Frangible Stop Member for Separable Loadbreak Connector Piston Control

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Solution Overview

Problem

Existing separable loadbreak connectors face reliability issues during fault closure due to uncontrolled arcing and piston ejection, as the rapid expansion of air during fault closure operations exceeds the stopping capability of traditional piston stops, leading to potential uncontrolled arcing and fault-to-ground conditions.

Innovation Solution

The implementation of a contact tube with radially inwardly extending stop members or projections that cant the piston, combined with axial grooves and knurled surfaces, to increase friction and slow the piston's movement during fault closure, thereby reducing the impact force and preventing piston ejection, while maintaining electrical contact and arc quenching efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a rigid piston stop is provided in the contact tube to limit piston movement during fault closure, then the piston movement is constrained, but the piston can still accelerate to high speed and exit the bushing due to rapid air expansion

Engineering Contradiction:

Improvepiston control during fault closureVSAvoidpiston acceleration during fault closure

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent applies beforehand cushioning by providing a frangible stop member that can break under excessive force. The stop member is positioned to engage the piston during normal operation, but is designed to fracture when the piston acceleration exceeds safe limits during fault closure, preventing piston ejection while allowing controlled movement under extreme conditions.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent changes the mechanical properties of the stop member by making it frangible rather than rigid. This parameter change allows the stop to provide resistance during normal operation but fail safely under extreme fault conditions, transforming the stop from a rigid constraint to a controlled failure mechanism.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the piston is allowed to move freely during fault closure, then the connector structure is simpler, but uncontrolled arcing and fault to ground conditions occur

Engineering Contradiction:

Improveconnector structureVSAvoiduncontrolled arcing and fault to ground

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The frangible stop member provides beforehand cushioning by being pre-positioned to engage the piston. During normal operation and controlled fault closure, it limits piston movement to prevent uncontrolled arcing. The frangible design ensures it breaks only when necessary, maintaining simplicity while preventing harmful effects.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The stop member acts as an intermediary between the piston and the contact tube. It mediates the interaction by providing controlled resistance to piston movement, preventing direct uncontrolled contact and arcing between the male and female contacts while allowing the piston to move when needed.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a frangible stop member is used to prevent piston ejection, then piston control is improved, but the stop member may break during normal operation if not properly designed

Engineering Contradiction:

Improvepiston containment during fault closureVSAvoidstop member strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The stop member's strength parameter is carefully controlled to be frangible - strong enough to contain the piston during normal operation but weak enough to break under excessive fault closure forces. This parameter optimization prevents both piston ejection and premature failure during normal operation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The stop member transitions from a static rigid component to a dynamic frangible component that changes its mechanical properties based on applied force. It maintains structural integrity during normal operation but is designed to fail dynamically when force exceeds safe thresholds, adapting its behavior to operational conditions.

Inventive Principle:

Principle #15Dynamics

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 effectively slows the piston's movement and reduces the impact force during fault closure, preventing uncontrolled arcing and piston ejection, enhancing the reliability and safety of the connector by maintaining stable electrical engagement and reducing the risk of fault-to-ground conditions.

Implementation Method 1

sufficient energy can be generated that rapidly expands the air present in the connector during a fault-close operation that slowing or stopping the piston using a typical piston stop can not be achieved

Methodology Applied

Scientific EffectRapid expansion of air: Adiabatic Heating

Implementation Method 2

If the piston can be prevented from accelerating to a high speed or slowed prior to engaging the piston stop, the piston may exit the bushing leading to uncontrolled arcing and fault to ground

Methodology Applied

Scientific EffectImpact force: Impact Force

Data Source

PatentUS7862354B2Separable loadbreak connector and system for reducing damage due to fault closure

Publication Date: 2011.01.04 EATON INTELLIGENT POWER LTD

AI summary

Separable loadbreak connectors include an interference element spaced about the contact tube that is configured to engage a portion of a connector piston.