4.173
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Global Settings (SET G Command)
IRIGC
IRIGC defines whether IEEE C37.118 control bit extensions are in use. Con-
trol bit extensions contain information such as Leap Second, UTC time, Day-
light Savings Time, and Time Quality. When your satellite-synchronized clock
provides these extensions, your relay adjusts the synchrophasor time-stamp
accordingly.
➤ IRIGC := NONE ignores bit extensions
➤ IRIGC := C37.118 extracts bit extensions and corrects
synchrophasor time accordingly
Coordinated Universal Time (UTC) Offset Setting
The SEL-751 has a Global setting UTC_OFF, settable from –24.00 to 24.00
hours, in 0.25 hour increments. The relay also uses the UTC_OFF setting to
calculate local (relay) time from the UTC source when configured for Simple
Network Time Protocol (SNTP) updating via Ethernet. When a time source
other than SNTP is updating the relay time, the UTC_OFF setting is not con-
sidered because the other time sources are defined as local time.
Automatic Daylight-Saving Time Settings
The SEL-751 can automatically switch to and from daylight-saving time, as
specified by the eight Global settings DST_BEGM through DST_ENDH. The
first four settings control the month, week, day, and time that daylight-saving
time shall commence, while the last four settings control the month, week,
day, and time that daylight-saving time shall cease.
Once configured, the SEL-751 changes to and from daylight-saving time
every year at the specified time. Device Word bit DST asserts when daylight-
saving time is active.
The SEL-751 interprets the week number settings DST_BEGW and
DST_ENDW (1–3, L = Last) as follows:
➤ The first seven days of the month are considered to be in
week 1.
➤ The second seven days of the month are considered to be in
week 2.
➤ The third seven days of the month are considered to be in
week 3.
➤ The last seven days of the month are considered to be in
week “L”.
This method of counting of the weeks allows easy programming of statements
like “the first Sunday”, “the second Saturday”, or “the last Tuesday” of a
month.
As an example, consider the following settings:
DST_BEGM := 3
DST_BEGW := L
DST_BEGD := SUN
DST_BEGH := 2
DST_ENDM := 10
DST_ENDW := 3
DST_ENDD := WED
DST_ENDH := 3
To Next Page
Loading...
