Drying method of power transformer winding solid insulation and apparatus for making the same

摘要

The invented method of drying power transformer winding solid insulation makes it possible to dry the winding by a low-frequency current of sinusoidal characteristic at continuously set frequency and adjustable current and voltage to a constant value in such a manner that the winding of higher voltage is fed with a low-frequency current while the winding of lower voltage is short-circuited. This arrangement eliminates a risk of occurrence of excessive voltage peaks in both the short-circuited winding and an optional third disconnected winding. A low-frequency source, a low-frequency converter (20) takes sinusoidal current from mains with power factor being equal to one and generates at the output a current and voltage of sinusoidal characteristic of arbitrary and continuously adjustable frequency. Both the output current and voltage can be set to a constant value. The low-frequency converter (20) makes it possible to measure the transformer winding resistance directly, without any additional devices. A control and recording system (60) controls automatically and regulates the entire drying process based on measured, calculated and given characteristic variables and values of the transformer. In the end of the measurement, it performs a conclusive record for a client. Besides that, it records all the drying process including interventions of the operator and in the end, it provides a record about history of the whole process.