GPS Syncronization Unit CMGPS
32
5.3 Using CMGPS in Conjunction with CMIRIG-B
Via the CMIRIG-B interface unit you can connect devices to CMC test sets that
either transmit or receive the IRIG-B time reference signal (DC level shift
protocol B00x). That way, two or more CMC test sets are synchronized.
Furthermore, an optional CMGPS synchronization unit can be integrated into
the test setup to serve as source of the synchronization moment or 1PPS
signal, respectively. The CMC test set decodes (when receiving) or encodes
(when transmitting) the IRIG-B protocol. The IRIG-B protocol extensions
required by standard IEEE C37.118 are supported as well.
The most significant functional enhancement of those Test Universe test
modules supporting the IRIG-B time reference is the starting and synchronizing
of CMC test set states (signal output) with high accuracy synchronous to the
IRIG-B
1
time reference or PPS/PPX
2
signal, respectively; for example for PMU
synchrophasor tests.
Figure 5-4:
Typical test setup with
CMIRIG-B
(not true to scale)
Requirements:
•A CMC 256 test set with Ethernet ports (not with PAR-1 option), a
CMC 256plus, CMC 353, CMC 356 or a CMC 850 test set.
• IRIG-B source or receiver with 5 V/TTL level; demodulated; DC level shift
protocol (B00x).
• In conjunction with the CMIRIG-B interface unit, use the 100-240 V
AC
/
18 V
DC
power supply unit to power the CMGPS.
1. IRIG stands for Inter Range Instrumentation Group and represents a serial time code format.
2. PPS: pulses per second. PPX: programmable PPS signal (pulse rate, e.g., 1 pulse per minute or
one pulse per 10 seconds)
Test signals (e.g., 3 x current, 3 x voltage).
IRIG-B/PPS source, e.g. GPS receiver with IRIG-B output.
IRIG-B/PPS receiver, e.g. protection relay, PMU.
Optional CMGPS synchronization unit (depends on the application).
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