Transformer Oil Paper Insulation Polarization Parameter Estimation
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Solution Overview
Problem
Current methods for diagnosing the aging state of oil paper insulation in transformers are inefficient due to long measurement times and dependence on uniform moisture distribution, which affects accuracy and is not suitable for large power transformers.
Innovation Solution
An improved mathematical model that estimates polarization parameters using single-cycle recovery voltage data, incorporating peak voltage, peak time, and initial slope, transformed into an optimization problem solved by a particle swarm algorithm, reducing measurement time and applicable to both large and distribution transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the dominant time constant is determined by charging time and temperature as variables, then the measurement can capture dielectric response characteristics, but it takes a long measurement time due to the large charging time interval
Solution Approach 1:
The patent transforms the parameter determination from direct measurement using large charging time intervals to calculation based on multiple characteristic quantities (peak time, maximum value, initial slope) obtained from smaller time interval measurements. This changes the measurement parameters to achieve both precision and speed
Solution Approach 2:
The patent performs preliminary measurements of multiple characteristic quantities (peak time, maximum recovery voltage, initial slope) during the measurement phase, then uses these pre-obtained data to calculate the dominant time constant through optimization, avoiding the need for lengthy direct measurement
2Measurement precision
If traditional Karl Fischer titration is used to determine trace moisture, then moisture content can be measured, but the test accuracy is greatly affected by temperature and requires uniform moisture distribution
Solution Approach 1:
The patent replaces the chemical Karl Fischer titration method with an electrical measurement method using recovery voltage characteristics. This substitution eliminates the need for uniform moisture distribution and reduces temperature sensitivity, as the dielectric response reflects overall insulation state rather than requiring homogeneous sampling
3Reliability
If the extended Debye equivalent circuit is used to explain relaxation characteristics, then the polarization parameters can be modeled, but a suitable mathematical model is needed to estimate the parameters efficiently
Solution Approach 1:
The patent uses an optimization algorithm that iteratively adjusts the dominant time constant value to minimize the difference between calculated and measured recovery voltage. This feedback mechanism efficiently determines the equivalent circuit parameters without requiring complex manual calculations or oversimplified models
Solution Approach 2:
The patent transforms the parameter estimation problem into an optimization problem by expressing the dominant time constant as a function of measurable characteristics (peak time, maximum value, initial slope). This changes the approach from direct complex parameter identification to optimized calculation based on fundamental relationships
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 method significantly reduces sampling data requirements, shortens measurement time, and provides consistent recovery voltage curves for accurate insulation state diagnosis in transformers.
Implementation Method 1
the extended Debye equivalent circuit can be used to explain the relaxation characteristics of the oil paper insulation
Implementation Method 2
establishing an equivalent circuit with polarization capacitance resistance and insulation capacitance resistance as unknown parameters
Data Source
AI summary
The present application relates to the technology field of assessment of aging state of oil paper insulation of the large power transformer and quantitative diagnostic, specifically estimating parameters of the circuit through the initial slope of the recovery voltage. It includes an improved mathematical model for solving parameters of the dielectric response equivalent circuit by using the peak of the recovery voltage, the peak time and the initial slope characteristics; transforming the identification of parameters of the equivalent circuit into a mathematical optimization problem, and then solving the mathematical optimization problem using a particle swarm algorithm. The design of the present application can significantly reduce the sampling data of the recovery voltage, and the measured data in the field and the calculated data of different capacity RVM experiments on real transformers have good consistency, which is conducive to the diagnosis of state of oil paper insulation of the transformer.