Area 1: Transformer winding dislocation
Main objective of projects below is to build clear correlation between terminal response changes to extent of dislocation and develop at least one on-line technique without requiring a shutdown of the transformer.
Project 1: Develop quantitative correlation between response at the terminal of winding to SFR excitation to the extent of dislocation and validate on a HV winding.
Part 1- Modeling of actual transformer winding of FRA- Compute the RLC elements of the high frequency equivalent circuit of the winding in the lab.
Part 2- Validate it by comparing the results of SFRA on the winding with Simulink /Spice simulation of the derived equivalent circuit.
Part 3- After the capacitance between a few discs, recalculate the response by simulation, validate on the model experimentally and aimed at arriving at the extent of changes such as shift in poles in relation to change in capacitance between disc in turn with the shifting of discs. Caution: Initially do only one disc movement and later investigate multiple defects.
Project 2: Develop quantitative correlation between frequency responses at the terminal of winding to LVI excitation to the extent of dislocation and validate on a HV winding.
Part 1– Same as in project 1
Part 2 &3– Same as in project 1 except that instead of swept frequency excite with impulses. Choose an impulse wave front and tail time that is most sensitive to disc movements.(Do not stay with only the conventional 1.2/50 microsec(us) wave. Pulse such as 0.2/10 us may be better depending on the natural frequencies of the windings)
Project 3: Develop quantitative correlation between reflections at the terminal of winding to LVI by travelling wave method to the extent of damage and validate on a HV winding.
Part 1– Same as in project 1
Part 2 &3– Same as in project 2 except that instead of looking for changes in frequency response apply travelling wave principle. Assuming that normal winding is uniform right through, its surge impedance will be same right through, and any impulse applied at one end will suffer reflection only at terminals. In case of winding movements, the surge impedance will not be the same through the length of the winding. Impulse input at one end will undergo several reflections. Some measure should give an indication of the extent of deformation. Suggest initial work by simulation in MATLAB/EMTP/SPICE. Take up experimentation after .extensive simulations. Location of fault can also can be attempted using wavelet.
Area 2: Ageing of paper insulation
De-polymerisation paper of paper takes place predominantly due to oxidation and hydrolysis. Diagnosis involves detection of the agents of ageing (moisture, acids, temperature) and degree of ageing (DP, furan content). Moisture estimation is typically done by frequency domain spectroscopy and suffers from inadequacies distribution of moisture in paper, its correlation with paper condition is empirical highly dependent on physical configuration winding insulation. Moisture and acids at the place of high temperature is unknown, furan content in oil is again an empirical estimation of the lowest DP in paper. FDS method s require shutdown and take several hours. Main objective of the following projects is to improve correlation (less structure dependent), introduce online methods, reduce test time, and locate the weak spots in the paper insulation.
Project 1: Estimation of moisture distribution in winding insulation using PDC method.
Part 1 :Development of equivalent circuit of the winding insulation. Paper , pressboard, oil to be each represented by RC elements for all types of polarization. RC values for various moisture contents to be taken from literature.
Part 2:Determine its PDC by simulation and correlate paper moisture content with the characteristics.
Project 2: Estimation of moisture distribution using FDS method.
Part 1:same as above.
Part2 :Determine C –Tan delta by simulation over the frequency range of 1 mHZ to 100Hz and correlate paper moisture content with the response obtained .
Area 3: Monitoring of power transformers with HPSEB
Project 1: Development of data based software for recording transformer data (on going UG project).
Project 2 : Propose a condition based monitoring plant to HPSEB for their power transformers.
Part1 :Interact with project 1 team so that all relevant data is collected.
Part 2:Categorize the transformers into normal (no known defects), suspects (disturbing trends in for eg. DGA, oil temperature) and defective units.Part 3:Propose monitoring plan for each category (what to monitor, periodicity etc).