7.2
SEL-400 Series Relays Instruction Manual Date Code 20171006
Metering
Instantaneous Metering
Instantaneous Metering
Use instantaneous metering to monitor power system parameters in real time.
The relay typically provides these fundamental frequency readings:
➤ Fundamental frequency phase voltages and currents
➤ Phase-to-phase voltages
➤ Sequence voltages and currents
➤ Fundamental real, reactive, and apparent power
➤ Displacement power factor
NOTE: After startup, automatic
restart, or a warm start, including
settings change and group switch, in
the beginning period of 20 cycles, the
10-cycle average values are initialized
with the latest calculated 1-cycle
average values.
You can also typically monitor these real-time rms quantities (with harmonics
included):
➤ RMS phase voltages and currents
➤ Real and apparent rms power
➤ True power factor
Power
The instantaneous power measurements are derived from 10-cycle averages that
the relay reports by using the generator condition of the positive power flow con-
vention; for example, real and reactive power flowing out (export) is positive, and
real and reactive power flowing in (import) is negative (see Figure 7.1).
NOTE: The SEL-487B does not
include power and power factor in its
metering reports.
For power factor, LAG and LEAD refer to whether the current lags or leads the
applied voltage. The reactive power Q is positive when the voltage angle is
greater than the current angle (V > I), which is the case for inductive loads
where the current lags the applied voltage. Conversely, Q is negative when the
voltage angle is less than the current angle V < I); this is when the current
leads the voltage, as in the case of capacitive loads.
MET M Display line maximum/minimum metering information
MET RM Reset line maximum/minimum metering information
MET D Display demand line metering information
MET RD Reset demand line metering information
MET RP Reset peak demand line metering information
MET E Display energy line metering information
MET RE Reset energy line metering information
MET BAT Display dc battery monitor information
MET RBM Reset battery monitor min/max measurements
MET PM Display phasor measurement (synchrophasor) metering information
MET RTD Display SEL-2600 temperature quantities
MET PMV Display protection math variable values
MET AMV Display automation math variable values
MET ANA Display remote analogs received from M
IRRORED BITS
Table 7.1 MET Command (Sheet 2 of 2)
Name Description
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