Calibration formula for the capacity Pn of test transformer capacity: Pn=KVn2 omega Ct x 10-9
In formula: Pn-- nominal test transformer capacity (kVA)
Vn-- the effective value of the rated output voltage of test transformer (kV)
K-- safety factor.
K= 2, when the nominal voltage is greater than 1MV, K= 2, when the nominal voltage is lower, the K value should be higher.
Ct--- the electrical capacity of the tested product (PF)
Omega -- the angular frequency, omega equals 2 PI f, f-- the frequency of the test power
The capacitance Ct of the tested equipment can be measured by ac bridge. Ct changes are large and can be determined by the type of device. Typical data is as follows:
Simple bridge or suspension insulator dozens of micromethods
Simple grading casing 100-1000PF
Voltage transformer 200-500PF