18.38
SEL-400 Series Relays Instruction Manual Date Code 20171006
Synchrophasors
Control Capabilities
When received, synchrophasor messages contain digital data. These data are
stored in the Remote Synchrophasor Relay Word bits in Figure 18.25.
Set MRTCDLY for the maximum expected communications channel delay in
milliseconds. Any data arriving later than this time are rejected. The RTCDLYp
Relay Word bit indicates this condition. Use the MRTCDLY to constrain the
maximum longest operating time of the system. Set the RTCRATE to the rate of
synchrophasor data being sent by remote relay. This is the MRATE setting on the
remote relay.
Several Relay Word bits are useful for monitoring system status. Add RTCCFGp
and RTCDLYp to the SER.
The RTCCFGp Relay Word bit is asserted after the two relays have communi-
cated configuration data successfully. RTCCFGp deassertion indicates that the
system has changed, perhaps because of a setting change in one of the relays.
If the RTCCFGp Relay Word bit indicates a new configuration, you can issue the
RTC command to ensure that the data being received have not changed. The
RTC command displays a description of the synchrophasor data being received.
Use this command to ensure that the remote value that you chose for the
SEL
OGIC equation is the correct value to compare with the local synchrophasor
value.
The RTCDLYA bit asserts when synchrophasor data have not been received on
Channel A within the window you set with the local MRTCDLY setting (100 ms
in this example). If the RTCDLYA asserts, consider three options. First, the
MRTCDLY setting can be increased. However, the MRTCDLY setting is your
way of guaranteeing operation within a certain time. Increasing MRTCDLY
allows for communications channels with longer transmission delay, but at the
cost of increasing the maximum time of operation. A second option is to improve
the communications channel so that it operates within the required MRTCDLY
setting time. A final option is available if the assertion of MRTCDLY results
from a temporary communications channel disruption. In this case, putting RTC-
DLYA in the SER provides warning.
The COM RTC command also provides information for monitoring system sta-
tus. Figure 18.11 shows a COM RTC command response. Use the maximum
packet delay field to monitor the communications channel delay. This informa-
tion can help you choose an appropriate value for the MRTCDLY setting.
RTCSEQp
a
This bit is asserted when the processed received message on Channel p is the
expected next-in-sequence. It is deasserted if it is not. The deassertion
implies that one or more packets of information were lost. Use this bit to con-
dition usage of Channel p data in applications where sequential data are
required.
RTCCFGp
a
Indicates Channel p is successfully configured.
a
p
= A or B.
Table 18.25 Remote Synchrophasor Data Bits
Name Description
RTCpD[16]
a
a
p
= A or B.
First sixteen digitals received in synchrophasor message on Channel p.
Only valid when RTCROKp is asserted.
Table 18.24 Synchrophasor Client Status Bits
Name Description
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