Allen-Bradley Powermonitor 3000 User Manual page 346

Glossary 22
Publication 1404-UM001D-EN-E - October 2004
ratchet clause
A rate schedule clause which states that billing demand may be based
on current month peak demand or on historical peak demand,
depending on relative magnitude. Usually the historical period is the
past eleven months, although it can be for the life of the contract.
Billing demand is either the current month peak demand or some
percentage (75 percent is typical) of the highest historical peak
demand, depending on which is largest. It is designed to compensate
the electric utility for maintaining equipment not fully utilized.
reactance
The opposition to the flow of alternating current. Capacitive reactance
is the opposition offered by capacitors and inductive reactance is the
opposition offered by an inductive load. Both reactances are
measured in ohms.
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 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.
RTU
Remote Terminal Unit, one of two possible transmission formats
supported by Modbus. Powermonitor 3000 only supports RTU slave
function.