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PowerLogicTM Series 800 Power Meter	63230-500-225A2
Glossary	3/2011

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—seepower 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.

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