Sampled value transmission is the principal component of communication between the process level and the bay level in the IEC 61850 substation. The simulation framework of IEC 61850 substation communication in the electric power and communication synchronizing simulator（EPOCHS） is proposed， and an IEC 61850 communication model for the specific substation is developed. The virtual local area network（VLAN） mechanism defined in IEEE 802.1Q is programmed in NS2， and VLAN multicast message simulation is implemented. Comparisons of sampled value transmission between the switched Ethernet and shared Ethernet， and single-input protection and multi-input protection are made. Simulation results show that the 100 Mbit/s switched Ethernet completely meets the requirement on standards， while 100 Mbit/s shared Ethernet doesn't. Sampled value message delay and jitter are so serious that measurement wave distortion occurred in the protection in the frequency-domain， or even mal-operation of protection. There is a bottleneck problem in the protection communication link which receives multiple merging units' sampled value message， and the relevant solution for multiple communication plug-in boards is proposed.