The development of smart distribution grid is towards the meshed and multi-source network topology

and the traditional feeder protection and automation (FA) are finding it increasingly difficult to meet the requirements for self-healing. Current differential protection is widely applied to the protection of transmission feeders owing to its inherent strengths of high sensitivity

selectivity and speed

which relies on the provision of a relatively high-bandwidth communication channel

and the existing synchronous digital hierarchy/plesiochronous digital hierarchy (SDH/PDH) networks have proven well suited to this task

but the communication equipment has a low bandwidth and is costly for the distribution grid. This paper presents a current differential protection device for the smart distribution grid

and the sampling value (SV) can be exchanged between these devices over the Ethernet passive optical network (EPON). The device adopts the SV synchronization algorithm based on IEEE 1588 to realize current differential protection of multi-terminal distribution lines. Now the device has successfully been put into operation in some 10 kV distribution lines.