This paper presents a health analysis technique for transformer winding insulation through thermal monitoring and Fast Fourier Transform (FFT) power spectrum. A novel thermal model for the Kraft paper insulation of transformer is proposed by using the transformer's top-oil and winding hot-spot temperature models. The relationship between the temperature rise of oil inside the transformer tank and the winding insulation degradation are considered by utilizing the data-sets and daily load cycles of a 10/13 MVA, 132/11 kV, 50 Hz, ONAF grid power transformer. The model based on IEEE Guide for loading mineral-oil-immersed transformers is developed in Simulink. The hotspot temperature rise from the thermal model is used as a reference to analyze the winding insulation degradation in the form of high frequency partial discharges (PDs) upon the output parameters of the transformer. Using data analysis techniques, a correlation is presented between the load cycles and the hot-spot temperature through which the health status of the transformer winding insulation is estimated. Moreover, the high frequency transients were detected using the Fast Fourier Transform (FFT) spectrum analyzer tool in MATLAB. The preliminary study shows that high frequency PDs are detected for the overheated and deteriorated state of the winding insulation. The results show that the proposed technique is feasible for the health analysis of power transformers and successfully predicted the deterioration of the transformer winding insulation.
Grim issue of Electricity shortages in most of developing countries leads to explore the potential in renewable and economical sources of energy. Power generation through Waste To Energy (WTE) Plants is an effective way to deal with the problems of MSW management and electricity shortages in densely populated cities of the world. In this paper, capacity estimation of Power generation from Municipal Solid Waste (MSW) of Peshawar city through Solid Waste Fueled Power Plant (SWFPP) is analyzed. For effective estimation of power generation through WTE plant, a detail study about estimation of Municipal Solid Waste of Peshawar city, composition and characteristics of collected waste, appropriate conversion technology; heat generated from it and ultimate power generation is discussed.
In transformers, in addition to the primary and secondary coils, there are several other important components and accessories in which the insulating material is one of the most critical components of a transformer. Sufficient insulation between different active parts are necessary for safe operation. Adequate insulation, it is not only necessary to insulate the coils from each other, or from the core and tank, but also guarantees the safety of the transformer against accidental surges, but with the growth in size and complexity of power stations, transformer is facing insulation problems. The evaluation of the transformer overload capacities certainly leads to complex variables that affect the operating life of the power and distribution transformer. In this study, the long-life calculation is performed on the basis of two experiments, which are related to the insulation degradation of the mineral oil and cellulose paper such as by adding different types of nano-particles to the mineral oil to enhance the strength of oil, and by changing the loads under different operating conditions to control the deteriorating rate of the insulation to prevent the life of the transformer. The insulation breakdown strength is improved from 37 kV to 71 kV by mixing the semiconductor nanoparticles such as gadolinium-doped ceria (GDC) and cerium dioxide (CeO2) with mineral oil. Moreover, for cellulose paper, thermal degradation rate is kept below its limit by reducing the temperature when controlling the load.
The prediction and determination of thermal response for the metallic parts is a very crucial step in the design of power transformers. This paper presents a comparative analysis of different thermal models for predicting the hotspot temperature and top oil temperature of power transformers. Also, a new thermal model is proposed for the monitoring of transformer operation which is capable of identifying the hotspot temperature and the top oil temperature by taking into account the ambient temperature and the load variation with respect to real time. The model is experimentally validated and compared with the actual field data. It is found that results obtained from the proposed model and the actual field data are in good agreement.
Due to the fast increase in energy of modern human being the desire for the clean renewable energy is increasing day by day. Electrical power generation from wind is promising source. But due to the large combination of wind forms in electrical power grid the stability and security are key issues for the electrical power engineers. Amongst the required grid codes for the power utilities LVRT is very important. According to LVRT the wind form should act as conventional power plant and connect to grid for some particular time to provide stability to grid at normal and fault time. In this paper we have developed a LVRT strategy for control of active, reactive power and DC link voltage of the variable speed wind turbine. The test bed system is 9 MW DFIG wind turbine attached to 120KV grid system by 30KM long 25 KV transmission line. The modelling and simulation is done by using MATLAB/SIMULINK. The control system is implemented by using PI controller using vector or field oriented control. The LVRT strategies implemented on test bed model are (STFCL), DC chopper, Rotor Crowbar and Hybrid strategy with using RSC control, GSC control and pitch control mechanisms. The hybrid strategy provides excellent solution for LVRT of DFIG wind turbine by controlling power (active and reactive) and voltage of DC link. The results of hybrid strategy during symmetrical fault is best and well suited to the LVRT requirements as compared of STFCL, DC chopper and crowbar.
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