Study of Inception Mechanism of Electrical Trees from Bow tie Trees
The relationship between bow tie tree length and breakdown strength of XLPE cables was obtained both experimentally and by calculation. Assuming the models where both permittivity and resistivity of BTTs vary near the BTT tip, it was verified that electrical trees may be initiated from inside the BTT, quantitatively. In cases where the length of the BTT is short, the equivalent phenomenon as if er= 80 occurs because the resistivity of the BTT may decrease non linearly under high electric fields. Using these results, the influences of BTTs on EHV cables in service were estimated.
IEEJ Transactions on Fundamentals and Materials