Grounded Neutral Fault Detection Using Adaptive Test Frequency

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Solution Overview

Problem

Existing ground fault circuit interrupt (GFCI) devices are disadvantaged in detecting neutral grounding faults, which can lead to bypassed protection and nuisance trips, causing potential damage and user dissatisfaction.

Innovation Solution

A grounded neutral fault detector is introduced, utilizing induction circuits to generate a leakage signal and a controller to determine the frequency of a test signal based on load noise analysis, injecting the test signal into the neutral conductor to measure impedance and accurately detect grounded neutral faults.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If test signal frequency is fixed, then detection is simpler, but load noise interference cannot be minimized

Engineering Contradiction:

Improvedetection complexityVSAvoidnoise interference

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent makes the test signal frequency dynamic rather than fixed. The controller selectively determines the frequency of the test signal based on the measured frequency spectrum of load noise, adjusting the test signal frequency to avoid noisy frequency components. This dynamic adaptation minimizes noise interference while maintaining relatively simple detection procedures.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the frequency parameter of the test signal based on measured load noise characteristics. By analyzing the frequency spectrum of load noise and selecting a test signal frequency that minimizes interference, the system achieves precise measurements without requiring complex detection algorithms or fixed frequency constraints.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively reduces nuisance trips and accurately detects grounded neutral faults, enhancing protection and reducing interference from load noise, thereby improving the reliability of fault detection in AC circuits.

Implementation Method 1

induction circuits configured to generate a leakage signal corresponding to a current imbalance between a line conductor and a neutral conductor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

measuring impedance of a current loop formed by a potential grounded neutral fault based on a second leakage signal corresponding to a second current imbalance with the test signal injected

Methodology Applied

Scientific EffectImpedance measurement: Electrical Resistance

Data Source

PatentUS11855442B2Systems and methods of grounded neutral fault detection by single frequency excitation and leakage spectral analysis

Publication Date: 2023.12.26 ABB (SCHWEIZ) AG

AI summary

A grounded neutral fault detector that includes induction circuits and a controller is provided. The controller is configured to determine a frequency of a test signal by measuring load noise based on a first leakage signal corresponding to a first current imbalance between the line conductor and the neutral conductor for the load without the test signal being injected, analyzing a frequency spectrum of the load noise, and selecting the frequency of the test signal. The controller is further configured to inject the test signal at the selected frequency to the neutral conductor, measure impedance of a current loop formed by a potential grounded neutral fault based on a second leakage signal corresponding to a second current imbalance with the test signal being injected, and determine a grounded neutral fault.