Transformer Self-Test Using Frequency-Band Fault Detection

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Solution Overview

Problem

Existing transformer arrangements in DC voltage systems face challenges in detecting faults, which can disrupt arc recognition and power line communication, especially when the primary or secondary winding is defective or when noise frequencies are not accurately distinguished.

Innovation Solution

A method involving a fault detection unit that determines signal components at specific frequencies from the secondary signal, comparing their levels with thresholds to identify faults, utilizing noise frequencies as indicators of fault-free conditions, and averaging signal levels across a frequency band to ignore interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If signal level thresholds are used to detect faults, then fault detection capability is improved, but false detection due to interference and noise increases

Engineering Contradiction:

Improvefault detection capabilityVSAvoidsignal level measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The frequency spectrum is segmented into multiple frequency bands, and signal levels are evaluated separately for each band. This allows the system to identify which frequency ranges contain interference and which contain valid fault information, preventing false fault detections caused by narrowband interference while maintaining sensitivity to actual faults.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The evaluation method changes from using a single fixed signal level threshold to using dynamic thresholds adapted to each frequency band. By analyzing the signal level distribution across different frequency bands and adapting thresholds accordingly, the system maintains accurate fault detection even in the presence of varying interference levels.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If a single signal level threshold is used for fault detection, then the detection method is simple, but interference in specific frequency ranges causes false fault indications

Engineering Contradiction:

Improvedetection method complexityVSAvoidfault detection reliability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The single threshold approach is segmented into multiple frequency-band-specific thresholds. Each frequency band has its own threshold determined by analyzing the signal level distribution in that band, allowing the system to accommodate varying interference conditions across different frequencies while maintaining overall system reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying a single threshold to all frequencies, the method applies partial evaluation to each frequency band separately. This excessive action of evaluating each band individually ensures that no single interference-prone frequency can cause false fault indications, while the overall process remains systematically simple.

Inventive Principle:

Principle #16Partial or excessive action

3Measurement precision

If noise frequencies are used as indicators of fault-free conditions, then the accuracy of fault detection is improved, but the complexity of distinguishing noise from fault signals increases

Engineering Contradiction:

Improvefault detection accuracyVSAvoidsignal analysis complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system performs preliminary analysis of the signal level distribution across frequency bands before making fault detection decisions. By pre-identifying which frequency bands contain noise and which contain potential fault signals, the system establishes a baseline for normal operation that simplifies subsequent fault detection while maintaining high accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The frequency band analysis acts as an intermediary between the raw secondary signal and the final fault detection decision. This intermediate evaluation step filters out noise frequencies and identifies meaningful signal components, reducing the complexity of the overall detection process while improving accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Effectively detects faults in transformer arrangements, ensuring reliable arc recognition and power line communication by distinguishing between noise and fault-induced signal level changes, thereby preventing misinterpretation of interference as faults.

Implementation Method 1

a transformer (4) that transforms a primary signal (i1) of a DC voltage line into a secondary signal

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11831149B2AFCI self test

Publication Date: 2023.11.28 FRONIUS INT GMBH

AI summary

To recognize a fault in an arrangement including a transformer having a primary winding connected in series with a DC voltage line and a secondary winding coupled magnetically to the primary winding, and including an evaluation unit that processes a secondary signal on the secondary winding, a signal component at at least one frequency is determined from the secondary signal and a signal level of the signal component is compared with a signal threshold. The fault is detected when the signal level falls below the signal threshold.