Due to the randomness of renewable energy

power flow becomes complex and variable. In addition

a large amount of renewable energy has to be remotely transferred and consumed. Therefore

transmission congestion becomes increasingly serious. Dynamic line rating (DTR) technology can improve the transmission capacity of existing overhead lines and fully utilize the flexibility of power system. Especially under N‒1 contingency

applying DTR technology can alleviate severe transmission congestion. However

it is still challenging to optimize DTR with security assurance

which suffers from dimension curse in traditional approaches under N‒1 contingency. In this paper

a two-stage distributionally robust optimization (DRO) approach is proposed to improve the transmission capacity of overhead lines. A transient temperature calculation model of overhead lines is firstly proposed and simplified to preserve the convexity property in the following DRO model. Then

a two-stage DRO model for source-grid-storage system considering DTR of overhead lines and N‒1 security criterion is established to avoid the blackout under N‒1 contingency. A linearized alternative current power flow model considering reactive power and network losses is utilized to calculate the line current more accurately. Finally

case studies on IEEE-24 bus system and IEEE-118 bus system verify the effectiveness of the proposed method.