Earth Leakage Circuit Breaker Harmonic Ratio Detection

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Earth leakage circuit breakers often malfunction by incorrectly detecting abnormal current due to characteristics of specific parts, leading to unnecessary circuit cutoffs, even when no abnormal current is present.

Innovation Solution

An earth leakage circuit breaker that includes a current sensing unit to detect both fundamental and harmonic components of current, using a controller to compare harmonic component ratios with thresholds to accurately determine abnormal current, thereby preventing malfunctions by considering both fundamental wave component values and peak current values.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the earth leakage circuit breaker detects peak current value from harmonic component, then the detection sensitivity is improved, but false detection occurs causing unnecessary circuit cutoff

Engineering Contradiction:

Improvedetection sensitivityVSAvoidfalse detection rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent segments the current signal into fundamental wave component and harmonic component through Fourier transform. The controller separately analyzes these components and applies different evaluation criteria: fundamental wave component is compared against leakage current threshold, while harmonic component ratio is compared against predetermined ratio threshold. This segmentation prevents false detection caused by harmonic peaks while maintaining detection sensitivity for actual leakage currents.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the detection parameter from simple peak current value to a composite evaluation involving fundamental wave component and harmonic component ratio. By transforming the current signal into frequency domain components and evaluating their ratio relationship, the system distinguishes between normal harmonic distortion and actual leakage current, thereby reducing false positives while maintaining detection accuracy.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the earth leakage circuit breaker uses only fundamental wave component for detection, then false detection is reduced, but detection accuracy for abnormal current decreases

Engineering Contradiction:

Improvefalse detection rateVSAvoiddetection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs preliminary Fourier transform analysis to separate fundamental wave and harmonic components before making the leakage detection decision. This preliminary action of decomposing the signal allows the system to pre-evaluate the harmonic component ratio and exclude its influence on the final detection judgment, thereby improving both reliability and accuracy.

Inventive Principle:

Principle #10Preliminary action

3Device complexity

If the earth leakage circuit breaker detects current without considering harmonic components, then the device complexity is reduced, but malfunction occurs due to characteristics of specific parts

Engineering Contradiction:

Improvedetection algorithm complexityVSAvoidmalfunction rate

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces simple peak value comparison with a signal processing approach using Fourier transform to decompose the current signal into frequency components. This substitution of detection mechanism allows the system to mathematically separate fundamental wave and harmonic components, evaluating each according to appropriate criteria. The increased computational complexity is offset by the elimination of malfunctions, achieving reliable detection without requiring additional hardware complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 improves the accuracy of abnormal current detection, reducing false positives and ensuring that the circuit is only cut off when actual abnormal current is present, thus preventing unnecessary cutoffs and enhancing protection.

Implementation Method 1

The converter is configured to convert the sensed current from an analog signal into digital data, and to perform Fourier transform with respect to the converted digital data to detect the fundamental wave component and the specific harmonic component

Methodology Applied

Scientific EffectFourier transform:

Data Source

PatentEP3496222B1Earth leakage circuit breaker based on the ratio of a specific harmonic current component to the fundamental wave current component

Publication Date: 2022.07.27 LSIS CO LTD

Figure 1~2
Figure 3
Figure 4

AI summary

An earth leakage circuit breaker includes a current sensing unit configured to sense current in a circuit, a converter configured to detect a fundamental wave component and a specific harmonic component from the sensed current, the specific harmonic component being one of a plurality of harmonic components, and a controller. The controller is configured to compare a harmonic component ratio with a threshold component ratio, to determine whether the sensed current is abnormal current, and to control cutoff of the circuit according to the result of determination. The harmonic component ratio is a ratio of the specific harmonic component to the fundamental wave component. The converter is configured to convert the sensed current from an analog signal into digital data and to perform Fourier transform with respect to the converted digital data to detect the fundamental wave component and the specific harmonic component.