Rockwell Automation 1403-DM_LM_MM Powermonitor II Instruction Sheet - Manual (Page 84)

D-4 Glossary
1403-IN001A-US-P
resistance
The property of a substance which impedes current
flow and results in the dissipation of power in the
form of heat. The unit of resistance is the ohm. One
ohm is the resistance through which a difference of
potential of one volt will produce a current of one
ampere.
revenue meter
A meter used by a utility to generate billing
information. Many types of meters fall in this
category depending on the rate structure.
root mean square (RMS)
The effective value of alternating current or voltage.
The RMS values of voltage and current can be used
for the accurate computation of power in watts. The
RMS value is the same value as if continuous direct
current were applied to a pure resistance.
S
sliding demand interval
A method of calculating average demand by
averaging the average demand over several
successive short time intervals, advancing one short
time interval each time. Updating average demand at
short time intervals gives the utility a much better
measure of true demand and makes it difficult for the
customer to obscure high short-term loads.
U
unbalanced load
A situation existing in a three phase alternating
current system using more than two current carrying
conductors where the current is not due to uneven
loading of the phases.
V
volt-ampere (VA)
The unit of apparent power. It equals volts times
amperes regardless of power factor.
volt-ampere demand
Where peak average demand is measured in volt-
amperes rather than watts. The average VA during a
predefined interval. The highest average, i.e. Peak
VA demand, is sometimes used for billing.
voltage (V)
The force which causes current to flow through a
conductor. One volt equals the force required to
produce a current flow of one ampere through a
resistance of one ohm.
W
watt (W)
A measure of real power. The unit of electrical power
required to do work at the rate of one joule per
second. It is the power expended when one ampere of
direct current flows through a resistance of one ohm.
Equal to apparent power VA times the power factor.
watt demand
Power during a predetermined interval. The highest
average, i.e. Peak demand is commonly used for
billing.
watt hour (Whr)
The number of watts used in one hour. Since the
power usage varies, it is necessary to integrate this
parameter over time. Power flow can be either
forward or reverse.
wattmeter
An instrument for measuring the real power in an
electric circuit. Its scale is usually graduated in watts,
kilowatts or megawatts.
volt ampere reactive hours (VARH)
The number of VARs used in one hour. Since the
value of this parameter varies, it is necessary to
integrate it over time. VARs can be either forward or
reverse.