Wet tests on naturally polluted glass and composite insulators
The study examines what type of bird excrement contamination will lead to insulator's flashovers on the Estonian 110 kV overhead power lines. Wet tests made in laboratory with naturally contaminated glass and composite insulators show that traditional (insulator's surface) contamination will not lead to flashovers and therefore most likely the flashovers are caused by highly conductive bird excrement streamers. The tests also show that using corona rings at composite insulator's line end fittings, affects the occurring probability of partial discharge extent on wetted insulator.
Effect of arc current on properties of composite insulators for overhead lines
Results of power are tests carried out on composite insulators for 110 kV overhead lines are analyzed. The effect of arcing on the basic electrical and mechanical parameters of the tested insulators is examined. Results of pre- and post-arc electric strength tests as well as those of thermomechanical and mechanical tests carried out on insulators subjected to the power arc test are presented.
Analysis on Operation Faults of Transmission Line and Countermeasures
As the terminal line,HV transmission line plays a crucial role in the electric power system.At first,the paper records the trip rate and operation faults of HV transmission line in the recent years.According to the recording results,it summarizes several reasons of electrical faults and tripping,the reasons are: lightning stroke,wind deviation discharge,external force damage,bird disaster,covered ice and waving,pollution flashover,uncertain reasons and so on.It also summarizes the main characteristics and regulation of faults and tripping,and analyzes the main factors of the fault from two aspects: external cause(circumstance) and internal cause(transmission line),and takes some effective protection measures in relation to the two aspects.The main countermeasures are: reducing pole tower grounding resistance,regulating discharge clearance before rainy season,decreasing protective angle,installing counter-bird devices,using composite insulators and anti-pollution insulators and so on.At last,it also brings out the new research subjects about UHV transmission line operation and maintenance based on present state of UHV development.It provides a reference for reducing and protecting operation faults of transmission line.