IEC 61850 has become the reference standard for Substation Automation Systems (SAS) in smart power grids. Current IEC 61850 compliant SAS use Ethernet technology for both Event-Triggered (ET) and Time-Triggered (TT) traffic to transport highly critical messages requiring low-latency guarantees. However the real-time guarantee is often achieved by over-provisioning network resources. In this paper we study the potentials of using Time-Sensitive Networking (TSN) in SAS. TSN adds real-time enhancement to the existing IEEE 802.1Q standard by providing several new traffic shapers. If TT traffic can be guaranteed by scheduling its transmission at the right time using TSN time-aware shaper, it is not the case for ET traffic. The paper contribution is twofold: proposing a first mapping of the IEC 61850 protocols to the TSN traffic classes, based on the analysis of both TSN and IEC 61850 protocols; and developing an exact worst-case delay (WCD) analysis for ET traffic. The tightness of the developed WCD analysis has be shown by simulations.