Redundancy Protocols; Parallel Redundancy Protocol (Prp); Prp Networks - GE MiCOM P40 Agile Technical Manual

3

REDUNDANCY PROTOCOLS

REB variants for each of the following protocols are available:
PRP (Parallel Redundancy Protocol)
●
HSR (High-availability Seamless Redundancy)
●
● RSTP (Rapid Spanning Tree Protocol)
SHP (Self-Healing Protocol)
●
DHP (Dual Homing Protocol)
●
Failover
●
PRP and HSR are open standards, so their implementation is compatible with any standard PRP or HSR device
respectively. PRP provides "bumpless" redundancy. RSTP is also an open standard, so its implementation is
compatible with any standard RSTP devices. RSTP provides redundancy, however, it is not "bumpless".
SHP and DHP are proprietary protocols intended for use with specific GE products:
SHP is compatible with the C264-SWR212 as well as H35x multimode switches.
●
● DHP is compatible with the C264-SWD212 as well as H36x multimode switches.
Both SHP and DHP provide "bumpless" redundancy.
Note:
The protocol you require must be selected at the time of ordering.
3.1

PARALLEL REDUNDANCY PROTOCOL (PRP)

Power system companies have traditionally used proprietary protocols for redundant communications. This is
because standardized protocols could not meet the requirements for real-time systems. Even a short loss of
connectivity may result in loss of functionality.
However, Parallel Redundancy Protocol (PRP) uses the IEC 62439 standard in Dual Homing Star Topology networks,
designed for IEDs from different manufacturers to operate with each other in a substation redundant-Ethernet
network. PRP provides bumpless redundancy for real-time systems and is the standard for double Star-topology
networks in substations.
3.1.1

PRP NETWORKS

Redundant networks usually rely on the network's ability to reconfigure if there is a failure. However, PRP uses two
independent networks in parallel.
PRP implements the redundancy functions in the end nodes rather than in network elements. This is one major
difference to RSTP. An end node is attached to two similar LANs of any topology which operate in parallel.
The sending node replicates each frame and transmits them over both networks. The receiving node processes the
frame that arrives first and discards the duplicate. Therefore there is no distinction between the working and
backup path. The receiving node checks that all frames arrive in sequence and that frames are correctly received
on both ports.
The PRP layer manages this replicate and discard function, and hides the two networks from the upper layers. This
scheme works without reconfiguration and switchover, so it stays available ensuring no data loss.
There should be no common point of failure between the two LANs. Therefore they are not powered by the same
source and cannot be connected directly together. They are identical in protocol at the MAC level but may differ in
performance and topology. Both LANs must be on the same subnet so all IP addresses must be unique.
Px4x-REB-TM-EN-6
Chapter 5 - Operation
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