Rockwell Automation 1426 PowerMonitor 5000 Unit - Manual (Page 386)

386 Rockwell Automation Publication 1426-UM001F-EN-P - November 2013
Glossary
Real Power The component of apparent power that represents real work in an alternating
current circuit. It is expressed in watts and is equal to the apparent power times
the power factor.
Resistance The property of a substance that 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 produces
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.
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.
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.
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, for example, Peak
VA demand, is sometimes used for billing.
Voltage (V) The force that 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.
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, for example, Peak
demand is commonly used for billing.