(1) Insulation resistance, absorption ratio, polarization index, dielectric loss factor, DC resistance and leakage of winding and bushing.
(2) Measurement of insulation resistance of fasteners insulated from iron core and outgoing bushing of iron core grounding wire to shell. (3) Inspection of transformer voltage ratio (all taps), three-phase connection group and polarity of single-phase transformer outgoing line.
(4) External power frequency AC withstand voltage test of transformer.
(5) Main screen insulation resistance, capacitance value, dielectric loss factor, end screen insulation resistance and dielectric loss factor of non pure porcelain bushing.
(6) Induction withstand voltage test of winding and bushing with partial discharge measurement test.
(7) Insulating oil test (including casing insulating oil test if necessary), including interfacial tension, acid value, water-soluble acid (pH value), mechanical impurities, flash point, electrical strength of insulating oil, oil dielectric loss factor (90 ℃), micro water content in insulating oil, gas content in insulating oil (330kV and above), and chromatographic analysis.
(8) Bushing current transformer test, including insulation resistance, DC resistance, current ratio, polarity and volt ampere characteristics.
(9) Inspection and test of on load tap changer, including electrical strength of insulating oil, micro water content in insulating oil, action sequence or number of action cycles), switching test and sealing test.
(10) Winding deformation test, impulse closing test under rated voltage and noise measurement.