Irig-B; Rs485 Ports - GE Multilin 489 Instruction Manual

CHAPTER 3: INSTALLATION

3.2.11 IRIG-B

3.2.12 RS485 Ports

489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
voltage from 30 to 250 V DC) through the breaker trip coil. The supervision circuits
respond to a loss of this trickle current as a failure condition. Circuit breakers equipped
with standard control circuits have a breaker auxiliary contact permitting the trip coil
to be energized only when the breaker is closed. When these contacts are open, as
detected by the Breaker Status digital input, trip coil supervision circuit is
automatically disabled. This logic provides that the trip circuit is monitored only when
the breaker is closed.
• 2 AUXILIARY, 3 AUXILIARY, 4 AUXILIARY: The auxiliary relays may be programmed for
numerous functions such as, trip echo, alarm echo, trip backup, alarm or trip
differentiation, control circuitry, etc. They should be wired as configuration warrants.
• 5 ALARM: The alarm relay should connect to the appropriate annunciator or
monitoring device.
• 6 SERVICE: The service relay will operate if any of the 489 diagnostics detect an
internal failure or on loss of control power. This output may be monitored with an
annunciator, PLC or DCS.
The service relay NC contact may also be wired in parallel with the trip relay on a
breaker application. This will provide failsafe operation of the generator; that is, the
generator will be tripped offline in the event that the 489 is not protecting it. Simple
annunciation of such a failure will allow the operator or the operation computer to
either continue, or do a sequenced shutdown.
Relay contacts must be considered unsafe to touch when the system is energized! If
the customer requires the relay contacts for low voltage accessible applications, it is
their responsibility to ensure proper insulation levels.
IRIG-B is a standard time-code format that allows stamping of events to be synchronized
among connected devices within 1 millisecond. The IRIG-B time codes are serial, width-
modulated formats which are either DC level shifted or amplitude modulated (AM). Third
party equipment is available for generating the IRIG-B signal. This equipment may use a
GPS satellite system to obtain the time reference enabling devices at different geographic
locations to be synchronized.
Terminals E12 and F12 on the 489 unit are provided for the connection of an IRIG-B signal.
Two independent two-wire RS485 ports are provided. Up to 32 489 relays can be daisy-
chained together on a communication channel without exceeding the driver capability. For
larger systems, additional serial channels must be added. It is also possible to use
commercially available repeaters to increase the number of relays on a single channel to
more than 32. A suitable cable should have a characteristic impedance of 120 Ω (e.g.
Belden #9841) and total wire length should not exceed 4000 feet (approximately 1200
metres). Commercially available repeaters will allow for transmission distances greater
than 4000 ft.
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