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PowerLogic
TM
Series 800 Power Meter 63230-500-225A2
Glossary 3/2011
106
nominal—typical or average.
parity—refers to binary numbers sent
over the communications link. An extra
bit is added so that the number of ones
in the binary number is either even or
odd, depending on your configuration.
Used to detect errors in the
transmission of data.
partial interval demand—calculation
of energy thus far in a present interval.
Equal to energy accumulated thus far in
the interval divided by the length of the
complete interval.
phase currents (rms)—measurement
in amperes of the rms current for each
of the three phases of the circuit. See
also maximum value.
phase rotation—phase rotations refers
to the order in which the instantaneous
values of the voltages or currents of the
system reach their maximum positive
values. Two phase rotations are
possible: A-B-C or A-C-B.
potential transformer (PT)—also
known as a voltage transformer
power factor (PF)—true power factor is
the ratio of real power to apparent
power using the complete harmonic
content of real and apparent power.
Calculated by dividing watts by volt
amperes. Power factor is the difference
between the total power your utility
delivers and the portion of total power
that does useful work. Power factor is
the degree to which voltage and current
to a load are out of phase.
real power—calculation of the real
power (3-phase total and per-phase
real power calculated) to obtain
kilowatts.
rms—root mean square. Power meters
are true rms sensing devices.
rolling block—a selected interval and
sub-interval that the power meter uses
for demand calculation. The sub-
interval must divide evenly into the
interval. Demand is updated at each
sub-interval, and the power meter
displays the demand value for the last
completed interval.
sag/swell—fluctuation (decreasing or
increasing) in voltage or current in the
electrical system being monitored. See
also, voltage sag and voltage swell.
scale factor—multipliers that the power
meter uses to make values fit into the
register where information is stored.
safety extra low voltage (SELV)
circuit—a SELV circuit is expected to
always be below a hazardous voltage
level.
short integer—a signed 16-bit integer
(see Register List on page 79).
sliding block—an interval selected
from 1 to 60 minutes (in 1-minute
increments). If the interval is between 1
and 15 minutes, the demand calculation
updates every 15 seconds. If the
interval is between 16 and 60 minutes,
the demand calculation updates every
60 seconds. The power meter displays
the demand value for the last
completed interval.
system type—a unique code assigned
to each type of system wiring
configuration of the power meter.
thermal demand—demand calculation
based on thermal response.
Total Harmonic Distortion (THD or
thd)—indicates the degree to which the
volt-age or current signal is distorted in
a circuit.
total power factor—see power factor.
true power factor—see power factor.
unsigned integer—an unsigned 16-bit
integer (see Register List Access on
page 79).
unsigned long integer—an unsigned
32-bit value returned by a register
(Register List Access on page 79). The
upper 16-bits are in the lowest-
numbered register pair. For example, in
the register pair 4010 and 4011, 4010
contains the upper 16-bits while 4011
contains the lower 16-bits.
VAR—volt ampere reactive.
voltage sag—a brief decrease in
effective voltage for up to one minute in
duration.
voltage swell—increase in effective
voltage for up to one minute in duration.