U.4.69
Date Code 20020501 User’s Guide SEL-421/SEL-421-1 Relay
Basic Relay Operations
Configuring High-Accuracy Timekeeping
Sync Status shows whether the relay internal clock is locked. The PPS Time
Mark Period value and the IRIG Time Mark Period value indicate the
instantaneous period in which the relay measures the time source inputs. The
relay displays the time mark periods showing the present time precision
derived from the applied time source signals. (The FF Time Mark Period is for
a future fiber port time input).
Adaptive Internal Clock Period Adjustment
The Internal Clock Period is the internal relay timekeeping period. The relay
adjusts this master internal clock when you apply PPS mode timekeeping,
adapting the internal relay clock for your installation temperature conditions.
If you lose the PPS timing lock, the relay internal clock operates at this
precisely adapted clock period until PPS mode is restored. Time tags for event
reports during a loss of PPS mode timekeeping remain very accurate. Lower
accuracy time sources do not adaptively adjust the internal relay clock period.
Monitoring
High-Accuracy
Time Source Status
The purpose of the procedure in the following steps is to show one method for
deriving the TIME Q Time Source information from Relay Word bits TPPS
and TIRIG. The TPPS Relay Word bit is at logical 1 when the relay is in PPS
time mode. The relay sets Relay Word bit TUPDH to logical 1, if the updating
source is a high-accuracy time source. For this application example, use a
PSV (Protection SEL
OGIC Variable) to monitor time keeping status.
PSV01 asserts when the relay uses a high-priority source to update the time
value, the synchronizing time source is PPS, and the relay is not
synchronizing to the PPS source. This condition triggers the relay alarm
output (OUT108 for this application example).
This example assumes that you have successfully established communication
with the relay; see Making an EIA-232 Serial Port Connection on page 4.6 for
a step-by-step procedure. In addition, you must be familiar with relay access
levels and passwords. See Changing the Default Passwords: Terminal on
Table 4.9 Date/Time Last Update Sources
Time Input Source
Mode (QQQQQ)
Accuracy Time Source
Front Panel
Editing?
PPS High Time/date from the IRIG-B input
coupled to the 1000 PPS (pulse per
second) pulse signal
No
IRIG High Time/date from the IRIG-B format
time base signal
No
COMM CRD Low Time/date signal from the commu-
nications card
Date and Time
DNP Low Time/date from the DNP commu-
nications port
Date and Time
MIRROR B Low Time/date from the M
IRRORED BIT
port
Date and Time
ASC TIME Low Time from the relay serial ports Date only
ASC DATE Low Date from the relay serial ports Time only
NONV CLK Low Time/date from the nonvolatile
random access memory clock
Date and Time
FP TIME Low Time from the front-panel TIME
entry screen
Date and Time
FP DATE Low Time from the front-panel DATE
entry screen
Date and Time
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