T-circuits are used widely in extra high voltage（EHV） transmission system due to their significant economic and environmental advantages over two-terminal lines.But it is difficult to protect T-circuit using the traditional techniques.Non-communication protection based on fault transient current component is used in T-circuit

and in terms of the features of fault transient current component

transient protection criterion is calculated using Daubechies wavelet.The detailed simulation of T-circuit is carried out in different positions

different transition resistances

different fault times and different fault types

and it has proved the feasibility to use the transient protection in T-circuit.