Yunus Biçen

Lifetime estimation and monitoring of power transformer considering annual load factors

This paper focuses on the realistic remaining service life prediction and monitoring system of power transformers, using an algorithm developed by the authors. The power transformer is one of the vital components of power transmission and distribution substations. It is important to know the loading capacity and remaining service life of a power transformer to ensure its economical and secure operation. This information is directly related to the condition of cellulosic insulation. According to classical method of prediction, the power transformer is considered to be operated under constant load for the remainder of its lifespan. However, in reality the load factor varies continuously, and this is a key factor affecting the service life of power transformers. In this study, a realistic method for monitoring and predicting the service lifetime of power transformers is presented by considering annual load factors. The proposed method is applicable to any power transformer and can be updated by considering relevant standards for different liquid and solid insulation materials. As a case study, life-loss calculation and the remaining service life predictions are carried out using a thermal model that has been created considering a 250 MVA mineral oil-immersed power transformer.

An assessment on aging model of IEEE/IEC standards for natural and mineral oil-immersed transformer

This paper presents an assessment on aging model of IEEE and IEC standards using thermal model of oil-immersed power transformer for natural ester and mineral oil. For this purpose, a model created for the analysis of behavior transient thermal performance with aging both of natural ester and mineral oils. Thermal model of the transformer is based on thermal-electrical analogy that is calculated separately for natural and mineral oils covering top-oil and hot-spot temperatures. The hot-spot temperature values of each ester/oil are used to calculate aging parameters which include the aging acceleration factor, time dependent relative aging rate and insulation life loss variations.

Thermal modelling and analysis of high-voltage insulated power cables under transient loads

This article presents a simple thermal model for transient analysis of high‐voltage underground power cables based on proper ladder diagram at MATLAB–Simulink software under various operating conditions for engineering students. Available commercial programs created with commercial worries are not suitable for students during the learning process, which involve different applications on power cable analysis. The model gives an opportunity for students to solve the often‐faced transient problems in utilities. The transient model of the underground power cable system using the analytic procedures based on IEC60853 standards is presented with an example solution of the 154 kV power cable in service in Turkish transmission system in this article.

A Novel Gui Simulation Program Designed for Teaching of Underground Power Cables

This paper presents a novel computer simulation program designed to aid teaching process in course of underground power cables for engineering students. The calculation of power cable ratings uses several different formulas and long analytical processes based on IEC 60287 and IEC 60853 standards. Therefore it is difficult to examine different variations such as power cable properties, installations and operation conditions, during the restrictive lesson time. For these reasons, a program has been developed to use for teaching process of the power cable course. The program allows the users to effectively learn the rating of underground power cables under different operation conditions with illustrative figures. The program details are presented and explained in this paper.

Monitoring of critical substation equipment

This paper presents lifetime monitoring algorithm available for critical substation equipment. In the remaining life calculation stage, two proposed methods named the weighted moving average - based monitoring and the trend adjusted (double) exponential smoothing - based monitoring introduced, respectively. Both methods are evaluated for various cases and the validity of the first methods tested on the prototype transformer, experimentally. However, the second newly method has advantages such as wide forecast range, trend determination capability and insensitive to short term fluctuations. These methods with the algorithms are applicable for the instrument or its parts that aging characteristics can be expressed by the empirical equations under certain stress/stresses.

Intelligent condition monitoring platform combined with multi-agent approach for complex systems

Condition monitoring and data analysis are key factors to avoid unexpected catastrophic breakdowns and detect incipient failures. Managing of these processes are not easy in complex system which has many inputs/outputs and interdependent relationships. In conventional methods, the condition monitoring is carried out separately and systematically due to the large number of monitoring point. This paper presents an intelligent condition monitoring platform (ICMP). This platform uses multi-agent system (MAS) advantages via mathematical process named failure sensitive matrix (FSM). Through this platform, the whole system is dynamically monitored, despite all the complexity. Cause and effect relations of a fault are evaluated more comprehensively and the success of achieving global results is higher. The growth of monitoring equipment or system is not a problem, because matrix structure is expandable as wanted and its performance is fast due to the nature of the parallel computation. Other important advantage of this platform is that it is an interface which works with expert systems and artificial intelligence techniques with no restrictions.