Self-Healing Ethernet Ring; Ethernet Redundancy - ABB RELION REX640 Technical Manual

Section 3
Basic functions
3.2.1
3.2.2
82

Self-healing Ethernet ring

The protection relay supports a self-healing ring solution for small installations. For
the correct operation of self-healing ring topology, the network topology must be a
ring. It is essential that the external switches in the network support the RSTP protocol
and that it is enabled in the switches. Otherwise, connecting the ring topology can
cause problems to the network.
The protection relay itself does not support link-down detection or RSTP. The ring
recovery process is based on the aging of the MAC addresses and the link-up/link-
down events can cause temporary breaks in communication. For a better performance
of the self-healing ring, it is recommended that the external switch furthest from the
protection relay loop is assigned as the root switch (bridge priority = 0) and the bridge
priority increases towards the protection relay ring. The end links of the protection
relay loop can be attached to the same external switch or to two adjacent external
switches.
A self-healing Ethernet ring requires a communication module with at least two
Ethernet interfaces for all protection relays.
The self-healing ring solution supports the connection of up to 30
protection relays. If more than 30 protection relays should be
connected in the same system or if SMV is used, it is recommended to
use the HSR or PRP protocols for Ethernet redundancy to ensure
proper functionality.

Ethernet redundancy

IEC 61850 specifies a network redundancy scheme that improves the system
availability for substation communication. It is based on two complementary
protocols defined in the IEC 62439-3:2012 standard: parallel redundancy protocol
PRP and high-availability seamless redundancy HSR protocol. Both protocols rely on
the duplication of all transmitted information via two Ethernet ports for one logical
network connection. Therefore, both are able to overcome the failure of a link or
switch with a zero-switchover time, thus fulfilling the most demanding real-time
application requirements for the substation automation.
Ethernet network redundancy can be achieved using HSR or PRP, or with a self-
healing ring using RSTP in the managed switches. Ethernet redundancy is applied to
all services using the Ethernet/TCP network.
PRP specifies that each device is connected in parallel to two local area networks.
HSR applies the PRP principle to rings and to the rings of rings to achieve cost-
effective redundancy. Thus, each device incorporates a switch element that forwards
frames from port to port.
1MRS759142 C
REX640
Technical Manual