With the rapid growth of the business data volume of smart grids

the requirements for low-latency and highreliability in control information transmission keep continuously increasing.The time-aware shaper(TAS)mechanism is one of the key technologies in time-sensitive networking(TSN)standard. However

the traditional TAS mechanisms can not fully utilize the communication bandwidth resources

which makes it difficult to simultaneously meet the diverse latency requirements of various traffic flows within substations.To address this issue

this paper proposes the idea of dynamic and finegrained protection time window division.We first propose a traffic mapping scheme based on the integration of International Electrotechnical Commission(IEC)61850 communication and TSN technology.Then

a utility analysis model for time window division is designed. Finally

a utility-based dynamic time window division algorithm is proposed to obtain the maximum benefits overall.The simulation results show that

by optimizing the time window division strategy of the TAS mechanism

the proposed algorithm significantly reduces overall network transmission latency under various scenarios. In particular

the transmission delay of critical generic object-oriented substation event(GOOSE)1A traffic is kept within 3 ms

while ensuring that the packet loss rate of sampled measured value(SMV)traffic does not exceed 3%.