Portable GFCI Circuit for Open Neutral Fault Interruption
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Solution Overview
Problem
Existing GFCI devices may fail to operate effectively in temporary power delivery systems with open neutral conditions, as they can be powered by the failed neutral conductor, leading to potential electric shock hazards.
Innovation Solution
A portable GFCI device with an electronic processor that compares current magnitudes and voltages between phase and neutral conductors, and a circuit breaker that interrupts power flow if thresholds are exceeded, ensuring protection against ground faults and open neutral conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a GFCI device is used in temporary power delivery systems, then ground fault protection is provided, but the device may fail to operate under open neutral conditions
Solution Approach 1:
The patent applies preliminary action by detecting open neutral conditions before they can cause hazardous voltage imbalances. The system proactively monitors neutral conductor integrity and trips the circuit breaker when an open neutral is detected, preventing the dangerous condition from developing rather than reacting after the hazard occurs.
Solution Approach 2:
The patent introduces an intermediary monitoring system that measures voltages between phase conductors and neutral, and between phase conductors and ground. This intermediary measurement system detects open neutral conditions indirectly through voltage imbalance detection, allowing the GFCI to respond to a condition it cannot directly sense.
2Reliability
If the GFCI device monitors current imbalance to detect ground faults, then ground fault protection is achieved, but the device cannot distinguish between ground faults and open neutral conditions
Solution Approach 1:
The patent transitions from single-dimension current imbalance detection to multi-dimensional voltage measurement. By adding voltage measurements between phase-neutral and phase-ground, the system creates additional detection dimensions that enable differentiation between ground faults and open neutral conditions, resolving the ambiguity of current-only monitoring.
Solution Approach 2:
The patent makes the detection system multi-functional by using the same voltage measurement circuitry to detect both ground faults and open neutral conditions. The voltage sensing mechanism serves multiple protective functions, eliminating the need for separate detection systems for different fault types.
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 interrupts current flow in case of ground faults and open neutral conditions, enhancing safety in temporary power delivery systems by ensuring reliable operation even when an open neutral condition occurs.
Implementation Method 1
comparing the amount of current going to and returning from the load along circuit conductors
Implementation Method 2
compare a first voltage between the first phase conductor and the neutral conductor to a second voltage between the second phase conductor and the neutral conductor
Implementation Method 3
open the circuit breaker to interrupt current flow from the power source to the booth stringer
Data Source
AI summary
A temporary power delivery system includes a power source, a booth stringer, and a portable GFCI device. The GFCI device is receives current from the power source by a first terminal and delivers current to the booth stringer by a second terminal. An electronic processor of the GFCI device compares a combined magnitude of current flowing through first and second phase conductors of the GFCI device to a magnitude of current flowing through a neutral conductor of the GFCI. The electronic processor also compares a first voltage between the first phase conductor and neutral conductor to a second voltage between the second phase conductor and neutral conductor. A circuit breaker of the GFCI device is opened if a difference between the combined magnitude of phase conductor current and neutral conductor current exceeds a first threshold or a difference between the first voltage and second voltage exceeds a second threshold.