GE Power Quality Meter Series, Инструкция по эксплуатации

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GE Power Management PQM Power Quality Meter 2-17
2 INSTALLATION 2.2 ELECTRICAL
2
2.2.7 ANALOG OUTPUTS (OPTIONAL)
The PQM has four current outputs when the transducer option is installed (T20 = 4 to 20 mA, T1 = 0 to 1 mA in
the order code). These outputs can be multiplexed to produce 8 analog transducers. This output is a current
source suitable for connection to a remote meter, chart recorder, programmable controller, or computer load.
Use the 4 to 20 mA option with a programmable controller that has a 2 to 40 mA current input. If only a voltage
input is available, use a scaling resistor at the PLC terminals to scale the current to the equivalent voltage. For
example, install a 500
Ω
resistor across the terminals of a 0 to 10 V input to make the 4 to 20 mA output corre-
spond to 2 to 10V (R = V / I = 10 V / 0.02 A = 500
Ω
). Current levels are not affected by the total lead and load
resistance which must not exceed 600
Ω
for the 4 to 20 mA range and 2400
Ω
for the 0 to 1 mA range. For
readings greater than full scale the output will saturate at 22 mA (4 to 20 mA) or 1.1 mA (0 to 1 mA). These
analog outputs are isolated and since all output terminals are floating, the connection of the analog output to a
process input will not introduce a ground loop. Part of the system should be grounded for safety, typically at the
programmable controller. For floating loads (such as a meter), ground Terminal 24 externally.
The outputs for these transducers can be selected from any of the measured parameters in the PQM. The
choice of output is selected in the
S2 SYSTEM SETUP \ ANALOG OUTPUT 1-4 setpoints group. See Section 4.3.2:
ANALOG OUTPUTS on page 4–21 for a list of available parameters. Each analog output can be assigned two
parameters: a main parameter and an alternate parameter. Under normal operating conditions, the main
parameter will appear at the output terminals. To select the alternate parameter, one of the switch inputs must
be assigned to SELECT ANALOG OUT and the switch input must be closed (assuming normally closed activa-
tion). By opening and closing the switch input, two analog output parameters can be multiplexed on one output.
This effectively achieves 8 analog outputs for the PQM.
Figure 2–13: ANALOG OUTPUT
As shown in wiring diagrams on pages 2–6 to 2–11, these outputs are at Terminals 25 to 28 and share Terminal
24 as their common. Shielded cable should be used, with only one end of the shield grounded, to minimize
noise effects.
Signals and power supply circuitry are internally isolated, allowing connection to devices (PLCs, computers,
etc.) at ground potentials different from the PQM. Each terminal, however, is clamped to ±36 V to ground.
2.2.8 ANALOG INPUT (OPTIONAL)
Terminals 22(–) and 23(+) are provided for a current signal input. This current signal can be used to monitor
any external quantity, such as transformer winding temperature, battery voltage, station service voltage, trans-
former tap position, etc. Any transducer output ranges within the range of 0 to 20 mA can be connected to the
analog input terminals of the PQM. See Section 4.3.3: ANALOG INPUT on page 4–25 for details on program-
ming the analog input.