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5 SETTINGS
•
Port 3 is in standby mode and does not actively communicate on the Ethernet network but monitors its link to the Mul-
tilink switch. If port 2 detects a problem with the link, communications is switched to Port 3. Port 3 is, in effect, acting as
a redundant or backup link to the network for port 2. Once Port 2 detects that the link between port 2 and the switch is
good, communications automatically switch back to port 2 and port 3 goes back into standby mode.
If
is set to PRP, the operation of ports 2 and 3 is as follows:
REDUNDANCY
•
Ports 2 and 3 use the port 2 MAC address, IP address, and mask
•
The configuration fields for IP address and mask on port 3 are overwritten with those from port 2. This is visible on the
front panel but not displayed in the EnerVista software.
•
Port 2
field is visible
MCST ADDRESS
•
The port 2 PTP function still uses only port 2 and the port 3 PTP function still uses only port 3. The relay still synchro-
nizes to whichever port has the best master. When ports 2 and 3 see the same master, as is typically the case for PRP
networks, the port with the better connectivity is used.
The two ports must be connected to completely independent LANS with no single point of failure, such as common
power supplies that feed switches on both LANS.
NOTE
For this setting change to take effect, restart the unit.
: This setting allows the user to change the multicast address used by the PRP supervision frames.
PRT2 PRP MCST ADDR
The setting applies to UR CPUs that support multiple ports (T, U, and V). This setting is available if the hardware has multi-
ple ports and
is set to PRP.
REDUNDANCY
e) PARALLEL REDUNDANCY PROTOCOL (PRP)
The Parallel Redundancy Protocol (PRP) defines a redundancy protocol for high availability in substation automation net-
works. It applies to networks based on Ethernet technology (ISO/IEC 8802-3) and is based on the second edition (July
2012) of the IEC 62439-3, clause 4.
PRP is designed to provide seamless recovery in case of a single failure in the network, by using a combination of LAN
duplication and frame duplication technique. Identical frames are sent on two completely independent networks that con-
nect source and destination. Under normal circumstances both frames reach the destination and one of them is sent up the
OSI stack to the destination application, while the second one is discarded. If an error occurs in one of the networks and
traffic is prevented from flowing on that path, connectivity is still provided through the other network to ensure continuous
communication. Take care when designing the two LANs, so that no single point of failure (such as a common power sup-
ply) is encountered, as such scenarios can bring down both LANs simultaneously.
Figure 5–6: EXAMPLE OF PARALLEL REDUNDANT NETWORK
PRP uses specialized nodes called doubly attached nodes (DANPs) for handling the duplicated frames. DANPs devices
have an additional module, called Link Redundancy Entity (LRE). LRE is responsible for duplicating frames and adding the
specific PRP trailer when sending the frames out on the LAN, as well as making decisions on received frames as to which
one is sent up the OSI stack to the application layer and which one is discarded. LRE is responsible for making PRP trans-
parent to the higher layers of the stack. There is a second type of specialized device used in PRP networks, called RedBox,
with the role of connecting Single Attached Nodes (SANs) to a redundant network.
UR relays implement only the DANP functionality. The RedBox functionality is not implemented.
GE Multilin
L90 Line Current Differential System
5.2 PRODUCT SETUP
5
5-25
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