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GE Multilin 489 Generator Management Relay 2-11
2 INSTALLATION 2.2 ELECTRICAL
2
2.2.5 VOLTAGE INPUTS
The 489 has four voltage transformer inputs, three for generator terminal voltage and one for neutral voltage. There are no
internal fuses or ground connections on the voltage inputs. The maximum VT ratio is 240.00:1. The two possible VT con-
nections for generator terminal voltage measurement are open delta or wye (see Figure 2–9: Typical Wiring Diagram on
page 2–7). The voltage channels are connected in wye internally, which means that the jumper shown on the delta-source
connection of the Typical Wiring Diagram, between the phase B input and the 489 neutral terminal, must be installed for
open delta VTs.
Polarity of the generator terminal VTs is critical for correct power measurement and voltage phase reversal
operation.
2.2.6 DIGITAL INPUTS
There are 9 digital inputs that are designed for dry contact connections only. Two of the digital inputs, Access and
Breaker Status have their own common terminal, the balance of the digital inputs share one common terminal (see
Figure 2–9: Typical Wiring Diagram on page 2–7).
In addition, the +24 V DC switch supply is brought out for control power of an inductive or capacitive proximity probe. The
NPN transistor output could be taken to one of the assignable digital inputs configured as a counter or tachometer. Refer to
the Specifications section of this manual for maximum current draw from the +24 V DC switch supply.
DO NOT INJECT VOLTAGES TO DIGITAL INPUTS. DRY CONTACT CONNECTIONS ONLY.
2.2.7 ANALOG INPUTS
Terminals are provided on the 489 for the input of four 0 to 1 mA, 0 to 20 mA, or 4 to 20 mA current signals (field program-
mable). This current signal can be used to monitor any external quantity such as: vibration, pressure, field current, etc. The
four inputs share one common return. Polarity of these inputs must be observed for proper operation The analog input cir-
cuitry is isolated as a group with the Analog Output circuitry and the RTD circuitry. Only one ground reference should be
used for the three circuits. Transorbs limit this isolation to ±36 V with respect to the 489 safety ground.
In addition, the +24 V DC analog input supply is brought out for control power of loop powered transducers. Refer to the
Specifications section of this manual for maximum current draw from this supply.
Figure 2–14: LOOP POWERED TRANSDUCER CONNECTION
CAUTION
CAUTION
CAUTION