P.3.271
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Communication and Timing
It is recommended that you set the 87TFB setting identically at all
nonpermanent outstation relays of a given application.
Ethernet Interface
Ports 5A and 5B on the optional E4 Ethernet card may be configured for 87L
communications. The relay supports the physical layers shown in Table 3.142.
Note that the E4 card comes standard with two ports.
Table 3.141 Time Fallback Modes
87TFB Description Usage
1 If any of the required time sources is unavailable, the 87L
function is effectively inhibited at all relays of the differen-
tial system.
This mode is biased towards security and away from avail-
ability. For instance, choose 87TFB = 1 in a 2SS applica-
tion with duplicate protection schemes where channel
asymmetry is expected. If a time source is lost on the A
protection, it is inhibited and the circuit remains protected
on the B protection.
2 If a local and/or remote time source for a given channel is
unavailable, the affected channel is forced out. The relay
responds by switching to a hot stand-by channel, switching
to the outstation mode, or the 87L function is entirely lost,
depending on the application and the status of the other
channels.
This mode is biased towards security and away from avail-
ability. It is applicable to schemes which have channel
redundancy (2SD or 3SM). For instance, choose
87TFB = 2 in a 3SM application where one of the channels
is routed through a MUX on which asymmetry is expected
and the other two channels are direct fiber. If a time source
is lost, the multiplexed channel is forced out and the two
relays that share this channel become slaves.
3 If a local and/or remote time source for a given channel is
unavailable, and the channel was symmetrical (less than
3 ms of asymmetry) prior to the loss of time, the affected
channel is forced into the channel-based synchronization
mode. The 87L settings are switched into the high security
mode, and the relay continues to use the channel. If the swi-
tchover to the channel-based synchronization was not possi-
ble, the channel is forced out with consequences as in the
fallback Mode 2.
This mode is biased towards availability and away from
security. Choose 87TFB = 3 in an application where asym-
metry may occur but can be dealt with by switching to
extended security settings.
4 If a local and/or remote time source for a given channel is
unavailable, and the channel was symmetrical (less than
3 ms of asymmetry) prior to the loss of time, the affected
channel is forced into the channel-based synchronization
mode. The 87L settings are switched into the high security
mode, and the relay continues to use the channel. This state
continues until the channel is switched. Channel switching
is detected via the step change in the round trip channel
delay or temporary loss of channel. If channel switching is
detected during the channel-based synchronization mode, or
the switchover to the channel-based synchronization was
not possible, the channel is forced out with consequences as
in the fallback Mode 2.
This mode is biased towards availability but is more secure
than Mode 3. For instance, choose 87TFB = 4 in an appli-
cation where asymmetry may be excessive if it occurs.
Table 3.142 Ethernet Interface Options
Physical Layer Medium Connector
10/100BASE-T Cat 5 cable (category 5 twisted-pair) RJ45
100BASE-FX Multimode fiber-optic cable LC
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