Irig-B - GE Multilin 350 Series Instruction Manual

CHAPTER 2: INSTALLATION
CAUTION:
CAUTION

2.2.10 IRIG-B

GPS CONNECTION
OPTIONAL
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
Voltage differences between remote ends of the communication link are not uncommon.
For this reason, surge protection devices are internally installed across all RS485 terminals.
Internally, an isolated power supply with an optocoupled data interface is used to prevent
noise coupling.
To ensure that all devices in a daisy-chain are at the same potential, it is imperative
that the common terminals of each RS485 port are tied together and grounded only
once, at the master or at the 350. Failure to do so may result in intermittent or failed
communications.
The source computer/PLC/SCADA system should have similar transient protection devices
installed, either internally or externally. Ground the shield at one point only, as shown in the
figure above, to avoid ground loops.
Correct polarity is also essential. The 350 IEDs must be wired with all the positive (+)
terminals connected together and all the negative (–) terminals connected together. Each
relay must be daisy-chained to the next one. Avoid star or stub connected configurations.
The last device at each end of the daisy-chain should be terminated with a 120 ohm ¼
watt resistor in series with a 1 nF capacitor across the positive and negative terminals.
Observing these guidelines will ensure a reliable communication system immune to
system transients.
IRIG-B is a standard time code format that allows time stamping of events to be
synchronized among connected devices within 1 millisecond. The IRIG time code formats
are serial, width-modulated codes which can be either DC level shift or amplitude
modulated (AM) form. The type of form is auto-detected by the 350 relay. Third party
equipment is available for generating the IRIG-B signal; this equipment may use a GPS
satellite system to obtain the time reference so that devices at different geographic
locations can also be synchronized.
Figure 2-15: IRIG-B connection
GPS SATELLITE SYSTEM
IRIG-B
TIME CODE
GENERATOR
+
(DC SHIFT OR
–
AMPLITUDE MODULATED
SIGNAL CAN BE USED)
RG58/59 COAXIAL CABLE
TO OTHER DEVICES
ELECTRICAL INSTALLATION
GE MULTILIN
350 RELAY
E1 IRIG-B(+)
RECEIVER
D1 IRIG-B(-)
898741.CDR
2–15