Dr. Farhan Mehmood

Liquid dielectrics are basically used to prevent or rapidly quench the electric discharges. They are used widely to provide insulation in transformers, capacitors, high voltage cables and switch gears. It is essential to design a device which can measure the breakdown voltage strength of these liquid dielectrics, in order to understand the reliability of equipment functionality on dielectrics used in them. The predetermined estimation of dielectric strength can help us to prevent our appliances from fatal failure, provided that they are operated in optimized range of voltages that is below the breakdown voltage of dielectrics used in them. The transformer oil (insulation oil) of voltage and current transformers fulfills the purpose of insulating as well as cooling. Thus, the dielectric quality of transformer oil is essential to secure operation of a transformer. As transformer oil deteriorates through aging and moisture ingress, transformer oil should, depending on economics, transformer duty and other factors, be tested periodically. Power utility companies have a vested interest in periodic oil testing since transformers represent a large proportion of their total assets. Through such testing, life of transformer can be substantially increased, thus reducing new investment of replacement transformer assets. Measuring the breakdown voltage of liquid dielectrics will give information about their dielectric strength. Through this test-kit, we will be able to study breakdown voltage characteristics of liquid dielectrics as well as newly developed nanodielectrics. Transformer designing is the major and toughest part of our project. We have designed a high voltage single phase transformer with input from WAPDA utility of 230V and the output will be variable with the range of 0V to 30kV (RMS). We rectify the AC input with a rectifier. This DC voltage is then inverted to a square wave with an inverter. This square wave is then converted to a sinusoid through an RLC filter. The transformer then steps up this voltage. The magnitude of the output voltage is controlled automatically through MATLAB and voltage rise rate is set to 2kV/ sec which can also be changed according to the requirement. As soon as, the breakdown of oil sample occurs as the high voltage, the protection circuit cuts the supply so that the source is not damaged by the short circuit current. The values of breakdown voltage, applied voltage and rate of rise of voltage can be monitored as well.

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