AFCI Outlet Upstream Parallel Arc Fault Protection

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Solution Overview

Problem

Conventional arc fault circuit interrupter (AFCI) devices cannot detect and interrupt upstream parallel arc faults, allowing hazardous arcing currents to continue and posing a fire risk due to their inability to react quickly enough.

Innovation Solution

An AFCI outlet with a switching element coupled between the line and neutral conductors, a voltage sensor, and a current sensor that detects a large voltage drop without corresponding current increase, triggering the switching element to create a low resistance path and trip the upstream conventional thermal-magnetic circuit breaker.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional AFCI outlets are used to detect arc faults, then downstream parallel arc faults and series arc faults can be detected, but upstream parallel arc faults cannot be detected or interrupted

Engineering Contradiction:

Improvearc fault detection capabilityVSAvoidcoverage of fault detection zones

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Instead of trying to detect upstream arc faults directly at the outlet where conventional AFCI devices fail, the invention inverts the approach by using the outlet's switching element to actively create a controlled short circuit condition that forces the upstream fault current to exceed the circuit breaker's trip threshold. This indirect method allows the outlet to protect against faults upstream of itself, expanding its protective coverage beyond what conventional direct detection methods achieve.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If conventional circuit breakers are used to interrupt arc faults, then power can be interrupted, but the response time is too slow to prevent fire hazards

Engineering Contradiction:

Improvefire hazard preventionVSAvoidresponse time to arc fault

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The invention performs preliminary action by detecting the arc fault condition first through voltage and current sensing, then pre-conditioning the circuit by closing the switching element to create a low-resistance path. This preliminary setup ensures that when the fault is detected, the system is already prepared to rapidly escalate the current to trip levels, significantly reducing the response time compared to waiting for the conventional circuit breaker's thermal-magnetic mechanism to react.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The switching element acts as an intermediary between the detection system and the circuit breaker. It mediates the transition from detection to interruption by first closing to create a controlled short circuit condition, which then forces the upstream circuit breaker to trip. This intermediary action bridges the gap between slow thermal-magnetic breakers and the need for rapid arc fault response.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If the switching element is closed to create a low resistance path for upstream fault interruption, then the circuit breaker trips faster, but this creates an overcurrent condition

Engineering Contradiction:

Improvecircuit breaker trip speedVSAvoidovercurrent condition

Core Design Contradiction:

SpeedVSObject-generated harmful factors

Solution Approach 1:

The invention converts the harmful overcurrent condition into a beneficial outcome. By deliberately closing the switching element to create a controlled short circuit, the system generates excessive current that, while potentially harmful in normal circumstances, serves the specific purpose of forcing the upstream circuit breaker to trip rapidly. The harm (overcurrent) is transformed into the benefit (fast protection against upstream arc faults).

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Enables detection and interruption of upstream parallel arc faults, reducing the risk of fire by ensuring the current exceeds the overcurrent trip level of the branch circuit breaker, and allows for reset capability without additional sensor components or communication to an electronic upstream circuit breaker.

Implementation Method 1

sensing a large voltage drop but no current

Methodology Applied

Scientific EffectVoltage drop detection: Ohm's Law

Implementation Method 2

sensing a large voltage drop but no current

Methodology Applied

Scientific EffectCurrent detection: Electrical Resistance

Implementation Method 3

the switching element is closed and current flows through the relatively lower resistance switching element

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentEP3017516B1Upstream parallel arc fault outlet protection method

Publication Date: 2021.09.15 SCHNEIDER ELECTRIC USA INC

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AI summary

An arc fault circuit interrupter (AFCI) outlet is disclosed which detects and interrupts upstream parallel arc faults. The example AFCI outlet includes a switching element coupled between the line and neutral conductors at the outlet. The outlet also includes a voltage sensor and a current sensor. A parallel upstream arc fault is detected from a sensed voltage drop and no corresponding increase in current. On detecting the arc fault, the switching element is closed and current flows through the relatively lower resistance switching element interrupting power through the arc fault. The closed switching element results in an overcurrent condition causing an upstream conventional thermal-magnetic circuit breaker to trip.