cable passing between the first and second compartments through a sealing multi-cable transit mounted in a wall shared by the first and second compartments. The first compartment may contain arc-generating equipment and the second compartment may contain equipment vulnerable to arc damage. The first compartment may include a medium-voltage cubicle and the second compartment may include a low-voltage control cubicle.