11.7
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Time and Date Management
Time Quality Indications
If TSOK is not asserted, but TIRIG is asserted, the relay is in regular IRIG time-
keeping mode. Following is a list of possible reasons for not entering HIRIG mode:
➤ The IRIG-B clock does not use the IEEE C37.118 control bit
assignments, or the IRIG-B signal is not of sufficient accuracy.
➤ The termination resistor, required by some IRIG clocks, is not installed.
➤ The time-source clock is reporting that its time error is greater than 1 s.
If neither TSOK nor TIRIG is asserted, the relay is not in an IRIG time-source
mode. Following is a list of possible reasons for not entering IRIG mode:
➤ The IRIG-B clock signal is not of sufficient accuracy or is
improperly configured.
➤ The termination resistor, required by some IRIG clocks, is not installed.
NOTE: At startup, TPTP can assert
as fast as 1.5 seconds after PTP_TIM
asserts.
TBNC asserts when BNC IRIG is used to update the relay master time. Likewise,
TSER asserts when serial IRIG is selected and TPTP asserts when PTP is the
active source updating the relay master time. At any given time, only one of these
three bits can equal logical 1.
Global Time Source vs Local Time Source
An SEL-400 series relay indicates that it is synchronized with either a Global or
local time source according to the logic as shown in Figure 11.3. When
CUR_SRC is IRIG or PTP and TSOK is asserted, the relay determines the status
of TGLOBAL or TLOCAL following the logic diagram in Figure 11.3.
TGLOBAL asserts when the relay is synchronized to high-accuracy IRIG-B
(accuracy 1 us and IRIGC = C37.118) or PTP (accuracy 1 us,
master_clock_class = 6). A holdover timer keeps TGLOBAL asserted for five
seconds if the relay loses its global time source after being synchronized. TLO-
CAL asserts when the relay is synchronized to high-accuracy IRIG-B (accuracy
1 us and IRIGC = None) or PTP (accuracy 1 us) and TGLOBAL is not
asserted.
Figure 11.3 TLOCAL and TGLOBAL Logic
5 S
CUR_SRC = IRIG
CUR_SRC = PTP
TSOK
TSOK
IRIGC = None
IRIGC = C37.118
master_clock_class ≠ 6
master_clock_class = 6
5 S
Holdover Timer
Holdover Timer
To TLOCAL
To TGLOBAL
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