Research And Development Of Online Condition Monitoring System And Evaluation For Power Transformer

Abstract:Power transformer is a vital equipment in the power transmission system and is also a important device in modern power supply system, moisture content and capacitive equipment insulation status is a reflection and an important indicator to power transformer, an important basis to monitoring the transformer for power supply company. This paper describes the development of the transformer line monitoring of moisture content and capacitive equipment insulation status online monitoring techniques and methods for the assessment of the transformer were studied. The main work is as follows:(1) The mechanism of moisture and its hazards are introduced; based on the relationship between moisture content in oil and the dielectric constant of the polyimide film,derived of the relations about moisture content,relative humidity and temperature design an online monitoring method which based on relative humidityand realize the online monitoring system of moisture content combined with temperature and humidity sensor MMT162.The experimental results show that the drift of moisture content is±1ppm and±0.2℃for temperature within half an hour.(2) Researched and developed a capacitive device online monitoring system. Studied the relationship between insulating properties of capacitive device and its dielectric loss, by measuring the dielectric loss factor and other electrical parameters of the device will be able to monitoring capacitive insulating state. Use high precision zero flux through current sensors which fit the industrial environments to achieve the goal of measuring the end of the screen small current accurately, then use discrete Fourier transform to calculate the dielectric loss factor devices to achieve a capacitive device online monitoring system. Using this method with the bridge method parameters were measured on the insulation sleeve comparative experiments, Test result shows that the monitoring system is with high accuracy and good stability. (3) Proposed a set of transformer condition assessment program. The program consists of two parts:First, the state of health of the transformer index calculation, the other part is used for life and the failure probability estimate. The health index is defined as a transformer operating parameters, on-site visual inspection and laboratory test results unified and integrated offline quantitative indicators to assess the state of the transformer; introduction of EA’s computing system, by setting the aging aging formula factor to achieve the estimated remaining life; probability of failure by setting the coefficients of the equation and curvature, to achieve the estimated probability of failure. The use of test data collected at the scene, the use of the program for the state of the transformer were evaluated to verify the assessment program has some practical value.(4) Developed a transformer condition monitoring system software, the ability to characterize the state of online transformer parameters, such as oil dissolved gas, moisture content and capacitive insulating parameters for online collection and centralized management. System using C/S and B/S hybrid architecture. Moisture content monitoring transformer operating conditions resulting oil and capacitive data, maintenance personnel management and maintenance of transformer substation site provides a reference.