A Modified Model for Discharge Voltage of AC Transmission Line-Tower Air Gaps

The discharge characteristics of long air gaps are of great significance in the external insulation design of extra high voltage (EHV) and ultra high voltage (UHV) transmission lines. At present, the breakdown characteristics of air gaps are mainly investigated by repeated full-scale discharge tests. In order to reduce the costly experimental works, the influence of different tower structures on the air gap breakdown voltage has been fully studied, and the tower structure coefficient $T_{g}$ is proposed and calculated. Then, a modified mathematical model is developed to calculate the 50% discharge voltage of complicated bundle conductor-tower air gaps. The research results show that the 50% discharge voltages of different tower structures calculated by these models are in good agreement with the on-site test results. The maximum errors between the calculated and the test data are less than 6.3%, which prove the feasibility of the proposed model for various engineering air gaps.

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