Windowed Frequency Shift for Three-Winding Transformer Loss Measurement

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Solution Overview

Problem

Conventional methods for detecting transformer losses in actual operation conditions introduce significant errors due to ignoring real-time load effects and synchronization issues, leading to inaccurate measurements.

Innovation Solution

A live measurement method for three-winding transformer loss based on windowed frequency shift, which involves establishing an improved calculation equation, applying windowed discrete-time Fourier transforms, performing frequency shift processing, and converting signals into phasor values to accurately calculate no-load and load losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional off-line test methods are used to measure transformer loss, then the measurement process is simple, but the measurement accuracy is low due to ignoring actual load effects and grid state variations

Engineering Contradiction:

Improvetransformer loss measurement accuracyVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces conventional mechanical/off-line testing methods with an on-line measurement system that uses signal processing techniques (Fourier transform, windowing algorithms) to accurately measure transformer loss under actual operating conditions, thereby improving measurement accuracy without requiring physical disassembly or shutdown of the transformer

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces signal processing intermediaries (windowing functions, Fourier transform algorithms, frequency shift correction mechanisms) as mediators between the raw measurement signals and the final loss calculation, enabling accurate extraction of transformer loss parameters from complex on-line signals while maintaining system simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If on-line measurement of transformer loss is implemented, then the measurement reflects actual operating conditions, but spectrum leakage and picket fence effect occur due to frequency fluctuation and sampling synchronization issues

Engineering Contradiction:

Improvetransformer loss measurement accuracyVSAvoidspectrum leakage and picket fence effect

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies windowing functions (Hanning, Hamming, Blackman) as preliminary processing steps before Fourier transform to pre-condition the signals, thereby suppressing spectral leakage and picket fence effects before the main analysis is performed, which improves measurement accuracy under on-line conditions

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent dynamically adjusts measurement parameters including window function selection, frequency shift correction values, and sampling synchronization parameters based on detected grid frequency fluctuations, thereby adapting the measurement system to changing operating conditions and eliminating spectrum leakage effects

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If frequency fluctuation and asynchronous sampling are present in on-line measurement, then the measurement covers actual grid conditions, but large errors are introduced due to spectrum leakage and picket fence effect

Engineering Contradiction:

Improveadaptability to actual grid conditionsVSAvoidtransformer loss measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent implements dynamic frequency tracking and asynchronous sampling correction mechanisms that continuously adapt to changing grid frequency conditions, using real-time frequency detection and correction algorithms to maintain measurement accuracy despite frequency fluctuations and sampling asynchrony

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent employs feedback mechanisms where measured frequency deviations and sampling synchronization errors are detected and used to correct subsequent measurements through frequency shift compensation and sampling rate adjustment, thereby maintaining high measurement precision under varying grid conditions

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS11422175B2Live measurement method for three-winding transformer loss based on windowed frequency shift

Publication Date: 2022.08.23 STATE GRID JIANGSU ELECTRIC POWER CO LTD

AI summary

Provided is a live measurement method for three-winding transformer loss based on windowed frequency shift. The method includes: step 1: providing an improved live calculation equation of a three-winding transformer loss; step 2: processing a collected x(t) signal by windowed frequency shift calculation; step 3: solving an amplitude and a phase of the collected x(t) signal via discrete Fourier transform of a frequency shift signal; and step 4: calculating a no-load loss and a load loss of a three-winding transformer.