GE T1000, Техническое руководство

Страница: 83 / 302

GE Reason Switches Chapter 4
– Functions
REASON SWITCHES-TM-EN-3 83
9.3 LAN in Modern Power System Communication
Virtual LAN technology allows separation of traffic in through logical and physical
networks. In power system communication, where is expected IEC-61850 messages
with different priority and usage, there will be only one physical path for each IED
and the packets must be separated logically.
Traffic segregation is particularly important in modern power system communication
as it is expected that multicast traffic will flow in the network. GOOSE, Sampled
Values and Precision Time Protocol messages are multicast messages, and all of
them can be mapped directly at Ethernet frame, in other words, they are layer 2
protocol communication. As these messages traffic mechanism is multicast, by
default the switch will flow them throughout its interfaces, except the incoming
messages. When using VLAN traffic segregation, multicast messages are forwarded
only onto the VLAN that the multicast message belongs to. Thus, GOOSE, Sampled
Values and PTP traffic will flow separately from each other. Finally, as the traffic is
separated, IED equipment that expects to receive only GOOSE messages will not
have its network interface interrupted by Sampled Values data, for example.
An example of expected VLAN traffic segregation is shown below. Note that a ring
physical topology is used only for example propose, as it is a common physical
network topology in power system communication. Before refer to the figure, there
are a few assumptions:

Merging Unit is the GOOSE and Sampled Values messages supply, and it is
an slave clock of PTP synchronization protocol;

PTP grandmaster clock synchronizes PTP-aware equipment, and do not
receive GOOSE or Sampled Values data;

IEDs do not synchronize themselves through PTP protocol. Both of them
expect to receive GOOSE messages from the Merging Unit and only one of
them expects to receive Sampled Values;

There are 3 VLAN configured at the equipment involved: One for PTP traffic,
other for Sampled Values traffic and another one for GOOSE messages
traffic.