10
MULTISYNC 100 GPS CLOCK – INSTRUCTION MANUAL
THE IRIG-B TIME CODE STANDARD
CHAPTER 2: THEORY OF OPERATION
is normally 5V for on, and 0V for off. Newer IEDs typically use DCLS due to accuracy.
However, the distance to IEDs is limited to around 100m. DCLS typically uses TTL outputs
over shielded, twisted pair cable and BNC connectors.
IEEE-1344 Extensions
The original IRIG Standard did not provide year information, or BCDYEAR, in the time code:
only time and day from the start of the year. Lack of year data was a limitation for some
applications, especially in regards to synchrophasors. The IEEE 1344-1995 Standard for
Synchrophasors for Power Systems includes definitions to include year data in the IRIG-B
time code. The IEEE 1344 extensions, as they're commonly known, add calendar year, leap
second, daylight savings time, local time offset, and time quality to the IRIG-B signal.
Individual devices may or may not support the IEEE 1344 extensions.
The IRIG-B Standard was revised in 2004 to include year data. The 200-04 Standard allows
IRIG-B to publish BCDYEAR, as described. The IEEE 1344 Standard has been replaced by
C37.118-2005 IEEE Standard for Synchrophasors for Power Systems, although the term
"IEEE 1344 extensions" is still in common use. The term "C37.118 extensions" may be used
instead.
Defining IRIG-B Time Codes
The IRIG Standard further defines the Time Code Designation to completely describe the
published time code signal.
Common time code formats are:
•
B00x for DC Level Shift
•
B12x for amplitude modulated
Table 2–1: IRIG signal identification numbers (3 digits)
Format
A
|
|
|
IRIG-A Format
B
|
|
|
IRIG-B Format
D
|
|
|
IRIG-D Format
E
|
|
|
IRIG-E Format
G
|
|
|
IRIG-G Format
H
|
|
|
IRIG-H Format
1st Digit - Modulation
0
|
|
Unmodulated - DC Level Shift, pulse-width coded
1
|
|
Amplitude modulated, sine wave carrier
2
|
|
Manchester modified
2nd Digit - Carrier Frequency /
Resolution
0
|
No carrier (DCLS)
1
|
100 Hz / 10 ms resolution
2
|
1 kHz / 1 ms resolution
3
|
10 kHz / 100
μ
s
resolution
4
|
100 kHz / 10
μ
s
resolution
3rd Digit - Coded Expressions
0
BCD
TOY
, CF, SBS
1
BCD
TOY
, CF
2
BCD
TOY
3
BCD
TOY
, SBS
4
BCD
TOY
, BCD
YEAR
,
CF, SBS
5
BCD
TOY
, BCD
YEAR
,
CF
6
BCD
TOY
, BCD
YEAR
7
BCD
TOY
, BCD
YEAR
, SBS