4.3
Date Code 20090730 Instruction Manual SEL-734 Meter
Metering
Instantaneous Metering
Figure 4.2 SEL-734 Power Flow Notations
Four-Quadrant
Meter Word Bits
In addition to displaying analog VAR quantities in all four quadrants, Meter
Word bits describing the instantaneous VAR quadrants are available (see
Meter Word Bits (Used in SEL
OGIC Control Equations) on page 9.3). These
bits are useful when monitoring unsigned VARs.
Instantaneous Metering
Use instantaneous metering to monitor power system parameters in real time.
The SEL-734 provides these readings:
➤ Fundamental phase voltages and currents
➤ RMS phase voltages and currents
➤ Phase-to-phase voltages
➤ Sequence voltages and currents
➤ Real, 4-quadrant reactive, and apparent power
➤ Distortion power
You can use the MET command (see MET Commands on page 10.18) to
display these instantaneous values or you can view them from the front panel.
SEL-734
Source
(Electric Utility)
Load
(Industrial Plant)
OUT (Received)
IN (Delivered)
Table 4.1 Metering Quantity Definitions (Sheet 1 of 2)
Ter m Definition
Real Power (P) Power that produces actual work, measured in watts; the
portion of apparent power that is real, not imaginary.
Real Power Average (P
AV E
) Real power (P) averaged over a one-second interval.
Real Power
Three Phase (P3P)
Three-phase real power measured in watts.
Reactive Power (Q) Reactive power measured in volt-amps reactive (VAR). The
product of the voltage and current multiplied by the sine of
the angle between the two.
Reactive Power
Average (Q
AV E
)
Reactive power (Q) average over a one-second interval.
Q
AV E
is forced to zero when the apparent power (S) is less
than or equal to real power (P) • 1.001.
Courtesy of NationalSwitchgear.com
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